A Direct Numerical Simulation of a Temporally Evolving Liquid-Gas Turbulent Mixing Layer

NASA Astrophysics Data System (ADS)

Vu, Lam Xuan; Chiodi, Robert; Desjardins, Olivier

2017-11-01

Air-blast atomization occurs when streams of co-flowing high speed gas and low speed liquid shear to form drops. Air-blast atomization has numerous industrial applications from combustion engines in jets to sprays used for medical coatings. The high Reynolds number and dynamic pressure ratio of a realistic air-blast atomization case requires large eddy simulation and the use of multiphase sub-grid scale (SGS) models. A direct numerical simulations (DNS) of a temporally evolving mixing layer is presented to be used as a base case from which future multiphase SGS models can be developed. To construct the liquid-gas mixing layer, half of a channel flow from Kim et al. (JFM, 1987) is placed on top of a static liquid layer that then evolves over time. The DNS is performed using a conservative finite volume incompressible multiphase flow solver where phase tracking is handled with a discretely conservative volume of fluid method. This study presents statistics on velocity and volume fraction at different Reynolds and Weber numbers.

The Materials Chemistry of Atomic Oxygen with Applications to Anisotropic Etching of Submicron Structures in Microelectronics and the Surface Chemistry Engineering of Porous Solids

NASA Technical Reports Server (NTRS)

Koontz, Steve L.; Leger, Lubert J.; Wu, Corina; Cross, Jon B.; Jurgensen, Charles W.

1994-01-01

Neutral atomic oxygen is the most abundant component of the ionospheric plasma in the low Earth orbit environment (LEO; 200 to 700 kilometers altitude) and can produce significant degradation of some spacecraft materials. In order to produce a more complete understanding of the materials chemistry of atomic oxygen, the chemistry and physics of O-atom interactions with materials were determined in three radically different environments: (1) The Space Shuttle cargo bay in low Earth orbit (the EOIM-3 space flight experiment), (2) a high-velocity neutral atom beam system (HVAB) at Los Alamos National Laboratory (LANL), and (3) a microwave-plasma flowing-discharge system at JSC. The Space Shuttle and the high velocity atom beam systems produce atom-surface collision energies ranging from 0.1 to 7 eV (hyperthermal atoms) under high-vacuum conditions, while the flowing discharge system produces a 0.065 eV surface collision energy at a total pressure of 2 Torr. Data obtained in the three different O-atom environments referred to above show that the rate of O-atom reaction with polymeric materials is strongly dependent on atom kinetic energy, obeying a reactive scattering law which suggests that atom kinetic energy is directly available for overcoming activation barriers in the reaction. General relationships between polymer reactivity with O atoms and polymer composition and molecular structure have been determined. In addition, vacuum ultraviolet photochemical effects have been shown to dominate the reaction of O atoms with fluorocarbon polymers. Finally, studies of the materials chemistry of O atoms have produced results which may be of interest to technologists outside the aerospace industry. Atomic oxygen 'spin-off' or 'dual use' technologies in the areas of anisotropic etching in microelectronic materials and device processing, as well as surface chemistry engineering of porous solid materials are described.

Structural evolution of nanoscale metallic glasses during high-pressure torsion: A molecular dynamics analysis

NASA Astrophysics Data System (ADS)

Feng, S. D.; Jiao, W.; Jing, Q.; Qi, L.; Pan, S. P.; Li, G.; Ma, M. Z.; Wang, W. H.; Liu, R. P.

2016-11-01

Structural evolution in nanoscale Cu50Zr50 metallic glasses during high-pressure torsion is investigated using molecular dynamics simulations. Results show that the strong cooperation of shear transformations can be realized by high-pressure torsion in nanoscale Cu50Zr50 metallic glasses at room temperature. It is further shown that high-pressure torsion could prompt atoms to possess lower five-fold symmetries and higher potential energies, making them more likely to participate in shear transformations. Meanwhile, a higher torsion period leads to a greater degree of forced cooperative flow. And the pronounced forced cooperative flow at room temperature under high-pressure torsion permits the study of the shear transformation, its activation and characteristics, and its relationship to the deformations behaviors. This research not only provides an important platform for probing the atomic-level understanding of the fundamental mechanisms of high-pressure torsion in metallic glasses, but also leads to higher stresses and homogeneous flow near lower temperatures which is impossible previously.

Magnetic resonance imaging with an optical atomic magnetometer

PubMed Central

Xu, Shoujun; Yashchuk, Valeriy V.; Donaldson, Marcus H.; Rochester, Simon M.; Budker, Dmitry; Pines, Alexander

2006-01-01

We report an approach for the detection of magnetic resonance imaging without superconducting magnets and cryogenics: optical atomic magnetometry. This technique possesses a high sensitivity independent of the strength of the static magnetic field, extending the applicability of magnetic resonance imaging to low magnetic fields and eliminating imaging artifacts associated with high fields. By coupling with a remote-detection scheme, thereby improving the filling factor of the sample, we obtained time-resolved flow images of water with a temporal resolution of 0.1 s and spatial resolutions of 1.6 mm perpendicular to the flow and 4.5 mm along the flow. Potentially inexpensive, compact, and mobile, our technique provides a viable alternative for MRI detection with substantially enhanced sensitivity and time resolution for various situations where traditional MRI is not optimal. PMID:16885210

Initiation with an electron beam of chemical reactions of interest for visible wavelength lasers

NASA Technical Reports Server (NTRS)

Whittier, J. S.; Cool, T. A.

1976-01-01

A description is given of the first results obtained with a new shock tube-electron beam facility designed to provide a versatile means for the systematic search for laser operation among several candidate metal atom-oxidizer systems. According to the current experimental approach, metal atoms are obtained in the vapor phase by the dissociation of metal compounds. A shock tube is employed to provide a short duration flow through an array of 29 supersonic flow-mixing nozzles. A high energy electron accelerator is used for the rapid initiation of chemical reaction in a mixed flow of encapsulated metal and oxidizer.

Slurry burner for mixture of carbonaceous material and water

DOEpatents

Nodd, D.G.; Walker, R.J.

1985-11-05

The present invention is intended to overcome the limitations of the prior art by providing a fuel burner particularly adapted for the combustion of carbonaceous material-water slurries which includes a stationary high pressure tip-emulsion atomizer which directs a uniform fuel into a shearing air flow as the carbonaceous material-water slurry is directed into a combustion chamber, inhibits the collection of unburned fuel upon and within the atomizer, reduces the slurry to a collection of fine particles upon discharge into the combustion chamber, and regulates the operating temperature of the burner as well as primary air flow about the burner and into the combustion chamber for improved combustion efficiency, no atomizer plugging and enhanced flame stability.

An interface capturing scheme for modeling atomization in compressible flows

NASA Astrophysics Data System (ADS)

Garrick, Daniel P.; Hagen, Wyatt A.; Regele, Jonathan D.

2017-09-01

The study of atomization in supersonic flow is critical to ensuring reliable ignition of scramjet combustors under startup conditions. Numerical methods incorporating surface tension effects have largely focused on the incompressible regime as most atomization applications occur at low Mach numbers. Simulating surface tension effects in compressible flow requires robust numerical methods that can handle discontinuities caused by both shocks and material interfaces with high density ratios. In this work, a shock and interface capturing scheme is developed that uses the Harten-Lax-van Leer-Contact (HLLC) Riemann solver while a Tangent of Hyperbola for INterface Capturing (THINC) interface reconstruction scheme retains the fluid immiscibility condition in the volume fraction and phasic densities in the context of the five equation model. The approach includes the effects of compressibility, surface tension, and molecular viscosity. One and two-dimensional benchmark problems demonstrate the desirable interface sharpening and conservation properties of the approach. Simulations of secondary atomization of a cylindrical water column after its interaction with a shockwave show good qualitative agreement with experimentally observed behavior. Three-dimensional examples of primary atomization of a liquid jet in a Mach 2 crossflow demonstrate the robustness of the method.

Elliptic flow from Coulomb interaction and low density elastic scattering

NASA Astrophysics Data System (ADS)

Sun, Yuliang; Li, Qingfeng; Wang, Fuqiang

2018-04-01

In high energy heavy ion collisions and interacting cold atom systems, large elliptic flow anisotropies have been observed. For the large opacity (ρ σ L ˜103 ) of the latter hydrodynamics is a natural consequence, but for the small opacity (ρ σ L ˜1 ) of the former the hydrodynamic description is questionable. To shed light onto the situation, we simulate the expansion of a low density argon ion (or atom) system, initially trapped in an elliptical region, under the Coulomb interaction (or elastic scattering). Significant elliptic anisotropy is found in both cases, and the anisotropy depends on the initial spatial eccentricity and the density of the system. The results may provide insights into the physics of anisotropic flow in high energy heavy ion collisions and its role in the study of quantum chromodynamics.

Investigation of MHD flow structure and fluctuations by potassium lineshape fitting

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bauman, L.E.

1993-12-31

Multiple Potassium D-line emission absorption spectra from a high temperature, coal-fired flow have been fit to a radiative transfer, boundary layer flow model. The results of fitting spectra from the aerodynamic duct of the Department of Energy Coal-Fired Flow Facility provide information about the thickness and shape of the thermal boundary layer and the bulk potassium seed atom density in a simulated magnetohydrodynamic channel flow. Probability distribution functions for the entire set of more than six thousand spectra clearly indicate the typical values and magnitude of fluctuations for the flow: core temperature of 2538 {plus_minus} 20 K, near wall temperaturemore » of 1945 {plus_minus} 135 K, boundary layer width of about 1 cm, and potassium seed atom density of (5.1 {plus_minus} 0.8)x 10{sup 22}/m{sup 3}. Probability distribution functions for selected times during the eight hours of measurements indicate occasional periods of unstable combustion. In addition, broadband particle parameters during the unstable start of the test may be related to differing particle and gas temperatures. The results clearly demonstrate the ability of lineshape fitting to provide valuable data for diagnosing the high speed turbulent flow.« less

Flow velocity measurements with stimulated Rayleigh-Brillouin-gain spectroscopy

NASA Technical Reports Server (NTRS)

Herring, G. C.; Moosmueller, H.; Lee, S. A.; She, C. Y.

1983-01-01

Using stimulated Rayleigh-Brillouin-gain spectroscopy, velocity measurements in an atmospheric-pressure subsonic nitrogen flow with 10 percent uncertainty have been conducted. It is shown that the accuracy of the velocity measurements increases with gas pressure, making this spectroscopic technique ideal for measuring velocity and other parameters of high-pressure (greater than 1-atm) atomic or molecular flows.

Thermal transpiration: A molecular dynamics study

NASA Astrophysics Data System (ADS)

T, Joe Francis; Sathian, Sarith P.

2014-12-01

Thermal transpiration is a phenomenon where fluid molecules move from the cold end towards the hot end of a channel under the influence of longitudinal temperature gradient alone. Although the phenomenon of thermal transpiration is observed at rarefied gas conditions in macro systems, the phenomenon can occur at atmospheric pressure if the characteristic dimensions of the channel is less than 100 nm. The flow through these nanosized channels is characterized by the free molecular flow regimes and continuum theory is inadequate to describe the flow. Thus a non-continuum method like molecular dynamics (MD) is necessary to study such phenomenon. In the present work, MD simulations were carried out to investigate the occurance of thermal transpiration in copper and platinum nanochannels at atmospheric pressure conditions. The mean pressure of argon gas confined inside the nano channels was maintained around 1 bar. The channel height is maintained at 2nm. The argon atoms interact with each other and with the wall atoms through the Lennard-Jones potential. The wall atoms are modelled using an EAM potential. Further, separate simulations were carried out where a Harmonic potential is used for the atom-atom interaction in the platinum channel. A thermally insulating wall was introduced between the low and high temperature regions and those wall atoms interact with fluid atoms through a repulsive potential. A reduced cut off radius were used to achieve this. Thermal creep is induced by applying a temperature gradient along the channel wall. It was found that flow developed in the direction of the increasing temperature gradient of the wall. An increase in the volumetric flux was observed as the length of the cold and the hot regions of the wall were increased. The effect of temperature gradient and the wall-fluid interaction strength on the flow parameters have been studied to understand the phenomenon better.

Review of Fluorescence-Based Velocimetry Techniques to Study High-Speed Compressible Flows

NASA Technical Reports Server (NTRS)

Bathel, Brett F.; Johansen, Criag; Inman, Jennifer A.; Jones, Stephen B.; Danehy, Paul M.

2013-01-01

This paper reviews five laser-induced fluorescence-based velocimetry techniques that have been used to study high-speed compressible flows at NASA Langley Research Center. The techniques discussed in this paper include nitric oxide (NO) molecular tagging velocimetry (MTV), nitrogen dioxide photodissociation (NO2-to-NO) MTV, and NO and atomic oxygen (O-atom) Doppler-shift-based velocimetry. Measurements of both single-component and two-component velocity have been performed using these techniques. This paper details the specific application and experiment for which each technique has been used, the facility in which the experiment was performed, the experimental setup, sample results, and a discussion of the lessons learned from each experiment.

Slurry burner for mixture of carbonaceous material and water

DOEpatents

Nodd, Dennis G.; Walker, Richard J.

1987-01-01

A carbonaceous material-water slurry burner includes a high pressure tip-emulsion atomizer for directing a carbonaceous material-water slurry into a combustion chamber for burning therein without requiring a support fuel or oxygen enrichment of the combustion air. Introduction of the carbonaceous material-water slurry under pressure forces it through a fixed atomizer wherein the slurry is reduced to small droplets by mixing with an atomizing air flow and directed into the combustion chamber. The atomizer includes a swirler located immediately adjacent to where the fuel slurry is introduced into the combustion chamber and which has a single center channel through which the carbonaceous material-water slurry flows into a plurality of diverging channels continuous with the center channel from which the slurry exits the swirler immediately adjacent to an aperture in the combustion chamber. The swirler includes a plurality of slots around its periphery extending the length thereof through which the atomizing air flows and by means of which the atomizing air is deflected so as to exert a maximum shear force upon the carbonaceous material-water slurry as it exits the swirler and enters the combustion chamber. A circulating coolant system or boiler feed water is provided around the periphery of the burner along the length thereof to regulate burner operating temperature, eliminate atomizer plugging, and inhibit the generation of sparklers, thus increasing combustion efficiency. A secondary air source directs heated air into the combustion chamber to promote recirculation of the hot combustion gases within the combustion chamber.

Coaxial atomization of a round liquid jet in a high speed gas stream: A phenomenological study

NASA Astrophysics Data System (ADS)

Mayer, W. O. H.

1994-05-01

Coaxial injectors have proven to be advantageous for the injection, atomization and mixing of propellants in cryogenic H2/O2 rocket engines. Thereby, a round liquid oxygen jet is atomized by a fast, coaxial gaseous hydrogen jet. This article summarizes phenomenological studies of coaxial spray generation under a broad variation of influencing parameters including injector design, inflow, and fluid conditions. The experimental investigations, performed using spark light photography and high speed cinematography in a shadow graph setup as main diagnostic means, illuminate the most important processes leading to atomization. These are identified as turbulence in the liquid jet, surface instability, surface wave growth and droplet detachment. Numerical simulations including free surface flow phenomena are a further diagnostic tool to elucidate some atomization particulars. The results of the study are of general importance in the field of liquid atomization.

Theoretical calculations and experimental verification for the pumping effect caused by the dynamic micro-tapered angle

NASA Astrophysics Data System (ADS)

Cai, Yufei; Zhang, Jianhui; Zhu, Chunling; Huang, Jun; Jiang, Feng

2016-05-01

The atomizer with micro cone apertures has advantages of ultra-fine atomized droplets, low power consumption and low temperature rise. The current research of this kind of atomizer mainly focuses on the performance and its application while there is less research of the principle of the atomization. Under the analysis of the dispenser and its micro-tapered aperture's deformation, the volume changes during the deformation and vibration of the micro-tapered aperture on the dispenser are calculated by coordinate transformation. Based on the characters of the flow resistance in a cone aperture, it is found that the dynamic cone angle results from periodical changes of the volume of the micro-tapered aperture of the atomizer and this change drives one-way flows. Besides, an experimental atomization platform is established to measure the atomization rates with different resonance frequencies of the cone aperture atomizer. The atomization performances of cone aperture and straight aperture atomizers are also measured. The experimental results show the existence of the pumping effect of the dynamic tapered angle. This effect is usually observed in industries that require low dispersion and micro- and nanoscale grain sizes, such as during production of high-pressure nozzles and inhalation therapy. Strategies to minimize the pumping effect of the dynamic cone angle or improve future designs are important concerns. This research proposes that dynamic micro-tapered angle is an important cause of atomization of the atomizer with micro cone apertures.

Coaxial airblast atomizers

NASA Technical Reports Server (NTRS)

Hardalupas, Y.; Whitelaw, J. H.

1993-01-01

An experimental investigation was performed to quantify the characteristics of the sprays of coaxial injectors with particular emphasis on those aspects relevant to the performance of rocket engines. Measurements for coaxial air blast atomizers were obtained using air to represent the gaseous stream and water to represent the liquid stream. A wide range of flow conditions were examined for sprays with and without swirl for gaseous streams. The parameters varied include Weber number, gas flow rate, liquid flow rate, swirl, and nozzle geometry. Measurements were made with a phase Doppler velocimeter. Major conclusions of the study focused upon droplet size as a function of Weber number, effect of gas flow rate on atomization and spray spread, effect of nozzle geometry on atomization and spread, effect of swirl on atomization, spread, jet recirculation and breakup, and secondary atomization.

High effective heterogeneous plasma vortex reactor for production of heat energy and hydrogen

NASA Astrophysics Data System (ADS)

Belov, N. K.; Zavershinskii, I. P.; Klimov, A. I.; Molevich, N. E.; Porfiriev, D. P.; Tolkunov, B. N.

2018-03-01

This work is a continuation of our previous studies [1-10] of physical parameters and properties of a long-lived heterogeneous plasmoid (plasma formation with erosive nanoclusters) created by combined discharge in a high-speed swirl flow. Here interaction of metal nanoclusters with hydrogen atoms is studied in a plasma vortex reactor (PVR) with argon-water steam mixture. Metal nanoclusters were created by nickel cathode’s erosion at combined discharge on. Dissociated hydrogen atoms and ions were obtained in water steam by electric discharge. These hydrogen atoms and ions interacted with metal nanoclusters, which resulted in the creation of a stable plasmoid in a swirl gas flow. This plasmoid has been found to create intensive soft X-ray radiation. Plasma parameters of this plasmoid were measured by optical spectroscopy method. It has been obtained that there is a high non-equilibrium plasmoid: Te > TV >> TR. The measured coefficient of energy performance of this plasmoid is about COP = 2÷10. This extra power release in plasmoid is supposed to be connected with internal excited electrons. The obtained experimental results have proved our suggestion.

Fuel Injector With Shear Atomizer

NASA Technical Reports Server (NTRS)

Beal, George W.; Mills, Virgil L.; Smith, Durward B., II; Beacom, William F.

1995-01-01

Atomizer for injecting liquid fuel into combustion chamber uses impact and swirl to break incoming stream of fuel into small, more combustible droplets. Slanted holes direct flow of liquid fuel to stepped cylindrical wall. Impact on wall atomizes liquid. Air flowing past vanes entrains droplets of liquid in swirling flow. Fuel injected at pressure lower than customarily needed.

Collisional quenching of atoms and molecules on spacecraft thermal protection surfaces

NASA Technical Reports Server (NTRS)

Marinelli, W. J.; Green, B. D.

1988-01-01

Preliminary results of a research program to determine energy partitioning in spacecraft thermal protection materials due to atom recombination at the gas-surface interface are presented. The primary focus of the research is to understand the catalytic processes which determine heat loading on Shuttle, Aeroassisted OTV, and NASP thermal protection surfaces in nonequilibrium flight regimes. Highly sensitive laser diagnostics based on laser-induced fluorescence and resonantly-enhanced multiphoton ionization spectroscopy are used to detect atoms and metastable molecules. At low temperatures, a discharge flow reactor is employed to measure deactivation/recombination coefficients for O-atoms, N-atoms, and O2. Detection methods are presented for measuring O-atoms, O2 and N2, and results for deactivation of O2 and O-atoms on reaction-cured glass and Ni surfaces. Both atom recombination and metastable product formation are examined. Radio-frequency discharges are used to produce highly dissociated beams of atomic species at energies characteristic of the surface temperature. Auger electron spectroscopy is employed as a diagnostic of surface composition in order to accurately define and control measurement conditions.

Heat Transfer of Confined Impinging Air-water Mist Jet

NASA Astrophysics Data System (ADS)

Chang, Shyy Woei; Su, Lo May

This paper describes the detailed heat transfer distributions of an atomized air-water mist jet impinging orthogonally onto a confined target plate with various water-to-air mass-flow ratios. A transient technique was used to measure the full field heat transfer coefficients of the impinging surface. Results showed that the high momentum mist-jet interacting with the water-film and wall-jet flows created a variety of heat transfer contours on the impinging surface. The trade-off between the competing influences of the different heat transfer mechanisms involving in an impinging mist jet made the nonlinear variation tendency of overall heat transfer against the increase of water-to-air mass-flow ratio and extended the effective cooling region. With separation distances of 10, 8, 6 and 4 jet-diameters, the spatially averaged heat transfer values on the target plate could respectively reach about 2.01, 1.83, 2.43 and 2.12 times of the equivalent air-jet values, which confirmed the applicability of impinging mist-jet for heat transfer enhancement. The optimal choices of water-to-air mass-flow ratio for the atomized mist jet required the considerations of interactive and combined effects of separation distance, air-jet Reynolds number and the water-to-air mass-flow ratio into the atomized nozzle.

Injection Principles from Combustion Studies in a 200-Pound-Thrust Rocket Engine Using Liquid Oxygen and Heptane

NASA Technical Reports Server (NTRS)

Heidmann, M. F.; Auble, C. M.

1955-01-01

The importance of atomizing and mixing liquid oxygen and heptane was studied in a 200-pound-thrust rocket engine. Ten injector elements were used with both steel and transparent chambers. Characteristic velocity was measured over a range of mixture ratios. Combustion gas-flow and luminosity patterns within the chamber were obtained by photographic methods. The results show that, for efficient combustion, the propellants should be both atomized and mixed. Heptane atomization controlled the combustion rate to a much larger extent than oxygen atomization. Induced mixing, however, was required to complete combustion in the smallest volume. For stable, high-efficiency combustion and smooth engine starts, mixing after atomization was most promising.

Transport coefficients and heat fluxes in non-equilibrium high-temperature flows with electronic excitation

NASA Astrophysics Data System (ADS)

Istomin, V. A.; Kustova, E. V.

2017-02-01

The influence of electronic excitation on transport processes in non-equilibrium high-temperature ionized mixture flows is studied. Two five-component mixtures, N 2 / N2 + / N / N + / e - and O 2 / O2 + / O / O + / e - , are considered taking into account the electronic degrees of freedom for atomic species as well as the rotational-vibrational-electronic degrees of freedom for molecular species, both neutral and ionized. Using the modified Chapman-Enskog method, the transport coefficients (thermal conductivity, shear viscosity and bulk viscosity, diffusion and thermal diffusion) are calculated in the temperature range 500-50 000 K. Thermal conductivity and bulk viscosity coefficients are strongly affected by electronic states, especially for neutral atomic species. Shear viscosity, diffusion, and thermal diffusion coefficients are not sensible to electronic excitation if the size of excited states is assumed to be constant. The limits of applicability for the Stokes relation are discussed; at high temperatures, this relation is violated not only for molecular species but also for electronically excited atomic gases. Two test cases of strongly non-equilibrium flows behind plane shock waves corresponding to the spacecraft re-entry (Hermes and Fire II) are simulated numerically. Fluid-dynamic variables and heat fluxes are evaluated in gases with electronic excitation. In inviscid flows without chemical-radiative coupling, the flow-field is weakly affected by electronic states; however, in viscous flows, their influence can be more important, in particular, on the convective heat flux. The contribution of different dissipative processes to the heat transfer is evaluated as well as the effect of reaction rate coefficients. The competition of diffusion and heat conduction processes reduces the overall effect of electronic excitation on the convective heating, especially for the Fire II test case. It is shown that reliable models of chemical reaction rates are of great importance for accurate predictions of the fluid dynamic variables and heat fluxes.

Plasma torch for ignition, flameholding and enhancement of combustion in high speed flows

NASA Technical Reports Server (NTRS)

O'Brien, Walter F. (Inventor); Billingsley, Matthew C. (Inventor); Sanders, Darius D. (Inventor); Schetz, Joseph A. (Inventor)

2009-01-01

Preheating of fuel and injection into a plasma torch plume fro adjacent the plasma torch plume provides for only ignition with reduced delay but improved fuel-air mixing and fuel atomization as well as combustion reaction enhancement. Heat exchange also reduced erosion of the anode of the plasma torch. Fuel mixing atomization, fuel mixture distribution enhancement and combustion reaction enhancement are improved by unsteady plasma torch energization, integral formation of the heat exchanger, fuel injection nozzle and plasma torch anode in a more compact, low-profile arrangement which is not intrusive on a highspeed air flow with which the invention is particularly effective and further enhanced by use of nitrogen as a feedstock material and inclusion of high pressure gases in the fuel to cause effervescence during injection.

Hydrogen fluoride overtone laser: experimental methods of characterization

NASA Astrophysics Data System (ADS)

Wisniewski, Charles F.; Hewett, Kevin B.; Manke, Gerald C., II; Truman, C. Randall; Hager, Gordon D.

2004-09-01

The uncertainty in both the fluorine atom concentration and the gain length has inhibited the development of accurate and device independent models of HF overtone lasers. Furthermore, previous methods of measuring the small signal gain were cumbersome and could not easily generate spatial maps of the gain in the cavity. Experimental techniques have been developed to directly measure the concentration of fluorine atoms, the gain length and the small signal gain in a hydrogen fluoride 5 cm slit nozzle laser. A gas phase titration technique was utilized to measure the fluorine atom concentration using HCl as the titrant. The gain length was measured using a pitot probe to locate the interface of the primary flow with the high Mach number shroud flows. A tunable diode laser was utilized to perform small signal gain measurements on HF overtone (ν=2-->0) transitions.

Nuclear spin polarized H and D by means of spin-exchange optical pumping

NASA Astrophysics Data System (ADS)

Stenger, Jörn; Grosshauser, Carsten; Kilian, Wolfgang; Nagengast, Wolfgang; Ranzenberger, Bernd; Rith, Klaus; Schmidt, Frank

1998-01-01

Optically pumped spin-exchange sources for polarized hydrogen and deuterium atoms have been demonstrated to yield high atomic flow and high electron spin polarization. For maximum nuclear polarization the source has to be operated in spin temperature equilibrium, which has already been demonstrated for hydrogen. In spin temperature equilibrium the nuclear spin polarization PI equals the electron spin polarization PS for hydrogen and is even larger than PS for deuterium. We discuss the general properties of spin temperature equilibrium for a sample of deuterium atoms. One result are the equations PI=4PS/(3+PS2) and Pzz=PSṡPI, where Pzz is the nuclear tensor polarization. Furthermore we demonstrate that the deuterium atoms from our source are in spin temperature equilibrium within the experimental accuracy.

Spray Behavior and Atomization Characteristics of Biodiesel

NASA Astrophysics Data System (ADS)

Choi, Seung-Hun; Oh, Young-Taig

Biodiesel has large amount of oxygen in itself, which make it very efficient in reducing exhaust emission by improving combustion inside an engine. But biodiesel has a low temperature flow problem because it has a high viscosity. In this study, the spray behavior and atomization characteristics were investigated to confirm of some effect for the combination of non-esterification biodiesel and fuel additive WDP and IPA. The process of spray was visualized through the visualization system composed of a halogen lamp and high speed camera, and atomization characteristics were investigated through LDPA. When blending WDP and IPA with biodiesel, atomization and spray characteristics were improved. Through this experimental result, SMD of blended fuel, WDP 25% and biodiesel 75%, was 33.9% reduced at distance 6cm from a nozzle tip under injection pressure 30MPa.

High Average Power Laser Gain Medium With Low Optical Distortion Using A Transverse Flowing Liquid Host

DOEpatents

Comaskey, Brian J.; Ault, Earl R.; Kuklo, Thomas C.

2005-07-05

A high average power, low optical distortion laser gain media is based on a flowing liquid media. A diode laser pumping device with tailored irradiance excites the laser active atom, ion or molecule within the liquid media. A laser active component of the liquid media exhibits energy storage times longer than or comparable to the thermal optical response time of the liquid. A circulation system that provides a closed loop for mixing and circulating the lasing liquid into and out of the optical cavity includes a pump, a diffuser, and a heat exchanger. A liquid flow gain cell includes flow straighteners and flow channel compression.

Characterization of vitamin D3 metabolites using continuous-flow fast atom bombardment tandem mass spectrometry and high-performance liquid chromatography.

PubMed

Yeung, B; Vouros, P; Reddy, G S

1993-08-13

A mass spectrometric method for the detection of vitamin D3 metabolites is described. This method involves the derivatization of the metabolites by cycloaddition with 4-phenyl-1,2,4-triazoline-3,5-dione, followed by their characterization by continuous-flow fast atom bombardment (CF-FAB) tandem mass spectrometry (MS-MS) and high-performance liquid chromatography (HPLC). Using HPLC, this derivatization has been shown to increase the UV detectability of 25-hydroxyvitamin D3 by about 5-fold. The FAB spectra of the adducts are dominated by peaks corresponding to a protonated molecule and a fragment ion derived in part from the loss of the side chain. Multiple reaction monitoring (MRM) of this transition by MS-MS may be utilized for trace level analysis of vitamin D metabolites. Sample introduction by flow injection yields detection limits in the low nanogram to high picogram range, whereas the use of on-line capillary LC has been found to decrease the detection limits to the low picogram level.

Investigation of the cavitating flow in injector nozzles for diesel and biodiesel

NASA Astrophysics Data System (ADS)

Zhong, Wenjun; He, Zhixia; Wang, Qian; Jiang, Zhaochen; Fu, Yanan

2013-07-01

In diesel engines, the cavitating flow in nozzles greatly affects the fuel atomization characteristics and then the subsequent combustion and exhaust emissions. At present the biodiesel is a kind of prospective alternative fuel in diesel engines, the flow characteristics for the biodiesel fuel need to be investigated. In this paper, based on the third-generation synchrotrons of Shanghai Synchrotron Radiation facility (SSRF), a high-precision three-dimension structure of testing nozzle with detailed internal geometry information was obtained using X-ray radiography for a more accurate physical model. A flow visualization experiment system with a transparent scaled-up vertical multi-hole injector nozzle tip was setup. A high resolution and speed CCD camera equipped with a long distance microscope device was used to acquire flow images of diesel and biodiesel fuel, respectively. Then, the characteristics of cavitating flow and their effects on the fuel atomization characteristics were investigated. The experimental results show that the nozzle cavitating flow of both the diesel and biodiesel fuel could be divided into four regimes: turbulent flow, cavitation inception, development of cavitation and hydraulic flip. The critical pressures of both the cavitating flow and hydraulic flip of biodiesel are higher than those of diesel. The spray cone angle increases as the cavitation occurs, but it decreases when the hydraulic flip appears. Finally, it can be concluded that the Reynolds number decreases with the increase of cavitation number, and the discharge coefficient increases with the increase of cavitation number.

Characterization of Arcjet Flows Using Laser-Induced Fluorescence

NASA Technical Reports Server (NTRS)

Bamford, Douglas J.; O'Keefe, Anthony; Babikian, Dikran S.; Stewart, David A.; Strawa, Anthony W.

1995-01-01

A sensor based on laser-induced fluorescence has been installed at the 20-MW NASA Ames Aerodynamic Heating Facility. The sensor has provided new, quantitative, real-time information about properties of the arcjet flow in the highly dissociated, partially ionized, nonequilibrium regime. Number densities of atomic oxygen, flow velocities, heavy particle translational temperatures, and collisional quenching rates have been measured. These results have been used to test and refine computational models of the arcjet flow. The calculated number densities, translational temperatures, and flow velocities are in moderately good agreement with experiment

Surface Catalytic Efficiency of Advanced Carbon Carbon Candidate Thermal Protection Materials for SSTO Vehicles

NASA Technical Reports Server (NTRS)

Stewart, David A.

1996-01-01

The catalytic efficiency (atom recombination coefficients) for advanced ceramic thermal protection systems was calculated using arc-jet data. Coefficients for both oxygen and nitrogen atom recombination on the surfaces of these systems were obtained to temperatures of 1650 K. Optical and chemical stability of the candidate systems to the high energy hypersonic flow was also demonstrated during these tests.

Direct sampling graphite furnace atomic absorption spectrometry - feasibility of Na and K determination in desalted crude oil

NASA Astrophysics Data System (ADS)

Seeger, Tassia S.; Machado, Eduarda Q.; Flores, Erico M. M.; Mello, Paola A.; Duarte, Fabio A.

2018-03-01

In this study, Na and K were determined in desalted crude oil by direct sampling graphite furnace atomic absorption spectrometry (DS-GF AAS), with the use of a Zeeman-effect background correction system with variable magnetic field. The analysis was performed in low and high sensitivity conditions. Sodium determination was performed in two low-sensitivity conditions: 1) main absorption line (589.0 nm), gas stop flow during the atomization step and 3-field dynamic mode (0.6-0.8 T); and 2) secondary absorption line (330.3 nm), gas stop flow during the atomization and 2-field mode (0.8 T). In K determination, some parameters, such as high-sensitivity mode, main absorption line (766.5 nm), gas stop flow during the atomization and 2-field mode (0.8 T), were used. Suitability of chemical modifiers, such as Pd and W-Ir was also evaluated. The heating program for Na and K was based on the pyrolysis and atomization curves. Calibration was performed by aqueous standards. Accuracy was evaluated by the analysis of Green Petroleum Coke (SRM NIST 2718) and Trace Elements in Fuel Oil (SRM NIST 1634c). Recovery tests were also performed and results were compared with those obtained by GF AAS after crude oil digestion by microwave-assisted digestion. The characteristic mass of Na was 17.1 pg and 0.46 ng in conditions 1 and 2, respectively, while the one of K was 1.4 pg. Limits of detection and quantification by DS-GF AAS were 30 and 40 ng g-1 for Na and 3.2 and 4.2 ng g-1 for K, respectively. Sodium and K were determined in three crude oil samples with API density ranging from 20.9 to 28.0. Sodium and K concentration ranged from 1.5 to 73 μg g-1 and from 23 to 522 ng g-1, respectively.

Oxidation kinetics and soot formation

NASA Technical Reports Server (NTRS)

Glassman, I.; Brezinsky, K.

1983-01-01

The research objective is to clarify the role of aromaticity in the soot nucleation process by determining the relative importance of phenyl radical/molecular oxygen and benzene/atomic oxygen reactions in the complex combustion of aromatic compounds. Three sets of chemical flow reactor experiments have been designed to determine the relative importance of the phenyl radical/molecular oxygen and benzene/atomic oxygen reactions. The essential elements of these experiments are 1) the use of cresols and anisole formed during the high temperature oxidation of toluene as chemical reaction indicators; 2) the in situ photolysis of molecular oxygen to provide an oxygen atom perturbation in the reacting aromatic system; and 3) the high temperature pyrolysis of phenol, the cresols and possibly anisole.

Organic matter dynamics and stable isotopes for tracing sources of suspended sediment

NASA Astrophysics Data System (ADS)

Schindler Wildhaber, Y.; Liechti, R.; Alewell, C.

2012-01-01

Suspended sediment (SS) and organic matter in rivers can harm brown trout Salmo trutta by impact on health and fitness of free swimming fish and siltation of the riverbed. The later results in a decrease of hydraulic conductivity and therefore smaller oxygen supply to the salmonid embryos. Additionally, oxygen demand within riverbeds will increase as the pool of organic matter increases. We assessed the temporal and spatial dynamics of sediment, carbon (C) and nitrogen (N) during the brown trout spawning season and used C isotopes as well as the C/N atomic ratio to distinguish autochthonous and allochthonous sources of organic matter in SS loads. The visual basic program IsoSource with 13Ctot and 15N as input isotopes was used to quantify the sources of SS in respect of time and space. Organic matter fractions in the infiltrated and suspended sediment were highest during low flow periods with small sediment loads and lowest during high flow periods with high sediment loads. Peak values in nitrate and dissolved organic C were measured during high flow and precipitation probably due to leaching from pasture and arable land. The organic matter was of allochthonous sources as indicated by the C/N atomic ratio and δ13Corg. Organic matter in SS increased from up- to downstream due to pasture and arable land. The fraction of SS originating from upper watershed riverbed sediment increased at all sites during high flow. Its mean fraction decreased from up- to downstream. During base flow conditions, the major sources of SS are pasture and arable land. The later increased during rainy and warmer periods probably due to snow melting and erosion processes. These modeling results support the measured increased DOC and NO3 concentrations during high flow.

Drop size distribution and air velocity measurements in air assist swirl atomizer sprays

NASA Technical Reports Server (NTRS)

Mao, C.-P.; Oechsle, V.; Chigier, N.

1987-01-01

Detailed measurements of mean drop size (SMD) and size distribution parameters have been made using a Fraunhofer diffraction particle sizing instrument in a series of sprays generated by an air assist swirl atomizer. Thirty-six different combinations of fuel and air mass flow rates were examined with liquid flow rates up to 14 lbm/hr and atomizing air flow rates up to 10 lbm/hr. Linear relationships were found between SMD and liquid to air mass flow rate ratios. SMD increased with distance downstream along the center line and also with radial distance from the axis. Increase in obscuration with distance downstream was due to an increase in number density of particles as the result of deceleration of drops and an increase in the exposed path length of the laser beam. Velocity components of the atomizing air flow field measured by a laser anemometer show swirling jet air flow fields with solid body rotation in the core and free vortex flow in the outer regions.

Experimental investigation of atomization characteristics of swirling spray by ADN gelled propellant

NASA Astrophysics Data System (ADS)

Guan, Hao-Sen; Li, Guo-Xiu; Zhang, Nai-Yuan

2018-03-01

Due to the current global energy shortage and increasingly serious environmental issues, green propellants are attracting more attention. In particular, the ammonium dinitramide (ADN)-based monopropellant thruster is gaining world-wide attention as a green, non-polluting and high specific impulse propellant. Gel propellants combine the advantages of liquid and solid propellants, and are becoming popular in the field of spaceflight. In this paper, a swirling atomization experimental study was carried out using an ADN aqueous gel propellant under different injection pressures. A high-speed camera and a Malvern laser particle size analyzer were used to study the spray process. The flow coefficient, cone angle of swirl atomizing spray, breakup length of spray membrane, and droplet size distribution were analyzed. Furthermore, the effects of different injection pressures on the swirling atomization characteristics were studied.

High fidelity simulation and analysis of liquid jet atomization in a gaseous crossflow at intermediate Weber numbers

NASA Astrophysics Data System (ADS)

Li, Xiaoyi; Soteriou, Marios C.

2016-08-01

Recent advances in numerical methods coupled with the substantial enhancements in computing power and the advent of high performance computing have presented first principle, high fidelity simulation as a viable tool in the prediction and analysis of spray atomization processes. The credibility and potential impact of such simulations, however, has been hampered by the relative absence of detailed validation against experimental evidence. The numerical stability and accuracy challenges arising from the need to simulate the high liquid-gas density ratio across the sharp interfaces encountered in these flows are key reasons for this. In this work we challenge this status quo by presenting a numerical model able to deal with these challenges, employing it in simulations of liquid jet in crossflow atomization and performing extensive validation of its results against a carefully executed experiment with detailed measurements in the atomization region. We then proceed to the detailed analysis of the flow physics. The computational model employs the coupled level set and volume of fluid approach to directly capture the spatiotemporal evolution of the liquid-gas interface and the sharp-interface ghost fluid method to stably handle high liquid-air density ratio. Adaptive mesh refinement and Lagrangian droplet models are shown to be viable options for computational cost reduction. Moreover, high performance computing is leveraged to manage the computational cost. The experiment selected for validation eliminates the impact of inlet liquid and gas turbulence and focuses on the impact of the crossflow aerodynamic forces on the atomization physics. Validation is demonstrated by comparing column surface wavelengths, deformation, breakup locations, column trajectories and droplet sizes, velocities, and mass rates for a range of intermediate Weber numbers. Analysis of the physics is performed in terms of the instability and breakup characteristics and the features of downstream flow recirculation, and vortex shedding. Formation of "Λ" shape windward column waves is observed and explained by the combined upward and lateral surface motion. The existence of Rayleigh-Taylor instability as the primary mechanism for the windward column waves is verified for this case by comparing wavelengths from the simulations to those predicted by linear stability analyses. Physical arguments are employed to postulate that the type of instability manifested may be related to conditions such as the gas Weber number and the inlet turbulence level. The decreased column wavelength with increasing Weber number is found to cause enhanced surface stripping and early depletion of liquid core at higher Weber number. A peculiar "three-streak-two-membrane" liquid structure is identified at the lowest Weber number and explained as the consequence of the symmetric recirculation zones behind the jet column. It is found that the vortical flow downstream of the liquid column resembles a von Karman vortex street and that the coupling between the gas flow and droplet transport is weak for the conditions explored.

High fidelity simulation and analysis of liquid jet atomization in a gaseous crossflow at intermediate Weber numbers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Xiaoyi, E-mail: lixy2@utrc.utc.com; Soteriou, Marios C.

Recent advances in numerical methods coupled with the substantial enhancements in computing power and the advent of high performance computing have presented first principle, high fidelity simulation as a viable tool in the prediction and analysis of spray atomization processes. The credibility and potential impact of such simulations, however, has been hampered by the relative absence of detailed validation against experimental evidence. The numerical stability and accuracy challenges arising from the need to simulate the high liquid-gas density ratio across the sharp interfaces encountered in these flows are key reasons for this. In this work we challenge this status quomore » by presenting a numerical model able to deal with these challenges, employing it in simulations of liquid jet in crossflow atomization and performing extensive validation of its results against a carefully executed experiment with detailed measurements in the atomization region. We then proceed to the detailed analysis of the flow physics. The computational model employs the coupled level set and volume of fluid approach to directly capture the spatiotemporal evolution of the liquid-gas interface and the sharp-interface ghost fluid method to stably handle high liquid-air density ratio. Adaptive mesh refinement and Lagrangian droplet models are shown to be viable options for computational cost reduction. Moreover, high performance computing is leveraged to manage the computational cost. The experiment selected for validation eliminates the impact of inlet liquid and gas turbulence and focuses on the impact of the crossflow aerodynamic forces on the atomization physics. Validation is demonstrated by comparing column surface wavelengths, deformation, breakup locations, column trajectories and droplet sizes, velocities, and mass rates for a range of intermediate Weber numbers. Analysis of the physics is performed in terms of the instability and breakup characteristics and the features of downstream flow recirculation, and vortex shedding. Formation of “Λ” shape windward column waves is observed and explained by the combined upward and lateral surface motion. The existence of Rayleigh-Taylor instability as the primary mechanism for the windward column waves is verified for this case by comparing wavelengths from the simulations to those predicted by linear stability analyses. Physical arguments are employed to postulate that the type of instability manifested may be related to conditions such as the gas Weber number and the inlet turbulence level. The decreased column wavelength with increasing Weber number is found to cause enhanced surface stripping and early depletion of liquid core at higher Weber number. A peculiar “three-streak-two-membrane” liquid structure is identified at the lowest Weber number and explained as the consequence of the symmetric recirculation zones behind the jet column. It is found that the vortical flow downstream of the liquid column resembles a von Karman vortex street and that the coupling between the gas flow and droplet transport is weak for the conditions explored.« less

Highly Segmented Thermal Barrier Coatings Deposited by Suspension Plasma Spray: Effects of Spray Process on Microstructure

NASA Astrophysics Data System (ADS)

Chen, Xiaolong; Honda, Hiroshi; Kuroda, Seiji; Araki, Hiroshi; Murakami, Hideyuki; Watanabe, Makoto; Sakka, Yoshio

2016-12-01

Effects of the ceramic powder size used for suspension as well as several processing parameters in suspension plasma spraying of YSZ were investigated experimentally, aiming to fabricate highly segmented microstructures for thermal barrier coating (TBC) applications. Particle image velocimetry (PIV) was used to observe the atomization process and the velocity distribution of atomized droplets and ceramic particles travelling toward the substrates. The tested parameters included the secondary plasma gas (He versus H2), suspension injection flow rate, and substrate surface roughness. Results indicated that a plasma jet with a relatively higher content of He or H2 as the secondary plasma gas was critical to produce highly segmented YSZ TBCs with a crack density up to 12 cracks/mm. The optimized suspension flow rate played an important role to realize coatings with a reduced porosity level and improved adhesion. An increased powder size and higher operation power level were beneficial for the formation of highly segmented coatings onto substrates with a wider range of surface roughness.

Lipid Neuroprotectants and Traumatic Glaucomatous Neurodegeneration

DTIC Science & Technology

2016-05-01

alter elastic TM, modulus and binding and functional assays with potential protein targets. Endogenous lipids, Aqueous humor, Trabecular meshwork...Intraocular pressure, sphingolipids, primary cell culture, elastic modulus, protein targets. Major goal 1. Test the hypothesis that selected lipids...glaucomatous TM with and without these lipids and atomic force microscope (AFM). Further elastic modulus using high flow and low flow areas of glaucomatous

Evaluation of a locally homogeneous flow model of spray combustion

NASA Technical Reports Server (NTRS)

Mao, C. P.; Szekely, G. A., Jr.; Faeth, G. M.

1980-01-01

A model of spray combustion which employs a second-order turbulence model was developed. The assumption of locally homogeneous flow is made, implying infinitely fast transport rates between the phase. Measurements to test the model were completed for a gaseous n-propane flame and an air atomized n-pentane spray flame, burning in stagnant air at atmospheric pressure. Profiles of mean velocity and temperature, as well as velocity fluctuations and Reynolds stress, were measured in the flames. The predictions for the gas flame were in excellent agreement with the measurements. The predictions for the spray were qualitatively correct, but effects of finite rate interphase transport were evident, resulting in a overstimation of the rate development of the flow. Predictions of spray penetration length at high pressures, including supercritical combustion conditions, were also completed for comparison with earlier measurements. Test conditions involved a pressure atomized n-pentane spray, burning in stagnant air at pressures of 3, 5, and 9 MPa. The comparison between predictions and measurements was fair. This is not a very sensitive test of the model, however, and further high pressure experimental and theoretical results are needed before a satisfactory assessment of the locally homogeneous flow approximation can be made.

A theoretical evaluation of aluminum gel propellant two-phase flow losses on vehicle performance

NASA Technical Reports Server (NTRS)

Mueller, Donn C.; Turns, Stephen R.

1993-01-01

A one-dimensional model of a hydrocarbon/Al/O2(gaseous) fueled rocket combustion chamber was developed to study secondary atomization effects on propellant combustion. This chamber model was coupled with a two dimensional, two-phase flow nozzle code to estimate the two-phase flow losses associated with solid combustion products. Results indicate that moderate secondary atomization significantly reduces propellant burnout distance and Al2O3 particle size; however, secondary atomization provides only moderate decreases in two-phase flow induced I(sub sp) losses. Despite these two-phase flow losses, a simple mission study indicates that aluminum gel propellants may permit a greater maximum payload than the hydrocarbon/O2 bi-propellant combination for a vehicle of fixed propellant volume. Secondary atomization was also found to reduce radiation losses from the solid combustion products to the chamber walls, primarily through reductions in propellant burnout distance.

The evolution of structural and chemical heterogeneity during rapid solidification at gas atomization

NASA Astrophysics Data System (ADS)

Golod, V. M.; Sufiiarov, V. Sh

2017-04-01

Gas atomization is a high-performance process for manufacturing superfine metal powders. Formation of the powder particles takes place primarily through the fragmentation of alloy melt flow with high-pressure inert gas, which leads to the formation of non-uniform sized micron-scale particles and subsequent their rapid solidification due to heat exchange with gas environment. The article presents results of computer modeling of crystallization process, simulation and experimental studies of the cellular-dendrite structure formation and microsegregation in different size particles. It presents results of adaptation of the approach for local nonequilibrium solidification to conditions of crystallization at gas atomization, detected border values of the particle size at which it is possible a manifestation of diffusionless crystallization.

Atomizing-gas temperature effect on cryogenic spray dropsize

NASA Technical Reports Server (NTRS)

Ingebo, Robert D.

1993-01-01

Correlating expressions for two-phase flow breakup of liquid nitrogen, LN2, jets in sonic velocity nitrogen gasflows were obtained for an atomizing-gas temperature range of 111 to 442 K. The correlations were based on characteristic dropsize measurements obtained with a scattered-light scanner. The effect of droplet vaporization on the measurements of the volume-median dropsize was calculated by using previously determined heat and momentum transfer expressions for droplets evaporating in high-velocity gasflow. Finally, the dropsize of the originally unvaporized spray was calculated, normalized with respect to jet diameter and correlated with atomizing-gas flowrate and temperature.

The Basics of Electric Weapons and Pulsed-Power Technologies

DTIC Science & Technology

2012-01-01

launchers. DEWs send energy, instead of matter, toward a target, and can be separated into three types: laser weapons, particle -beam weapons, and high...beam’s energy de- position, target material, and flight dynamics is needed. Particle Beams A particle -beam weapon is a directed flow of atomic or sub...atomic particles . These parti- cles can be neutral or electrically charged. Neutral beams need to be used outside the atmosphere (in space), where

Atomizing, continuous, water monitoring module

DOEpatents

Thompson, C.V.; Wise, M.B.

1997-07-08

A system for continuously analyzing volatile constituents of a liquid is described. The system contains a pump for continuously pumping the liquid to be tested at a predetermined flow rate into an extracting container through a liquid directing tube having an orifice at one end and positioned to direct the liquid into the extracting container at a flow rate sufficient to atomize the liquid within the extracting container. A continuous supply of helium carrier gas at a predetermined flow rate is directed through a tube into the extracting container and co-mingled with the atomized liquid to extract the volatile constituents contained within the atomized liquid. The helium containing the extracted volatile constituents flows out of the extracting container into a mass spectrometer for an analysis of the volatile constituents of the liquid. 3 figs.

Atomizing, continuous, water monitoring module

DOEpatents

Thompson, Cyril V.; Wise, Marcus B.

1997-01-01

A system for continuously analyzing volatile constituents of a liquid is described. The system contains a pump for continuously pumping the liquid to be tested at a predetermined flow rate into an extracting container through a liquid directing tube having an orifice at one end and positioned to direct the liquid into the extracting container at a flow rate sufficient to atomize the liquid within the extracting container. A continuous supply of helium carrier gas at a predetermined flow rate is directed through a tube into the extracting container and co-mingled with the atomized liquid to extract the volatile constituents contained within the atomized liquid. The helium containing the extracted volatile constituents flows out of the extracting container into a mass spectrometer for an analysis of the volatile constituents of the liquid.

An unstructured shock-fitting solver for hypersonic plasma flows in chemical non-equilibrium

NASA Astrophysics Data System (ADS)

Pepe, R.; Bonfiglioli, A.; D'Angola, A.; Colonna, G.; Paciorri, R.

2015-11-01

A CFD solver, using Residual Distribution Schemes on unstructured grids, has been extended to deal with inviscid chemical non-equilibrium flows. The conservative equations have been coupled with a kinetic model for argon plasma which includes the argon metastable state as independent species, taking into account electron-atom and atom-atom processes. Results in the case of an hypersonic flow around an infinite cylinder, obtained by using both shock-capturing and shock-fitting approaches, show higher accuracy of the shock-fitting approach.

Low-noise humidity controller for imaging water mediated processes in atomic force microscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gaponenko, I., E-mail: iaroslav.gaponenko@unige.ch; Gamperle, L.; Herberg, K.

2016-06-15

We demonstrate the construction of a novel low-noise continuous flow humidity controller and its integration with a commercial variable-temperature atomic force microscope fluid cell, allowing precise control of humidity and temperature at the sample during nanoscale measurements. Based on wet and dry gas mixing, the design allows a high mechanical stability to be achieved by means of an ultrasonic atomiser for the generation of water-saturated gas, improving upon previous bubbler-based architectures. Water content in the flow is measured both at the inflow and outflow of the fluid cell, enabling the monitoring of water condensation and icing, and allowing controlled variationmore » of the sample temperature independently of the humidity. To benchmark the performance of the controller, the results of detailed noise studies and time-based imaging of the formation of ice layers on highly oriented pyrolytic graphite are shown.« less

Organic matter dynamics and stable isotope signature as tracers of the sources of suspended sediment

NASA Astrophysics Data System (ADS)

Schindler Wildhaber, Y.; Liechti, R.; Alewell, C.

2012-06-01

Suspended sediment (SS) and organic matter in rivers can harm brown trout Salmo trutta by affecting the health and fitness of free swimming fish and by causing siltation of the riverbed. The temporal and spatial dynamics of sediment, carbon (C), and nitrogen (N) during the brown trout spawning season in a small river of the Swiss Plateau were assessed and C isotopes as well as the C/N atomic ratio were used to distinguish autochthonous and allochthonous sources of organic matter in SS loads. The visual basic program IsoSource with 13Ctot and 15N as input isotopes was used to quantify the temporal and spatial sources of SS. Organic matter concentrations in the infiltrated and suspended sediment were highest during low flow periods with small sediment loads and lowest during high flow periods with high sediment loads. Peak values in nitrate and dissolved organic C were measured during high flow and high rainfall, probably due to leaching from pasture and arable land. The organic matter was of allochthonous sources as indicated by the C/N atomic ratio and δ13Corg. Organic matter in SS increased from up- to downstream due to an increase of pasture and arable land downstream of the river. The mean fraction of SS originating from upper watershed riverbed sediment decreased from up to downstream and increased during high flow at all measuring sites along the course of the river. During base flow conditions, the major sources of SS are pasture, forest and arable land. The latter increased during rainy and warmer winter periods, most likely because both triggered snow melt and thus erosion. The measured increase in DOC and nitrate concentrations during high flow support these modeling results. Enhanced soil erosion processes on pasture and arable land are expected with increasing heavy rain events and less snow during winter seasons due to climate change. Consequently, SS and organic matter in the river will increase, which will possibly affect brown trout negatively.

Mixing due Pulsating Turbulent Jets

NASA Astrophysics Data System (ADS)

Grosshans, Holger; Nygård, Alexander; Fuchs, Laszlo

Combustion efficiency and the formation of soot and/or NOx in Internal- Combustion engines depends strongly on the local air/fuel mixture, the local flow conditions and temperature. Modern diesel engines employ high injection pressure for improved atomization, but mixing is controlled largely by the flow in the cylinder. By injecting the fuel in pulses one can gain control over the atomization, evaporation and the mixing of the gaseous fuel. We show that the pulsatile injection of fuel enhances fuel break-up and the entrainment of ambient air into the fuel stream. The entrainment level depends on fuel property, such as fuel/air viscosity and density ratio, fuel surface-tension, injection speed and injection sequencing. Examples of enhanced break-up and mixing are given.

Spray Formation from a Charged Liquid Jet of a Dielectric Fluid

NASA Astrophysics Data System (ADS)

Doak, William; de Bellis, Victor; Chiarot, Paul; Microfluidics; Multiphase Flow Laboratory Team

2017-11-01

Atomization of a dielectric micro-jet is achieved via an electrohydrodynamic charge injection process. The atomizer is comprised of a grounded nozzle housing (ground electrode) and an internal probe (high voltage electrode) that is concentric with the emitting orifice. The internal probe is held at electric potentials ranging from 1-10 kV. A pressurized reservoir drives a dielectric fluid at a desired flow rate through the 100-micrometer diameter orifice. The fluid fills the cavity between the electrodes as it passes through the atomizer, impeding the transport of electrons. This process injects charge into the flowing fluid. Upon exiting the orifice, the emitted jet is highly charged and it deforms via a bending instability that is qualitatively similar to the behavior observed in the electrospinning of fibers. We observed bulging regions, or nodes, of highly charged fluid forming along the bent, rotating jet. These nodes separate into highly charged droplets that emit satellite droplets. The remaining ligaments break up due to capillarity in a process that produces additional satellites. All of the droplets possess a normal (inertial) and radial (electrically-driven) momentum component. The radial component is responsible for the formation of a conical spray envelope. Our research focuses on the jet, its break up, and the droplet dynamics of this system. This research supported by the American Chemical Society.

Simplified Thermo-Chemical Modelling For Hypersonic Flow

NASA Astrophysics Data System (ADS)

Sancho, Jorge; Alvarez, Paula; Gonzalez, Ezequiel; Rodriguez, Manuel

2011-05-01

Hypersonic flows are connected with high temperatures, generally associated with strong shock waves that appear in such flows. At high temperatures vibrational degrees of freedom of the molecules may become excited, the molecules may dissociate into atoms, the molecules or free atoms may ionize, and molecular or ionic species, unimportant at lower temperatures, may be formed. In order to take into account these effects, a chemical model is needed, but this model should be simplified in order to be handled by a CFD code, but with a sufficient precision to take into account the physics more important. This work is related to a chemical non-equilibrium model validation, implemented into a commercial CFD code, in order to obtain the flow field around bodies in hypersonic flow. The selected non-equilibrium model is composed of seven species and six direct reactions together with their inverse. The commercial CFD code where the non- equilibrium model has been implemented is FLUENT. For the validation, the X38/Sphynx Mach 20 case is rebuilt on a reduced geometry, including the 1/3 Lref forebody. This case has been run in laminar regime, non catalytic wall and with radiative equilibrium wall temperature. The validated non-equilibrium model is applied to the EXPERT (European Experimental Re-entry Test-bed) vehicle at a specified trajectory point (Mach number 14). This case has been run also in laminar regime, non catalytic wall and with radiative equilibrium wall temperature.

Miscut dependent surface evolution in the process of N-polar GaN(000 1 bar) growth under N-rich condition

NASA Astrophysics Data System (ADS)

Krzyżewski, Filip; Załuska-Kotur, Magdalena A.; Turski, Henryk; Sawicka, Marta; Skierbiszewski, Czesław

2017-01-01

The evolution of surface morphology during the growth of N-polar (000 1 bar) GaN under N-rich conditions is studied by kinetic Monte Carlo (kMC) simulations for two substrates miscuts 2° and 4°. The results are compared with experimentally observed surface morphologies of (000 1 bar) GaN layers grown by plasma-assisted molecular beam epitaxy. The proposed kMC two-component model of GaN(000 1 bar) surface where both types of atoms, nitrogen and gallium, attach to the surface and diffuse independently shows that at relatively high rates of the step flow (miscut angle < 2 °) the low mobility of gallium adatoms causes surface instabilities and leads to experimentally observed roughening while for low rates of the step flow (miscut 4°), smooth surface can be obtained. In the presence of almost immobile nitrogen atoms under N-rich conditions crystal growth is realized by the process of two-dimensional island nucleation and coalescence. Larger crystal miscut, lower growth rate or higher temperature results in similar effect of the surface smoothening. We show that the surface also smoothens for the growth conditions with very high N-excess. In the presence of large number of nitrogen atoms the mobility of gallium atoms changes locally thus providing easier coalescence of separated island.

Slurry atomizer for a coal-feeder and dryer used to provide coal at gasifier pressure

DOEpatents

Loth, John L.; Smith, William C.; Friggens, Gary R.

1982-01-01

The present invention is directed to a coal-water slurry atomizer for use a high-pressure dryer employed in a pumping system utilized to feed coal into a pressurized coal gasifier. The slurry atomizer is provided with a venturi, constant area slurry injection conduit, and a plurality of tangentially disposed steam injection ports. Superheated steam is injected into the atomizer through these ports to provide a vortical flow of the steam, which, in turn, shears slurry emerging from the slurry injection conduit. The droplets of slurry are rapidly dispersed in the dryer through the venturi where the water is vaporized from the slurry by the steam prior to deleterious heating of the coal.

Densities of Active species in N2/H2 RF and HF afterglows: application to surface nitriding of TiO2 nanocrystals

NASA Astrophysics Data System (ADS)

Ricard, André; Sarrette, Jean-Philippe; Wang, Yunfei; Kim, Yu-Kwon

2017-10-01

N2/0-5% H2 flowing afterglows from Radio Frequency (RF) and High Frequency (HF) sources have been analyzed by optical emission spectroscopy. In similar conditions (pressure 5-6 Torr, flow rate 0.5 slm and power 100 W), it is found in pure N2 a nearly constant N-atom density from the pink to the late afterglow, which is higher in HF than in RF: (1-2) and 0.4 × 1015 cm-3, respectively. With a N2/2% H2 gas mixture, the early afterglows is changed to a late afterglow with about the same N-atom density for both RF and HF cases: (8-9) × 1014 cm-3. Anatase TiO2 nanocrystals and Atomic Layer Deposition-grown films were exposed to the RF afterglows at room temperature. XPS analysis of the samples has shown that the highest N/Ti ratio of 0.24 can be achieved with the pure N2 late afterglow. In the HF pure N2 late afterglow, however, the N/Ti coverage was limited to 0.04 in spite of higher N-atom density. Such differences in the N content between the two RF and HF cases are attributed to the presence of a high O-atom impurity of 2 × 1013 cm-3 in HF as compared to that (8 × 1011 cm-3) in RF. Contribution to the topical issue "Plasma Sources and Plasma Processes (PSPP)", edited by Luis Lemos Alves, Thierry Belmonte and Tiberiu Minea

FUSE spectra of Lyman series emissions from the interplanetary medium

NASA Astrophysics Data System (ADS)

Clarke, John

Neutral atoms from the local ISM flow into the solar system producing diffuse emissions through resonant scattering of solar emissions. This wind contains the velocity distribution of the local ISM, plus modifications by solar gravity and radiation pressure near the Sun. In addition, the H atom motions are modified by charge exchange collisions with fast protons in the heliospheric interface region, while He atoms are little affected by charge exchange. Recent observations of the He and H flows in the solar system suggest that the He velocity of 26 km s-1 is that of the local ISM cloud, while the lower H velocity of 18-21 km s-1 and greatly increased velocity dispersion in the flow direction are due to an interface modification of the H flow. Remote observations of the H flow thereby provide a method to remotely study the heliospheric interface. The H flow has been studied from H Lyα line profiles at high spectral resolution observed by Copernicus, IUE, and HST, using the Earth orbital motion to Doppler shift the ISM from the geocoronal emission. One serious ambiguity in the interpretation of these data results from the optically thick Lyα emission, leading to uncertainties in derived values of the H density. Using FUSE to observe the brightness and line profile of the optically thin H Lyβ line, close in time to SOHO observations of the Lyα emission, we can determine accurately the optical depth and density n(H) along lines of sight upwind, downwind, and cross-flow. Comparing n(H) with the heliospheric helium density, and with the interstellar cloud HI/HeI ratio measured recently by the EUVE, will give the fraction of H atoms removed by charge exchange at the entrance to the heliosphere, and then the Local Cloud (or ambient ISM) electron density which governs the size of the heliosphere. We request FUSE sky aperture spectra in the two narrow science apertures obtained during other pointed observations, through cooperation in scheduling pointed observations in the correct look directions at the proper times of year.

Sediment source detection by stable isotope analysis, carbon and nitrogen content and CSSI in a small river of the Swiss Plateau

NASA Astrophysics Data System (ADS)

SchindlerWildhaber, Yael; Alewell, Christine; Birkholz, Axel

2014-05-01

Suspended sediment (SS) and organic matter in rivers can harm the fauna by affecting health and fitness of free swimming fish and by causing siltation of the riverbed. The temporal and spatial dynamics of sediment, carbon (C) and nitrogen (N) during the brown trout spawning season in a small river of the Swiss Plateau were assessed and C isotopes as well as the C/N atomic ratio were used to distinguish autochthonous and allochthonous sources of organic matter in SS loads. The visual basic program IsoSource with 13Ctot and 15N as input isotopes was used to quantify the temporal and spatial sources of SS. We determined compound specific stable carbon isotopes (CSSI) in fatty acids of possible sediment source areas to the stream in addition and compared them to SS from selected high flow and low flow events. Organic matter concentrations in the infiltrated and suspended sediment were highest during low flow periods with small sediment loads and lowest during high flow periods with high sediment loads. Peak values in nitrate and dissolved organic C were measured during high flow and high rainfall, probably due to leaching from pasture and arable land. The organic matter was of allochthonous sources as indicated by the C/N atomic ratio and δ13Corg. Organic matter in SS increased from up- to downstream due to an increase in sediment delivery from pasture and arable land downstream of the river. While the major sources of SS are pasture and arable land during base flow conditions, SS from forest soils increased during heavy rain events and warmer winter periods most likely due to snow melt which triggered erosion. Preliminary results of CSSI analysis of sediment source areas and comparison to SS of selected events indicate that differences in d13C values of individual fatty acids are too small to differentiate unambiguously between sediment sources.

Modeling Liquid Rocket Engine Atomization and Swirl/Coaxial Injectors

DTIC Science & Technology

2008-02-27

47-61, 2004. 2. Yoon, S . S ., and Heister, S . D., "A Fully Nonlinear Model for Atomization of High - Speed Jets," Engineering Analysis with... Power , V20, pp 468-479, 2004. 5. Yoon, S . S ., and Heister, S . D., "Analytic Solutions for Computing Velocities Induced from Potential Vortex Ring...Heister, S . D., "Three Dimensional Flow Simulations in Recessed Region of a Coaxial Injector," J. Propulsion and Power , V21, No.4, pp. 728-742

Temperature Dependences for the Reactions of O2- and O- with N and O Atoms in a Selected-Ion Flow Tube Instrument

DTIC Science & Technology

2013-10-07

quadrupole mass filter, mass selected, and injected into the flow reactor via a Venturi - type inlet. Ions undergo ∼105 collisions with helium buffer... gas at pressures of 0.4 to 0.8 Torr resulting in complete or near-complete thermalization.10 The higher pressure was used when studying the high...butterfly gate valve resulting in lower pumping speeds and thus longer reaction times. Neutrals were injected 49 cm before the end of the flow tube and

Flow visualization of a rocket injector spray using gelled propellant simulants

NASA Technical Reports Server (NTRS)

Green, James M.; Rapp, Douglas C.; Roncace, James

1991-01-01

A study was conducted at NASA-Lewis to compare the atomization characteristics of gelled and nongelled propellant simulants. A gelled propellant simulant composed of water, sodium hydroxide, and an acrylic acid polymer resin (as the gelling agent) was used to simulate the viscosity of an aluminum/PR-1 metallized fuel gel. Water was used as a comparison fluid to isolate the rheological effects of the water-gel and to simulate nongelled RP-1. The water-gel was injected through the central orifice of a triplet injector element and the central post of a coaxial injector element. Nitrogen gas flowed through the outer orifices of the triplet injector element and through the annulus of the coaxial injector element and atomized the gelled and nongelled liquids. Photographs of the water-gel spray patterns at different operating conditions were compared with images obtained using water and nitrogen. A laser light was used for illumination of the sprays. The results of the testing showed that the water sprays produced a finer and more uniform atomization than the water-gel sprays. Rheological analysis of the water-gel showed poor atomization caused by high viscosity of water-gel delaying the transition to turbulence.

A pressure tuned stop-flow atomic layer deposition process for MoS2 on high porous nanostructure and fabrication of TiO2/MoS2 core/shell inverse opal structure

NASA Astrophysics Data System (ADS)

Li, Xianglin; Puttaswamy, Manjunath; Wang, Zhiwei; Kei Tan, Chiew; Grimsdale, Andrew C.; Kherani, Nazir P.; Tok, Alfred Iing Yoong

2017-11-01

MoS2 thin films are obtained by atomic layer deposition (ALD) in the temperature range of 120-150 °C using Mo(CO)6 and dimethyl disulfide (DMDS) as precursors. A pressure tuned stop-flow ALD process facilitates the precursor adsorption and enables the deposition of MoS2 on high porous three dimensional (3D) nanostructures. As a demonstration, a TiO2/MoS2 core/shell inverse opal (TiO2/MoS2-IO) structure has been fabricated through ALD of TiO2 and MoS2 on a self-assembled multilayer polystyrene (PS) structure template. Due to the self-limiting surface reaction mechanism of ALD and the utilization of pressure tuned stop-flow ALD processes, the as fabricated TiO2/MoS2-IO structure has a high uniformity, reflected by FESEM and FIB-SEM characterization. A crystallized TiO2/MoS2-IO structure can be obtained through a post annealing process. As a 3D photonic crystal, the TiO2/MoS2-IO exhibits obvious stopband reflecting peaks, which can be adjusted through changing the opal diameters as well as the thickness of MoS2 layer.

Modeling of Turbulence Effects on Liquid Jet Atomization and Breakup

NASA Technical Reports Server (NTRS)

Trinh, Huu; Chen, C. P.

2004-01-01

Recent experimental investigations and physical modeling studies have indicated that turbulence behaviors within a liquid jet have considerable effects on the atomization process. For certain flow regimes, it has been observed that the liquid jet surface is highly turbulent. This turbulence characteristic plays a key role on the breakup of the liquid jet near to the injector exit. Other experiments also showed that the breakup length of the liquid core is sharply shortened as the liquid jet is changed from the laminar to the turbulent flow conditions. In the numerical and physical modeling arena, most of commonly used atomization models do not include the turbulence effect. Limited attempts have been made in modeling the turbulence phenomena on the liquid jet disintegration. The subject correlation and models treat the turbulence either as an only source or a primary driver in the breakup process. This study aims to model the turbulence effect in the atomization process of a cylindrical liquid jet. In the course of this study, two widely used models, Reitz's primary atomization (blob) and Taylor-Analogy-Break (TAB) secondary droplet breakup by O Rourke et al. are examined. Additional terms are derived and implemented appropriately into these two models to account for the turbulence effect on the atomization process. Since this enhancement effort is based on a framework of the two existing atomization models, it is appropriate to denote the two present models as T-blob and T-TAB for the primary and secondary atomization predictions, respectively. In the primary breakup model, the level of the turbulence effect on the liquid breakup depends on the characteristic time scales and the initial flow conditions. This treatment offers a balance of contributions of individual physical phenomena on the liquid breakup process. For the secondary breakup, an addition turbulence force acted on parent drops is modeled and integrated into the TAB governing equation. The drop size formed from this breakup regime is estimated based on the energy balance before and after the breakup occurrence. The turbulence energy is also considered in this process.

Injection, Atomization, Ignition and Combustion of Liquid Fuels in High-Speed Air Streams.

DTIC Science & Technology

1983-01-01

evaporiza- tieo. There is, therefore, some tim history of temperature (and vapor pressure) els0 the plum, and that is the process that we wish to simulate...and ~~’m~po 317.6 %Ui es*l11uhes fte e*oints in the heating process for the hot flow case ad te beatl for fte flow p"Islm -to be model led. The task now

The role of charge transfer in the oxidation state change of Ce atoms in the TM13-CeO2(111) systems (TM = Pd, Ag, Pt, Au): a DFT + U investigation.

PubMed

Tereshchuk, Polina; Freire, Rafael L H; Ungureanu, Crina G; Seminovski, Yohanna; Kiejna, Adam; Da Silva, Juarez L F

2015-05-28

Despite extensive studies of transition metal (TM) clusters supported on ceria (CeO2), fundamental issues such as the role of the TM atoms in the change in the oxidation state of Ce atoms are still not well understood. In this work, we report a theoretical investigation based on static and ab initio molecular dynamics density functional theory calculations of the interaction of 13-atom TM clusters (TM = Pd, Ag, Pt, Au) with the unreduced CeO2(111) surface represented by a large surface unit cell and employing Hubbard corrections for the strong on-site Coulomb correlation in the Ce f-electrons. We found that the TM13 clusters form pyramidal-like structures on CeO2(111) in the lowest energy configurations with the following stacking sequence, TM/TM4/TM8/CeO2(111), while TM13 adopts two-dimensional structures at high energy structures. TM13 induces a change in the oxidation state of few Ce atoms (3 of 16) located in the topmost Ce layer from Ce(IV) (itinerant Ce f-states) to Ce(III) (localized Ce f-states). There is a charge flow from the TM atoms to the CeO2(111) surface, which can be explained by the electronegativity difference between the TM (Pd, Ag, Pt, Au) and O atoms, however, the charge is not uniformly distributed on the topmost O layer due to the pressure induced by the TM13 clusters on the underlying O ions, which yields a decrease in the ionic charge of the O ions located below the cluster and an increase in the remaining O ions. Due to the charge flow mainly from the TM8-layer to the topmost O-layer, the charge cannot flow from the Ce(IV) atoms to the O atoms with the same magnitude as in the clean CeO2(111) surface. Consequently, the effective cationic charge decreases mainly for the Ce atoms that have a bond with the O atoms not located below the cluster, and hence, those Ce atoms change their oxidation state from IV to III. This increases the size of the Ce(III) compared with the Ce(IV) cations, which builds-in a strain within the topmost Ce layer, and hence, also affecting the location of the Ce(III) cations and the structure of the TM13 clusters.

Gas density effect on dropsize of simulated fuel sprays

NASA Technical Reports Server (NTRS)

Ingebo, Robert D.

1989-01-01

Two-phase flow in pneumatic two-fluid fuel nozzles was investigated experimentally to determine the effect of atomizing-gas density and gas mass-flux on liquid-jet breakup in sonic-velocity gas-flow. Dropsize data were obtained for the following atomizing-gases: nitrogen; argon; carbon dioxide; and helium. They were selected to cover a gas molecular-weight range of 4 to 44. Atomizing-gas mass-flux ranged from 6 to 50 g/sq cm-sec and four differently sized two-fluid fuel nozzles were used having orifice diameters that varied from 0.32 to 0.56 cm. The ratio of liquid-jet diameter to SMD, D sub o/D sub 32, was correlated with aerodynamic and liquid-surface forces based on the product of the Weber and Reynolds number, We*Re, and gas-to-liquid density ratio, rho sub g/rho sub l. To correlate spray dropsize with breakup forces produced by using different atomizing-gases, a new molecular-scale dimensionless group was derived. The derived dimensionless group was used to obtain an expression for the ratio of liquid-jet diameter to SMD, D sub o/D sub 32. The mathematical expression of this phenomenon incorporates the product of the Weber and Reynolds number, liquid viscosity, surface tension, acoustic gas velocity, the RMS velocity of gas molecules, the acceleration of gas molecules due to gravity, and gas viscosity. The mathematical expression encompassing these parameters agrees well with the atomization theory for liquid-jet breakup in high velocity gas flow. Also, it was found that at the same gas mass-flux, helium was considerably more effective than nitrogen in producing small droplet sprays with SMD's in the order of 5 micrometers.

Roles of additives and surface control in slurry atomization

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tsai, S.C.

1990-01-01

This report focuses on the effects of interparticle forces on the rheology and airblast atomization of micronized coal water slurry (CWS). We found that the CWS flow behavior index is determined by the relative importance of the interparticle van der Waals attraction and the interparticle electrostatic repulsion. The former intensifies as the Hamaker constant increases and the interparticle distance reduces while the latter increases as the particle surface charge density increases. The interparticle attraction causes particle aggregation, which breaks down at high shear rates, and thus leads to slurry pseudoplastic behavior. In contrast, the interparticle repulsion prevents particle aggregation andmore » thus leads to Newtonian behavior. Both atomized at low atomizing air pressures (less than 270 kPa) using twin-fluid jet atomizers of various distributor designs. We found that the atomized drop sizes of micronized coal water slurries substantially decrease as the atomizing air pressure exceeds a threshold value. The effects of coal volume fraction, coal particle surface charge, liquid composition and liquid viscosity on slurry atomization can be accounted for by their effects on slurry rheology. 26 refs.« less

Effects of gas liquid ratio on the atomization characteristics of gas-liquid swirl coaxial injectors

NASA Astrophysics Data System (ADS)

Kang, Zhongtao; Li, Qinglian; Zhang, Jiaqi; Cheng, Peng

2018-05-01

To understand the atomization characteristics and atomization mechanism of the gas-liquid swirl coaxial (GLSC) injector, a back-lighting photography technique has been employed to capture the instantaneous spray images with a high speed camera. The diameter and velocity of the droplets in the spray have been characterized with a Dantec Phase Doppler Anemometry (PDA) system. The effects of gas liquid ratio (GLR) on the spray pattern, Sauter mean diameter (SMD), diameter-velocity distribution and mass flow rate distribution were analyzed and discussed. The results show that the atomization of the GLSC injector is dominated by the film breakup when the GLR is small, and violent gas-liquid interaction when the GLR is large enough. The film breakup dominated spray can be divided into gas acceleration region and film breakup region while the violent gas-liquid interaction dominated spray can be divided into the gas acceleration region, violent gas-liquid interaction region and big droplets breakup region. The atomization characteristics of the GLSC injector is significantly influenced by the GLR. From the point of atomization performance, the increase of GLR has positive effects. It decreases the global Sauter mean diameter (GSMD) and varies the SMD distribution from a hollow cone shape (GLR = 0) to an inverted V shape, and finally slanted N shape. However, from the point of spatial distribution, the increase of GLR has negative effects, because the mass flow rate distribution becomes more nonuniform.

Vacuum ultraviolet radiation/atomic oxygen synergism in fluorinated ethylene propylene Teflon erosion

NASA Technical Reports Server (NTRS)

Stiegman, A. E.; Brinza, David E.; Laue, Eric G.; Anderson, Mark S.; Liang, Ranty H.

1992-01-01

A micrographic investigation is reported of samples of the fluorinated ethylene propylene (FEP) Teflon thermal-blanketing materials recovered from the Long-Duration Exposure Facility (LDEF) satellite. The samples are taken from the trailing edge and row 8 which correspond to exposures to vacuum UV (VUV) and VUV + atomic O, respectively. Data are taken from SEM and IR-spectra observations, and the LDEF leading-edge FEP shows a high degree of erosion, roughening, and sharp peaks angled in the direction of the flow of atomic O. The trailing edge sample influenced primarily by VUV shows a hard brittle layer and some cracked mosaic patterns. Comparisons to a reference sample suggest that the brittle layer is related to exposure to VUV and is removed by atomic-O impingement. Polymers that are stable to VUV radiation appear to be more stable in terms of atomic oxygen.

Understanding the mechanisms of amorphous creep through molecular simulation

NASA Astrophysics Data System (ADS)

Cao, Penghui; Short, Michael P.; Yip, Sidney

2017-12-01

Molecular processes of creep in metallic glass thin films are simulated at experimental timescales using a metadynamics-based atomistic method. Space-time evolutions of the atomic strains and nonaffine atom displacements are analyzed to reveal details of the atomic-level deformation and flow processes of amorphous creep in response to stress and thermal activations. From the simulation results, resolved spatially on the nanoscale and temporally over time increments of fractions of a second, we derive a mechanistic explanation of the well-known variation of creep rate with stress. We also construct a deformation map delineating the predominant regimes of diffusional creep at low stress and high temperature and deformational creep at high stress. Our findings validate the relevance of two original models of the mechanisms of amorphous plasticity: one focusing on atomic diffusion via free volume and the other focusing on stress-induced shear deformation. These processes are found to be nonlinearly coupled through dynamically heterogeneous fluctuations that characterize the slow dynamics of systems out of equilibrium.

Investigation of Atomization and Combustion Performance of Renewable Biofuels and the Effects of Ethanol Blending in Biodiesel

NASA Astrophysics Data System (ADS)

Silver, Adam Gregory

This thesis presents results from an experimental investigation of the macroscopic and microscopic atomization and combustion behavior of B99 biodiesel, ethanol, B99-ethanol blends, methanol, and an F-76-Algae biodiesel blend. In addition, conventional F-76 and Diesel #2 sprays were characterized as a base case to compare with. The physical properties and chemical composition of each fuel were measured in order to characterize and predict atomization performance. A variety of B99-ethanol fuel blends were used which demonstrate a tradeoff between lower density, surface tension, and viscosity with a decrease in the air to liquid ratio. A plain jet air-blast atomizer was used for both non-reacting and reacting tests. The flow rates for the alternative fuels were set by matching the power input provided by the baseline fossil fuels in order to simulate use as a drop in replacement. For this study, phase Doppler interferometry is employed to gain information on drop size, SMD, velocity, and volume flux distribution across the spray plume. A high speed camera is used to gather high speed cinematography of the sprays for observing breakup characteristics and providing additional insight. Reacting flow tests captured NOx, CO, and UHC emissions along with high speed footage used to predict soot levels based on flame luminosity. The results illustrate how the fuel type impacts the atomization and spray characteristics. The air-blast atomizer resulted in similar atomization performance among the DF2, F-76, and the F-76/Algae blend. While methanol and ethanol are not suitable candidates for this air-blast configuration and B99 produces significantly larger droplets, the addition of ethanol decreased drop sizes for all B99-ethanol blends by approximately 5 microns. In regards to reacting conditions, increased ethanol blending to B99 consistently lowered NOx emissions while decreasing combustion efficiency. Overall, lower NOx and CO emissions were achieved with the fuel blends than for conventional diesels, while the neat biofuels emitted overall less NOx per CO than the baseline fuels. This research clearly demonstrated that blends of two renewable fuels (B99 and ethanol improved (1) atomization and (2) emissions performance for the burner studied when compared to the baseline fossil fuels DF2 and F-76.

An automated flow injection system for metal determination by flame atomic absorption spectrometry involving on-line fabric disk sorptive extraction technique.

PubMed

Anthemidis, A; Kazantzi, V; Samanidou, V; Kabir, A; Furton, K G

2016-08-15

A novel flow injection-fabric disk sorptive extraction (FI-FDSE) system was developed for automated determination of trace metals. The platform was based on a minicolumn packed with sol-gel coated fabric media in the form of disks, incorporated into an on-line solid-phase extraction system, coupled with flame atomic absorption spectrometry (FAAS). This configuration provides minor backpressure, resulting in high loading flow rates and shorter analytical cycles. The potentials of this technique were demonstrated for trace lead and cadmium determination in environmental water samples. The applicability of different sol-gel coated FPSE media was investigated. The on-line formed complex of metal with ammonium pyrrolidine dithiocarbamate (APDC) was retained onto the fabric surface and methyl isobutyl ketone (MIBK) was used to elute the analytes prior to atomization. For 90s preconcentration time, enrichment factors of 140 and 38 and detection limits (3σ) of 1.8 and 0.4μgL(-1) were achieved for lead and cadmium determination, respectively, with a sampling frequency of 30h(-1). The accuracy of the proposed method was estimated by analyzing standard reference materials and spiked water samples. Copyright © 2016 Elsevier B.V. All rights reserved.

Spray drying for preservation of erythrocytes: effect of atomization on hemolysis.

PubMed

McLean, Mary; Han, Xiao-Yue; Higgins, Adam Z

2013-04-01

Spray drying has the potential to enable storage of erythrocytes at room temperature in the dry state. The spray drying process involves atomization of a liquid into small droplets and drying of the droplets in a gas stream. In this short report, we focus on the atomization process. To decouple atomization from drying, erythrocyte suspensions were sprayed with a two-fluid atomizer nozzle using humid nitrogen as the atomizing gas. The median droplet size was less than 100 μm for all of the spray conditions investigated, indicating that the suspensions were successfully atomized. Hemolysis was significantly affected by the hematocrit of the erythrocyte suspension, the suspension flow rate, and the atomizing gas flow rate (p<0.01 in all cases). Under appropriate conditions, it was possible to achieve less than 2% hemolysis, suggesting that spray drying may be a feasible option for erythrocyte biopreservation.

Pulsed high energy synthesis of fine metal powders

NASA Technical Reports Server (NTRS)

Witherspoon, F. Douglas (Inventor); Massey, Dennis W. (Inventor)

1999-01-01

Repetitively pulsed plasma jets generated by a capillary arc discharge at high stagnation pressure (>15,000 psi) and high temperature (>10,000 K) are utilized to produce 0.1-10 .mu.m sized metal powders and decrease cost of production. The plasma jets impact and atomize melt materials to form the fine powders. The melt can originate from a conventional melt stream or from a pulsed arc between two electrodes. Gas streams used in conventional gas atomization are replaced with much higher momentum flux plasma jets. Delivering strong incident shocks aids in primary disintegration of the molten material. A series of short duration, high pressure plasma pulses fragment the molten material. The pulses introduce sharp velocity gradients in the molten material which disintegrates into fine particles. The plasma pulses have peak pressures of approximately one kilobar. The high pressures improve the efficiency of disintegration. High gas flow velocities and pressures are achieved without reduction in gas density. Repetitively pulsed plasma jets will produce powders with lower mean size and narrower size distribution than conventional atomization techniques.

Integrated Physics-based Modeling and Experiments for Improved Prediction of Combustion Dynamics in Low-Emission Systems

NASA Technical Reports Server (NTRS)

Anderson, William E.; Lucht, Robert P.; Mongia, Hukam

2015-01-01

Concurrent simulation and experiment was undertaken to assess the ability of a hybrid RANS-LES model to predict combustion dynamics in a single-element lean direct-inject (LDI) combustor showing self-excited instabilities. High frequency pressure modes produced by Fourier and modal decomposition analysis were compared quantitatively, and trends with equivalence ratio and inlet temperature were compared qualitatively. High frequency OH PLIF and PIV measurements were also taken. Submodels for chemical kinetics and primary and secondary atomization were also tested against the measured behavior. For a point-wise comparison, the amplitudes matched within a factor of two. The dependence on equivalence ratio was matched. Preliminary results from simulation using an 18-reaction kinetics model indicated instability amplitudes closer to measurement. Analysis of the simulations suggested a band of modes around 1400 Hz were due to a vortex bubble breakdown and a band of modes around 6 kHz were due to a precessing vortex core hydrodynamic instability. The primary needs are directly coupled and validated ab initio models of the atomizer free surface flow and the primary atomization processes, and more detailed study of the coupling between the 3D swirling flow and the local thermoacoustics in the diverging venturi section.

Experimental study of the spray characteristics of a research airblast atomizer

NASA Technical Reports Server (NTRS)

Acosta, W. A.

1985-01-01

Airblast atomization was studied using a especially designed atomizer in which the liquid first impinges on a splash plate, then is directed radially outward and is atomized by the air passing through two concentric, vaned swirlers that swirl the air in opposite directions. The effect of flow conditions, air mass velocity (mass flow rate per unit area) and liquid to air ratio on the mean drop size was studied. Seven different ethanol solutions were used to simulate changes in fuel physical properties. The range of atomizing air velocities was from 30 to 80 m/s. The mean drop diameter was measured at ambient temperature (295 K) and atmospheric pressure.

Experimental study of the spray characteristics of a research airblast atomizer

NASA Technical Reports Server (NTRS)

Acosta, W. A.

1985-01-01

Airblast atomization was studied using a especially designed atomizer in which the liquid first impinges on a splash plate, then is directed radically outward and is atomized by the air passing through two concentric, vaned swirlers that swirl the air in opposite directions. The effect of flow conditions, air mass velocity (mass flow rate per unit area) and liquid to air ratio on the mean drop size was studied. Seven different ethanol solutions were used to simulate changes in fuel physical properties. The range of atomizing air velocities was from 30 to 80 m/s. The mean drop diameter was measured at ambient temperature (295 K) and atmospheric pressure.

High Fidelity Simulation of Primary Atomization in Diesel Engine Sprays

NASA Astrophysics Data System (ADS)

Ivey, Christopher; Bravo, Luis; Kim, Dokyun

2014-11-01

A high-fidelity numerical simulation of jet breakup and spray formation from a complex diesel fuel injector at ambient conditions has been performed. A full understanding of the primary atomization process in fuel injection of diesel has not been achieved for several reasons including the difficulties accessing the optically dense region. Due to the recent advances in numerical methods and computing resources, high fidelity simulations of atomizing flows are becoming available to provide new insights of the process. In the present study, an unstructured un-split Volume-of-Fluid (VoF) method coupled to a stochastic Lagrangian spray model is employed to simulate the atomization process. A common rail fuel injector is simulated by using a nozzle geometry available through the Engine Combustion Network. The working conditions correspond to a single orifice (90 μm) JP-8 fueled injector operating at an injection pressure of 90 bar, ambient condition at 29 bar, 300 K filled with 100% nitrogen with Rel = 16,071, Wel = 75,334 setting the spray in the full atomization mode. The experimental dataset from Army Research Lab is used for validation in terms of spray global parameters and local droplet distributions. The quantitative comparison will be presented and discussed. Supported by Oak Ridge Associated Universities and the Army Research Laboratory.

Measurements of uranium mass confined in high density plasmas

NASA Technical Reports Server (NTRS)

Stoeffler, R. C.

1976-01-01

An X-ray absorption method for measuring the amount of uranium confined in high density, rf-heated uranium plasmas is described. A comparison of measured absorption of 8 keV X-rays with absorption calculated using Beer Law indicated that the method could be used to measure uranium densities from 3 times 10 to the 16th power atoms/cu cm to 5 times 10 to the 18th power atoms/cu cm. Tests were conducted to measure the density of uranium in an rf-heated argon plasma with UF6 infection and with the power to maintain the discharge supplied by a 1.2 MW rf induction heater facility. The uranium density was measured as the flow rate through the test chamber was varied. A maximum uranium density of 3.85 times 10 to the 17th power atoms/cu cm was measured.

Atmospheric Pressure Method and Apparatus for Removal of Organic Matter with Atomic and Ionic Oxygen

NASA Technical Reports Server (NTRS)

Banks, Bruce A. (Inventor); Rutledge, Sharon K. (Inventor)

1996-01-01

A gas stream containing ionic and atomic oxygen in inert gas is used to remove organic matter from a substrate. The gas stream is formed by flowing a mixture of gaseous oxygen in an inert gas such as helium at atmospheric pressure past a high voltage, current limited, direct current arc which contacts the gas mixture and forms the ionic and atomic oxygen. The arc is curved at the cathode end and the ionic oxygen formed by the arc nearer to the anode end of the arc is accelerated in a direction towards the cathode by virtue of its charge. The relatively high mass to charge ratio of the ionic oxygen enables at least some of it to escape the arc before contacting the cathode and it is directed onto the substrate. This is useful for cleaning delicate substrates such as fine and historically important paintings and delicate equipment and the like.

Atmospheric Pressure Method and Apparatus for Removal of Organic Matter with Atomic and Ionic Oxygen

NASA Technical Reports Server (NTRS)

Banks, Bruce A. (Inventor); Rutledge, Sharon K. (Inventor)

1997-01-01

A gas stream containing ionic and atomic oxygen in inert gas is used to remove organic matter from a substrate. The gas stream is formed by flowing a mixture of gaseous oxygen in an inert gas such as helium at atmospheric pressure past a high voltage, current limited, direct current arc which contacts the gas mixture and forms the ionic and atomic oxygen. The arc is curved at the cathode end and the ionic oxygen formed by the arc nearer to the anode end of the arc is accelerated in a direction towards the cathode by virtue of its charge. The relatively high mass to charge ratio of the ionic oxygen enables at least some of it to escape the arc before contacting the cathode and it is directed onto the substrate. This is useful for cleaning delicate substrates such as fine and historically important paintings and delicate equipment and the like.

Molecular transport through capillaries made with atomic-scale precision

NASA Astrophysics Data System (ADS)

Radha, B.; Esfandiar, A.; Wang, F. C.; Rooney, A. P.; Gopinadhan, K.; Keerthi, A.; Mishchenko, A.; Janardanan, A.; Blake, P.; Fumagalli, L.; Lozada-Hidalgo, M.; Garaj, S.; Haigh, S. J.; Grigorieva, I. V.; Wu, H. A.; Geim, A. K.

2016-10-01

Nanometre-scale pores and capillaries have long been studied because of their importance in many natural phenomena and their use in numerous applications. A more recent development is the ability to fabricate artificial capillaries with nanometre dimensions, which has enabled new research on molecular transport and led to the emergence of nanofluidics. But surface roughness in particular makes it challenging to produce capillaries with precisely controlled dimensions at this spatial scale. Here we report the fabrication of narrow and smooth capillaries through van der Waals assembly, with atomically flat sheets at the top and bottom separated by spacers made of two-dimensional crystals with a precisely controlled number of layers. We use graphene and its multilayers as archetypal two-dimensional materials to demonstrate this technology, which produces structures that can be viewed as if individual atomic planes had been removed from a bulk crystal to leave behind flat voids of a height chosen with atomic-scale precision. Water transport through the channels, ranging in height from one to several dozen atomic planes, is characterized by unexpectedly fast flow (up to 1 metre per second) that we attribute to high capillary pressures (about 1,000 bar) and large slip lengths. For channels that accommodate only a few layers of water, the flow exhibits a marked enhancement that we associate with an increased structural order in nanoconfined water. Our work opens up an avenue to making capillaries and cavities with sizes tunable to ångström precision, and with permeation properties further controlled through a wide choice of atomically flat materials available for channel walls.

Laser diagnostics of welding plasma by polarization spectroscopy.

PubMed

Lucas, Owen; Alwahabi, Zeyad T; Linton, Valerie; Meeuwissen, Karel

2007-05-01

The application of polarization spectroscopy (PS) to detect atomic species in an atmospheric pressure welding plasma has been demonstrated. PS spectra of Na atoms, seeded in the shielding gas flow of a gas tungsten arc welding (GTAW) plasma, are presented at different pump beam energies. The nature of the PS technique was found to be very efficient in suppressing the high background emission associated with the welding plasma. The PS spectral profiles appear to be Lorentzian and Lorentzian cubed for high and low pump beam energy, respectively. The effect of beam steering, due to the thermal gradient in the interaction plasma zone, was addressed. It was found that there is 2% unavoidable error in the detectable PS signal.

Development of the seeding system used for laser velocimeter surveys of the NASA Low-Speed Centrifugal Compressor flow field

NASA Technical Reports Server (NTRS)

Wasserbauer, Charles A.; Hathaway, Michael D.

1993-01-01

An atomizer-based system for distributing high-volume rates of seed material was developed to support laser velocimeter investigations of the NASA Low-Speed Centrifugal Compressor flow field. The seeding system and the major concerns that were addressed during its development are described. Of primary importance were that the seed material be dispersed as single particles and that the liquid carrier used be completely evaporated before entering the compressor.

Velocity measurements in the plume of an arcjet engine

NASA Technical Reports Server (NTRS)

Pivirotto, T. J.; Deininger, W. D.

1987-01-01

A nonintrusive technique has been used to conduct a radial survey in the flow field of an arcjet engine plume. The technique measures the Doppler shift of an optically thin line resulting from recombination and relaxation processes in the high Mach number stream, in order to determine flow velocities. Atom temperature can also be calculated from the same Doppler-broadened line widths, when these shifts are measured with a scanning Fabry-Perot spectrometer whose design is presented in detail.

Quantum decoherence in electronic current flowing through carbon nanotubes induced by thermal atomic vibrations

NASA Astrophysics Data System (ADS)

Ishizeki, Keisuke; Sasaoka, Kenji; Konabe, Satoru; Souma, Satofumi; Yamamoto, Takahiro

2018-06-01

We theoretically investigate quantum decoherence in electronic currents flowing through metallic carbon nanotubes caused by thermal atomic vibrations using the time-dependent Schrödinger equation for an open system. We reveal that the quantum coherence of conduction electrons decays exponentially with tube length at a fixed temperature, and that the decay rate increases with temperature. We also find that the phase relaxation length due to the thermal atomic vibrations is inversely proportional to temperature.

Evaluation of a direct injection nebulizer interface for flow injection analysis and high performance liquid chromatography with inductively coupled plasma-atomic emission spectroscopic detection

DOE Office of Scientific and Technical Information (OSTI.GOV)

LaFreniere, K.E.

A direct injection nebulizer (DIN) was designed, developed and evaluated to determine its potential utilization as an effective interface for flow injection analysis (FIA) and high performance liquid chromatography (HPLC) coupled with inductively coupled plasma-atomic emission spectroscopic detection. The analytical figures of merit for the DIN when used as an interface for FIA-ICP-AES were found to be comparable to or better than those obtained with conventional pneumatic nebulization in terms of limits of detection (LODs), reproducibility, linearity, and interelement effects. In the HPLC mode, the LODDs were found to be comparable to those obtained by continuous-flow sample introduction into themore » ICP, or inferior by up to only a factor of four. Stable plasma operation was maintained for the DIN sample introduction of a variety of pure organic solvents, including acetonitrile, methanol, methyl-isobutylketone, and pyridine. The HPLC-DIN-ICP-AES facility was specifically applied for the speciation of inorganic and organo-metallic species contained in synthetic mixtures, vanilla extracts and a variety of energy-related materials, such as shale oil process water, coal extracts, shale oil, crude oil, and an SRC II. Suggestions for future research are also considered.« less

Determination of ultratrace elements in natural waters by solid-phase extraction and atomic spectrometry methods.

PubMed

Grotti, Marco; Abelmoschi, Maria Luisa; Soggia, Francesco; Frache, Roberto

2003-01-01

A study was carried out on the preconcentration of ultratrace amounts of cadmium, lead, manganese, copper and iron from high-salinity aqueous samples and determination by atomic spectrometry methods. Sample volume, amount of resin, loading flow rate, and elution volume were optimized in order to obtain the simultaneous preconcentration of all the analytes. Quantitative recoveries were obtained by using 200 mg of iminodiacetic resin with a loading flow rate of 2 mL min(-1), elution volume of 3 mL and sample volume of 50-450 mL. Only copper in seawater samples was not completely retained by the resin (60-70% recovery), due to unfavorable competition of iminodiacetic-active groups with organically bound metal.To quantify the metals in the eluates, two atomic spectrometry techniques were compared: electrothermal atomization atomic absorption spectrometry (ETAAS) and inductively coupled plasma-optical emission spectrometry (ICP-OES) with simultaneous CCD detection system. Both techniques are suitable for sample analysis with detection limits of 1.0, 4.7, 3.3, 6.8, and 53 ng L(-1) using ETAAS and 12, 122, 3.4, 17, and 21 ng L(-1) using ICP-OES for Cd, Pb, Mn, Cu, and Fe, respectively. Relative standard deviations of the procedures ranged from 1.7 to 14% at the sub-microg L(-1) concentration level. The accuracy of both methods was verified by analyzing various certified reference materials (river water, estuarine water, coastal and off-shore seawater).

Study of the reaction of atomic oxygen with aerosols

NASA Technical Reports Server (NTRS)

Akers, F. I.; Wightman, J. P.

1975-01-01

The rate of disappearance of atomic oxygen was measured at several pressures in a fast flow pyrex reactor system with its walls treated with (NH4)2SO4 (s), H2SO4 (l), and NH4CL (s). Atomic oxygen, P-3 was generated by dissociation of pure, low pressure oxygen in a microwave discharge. Concentrations of atomic oxygen were measured at several stations in the reactor system using chemiluminescent titration with NO2. Recombination efficiencies calculated from experimentally determined wall recombination rate constants are in good agreement with reported values for clean Pyrex and an H2SO4 coated wall. The recombination efficiency for (NH4)2SO4, results in a slightly lower value than for H2S04. A rapid exothermic reaction between atomic oxygen and the NH4Cl wall coating prevented recombination efficiency determination for this coating. The results show that the technique is highly useful for wall recombination measurements and as a means of extrapolating to the case of free stream aerosol-gas interactions.

Measuring air core characteristics of a pressure-swirl atomizer via a transparent acrylic nozzle at various Reynolds numbers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lee, Eun J.; Oh, Sang Youp; Kim, Ho Y.

2010-11-15

Because of thermal fluid-property dependence, atomization stability (or flow regime) can change even at fixed operating conditions when subject to temperature change. Particularly at low temperatures, fuel's high viscosity can prevent a pressure-swirl (or simplex) atomizer from sustaining a centrifugal-driven air core within the fuel injector. During disruption of the air core inside an injector, spray characteristics outside the nozzle reflect a highly unstable, nonlinear mode where air core length, Sauter mean diameter (SMD), cone angle, and discharge coefficient variability. To better understand injector performance, these characteristics of the pressure-swirl atomizer were experimentally investigated and data were correlated to Reynoldsmore » numbers (Re). Using a transparent acrylic nozzle, the air core length, SMD, cone angle, and discharge coefficient are observed as a function of Re. The critical Reynolds numbers that distinguish the transition from unstable mode to transitional mode and eventually to a stable mode are reported. The working fluids are diesel and a kerosene-based fuel, referred to as bunker-A. (author)« less

Kolmogorov Turbulence Defeated by Anderson Localization for a Bose-Einstein Condensate in a Sinai-Oscillator Trap

NASA Astrophysics Data System (ADS)

Ermann, Leonardo; Vergini, Eduardo; Shepelyansky, Dima L.

2017-08-01

We study the dynamics of a Bose-Einstein condensate in a Sinai-oscillator trap under a monochromatic driving force. Such a trap is formed by a harmonic potential and a repulsive disk located in the center vicinity corresponding to the first experiments of condensate formation by Ketterle and co-workers in 1995. We allow that the external driving allows us to model the regime of weak wave turbulence with the Kolmogorov energy flow from low to high energies. We show that in a certain regime of weak driving and weak nonlinearity such a turbulent energy flow is defeated by the Anderson localization that leads to localization of energy on low energy modes. This is in a drastic contrast to the random phase approximation leading to energy flow to high modes. A critical threshold is determined above which the turbulent flow to high energies becomes possible. We argue that this phenomenon can be studied with ultracold atoms in magneto-optical traps.

Demonstration of a stabilized alumina/ethanol colloidal dispersion technique for seeding high temperature air flows

NASA Technical Reports Server (NTRS)

Wernet, Mark P.; Skoch, Gary J.; Wernet, Judith H.

1995-01-01

Laser anemometry enables the measurement of complex flow fields via the light scattered from small particles entrained in the flow. In the study of turbomachinery, refractory seed materials are required for seeding the flow due to the high temperatures encountered. In this work we present a pH stabilization technique commonly employed in ceramic processing to obtain stable dispersions for generating aerosols of refractory seed material. By adding submicron alumina particles to a preadjusted pH solution of ethanol, a stable dispersion is obtained which when atomized, produces a high quality aerosol. Commercial grade alumina powder is used with a moderate size distribution. Other metal oxide powders in various polar solvents could also be used once the point of zero charge (pH(pzc)) of the powder in the solvent has been determined. Laser anemometry measurements obtained using the new seeding technique are compared to measurements obtained using Polystyrene Latex (PSL) spheres as the seed material.

Kolmogorov Turbulence Defeated by Anderson Localization for a Bose-Einstein Condensate in a Sinai-Oscillator Trap.

PubMed

Ermann, Leonardo; Vergini, Eduardo; Shepelyansky, Dima L

2017-08-04

We study the dynamics of a Bose-Einstein condensate in a Sinai-oscillator trap under a monochromatic driving force. Such a trap is formed by a harmonic potential and a repulsive disk located in the center vicinity corresponding to the first experiments of condensate formation by Ketterle and co-workers in 1995. We allow that the external driving allows us to model the regime of weak wave turbulence with the Kolmogorov energy flow from low to high energies. We show that in a certain regime of weak driving and weak nonlinearity such a turbulent energy flow is defeated by the Anderson localization that leads to localization of energy on low energy modes. This is in a drastic contrast to the random phase approximation leading to energy flow to high modes. A critical threshold is determined above which the turbulent flow to high energies becomes possible. We argue that this phenomenon can be studied with ultracold atoms in magneto-optical traps.

Where is the Most Likely Location Where the Secondary Interstellar Oxygen Atoms Are Created Around the Heliosheath?

NASA Astrophysics Data System (ADS)

Park, J.; Kucharek, H.; Szabo, A.; Paschalidis, N.; Grocer, A.; Jones, S.

2017-12-01

The secondary component of the interstellar neutral gas flow is originated from charge exchange between the undisturbed primary interstellar neutrals and the ions that have been deflected as they approach the heliopause. The secondary neutrals that are emitted from the interstellar ion flow through charge exchange carry information on the diverted flow and a fraction of them can travel to the Sun. Therefore, the secondary component of the interstellar neutrals is an excellent diagnostic tool to provide important information to constrain the shape of the heliopause. The presence of the secondary neutrals was predicted in the global heliospheric models and they are observed by Interstellar Boundary Explorer (IBEX) at Earth's orbit. Using the IBEX observations of neutral helium atoms, Kubiak et al. (2016, ApJS, 223, 25) approximated the parent distribution of the secondary interstellar He atoms (so-called Warm Breeze) with a homogeneous Maxwellian distribution function. Park et al. (2016, ApJ, 833, 130) analyzed IBEX observations of secondary interstellar helium and oxygen distributions at Earth's orbit. Lee et al. (2012, ApJS, 198, 10) constructed the heliospheric phase-space distribution function of an interstellar gas species in the Earth frame as a function of solar longitude. In this distribution, the authors assume that the distribution is a drifting Maxwellian at large distances from the Sun. In this study, we assume that a fraction of the secondary neutral atoms has a velocity vector toward the Sun and they can be described as a flow with a drifting Maxwellian distribution near the heliopause. Unlike the primary interstellar gas flow, the distribution of the secondary neutrals is expected to have a wide width and their bulk speeds are slower than the bulk speed of the primary interstellar gas flow. We compare Lee's distribution and IBEX observations of neutral oxygen atoms and then estimate the most likely direction where the secondary interstellar oxygen atoms are created near the heliopause.

Numerical Simulation of Atomization in Nozzle Injection Flow

NASA Astrophysics Data System (ADS)

Fan, Qinyin; Guo, Chenhai; Takagi, Tosimi; Narumiya, Kikuo; Hattori, Hiroshi

At the initial stage of injection, the injection flow has not yet broken up and in a range of small atmosphere pressure (16˜500KPa), the tip of the injection flow always forms a shape of mushroom. [1] [2] Moreover, the umbrella of the mushroom is always very big and its root is always very thin, especially when the atmosphere pressure is relatively low (88KPa, or 100mmHg). These phenomena are not known popularly and the reason of mushroom formation is not clear. In this paper, with the MARS method for simulating free surface, analysis of injection flow is practiced. The phenomena are reproduced and the reason is cleared that the formation of the mushroom is induced by the momentum exchange between the injection fuel flow with very high speed and the very complex flow of the air.

Vacuum low-temperature superconductivity is the essence of superconductivity - Atomic New Theory

NASA Astrophysics Data System (ADS)

Yongquan, Han

2010-10-01

The universe when the temperature closest to the Big Bang the temperature should be nuclear. Because, after the big bang, instant formation of atoms, nuclei and electrons between the absolute vacuum, the nucleus can not emit energy. (Radioactive elements, except in fact, radiation Yuan Su limited power emitted) which causes atomic nuclei and external temperature difference are so enormous that a large temperature difference reasons, all external particles became closer to the nucleus, affect the motion of electrons. When the conductor conductivity and thus affect the conductivity, the formation of resistance. Assumption that no particles affect the motion of electrons (except outside the nucleus) to form a potential difference will not change after the vector form, is now talking about the phenomenon of superconductivity, and then to introduce general, the gap between atoms in molecules or between small, valence electron number of high temperature superconducting conductors. This theory of atomic nuclei, but also explain the atomic and hydrogen bombs can remain after an explosion Why can release enormous energy reasons. Can also explain the ``super flow'' phenomenon. natural world. Tel 13241375685

Growth kinetics and characterizations of gallium nitride thin films by remote PECVD

NASA Technical Reports Server (NTRS)

Choi, S. W.; Bachmann, K. J.; Lucovsky, G.

1993-01-01

Thin films of GaN have been deposited at relatively low growth temperatures by remote plasma-enhanced chemical-vapor deposition (RPECVD), using a plasma excited NH3, and trimethylgallium (TMG), injected downstream from the plasma. The activation energy for GaN growth has been tentatively assigned to the dissociation of NH groups as the primary N-atom precursors in the surface reaction with adsorbed TMG, or TMG fragments. At high He flow rates, an abrupt increase in the growth rate is observed and corresponds to a change in the reaction mechanism attributed to the formation of atomic N. XRD reveals an increased tendency to ordered growth in the (0001) direction with increasing growth temperature, He flow rate, and RF plasma power. IR spectra show the fundamental lattice mode of GaN at 530 cm without evidence for vibrational modes of hydrocarbon groups.

Buried structure for increasing fabrication performance of micromaterial by electromigration

NASA Astrophysics Data System (ADS)

Kimura, Yasuhiro; Saka, Masumi

2016-06-01

The electromigration (EM) technique is a physical synthetic growth method for micro/nanomaterials. EM causes atomic diffusion in a metal line by high-density electron flows. The intentional control of accumulation and relaxation of atoms by EM can lead to the fabrication of a micro/nanomaterial. TiN passivation has been utilized as a component of sample in the EM technique. Although TiN passivation can simplify the cumbersome processes for preparing the sample, the leakage of current naturally occurs because of the conductivity of TiN as a side effect and decreases the performance of micro/nanomaterial fabrication. In the present work, we propose a buried structure, which contributes to significantly decreasing the current for fabricating an Al micromaterial by confining the current flow in the EM technique. The fabrication performance was evaluated based on the threshold current for fabricating an Al micromaterial using the buried structure and the previous structure with the leakage of current.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zagidullin, M V; Azyazov, V N; Malyshev, M S

The kinetics of the processes occurring in an O{sub 2} – I{sub 2} – He – H{sub 2}O gas flow in which photodissociation of molecular iodine at a wavelength close to 500 nm and excitation of atomic iodine on the {sup 2}P{sub 1/2} – {sup 2}P{sub 3/2} transition by narrow-band radiation near 1315 nm are implemented successively has been analysed. It is shown that implementation of these processes allows one to form an oxygen – iodine medium with a high degree of dissociation of molecular iodine and a relative content of singlet oxygen O{sub 2}(a{sup 1}Δ) exceeding 10%. Having formedmore » a supersonic gas flow with a temperature ∼100 K from this medium, one can reach a small-signal gain of about 10{sup -2} cm{sup -1} on the {sup 2}P{sub 1/2} – {sup 2}P{sub 3/2} transition in iodine atoms. The specific power per unit flow cross section in the oxygen – iodine laser with this active medium may reach ∼100 W cm{sup -2}. (active media)« less

Methods of analysis by the U.S. Geological Survey National Water Quality Laboratory; determination of arsenic and selenium in water and sediment by graphite furnace atomic absorption spectrometry

USGS Publications Warehouse

Jones, Sandra R.; Garbarino, John R.

1999-01-01

Graphite furnace-atomic absorption spectrometry (GF-AAS) is a sensitive, precise, and accurate technique that can be used to determine arsenic and selenium in samples of water and sediment. The GF-AAS method has been developed to replace the hydride generation-atomic absorption spectrometry (HG-AAS) methods because the method detection limits are similar, bias and variability are comparable, and interferences are minimal. Advantages of the GF-AAS method include shorter sample preparation time, increased sample throughput from simultaneous multielement analysis, reduced amount of chemical waste, reduced sample volume requirements, increased linear concentration range, and the use of a more accurate digestion procedure. The linear concentration range for arsenic and selenium is 1 to 50 micrograms per liter in solution; the current method detection limit for arsenic in solution is 0.9 microgram per liter; the method detection limit for selenium in solution is 1 microgram per liter. This report describes results that were obtained using stop-flow and low-flow conditions during atomization. The bias and variability of the simultaneous determination of arsenic and selenium by GF-AAS under both conditions are supported with results from standard reference materials--water and sediment, real water samples, and spike recovery measurements. Arsenic and selenium results for all Standard Reference Water Samples analyzed were within one standard deviation of the most probable values. Long-term spike recoveries at 6.25, 25.0, 37.5 micrograms per liter in reagent-, ground-, and surface-water samples for arsenic averaged 103 plus or minus 2 percent using low-flow conditions and 104 plus or minus 4 percent using stop-flow conditions. Corresponding recoveries for selenium were 98 plus or minus 13 percent using low-flow conditions and 87 plus or minus 24 percent using stop-flow conditions. Spike recoveries at 25 micrograms per liter in 120 water samples ranged from 97 to 99 percent for arsenic and from 82 to 93 percent for selenium, depending on the flow conditions used. Statistical analysis of dissolved and whole-water recoverable analytical results for the same set of water samples indicated that there is no significant difference between the GF-AAS and HG-AAS methods. Interferences related to various chemical constituents were also identified. Although sulfate and chloride in association with various cations might interfere with the determination of arsenic and selenium by GF-AAS, the use of a magnesium nitrate/palladium matrix modifier and low-flow argon during atomization helped to minimize such interferences. When using stabilized temperature platform furnace conditions where stop flow is used during atomization, the addition of hydrogen (5 percent volume/volume) to the argon minimized chemical interferences. Nevertheless, stop flow during atomization was found to be less effective than low flow in reducing interference effects.

a Marker-Based Eulerian-Lagrangian Method for Multiphase Flow with Supersonic Combustion Applications

NASA Astrophysics Data System (ADS)

Fan, Xiaofeng; Wang, Jiangfeng

2016-06-01

The atomization of liquid fuel is a kind of intricate dynamic process from continuous phase to discrete phase. Procedures of fuel spray in supersonic flow are modeled with an Eulerian-Lagrangian computational fluid dynamics methodology. The method combines two distinct techniques and develops an integrated numerical simulation method to simulate the atomization processes. The traditional finite volume method based on stationary (Eulerian) Cartesian grid is used to resolve the flow field, and multi-component Navier-Stokes equations are adopted in present work, with accounting for the mass exchange and heat transfer occupied by vaporization process. The marker-based moving (Lagrangian) grid is utilized to depict the behavior of atomized liquid sprays injected into a gaseous environment, and discrete droplet model 13 is adopted. To verify the current approach, the proposed method is applied to simulate processes of liquid atomization in supersonic cross flow. Three classic breakup models, TAB model, wave model and K-H/R-T hybrid model, are discussed. The numerical results are compared with multiple perspectives quantitatively, including spray penetration height and droplet size distribution. In addition, the complex flow field structures induced by the presence of liquid spray are illustrated and discussed. It is validated that the maker-based Eulerian-Lagrangian method is effective and reliable.

Fundamental Processes of Atomization in Fluid-Fluid Flows

NASA Technical Reports Server (NTRS)

McCready, M. J.; Chang, H.-C.; Leighton, D. T.

2001-01-01

This report outlines the major results of the grant "Fundamental Processes of Atomization in Fluid-Fluid Flows." These include: 1) the demonstration that atomization in liquid/liquid shear flow is driven by a viscous shear instability that triggers the formation of a long thin sheet; 2) discovery of a new mode of interfacial instability for oscillatory two-layer systems whereby a mode that originates within the less viscous liquid phase causes interfacial deformation as the oscillation proceeds; 3) the demonstration that rivulet formation from gravity front occurs because the local front shape specified by gravity and surface tension changes from a nose to a wedge geometry, thus triggering a large increase in viscous resistance; and 4) extension of the studies on nonlinear wave evolution on falling films and in stratified flow, particularly the evolution towards large-amplitude solitary waves that tend to generate drops.

Evaluation of a direct injection nebulizer interface for flow injection analysis and high performance liquid chromatography with inductively coupled plasma-atomic emission spectroscopic detection

DOE Office of Scientific and Technical Information (OSTI.GOV)

LaFreniere, K.E.

A direct injection nebulizer (DIN) was designed, developed, and evaluated to determine its potential utilization as an effective interface for flow injection analysis (FIA) and high performance liquid chromatography (HPLC) coupled with inductively coupled plasma-atomic emission spectroscopic detection. The analytical figures of merit for the DIN when used as an interface for FIA-ICP-AES were found to be comparable to or better than those obtained with conventional pneumatic nebulization in terms of limits of detection (LODs), reproducibility, linearity, and interelement effects. Stable plasma operation was maintained for the DIN sample introduction of a variety of pure organic solvents, including acetonitrile, methanol,more » methylisobutylketone, and pyridine. The HPLC-DIN-ICP-AES facility was specifically applied for the speciation of inorganic and organometallic species contained in synthetic mixtures, vanilla extracts, and a variety of energy-related materials, such as shale oil process water, coal extracts, shale oil, crude oil, and an SRC II. Suggestions for future research are also considered. 227 refs., 44 figs., 15 tabs.« less

Method and apparatus for detecting and measuring trace impurities in flowing gases

DOEpatents

Taylor, Gene W.; Dowdy, Edward J.

1979-01-01

Trace impurities in flowing gases may be detected and measured by a dynamic atomic molecular emission spectrograph utilizing as its energy source the energy transfer reactions of metastable species, atomic or molecular, with the impurities in the flowing gas. An electronically metastable species which maintains a stable afterglow is formed and mixed with the flowing gas in a region downstream from and separate from the region in which the metastable species is formed. Impurity levels are determined quantitatively by the measurement of line and/or band intensity as a function of concentration employing emission spectroscopic techniques.

High enthalpy hypersonic boundary layer flow

NASA Technical Reports Server (NTRS)

Yanow, G.

1972-01-01

A theoretical and experimental study of an ionizing laminar boundary layer formed by a very high enthalpy flow (in excess of 12 eV per atom or 7000 cal/gm) with allowance for the presence of helium driver gas is described. The theoretical investigation has shown that the use of variable transport properties and their respective derivatives is very important in the solution of equilibrium boundary layer equations of high enthalpy flow. The effect of low level helium contamination on the surface heat transfer rate is minimal. The variation of ionization is much smaller in a chemically frozen boundary layer solution than in an equilibrium boundary layer calculation and consequently, the variation of the transport properties in the case of the former was not essential in the integration. The experiments have been conducted in a free piston shock tunnel, and a detailed study of its nozzle operation, including the effects of low levels of helium driver gas contamination has been made. Neither the extreme solutions of an equilibrium nor of a frozen boundary layer will adequately predict surface heat transfer rate in very high enthalpy flows.

Effect of Surface Preparation and Gas Flow on Nitrogen Atom Surface Recombination

NASA Technical Reports Server (NTRS)

Prok, George M.

1961-01-01

The effects of surface preparation and gas flow on the recombination of nitrogen atoms at copper and platinum surfaces were determined. Atoms were generated by an electrodeless 2450-megacycle-per-second discharge, and their concentration was measured by gas-phase titration with nitric oxide. Test surfaces were either vacuum-evaporated films or spheres machined from bulk metal and cemented around small glass-bead thermistors. Heat released by recombination was measured as the difference in electrical energy required to maintain a given thermistor temperature with and without a catalytic surface exposed. Recombination coefficients measured at flow velocities of 1120, 1790, 2250, and 3460 centimeters per second and at pressures of 0.42 and 0.59 millimeter of mercury showed that flow conditions had no effect. The results were also independent of atom concentration. A rough indication of the temperature dependence was obtained; it was greater for copper than for platinum. Platinum films deposited on platinum or on glass had the same activity - about 3 percent of the atoms impinging recombined. With copper, however, the glass substrate greatly reduced the percent of atoms recombining over that of a bulk copper substrate where 4 percent of the impinging atoms recombined. This effect could be overcome by depositing a second film on top of the first. Bulk metal samples were subjected to various surface treatments including polishing, degreasing with a chlorinated hydrocarbon, washing with nitric acid, and rinsing with water. Polished, degreased platinum had low activity compared to an evaporated film, but nitric acid treatment made it equivalent. Polished, degreased copper was only slightly less active than a copper film; nitric acid etching decreased the activity still further, probably by preferentially exposing facets of low catalytic efficiency.

Vapor phase tri-methyl-indium seeding system suitable for high temperature spectroscopy and thermometry

DOE Office of Scientific and Technical Information (OSTI.GOV)

Whiddon, R.; Zhou, B.; Borggren, J.

2015-09-15

Tri-methyl-indium (TMI) is used as an indium transport molecule to introduce indium atoms to reactive hot gas flows/combustion environments for spectroscopic diagnostics. A seeding system was constructed to allow the addition of an inert TMI laden carrier gas into an air/fuel mixture burning consequently on a burner. The amount of the seeded TMI in the carrier gas can be readily varied by controlling the vapor pressure through the temperature of the container. The seeding process was calibrated using the fluorescent emission intensity from the indium 6{sup 2}S{sub 1/2} → 5{sup 2}P{sub 1/2} and 6{sup 2}S{sub 1/2} → 5{sup 2}P{sub 3/2}more » transitions as a function of the calculated TMI seeding concentration over a range of 2–45 ppm. The response was found to be linear over the range 3–22.5 ppm; at concentrations above 25 ppm there is a loss of linearity attributable to self-absorption or loss of saturation of TMI vapor pressure in the carrier gas flow. When TMI was introduced into a post-combustion environment via an inert carrier gas, molecular transition from InH and InOH radicals were observed in the flame emission spectrum. Combined laser-induced fluorescence and absorption spectroscopy were applied to detect indium atoms in the TMI seeded flame and the measured atomic indium concentration was found to be at the ppm level. This method of seeding organometallic vapor like TMI to a reactive gas flow demonstrates the feasibility for quantitative spectroscopic investigations that may be applicable in various fields, e.g., chemical vapor deposition applications or temperature measurement in flames with two-line atomic fluorescence.« less

Liquid Spray Characterization in Flow Fields with Centripetal Acceleration

DTIC Science & Technology

2014-03-27

25 2.4.1 Atomization of Liquid Jets ...volumetric heat release rates, easier light-up, wider burning range, and lower exhaust pollutant emissions [11]. 26 2.4.1 Atomization of Liquid Jets ...Atomization involves the interaction of consolidating and disruptive forces acting on a jet of liquid . The process of atomization can be further

Investigation of spray characteristics for flashing injection of fuels containing dissolved air and superheated fuels

NASA Technical Reports Server (NTRS)

Solomon, A. S. P.; Chen, L. D.; Faeth, G. M.

1982-01-01

The flow, atomization and spreading of flashing injector flowing liquids containing dissolved gases (jet/air) as well as superheated liquids (Freon II) were considered. The use of a two stage expansion process separated by an expansion chamber, ws found to be beneficial for flashing injection particularly for dissolved gas systems. Both locally homogeneous and separated flow models provided good predictions of injector flow properties. Conventional correlations for drop sizes from pressure atomized and airblast injectors were successfully modified, using the separated flow model to prescribe injector exit conditions, to correlate drop size measurements. Additional experimental results are provided for spray angle and combustion properties of sprays from flashing injectors.

K-distribution models for gas mixtures in hypersonic nonequilibrium flows

NASA Astrophysics Data System (ADS)

Bansal, Ankit

Calculation of nonequilibrium radiation field in plasmas around a spacecraft entering into an atmosphere at hypersonic velocities is a very complicated and computationally expensive task. The objective of this Dissertation is to collect state-of-the art spectroscopic data for the evaluation of spectral absorption and emission coefficients of atomic and molecular gases, develop efficient and accurate spectral models and databases, and study the effect of radiation on wall heat loads and flowfield around the spacecraft. The most accurate simulation of radiative transport in the shock layer requires calculating the gas properties at a large number of wavelengths and solving the Radiative Transfer Equation (RTE) in a line-by-line (LBL) fashion, which is prohibitively expensive for coupled simulations. A number of k-distribution based spectral models are developed for atomic lines, continuum and molecular bands that allow efficient evaluation of radiative properties and heat loads in hypersonic shock layer plasma. Molecular radiation poses very different challenges than atomic radiation. A molecular spectrum is governed by simultaneous electronic, vibrational and rotational transitions, making the spectrum very strongly dependent on wavelength. In contrast to an atomic spectrum, where line wings play a major role in heat transfer, most of the heat transfer in molecular spectra occurs near line centers. As the first step, k-distribution models are developed separately for atomic and molecular species, taking advantage of the fact that in the Earth's atmosphere the radiative field is dominated by atomic species (N and O) and in Titan's and Mars' atmospheres molecular bands of CN and CO are dominant. There are a number of practical applications where both atomic and molecular species are present, for example, the vacuum-ultra-violet spectrum during Earth's reentry conditions is marked by emission from atomic bound-bound lines and continuum and simultaneous absorption by strong bands of N2. For such cases, a new model is developed for the treatment of gas mixtures containing atomic lines, continuum and molecular bands. Full-spectrum k-distribution (FSK) method provides very accurate results compared to those obtained from the exact line-by-line method. For cases involving more extreme gradients in species concentrations and temperature, full-spectrum k-distribution model is relatively less accurate, and the method is refined by dividing the spectrum into a number of groups or scales, leading to the development of multi-scale models. The detailed methodology of splitting the gas mixture into scales is presented. To utilize the full potential of the k-distribution methods, pre-calculated values of k-distributions are stored in databases, which can later be interpolated at local flow conditions. Accurate and compact part-spectrum k-distribution databases are developed for atomic species and molecular bands. These databases allow users to calculate desired full-spectrum k-distributions through look-up and interpolation. Application of the new spectral models and databases to shock layer plasma radiation is demonstrated by solving the radiative transfer equation along typical one-dimensional flowfields in Earth's, Titan's and Mars' atmospheres. The k-distribution methods are vastly more efficient than the line-by-line method. The efficiency of the method is compared with the line-by-line method by measuring computational times for a number of test problems, showing typical reduction in computational time by a factor of more than 500 for property evaluation and a factor of about 32,000 for the solution of the RTE. A large percentage of radiative energy emitted in the shock-layer is likely to escape the region, resulting in cooling of the shock layer. This may change the flow parameters in the flowfield and, in turn, can affect radiative as well as convective heat loads. A new flow solver is constructed to simulate coupled hypersonic flow-radiation over a reentry vehicle. The flow solver employs a number of existing schemes and tools available in OpenFOAM; along with a number of additional features for high temperature, compressible and chemically reacting flows, and k-distribution models for radiative calculations. The radiative transport is solved with the one-dimensional tangent slab and P1 solvers, and also with the two-dimensional P1 solver. The new solver is applied to simulate flow around an entry vehicle in Martian atmosphere. Results for uncoupled and coupled flow-radiation simulations are presented, highlighting the effects of radiative cooling on flowfield and wall fluxes.

High-Fidelity Simulations of Electrically-Charged Atomizing Diesel-Type Jets

NASA Astrophysics Data System (ADS)

Gaillard, Benoit; Owkes, Mark; van Poppel, Bret

2015-11-01

Combustion of liquid fuels accounts for over a third of the energy usage today. Improving efficiency of combustion systems is critical to meet the energy needs while limiting environmental impacts. Additionally, a shift away from traditional fossil fuels to bio-derived alternatives requires fuel injection systems that can atomize fuels with a wide range of properties. In this work, the potential benefits of electrically-charged atomization is investigated using numerical simulations. Particularly, the electrostatic forces on the hydrodynamic jet are quantified and the impact of the forces is analyzed by comparing simulations of Diesel-type jets at realistic flow conditions. The simulations are performed using a state-of-the-art numerical framework that globally conserves mass, momentum, and the electric charge density even at the gas-liquid interface where discontinuities exist.

Quantized spin-momentum transfer in atom-sized magnetic systems

NASA Astrophysics Data System (ADS)

Loth, Sebastian

2010-03-01

Our ability to quickly access the vast amounts of information linked in the internet is owed to the miniaturization of magnetic data storage. In modern disk drives the tunnel magnetoresistance effect (TMR) serves as sensitive reading mechanism for the nanoscopic magnetic bits [1]. At its core lies the ability to control the flow of electrons with a material's magnetization. The inverse effect, spin transfer torque (STT), allows one to influence a magnetic layer by high current densities of spin-polarized electrons and carries high hopes for applications in non-volatile magnetic memory [2]. We show that equivalent processes are active in quantum spin systems. We use a scanning tunneling microscope (STM) operating at low temperature and high magnetic field to address individual magnetic structures and probe their spin excitations by inelastic electron tunneling [3]. As model system we investigate transition metal atoms adsorbed to a copper nitride layer grown on a Cu crystal. The magnetic atoms on the surface possess well-defined spin states [4]. Transfer of one magnetic atom to the STM tip's apex creates spin-polarization in the probe tip. The combination of functionalized tip and surface adsorbed atom resembles a TMR structure where the magnetic layers now consist of one magnetic atom each. Spin-polarized current emitted from the probe tip not only senses the magnetic orientation of the atomic spin system, it efficiently transfers spin angular momentum and pumps the quantum spin system between the different spin states. This enables further exploration of the microscopic mechanisms for spin-relaxation and stability of quantum spin systems. [4pt] [1] Zhu and Park, Mater. Today 9, 36 (2006).[0pt] [2] Huai, AAPPS Bulletin 18, 33 (2008).[0pt] [3] Heinrich et al., Science 306, 466 (2004).[0pt] [4] Hirjibehedin et al., Science 317, 1199 (2007).

Macroscopic irreversibility and microscopic paradox: A Constructal law analysis of atoms as open systems

PubMed Central

Lucia, Umberto

2016-01-01

The relation between macroscopic irreversibility and microscopic reversibility is a present unsolved problem. Constructal law is introduced to develop analytically the Einstein’s, Schrödinger’s, and Gibbs’ considerations on the interaction between particles and thermal radiation (photons). The result leads to consider the atoms and molecules as open systems in continuous interaction with flows of photons from their surroundings. The consequent result is that, in any atomic transition, the energy related to the microscopic irreversibility is negligible, while when a great number of atoms (of the order of Avogadro’s number) is considered, this energy related to irreversibility becomes so large that its order of magnitude must be taken into account. Consequently, macroscopic irreversibility results related to microscopic irreversibility by flows of photons and amount of atoms involved in the processes. PMID:27762333

Large-Area WS2 Film with Big Single Domains Grown by Chemical Vapor Deposition

NASA Astrophysics Data System (ADS)

Liu, Pengyu; Luo, Tao; Xing, Jie; Xu, Hong; Hao, Huiying; Liu, Hao; Dong, Jingjing

2017-10-01

High-quality WS2 film with the single domain size up to 400 μm was grown on Si/SiO2 wafer by atmospheric pressure chemical vapor deposition. The effects of some important fabrication parameters on the controlled growth of WS2 film have been investigated in detail, including the choice of precursors, tube pressure, growing temperature, holding time, the amount of sulfur powder, and gas flow rate. By optimizing the growth conditions at one atmospheric pressure, we obtained tungsten disulfide single domains with an average size over 100 μm. Raman spectra, atomic force microscopy, and transmission electron microscopy provided direct evidence that the WS2 film had an atomic layer thickness and a single-domain hexagonal structure with a high crystal quality. And the photoluminescence spectra indicated that the tungsten disulfide films showed an evident layer-number-dependent fluorescence efficiency, depending on their energy band structure. Our study provides an important experimental basis for large-area, controllable preparation of atom-thick tungsten disulfide thin film and can also expedite the development of scalable high-performance optoelectronic devices based on WS2 film.

Microwave plasma generation of hydrogen atoms for rocket propulsion

NASA Technical Reports Server (NTRS)

Chapman, R.; Filpus, J.; Morin, T.; Snellenberger, R.; Asmussen, J.; Hawley, M.; Kerber, R.

1981-01-01

A flow microwave plasma reaction system is used to study the conversion of hydrogen to hydrogen atoms as a function of pressure, power density, cavity tuning, cavity mode, and time in the plasma zone. Hydrogen atom concentration is measured down-stream from the plasma by NOCl titration. Extensive modeling of the plasma and recombination zones is performed with the plasma zone treated as a backmix reaction system and the recombination zone treated as a plug flow. The thermodynamics and kinetics of the recombination process are examined in detail to provide an understanding of the conversion of recombination energy to gas kinetic energy. It is found that cavity tuning, discharge stability, and optimum power coupling are critically dependent on the system pressure, but nearly independent of the flow rate.

Advanced gas atomization production of oxide dispersion strengthened (ODS) Ni-base superalloys through process and solidification control

NASA Astrophysics Data System (ADS)

Meyer, John Louis Lamb

A novel gas atomization reaction synthesis (GARS) method was utilized to produce precursor Ni-Cr-Y-Ti powder with a surface oxide and an internal rare earth (RE)-containing intermetallic. Although Al is necessary for industrial superalloy production, the Ni-Cr base alloy system was selected as a simplified system more amenable to characterization. This was done in an effort to better study the effects of processing parameters. Consolidation and heat-treatment were performed to promote the exchange of oxygen from the surface oxide to the RE intermetallic to form nanometric oxide dispersoids. Alloy selection was aided by an internal oxidation and serial grinding experiment that found that Hf-containing alloys may form more stable dispersoids than Ti-containing alloys, but the Hf-containing system exhibited five different oxide phases and two different intermetallics compared to the two oxide phases and one intermetallic in the Ti-containing alloys. Since the simpler Ti-containing system was easier to characterize, and make observations on the effects of processing parameters, the Ti-containing system was used for experimental atomization trials. An internal oxidation model was used to predict the heat treatment times necessary for dispersoid formation as a function of powder size and temperature. A new high-pressure gas atomization (HPGA) nozzle was developed with the aim of promoting fine powder production at scales similar to that of the high gas-flow and melt-flow of industrial atomizers. The atomization nozzle was characterized using schlieren imaging and aspiration pressure testing to determine the optimum melt delivery tip geometry and atomization pressure to promote enhanced secondary atomization mechanisms. Six atomization trials were performed to investigate the effects of gas atomization pressure and reactive-gas concentration on the particle size distribution (PSD). Also, the effect on the rapidly solidified microstructure (as a function of powder size) was investigated as a function of reactive-gas composition and bulk alloy composition. The results indicate that the pulsation mechanism and optimum PSDs reported in the literature were not observed. Also, it was determined that reactive gas may marginally improve the PSD, but further experiments are required. The oxygen content in the gas was also not found to be detrimental to the microstructure (i.e., did not catalyze nucleation), but may have removed potent catalytic nucleation sites, although not enough to significantly alter the microstructure. Overall, the downstream injection of oxygen was not found to significantly affect either the PSD or undercooling (as inferred from microstructure and XRD observations), but injection further upstream, including in the gas atomization nozzle, remains to be investigated.

Development of Low Cost Gas Atomization of Precursor Powders for Simplified ODS Alloy Production

DOE Office of Scientific and Technical Information (OSTI.GOV)

Anderson, Iver

2014-08-05

A novel gas atomization reaction synthesis (GARS) method was developed in this project to enable production (at our partner’s facility) a precursor Ni-Cr-Y-Ti powder with a surface oxide and an internal rare earth (RE) containing intermetallic compound (IMC) phase. Consolidation and heat-treatment experiments were performed at Ames Lab to promote the exchange of oxygen from the surface oxide to the RE intermetallic to form nano-metric oxide dispersoids. Alloy selection was aided by an internal oxidation and serial grinding experiments at Ames Lab and found that Hf-containing alloys may form more stable dispersoids than Ti-containing alloy, i.e., the Hf-containing system exhibitedmore » five different oxide phases and two different intermetallics compared to the two oxide phases and one intermetallic in the Ti-containing alloys. Since the simpler Ti-containing system was less complex to characterize, and make observations on the effects of processing parameters, the Ti-containing system was selected by Ames Lab for experimental atomization trials at our partner. An internal oxidation model was developed at Ames Lab and used to predict the heat treatment times necessary for dispersoid formation as a function of powder size and temperature. A new high-pressure gas atomization (HPGA) nozzle was developed at Ames Lab with the aim of promoting fine powder production at scales similar to that of the high gas-flow and melt-flow of industrial atomizers. The atomization nozzle was characterized using schlieren imaging and aspiration pressure testing at Ames Lab to determine the optimum melt delivery tip geometry and atomization pressure to promote enhanced secondary atomization mechanisms. Six atomization trials were performed at our partner to investigate the effects of: gas atomization pressure and reactive gas concentration on the particle size distribution (PSD) and the oxygen content of the resulting powder. Also, the effect on the rapidly solidified microstructure (as a function of powder size) was investigated at Ames Lab as a function of reactive gas composition and bulk alloy composition. The results indicated that the pulsatile gas atomization mechanism and a significantly enhanced yield of fine powders reported in the literature for this type of process were not observed. Also it was determined that reactive gas may marginally improve the fine powder yield but further experiments are required. The oxygen content in the gas also did not have any detrimental effect on the microstructure (i.e. did not significantly reduce undercooling). On the contrary, the oxygen addition to the atomization gas may have mitigated some potent catalytic nucleation sites, but not enough to significantly alter the microstructure vs. particle size relationship. Overall the downstream injection of oxygen was not found to significantly affect either the particle size distribution or undercooling (as inferred from microstructure and XRD observations) but injection further upstream, including in the gas atomization nozzle, remains to be investigated in later work.« less

Pressure atomizer having multiple orifices and turbulent generation feature

DOEpatents

VanBrocklin, Paul G.; Geiger, Gail E.; Moran, Donald James; Fournier, Stephane

2002-01-01

A pressure atomizer includes a silicon plate having a top surface and a bottom surface. A portion of the top surface defines a turbulent chamber. The turbulent chamber is peripherally bounded by the top surface of the plate. The turbulent chamber is recessed a predetermined depth relative to the top surface. The silicon plate further defines at least one flow orifice. Each flow orifice extends from the bottom surface of the silicon plate to intersect with and open into the turbulent chamber. Each flow orifice is in fluid communication with the turbulent chamber.

Study the effect of nitrogen flow rate on tribological properties of tantalum nitride based coatings

NASA Astrophysics Data System (ADS)

Chauhan, Dharmesh B.; Chauhan, Kamlesh V.; Sonera, Akshay L.; Makwana, Nishant S.; Dave, Divyeshkumar P.; Rawal, Sushant K.

2018-05-01

Tantalum Nitride (TaN) based coatings are well-known for their high temperature stability and chemical inertness. We have studied the effect of nitrogen flow rate variation on the structural and tribological properties of TaN based coating deposited by RF magnetron sputtering process. The nitrogen flow rate was varied from 5 to 30 sccm. X-ray diffractometer (XRD) and Atomic Force Microscopy (AFM) were used to determine structure and surface topography of coating. Pin on disc tribometer was used to determine tribological properties of coating. TaN coated brass and mild steel substrates shows higher wear resistance compared to uncoated substrates of brass and mild steel.

Modeling of atomization and distribution of drop-liquid fuel in unsteady swirling flows in a combustion chamber and free space

NASA Astrophysics Data System (ADS)

Sviridenkov, A. A.; Toktaliev, P. D.; Tretyakov, V. V.

2018-03-01

Numerical and experimental research of atomization and propagation of drop-liquid phase in swirling flow behind the frontal device of combustion chamber was performed. Numerical procedure was based on steady and unsteady Reynolds equations solution. It's shown that better agreement with experimental data could be obtained with unsteady approach. Fractional time step method was implemented to solve Reynolds equations. Models of primary and secondary breakup of liquid fuel jet in swirling flows are formulated and tested. Typical mean sizes of fuel droplets for base operational regime of swirling device and combustion chamber were calculated. Comparison of main features of internal swirling flow in combustion chamber with unbounded swirling flow was made.

IBEX-Lo Observations of Secondary Interstellar Helium and Oxygen Distributions

NASA Astrophysics Data System (ADS)

Park, J.; Kucharek, H.; Moebius, E.; Kubiak, M. A.; Bzowski, M.; Galli, A.; McComas, D. J.

2015-12-01

Observations of the Interstellar Boundary EXplorer (IBEX) show, among other features, the pristine interstellar neutral gas flow and additional populations associated with neutral helium and oxygen. Kubiak et al. (2014, ApJS, 213, 29) discovered the "Warm Breeze", or additional He component, which is slower and warmer than the primary interstellar He population and its flow direction differs by about 19° from the interstellar neutral (ISN) flow. Park et al. (2015, ApJS, In Press) studied the combined count rate maps of heavy neutral atoms with three statistical analysis methods and found an extended tail of the ISN O flow, centered around 190° in ecliptic longitude and +15° in ecliptic latitude, or approximately 38° from the ISN O and Ne flow peak. The most likely sources for the Warm Breeze and the extended O tail may be secondary populations of interstellar He and O, created by charge exchange between ISN atoms and interstellar ions in the outer heliosheath. The charge exchange between interstellar He atoms and He+ ions is the most important reaction to generate the secondary neutral He in the outer heliosheath, with a reaction rate of 1.7×10-10 s-1 and a mean free path of ~950 AU. For O+, the charge exchange with interstellar H atoms with a rate ~1.0×10-9 s-1 and a mean free path of ~100 AU is most important. Because the differences in the reaction rates and atomic masses for He and O result in different velocity distributions in the outer heliosheath, the directional distributions of these populations at Earth orbit are not identical. In this study, we use the IBEX flux maps of the observed helium and oxygen atoms to compare their directional distributions. These observed distributions may provide constraints and information to improve our current understanding of the interactions in the outer heliosheath.

Analysis of the Zeeman effect on D α spectra on the EAST tokamak

NASA Astrophysics Data System (ADS)

Gao, Wei; Huang, Juan; Wu, Chengrui; Xu, Zong; Hou, Yumei; Jin, Zhao; Chen, Yingjie; Zhang, Pengfei; Zhang, Ling; Wu, Zhenwei; EAST Team

2017-04-01

Based on the passive spectroscopy, the {{{D}}}α atomic emission spectra in the boundary region of the plasma have been measured by a high resolution optical spectroscopic multichannel analysis (OSMA) system in EAST tokamak. The Zeeman splitting of the {{{D}}}α spectral lines has been observed. A fitting procedure by using a nonlinear least squares method was applied to fit and analyze all polarization π and +/- σ components of the {{{D}}}α atomic spectra to acquire the information of the local plasma. The spectral line shape was investigated according to emission spectra from different regions (e.g., low-field side and high-field side) along the viewing chords. Each polarization component was fitted and classified into three energy categories (the cold, warm, and hot components) based on different atomic production processes, in consistent with the transition energy distribution by calculating the gradient of the {{{D}}}α spectral profile. The emission position, magnetic field intensity, and flow velocity of a deuterium atom were also discussed in the context. Project supported by the National Natural Science Foundation of China (Grant Nos. 11275231 and 11575249) and the National Magnetic Confinement Fusion Energy Research Program of China (Grant No. 2015GB110005).

Measurements of the Diameter and Velocity Distributions of Atomized Tablet-Coating Solutions for Pharmaceutical Applications

NASA Astrophysics Data System (ADS)

Osterday, Kathryn; Aliseda, Alberto; Lasheras, Juan

2009-11-01

The atomization of colloidal suspensions is of particular interest to the manufacturing of tablets and pills used as drug delivery systems by the pharmaceutical industry. At various stages in the manufacturing process, the tablets are coated with a spray of droplets produced by co-axial atomizers. The mechanisms of droplet size and spray formation in these types of atomizers are dominated by Kelvin-Helmholtz and Raleigh-Taylor instabilities for both low[1] and high[2] Ohnesorge numbers. We present detailed phase Doppler measurements of the Sauter Mean Diameter of the droplets produced by co-axial spray atomizers using water-based colloidal suspensions with solid concentrations ranging from fifteen to twenty percent and acetone-based colloidal suspensions with solid concentrations ranging from five to ten percent. Our results compare favorably with predictions by Aliseda's model. This suggests that the final size distribution is mainly determined by the instabilities caused by the sudden acceleration of the liquid interface. [1]Varga, C. M., et al. (2003) J. Fluid Mech. 497:405-434 [2]Aliseda, A. et al. (2008). J. Int. J. Multiphase Flow, 34(2), 161-175.

Atomic Species Associated with the Portevin-Le Chatelier Effect in Superalloy 718 Studied by Mechanical Spectroscopy

NASA Astrophysics Data System (ADS)

Max, B.; San Juan, J.; Nó, M. L.; Cloue, J. M.; Viguier, B.; Andrieu, E.

2018-06-01

In many Ni-based superalloys, dynamic strain aging (DSA) generates an inhomogeneous plastic deformation resulting in jerky flow known as the Portevin-Le Chatelier (PLC) effect. This phenomenon has a deleterious effect on the mechanical properties and, at high temperature, is related to the diffusion of substitutional solute atoms toward the core of dislocations. However, the question about the nature of the atomic species responsible for the PLC effect at high temperature still remains open. The goal of the present work is to answer this important question; to this purpose, three different 718-type and a 625 superalloy were studied through a nonconventional approach by mechanical spectroscopy. The internal friction (IF) spectra of all the studied alloys show a relaxation peak P 718 (at 885 K for 0.1 Hz) in the same temperature range, 700 K to 950 K, as the observed PLC effect. The activation parameters of this relaxation peak have been measured, E a( P 718) = 2.68 ± 0.05 eV, τ 0 = 2·10-15 ± 1 s as well as its broadening factor β = 1.1. Experiments on different alloys and the dependence of the relaxation strength on the amount of Mo attribute this relaxation to the stress-induced reorientation of Mo-Mo dipoles due to the short distance diffusion of one Mo atom by exchange with a vacancy. Then, it is concluded that Mo is the atomic species responsible for the high-temperature PLC effect in 718 superalloy.

Atomic Species Associated with the Portevin-Le Chatelier Effect in Superalloy 718 Studied by Mechanical Spectroscopy

NASA Astrophysics Data System (ADS)

Max, B.; San Juan, J.; Nó, M. L.; Cloue, J. M.; Viguier, B.; Andrieu, E.

2018-03-01

In many Ni-based superalloys, dynamic strain aging (DSA) generates an inhomogeneous plastic deformation resulting in jerky flow known as the Portevin-Le Chatelier (PLC) effect. This phenomenon has a deleterious effect on the mechanical properties and, at high temperature, is related to the diffusion of substitutional solute atoms toward the core of dislocations. However, the question about the nature of the atomic species responsible for the PLC effect at high temperature still remains open. The goal of the present work is to answer this important question; to this purpose, three different 718-type and a 625 superalloy were studied through a nonconventional approach by mechanical spectroscopy. The internal friction (IF) spectra of all the studied alloys show a relaxation peak P 718 (at 885 K for 0.1 Hz) in the same temperature range, 700 K to 950 K, as the observed PLC effect. The activation parameters of this relaxation peak have been measured, E a(P 718) = 2.68 ± 0.05 eV, τ 0 = 2·10-15 ± 1 s as well as its broadening factor β = 1.1. Experiments on different alloys and the dependence of the relaxation strength on the amount of Mo attribute this relaxation to the stress-induced reorientation of Mo-Mo dipoles due to the short distance diffusion of one Mo atom by exchange with a vacancy. Then, it is concluded that Mo is the atomic species responsible for the high-temperature PLC effect in 718 superalloy.

A facility to produce an energetic, ground state atomic oxygen beam for the simulation of the Low-Earth Orbit environment

NASA Technical Reports Server (NTRS)

Ketsdever, Andrew D.; Weaver, David P.; Muntz, E. P.

1994-01-01

Because of the continuing commitment to activity in low-Earth orbit (LEO), a facility is under development to produce energetic atmospheric species, particularly atomic oxygen, with energies ranging from 5 to 80 eV. This relatively high flux facility incorporates an ion engine to produce the corresponding specie ion which is charge exchanged to produce a neutral atomic beam. Ion fluxes of around 10(exp 15) sec(exp -1) with energies of 20-70 eV have been achieved. A geometrically augmented inertially tethered charge exchanger (GAITCE) was designed to provide a large column depth of charge exchange gas while reducing the gas load to the low pressure portion of the atomic beam facility. This is accomplished using opposed containment jets which act as collisional barriers to the escape of the dense gas region formed between the jets. Leak rate gains to the pumping system on the order of 10 were achieved for moderate jet mass flows. This system provides an attractive means for the charge exchange of atomic ions with a variety of gases to produce energetic atomic beams.

Copper atom based measurements of velocity and turbulence in arc jet flows

NASA Technical Reports Server (NTRS)

Marinelli, William J.; Kessler, William J.; Allen, Mark G.; Arepalli, Sivaram; Scott, Carl D.

1991-01-01

Laboratory and field measurements were combined with a modeling effort to explore the feasibility of using atomic copper laser-induced fluorescence to measure velocity, turbulence, and temperature in arcjet flows. Both CW and pulsed frequency-doubled dye lasers were used to demonstrate the ability to measure velocity with 10 percent accuracy at rates of 200,000 cm/s in a rarefied flow of Cu atoms seeded in He. The pulsed laser established a threshold energy for power-broadening of the absorption line at 3.5 x 10 to the -8th J/sq cm. Field measurements at the NASA/JSC 10-MW arcjet facility demonstrated the ability to perform these measurements under actual test conditions. The use of this technique to measure freestream temperatures in the flow was examined for the 0.08/cm linewidth laser used in the NASA/JSC effort. Finally, single-shot turbulence measurements at the USAF/AEDC 35-MW H2 arcjet facility were measured with 4 percent accuracy using the laser/absorption line-overlap technique.

Hyperbaric hydrothermal atomic force microscope

DOEpatents

Knauss, Kevin G.; Boro, Carl O.; Higgins, Steven R.; Eggleston, Carrick M.

2002-01-01

A hyperbaric hydrothermal atomic force microscope (AFM) is provided to image solid surfaces in fluids, either liquid or gas, at pressures greater than normal atmospheric pressure. The sample can be heated and its surface imaged in aqueous solution at temperatures greater than 100.degree. C. with less than 1 nm vertical resolution. A gas pressurized microscope base chamber houses the stepper motor and piezoelectric scanner. A chemically inert, flexible membrane separates this base chamber from the sample cell environment and constrains a high temperature, pressurized liquid or gas in the sample cell while allowing movement of the scanner. The sample cell is designed for continuous flow of liquid or gas through the sample environment.

Hyperbaric Hydrothermal Atomic Force Microscope

DOEpatents

Knauss, Kevin G.; Boro, Carl O.; Higgins, Steven R.; Eggleston, Carrick M.

2003-07-01

A hyperbaric hydrothermal atomic force microscope (AFM) is provided to image solid surfaces in fluids, either liquid or gas, at pressures greater than normal atmospheric pressure. The sample can be heated and its surface imaged in aqueous solution at temperatures greater than 100.degree. C. with less than 1 nm vertical resolution. A gas pressurized microscope base chamber houses the stepper motor and piezoelectric scanner. A chemically inert, flexible membrane separates this base chamber from the sample cell environment and constrains a high temperature, pressurized liquid or gas in the sample cell while allowing movement of the scanner. The sample cell is designed for continuous flow of liquid or gas through the sample environment.

Modeling the Partial Atomic Charges in Inorganometallic Molecules and Solids and Charge Redistribution in Lithium-Ion Cathodes

DOE PAGES

Wang, Bo; Li, Shaohong L.; Truhlar, Donald G.

2014-10-30

Partial atomic charges are widely used for the description of charge distributions of molecules and solids. These charges are useful to indicate the extent of charge transfer and charge flow during chemical reactions in batteries, fuel cells, and catalysts and to characterize charge distributions in capacitors, liquid-phase electrolytes, and solids and at electrochemical interfaces. However, partial atomic charges given by various charge models differ significantly, especially for systems containing metal atoms. In the present study, we have compared various charge models on both molecular systems and extended systems, including Hirshfeld, CM5, MK, ChElPG, Mulliken, MBS, NPA, DDEC, LoProp, and Badermore » charges. Their merits and drawbacks are compared. The CM5 charge model is found to perform well on the molecular systems, with a mean unsigned percentage deviation of only 9% for the dipole moments. We therefore formulated it for extended systems and applied it to study charge flow during the delithiation process in lithium-containing oxides used as cathodes. Our calculations show that the charges given by the CM5 charge model are reasonable and that during the delithiation process, the charge flow can occur not only on the transition metal but also on the anions. The oxygen atoms can lose a significant density of electrons, especially for deeply delithiated materials. We also discuss other methods in current use to analyze the charge transfer and charge flow in batteries, in particular the use of formal charge, spin density, and orbital occupancy. Here, we conclude that CM5 charges provide useful information in describing charge distributions in various materials and are very promising for the study of charge transfer and charge flows in both molecules and solids.« less

Modeling the Partial Atomic Charges in Inorganometallic Molecules and Solids and Charge Redistribution in Lithium-Ion Cathodes.

PubMed

Wang, Bo; Li, Shaohong L; Truhlar, Donald G

2014-12-09

Partial atomic charges are widely used for the description of charge distributions of molecules and solids. These charges are useful to indicate the extent of charge transfer and charge flow during chemical reactions in batteries, fuel cells, and catalysts and to characterize charge distributions in capacitors, liquid-phase electrolytes, and solids and at electrochemical interfaces. However, partial atomic charges given by various charge models differ significantly, especially for systems containing metal atoms. In the present study, we have compared various charge models on both molecular systems and extended systems, including Hirshfeld, CM5, MK, ChElPG, Mulliken, MBS, NPA, DDEC, LoProp, and Bader charges. Their merits and drawbacks are compared. The CM5 charge model is found to perform well on the molecular systems, with a mean unsigned percentage deviation of only 9% for the dipole moments. We therefore formulated it for extended systems and applied it to study charge flow during the delithiation process in lithium-containing oxides used as cathodes. Our calculations show that the charges given by the CM5 charge model are reasonable and that during the delithiation process, the charge flow can occur not only on the transition metal but also on the anions. The oxygen atoms can lose a significant density of electrons, especially for deeply delithiated materials. We also discuss other methods in current use to analyze the charge transfer and charge flow in batteries, in particular the use of formal charge, spin density, and orbital occupancy. We conclude that CM5 charges provide useful information in describing charge distributions in various materials and are very promising for the study of charge transfer and charge flows in both molecules and solids.

Microscopic Analysis of Current and Mechanical Properties of Nafion® Studied by Atomic Force Microscopy

PubMed Central

Hiesgen, Renate; Helmly, Stefan; Galm, Ines; Morawietz, Tobias; Handl, Michael; Friedrich, K. Andreas

2012-01-01

The conductivity of fuel cell membranes as well as their mechanical properties at the nanometer scale were characterized using advanced tapping mode atomic force microscopy (AFM) techniques. AFM produces high-resolution images under continuous current flow of the conductive structure at the membrane surface and provides some insight into the bulk conducting network in Nafion membranes. The correlation of conductivity with other mechanical properties, such as adhesion force, deformation and stiffness, were simultaneously measured with the current and provided an indication of subsurface phase separations and phase distribution at the surface of the membrane. The distribution of conductive pores at the surface was identified by the formation of water droplets. A comparison of nanostructure models with high-resolution current images is discussed in detail. PMID:24958429

Study on atomization and combustion characteristics of LOX/methane pintle injectors

NASA Astrophysics Data System (ADS)

Fang, Xin-xin; Shen, Chi-bing

2017-07-01

Influences of main structural parameters of the LOX/methane pintle injectors on atomization cone angles and combustion performances were studied by experiments and numerical simulation respectively. In addition, improvement was brought up to the structure of the pintle injectors and combustion flow fields of two different pintle engines were obtained. The results indicate that, with increase of the gas-liquid mass flow ratio, the atomization cone angle decreases. In the condition of the same gas-liquid mass flow ratio, as the thickness of the LOX-injection gap grows bigger, the atomization cone angle becomes smaller. In the opposite, when the half cone angle of the LOX-injection gap grows bigger, the atomization cone angle becomes bigger. Moreover, owing to the viscous effects of the pintle tip, with increase of the 'skip distance', the atomization cone angle gets larger. Two big recirculation zones in the combustor lead to combustion stability of the pintle engines. When the value of the non-dimensional 'skip distance' is near 1, the combustion efficiency of the pintle engines is the highest. Additionally, pintle engines with LOX injected in quadrangular slots can acquire better mixing efficiency of the propellants and higher combustion efficiency as the gas methane can pass through the adjacent slots. However, the annular-channel type of pintle injectors has an 'enclosed' area near the pintle tip which has a great negative influence on the combustion efficiency.

Pulse regime in formation of fractal fibers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Smirnov, B. M., E-mail: bmsmirnov@gmail.com

The pulse regime of vaporization of a bulk metal located in a buffer gas is analyzed as a method of generation of metal atoms under the action of a plasma torch or a laser beam. Subsequently these atoms are transformed into solid nanoclusters, fractal aggregates and then into fractal fibers if the growth process proceeds in an external electric field. We are guided by metals in which transitions between s and d-electrons of their atoms are possible, since these metals are used as catalysts and filters in interaction with gas flows. The resistance of metal fractal structures to a gasmore » flow is evaluated that allows one to find optimal parameters of a fractal structure for gas flow propagation through it. The thermal regime of interaction between a plasma pulse or a laser beam and a metal surface is analyzed. It is shown that the basic energy from an external source is consumed on a bulk metal heating, and the efficiency of atom evaporation from the metal surface, that is the ratio of energy fluxes for vaporization and heating, is 10{sup –3}–10{sup –4} for transient metals under consideration. A typical energy flux (~10{sup 6} W/cm{sup 2}), a typical surface temperature (~3000 K), and a typical pulse duration (~1 μs) provide a sufficient amount of evaporated atoms to generate fractal fibers such that each molecule of a gas flow collides with the skeleton of fractal fibers many times.« less

Agreement between experimental and theoretical effects of nitrogen gas flowrate on liquid jet atomization

NASA Technical Reports Server (NTRS)

Ingebo, Robert D.

1987-01-01

Two-phase flows were investigated by using high velocity nitrogen gas streams to atomize small-diameter liquid jets. Tests were conducted primarily in the acceleration-wave regime for liquid jet atomization, where it was found that the loss of droplets due to vaporization had a marked effect on drop size measurements. In addition, four identically designed two-fluid atomizers were fabricated and tested for similarity of spray profiles. A scattered-light scanner was used to measure a characteristic drop diameter, which was correlated with nitrogen gas flowrate. The exponent of 1.33 for nitrogen gas flowrate is identical to that predicted by atomization theory for liquid jet breakup in the acceleration-wave regime. This is higher than the value of 1.2 which was previously obtained at a sampling distance of 4.4 cm downstream of the atomizer. The difference is attributed to the fact that drop-size measurements obtained at a 2.2 cm sampling distance are less effected by vaporization and dispersion of small droplets and therefore should give better agreement with atomization theory. Profiles of characteristic drop diameters were also obtained by making at least five line-of-sight measurements across the spray at several horizontal positions above and below the center line of the spray.

Agreement between experimental and theoretical effects of nitrogen gas flowrate on liquid jet atomization

NASA Technical Reports Server (NTRS)

Ingebo, Robert D.

1987-01-01

Two-phase flows were investigated by using high velocity nitrogen gas streams to atomize small-diameter liquid jets. Tests were conducted primarily in the acceleration-wave regime for liquid jet atomization, where it was found that the loss of droplets due to vaporization had a marked effect on drop-size measurements. In addition, four identically designed two-fluid atomizers were fabricated and tested for similarity of spray profiles. A scattered-light scanner was used to measure a characteristic drop diameter, which was correlated with nitrogen gas flowrate. The exponent of 1.33 for nitrogen gas flowrate is identical to that predicted by atomization theory for liquid jet breakup in the acceleration-wave regime. This is higher than the value of 1.2 which was previously obtained at a smapling distance of 4.4 cm downstream of the atomizer. The difference is attributed to the fact that drop-size measurements obtained at a 2.2 cm sampling distance are less affected by vaporization and dispersion of small droplets and therefore should give better agreement with atomization theory. Profiles of characteristic drop diameters were also obtained by making at least five line-of-sight measurements across the spray at several horizontal positions above and below the center line of the spray.

Assessment of Some Atomization Models Used in Spray Calculations

NASA Technical Reports Server (NTRS)

Raju, M. S.; Bulzin, Dan

2011-01-01

The paper presents the results from a validation study undertaken as a part of the NASA s fundamental aeronautics initiative on high altitude emissions in order to assess the accuracy of several atomization models used in both non-superheat and superheat spray calculations. As a part of this investigation we have undertaken the validation based on four different cases to investigate the spray characteristics of (1) a flashing jet generated by the sudden release of pressurized R134A from cylindrical nozzle, (2) a liquid jet atomizing in a subsonic cross flow, (3) a Parker-Hannifin pressure swirl atomizer, and (4) a single-element Lean Direct Injector (LDI) combustor experiment. These cases were chosen because of their importance in some aerospace applications. The validation is based on some 3D and axisymmetric calculations involving both reacting and non-reacting sprays. In general, the predicted results provide reasonable agreement for both mean droplet sizes (D32) and average droplet velocities but mostly underestimate the droplets sizes in the inner radial region of a cylindrical jet.

[Research on optimization of mathematical model of flow injection-hydride generation-atomic fluorescence spectrometry].

PubMed

Cui, Jian; Zhao, Xue-Hong; Wang, Yan; Xiao, Ya-Bing; Jiang, Xue-Hui; Dai, Li

2014-01-01

Flow injection-hydride generation-atomic fluorescence spectrometry was a widely used method in the industries of health, environmental, geological and metallurgical fields for the merit of high sensitivity, wide measurement range and fast analytical speed. However, optimization of this method was too difficult as there exist so many parameters affecting the sensitivity and broadening. Generally, the optimal conditions were sought through several experiments. The present paper proposed a mathematical model between the parameters and sensitivity/broadening coefficients using the law of conservation of mass according to the characteristics of hydride chemical reaction and the composition of the system, which was proved to be accurate as comparing the theoretical simulation and experimental results through the test of arsanilic acid standard solution. Finally, this paper has put a relation map between the parameters and sensitivity/broadening coefficients, and summarized that GLS volume, carrier solution flow rate and sample loop volume were the most factors affecting sensitivity and broadening coefficients. Optimizing these three factors with this relation map, the relative sensitivity was advanced by 2.9 times and relative broadening was reduced by 0.76 times. This model can provide a theoretical guidance for the optimization of the experimental conditions.

Experimental and Numerical Investigation of Air Radiation in Superorbital Expanding Flow

NASA Technical Reports Server (NTRS)

Wei, Han; Morgan, Richard G.; McIntyre, Timothy J.; Brandis, Aaron M.; Johnston, Christopher O.

2017-01-01

To investigate air radiation in expanding flows and provide experimental data for validating associated computational models, experiments were conducted in the X2 expansion tunnel facility at the Centre for Hypersonics of the University of Queensland. A 54 turning angle wedge model was employed to generate steady expanding flows with in flow total enthalpies of 50.7, 63.4 and 75.4 MJkg. VUV spectra from 118 to 180 nm were acquired across the wedge at three equispaced distances away from the top of the model, as well as through its top surface. High speed filtered images were also obtained by coupling a Shimadzu 1 MHz high speed camera to a bandpass filter to obtain calibrated images of the 777 nm oxygen triplet. Both the across-wedge VUV spectra and filtered images of the 777 nm atomic oxygen were compared with NEQAIR simulations, which were performed using flow field data from two-dimensional CFD simulations with two-temperature 11-species air chemistry utilizing the in-house Navier-Stokes flow solver Eilmer3. Data extracted from consecutive frames of the filtered high speed images confirmed up to 8 s of available test time for the flow conditions tested. For the strongly radiating 149 and 174 nm atomic nitrogen lines, large disagreement between experimental data and NEQAIR predictions can be observed from the start of the expansion fan where the electron-ion recombination process commences. The spatial extent, or spans of the radiance profiles of the 149 and 174 nm N lines are significantly under predicted by NEQAIR, and are very close to those of N, N+ and electron number density profiles, which follow that of flow density. The electron-ion recombination process is proposed as the main reason for these discrepancies. The comparisons between NEQAIR simulations and filtered images of the 777 nm oxygen triplet show good agreement in the post-shock compression region and the start of the expansion fan for the 63.4 MJkg condition, but with up to a factor of three over prediction by NEQAIR further downstream, which is attributed to electron-impact excitation. Similar trends are found with the 75.4 MJkg condition, with reduced level of agreement in the compression region, which can be due to uncertainties in inflow condition.

Experimental and Numerical Investigation of Air Radiation in Superorbital Expanding Flow

NASA Technical Reports Server (NTRS)

Wei, Han; Morgan, Richard G.; Mcintyre, Timothy J.; Brandis, Aaron M.; Johnston, Christopher O.

2017-01-01

To investigate air radiation in expanding flows and provide experimental data for validating associated computational models, experiments were conducted in the X2 expansion tunnel facility at the Centre for Hypersonics of the University of Queensland. A 54deg turning angle wedge model was employed to generate steady expanding flows with in flow total enthalpies of 50.7, 63.4 and 75.4 MJ/kg. VUV spectra from 118 to 180 nm were acquired across the wedge at three equispaced distances away from the top of the model, as well as through its top surface. High speed filtered images were also obtained by coupling a Shimadzu 1 MHz high speed camera to a bandpass filter to obtain calibrated images of the 777 nm oxygen triplet. Both the across-wedge VUV spectra and filtered images of the 777 nm atomic oxygen were compared with NEQAIR simulations, which were performed using flow field data from two-dimensional CFD simulations with two-temperature 11-species air chemistry utilising the in-house Navier-Stokes flow solver Eilmer3. Data extracted from consecutive frames of the filtered high speed images confirmed up to 8 s of available test time for the flow conditions tested. For the strongly radiating 149 and 174 nm atomic nitrogen lines, large disagreement between experimental data and NEQAIR predictions can be observed from the start of the expansion fan where the electron-ion recombination process commences. The spatial extent, or spans of the radiance profiles of the 149 and 174 nm N lines are significantly underpredicted by NEQAIR, and are very close to those of N, N+ and electron number density profiles, which follow that of flow density. The electron-ion recombination process is proposed as the main reason for these discrepancies. The comparisons between NEQAIR simulations and filtered images of the 777 nm oxygen triplet show good agreement in the post-shock compression region and the start of the expansion fan for the 63.4 MJ/kg condition, but with up to a factor of three overprediction by NEQAIR further downstream, which is attributed to electron-impact excitation. Similar trends are found with the 75.4 MJ/kg condition, with reduced level of agreement in the compression region, which can be due to uncertainties in inflow condition.

In Situ Solid Particle Generator

NASA Technical Reports Server (NTRS)

Agui, Juan H.; Vijayakumar, R.

2013-01-01

Particle seeding is a key diagnostic component of filter testing and flow imaging techniques. Typical particle generators rely on pressurized air or gas sources to propel the particles into the flow field. Other techniques involve liquid droplet atomizers. These conventional techniques have drawbacks that include challenging access to the flow field, flow and pressure disturbances to the investigated flow, and they are prohibitive in high-temperature, non-standard, extreme, and closed-system flow conditions and environments. In this concept, the particles are supplied directly within a flow environment. A particle sample cartridge containing the particles is positioned somewhere inside the flow field. The particles are ejected into the flow by mechanical brush/wiper feeding and sieving that takes place within the cartridge chamber. Some aspects of this concept are based on established material handling techniques, but they have not been used previously in the current configuration, in combination with flow seeding concepts, and in the current operational mode. Unlike other particle generation methods, this concept has control over the particle size range ejected, breaks up agglomerates, and is gravity-independent. This makes this device useful for testing in microgravity environments.

Spray Characteristics and Tribo-Mechanical Properties of High-Velocity Arc-Sprayed WC-W2C Iron-Based Coatings

NASA Astrophysics Data System (ADS)

Tillmann, W.; Hagen, L.; Kokalj, D.

2017-10-01

In terms of arc-sprayed coatings, the lamellar coating microstructure is mainly affected by the atomization behavior of the molten electrode tips. When using compressed air, oxide formations occur during atomization, across the particle-laden spray plume and when the molten droplets splash onto the substrate. Within the scope of this study, the potential of a high-velocity arc-spraying process due to elevated atomization gas pressures and its effect on the spray and coating characteristics was analyzed using a cast tungsten carbide (CTC)-reinforced FeCMnSi cored wire. Since the atomization behavior corresponds with the electrode phenomena, the power spectrum and the droplet formation were observed during spraying. The tribo-mechanical properties of CTC-FeCMnSi coatings were examined in dry sliding experiments and indentation tests. In addition, adhesion tests and metallographic investigations were carried out to analyze the bonding strength, cohesive behavior, and lamellar microstructure. The occurrence of oxide phases was evaluated by x-ray diffraction and electron microscopy. Moreover, the oxygen content was determined by using glow discharge optical emission spectroscopy as well as energy-dispersive x-ray spectroscopy. With respect to elevated atomization gas pressures, a dense microstructure with improved adhesion to the substrate and reduced surface roughness was observed. Dry sliding experiments revealed an advanced wear behavior of specimens, when using above average increased atomization gas pressures. Analytic methods verified the existence of oxide phases, which were generated during spraying. A significant change of the extent and type of oxides, when applying an increased flow rate of the atomization gas, cannot be observed. Besides an enhanced coating quality, the use of increased atomization gas pressure exhibited good process stability.

Assessment of swirl spray interaction in lab scale combustor using time-resolved measurements

NASA Astrophysics Data System (ADS)

Rajamanickam, Kuppuraj; Jain, Manish; Basu, Saptarshi

2017-11-01

Liquid fuel injection in highly turbulent swirling flows becomes common practice in gas turbine combustors to improve the flame stabilization. It is well known that the vortex bubble breakdown (VBB) phenomenon in strong swirling jets exhibits complicated flow structures in the spatial domain. In this study, the interaction of hollow cone liquid sheet with such coaxial swirling flow field has been studied experimentally using time-resolved measurements. In particular, much attention is focused towards the near field breakup mechanism (i.e. primary atomization) of liquid sheet. The detailed swirling gas flow field characterization is carried out using time-resolved PIV ( 3.5 kHz). Furthermore, the complicated breakup mechanisms and interaction of the liquid sheet are imaged with the help of high-speed shadow imaging system. Subsequently, proper orthogonal decomposition (POD) and dynamic mode decomposition (DMD) is implemented over the instantaneous data sets to retrieve the modal information associated with the interaction dynamics. This helps to delineate more quantitative nature of interaction process between the liquid sheet and swirling gas phase flow field.

Thermochemical nonequilibrium in atomic hydrogen at elevated temperatures

NASA Technical Reports Server (NTRS)

Scott, R. K.

1972-01-01

A numerical study of the nonequilibrium flow of atomic hydrogen in a cascade arc was performed to obtain insight into the physics of the hydrogen cascade arc. A rigorous mathematical model of the flow problem was formulated, incorporating the important nonequilibrium transport phenomena and atomic processes which occur in atomic hydrogen. Realistic boundary conditions, including consideration of the wall electrostatic sheath phenomenon, were included in the model. The governing equations of the asymptotic region of the cascade arc were obtained by writing conservation of mass and energy equations for the electron subgas, an energy conservation equation for heavy particles and an equation of state. Finite-difference operators for variable grid spacing were applied to the governing equations and the resulting system of strongly coupled, stiff equations were solved numerically by the Newton-Raphson method.

Observing the Interstellar Neutral He Gas Flow with a Variable IBEX Pointing Strategy

NASA Astrophysics Data System (ADS)

Leonard, T.; Moebius, E.; Bzowski, M.; Fuselier, S. A.; Heirtzler, D.; Kubiak, M. A.; Kucharek, H.; Lee, M. A.; McComas, D. J.; Schwadron, N.; Wurz, P.

2015-12-01

The Interstellar Neutral (ISN) gas flow can be observed at Earth's orbit due to the motion of the solar system relative to the surrounding interstellar gas. Since He is minimally influenced by ionization and charge exchange, the ISN He flow provides a sample of the pristine interstellar environment. The Interstellar Boundary Explorer (IBEX) has observed the ISN gas flow over the past 7 years from a highly elliptical orbit around the Earth. IBEX is a Sun-pointing spinning spacecraft with energetic neutral atom (ENA) detectors observing perpendicular to the spacecraft spin axis. Due to the Earth's orbital motion around the Sun, it is necessary for IBEX to perform spin axis pointing maneuvers every few days to maintain a sunward pointed spin axis. The IBEX operations team has successfully pointed the spin axis in a variety of latitude orientations during the mission, including in the ecliptic during the 2012 and 2013 seasons, about 5 degrees below the ecliptic during the 2014 season, and recently about 5 degrees above the ecliptic during the 2015 season, as well as optimizing observations with the spin axis pointed along the Earth-Sun line. These observations include a growing number of measurements near the perihelion of the interstellar atom trajectories, which allow for an improved determination of the ISN He bulk flow longitude at Earth orbit. Combining these bulk flow measurements with an analytical model (Lee et al. 2012 ApJS, 198, 10) based upon orbital mechanics improves the knowledge of the narrow ISN parameter tube, obtained with IBEX, which couples the interstellar inflow longitude, latitude, speed, and temperature.

Highly enhanced electrochemical activity of Ni foam electrodes decorated with nitrogen-doped carbon nanotubes for non-aqueous redox flow batteries

NASA Astrophysics Data System (ADS)

Lee, Jungkuk; Park, Min-Sik; Kim, Ki Jae

2017-02-01

Nitrogen-doped carbon nanotubes (NCNTs) are directly grown on the surface of a three-dimensional (3D) Ni foam substrate by floating catalytic chemical vapor deposition (FCCVD). The electrochemical properties of the 3D NCNT-Ni foam are thoroughly examined as a potential electrode for non-aqueous redox flow batteries (RFBs). During synthesis, nitrogen atoms can be successfully doped onto the carbon nanotube (CNT) lattices by forming an abundance of nitrogen-based functional groups. The 3D NCNT-Ni foam electrode exhibits excellent electrochemical activities toward the redox reactions of [Fe (bpy)3]2+/3+ (in anolyte) and [Co(bpy)3]+/2+ (in catholyte), which are mainly attributed to the hierarchical 3D structure of the NCNT-Ni foam electrode and the catalytic effect of nitrogen atoms doped onto the CNTs; this leads to faster mass transfer and charge transfer during operation. As a result, the RFB cell assembled with 3D NCNT-Ni foam electrodes exhibits a high energy efficiency of 80.4% in the first cycle; this performance is maintained up to the 50th cycle without efficiency loss.

Diagnostic of N2(A) concentration in high velocity nitrogen afterglow at atmospheric pressure

NASA Astrophysics Data System (ADS)

Pointu, Anne-Marie; Mintusov, Evgeny

2009-10-01

An optical emission diagnostic was used to measure N2(A) concentration in a high velocity (1000 cm/s) N2 flowing afterglow of corona discharge at atmospheric pressure, used for biological decontamination. Introducing impurities of NO (<1e-5) we used two well separated and relatively intense lines of NO gamma and beta bands (248nm and 321 nm), easily studied with a low resolution spectrometer. Based on a simplified transport kinetics, the technique is validated using a variation of lines intensity ratios used as coordinates, for numerous experimental points, measured at different axial distances and for different values of NO injected flow. Moreover, it has been demonstrated that N2(A) creation comes from N+N+N2 atom recombination with a global rate around 2e-33 cm^6/s, a result which agrees with literature, as well as N2(A) loss mechanisms were confirmed to go via quenching with O and N atoms. The order of magnitude of obtained N2(A) concentration, about 1e11 cm-3, coincides with the results of direct measurement (by Vegard-Kaplan band), using a spectrometer of better resolution.

Parallel array of nanochannels grafted with polymer-brushes-stabilized Au nanoparticles for flow-through catalysis.

PubMed

Liu, Jianxi; Ma, Shuanhong; Wei, Qiangbing; Jia, Lei; Yu, Bo; Wang, Daoai; Zhou, Feng

2013-12-07

Smart systems on the nanometer scale for continuous flow-through reaction present fascinating advantages in heterogeneous catalysis, in which a parallel array of straight nanochannels offers a platform with high surface area for assembling and stabilizing metallic nanoparticles working as catalysts. Herein we demonstrate a method for finely modifying the nanoporous anodic aluminum oxide (AAO), and further integration of nanoreactors. By using atomic transfer radical polymerization (ATRP), polymer brushes were successfully grafted on the inner wall of the nanochannels of the AAO membrane, followed by exchanging counter ions with a precursor for nanoparticles (NPs), and used as the template for deposition of well-defined Au NPs. The membrane was used as a functional nanochannel for novel flow-through catalysis. High catalytic performance and instantaneous separation of products from the reaction system was achieved in reduction of 4-nitrophenol.

Parallel array of nanochannels grafted with polymer-brushes-stabilized Au nanoparticles for flow-through catalysis

NASA Astrophysics Data System (ADS)

Liu, Jianxi; Ma, Shuanhong; Wei, Qiangbing; Jia, Lei; Yu, Bo; Wang, Daoai; Zhou, Feng

2013-11-01

Smart systems on the nanometer scale for continuous flow-through reaction present fascinating advantages in heterogeneous catalysis, in which a parallel array of straight nanochannels offers a platform with high surface area for assembling and stabilizing metallic nanoparticles working as catalysts. Herein we demonstrate a method for finely modifying the nanoporous anodic aluminum oxide (AAO), and further integration of nanoreactors. By using atomic transfer radical polymerization (ATRP), polymer brushes were successfully grafted on the inner wall of the nanochannels of the AAO membrane, followed by exchanging counter ions with a precursor for nanoparticles (NPs), and used as the template for deposition of well-defined Au NPs. The membrane was used as a functional nanochannel for novel flow-through catalysis. High catalytic performance and instantaneous separation of products from the reaction system was achieved in reduction of 4-nitrophenol.

Flow diagnostics in unseeded air

NASA Technical Reports Server (NTRS)

Miles, R.; Lempert, W.

1990-01-01

Several approaches are presented for the quantitative measurement of flowfield parameters in high-speed flows. The techniques are developed for the study of air flows in the Mach 2 to Mach 3 regime and can be extended to the hypersonic and subsonic regimes in a straightforward manner. Instantaneous two-dimensional cross-sectional images of the density using UV Rayleigh scattering and the measurement of velocity profiles using the RELIEF technique are shown. The RELIEF technique employs two high-powered lasers separated in frequency by the vibrational frequency of oxygen molecules to write lines across the flowfield by stimulated Raman scattering. The preliminary results indicate that the UV Rayleigh scattering may also be extended to the measurement of velocity and temperature fields by using an atomic or molecular absorption filter window, and that the RELIEF technique can be extended to marking shaped volumetric points or arrays of points in the flowfield for velocity and vorticity measurements.

Measured and calculated spectral radiation from a blunt body shock layer in an arc-jet wind tunnel

NASA Technical Reports Server (NTRS)

Babikian, Dikran S.; Palumbo, Giuseppe; Craig, Roger A.; Park, Chul; Palmer, Grant; Sharma, Surendra P.

1994-01-01

Spectra of the shock layer radiation incident on the stagnation point of a blunt body placed in an arc-jet wind tunnel were measured over the wavelength range from 600 nm to 880 nm. The test gas was a mixture of 80 percent air and 20 percent argon by mass, and the run was made in a highly nonequilibrium environment. The observed spectra contained contributions from atomic lines of nitrogen, oxygen, and argon, of bound-free and free-free continua, and band systems of N2 and N2(+). The measured spectra were compared with the synthetic spectra, which were obtained through four steps: the calculation of the arc-heater characteristics, of the nozzle flow, of the blunt-body flow, and the nonequilibrium radiation processes. The results show that the atomic lines are predicted approximately correctly, but all other sources are underpredicted by orders of magnitude. A possible explanation for the discrepancy is presented.

Laser-Induced Fluorescence and Synthetic Jet Fuel Analysis in the Ultra Compact Combustor

DTIC Science & Technology

2009-12-01

In the primary zone, high- temperature, high-pressure air enters from the compressor and flows around fuel injectors spraying atomized liquid -droplet...chemical reaction in which synthesis gas , a mixture of carbon monoxide and hydrogen, is converted into liquid hydrocarbons of various forms. The most...the fuel lines needed to be rebuilt due to a recent COAL lab renovation. The liquid fuel system had not been used for nearly two years so some

Twisted Vanes Would Enhance Fuel/Air Mixing In Turbines

NASA Technical Reports Server (NTRS)

Nguyen, H. Lee; Micklow, Gerald J.; Dogra, Anju S.

1994-01-01

Computations of flow show performance of high-shear airblast fuel injector in gas-turbine engine enhanced by use of appropriately proportioned twisted (instead of flat) dome swirl vanes. Resultant more nearly uniform fuel/air mixture burns more efficiently, emitting smaller amounts of nitrogen oxides. Twisted-vane high-shear airblast injectors also incorporated into paint sprayers, providing advantages of low pressure drop characteristic of airblast injectors in general and finer atomization of advanced twisted-blade design.

Shear-induced partial translational ordering of a colloidal solid

NASA Astrophysics Data System (ADS)

Ackerson, B. J.; Clark, N. A.

1984-08-01

Highly charged submicrometer plastic spheres suspended in water at low ionic strength will order spontaneously into bcc crystals or polycrystals. A simple linear shear orients and disorders these crystals by forcing (110) planes to stack normal to the shear gradient and to slide relative to each other with a <111> direction parallel to the solvent flow. In this paper we analyze in detail the disordering and flow processes occurring beyond the intrinsic elastic limit of the bcc crystal. We are led to a model in which the flow of a colloidal crystal is interpreted as a fundamentally different process from that found in atomic crystals. In the colloidal crystal the coupling of particle motion to the background fluid forces a homogeneous flow, where every layer is in motion relative to its neighboring layers. In contrast, the plastic flow in an atomic solid is defect mediated flow. At the lowest applied stress, the local bcc order in the colloidal crystal exhibits shear strains both parallel and perpendicular to the direction of the applied stress. The magnitude of these deformations is estimated using the configurational energy for bcc and distorted bcc crystals, assuming a screened Coulomb pair interaction between colloidal particles. As the applied stress is increased, the intrinsic elastic limit of the crystal is exceeded and the crystal begins to flow with adjacent layers executing an oscillatory path governed by the balance of viscous and screened Coulomb forces. The path takes the structure from the bcc1 and bcc2 twins observed at zero shear to a distorted two-dimensional hcp structure at moderate shear rates, with a loss of interlayer registration as the shear is increased. This theoretical model is consistent with other experimental observations, as well.

Model calculations of kinetic and fluid dynamic processes in diode pumped alkali lasers

NASA Astrophysics Data System (ADS)

Barmashenko, Boris D.; Rosenwaks, Salman; Waichman, Karol

2013-10-01

Kinetic and fluid dynamic processes in diode pumped alkali lasers (DPALs) are analyzed in detail using a semianalytical model, applicable to both static and flowing-gas devices. The model takes into account effects of temperature rise, excitation of neutral alkali atoms to high lying electronic states and their losses due to ionization and chemical reactions, resulting in a decrease of the pump absorption, slope efficiency and lasing power. Effects of natural convection in static DPALs are also taken into account. The model is applied to Cs DPALs and the results are in good agreement with measurements in a static [B.V. Zhdanov, J. Sell and R.J. Knize, Electron. Lett. 44, 582 (2008)] and 1-kW flowing-gas [A.V. Bogachev et al., Quantum Electron. 42, 95 (2012)] DPALs. It predicts the dependence of power on the flow velocity in flowing-gas DPALs and on the buffer gas composition. The maximum values of the laser power can be substantially increased by optimization of the flowing-gas DPAL parameters. In particular for the aforementioned 1 kW DPAL, 6 kW maximum power is achievable just by increasing the pump power and the temperature of the wall and the gas at the flow inlet (resulting in increase of the alkali saturated vapor density). Dependence of the lasing power on the pump power is non-monotonic: the power first increases, achieves its maximum and then decreases. The decrease of the lasing power with increasing pump power at large values of the latter is due to the rise of the aforementioned losses of the alkali atoms as a result of ionization. Work in progress applying two-dimensional computational fluid dynamics modeling of flowing-gas DPALs is also reported.

Monitoring Temperature in High Enthalpy Arc-heated Plasma Flows using Tunable Diode Laser Absorption Spectroscopy

NASA Technical Reports Server (NTRS)

Martin, Marcel Nations; Chang, Leyen S.; Jeffries, Jay B.; Hanson, Ronald K.; Nawaz, Anuscheh; Taunk, Jaswinder S.; Driver, David M.; Raiche, George

2013-01-01

A tunable diode laser sensor was designed for in situ monitoring of temperature in the arc heater of the NASA Ames IHF arcjet facility (60 MW). An external cavity diode laser was used to generate light at 777.2 nm and laser absorption used to monitor the population of electronically excited oxygen atoms in an air plasma flow. Under the assumption of thermochemical equilibrium, time-resolved temperature measurements were obtained on four lines-of-sight, which enabled evaluation of the temperature uniformity in the plasma column for different arcjet operating conditions.

Dissolution Processes at Step Edges of Calcite in Water Investigated by High-Speed Frequency Modulation Atomic Force Microscopy and Simulation.

PubMed

Miyata, Kazuki; Tracey, John; Miyazawa, Keisuke; Haapasilta, Ville; Spijker, Peter; Kawagoe, Yuta; Foster, Adam S; Tsukamoto, Katsuo; Fukuma, Takeshi

2017-07-12

The microscopic understanding of the crystal growth and dissolution processes have been greatly advanced by the direct imaging of nanoscale step flows by atomic force microscopy (AFM), optical interferometry, and X-ray microscopy. However, one of the most fundamental events that govern their kinetics, namely, atomistic events at the step edges, have not been well understood. In this study, we have developed high-speed frequency modulation AFM (FM-AFM) and enabled true atomic-resolution imaging in liquid at ∼1 s/frame, which is ∼50 times faster than the conventional FM-AFM. With the developed AFM, we have directly imaged subnanometer-scale surface structures around the moving step edges of calcite during its dissolution in water. The obtained images reveal that the transition region with typical width of a few nanometers is formed along the step edges. Building upon insight in previous studies, our simulations suggest that the transition region is most likely to be a Ca(OH) 2 monolayer formed as an intermediate state in the dissolution process. On the basis of this finding, we improve our understanding of the atomistic dissolution model of calcite in water. These results open up a wide range of future applications of the high-speed FM-AFM to the studies on various dynamic processes at solid-liquid interfaces with true atomic resolution.

Monitoring the growth of polyoxomolybdate nanoparticles in suspension by flow field-flow fractionation.

PubMed

Chen, Bailin; Jiang, Huijian; Zhu, Yan; Cammers, Arthur; Selegue, John P

2005-03-30

We follow the evolution of polyoxomolybdate nanoparticles in suspensions derived from the keplerate (NH4)42[MoVI72MoV60O372(CH3CO2)30(H2O)72].ca..300H2O.ca..10CH3CO2NH4 ({Mo132}) by flow field-flow fractionation (FlFFF) to monitor the particle-size distribution in situ, atomic force and high-resolution transmission electron microscopy (AFM, SEM, and HRTEM) to confirm particle sizes, inductively coupled plasma-optical emission spectrometry (ICP-OES) to determine the Mo content of the FlFFF-separated fractions, and UV/visible spectroscopy to confirm the identity of the species in suspension. We observe the formation of 3-75-nm polyoxomolybdate particles in suspension and the dynamic growth of {Mo132} crystals.

Effect of vane twist on the performance of dome swirlers for gas turbine airblast atomizers

NASA Technical Reports Server (NTRS)

Micklow, Gerald J.; Dogra, Anju S.; Nguyen, H. Lee

1990-01-01

For advanced gas turbine engines, two combustor systems, the lean premixed/prevaporized (LPP) and the rich burn/quick quench/lean burn (RQL) offer great potential for reducing NO(x) emissions. An important consideration for either concept is the development of an advanced fuel injection system that will provide a stable, efficient, and very uniform combustion system over a wide operating range. High-shear airblast fuel injectors for gas turbine combustors have exhibited superior atomization and mixing compared with pressure-atomizing fuel injectors. This improved mixing has lowered NO(x) emissions and the pattern factor, and has enabled combustors to alternate fuels while maintaining a stable, efficient combustion system. The performance of high-shear airblast fuel injectors is highly dependent on the design of the dome swirl vanes. The type of swirl vanes most widely used in gas turbine combustors are usually flat for ease of manufacture, but vanes with curvature will, in general, give superior aerodynamic performance. The design and performance of high-turning, low-loss curved dome swirl vanes with twist along the span are investigated. The twist induces a secondary vortex flow pattern which will improve the atomization of the fuel, thereby producing a more uniform fuel-air distribution. This uniform distribution will increase combustion efficiency while lowering NO(x) emissions. A systematic swirl vane design system is presented based on one-, two-, and three-dimensional flowfield calculations, with variations in vane-turning angle, rate of turning, vane solidity, and vane twist as design parameters.

Effect of vane twist on the performance of dome swirlers for gas turbine airblast atomizers

NASA Astrophysics Data System (ADS)

Micklow, Gerald J.; Dogra, Anju S.; Nguyen, H. Lee

1990-07-01

For advanced gas turbine engines, two combustor systems, the lean premixed/prevaporized (LPP) and the rich burn/quick quench/lean burn (RQL) offer great potential for reducing NO(x) emissions. An important consideration for either concept is the development of an advanced fuel injection system that will provide a stable, efficient, and very uniform combustion system over a wide operating range. High-shear airblast fuel injectors for gas turbine combustors have exhibited superior atomization and mixing compared with pressure-atomizing fuel injectors. This improved mixing has lowered NO(x) emissions and the pattern factor, and has enabled combustors to alternate fuels while maintaining a stable, efficient combustion system. The performance of high-shear airblast fuel injectors is highly dependent on the design of the dome swirl vanes. The type of swirl vanes most widely used in gas turbine combustors are usually flat for ease of manufacture, but vanes with curvature will, in general, give superior aerodynamic performance. The design and performance of high-turning, low-loss curved dome swirl vanes with twist along the span are investigated. The twist induces a secondary vortex flow pattern which will improve the atomization of the fuel, thereby producing a more uniform fuel-air distribution. This uniform distribution will increase combustion efficiency while lowering NO(x) emissions. A systematic swirl vane design system is presented based on one-, two-, and three-dimensional flowfield calculations, with variations in vane-turning angle, rate of turning, vane solidity, and vane twist as design parameters.

Effect of vane twist on the performance of dome swirlers for gas turbine airblast atomizers

NASA Astrophysics Data System (ADS)

Micklow, Gerald J.; Dogra, Anju S.; Nguyen, H. Lee

1990-06-01

For advanced gas turbine engines, two combustor systems, the lean premixed/prevaporized (LPP) and the rich burn/quick quench/lean burn (RQL) offer great potential for reducing NO(x) emissions. An important consideration for either concept is the development of an advanced fuel injection system that will provide a stable, efficient, and very uniform combustion system over a wide operating range. High-shear airblast fuel injectors for gas turbine combustors have exhibited superior atomization and mixing compared with pressure-atomizing fuel injectors. This improved mixing has lowered NO(x) emissions and the pattern factor, and has enabled combustors to alternate fuels while maintaining a stable, efficient combustion system. The performance of high-shear airblast fuel injectors is highly dependent on the design of the dome swirl vanes. The type of swirl vanes most widely used in gas turbine combustors are usually flat for ease of manufacture, but vanes with curvature will, in general, give superior aerodynamic performance. The design and performance of high-turning, low-loss curved dome swirl vanes with twist along the span are investigated. The twist induces a secondary vortex flow pattern which will improve the atomization of the fuel, thereby producing a more uniform fuel-air distribution. This uniform distribution will increase combustion efficiency while lowering NO(x) emissions. A systematic swirl vane design system is presented based on one-, two-, and three-dimensional flowfield calculations, with variations in vane-turning angle, rate of turning, vane solidity, and vane twist as design parameters.

Temperature Measurements of High-Z Plasma Exiting the Laser Entrance Hole of Ignition Scale Depleted Uranium Hohlraums

NASA Astrophysics Data System (ADS)

Parrilla, Nicholas; Ralph, Joe; Bachmann, Ben; Goyon, Clement; Dewald, Eduard

2017-10-01

The temperature profile from the Laser Entrance Hole to 3.5 mm from the exit point was measured for plasma with high atomic number (high-Z) of Depleted Uranium ignition scale hohlraums. Each hohlraum was filled with 0.6 mg/cc He as part of the high foot CH campaign. Temperature of the flowing plasma is measured by fitting the velocity distribution to a Maxwellian and considering the Planckian spectral distributions with and without a 42 um Ge filter. The two spectra are then compared to determine the temperature of the high-Z plasma.

Experimental spray atomization studies of uni-element shear coaxial injector plate geometry for LOX/CH4 combustion and propulsion research

NASA Astrophysics Data System (ADS)

Dorado, Vanessa

The Center for Space Exploration Technology Research (cSETR) has developed a set of shear coaxial injectors as part of a system-level approach to study LOX/CH4 combustion. This thesis describes the experimental studies involved in the characterization of the effects produced by two design injection face plate variables: post thickness and recession length. A testing program was developed to study the injectors' atomization process using LN2 as a substitute for LOX in cold flow and the flame anchoring mechanisms in hot firings. The cold flow testing stage was conducted to obtain liquid core measurements and compare its behavior between the different geometric configurations. Shadowgraph technique was used during this testing stage to obtain these measurements and compare them to previously published data and core length mathematical models. The inlet conditions were selected to obtain mixture ratios in the 2-4 range and a wide range of high momentum flux ratios (30-150). Particle Image Velocimetry (PIV) was also used in the testing of the three injectors to assess their atomization performance and their fragmentation behaviors. Results show that changes in central post thickness and co-annular orifice recession length with respect to the injection plate have quantifiable effects in the generated spray flow field, despite not being accounted for in traditional break up calculations. The observations and results of this investigation lead to a proof of concept demonstration in a combustion setting to support the study of flame anchoring mechanisms, also discussed in this work.

Efficient Nonlinear Atomization Model for Thin 3D Free Liquid Films

NASA Astrophysics Data System (ADS)

Mehring, Carsten

2007-03-01

Reviewed is a nonlinear reduced-dimension thin-film model developed by the author and aimed at the prediction of spray formation from thin films such as those found in gas-turbine engines (e.g., prefilming air-blast atomizers), heavy-fuel-oil burners (e.g., rotary-cup atomizers) and in the paint industry (e.g., flat-fan atomizers). Various implementations of the model focusing on different model-aspects, i.e., effect of film geometry, surface tension, liquid viscosity, coupling with surrounding gas-phase flow, influence of long-range intermolecular forces during film rupture are reviewed together with a validation of the nonlinear wave propagation characteristics predicted by the model for inviscid planar films using a two-dimensional vortex- method. An extension and generalization of the current nonlinear film model for implementation into a commercial flow- solver is outlined.

A comprehensive Two-Fluid Model for Cavitation and Primary Atomization Modelling of liquid jets - Application to a large marine Diesel injector

NASA Astrophysics Data System (ADS)

Habchi, Chawki; Bohbot, Julien; Schmid, Andreas; Herrmann, Kai

2015-12-01

In this paper, a comprehensive two-fluid model is suggested in order to compute the in-nozzle cavitating flow and the primary atomization of liquid jets, simultaneously. This model has been applied to the computation of a typical large marine Diesel injector. The numerical results have shown a strong correlation between the in-nozzle cavitating flow and the ensuing spray orientation and atomization. Indeed, the results have confirmed the existence of an off-axis liquid core. This asymmetry is likely to be at the origin of the spray deviation observed experimentally. In addition, the primary atomization begins very close to the orifice exit as in the experiments, and the smallest droplets are generated due to cavitation pocket shape oscillations located at the same side, inside the orifice.

An experimental study of combustion of the Shen-Mu CWS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lifang, C.; Zhan Huanqing; Sun Wenchao

1993-12-31

Self-stabilized combustion for Shen-Mu CWS is provided by a combustion facility with outstanding characteristics. Experimental results show that the Shen-Mu CWS of about 65% concentrations possesses still a good flow property and it is easy to atomize. The atomized particles were measured by use of a Malvern setup. The Sauter mean diameters of the slurry spray are 56 {mu}m, while the air/fuel mass ratio is 0.21. It gives the evidence that the atomizer has excellent atomization performance. Self-stabilized combustion is preserved under the condition of unpreheated air and no say addition of auxiliary fuel is required. Experimental study of combustionmore » was carried out in the combustion chambers of 360mm {times} 540mm {times} 1400mm, the rates of CWS flow were 320kg/h.« less

Modeling of flowing gas diode pumped alkali lasers: dependence of the operation on the gas velocity and on the nature of the buffer gas.

PubMed

Barmashenko, B D; Rosenwaks, S

2012-09-01

A simple, semi-analytical model of flowing gas diode pumped alkali lasers (DPALs) is presented. The model takes into account the rise of temperature in the lasing medium with increasing pump power, resulting in decreasing pump absorption and slope efficiency. The model predicts the dependence of power on the flow velocity in flowing gas DPALs and checks the effect of using a buffer gas with high molar heat capacity and large relaxation rate constant between the 2P3/2 and 2P1/2 fine-structure levels of the alkali atom. It is found that the power strongly increases with flow velocity and that by replacing, e.g., ethane by propane as a buffer gas the power may be further increased by up to 30%. Eight kilowatt is achievable for 20 kW pump at flow velocity of 20  m/s.

Arc Jet Flow Properties Determined from Laser-Induced Fluorescence of Atomic Nitrogen

NASA Technical Reports Server (NTRS)

Fletcher, Douglas; Wercinski, Paul F. (Technical Monitor)

1998-01-01

An laser-spectroscopic investigation of the thermocheMical state of arcjet flows is currently being conducted in the Aerodynamic Heating Facility (AHF) Circlet at NASA Ames Research Center. Downstream of the nozzle exit, but upstream of the test article, Laser-Induced Fluorescence (LIF) of atomic nitrogen is used to assess the nonequilibriuM distribution of flow enthalpy in the free stream. The two-photon LIF technique provides simultaneous measurements of free stream velocity, translational temperature, and nitrogen number density on the flow centerline. Along with information from facility instrumentation, these measurements allow a determination of the free stream total enthalpy, and its apportionment in to thermal, kinetic, and chemical mode contributions. Experimental results are presented and discussed for two different niti-ogen/argon test gas flow runs during which the current is varied while the pressure remains constant .

Monte Carlo Approach for Estimating Density and Atomic Number From Dual-Energy Computed Tomography Images of Carbonate Rocks

NASA Astrophysics Data System (ADS)

Victor, Rodolfo A.; Prodanović, Maša.; Torres-Verdín, Carlos

2017-12-01

We develop a new Monte Carlo-based inversion method for estimating electron density and effective atomic number from 3-D dual-energy computed tomography (CT) core scans. The method accounts for uncertainties in X-ray attenuation coefficients resulting from the polychromatic nature of X-ray beam sources of medical and industrial scanners, in addition to delivering uncertainty estimates of inversion products. Estimation of electron density and effective atomic number from CT core scans enables direct deterministic or statistical correlations with salient rock properties for improved petrophysical evaluation; this condition is specifically important in media such as vuggy carbonates where CT resolution better captures core heterogeneity that dominates fluid flow properties. Verification tests of the inversion method performed on a set of highly heterogeneous carbonate cores yield very good agreement with in situ borehole measurements of density and photoelectric factor.

Dynamic Tunneling Junctions at the Atomic Intersection of Two Twisted Graphene Edges.

PubMed

Bellunato, Amedeo; Vrbica, Sasha D; Sabater, Carlos; de Vos, Erik W; Fermin, Remko; Kanneworff, Kirsten N; Galli, Federica; van Ruitenbeek, Jan M; Schneider, Grégory F

2018-04-11

The investigation of the transport properties of single molecules by flowing tunneling currents across extremely narrow gaps is relevant for challenges as diverse as the development of molecular electronics and sequencing of DNA. The achievement of well-defined electrode architectures remains a technical challenge, especially due to the necessity of high precision fabrication processes and the chemical instability of most bulk metals. Here, we illustrate a continuously adjustable tunneling junction between the edges of two twisted graphene sheets. The unique property of the graphene electrodes is that the sheets are rigidly supported all the way to the atomic edge. By analyzing the tunneling current characteristics, we also demonstrate that the spacing across the gap junction can be controllably adjusted. Finally, we demonstrate the transition from the tunneling regime to contact and the formation of an atomic-sized junction between the two edges of graphene.

Dynamic Tunneling Junctions at the Atomic Intersection of Two Twisted Graphene Edges

PubMed Central

2018-01-01

The investigation of the transport properties of single molecules by flowing tunneling currents across extremely narrow gaps is relevant for challenges as diverse as the development of molecular electronics and sequencing of DNA. The achievement of well-defined electrode architectures remains a technical challenge, especially due to the necessity of high precision fabrication processes and the chemical instability of most bulk metals. Here, we illustrate a continuously adjustable tunneling junction between the edges of two twisted graphene sheets. The unique property of the graphene electrodes is that the sheets are rigidly supported all the way to the atomic edge. By analyzing the tunneling current characteristics, we also demonstrate that the spacing across the gap junction can be controllably adjusted. Finally, we demonstrate the transition from the tunneling regime to contact and the formation of an atomic-sized junction between the two edges of graphene. PMID:29513997

LOX/Hydrogen Coaxial Injector Atomization Test Program

NASA Technical Reports Server (NTRS)

Zaller, M.

1990-01-01

Quantitative information about the atomization of injector sprays is needed to improve the accuracy of computational models that predict the performance and stability margin of liquid propellant rocket engines. To obtain this data, a facility for the study of spray atomization is being established at NASA-Lewis to determine the drop size and velocity distributions occurring in vaporizing liquid sprays at supercritical pressures. Hardware configuration and test conditions are selected to make the cold flow simulant testing correspond as closely as possible to conditions in liquid oxygen (LOX)/gaseous H2 rocket engines. Drop size correlations from the literature, developed for liquid/gas coaxial injector geometries, are used to make drop size predictions for LOX/H2 coaxial injectors. The mean drop size predictions for a single element coaxial injector range from 0.1 to 2000 microns, emphasizing the need for additional studies of the atomization process in LOX/H2 engines. Selection of cold flow simulants, measured techniques, and hardware for LOX/H2 atomization simulations are discussed.

Laser photochemical lead isotopes separation for harmless nuclear power engineering

NASA Astrophysics Data System (ADS)

Bokhan, P. A.; Fateev, N. V.; Kim, V. A.; Zakrevsky, D. E.

2016-09-01

The collisional quenching of the metastable 3 P 1,2 and 1 D 2 lead atoms is studied experimentally in the gas flow of the lead atoms, reagent-molecules and a carrier gas Ar. The experimental parameters were similar to the conditions that are required in the operation of the experimental setup for photochemical isotope separation. Excited atoms are generated under electron impact conditions created by a gas glow discharge through the mixture of gases and monitored photoelectrically by attenuation of atomic resonance radiation from hollow cathode 208Pb lamp. The decay of the excited atoms has been studied in the presence various molecules and total cross section data are reported. The flow tube measurements has allowed to separate the physical and chemical quenching channels and measure the rates of the chemical reaction excited lead with N2O, CH2Cl2, SF6 and CuBr molecules. These results are discussed in the prospects of the obtaining isotopically modified lead as a promising coolant in the reactors on the fast-neutron.

IBEX-lo Sky Maps of Secondary Interstellar Neutrals Helium and Oxygen

NASA Astrophysics Data System (ADS)

Kucharek, H.; Isenberg, P. A.; Jeewoo, P.; Kubiak, M. A.; Bzowski, M.

2017-12-01

There are several populations of heliospheric energetic neutral atoms (ENAs) generated at the various heliospheric interfaces, the inner heliosheath, outer heliosheath (OHS), and the termination shock (TS). Depending on where and how these ENAs are generated, they belong to different energy regimes. While interstellar neutral (ISN) particles flow through the heliospheric boundary is mostly unimpeded, a substantial fraction of ISN H and O is filtered through charge exchange with ambient plasma ions before reaching the TS. Secondary ISN atoms are generated by the charge exchange reaction between primary ISN atoms and interstellar ions in the outer heliosheath, forming walls of H and O in front of the heliopause (HP). The flowing interstellar plasma encounters the heliopause as an obstacle, which deflects the flow. Thus, secondary neutrals measured at 1 AU carry information about the deflected interstellar plasma and the shape of the heliopause that causes the deflection. Due to very different magnitudes of charge exchange cross sections, the main source of the secondary He is charge exchange with the OHS He+, while that of the secondary O is the charge exchange between interstellar O+ and the OHS H. Therefore, the oxygen results are drastically different from those of helium. Interstellar O+ ions behave in principle like the He+ particles with an over-density due to the plasma deceleration. The high density decelerated oxygen ions just upwind of the heliopause encounter an over-density in neutral hydrogen, the hydrogen wall, allowing frequent charge exchange that produce slow neutral oxygen atoms forming the oxygen wall. Thus, the distribution in the sky maps of secondary He and O carries information on the shape as well as the structures in front of it. To investigate the secondary component of the interstellar neutral in detail we have distinguish between the two secondary component's. We engaged theory and simulations for the primary and secondary components to determine differences of between measurements and model predicted data.

An introduction to mass cytometry: fundamentals and applications.

PubMed

Tanner, Scott D; Baranov, Vladimir I; Ornatsky, Olga I; Bandura, Dmitry R; George, Thaddeus C

2013-05-01

Mass cytometry addresses the analytical challenges of polychromatic flow cytometry by using metal atoms as tags rather than fluorophores and atomic mass spectrometry as the detector rather than photon optics. The many available enriched stable isotopes of the transition elements can provide up to 100 distinguishable reporting tags, which can be measured simultaneously because of the essential independence of detection provided by the mass spectrometer. We discuss the adaptation of traditional inductively coupled plasma mass spectrometry to cytometry applications. We focus on the generation of cytometry-compatible data and on approaches to unsupervised multivariate clustering analysis. Finally, we provide a high-level review of some recent benchmark reports that highlight the potential for massively multi-parameter mass cytometry.

Solid-phase extraction and separation procedure for trace aluminum in water samples and its determination by high-resolution continuum source flame atomic absorption spectrometry (HR-CS FAAS).

PubMed

Ciftci, Harun; Er, Cigdem

2013-03-01

In the present study, a separation/preconcentration procedure for determination of aluminum in water samples has been developed by using a new atomic absorption spectrometer concept with a high-intensity xenon short-arc lamp as continuum radiation source, a high-resolution double-echelle monochromator, and a charge-coupled device array detector. Sample solution pH, sample volume, flow rate of sample solution, volume, and concentration of eluent for solid-phase extraction of Al chelates with 4-[(dicyanomethyl)diazenyl] benzoic acid on polymeric resin (Duolite XAD-761) have been investigated. The adsorbed aluminum on resin was eluted with 5 mL of 2 mol L(-1) HNO(3) and its concentration was determined by high-resolution continuum source flame atomic absorption spectrometry (HR-CS FAAS). Under the optimal conditions, limit of detection obtained with HR-CS FAAS and Line Source FAAS (LS-FAAS) were 0.49 μg L(-1) and 3.91 μg L(-1), respectively. The accuracy of the procedure was confirmed by analyzing certified materials (NIST SRM 1643e, Trace elements in water) and spiked real samples. The developed procedure was successfully applied to water samples.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Atutov, S. N., E-mail: atutovsn@mail.ru; Plekhanov, A. I.

We present the results of a systematic study of Knudsen’s flow of Rb atoms in cylindrical capillary cells coated with a polydimethylsiloxane (PDMS) compound. The purpose of the investigation is to determine the characterization of the coating in terms of the sticking probability and sticking time of Rb on the two types of coating of high and medium viscosities. We report the measurement of the sticking probability of a Rb atom to the coating equal to 4.3 × 10{sup −5}, which corresponds to the number of bounces 2.3 × 10{sup 4} at room temperature. These parameters are the same formore » the two kinds of PDMS used. We find that at room temperature, the respective sticking times for high-viscosity and medium-viscosity PDMS are 22 ± 3 μs and 49 ± 6 μs. These sticking times are about million times larger than the sticking time derived from the surface Rb atom adsorption energy and temperature of the coating. A tentative explanation of this surprising result is proposed based on the bulk diffusion of the atoms that collide with the surface and penetrate inside the coating. The results can be important in many resonance cell experiments, such as the efficient magnetooptical trapping of rare elements or radioactive isotopes and in experiments on the light-induced drift effect.« less

The structure and properties of a nickel-base superalloy produced by osprey atomization-deposition

NASA Astrophysics Data System (ADS)

Bricknell, Rodger H.

1986-04-01

The production of a nickel-base superalloy, René* 80, by the Osprey atomization-deposition process has been investigated. Dense (>99 pct) material with a fine-grained equiaxed microstructure was deposited using either argon or nitrogen as the atomizing gas. Defects present in the material included a chill region at the collector plate interface, entrapped recirculated particles, porosity, and ceramic particles from the melting and dispensing system. In contrast to other rapid solidification techniques, low oxygen pick-ups are noted in the current technique. Tensile strengths above those displayed by castings are found in both nitrogen and argon atomized material, and in both the as-deposited and heat treated conditions. In addition, no profound mid-temperature ductility loss is displayed by this low oxygen material, in contrast to results on other rapidly solidified material with high oxygen contents. These results are explained in terms of oxygen embrittlement. In view of the excellent properties measured, the attractive economics of the process, and the fact that fine control of the gas/metal flow ratio is shown to be unnecessary, it is concluded that atomization-deposition presents an attractive potential production route for advanced alloys.

Arcjet Flow Properties Determined from Laser-Induced Fluorescence of Atomic Species

NASA Technical Reports Server (NTRS)

Fletcher, Douglas G.

1997-01-01

Flow property measurements that were recently acquired in the Ames Research Center Aerodynamic Heating Facility (AHF) arc jet using two-photon Laser-Induced Fluorescence (LIF) of atomic nitrogen and oxygen are reported. The measured properties, which include velocity, translational temperature, and species concentration, cover a wide range of facility operation for the 30 cm nozzle. During the tests, the arc jet pressure and input stream composition were maintained at fixed values and the arc current was varied to vary the flow enthalpy. As part of this ongoing effort, a measurement of the two-photon absorption coefficient for the 3p4D<-2p4S transition of atomic nitrogen was performed, and the measured value is used to convert the relative concentration measurements to absolute values. A flow reactor is used to provide a known temperature line shape profile to deconvolve the laser line width contribution to the translational temperature measurements. Results from the current experiments are compared with previous results obtained using NO-Beta line profiles at room temperature and the problem of multimode laser oscillation and its impact on the two-photon excitation line shape are discussed. One figure is attached, and this figure shows relative N atom concentration measurements as a function of the arc power. Other measurements have already been acquired and analyzed. This poster represents an application of laser-spectroscopic measurements in an important test facility. The arc jet flow facilities are heavily used in thermal protection material development and evaluation. All hypersonic flight and planetary atmospheric entry vehicles will use materials tested in these arc jet facilities.

Focused Schlieren flow visualization studies of multiple venturi fuel injectors in a high pressure combustor

NASA Technical Reports Server (NTRS)

Chun, K. S.; Locke, R. J.; Lee, C. M.; Ratvasky, W. J.

1994-01-01

Multiple venturi fuel injectors were used to obtain uniform fuel distributions, better atomization and vaporization in the premixing/prevaporizing section of a lean premixed/prevaporized flame tube combustor. A focused Schlieren system was used to investigate the fuel/air mixing effectiveness of various fuel injection configurations. The Schlieren system was focused to a plane within the flow field of a test section equipped with optical windows. The focused image plane was parallel to the axial direction of the flow and normal to the optical axis. Images from that focused plane, formed by refracted light due to density gradients within the flow field, were filmed with a high-speed movie camera at framing rates of 8,000 frames per second (fps). Three fuel injection concepts were investigated by taking high-speed movies of the mixture flows at various operating conditions. The inlet air temperature was varied from 600 F to 1000 F, and inlet pressures from 80 psia to 150 psia. Jet-A fuel was used typically at an equivalence ratio of 0.5. The intensity variations of the digitized Schlieren images were analytically correlated to spatial density gradients of the mixture flows. Qualitative measurements for degree of mixedness, intensity of mixing, and mixing completion time are shown. Various mixing performance patterns are presented with different configurations of fuel injection points and operating conditions.

Velocity measurements in the near field of a diesel fuel injector by ultrafast imagery

NASA Astrophysics Data System (ADS)

Sedarsky, David; Idlahcen, Saïd; Rozé, Claude; Blaisot, Jean-Bernard

2013-02-01

This paper examines the velocity profile of fuel issuing from a high-pressure single-orifice diesel injector. Velocities of liquid structures were determined from time-resolved ultrafast shadow images, formed by an amplified two-pulse laser source coupled to a double-frame camera. A statistical analysis of the data over many injection events was undertaken to map velocities related to spray formation near the nozzle outlet as a function of time after start of injection. These results reveal a strong asymmetry in the liquid profile of the test injector, with distinct fast and slow regions on opposite sides of the orifice. Differences of ˜100 m/s can be observed between the `fast' and `slow' sides of the jet, resulting in different atomization conditions across the spray. On average, droplets are dispersed at a greater distance from the nozzle on the `fast' side of the flow, and distinct macrostructure can be observed under the asymmetric velocity conditions. The changes in structural velocity and atomization behavior resemble flow structures which are often observed in the presence of string cavitation produced under controlled conditions in scaled, transparent test nozzles. These observations suggest that widely used common-rail supply configurations and modern injectors can potentially generate asymmetric interior flows which strongly influence diesel spray morphology. The velocimetry measurements presented in this work represent an effective and relatively straightforward approach to identify deviant flow behavior in real diesel sprays, providing new spatially resolved information on fluid structure and flow characteristics within the shear layers on the jet periphery.

The influence of cavitation in the breakup of liquid free jets

NASA Astrophysics Data System (ADS)

Bode, Juergen

1991-03-01

The interaction between a diesel injection nozzle flow and the atomizing jet was investigated over a wide range of Reynolds numbers. If the pressure gradient towards the centerline of the injection nozzle, generated by the curved streamlines, becomes too large, cavitation occurs at the inlet corner. The cavitation region grows in length and boundary surface with increasing Reynolds number. The instability of the reentry flow causes unsteady fluctuations of the cavitation which influences the breakup of the liquid jet, whereby liquid films are generated which take off from the jet. Cavitation amplifies the mechanism of the atomization, based on the interaction between the jet and surrounding gas. The influence of the cavitation on the atomization is restricted to the region directly behind the nozzle exit. The injection pressure and the temperature of the gas hardly affect the atomization. The jet angle depends mainly on the density of the surrounding gas.

Atomic Physics Effects on Convergent, Child-Langmuir Ion Flow between Nearly Transparent Electrodes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Santarius, John F.; Emmert, Gilbert A.

Research during this project at the University of Wisconsin Fusion Technology Institute (UW FTI) on ion and neutral flow through an arbitrary, monotonic potential difference created by nearly transparent electrodes accomplished the following: (1) developed and implemented an integral equation approach for atomic physics effects in helium plasmas; (2) extended the analysis to coupled integral equations that treat atomic and molecular deuterium ions and neutrals; (3) implemented the key deuterium and helium atomic and molecular cross sections; (4) added negative ion production and related cross sections; and (5) benchmarked the code against experimental results. The analysis and codes treat themore » species D0, D20, D+, D2+, D3+, D and, separately at present, He0 and He+. Extensions enhanced the analysis and related computer codes to include He++ ions plus planar and cylindrical geometries.« less

Superior visible light hydrogen evolution of Janus bilayer junctions via atomic-level charge flow steering

NASA Astrophysics Data System (ADS)

Li, Jie; Zhan, Guangming; Yu, Ying; Zhang, Lizhi

2016-05-01

Although photocatalytic hydrogen evolution (PHE) is ideal for solar-to-fuel conversion, it remains challenging to construct a highly efficient PHE system by steering the charge flow in a precise manner. Here we tackle this challenge by assembling 1T MoS2 monolayers selectively and chemically onto (Bi12O17) end-faces of Bi12O17Cl2 monolayers to craft two-dimensional (2D) Janus (Cl2)-(Bi12O17)-(MoS2) bilayer junctions, a new 2D motif different from van der Waals heterostructure. Electrons and holes from visible light-irradiated Bi12O17Cl2 are directionally separated by the internal electric field to (Bi12O17) and (Cl2) end-faces, respectively. The separated electrons can further migrate to MoS2 via Bi-S bonds formed between (Bi12O17) and MoS2 monolayers. This atomic-level directional charge separation endows the Janus bilayers with ultralong carrier lifetime of 3,446 ns and hence a superior visible-light PHE rate of 33 mmol h-1 g-1. Our delineated Janus bilayer junctions on the basis of the oriented assembly of monolayers presents a new design concept to effectively steer the charge flow for PHE.

A benchmark of co-flow and cyclic deposition/etch approaches for the selective epitaxial growth of tensile-strained Si:P

NASA Astrophysics Data System (ADS)

Hartmann, J. M.; Veillerot, M.; Prévitali, B.

2017-10-01

We have compared co-flow and cyclic deposition/etch processes for the selective epitaxial growth of Si:P layers. High growth rates, relatively low resistivities and significant amounts of tensile strain (up to 10 nm min-1, 0.55 mOhm cm and a strain equivalent to 1.06% of substitutional C in Si:C layers) were obtained at 700 °C, 760 Torr with a co-flow approach and a SiH2Cl2 + PH3 + HCl chemistry. This approach was successfully used to thicken the sources and drains regions of n-type fin-shaped Field Effect Transistors. Meanwhile, the (Si2H6 + PH3/HCl + GeH4) CDE process evaluated yielded at 600 °C, 80 Torr even lower resistivities (0.4 mOhm cm, typically), at the cost however of the tensile strain which was lost due to (i) the incorporation of Ge atoms (1.5%, typically) into the lattice during the selective etch steps and (ii) a reduction by a factor of two of the P atomic concentration in CDE layers compared to that in layers grown in a single step (5 × 1020 cm-3 compared to 1021 cm-3).

Atomic oxygen reactor having at least one sidearm conduit

NASA Technical Reports Server (NTRS)

Koontz, Steven L. (Inventor)

1994-01-01

An apparatus for treating a microporous structure with atomic oxygen is presented. The apparatus includes a main gas chamber for flowing gas in an axial direction and a source of gas, containing atomic oxygen, connected for introducing the gas into the main gas chamber. The apparatus employs at least one side arm extending from the main atomic oxygen-containing chamber. The side arm has characteristic relaxation times such that a uniform atomic oxygen dose rate is delivered to a specimen positioned transversely in the side arm spaced from the main gas chamber.

Coupling modes between liquid/gas coaxial jets and transverse acoustic waves

NASA Astrophysics Data System (ADS)

Helland, Chad; Hilliker, Cullen; Forliti, David; University of St. Thomas Team

2017-11-01

The interactions between shear flows and acoustic disturbances plays a very important role in many propulsion and energy applications. Liquid jets, either independent or air assisted, respond to acoustic disturbances in a manner that alters the primary and secondary atomization processes. The current study focused on the response of an air-assisted liquid jet to disturbances associated with a transverse acoustic wave. The jet is placed in the pressure node (velocity antinode) region of the resonant mode shape. It has been shown in previous studies, under certain conditions, that the acoustic forces can cause the jet flow to distort and atomize. Both liquid and coaxial gas/ liquid jet flows have been shown to distort via acoustic forces. The purpose of the current study is to understand the predictive characteristics that cause the distortion behaviors of a liquid and coaxial jet flow, and how a how a coaxial flow affects the behavior.

Spray measurements of aerothermodynamic effect on disintegrating liquid jets

NASA Technical Reports Server (NTRS)

Ingebo, Robert D.

1991-01-01

An experimental investigation was made to determine the effect of atomizing gas mass flux and temperature on liquid jet breakup in sonic velocity gas flow. Characteristic drop size data were obtained by using the following atomizing gases: nitrogen, argon, and helium to breakup water jets in high velocity gas flow. A scattered light scanning instrument developed at Lewis Research Center was used to measure Sauter mean diameter (SMD). The three gases gave a molecular weight range of 4 to 40 and atomizing gas mass flux and temperature were varied from 6 to 50 g/sq cm and 275-400 K, respectively. The ratio of liquid jet diameter to SMD, D(sub 0)/D(sub 32), was correlated with aerodynamic and liquid-surface force ratios, i.e., the product of the Weber and Reynolds number, We Re, the gas to liquid density ratio, rho(sub g)/rho(sub 1) g and also the molecular scale dimensionless group, rho(sub 1)(Vm exp 3)/ mu(sub 1) g, to give the following expression: D(sub 0)/D(sub 32) = 0.90 x 10(exp -8) x (We Re rho sub g/rho sub 1)exp 0.44 x (rho sub 1 Vm exp 3/mu sub 1 g)exp 0.67 where We Re = ((rho sub g)exp 2(D sub 0)exp 2(V sub C)exp3))/ mu sub 1 sigma, mu sub 1 is liquid viscosity, sigma is surface tension, V sub C is the acoustic gas velocity, V sub m is the RMS velocity of gas molecules, and g is the acceleration of gas molecules due to gravity. Good agreement was obtained with atomization theory for liquid-jet breakup in the regime of aerodynamic stripping. Also, due to its low molecular weight and high acoustic velocity, helium was considerably more effective than nitrogen or argon in producing small-droplet sprays with values of D(sub 32) on the order of 5 microns.

Effect of N2 flow during deposition on p-type ZnO film

NASA Astrophysics Data System (ADS)

Lin, Chiung-Wei; Liu, Bor-Chang

2017-01-01

In this study, the influence of a nitrogen source on p-type conductive ZnO films was studied. Rapid thermal oxidation was conducted to oxidize ZnN films and convert them to ZnO films. When an as-deposited ZnN film was prepared at a high nitrogen gas flow rate, the converted ZnO film possessed many acceptors and showed stable p-type conduction. This p-type conduction was attributed to the nitrogen gas flow providing many “No” states, which act as acceptors within the processed ZnO film. It was found that the as-deposited ZnN film prepared at a high nitrogen gas flow rate is oxidized slightly so that only a few nitrogen atoms were replaced by oxygen. The carrier concentration and mobility of the optimized oxidized ZnN film were 9.76 × 1017 cm-3 and 62.78 cm2 V-1 s-1, respectively. A good rectified current-voltage characteristic with a turn-on voltage of 3.65 V was achieved for the optimized ZnO:N/ZnO junction.

[Determination of mercury in Boletus impolitus by flow injection-atomic absorption spectrometry].

PubMed

Li, Tao; Wang, Yuan-Zhong

2008-04-01

Various test conditions and effect factors for the determination of mercury by flow injection-atomic absorption spectrometry were discussed, and a method for the determination of mercury in Boletus impolitus has been developed. The linear range for mercury is 0-60 microg x L(-1). The relative standard deviation is less than 3.0%, and the recovery is 96%-107%. This method is simple, rapid and has been applied to the determination of mercury in Boletus impolitus samples with satisfactory results.

A numerical study on liquid charging inside electrostatic atomizers

NASA Astrophysics Data System (ADS)

Kashir, Babak; Perri, Anthony; Sankaran, Abhilash; Staszel, Christopher; Yarin, Alexander; Mashayek, Farzad

2016-11-01

The charging of the dielectric liquid inside an electrostatic atomizer is studied numerically by developing codes based on the OpenFOAM platform. Electrostatic atomization is an appealing technology in painting, fuel injection and oil coating systems due to improved particle-size distribution, enhanced controlability of droplets' trajectories and lower power consumption. The numerical study is conducted concurrently to an experimental investigation to facilitate the validation and deliver feedback for further development. The atomizer includes a pin electrode that is placed at the center of a converging chamber. The chamber orifice is located at a known distance from the electrode tip. The pin electrode is connected to a high voltage that leads to the charging of the liquid. In the present work, the theoretical foundations of separated treatment of the polarized layer and the electronuetral bulk flow are set by describing the governing equations, relevant boundary conditions and the matching condition between these two domains. The resulting split domains are solved numerically to find the distribution of velocity and electrostatic fields over the specified regions. National Science Foundation Award Number: 1505276.

Liquid atomization in supersonic flows

NASA Astrophysics Data System (ADS)

Missoum, Azzedine

An experimental investigation of the atomization of a round liquid jet by coaxial, costream injection into a supersonic, Mach 1.5 air flow is reported. Extensive flow visualization was conducted using schlieren/shadowgraph, flash photography, and short duration (ns) laser imaging. The finer details of the jet were revealed when viewed under high magnification with the help of a microscope. The liquid and air pressures were varied individually. Photographic evidence indicates the presence of three regions within the liquid jet: a primary region enclosed by the first shock cell where the primary breakup occurs, a secondary region in which the jet is totally broken because of its interaction with the supersonic wave structure, and a third, subsonic region further downstream. It was found that the breakup mechanism of liquid jets in supersonic airstreams is quite complex. The breakup seems to be initiated by the growth of the turbulent structure on the liquid surface and the subsequent detachment of the three-dimensional structure as fine droplets by the intense shear at the liquid-gas interface. This seems to confirm the boundary layer stripping mechanism. The liquid jet expands into a bubble like formation as it interacts with the first set of waves. Higher liquid injection pressures resulted in higher initial spray angles. The liquid jet displayed a geometry strongly dependent on the pressure distribution resulting from the wave structure present in the supersonic jet. Droplet size and velocity distributions were measured by the P/DPA (Phase/Doppler Particle Analyzer) system. The Sauter Mean Diameter (SMD) was measured at several axial and radial locations at various liquid and air pressures. The SMD shows a decrease with increase in both the air-to-liquid mass flow ratio and the Weber number. The drop size decreased towards the outer edges of the jet. The results lead one to conclude that the coaxial, coflowing configuration is very attractive for atomizing scramjet liquid fuels.

Evaporating Spray in Supersonic Streams Including Turbulence Effects

NASA Technical Reports Server (NTRS)

Balasubramanyam, M. S.; Chen, C. P.

2006-01-01

Evaporating spray plays an important role in spray combustion processes. This paper describes the development of a new finite-conductivity evaporation model, based on the two-temperature film theory, for two-phase numerical simulation using Eulerian-Lagrangian method. The model is a natural extension of the T-blob/T-TAB atomization/spray model which supplies the turbulence characteristics for estimating effective thermal diffusivity within the droplet phase. Both one-way and two-way coupled calculations were performed to investigate the performance of this model. Validation results indicate the superiority of the finite-conductivity model in low speed parallel flow evaporating sprays. High speed cross flow spray results indicate the effectiveness of the T-blob/T-TAB model and point to the needed improvements in high speed evaporating spray modeling.

Effect of broad properties fuel on injector performance in a reverse flow combustor

NASA Technical Reports Server (NTRS)

Raddlebaugh, S. M.; Norgren, C. T.

1983-01-01

The effect of fuel type on the performance of various fuel injectors was investigated in a reverse flow combustor. Combustor performance and emissions are documented for simplex pressure atomizing, spill flow, and airblast fuel injectors using a broad properties fuel and compared with performance using Jet A fuel. Test conditions simulated a range of flight conditions including sea level take off, low and high altitude cruise, as well as a parametric evaluation of the effect of increased combustor loading. The baseline simplex injector produced higher emission levels with corresponding lower combustion efficiency with the broad properties fuel. There was little or not loss in performance by the two advanced concept injectors with the broad properties fuel. The airblast injector proved to be especially insensitive to fuel type.

Towards More Efficient, Greener Syntheses through Flow Chemistry.

PubMed

Lummiss, Justin A M; Morse, Peter D; Beingessner, Rachel L; Jamison, Timothy F

2017-07-01

Technological advances have an important role in the design of greener synthetic processes. In this Personal Account, we describe a wide range of thermal, photochemical, catalytic, and biphasic chemical transformations examined by our group. Each of these demonstrate how the merits of a continuous flow synthesis platform can align with some of the goals put forth by the Twelve Principles of Green Chemistry. In particular, we illustrate the potential for improved reaction efficiency in terms of atom economy, product yield and reaction rates, the ability to design synthetic process with chemical and solvent waste reduction in mind as well as highlight the benefits of the real-time monitoring capabilities in flow for highly controlled synthetic output. © 2017 The Chemical Society of Japan & Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Effect of gas mass flux on cryogenic liquid jet breakup

NASA Technical Reports Server (NTRS)

Ingebo, R. D.

1992-01-01

A scattered-light scanning instrument developed at NASA Lewis Research Center was used to measure the characteristic drop size of clouds of liquid nitrogen droplets. The instrument was calibrated with suspensions of monosized polystyrene spheres. In this investigation of the mechanism of liquid nitrogen jet disintegration in a high-velocity gas flow, the Sauter mean diameter, D32, was found to vary inversely with the nitrogen gas mass flux raised to the power 1.33. Values of D32 varied from 5 to 25 microns and the mass flux exponent of 1.33 agrees well with theory for liquid jet breakup in high-velocity gas flows. The loss of very small droplets due to the high vaporization rate of liquid nitrogen was avoided by sampling the spray very close to the atomizer, i.e., 1.3 cm downstream of the nozzle orifice. The presence of high velocity and thermal gradients in the gas phase also made sampling of the particles difficult. As a result, it was necessary to correct the measurements for background noise produced by both highly turbulent gas flows and thermally induced density gradients in the gas phase.

Liquid Metals as Plasma-facing Materials for Fusion Energy Systems: From Atoms to Tokamaks

DOE Office of Scientific and Technical Information (OSTI.GOV)

Stone, Howard A.; Koel, Bruce E.; Bernasek, Steven L.

The objective of our studies was to advance our fundamental understanding of liquid metals as plasma-facing materials for fusion energy systems, with a broad scope: from atoms to tokamaks. The flow of liquid metals offers solutions to significant problems of the plasma-facing materials for fusion energy systems. Candidate metals include lithium, tin, gallium, and their eutectic combinations. However, such liquid metal solutions can only be designed efficiently if a range of scientific and engineering issues are resolved that require advances in fundamental fluid dynamics, materials science and surface science. In our research we investigated a range of significant and timelymore » problems relevant to current and proposed engineering designs for fusion reactors, including high-heat flux configurations that are being considered by leading fusion energy groups world-wide. Using experimental and theoretical tools spanning atomistic to continuum descriptions of liquid metals, and bridging surface chemistry, wetting/dewetting and flow, our research has advanced the science and engineering of fusion energy materials and systems. Specifically, we developed a combined experimental and theoretical program to investigate flows of liquid metals in fusion-relevant geometries, including equilibrium and stability of thin-film flows, e.g. wetting and dewetting, effects of electromagnetic and thermocapillary fields on liquid metal thin-film flows, and how chemical interactions and the properties of the surface are influenced by impurities and in turn affect the surface wetting characteristics, the surface tension, and its gradients. Because high-heat flux configurations produce evaporation and sputtering, which forces rearrangement of the liquid, and any dewetting exposes the substrate to damage from the plasma, our studies addressed such evaporatively driven liquid flows and measured and simulated properties of the different bulk phases and material interfaces. The range of our studies included (i) quantum mechanical calculations that allow inclusion of many thousands of atoms for the characterization of the interface of liquid metals exposed to continuous bombardment by deuterium and tritium as expected in fusion, (ii) molecular dynamics studies of the phase behavior of liquid metals, which (a) utilize thermodynamic properties computed using our quantum mechanical calculations and (b) establish material and wetting properties of the liquid metals, including relevant eutectics, (iii) experimental investigations of the surface science of liquid metals, interacting both with the solid substrate as well as gaseous species, and (iv) fluid dynamical studies that incorporate the material and surface science results of (ii) and (iii) in order to characterize flow in capillary porous materials and the thin-film flow along curved boundaries, both of which are potentially major components of plasma-facing materials. The outcome of these integrated studies was new understanding that enables developing design rules useful for future developments of the plasma-facing components critical to the success of fusion energy systems.« less

Resonant Laser Manipulation of an Atomic Beam

DTIC Science & Technology

2010-07-01

similar species such as alkali metals . 15. SUBJECT TERMS 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF ABSTRACT 18. NUMBER OF PAGES...resonant laser-atom interaction with other rarefied and collisional solvers for similar species such as alkali metals . Keywords: atomic beam, cesium...a target flow over length scales which push the limits of physical manufacture. The ability to create masks, beam blocks, controlling electric

Broadband X-ray Imaging in the Near-Field Region of an Airblast Atomizer

NASA Astrophysics Data System (ADS)

Li, Danyu; Bothell, Julie; Morgan, Timothy; Heindel, Theodore

2017-11-01

The atomization process has a close connection to the efficiency of many spray applications. Examples include improved fuel atomization increasing the combustion efficiency of aircraft engines, or controlled droplet size and spray angle enhancing the quality and speed of the painting process. Therefore, it is vital to understand the physics of the atomization process, but the near-field region is typically optically dense and difficult to probe with laser-based or intrusive measurement techniques. In this project, broadband X-ray radiography and X-ray computed tomography (CT) imaging were performed in the near-field region of a canonical coaxial airblast atomizer. The X-ray absorption rate was enhanced by adding 20% by weight of Potassium Iodide to the liquid phase to increase image contrast. The radiographs provided an estimate of the liquid effective mean path length and spray angle at the nozzle exit for different flow conditions. The reconstructed CT images provided a 3D map of the time-average liquid spray distribution. X-ray imaging was used to quantify the changes in the near-field spray characteristics for various coaxial airblast atomizer flow conditions. Office of Naval Research.

Energetic atomic and molecular ions of ionospheric origin observed in distant magnetotail flow-reversal events

NASA Technical Reports Server (NTRS)

Christon, S. P.; Gloeckler, G.; Williams, D. J.; Mukai, T.; Mcentire, R. W.; Jacquey, C.; Angelopoulos, V.; Lui, A. T. Y.; Kokubun, S.; Fairfield, D. H.

1994-01-01

Energetic atomic (O(+1) and N(+1)) and molecular (O2(+1), NO(+1), and N2(+1)) ions of ionospheric origin were observed in Earth's magnetotail at X approximately -146 R(sub E) during two plasma sheet sunward/tailward flow-reversal events measured by instruments on the GEOTAIL spacecraft. These events were associated with concurrent ground-measured geomagnetic disturbance intensification at auroral-and mid-latitudes (Kp = 7(-)). Energetic ions in the sunward-component and tailward flows were from both the solar wind and ionosphere. Plasma and energetic ions participated in the flows. During tailward flow, ionospheric origin ion abundance ratios at approximately 200-900 km/s in the rest frame were N(+1)/O(+1) = approximately 25-30% and ((O2(+1), NO(+1), and N2(+1))/O(+1) = approximately 1-2%. We argue that tailward flow most likely initiated approximately 80-100 R(sub E) tailward of Earth and molecular ions were in the plasma sheet prior to geomagnetic intensification onset.

Eutectic structures in friction spot welding joint of aluminum alloy to copper

NASA Astrophysics Data System (ADS)

Shen, Junjun; Suhuddin, Uceu F. H.; Cardillo, Maria E. B.; dos Santos, Jorge F.

2014-05-01

A dissimilar joint of AA5083 Al alloy and copper was produced by friction spot welding. The Al-MgCuAl2 eutectic in both coupled and divorced manners were found in the weld. At a relatively high temperature, mass transport of Cu due to plastic deformation, material flow, and atomic diffusion, combined with the alloy system of AA5083 are responsible for the ternary eutectic melting.

Atmospheric Pressure Plasma Jet for Chem/Bio Warfare Decontamination

NASA Astrophysics Data System (ADS)

Herrmann, Hans W.; Henins, Ivars; Park, Jaeyoung; Selwyn, Gary S.

1999-11-01

Atmospheric Pressure Plasma Jet (APPJ) technology may provide a much needed method of CBW decontamination which, unlike traditional decon methods, is dry and nondestructive to sensitive equipment and materials. The APPJ discharge uses a high-flow feedgas consisting primarily of an inert carrier gas, such as He, and a small amount of a reactive additive, such as O2, which flows between capacitively-coupled electrodes powered at 13.56 MHz. The plasma generates highly reactive metastable and atomic species of oxygen which are then directed onto a contaminated surface. The reactive effluent of the APPJ has been shown to effectively neutralize VX nerve agent as well as simulants for anthrax and mustard blister agent. Research efforts are now being directed towards reducing He consumption and increasing the allowable stand-off distance. Recent results demonstrate that by replacing the O2 reactive additive with CO2, ozone formation is greatly reduced. This has the result of extending the lifetime of atomic oxygen by an order of magnitude or more. A recirculating APP Decon Chamber which combines heat, vacuum, forced convection and reactivity is currently being developed for enhanced decontamination of sensitive equipment. Several techniques are also being evaluated for use in an APP Decon Jet for decontamination of items which cannot be placed inside a chamber.

Gas dynamics and mixture formation in swirled flows with precession of air flow

NASA Astrophysics Data System (ADS)

Tretyakov, V. V.; Sviridenkov, A. A.

2017-10-01

The effect of precessing air flow on the processes of mixture formation in the wake of the front winding devices of the combustion chambers is considered. Visual observations have shown that at different times the shape of the atomized jet is highly variable and has signs of precessing motion. The experimental data on the distribution of the velocity and concentration fields of the droplet fuel in the working volume of the flame tube of a typical combustion chamber are obtained. The method of calculating flows consisted in integrating the complete system of Reynolds equations written in Euler variables and closed with the two-parameter model of turbulence k-ε. Calculation of the concentration fields of droplet and vapor fuel is based on the use of models for disintegration into droplets of fuel jets, fragmentation of droplets and analysis of motion and evaporation of individual droplets in the air flow. Comparison of the calculation results with experimental data showed their good agreement.

Development and Application of Novel Diagnostics for Arc-Jet Characterization

NASA Technical Reports Server (NTRS)

Hanson, R. K.

2002-01-01

This NASA-Ames University Consortium Project has focused on the design and demonstration of optical absorption sensors using tunable diode laser to target atomic copper impurities from electrode erosion in thc arc-heater metastable electronic excited states of molecular nitrogen, atomic argon, aid atomic oxygen in the arcjet plume. Accomplishments during this project include: 1. Design, construction, and assembly of optical access to the arc-heater gas flow. 2. Design of diode laser sensor for copper impurities in the arc-heater flow. 3 . Diode laser sensor design and test in laboratory plasmas for metastable Ar(3P), O(5S), N(4P), and N2(A). 4. Diode laser sensor demonstration measurements in the test cell to monitor species in the arc-jet plume.

Analysis of the effects of atomic mass, jet velocity, and radiative cooling on the dimensionless parameters of counter-propagating, weakly collisional plasma flows

NASA Astrophysics Data System (ADS)

Collins, Gilbert; Valenzuela, Julio; Beg, Farhat

2016-10-01

We have studied the collision of counter-propagating plasma flows using opposing conical wire arrays driven by the 200kA, 150ns rise-time `GenASIS' driver. These plasma flows produced weakly collisional, well-defined bow-shock structures. Varying initial parameters such as the opening angle of the array and the atomic mass of the wires allowed us to modify quantities such as the density contrast between jets, intra-jet mean free path (λmfp, scales with v, atomic mass A, and ionization state Zi-4) , Reynolds number (Re, scales with AZ), and the Peclet number (Pe, scales with Z). We calculate these dimensionless quantities using schlieren imagery, interferometry, and emission data, and determine whether they meet the scaling criteria necessary for the comparison to and subsequent study of astrophysical plasmas. This work was partially supported by the Department of Energy Grant Number DE-SC0014493.

Combustion of liquid sprays at high pressures

NASA Technical Reports Server (NTRS)

Shearer, A. J.; Faeth, G. M.

1977-01-01

The combustion of pressure atomized fuel sprays in high pressure stagnant air was studied. Measurements were made of flame and spray boundaries at pressures in the range 0.1-9 MPa for methanol and n-pentane. At the higher test pressure levels, critical phenomena are important. The experiments are compared with theoretical predictions based on a locally homogeneous two-phase flow model. The theory correctly predicted the trends of the data, but underestimates flame and spray boundaries by 30-50 percent, indicating that slip is still important for the present experiments (Sauter mean diameters of 30 microns at atmospheric pressure under cold flow conditions). Since the sprays are shorter at high pressures, slip effects are still important even though the density ratio of the phases approach one another as the droplets heat up. The model indicates the presence of a region where condensed water is present within the spray and provides a convenient means of treating supercritical phenomena.

Stabilized Alumina/Ethanol Colloidal Dispersion for Seeding High Temperature Air Flows

NASA Technical Reports Server (NTRS)

Wernet, Judith H.; Wernet, Mark P.

1994-01-01

Seeding air flows with particles to enable measurements of gas velocities via laser anemometry and/or particle image velocimetry techniques can be quite exasperating. The seeding requirements are compounded when high temperature environments are encountered and special care must be used in selecting a refractory seed material. The pH stabilization techniques commonly employed in ceramic processing are used to obtain stable dispersions for generating aerosols of refractory seed material. By adding submicron alumina particles to a preadjusted pH solution of ethanol, a stable dispersion is obtained which when atomized produces a high quality aerosol. Commercial grade alumina powder is used with a moderate size distribution. The technique is not limited to alumina/ethanol and is also demonstrated with an alumina/H2O system. Other ceramic powders in various polar solvents could also be used once the point of zero charge (pH(sub pzc)) of the powder in the solvent has been determined.

Fabrication of High Performing PEMFC Catalyst-Coated Membranes with a Low Cost Air-Assisted Cylindrical Liquid Jets Spraying System

DOE PAGES

Peng, Xiong; Omasta, Travis; Rigdon, William; ...

2016-11-15

In this paper, a low cost air-assisted cylindrical liquid jets spraying (ACLJS) system was developed to prepare high-performance catalyst-coated membranes (CCMs) for proton exchange membrane fuel cells (PEMFCs). The catalyst ink was flowed from a cylindrical orifice and was atomized by an air stream fed from a coaxial slit and sprayed directly onto the membrane, which was suctioned to a heated aluminum vacuum plate. The CCM pore architecture including size, distribution and volume can be controlled using various flow parameters, and the impact of spraying conditions on electrode structure and PEMFC performance was investigated. CCMs fabricated in the fiber-type break-upmore » regime by ACLJS achieved very high performance during PEMFC testing, with the top-performing cells having a current density greater than 1900 mA/cm 2 at 0.7 V under H 2/O 2 flows and 700 mA/cm 2 under H 2/Air at 1.5 bar(absolute) pressure and 60% gas RH, and 80°C cell temperature.« less

Fabrication of High Performing PEMFC Catalyst-Coated Membranes with a Low Cost Air-Assisted Cylindrical Liquid Jets Spraying System

DOE Office of Scientific and Technical Information (OSTI.GOV)

Peng, Xiong; Omasta, Travis; Rigdon, William

In this paper, a low cost air-assisted cylindrical liquid jets spraying (ACLJS) system was developed to prepare high-performance catalyst-coated membranes (CCMs) for proton exchange membrane fuel cells (PEMFCs). The catalyst ink was flowed from a cylindrical orifice and was atomized by an air stream fed from a coaxial slit and sprayed directly onto the membrane, which was suctioned to a heated aluminum vacuum plate. The CCM pore architecture including size, distribution and volume can be controlled using various flow parameters, and the impact of spraying conditions on electrode structure and PEMFC performance was investigated. CCMs fabricated in the fiber-type break-upmore » regime by ACLJS achieved very high performance during PEMFC testing, with the top-performing cells having a current density greater than 1900 mA/cm 2 at 0.7 V under H 2/O 2 flows and 700 mA/cm 2 under H 2/Air at 1.5 bar(absolute) pressure and 60% gas RH, and 80°C cell temperature.« less

Atomically layer-by-layer diffusion of oxygen/hydrogen in highly epitaxial PrBaCo2O5.5+δ thin films

NASA Astrophysics Data System (ADS)

Bao, Shanyong; Xu, Xing; Enriquez, Erik; Mace, Brennan E.; Chen, Garry; Kelliher, Sean P.; Chen, Chonglin; Zhang, Yamei; Whangbo, Myung-Hwan; Dong, Chuang; Zhang, Qinyu

2015-12-01

Single-crystalline epitaxial thin films of PrBaCo2O5.5+δ (PrBCO) were prepared, and their resistance R(t) under a switching flow of oxidizing and reducing gases were measured as a function of the gas flow time t in the temperature range of 200-800 °C. During the oxidation cycle under O2, the PrBCO films exhibit fast oscillations in their dR(t)/dt vs. t plots, which reflect the oxidation processes, Co2+/Co3+ → Co3+ and Co3+ → Co3+/Co4+, that the Co atoms of PrBCO undergo. Each oscillation consists of two peaks, with larger and smaller peaks representing the oxygen/hydrogen diffusion through the (BaO)(CoO2)(PrO)(CoO2) layers of PrBCO via the oxygen-vacancy-exchange mechanism. This finding paves a significant avenue for cathode materials operating in low-temperature solid-oxide-fuel-cell devices and for chemical sensors with wide range of operating temperature.

Nonequilibrium in a low power arcjet nozzle

NASA Technical Reports Server (NTRS)

Zube, Dieter M.; Myers, Roger M.

1991-01-01

Emission spectroscopy measurements were made of the plasma flow inside the nozzle of a 1 kW class arcjet thruster. The thruster propellant was a hydrogen-nitrogen mixture used to simulate fully decomposed hydrazine. The 0.25 mm diameter holes were drilled into the diverging section of the tungsten thruster nozzle to provide optical access to the internal flow. Atomic electron excitation, vibrational, and rotational temperatures were determined for the expanding plasma using relative line intensity techniques. The atomic excitation temperatures decreased from 18,000K at a location 3 mm downstream of the constrictor to 9,000K at a location 9 mm from the constrictor, while the molecular vibrational and rotational temperatures decreased from 6,500K to 2,500K and from 8,000K to 3,000K, respectively, between the same locations. The electron density measured using hydrogen H line Stark broadening decreased from about 10(exp 15) cm(-3) to about 2 times 10(exp 14) cm(-3) during the expansion. The results show that the plasma is highly nonequilibrium throughout the nozzle, with most relaxation times equal or exceeding the particle residence time.

Highly ionized atoms in cooling gas

NASA Technical Reports Server (NTRS)

Edgar, R. J.; Chevalier, R. A.

1986-01-01

The ionization of low density gas cooling from a high temperature was calculated. The evolution during the cooling is assumed to be isochoric, isobaric, or a combination of these cases. The calculations are used to predict the column densities and ultraviolet line luminosities of highly ionized atoms in cooling gas. In a model for cooling of a hot galactic corona, it is shown that the observed value of N(N V) can be produced in the cooling gas, while the predicted value of N(Si IV) falls short of the observed value by a factor of about 5. The same model predicts fluxes of ultraviolet emission lines that are a factor of 10 lower than the claimed detections of Feldman, Brune, and Henry. Predictions are made for ultraviolet lines in cooling flows in early-type galaxies and clusters of galaxies. It is shown that the column densities of interest vary over a fairly narrow range, while the emission line luminosities are simply proportional to the mass inflow rate.

Highly ionized atoms in cooling gas. [in model for cooling of hot Galactic corona

NASA Technical Reports Server (NTRS)

Edgar, Richard J.; Chevalier, Roger A.

1986-01-01

The ionization of low density gas cooling from a high temperature was calculated. The evolution during the cooling is assumed to be isochoric, isobaric, or a combination of these cases. The calculations are used to predict the column densities and ultraviolet line luminosities of highly ionized atoms in cooling gas. In a model for cooling of a hot galactic corona, it is shown that the observed value of N(N V) can be produced in the cooling gas, while the predicted value of N(Si IV) falls short of the observed value by a factor of about 5. The same model predicts fluxes of ultraviolet emission lines that are a factor of 10 lower than the claimed detections of Feldman, Bruna, and Henry. Predictions are made for ultraviolet lines in cooling flows in early-type galaxies and clusters of galaxies. It is shown that the column densities of interest vary over a fairly narrow range, while the emission line luminosities are simply proportional to the mass inflow rate.

Evaporation of Water Droplets Moving Through High-Temperature Gases

NASA Astrophysics Data System (ADS)

Kuznetsov, G. V.; Strizhak, P. A.

2018-01-01

With the use of high-speed recording and diagnostic facilities, an experimental study has been made of the evaporation of droplets (of characteristic size Rm ≈ 0.05-0.035 mm) of atomized flow of water-based suspensions with typical soil impurities (silt and clay) moving in a high-temperature (about 1100 K) gaseous medium (with the example of acetone combustion products). The relative mass concentration of soil components in the suspension was varied over the range of γ = 0-1%. A strong influence of the above impurities on the main characteristic of evaporation — the relative change in the droplet radius ΔR — has been established. The influence of the initial temperature (varied over the range of Tw = 278-320 K) of the atomized suspension on the evaporation rate of the latter has been determined. It has been shown that the values of integral characteristics of the process of evaporation of suspensions with soil impurities can be much (2-3 times) higher than for water without these components.

An integrated MEMS infrastructure for fuel processing: hydrogen generation and separation for portable power generation

NASA Astrophysics Data System (ADS)

Varady, M. J.; McLeod, L.; Meacham, J. M.; Degertekin, F. L.; Fedorov, A. G.

2007-09-01

Portable fuel cells are an enabling technology for high efficiency and ultra-high density distributed power generation, which is essential for many terrestrial and aerospace applications. A key element of fuel cell power sources is the fuel processor, which should have the capability to efficiently reform liquid fuels and produce high purity hydrogen that is consumed by the fuel cells. To this end, we are reporting on the development of two novel MEMS hydrogen generators with improved functionality achieved through an innovative process organization and system integration approach that exploits the advantages of transport and catalysis on the micro/nano scale. One fuel processor design utilizes transient, reverse-flow operation of an autothermal MEMS microreactor with an intimately integrated, micromachined ultrasonic fuel atomizer and a Pd/Ag membrane for in situ hydrogen separation from the product stream. The other design features a simpler, more compact planar structure with the atomized fuel ejected directly onto the catalyst layer, which is coupled to an integrated hydrogen selective membrane.

Over atmospheric pressure flowing afterglow

NASA Astrophysics Data System (ADS)

Ganciu, Mihai; Orphal, Johannes; Vervloet, Michel; Pointu, Anne-Marie; Touzeau, Michel

2002-10-01

A Tabletop discharge * created above atmospheric pressure in a N2 gas flow, uses some 10 kV very fast high voltage pulses applied between needle electrodes with some 10 kHz repetition rate. It is followed by a post-discharge, in a plastic tube with 6-mm internal diameter. Adjusting the flow and the repetition rate, the post-discharge exhibits a surprisingly long size, 9-10 m, as shown by the tube fluorescence. Preliminary spectroscopic measurements demonstrate that fluorescence is due to internal gas excited molecules (CN and NH) that are locally created by active species interaction with organic impurities. The discharge emission spectrum evidences a high nitrogen atom production rate, much higher than attainable rate with a Dielectric Barrier Discharge with same applied voltage pulses. For small air quantities added in the post-discharge, spectrum exhibits rich UV range corresponding to NO excited states. Further studies will be devoted to the post-discharge kinetics and to possible applications to medical sterilization. *M. Ganciu, private communication

Internal Energy Transfer and Dissociation Model Development using Accelerated First-Principles Simulations of Hypersonic Flow Features

DTIC Science & Technology

2013-07-11

in Fig. 3) is simulated. Each atom interacts with its neighboring atoms through a potential energy surface (PES), such as the simple Lennard - Jones ... Lennard -­‐ Jones  (LJ)   potential  energy  surface  (PES)  dictating  atomic  interaction  forces. The main point of this section is to...the potential energy surface (PES) that governs individual atomic interaction forces. In contrast to existing rotational energy models, we found

Potential roughness near lithographically fabricated atom chips

DOE Office of Scientific and Technical Information (OSTI.GOV)

Krueger, P.; Laboratoire Kastler Brossel, Ecole Normale Superieure, 24 Rue Lhomond, F-75005 Paris; Andersson, L. M.

2007-12-15

Potential roughness has been reported to severely impair experiments in magnetic microtraps. We show that these obstacles can be overcome as we measure disorder potentials that are reduced by two orders of magnitude near lithographically patterned high-quality gold layers on semiconductor atom chip substrates. The spectrum of the remaining field variations exhibits a favorable scaling. A detailed analysis of the magnetic field roughness of a 100-{mu}m-wide wire shows that these potentials stem from minute variations of the current flow caused by local properties of the wire rather than merely from rough edges. A technique for further reduction of potential roughnessmore » by several orders of magnitude based on time-orbiting magnetic fields is outlined.« less

Vibrational and Electronic Energy Transfer and Dissociation of Diatomic Molecules by Electron Collisions

NASA Technical Reports Server (NTRS)

Huo, Winifred M.; Langhoff, Stephen R. (Technical Monitor)

1995-01-01

At high altitudes and velocities equal to or greater than the geosynchronous return velocity (10 kilometers per second), the shock layer of a hypersonic flight will be in thermochemical nonequilibrium and partially ionized. The amount of ionization is determined by the velocity. For a trans atmospheric flight of 10 kilometers per second and at an altitude of 80 kilometers, a maximum of 1% ionization is expected. At a velocity of 12 - 17 kilometer per second, such as a Mars return mission, up to 30% of the atoms and molecules in the flow field will be ionized. Under those circumstances, electrons play an important role in determining the internal states of atoms and molecules in the flow field and hence the amount of radiative heat load and the distance it takes for the flow field to re-establish equilibrium. Electron collisions provide an effective means of transferring energy even when the electron number density is as low as 1%. Because the mass of an electron is 12,760 times smaller than the reduced mass of N2, its average speed, and hence its average collision frequency, is more than 100 times larger. Even in the slightly ionized regime with only 1% electrons, the frequency of electron-molecule collisions is equal to or larger than that of molecule-molecule collisions, an important consideration in the low density part of the atmosphere. Three electron-molecule collision processes relevant to hypersonic flows will be considered: (1) vibrational excitation/de-excitation of a diatomic molecule by electron impact, (2) electronic excitation/de-excitation, and (3) dissociative recombination in electron-diatomic ion collisions. A review of available data, both theory and experiment, will be given. Particular attention will be paid to tailoring the molecular physics to the condition of hypersonic flows. For example, the high rotational temperatures in a hypersonic flow field means that most experimental data carried out under room temperatures are not applicable. Also, the average electron temperature is expected to be between 10,000 and 20,000 K. Thus only data for low energy electrons are relevant to the model.

Modification, calibration, and performance of the Ultra-High Sensitivity Aerosol Spectrometer for particle size distribution and volatility measurements during the Atmospheric Tomography Mission (ATom) airborne campaign

NASA Astrophysics Data System (ADS)

Kupc, Agnieszka; Williamson, Christina; Wagner, Nicholas L.; Richardson, Mathews; Brock, Charles A.

2018-01-01

Atmospheric aerosol is a key component of the chemistry and climate of the Earth's atmosphere. Accurate measurement of the concentration of atmospheric particles as a function of their size is fundamental to investigations of particle microphysics, optical characteristics, and chemical processes. We describe the modification, calibration, and performance of two commercially available, Ultra-High Sensitivity Aerosol Spectrometers (UHSASs) as used on the NASA DC-8 aircraft during the Atmospheric Tomography Mission (ATom). To avoid sample flow issues related to pressure variations during aircraft altitude changes, we installed a laminar flow meter on each instrument to measure sample flow directly at the inlet as well as flow controllers to maintain constant volumetric sheath flows. In addition, we added a compact thermodenuder operating at 300 °C to the inlet line of one of the instruments. With these modifications, the instruments are capable of making accurate (ranging from 7 % for Dp < 0.07 µm to 1 % for Dp > 0.13 µm), precise (< ±1.2 %), and continuous (1 Hz) measurements of size-resolved particle number concentration over the diameter range of 0.063-1.0 µm at ambient pressures of > 1000 to 225 hPa, while simultaneously providing information on particle volatility.We assessed the effect of uncertainty in the refractive index (n) of ambient particles that are sized by the UHSAS assuming the refractive index of ammonium sulfate (n = 1.52). For calibration particles with n between 1.44 and 1.58, the UHSAS diameter varies by +4/-10 % relative to ammonium sulfate. This diameter uncertainty associated with the range of refractive indices (i.e., particle composition) translates to aerosol surface area and volume uncertainties of +8.4/-17.8 and +12.4/-27.5 %, respectively. In addition to sizing uncertainty, low counting statistics can lead to uncertainties of < 20 % for aerosol surface area and < 30 % for volume with 10 s time resolution. The UHSAS reduction in counting efficiency was corrected for concentrations > 1000 cm-3.Examples of thermodenuded and non-thermodenuded aerosol number and volume size distributions as well as propagated uncertainties are shown for several cases encountered during the ATom project. Uncertainties in particle number concentration were limited by counting statistics, especially in the tropical upper troposphere where accumulation-mode concentrations were sometimes < 20 cm-3 (counting rates ˜ 5 Hz) at standard temperature and pressure.

Development of ultrasonic atomizer and its application to S. I. engines

DOE Office of Scientific and Technical Information (OSTI.GOV)

Namiyama, K.; Nakamura, H.; Kokubo, K.

1989-01-01

This paper describes a fuel atomizer developed for S.I. engines based on ultrasonic vibrations. As the spray is characterized by fine droplet size and low penetration, it facilitates fuel movement and the formation of a homogeneous mixture. The spray behavior of this atomizer is easily influenced by ambient air motion. Therefore, the spray is most effectively delivered to the cylinders by precise injection timing. The ultrasonic atomizer disperses a fine spray over a wide flow rate range. A single cylinder engine fitted with the atomizer showed advantages in combustion speed and transient response performance.

New singlet oxygen generator for chemical oxygen-iodine lasers

NASA Astrophysics Data System (ADS)

Yoshida, S.; Saito, H.; Fujioka, T.; Yamakoshi, H.; Uchiyama, T.

1986-11-01

Experiments have been carried out to investigate a new method for generating O2(1Delta) with long-time operation of an efficient chemical oxygen-iodine laser system in mind. An impinging-jet nozzle was utilized to atomize a H2O2-KOH solution so that the alkaline H2O2/Cl2 reaction might occur in droplet-gas phase with high excitation efficiency. Experimental results indicate that the present generator can yield as high as 80 percent of O2(1Delta) with reasonable O2 flow rate.

Atomic-scale thermocapillary flow in focused ion beam milling

NASA Astrophysics Data System (ADS)

Das, Kallol; Johnson, Harley; Freund, Jonathan

2016-11-01

Focused ion beams (FIB) offer an attractive tool for nanometer-scale manufacturing and material processing, particularly because they can be focused to a few nanometer diameter spot. This motivates their use for many applications, such as sample preparation for transmission electron microscopy (TEM), forming nanometer scale pores in thin films for DNA sequencing. Despite its widespread use, the specific mechanisms of FIB milling, especially at high ion fluxes for which significant phase change might occur, remains incompletely understood. Here we investigate the process of nanopore fabrication in thin Si films using molecular dynamics simulation where Ga+ ions are used as the focused ions. For a range of ion intensities in a realistic configuration, a recirculating melt region develops, which is seen to flow with a symmetrical pattern, counter to how it would flow were it is driven by the ion momentum flux. Such flow is potentially important for the shape and composition of the formed structures. Relevant stress scales and estimated physical properties of silicon under these extreme conditions support the importance thermocapillary effects. A continuum flow model with Marangoni forcing reproduces the flow.

Y-doped Li 8ZrO 6: A Li-Ion Battery Cathode Material with High Capacity

DOE PAGES

Huang, Shuping; Wilson, Benjamin E.; Wang, Bo; ...

2015-08-11

We study—experimentally and theoretically—the energetics, structural changes, and charge flows during the charging and discharging processes for a new high-capacity cathode material, Li 8ZrO 6 (LZO), which we study both pure and yttrium-doped. We quantum mechanically calculated the stable delithiated configurations, the delithiation energy, the charge flow during delithiation, and the stability of the delithiated materials. We find that Li atoms are easier to extract from tetrahedral sites than octahedral ones. We calculate a large average voltage of 4.04 eV vs Li/Li + for delithiation of the first Li atom in a primitive cell, which is confirmed by galvanostatic charge/dischargemore » cycling data. Energy calculations indicate that topotactic delithiation is kinetically favored over decomposition into Li, ZrO 2, and O 2 during the charging process, although the thermodynamic energy of the topotactic reaction is less favorable. When one or two lithium atoms are extracted from a primitive cell of LZO, its volume and structure change little, whereas extraction of the third lithium greatly distorts the layered structure. The Li 6ZrO 6 and Li 5ZrO 6 delithiation products can be thermodynamically metastable to release of O 2. Experimentally, materials with sufficiently small particle size for efficient delithiation and relithiation were achieved within an yttrium-doped LZO/carbon composite cathode that exhibited an initial discharge capacity of at least 200 mAh/g over the first 10 cycles, with 142 mAh/g maintained after 60 cycles. Computations predict that during the charging process, the oxygen ion near the Li vacancy is oxidized for both pure LZO and yttrium-doped LZO, which leads to a small-polaron hole.« less

Y-doped Li 8ZrO 6: A Li-Ion Battery Cathode Material with High Capacity

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huang, Shuping; Wilson, Benjamin E.; Wang, Bo

We study—experimentally and theoretically—the energetics, structural changes, and charge flows during the charging and discharging processes for a new high-capacity cathode material, Li 8ZrO 6 (LZO), which we study both pure and yttrium-doped. We quantum mechanically calculated the stable delithiated configurations, the delithiation energy, the charge flow during delithiation, and the stability of the delithiated materials. We find that Li atoms are easier to extract from tetrahedral sites than octahedral ones. We calculate a large average voltage of 4.04 eV vs Li/Li + for delithiation of the first Li atom in a primitive cell, which is confirmed by galvanostatic charge/dischargemore » cycling data. Energy calculations indicate that topotactic delithiation is kinetically favored over decomposition into Li, ZrO 2, and O 2 during the charging process, although the thermodynamic energy of the topotactic reaction is less favorable. When one or two lithium atoms are extracted from a primitive cell of LZO, its volume and structure change little, whereas extraction of the third lithium greatly distorts the layered structure. The Li 6ZrO 6 and Li 5ZrO 6 delithiation products can be thermodynamically metastable to release of O 2. Experimentally, materials with sufficiently small particle size for efficient delithiation and relithiation were achieved within an yttrium-doped LZO/carbon composite cathode that exhibited an initial discharge capacity of at least 200 mAh/g over the first 10 cycles, with 142 mAh/g maintained after 60 cycles. Computations predict that during the charging process, the oxygen ion near the Li vacancy is oxidized for both pure LZO and yttrium-doped LZO, which leads to a small-polaron hole.« less

Topical Airway Anesthesia for Awake-endoscopic Intubation Using the Spray-as-you-go Technique with High Oxygen Flow.

PubMed

Pirlich, Nina; Lohse, Jana A; Noppens, Rüdiger R

2017-01-13

A patient's willingness to cooperate is an absolute precondition for successful awake intubation of the trachea. Whilst drug-sedation of patients can jeopardize their spontaneous breathing, topical anesthesia of the airway is a popular technique. The spray-as-you-go technique represents one of the simplest opportunities to anesthetize the airway mucosa. The application of local anesthetic through the working channel of the flexible endoscope is a widespread practice for anesthetists as well as pulmonologists. There is neither need for additional devices nor special training as a pre-requisite to perform this technique. However, a known clinical problem is the coughing and gagging reflex that may occur when the liquid anesthetic strikes the airway mucosa and other sensitive structures like the vocal cords. This can be avoided by the use of oxygen applied through the working channel with the aim of fogging the local anesthetic into finer particles. Furthermore, the oxygen flow provides a higher oxygen supply and contributes to a better view, dispersing mucus secretions and blood away from the lens. Using an atomizer with a high oxygen flow of 10 L/min we maximized these benefits, caused less coughing and had more satisfied and therefore cooperative patients. Possible, but very rare complications of using oxygen flow including gastric insufflation, organ rupture or barotrauma did not arise. We attribute the complication-free use of high oxygen flow to the design of the set, which permits flow and pressure release.

AFM AND XPS Characterization of Zinc-Aluminum Alloy Coatings with Attention to Surface Dross and Flow Lines

NASA Astrophysics Data System (ADS)

Harding, Felipe A.; Alarcon, Nelson A.; Toledo, Pedro G.

Surfaces of various zinc-aluminum alloy (Zn-Al) coated steel samples are studied with attention to foreign surface dross by atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS/ESCA). AFM topographic maps of zinc-aluminum alloy surfaces free of dross reveal the perfect nanoscale details of two kinds of dendrites: branched and globular. In all magnifications the dendrites appear smooth and, in general, very clean. XPS analysis of the extreme surface of a Zn-Al sample reveals Al, Zn, Si and O as the main components. The XPS results show no segregation or separation of phases other than those indicated by the ternary Al-Zn-Si diagram. For surfaces of Zn-Al plagued with impurities, high resolution AFM topographic maps reveal three situations: (1) areas with well-defined dendrites, relatively free of dross; (2) areas with small, millimeter-sized black spots known as dross; and (3) areas with large black stains, known as flow lines. Dendrite deformation and dross accumulation increase notably in the neighborhood, apparently clean to the naked eye, of dross or flow lines. XPS results of areas with dross and flow lines indicate unacceptable high concentration of Si and important Si phase separation. These results, in the light of AFM work, reveal that dross and flow lines are a consequence of a high local concentration of Si from high melting point silica and silicate impurities in the Zn-Al alloy source.

A Eulerian-Lagrangian Model to Simulate Two-Phase/Particulate Flows

NASA Technical Reports Server (NTRS)

Apte, S. V.; Mahesh, K.; Lundgren, T.

2003-01-01

Figure 1 shows a snapshot of liquid fuel spray coming out of an injector nozzle in a realistic gas-turbine combustor. Here the spray atomization was simulated using a stochastic secondary breakup model (Apte et al. 2003a) with point-particle approximation for the droplets. Very close to the injector, it is observed that the spray density is large and the droplets cannot be treated as point-particles. The volume displaced by the liquid in this region is significant and can alter the gas-phase ow and spray evolution. In order to address this issue, one can compute the dense spray regime by an Eulerian-Lagrangian technique using advanced interface tracking/level-set methods (Sussman et al. 1994; Tryggvason et al. 2001; Herrmann 2003). This, however, is computationally intensive and may not be viable in realistic complex configurations. We therefore plan to develop a methodology based on Eulerian-Lagrangian technique which will allow us to capture the essential features of primary atomization using models to capture interactions between the fluid and droplets and which can be directly applied to the standard atomization models used in practice. The numerical scheme for unstructured grids developed by Mahesh et al. (2003) for incompressible flows is modified to take into account the droplet volume fraction. The numerical framework is directly applicable to realistic combustor geometries. Our main objectives in this work are: Develop a numerical formulation based on Eulerian-Lagrangian techniques with models for interaction terms between the fluid and particles to capture the Kelvin- Helmholtz type instabilities observed during primary atomization. Validate this technique for various two-phase and particulate flows. Assess its applicability to capture primary atomization of liquid jets in conjunction with secondary atomization models.

Pressurized feed-injection spray-forming apparatus

DOEpatents

Berry, R.A.; Fincke, J.R.; McHugh, K.M.

1995-08-29

A spray apparatus and method are disclosed for injecting a heated, pressurized liquid in a first predetermined direction into a pressurized gas flow that is flowing in a second predetermined direction, to provide for atomizing and admixing the liquid with the gas to form a two-phase mixture. A valve is also disposed within the injected liquid conduit to provide for a pulsed injection of the liquid and timed deposit of the atomized gas phase. Preferred embodiments include multiple liquid feed ports and reservoirs to provide for multiphase mixtures of metals, ceramics, and polymers. 22 figs.

Pressurized feed-injection spray-forming apparatus

DOEpatents

Berry, Ray A.; Fincke, James R.; McHugh, Kevin M.

1995-01-01

A spray apparatus and method for injecting a heated, pressurized liquid in a first predetermined direction into a pressurized gas flow that is flowing in a second predetermined direction, to provide for atomizing and admixing the liquid with the gas to form a two-phase mixture. A valve is also disposed within the injected liquid conduit to provide for a pulsed injection of the liquid and timed deposit of the atomized gas phase. Preferred embodiments include multiple liquid feed ports and reservoirs to provide for multiphase mixtures of metals, ceramics, and polymers.

Product energy distributions and energy partitioning in O atom reactions on surfaces

NASA Technical Reports Server (NTRS)

Halpern, Bret; Kori, Moris

1987-01-01

Surface reactions involving O atoms are likely to be highly exoergic, with different consequences if energy is channeled mostly to product molecules or surface modes. Thus the surface may become a source of excited species which can react elsewhere, or a sink for localized heat deposition which may disrupt the surface. The vibrational energy distribution of the product molecule contains strong clues about the flow of released energy. Two instructive examples of energy partitioning at surfaces are the Pt catalyzed oxidations: (1) C(ads) + O(ads) yields CO* (T is greater than 1000 K); and (2) CO(ads) + O(gas) yields CO2* (T is approx. 300 K). The infrared emission spectra of the excited product molecules were recorded and the vibrational population distributions were determined. In reaction 1, energy appeared to be statistically partitioned between the product CO and several Pt atoms. In reaction 2, partitioning was non-statistical; the CO2 asymmetric stretch distribution was inverted. In gas reactions these results would indicate a long lived and short lived activated complex. The requirement that Pt be heated in O atoms to promote reaction of atomic O and CO at room temperature is specifically addressed. Finally, the fraction of released energy that is deposited in the catalyst is estimated.

Femtosecond, two-photon laser-induced-fluorescence imaging of atomic oxygen in an atmospheric-pressure plasma jet

NASA Astrophysics Data System (ADS)

Schmidt, Jacob B.; Sands, Brian L.; Kulatilaka, Waruna D.; Roy, Sukesh; Scofield, James; Gord, James R.

2015-06-01

Femtosecond, two-photon-absorption laser-induced-fluorescence (fs-TALIF) spectroscopy is employed to measure space- and time-resolved atomic-oxygen distributions in a nanosecond, repetitively pulsed, externally grounded, atmospheric-pressure plasma jet flowing helium with a variable oxygen admixture. The high-peak-intensity, low-average-energy femtosecond pulses result in increased TALIF signal with reduced photolytic inferences. This allows 2D imaging of absolute atomic-oxygen number densities ranging from 5.8   ×   1015 to 2.0   ×   1012cm-3 using a cooled CCD with an external intensifier. Xenon is used for signal and imaging-system calibrations to quantify the atomic-oxygen fluorescence signal. Initial results highlight a transition in discharge morphology from annular to filamentary, corresponding with a change in plasma chemistry from ozone to atomic oxygen production, as the concentration of oxygen in the feed gas is changed at a fixed voltage-pulse-repetition rate. In this configuration, significant concentrations of reactive oxygen species may be remotely generated by sustaining an active discharge beyond the confines of the dielectric capillary, which may benefit applications that require large concentrations of reactive oxygen species such as material processing or biomedical devices.

Atomizer with liquid spray quenching

DOEpatents

Anderson, Iver E.; Osborne, Matthew G.; Terpstra, Robert L.

1998-04-14

Method and apparatus for making metallic powder particles wherein a metallic melt is atomized by a rotating disk or other atomizer at an atomizing location in a manner to form molten droplets moving in a direction away from said atomizing location. The atomized droplets pass through a series of thin liquid quenching sheets disposed in succession about the atomizing location with each successive quenching sheet being at an increasing distance from the atomizing location. The atomized droplets are incrementally cooled and optionally passivated as they pass through the series of liquid quenching sheets without distorting the atomized droplets from their generally spherical shape. The atomized, cooled droplets can be received in a chamber having a collection wall disposed outwardly of the series of liquid quenching sheets. A liquid quenchant can be flowed proximate the chamber wall to carry the cooled atomized droplets to a collection chamber where atomized powder particles and the liquid quenchant are separated such that the liquid quenchant can be recycled.

Atomizer with liquid spray quenching

DOEpatents

Anderson, I.E.; Osborne, M.G.; Terpstra, R.L.

1998-04-14

Method and apparatus are disclosed for making metallic powder particles wherein a metallic melt is atomized by a rotating disk or other atomizer at an atomizing location in a manner to form molten droplets moving in a direction away from said atomizing location. The atomized droplets pass through a series of thin liquid quenching sheets disposed in succession about the atomizing location with each successive quenching sheet being at an increasing distance from the atomizing location. The atomized droplets are incrementally cooled and optionally passivated as they pass through the series of liquid quenching sheets without distorting the atomized droplets from their generally spherical shape. The atomized, cooled droplets can be received in a chamber having a collection wall disposed outwardly of the series of liquid quenching sheets. A liquid quenchant can be flowed proximate the chamber wall to carry the cooled atomized droplets to a collection chamber where atomized powder particles and the liquid quenchant are separated such that the liquid quenchant can be recycled. 6 figs.

Comparison of analytical performances of inductively coupled plasma mass spectrometry and inductively coupled plasma atomic emission spectrometry for trace analysis of bismuth and bismuth oxide

NASA Astrophysics Data System (ADS)

Medvedev, Nickolay S.; Shaverina, Anastasiya V.; Tsygankova, Alphiya R.; Saprykin, Anatoly I.

2018-04-01

The paper presents а comparison of analytical performances of inductively coupled plasma mass spectrometry (ICP-MS) and inductively coupled plasma atomic emission spectrometry (ICP-AES) for trace analysis of high purity bismuth and bismuth oxide. Matrix effects in the ICP-MS and ICP-AES methods were studied as a function of Bi concentration, ICP power and nebulizer flow rate. For ICP-MS the strong dependence of the matrix effects versus the atomic mass of analytes was observed. For ICP-AES the minimal matrix effects were achieved for spectral lines of analytes with low excitation potentials. The optimum degree of sample dilution providing minimum values of the limits of detection (LODs) was chosen. Both methods let us to reach LODs from n·10-7 to n·10-4 wt% for more than 50 trace elements. For most elements the LODs of ICP-MS were lower in comparison to ICP-AES. Validation of accuracy of the developed techniques was performed by "added-found" experiments and by comparison of the results of ICP-MS and ICP-AES analysis of high-purity bismuth oxide.

High-speed imaging optical techniques for shockwave and droplets atomization analysis

NASA Astrophysics Data System (ADS)

Slangen, Pierre R.; Lauret, Pierre; Heymes, Frederic; Aprin, Laurent; Lecysyn, Nicolas

2016-12-01

Droplets atomization by shockwave can act as a consequence in domino effects on an industrial facility: aggression of a storage tank (projectile from previous event, for example) can cause leakage of hazardous material (toxic and flammable). As the accident goes on, a secondary event can cause blast generation, impacting the droplets and resulting in their atomization. Therefore, exchange surface increase impacts the evaporation rate. This can be an issue in case of dispersion of such a cloud. The experiments conducted in the lab generate a shockwave with an open-ended shock tube to break up liquid droplets. As the expected shockwave speed is about 400 m/s (˜Mach 1.2), the interaction with falling drops is very short. High-speed imaging is performed at about 20,000 fps. The shockwave is measured using both overpressure sensors: particle image velocimetry and pure in line shadowgraphy. The size of fragmented droplets is optically measured by direct shadowgraphy simultaneously in different directions. In these experiments, secondary breakups of a droplet into an important number of smaller droplets from the shockwave-induced flow are shown. The results of the optical characterizations are discussed in terms of shape, velocity, and size.

Copper Vapor Generator

DTIC Science & Technology

1974-09-01

flow. A volumetric quench.ng agent should quench the lower laser level m a t.me ᝺^ sec without mterfenng w.th the excitation process. A high-speed...quenchtng agent should not ^" »ff. AlLu^ A« Ire Imon gases do not appear promrsmg. there are some other more complex posstb.hues st.ll to be pursued...dimension along the How). Unless a volumetric quenching agent is discovered and employed, those copper atoms which contributed to the previous laser

Eutectic structures in friction spot welding joint of aluminum alloy to copper

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shen, Junjun, E-mail: junjun.shen@hzg.de; Suhuddin, Uceu F. H.; Cardillo, Maria E. B.

2014-05-12

A dissimilar joint of AA5083 Al alloy and copper was produced by friction spot welding. The Al-MgCuAl{sub 2} eutectic in both coupled and divorced manners were found in the weld. At a relatively high temperature, mass transport of Cu due to plastic deformation, material flow, and atomic diffusion, combined with the alloy system of AA5083 are responsible for the ternary eutectic melting.

Dramatic nano-fluidic properties of carbon nanotube membranes as a platform for protein channel mimetics

NASA Astrophysics Data System (ADS)

Hinds, Bruce

2013-03-01

Carbon nanotubes have three key attributes that make them of great interest for novel membrane applications: 1) atomically flat graphite surface allows for ideal fluid slip boundary conditions and extremely fast flow rates 2) the cutting process to open CNTs inherently places functional chemistry at CNT core entrance for chemical selectivity and 3) CNT are electrically conductive allowing for electrochemical reactions and application of electric fields gradients at CNT tips. Pressure driven flux of a variety of solvents (H2O, hexane, decane ethanol, methanol) are 4-5 orders of magnitude higher than conventional Newtonian flow [Nature 2005, 438, 44] due to atomically flat graphite planes inducing nearly ideal slip conditions. However this is eliminated with selective chemical functionalization [ACS Nano 2011 5(5) 3867-3877] needed to give chemical selectivity. These unique properties allow us to explore the hypothesis of producing ``Gatekeeper'' membranes that mimic natural protein channels to actively pump through rapid nm-scale channels. With anionic tip functionality strong electroosmotic flow is induced by unimpeded cation flow with similar 10,000 fold enhancements [Nature Nano 2012 7(2) 133-39]. With enhanced power efficiency, carbon nanotube membranes were employed as the active element of a switchable transdermal drug delivery device that can facilitate more effective treatments of drug abuse and addiction. Recently methods to deposit Pt monolayers on CNT surface have been developed making for highly efficient catalytic platforms. Discussed are other applications of CNT protein channel mimetics, for large area robust engineering platforms, including water purification, flow battery energy storage, and biochemical/biomass separations. DOE EPSCoR (DE-FG02-07ER46375) and DARPA, W911NF-09-1-0267

Stepwise Hydrogen Atom and Proton Transfers in Dioxygen Reduction by Aryl-Alcohol Oxidase.

PubMed

Carro, Juan; Ferreira, Patricia; Martínez, Angel T; Gadda, Giovanni

2018-03-20

The mechanism of dioxygen reduction by the flavoenzyme aryl-alcohol oxidase was investigated with kinetic isotope, viscosity, and pL (pH/pD) effects in rapid kinetics experiments by stopped-flow spectrophotometry of the oxidative half-reaction of the enzyme. Double mixing of the enzyme in a stopped-flow spectrophotometer with [α- 2 H 2 ]- p-methoxybenzyl alcohol and oxygen at varying aging times established a slow rate constant of 0.0023 s -1 for the wash-out of the D atom from the N5 atom of the reduced flavin. Thus, the deuterated substrate could be used to probe the cleavage of the N-H bond of the reduced flavin in the oxidative half-reaction. A significant and pH-independent substrate kinetic isotope effect (KIE) of 1.5 between pH 5.0 and 8.0 demonstrated that H transfer is partially limiting the oxidative half-reaction of the enzyme; a negligible solvent KIE of 1.0 between pD 5.0 and 8.0 proved a fast H + transfer reaction that does not contribute to determining the flavin oxidation rates. Thus, a mechanism for dioxygen reduction in which the H atom originating from the reduced flavin and a H + from a solvent exchangeable site are transferred in separate kinetic steps is proposed. The spectroscopic and kinetic data presented also showed a lack of stabilization of transient flavin intermediates. The substantial differences in the mechanistic details of O 2 reduction by aryl-alcohol oxidase with respect to other alcohol oxidases like choline oxidase, pyranose 2-oxidase, and glucose oxidase further demonstrate the high level of versatility of the flavin cofactor in flavoenzymes.

Odd nitrogen production by meteoroids

NASA Technical Reports Server (NTRS)

Park, C.; Menees, G. P.

1978-01-01

The process by which odd nitrogen species (atomic nitrogen and nitric oxide) are formed during atmospheric entry of meteoroids is analyzed theoretically. An ablating meteoroid is assumed to be a point source of mass with a continuum regime evolving in its wake. The amounts of odd nitrogen species, produced by high-temperature reactions of air in the continuum wake, are calculated by numerical integration of chemical rate equations. Flow properties are assumed to be uniform across the wake, and 29 reactions involving five neutral species and five singly ionized species are considered, as well as vibrational and electron temperature nonequilibrium phenomena. The results, when they are summed over the observed mass, velocity, and entry-angle distribution of meteoroids, provide odd-nitrogen-species annual global production rates as functions of altitude. The peak production of nitric oxide is found to occur at an altitude of about 85 km; atomic nitrogen production peaks at about 95 km. The total annual rate for nitric oxide is 40 million kg; for atomic nitrogen it is 170 million kg.

Vibrational Energy Transfer from Heme through Atomic Contacts in Proteins.

PubMed

Yamashita, Satoshi; Mizuno, Misao; Tran, Duy Phuoc; Dokainish, Hisham M; Kitao, Akio; Mizutani, Yasuhisa

2018-05-10

A pathway of vibrational energy flow in myoglobin was studied by time-resolved anti-Stokes ultraviolet resonance Raman spectroscopy combined with site-directed mutagenesis. Our previous study suggested that atomic contacts in proteins provide the dominant pathway for energy transfer while covalent bonds do not. In the present study, we directly examined the contributions of covalent bonds and atomic contacts to the pathway of vibrational energy flow by comparing the anti-Stokes resonance Raman spectra of two myoglobin mutants: one lacked a covalent bond between heme and the polypeptide chain and the other retained the intact bond. The two mutants showed no significant difference in temporal changes in the anti-Stokes Raman intensities of the tryptophan bands, implying that the dominant channel of vibrational energy transfer is not through the covalent bond but rather through van der Waals atomic contacts between heme and the protein moiety. The obtained insights contribute to our general understanding of energy transfer in the condensed phase.

Behavior and dynamics of bubble breakup in gas pipeline leaks and accidental subsea oil well blowouts.

PubMed

Wang, Binbin; Socolofsky, Scott A; Lai, Chris C K; Adams, E Eric; Boufadel, Michel C

2018-06-01

Subsea oil well blowouts and pipeline leaks release oil and gas to the environment through vigorous jets. Predicting the breakup of the released fluids in oil droplets and gas bubbles is critical to predict the fate of petroleum compounds in the marine water column. To predict the gas bubble size in oil well blowouts and pipeline leaks, we observed and quantified the flow behavior and breakup process of gas for a wide range of orifice diameters and flow rates. Flow behavior at the orifice transitions from pulsing flow to continuous discharge as the jet crosses the sonic point. Breakup dynamics transition from laminar to turbulent at a critical value of the Weber number. Very strong pure gas jets and most gas/liquid co-flowing jets exhibit atomization breakup. Bubble sizes in the atomization regime scale with the jet-to-plume transition length scale and follow -3/5 power-law scaling for a mixture Weber number. Copyright © 2018 Elsevier Ltd. All rights reserved.

Total arsenic and selenium analysis in Marcellus shale, high-salinity water, and hydrofracture flowback wastewater.

PubMed

Balaba, Ronald S; Smart, Ronald B

2012-11-01

Trace levels of arsenic and selenium can be toxic to living organisms yet their quantitation in high ionic strength or high salinity aqueous media is difficult due to the matrix interferences which can either suppress or enhance the analyte signal. A modified thiol cotton fiber (TCF) method employing lower flow rates and centrifugation has been used to remove the analyte from complex aqueous media and minimize the matrix interferences. This method has been tested using a USGS (SGR-1b) certified reference shale. It has been used to analyze Marcellus shale samples following microwave digestion as well as spiked samples of high salinity water (HSW) and flow back wastewater (WRF6) obtained from an actual gas well drilling operation. Quantitation of arsenic and selenium is carried out by graphite furnace atomic spectroscopy (GFAAS). Extraction of arsenic and selenium from Marcellus shale exposed to HSW and WRF6 for varying lengths of time is also reported. Copyright © 2012 Elsevier Ltd. All rights reserved.

Hot-electron-mediated surface chemistry: toward electronic control of catalytic activity.

PubMed

Park, Jeong Young; Kim, Sun Mi; Lee, Hyosun; Nedrygailov, Ievgen I

2015-08-18

Energy dissipation at surfaces and interfaces is mediated by excitation of elementary processes, including phonons and electronic excitation, once external energy is deposited to the surface during exothermic chemical processes. Nonadiabatic electronic excitation in exothermic catalytic reactions results in the flow of energetic electrons with an energy of 1-3 eV when chemical energy is converted to electron flow on a short (femtosecond) time scale before atomic vibration adiabatically dissipates the energy (in picoseconds). These energetic electrons that are not in thermal equilibrium with the metal atoms are called "hot electrons". The detection of hot electron flow under atomic or molecular processes and understanding its role in chemical reactions have been major topics in surface chemistry. Recent studies have demonstrated electronic excitation produced during atomic or molecular processes on surfaces, and the influence of hot electrons on atomic and molecular processes. We outline research efforts aimed at identification of the intrinsic relation between the flow of hot electrons and catalytic reactions. We show various strategies for detection and use of hot electrons generated by the energy dissipation processes in surface chemical reactions and photon absorption. A Schottky barrier localized at the metal-oxide interface of either catalytic nanodiodes or hybrid nanocatalysts allows hot electrons to irreversibly transport through the interface. We show that the chemicurrent, composed of hot electrons excited by the surface reaction of CO oxidation or hydrogen oxidation, correlates well with the turnover rate measured separately by gas chromatography. Furthermore, we show that hot electron flows generated on a gold thin film by photon absorption (or internal photoemission) can be amplified by localized surface plasmon resonance. The influence of hot charge carriers on the chemistry at the metal-oxide interface are discussed for the cases of Au, Ag, and Pt nanoparticles on oxide supports and Pt-CdSe-Pt nanodumbbells. We show that the accumulation or depletion of hot electrons on metal nanoparticles, in turn, can also influence catalytic reactions. Mechanisms suggested for hot-electron-induced chemical reactions on a photoexcited plasmonic metal are discussed. We propose that the manipulation of the flow of hot electrons by changing the electrical characteristics of metal-oxide and metal-semiconductor interfaces can give rise to the intriguing capability of tuning the catalytic activity of hybrid nanocatalysts.

Simple interface of high-performance liquid chromatography-atomic fluorescence spectrometry hyphenated system for speciation of mercury based on photo-induced chemical vapour generation with formic acid in mobile phase as reaction reagent.

PubMed

Yin, Yongguang; Liu, Jingfu; He, Bin; Shi, Jianbo; Jiang, Guibin

2008-02-15

Photo-induced chemical vapour generation (CVG) with formic acid in mobile phase as reaction reagent was developed as interface to on-line couple HPLC with atomic fluorescence spectrometry for the separation and determination of inorganic mercury, methylmercury (MeHg), ethylmercury (EtHg) and phenylmercury (PhHg). In the developed procedure, formic acid in mobile phase was used to decompose organomercuries and reduce Hg(2+) to mercury cold vapour under UV irradiation. Therefore, no post-column reagent was used and the flow injection system in traditional procedure is omitted. A number of operating parameters including pH of mobile phase, concentration of formate, flow rate of mobile phase, length of PTFE reaction coil, flow rate of carrier gas and Na(2)S(2)O(3) in sample matrix were optimized. The limits of detection at the optimized conditions were 0.085, 0.033, 0.029 and 0.038 microg L(-1) for inorganic mercury, MeHg, EtHg and PhHg, respectively. The developed method was validated by determination of certified reference material DORM-2 and was further applied in analyses of seafood samples from Yantai port, China. The UV-CVG with formic acid simplifies the instrumentation and reduces the analytical cost significantly.

[Determination of high concentrations of rubidium chloride by ICP-OES].

PubMed

Zhong, Yuan; Sun, Bai; Li, Hai-jun; Wang, Tao; Li, Wu; Song, Peng-sheng

2015-01-01

The method of ICP-OES for the direct determination of high content of rubidium in rubidium chloride solutions was studied through mass dilution method and optimizing parameters of the instrument in the present paper. It can reduce the times of dilution and the error introduced by the dilution, and improve the accuracy of determination results of rubidium. Through analyzing the sensitivity of the three detection spectral lines for rubidium ion, linearly dependent coefficient and the relative errors of the determination results, the spectral line of Rb 780. 023 nm was chosen as the most suitable wavelength to measure the high content of rubidium in the rubidium chloride solutions. It was found that the instrument parameters of ICP-OES such as the atomizer flow, the pump speed and the high-frequency power are the major factors for the determination of rubidium ion in the rubidium chloride solutions. As we know instrument parameters of ICP-OES have an important influence on the atomization efficiency as well as the emissive power of the spectral lines of rubidium, they are considered as the significant factors for the determination of rubidium. The optimization parameters of the instrument were obtained by orthogonal experiments and further single factor experiment, which are 0. 60 L . min-1 of atomizer flow, 60 r . min-1 of pump speed, and 1 150 W of high-frequency power. The same experiments were repeated a week later with the optimization parameters of the instrument, and the relative errors of the determination results are less than 0. 5% when the concentration of rubidium chloride ranged from 0. 09% to 0. 18%. As the concentration of rubidium chloride is 0. 06%, the relative errors of the determination results are -1. 7%. The determination of lithium chloride and potassium chloride in the high concentration of the aqueous solutions was studied under the condition of similar instrument parameters. It was found by comparison that the determination results of lithium chloride are better than that of potassium chloride and rubidium chloride. The method of ICP-OES used for determination of high content of rubidium is fast and simple for operation, and the results are accurate. It is suitable for studying the equilibrium in the salt-water system containing rubidium and for analysis of products of rubidium with high content.

Liquid jet breakup regimes at supercritical pressures

DOE PAGES

Oefelein, Joseph C.; Dahms, Rainer Norbert Uwe

2015-07-23

Previously, a theory has been presented that explains how discrete vapor–liquid interfaces become diminished at certain high-pressure conditions in a manner that leads to well known qualitative trends observed from imaging in a variety of experiments. Rather than surface tension forces, transport processes can dominate over relevant ranges of conditions. In this paper, this framework is now generalized to treat a wide range of fuel-oxidizer combinations in a manner consistent with theories of capillary flows and extended corresponding states theory. Different flow conditions and species-specific molecular properties are shown to produce distinct variations of interfacial structures and local free molecularmore » paths. These variations are shown to occur over the operating ranges in a variety of propulsion and power systems. Despite these variations, the generalized analysis reveals that the envelope of flow conditions at which the transition from classical sprays to diffusion-dominated mixing occurs exhibits a characteristic shape for all liquid–gas combinations. As a result, for alkane-oxidizer mixtures, it explains that these conditions shift to higher pressure flow conditions with increasing carbon number and demonstrates that, instead of widely assumed classical spray atomization, diffusion-dominated mixing may occur under relevant high-pressure conditions in many modern devices.« less

Simulation of RCC Crack Growth Due to Carbon Oxidation in High-Temperature Gas Environments

NASA Technical Reports Server (NTRS)

Titov, E. V.; Levin, D. A.; Picetti, Donald J.; Anderson, Brian P.

2009-01-01

The carbon wall oxidation technique coupled with a CFD technique was employed to study the flow in the expanding crack channel caused by the oxidation of the channel carbon walls. The recessing 3D surface morphing procedure was developed and tested in comparison with the arcjet experimental results. The multi-block structured adaptive meshing was used to model the computational domain changes due to the wall recession. Wall regression rates for a reinforced carbon-carbon (RCC) samples, that were tested in a high enthalpy arcjet environment, were computationally obtained and used to assess the channel expansion. The test geometry and flow conditions render the flow regime as the transitional to continuum, therefore Navier-Stokes gas dynamic approach with the temperature jump and velocity slip correction to the boundary conditions was used. The modeled mechanism for wall material loss was atomic oxygen reaction with bare carbon. The predicted channel growth was found to agree with arcjet observations. Local gas flow field results were found to affect the oxidation rate in a manner that cannot be predicted by previous mass loss correlations. The method holds promise for future modeling of materials gas-dynamic interactions for hypersonic flight.

Determination of mercury in agroindustrial samples by flow-injection cold vapor atomic absorption spectrometry using ion exchange and reductive elution.

PubMed

Gomes Neto, J A; Zara, L F; Rocha, J C; Santos, A; Dakuzaku, C S; Nóbrega, J A

2000-03-06

A flow-injection system with a Chelite-S(R) cationic resin packed minicolumn is proposed for the determination of trace levels of mercury in agroindustrial samples by cold vapor atomic absorption spectrometry. Improved sensitivity and selectivity are attained since mercuric ions are on-line concentrated whereas other potential interferents are discarded. With on-line reductive elution procedure, concentrated hydrochloric acid could be replaced by 10% w/v SnCl(2), in 6 M HCl as eluent. The reversed-intermittent stream either carries the atomic mercury to the flow cell in the forward direction or removes the residue from reactor/gas-liquid separator to a discarding flask in the opposite direction. Concentration and volume of reagent, acidity, flow rates, commutation times and potential interfering species were investigated. For 120 s preconcentration time, the proposed system handles about 25 samples h(-1) (50.0-500 ng l(-1)), consuming about 10 ml sample and 5 mg SnCl(2) per determination. The detection limit is 0.8 ng l(-1) and the relative standard deviation (RSD) (n=12) of a 76.7 ng l(-1) sample is about 5%. Results are in agreement with certified value of standard materials at 95% confidence level and good recoveries (97-128%) of spiked samples were found.

A high precision gas flow cell for performing in situ neutron studies of local atomic structure in catalytic materials

DOE PAGES

Olds, Daniel; Page, Katharine; Paecklar, Arnold A.; ...

2017-03-17

Gas-solid interfaces enable a multitude of industrial processes, including heterogeneous catalysis; however, there are few methods available for studying the structure of this interface under operating conditions. Here, we present a new sample environment for interrogating materials under gas-flow conditions using time-of-flight neutron scattering under both constant and pulse probe gas flow. Outlined are descriptions of the gas flow cell and a commissioning example using the adsorption of N 2 by Ca-exchanged zeolite-X (Na 78–2xCa xAl 78Si 144O 384,x ≈ 38). We demonstrate sensitivities to lattice contraction and N 2 adsorption sites in the structure, with both static gas loadingmore » and gas flow. A steady-state isotope transient kinetic analysis of N 2 adsorption measured simultaneously with mass spectrometry is also demonstrated. In the experiment, the gas flow through a plugged-flow gas-solid contactor is switched between 15N 2 and 14N 2 isotopes at a temperature of 300 K and a constant pressure of 1 atm; the gas flow and mass spectrum are correlated with the structure factor determined from event-based neutron total scattering. As a result, available flow conditions, sample considerations, and future applications are discussed.« less

UF6 Density and Mass Flow Measurements for Enrichment Plants using Acoustic Techniques

DOE Office of Scientific and Technical Information (OSTI.GOV)

Good, Morris S.; Smith, Leon E.; Warren, Glen A.

A key enabling capability for enrichment plant safeguards being considered by the International Atomic Energy Agency (IAEA) is high-accuracy, noninvasive, unattended measurement of UF6 gas density and mass flow rate. Acoustic techniques are currently used to noninvasively monitor gas flow in industrial applications; however, the operating pressures at gaseous centrifuge enrichment plants (GCEPs) are roughly two orders magnitude below the capabilities of commercial instrumentation. Pacific Northwest National Laboratory is refining acoustic techniques for estimating density and mass flow rate of UF6 gas in scenarios typical of GCEPs, with the goal of achieving 1% measurement accuracy. Proof-of-concept laboratory measurements using amore » surrogate gas for UF6 have demonstrated signatures sensitive to gas density at low operating pressures such as 10–50 Torr, which were observed over the background acoustic interference. Current efforts involve developing a test bed for conducting acoustic measurements on flowing SF6 gas at representative flow rates and pressures to ascertain the viability of conducting gas flow measurements under these conditions. Density and flow measurements will be conducted to support the evaluation. If successful, the approach could enable an unattended, noninvasive approach to measure mass flow in unit header pipes of GCEPs.« less

Modeling aerosols formed in the ring - pack of reciprocating piston

NASA Astrophysics Data System (ADS)

Dallstream, Brian Ellis

The hydrocarbon emissions of an internal combustion engine are directly correlated with the engine's oil consumption. This oil consumption is associated with reverse blow-by, a condition in which gases flow past the ring-pack from the crankcase to the combustion chamber. This reverse blow-by breaks down the oil film on the cylinder walls and entrains oil particles in the gas flow during the downstroke of the piston. In this project a numerical model was developed that accurately describes the formation of aerosols in the ring pack by simulating the mechanisms by which oil globules are broken up, atomized, and entrained in a gas flowing through an orifice. The results of this numerical model are in good agreement with experimental values. Thus, this numerical model gives insight into the parameters that govern oil consumption. A discussion is also presented regarding the general applications of atomization and how past researchers have developed and advanced the theories of atomization.Included in this discussion is an introduction to past models of oil consumption and the conditions needed for aerosols to form within the ring-pack of a piston.

The Helium Warm Breeze in IBEX Observations As a Result of Charge-exchange Collisions in the Outer Heliosheath

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bzowski, Maciej; Kubiak, Marzena A.; Czechowski, Andrzej

2017-08-10

We simulated the signal due to neutral He atoms, observed by the Interstellar Boundary Explorer ( IBEX ), assuming that charge-exchange collisions between neutral He atoms and He{sup +} ions operate everywhere between the heliopause and a distant source region in the local interstellar cloud, where the neutral and charged components are in thermal equilibrium. We simulated several test cases of the plasma flow within the outer heliosheath (OHS) and investigated the signal generation for plasma flows both in the absence and in the presence of the interstellar magnetic field (ISMF). We found that a signal in the portion ofmore » IBEX data identified as being due to the Warm Breeze (WB) does not arise when a homogeneous plasma flow in front of the heliopause is assumed, but it appears immediately when any reasonable disturbance in its flow due to the presence of the heliosphere is assumed. We obtained a good qualitative agreement between the data selected for comparison and the simulations for a model flow with the velocity vector of the unperturbed gas and the direction and intensity of magnetic field adopted from recent determinations. We conclude that direct-sampling observations of neutral He atoms at 1 au from the Sun are a sensitive tool for investigating the flow of interstellar matter in the OHS, that the WB is indeed the secondary population of interstellar helium, which was hypothesized earlier, and that the WB signal is consistent with the heliosphere distorted from axial symmetry by the ISMF.« less

Flaw-induced plastic-flow dynamics in bulk metallic glasses under tension

PubMed Central

Chen, S. H.; Yue, T. M.; Tsui, C. P.; Chan, K. C.

2016-01-01

Inheriting amorphous atomic structures without crystalline lattices, bulk metallic glasses (BMGs) are known to have superior mechanical properties, such as high strength approaching the ideal value, but are susceptible to catastrophic failures. Understanding the plastic-flow dynamics of BMGs is important for achieving stable plastic flow in order to avoid catastrophic failures, especially under tension, where almost all BMGs demonstrate limited plastic flow with catastrophic failure. Previous findings have shown that the plastic flow of BMGs displays critical dynamics under compression tests, however, the plastic-flow dynamics under tension are still unknown. Here we report that power-law critical dynamics can also be achieved in the plastic flow of tensile BMGs by introducing flaws. Differing from the plastic flow under compression, the flaw-induced plastic flow under tension shows an upward trend in the amplitudes of the load drops with time, resulting in a stable plastic-flow stage with a power-law distribution of the load drop. We found that the flaw-induced plastic flow resulted from the stress gradients around the notch roots, and the stable plastic-flow stage increased with the increase of the stress concentration factor ahead of the notch root. The findings are potentially useful for predicting and avoiding the catastrophic failures in tensile BMGs by tailoring the complex stress fields in practical structural-applications. PMID:27779221

Structural relaxation driven increase in elastic modulus for a bulk metallic glass

DOE Office of Scientific and Technical Information (OSTI.GOV)

Arora, Harpreet Singh; Aditya, Ayyagari V.; Mukherjee, Sundeep, E-mail: sundeep.mukherjee@unt.edu

2015-01-07

The change in elastic modulus as a function of temperature was investigated for a zirconium-based bulk metallic glass. High temperature nano-indentation was done over a wide temperature range from room temperature to the glass-transition. At higher temperature, there was a transition from inhomogeneous to homogeneous deformation, with a decrease in serrated flow and an increase in creep displacement. Hardness was found to decrease, whereas elastic modulus was found to increase with temperature. The increase in elastic modulus for metallic glass at higher temperature was explained by diffusive rearrangement of atoms resulting in free volume annihilation. This is in contrast tomore » elastic modulus increase with temperature for silicate glasses due to compaction of its open three dimensional coordinated structure without any atomic diffusion.« less

Laser manipulation of atomic and molecular flows

NASA Astrophysics Data System (ADS)

Lilly, Taylor C.

The continuing advance of laser technology enables a range of broadly applicable, laser-based flow manipulation techniques. The characteristics of these laser-based flow manipulations suggest that they may augment, or be superior to, such traditional electro-mechanical methods as ionic flow control, shock tubes, and small scale wind tunnels. In this study, methodology was developed for investigating laser flow manipulation techniques, and testing their feasibility for a number of aerospace, basic physics, and micro technology applications. Theories for laser-atom and laser-molecule interactions have been under development since the advent of laser technology. The theories have yet to be adequately integrated into kinetic flow solvers. Realizing this integration would greatly enhance the scaling of laser-species interactions beyond the realm of ultra-cold atomic physics. This goal was realized in the present study. A representative numerical investigation, of laser-based neutral atomic and molecular flow manipulations, was conducted using near-resonant and non-resonant laser fields. To simulate the laser interactions over a range of laser and flow conditions, the following tools were employed: a custom collisionless gas particle trajectory code and a specifically modified version of the Direct Simulation Monte Carlo statistical kinetic solver known as SMILE. In addition to the numerical investigations, a validating experiment was conducted. The experimental results showed good agreement with the numerical simulations when experimental parameters, such as finite laser line width, were taken into account. Several areas of interest were addressed: laser induced neutral flow steering, collimation, direct flow acceleration, and neutral gas heating. Near-resonant continuous wave laser, and non-resonant pulsed laser, interactions with cesium and nitrogen were simulated. These simulations showed trends and some limitations associated with these interactions, used for flow steering and collimation. The use of one of these interactions, the induced dipole force, was extended beyond a single Gaussian laser field. The interference patterns associated with counter-propagating laser fields, or "optical lattices," were shown to be capable of both direct species acceleration and gas heating. This study resulted in predictions for a continuous, resonant laser-cesium flow with accelerations of 106 m/s2. For this circumstance, a future straightforward proof of principle experiment has been identified. To demonstrate non-resonant gas heating, a series of pulsed optical lattices were simulated interacting with neutral non-polar species. An optimum time between pulses was identified as a function of the collisional relaxation time. Using the optimum time between pulses, molecular nitrogen simulations showed an increase in gas temperature from 300 K to 2470 K at 1 atm, for 50 successive optical lattice pulses. A second proof of principle experiment was identified for future investigation.

Can sample treatments based on advanced oxidation processes assisted by high-intensity focused ultrasound be used for toxic arsenic determination in human urine by flow-injection hydride-generation atomic absorption spectrometry?

PubMed

Correia, A; Galesio, M; Santos, H; Rial-Otero, R; Lodeiro, C; Oehmen, A; Conceição, Antonio C L; Capelo, J L

2007-05-15

Two advanced oxidation processes (AOPs), based on high-intensity focused ultrasound (HIFU), namely, KMnO(4)/HCl/HIFU and H(2)O(2)/HCl/HIFU are studied and compared for the determination of toxic arsenic in human urine [As(III)+As(V)+MMA+DMA] by flow-injection hydride-generation atomic absorption spectrometry (FI-HG-AAS). The KMnO(4)/HCl/HIFU procedure was found to be adequate for organic matter degradation in human urine. l-cysteine (letra minuscula) was used for As reduction to the trivalent state. The new procedure was assessed with seven urines certified in different As species. Results revealed that with KMnO(4)/HCl/HIFU plus l-cysteine the toxic arsenic can be accurately measured in human urine whilst the H(2)O(2)/HCl/HIFU procedure underestimates toxic As. DMA and MMA degradation in urine were observed, due to the effects of the ultrasonic field. Recoveries for As(III), As(V), MMA and DMA were within the certified ranges. Arsenobetaine was not degraded by the AOPs. The new procedure adheres well to the principles of analytical minimalism: (i) low reagent consumption, (ii) low reagent concentration, (iii) low waste production and (iv) low amount of time required for sample preparation and analysis.

Characterization of protein immobilization on nanoporous gold using atomic force microscopy and scanning electron microscopy†

PubMed Central

Tan, Yih Horng; Schallom, John R.; Ganesh, N. Vijaya; Fujikawa, Kohki; Demchenko, Alexei V.

2011-01-01

Nanoporous gold (NPG), made by dealloying low carat gold alloys, is a relatively new nanomaterial finding application in catalysis, sensing, and as a support for biomolecules. NPG has attracted considerable interest due to its open bicontinuous structure, high surface-to-volume ratio, tunable porosity, chemical stability and biocompatibility. NPG also has the attractive feature of being able to be modified by self-assembled monolayers. Here we use scanning electron microscopy (SEM) and atomic force microscopy (AFM) to characterize a highly efficient approach for protein immobilization on NPG using N-hydroxysuccinimide (NHS) ester functionalized self-assembled monolayers on NPG with pore sizes in the range of tens of nanometres. Comparison of coupling under static versus flow conditions suggests that BSA (Bovine Serum Albumin) and IgG (Immunoglobulin G) can only be immobilized onto the interior surfaces of free standing NPG monoliths with good coverage under flow conditions. AFM is used to examine protein coverage on both the exterior and interior of protein modified NPG. Access to the interior surface of NPG for AFM imaging is achieved using a special procedure for cleaving NPG. AFM is also used to examine BSA immobilized on rough gold surfaces as a comparative study. In principle, the general approach described should be applicable to many enzymes, proteins and protein complexes since both pore sizes and functional groups present on the NPG surfaces are controllable. PMID:21750834

Spectroscopic investigations of microwave generated plasmas

NASA Technical Reports Server (NTRS)

Hawley, Martin C.; Haraburda, Scott S.; Dinkel, Duane W.

1991-01-01

The study deals with the plasma behavior as applied to spacecraft propulsion from the perspective of obtaining better design and modeling capabilities. The general theory of spectroscopy is reviewed, and existing methods for converting emission-line intensities into such quantities as temperatures and densities are outlined. Attention is focused on the single-atomic-line and two-line radiance ratio methods, atomic Boltzmann plot, and species concentration. Electronic temperatures for a helium plasma are determined as a function of pressure and a gas-flow rate using these methods, and the concentrations of ions and electrons are predicted from the Saha-Eggert equations using the sets of temperatures obtained as a function of the gas-flow rate. It is observed that the atomic Boltzmann method produces more reliable results for the electronic temperature, while the results obtained from the single-line method reflect the electron temperatures accurately.

Pulsed electrothermal thruster

NASA Technical Reports Server (NTRS)

Burton, Rodney L. (Inventor); Goldstein, Yeshayahu S. A. (Inventor); Tidman, Derek A. (Inventor); Winsor, Niels K. (Inventor)

1989-01-01

A plasma electrothermal thruster includes a capillary passage in which a plasma discharge is formed and directed out of an open end of the passage into a supersonic nozzle. Liquid supplied to the capillary passage becomes partially atomized to cool a confining surface of the passage. The plasma discharge is formed as the atomized liquid flows out of the open end into a supersonic equilibrium nozzle. The discharge can have a duration greater than the two way travel time of acoustic energy in the capillary to cause the plasma to flow continuously through the nozzle during the time of the discharge pulse.

Two-photon laser-induced fluorescence of atomic hydrogen in a diamond-depositing dc arcjet.

PubMed

Juchmann, Wolfgang; Luque, Jorge; Jeffries, Jay B

2005-11-01

Atomic hydrogen in the plume of a dc-arcjet plasma is monitored by use of two-photon excited laser-induced fluorescence (LIF) during the deposition of diamond film. The effluent of a dc-arc discharge in hydrogen and argon forms a luminous plume as it flows through a converging-diverging nozzle into a reactor. When a trace of methane (< 2%) is added to the flow in the diverging part of the nozzle, diamond thin film grows on a water-cooled molybdenum substrate from the reactive mixture. LIF of atomic hydrogen in the arcjet plume is excited to the 3S and 3D levels with two photons near 205 nm, and the subsequent fluorescence is observed at Balmer-alpha near 656 nm. Spatially resolved LIF measurements of atomic hydrogen are made as a function of the ratio of hydrogen to argon feedstock gas, methane addition, and reactor pressure. At lower reactor pressures, time-resolved LIF measurements are used to verify our collisional quenching correction algorithm. The quenching rate coefficients for collisions with the major species in the arcjet (Ar, H, and H2) do not change with gas temperature variations in the plume (T < 2300 K). Corrections of the LIF intensity measurements for the spatial variation of collisional quenching are important to determine relative distributions of the atomic hydrogen concentration. The relative atomic hydrogen concentrations measured here are calibrated with an earlier calorimetric determination of the feedstock hydrogen dissociation to provide quantitative hydrogen-atom concentration distributions.

Use of electrothermal atomic absorption spectrometry for size profiling of gold and silver nanoparticles.

PubMed

Panyabut, Teerawat; Sirirat, Natnicha; Siripinyanond, Atitaya

2018-02-13

Electrothermal atomic absorption spectrometry (ETAAS) was applied to investigate the atomization behaviors of gold nanoparticles (AuNPs) and silver nanoparticles (AgNPs) in order to relate with particle size information. At various atomization temperatures from 1400 °C to 2200 °C, the time-dependent atomic absorption peak profiles of AuNPs and AgNPs with varying sizes from 5 nm to 100 nm were examined. With increasing particle size, the maximum absorbance was observed at the longer time. The time at maximum absorbance was found to linearly increase with increasing particle size, suggesting that ETAAS can be applied to provide the size information of nanoparticles. With the atomization temperature of 1600 °C, the mixtures of nanoparticles containing two particle sizes, i.e., 5 nm tannic stabilized AuNPs with 60, 80, 100 nm citrate stabilized AuNPs, were investigated and bimodal peaks were observed. The particle size dependent atomization behaviors of nanoparticles show potential application of ETAAS for providing size information of nanoparticles. The calibration plot between the time at maximum absorbance and the particle size was applied to estimate the particle size of in-house synthesized AuNPs and AgNPs and the results obtained were in good agreement with those from flow field-flow fractionation (FlFFF) and transmission electron microscopy (TEM) techniques. Furthermore, the linear relationship between the activation energy and the particle size was observed. Copyright © 2017 Elsevier B.V. All rights reserved.

Adhesion and formation of microbial biofilms in complex microfluidic devices

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kumar, Aloke; Karig, David K; Neethirajan, Suresh

2012-01-01

Shewanella oneidensis is a metal reducing bacterium, which is of interest for bioremediation and clean energy applications. S. oneidensis biofilms play a critical role in several situations such as in microbial energy harvesting devices. Here, we use a microfluidic device to quantify the effects of hydrodynamics on the biofilm morphology of S. oneidensis. For different rates of fluid flow through a complex microfluidic device, we studied the spatiotemporal dynamics of biofilms, and we quantified several morphological features such as spatial distribution, cluster formation and surface coverage. We found that hydrodynamics resulted in significant differences in biofilm dynamics. The baffles inmore » the device created regions of low and high flow in the same device. At higher flow rates, a nonuniform biofilm develops, due to unequal advection in different regions of the microchannel. However, at lower flow rates, a more uniform biofilm evolved. This depicts competition between adhesion events, growth and fluid advection. Atomic force microscopy (AFM) revealed that higher production of extra-cellular polymeric substances (EPS) occurred at higher flow velocities.« less

Serrated Flow Behavior of Aisi 316l Austenitic Stainless Steel for Nuclear Reactors

NASA Astrophysics Data System (ADS)

Li, Qingshan; Shen, Yinzhong; Han, Pengcheng

2017-10-01

AISI 316L austenitic stainless steel is a candidate material for Generation IV reactors. In order to investigate the influence of temperature on serrated flow behavior, tensile tests were performed at temperatures ranging from 300 to 700 °C at an initial strain rate of 2×10-4 s-1. Another group of tensile tests were carried out at strain rates ranging from 1×10-4 to 1×10-2 s-1 at 600 °C to examine the influence of strain rates on serrated flow behavior. The steel exhibited serrated flow, suggesting the occurrence of dynamic strain ageing at 450-650°C. No plateau of yield stresses of the steel was observed at an initial strain rate of 2×10-4 s-1. The effective activation energy for serrated flow occurrence was calculated to be about 254.72 kJ/mol-1. Cr, Mn, Ni and Mo solute atoms are expected to be responsible for dynamic strain ageing at high temperatures of 450-650 °C in the steel.

Hydrogen-dominated plasma, due to silane depletion, for microcrystalline silicon deposition

DOE Office of Scientific and Technical Information (OSTI.GOV)

Howling, A. A.; Sobbia, R.; Hollenstein, Ch.

2010-07-15

Plasma conditions for microcrystalline silicon deposition generally require a high flux of atomic hydrogen, relative to SiH{sub {alpha}=0{yields}3} radicals, on the growing film. The necessary dominant partial pressure of hydrogen in the plasma is conventionally obtained by hydrogen dilution of silane in the inlet flow. However, a hydrogen-dominated plasma environment can also be obtained due to plasma depletion of the silane in the gas mixture, even up to the limit of pure silane inlet flow, provided that the silane depletion is strong enough. At first sight, it may seem surprising that the composition of a strongly depleted pure silane plasmamore » consists principally of molecular hydrogen, without significant contribution from the partial pressure of silane radicals. The aim here is to bring some physical insight by means of a zero-dimensional, analytical plasma chemistry model. The model is appropriate for uniform large-area showerhead reactors, as shown by comparison with a three-dimensional numerical simulations. The SiH{sub {alpha}} densities remain very low because of their rapid diffusion and surface reactivity, contributing to film growth which is the desired scenario for efficient silane utilization. Significant SiH{sub {alpha}} densities due to poor design of reactor and gas flow, on the other hand, would result in powder formation wasting silane. Conversely, hydrogen atoms are not deposited, but recombine on the film surface and reappear as molecular hydrogen in the plasma. Therefore, in the limit of extremely high silane depletion fraction (>99.9%), the silane density falls below the low SiH{sub {alpha}} densities, but only the H radical can eventually reach significant concentrations in the hydrogen-dominated plasma.« less

Development of the Seeding System Used for Laser Velocimeter Surveys of the NASA Low-Speed Centrifugal Compressor Flow Field

NASA Technical Reports Server (NTRS)

Wasserbauer, C. A.; Hathaway, M. D.

1994-01-01

Consideration is given to an atomizer-based system for distributing high-volume rates of polystyrene latex (PSL) seed material developed to support laser velocimeter investigations of the NASA Low-Speed Compressor flow field. Complete evaporation of the liquid carrier before the flow entering the compressor was of primary concern for the seeder system design. It is argued that the seed nozzle should incorporate a needle valve that can mechanically dislodge accumulated PSL seed material when the nozzle is turned off. Water is less expensive as the liquid carrier and should be used whenever adequate residence times are available to ensure complete evaporation. PSL agglomerates over time and needs to be mixed or blended before use. Arrangement of the spray nozzles needs to be adjustable to provide maximum seeding at the laser probe volume.

Detailed investigation of a vaporising fuel spray. Part 1: Experimental investigation of time averaged spray

NASA Technical Reports Server (NTRS)

Yule, A. J.; Seng, C. A.; Boulderstone, R.; Ungut, A.; Felton, P. G.; Chigier, N. A.

1980-01-01

A laser tomographic light scattering technique provides rapid and accurate high resolution measurements of droplet sizes, concentrations, and vaporization. Measurements using a computer interfaced thermocouple are presented and it is found that the potential exists for separating gas and liquid temperature measurements and diagnosing local spray density by in situ analysis of the response characteristics of the thermocouple. The thermocouple technique provides a convenient means for measuring mean gas velocity in both hot and cold two phase flows. The experimental spray is axisymmetric and has carefully controlled initial and boundary conditions. The flow is designed to give relatively insignificant transfer of momentum and mass from spray to air flow. The effects of (1) size-dependent droplet dispersion by the turbulence, (2) the initial spatial segregation of droplet sizes during atomization, and (3) the interaction between droplets and coherent large eddies are diagnosed.

Observation of dynamic atom-atom correlation in liquid helium in real space.

PubMed

Dmowski, W; Diallo, S O; Lokshin, K; Ehlers, G; Ferré, G; Boronat, J; Egami, T

2017-05-04

Liquid 4 He becomes superfluid and flows without resistance below temperature 2.17 K. Superfluidity has been a subject of intense studies and notable advances were made in elucidating the phenomenon by experiment and theory. Nevertheless, details of the microscopic state, including dynamic atom-atom correlations in the superfluid state, are not fully understood. Here using a technique of neutron dynamic pair-density function (DPDF) analysis we show that 4 He atoms in the Bose-Einstein condensate have environment significantly different from uncondensed atoms, with the interatomic distance larger than the average by about 10%, whereas the average structure changes little through the superfluid transition. DPDF peak not seen in the snap-shot pair-density function is found at 2.3 Å, and is interpreted in terms of atomic tunnelling. The real space picture of dynamic atom-atom correlations presented here reveal characteristics of atomic dynamics not recognized so far, compelling yet another look at the phenomenon.

Cryogenic spray vaporization in high-velocity helium, argon and nitrogen gasflows

NASA Technical Reports Server (NTRS)

Ingebo, Robert D.

1993-01-01

Effects of gas properties on cryogenic liquid-jet atomization in high-velocity helium, nitrogen, and argon gas flows were investigated. Volume median diameter, D(sub v.5e), data were obtained with a scattered-light scanning instrument. By calculating the change in spray drop size, -Delta D(sub v.5)(exp 2), due to droplet vaporization, it was possible to calculate D(sub v.5C). D(sub v.5C) is the unvaporized characteristic drop size formed at the fuel-nozzle orifice. This drop size was normalized with respect to liquid-jet diameter, D(sub O). It was then correlated with several dimensionless groups to give an expression for the volume median diameter of cryogenic LN2 sprays. This expression correlates drop size D(sub v.5c) with aerodynamic and liquid-surface forces so that it can be readily determined in the design of multiphase-flow propellant injectors for rocket combustors.

A numerical study on charging mechanism in leaky dielectric liquids inside the electrostatic atomizers

NASA Astrophysics Data System (ADS)

Kashir, Babak; Perri, Anthony; Yarin, Alexander L.; Mashayek, Farzad

2017-11-01

The charging of leaky dielectric liquids inside an electrostatic atomizer is studied numerically by developed codes based on OpenFOAM platform. Faradaic reactions are taken into account as the electrification mechanism. The impact of ionic finite size (steric terms) in high voltages is also investigated. The fundamental electrohydrodynamic understanding of the charging mechanism is aimed in the present work where the creation of polarized near-electrode layer and the movement of charges due to hydrodynamic flow are studied in conjunction with the solution of the Navier-Stokes equations. The case of a micro channel electrohydrodynamic flow subjected to two electrodes of the opposite polarity is considered as an example, with the goal to predict the resulting net charge at the exit. Even though the electrodes constitute a small portion of the channel wall, otherwise insulated, it is indicated that the channel length plays a dominant role in the discharging net charge. The ionic fluxes at the electrode surfaces are accounted through the Frumkin-Butler-Volmer relation found from the concurrent in-house experimental investigations. This projects was supported by National science Foundation (NSF) GOALI Grant CBET-1505276.

The effect of a miniature argon flow rate on the spectral characteristics of a direct current atmospheric pressure glow micro-discharge between an argon microjet and a small sized flowing liquid cathode

NASA Astrophysics Data System (ADS)

Jamróz, Piotr; Żyrnicki, Wiesław; Pohl, Paweł

2012-07-01

A stable direct current atmospheric pressure glow microdischarge (dc-μAPGD) was generated between a miniature Ar flow microjet and a small sized flowing liquid cathode. The microdischarge was operated in the open to air atmosphere. High energy species, including OH, NH, NO, N2, H, O and Ar were identified in the emission spectra of this microdischarge. Additionally, atomic lines of metals dissolved in water solutions were easily excited. The near cathode and the near anode zones of the microdischarge were investigated as a function of an Ar flow rate up to 300 sccm. The spectroscopic parameters, i.e., the excitation, the vibrational and the rotational temperatures as well as the electron number density, were determined in the near cathode and the near anode regions of the microdischarge. In the near cathode region, the rotational temperatures obtained for OH (2000-2600 K) and N2 bands (1600-1950 K) were significantly lower than the excitation temperatures of Ar (7400 K-7800 K) and H (11 000-15 500 K) atoms. Vibrational temperatures of N2, OH and NO varied from 3400 to 4000 K, from 2900 to 3400 K and from 2700 to 3000 K, respectively. In the near anode region, rotational temperatures of OH (350-1750 K) and N2 (400-1350 K) and excitation temperatures of Ar (5200-5500 K) and H (3600-12 600 K) atoms were lower than those measured in the near cathode region. The effect of the introduction of a liquid sample on the microdischarge radiation and spectroscopic parameters was also investigated in the near cathode zone. The electron number density was calculated from the Stark broadening of the Hβ line and equals to (0.25-1.1) × 1015 cm- 3 and (0.68-1.2) × 1015 cm- 3 in the near cathode and the near anode zones, respectively. The intensity of the Na I emission line and the signal to background ratio (SBR) of this line were investigated in both zones to evaluate the excitation properties of the developed excitation microsource. The limit of detection for Na was determined at the level of 3 ng mL- 1.

Magnetogasdynamic Power Extraction and Flow Conditioning for a Gas Turbine

NASA Technical Reports Server (NTRS)

Adamovich, Igor V.; Rich, J. William; Schneider, Steven; Blankson, Isaiah

2003-01-01

An extension of the Russian AJAX concept to a turbojet is being explored. This magnetohydrodynamic (MHD) energy bypass engine cycle incorporating conventional gas turbine technology has MHD flow conditioning at the inlet to electromagnetically extract part of the inlet air kinetic energy. The electrical power generated can be used for various on-board vehicle requirements including plasma flow control around the vehicle or it may be used for augmenting the expanding flow in the high speed nozzle by MHD forces to generate more thrust. In order to achieve this interaction, the air needs to be ionized by an external means even up to fairly high flight speeds, and the leading candidates may be classified as electrical discharge devices. The present kinetic modeling calculations suggest that the use of electron beams with characteristics close to the commercially available e-beam systems (electron energy approx. 60 keV, beam current approx. 0.2 mA/sq cm) to sustain ionization in intermediate pressure, low-temperature (P = 0.1 atm, T = 300 K) supersonic air flows allows considerable reduction of the flow kinetic energy (up to 10 to 20 percent in M = 3 flows). The calculations also suggest that this can be achieved at a reasonable electron beam efficiency (eta approx. 5), even if the e-beam window losses are taken into account. At these conditions, the exit NO and O atom concentrations due to e-beam initiated chemical reactions do not exceed 30 ppm. Increasing the beam current up to approx. 2 mA/sq cm, which corresponds to a maximum electrical conductivity of sigma(sub max) approx. 0.8 mho/m at the loading parameter of K = 0.5, would result in a much greater reduction of the flow kinetic energy (up to 30 to 40 percent). The MHD channel efficiency at these conditions would be greatly reduced (to eta approx. 1) due to increased electron recombination losses in the channel. At these conditions, partial energy conversion from kinetic energy to heat would result in a significant total pressure loss (P(sub 0)/P(sub 0i) approx. 0.3). The total pressure loss can be reduced operating at the loading parameter closer to unity, at the expense of the reduced electrical power output. Raising the beam current would also result in the increase of the exit O atom concentrations (up to 600 ppm) and NO (up to 150 ppm).

Combustion characteristics of gas turbine alternative fuels

NASA Technical Reports Server (NTRS)

Rollbuhler, R. James

1987-01-01

An experimental investigation was conducted to obtain combustion performance values for specific heavyend, synthetic hydrocarbon fuels. A flame tube combustor modified to duplicate an advanced gas turbine engine combustor was used for the tests. Each fuel was tested at steady-state operating conditions over a range of mass flow rates, fuel-to-air mass ratio, and inlet air temperatures. The combustion pressure, as well as the hardware, were kept nearly constant over the program test phase. Test results were obtained in regards to geometric temperature pattern factors as a function of combustor wall temperatures, the combustion gas temperature, and the combustion emissions, both as affected by the mass flow rate and fuel-to-air ratio. The synthetic fuels were reacted in the combustor such that for most tests their performance was as good, if not better, than the baseline gasoline or diesel fuel tests. The only detrimental effects were that at high inlet air temperature conditions, fuel decomposition occurred in the fuel atomizing nozzle passages resulting in blockage. And the nitrogen oxide emissions were above EPA limits at low flow rate and high operating temperature conditions.

Glass-wool study of laser-induced spin currents en route to hyperpolarized Cs salt

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ishikawa, Kiyoshi

2011-07-15

The nuclear spin polarization of optically pumped Cs atoms flows to the surface of Cs hydride in a vapor cell. A fine glass wool lightly coated with the salt helps greatly increase the surface area in contact with the pumped atoms and enhance the spin polarization of the salt nuclei. Even though the glass wool randomly scatters the pump light, the atomic vapor can be polarized with unpolarized light in a magnetic field. The measured enhancement in the salt enables study of the polarizations of light and atomic nuclei very near the salt surface.

Warm Breeze due to Charge Exchange Collisions Between Neutral He Atoms and He+ Ions in the Outer Heliosheath.

NASA Astrophysics Data System (ADS)

Kubiak, M. A.; Bzowski, M.; Czechowski, A.; Grygorczuk, J.

2017-12-01

We simulated the signal due to neutral He atoms, observed by Interstellar Boundary Explorer (IBEX), assuming that charge exchange collisions between neutral He atoms and He+ ions operate everywhere between the heliopause and a distant source region in the local interstellar cloud (LIC). We chose the limiting distance of calculations at 5000 AU, where the neutral and charged components are in thermal equilibrium. From that distance we integrated the signal for test particles that we know they reach the IBEX detector, calculating for each particle the balance of losses and gains in the LIC, the ionization losses inside the HP, and the distribution function at 5000 AU. The resulting statistical weights were integrated over speed, inflow direction, collimator transmission, observation times, and IBEX spin angle bins to simulate the count rate actually observed by IBEX. We simulated several test cases of the plasma flow within the outer heliosheath and investigated the signal generation for plasma flows both in the presence and in the absence of the interstellar magnetic field. We found that a signal in the portion of IBEX data identified as due to the Warm Breeze does not arise when a homogeneous plasma flow in front of the heliopause is assumed. However, it appears immediately when any reasonable disturbance in the plasma flow due to the presence of the heliosphere is assumed. We obtained a good qualitative agreement between the data and the simulations for a model flow with the velocity vector of the unperturbed gas and the direction and intensity of magnetic field adopted from recent determinations. We conclude that direct-sampling observations of neutral He atoms at 1 AU from the Sun are a sensitive tool for investigating the flow of interstellar matter in the outer heliosheath; the Warm Breeze is indeed the secondary population of interstellar helium, as it was hypothesized earlier; the WB signal is consistent with that predicted by comet-like models of the heliosphere with a distortion from axial symmetry by the interstellar magnetic field of 3 microgauss, directed close to the Ribbon direction.

Gas-phase reactions of carbon dioxide with atomic transition-metal and main-group cations: room-temperature kinetics and periodicities in reactivity.

PubMed

Koyanagi, Gregory K; Bohme, Diethard K

2006-02-02

The chemistry of carbon dioxide has been surveyed systematically with 46 atomic cations at room temperature using an inductively-coupled plasma/selected-ion flow tube (ICP/SIFT) tandem mass spectrometer. The atomic cations were produced at ca. 5500 K in an ICP source and allowed to cool radiatively and to thermalize by collisions with Ar and He atoms prior to reaction downstream in a flow tube in helium buffer gas at 0.35 +/- 0.01 Torr and 295 +/- 2 K. Rate coefficients and products were measured for the reactions of first-row atomic ions from K(+) to Se(+), of second-row atomic ions from Rb(+) to Te(+) (excluding Tc(+)), and of third-row atomic ions from Cs(+) to Bi(+). CO(2) was found to react in a bimolecular fashion by O atom transfer only with 9 early transition-metal cations: the group 3 cations Sc(+), Y(+), and La(+), the group 4 cations Ti(+), Zr(+), and Hf(+), the group 5 cations Nb(+) and Ta(+), and the group 6 cation W(+). Electron spin conservation was observed to control the kinetics of O atom transfer. Addition of CO(2) was observed for the remaining 37 cations. While the rate of addition was not measurable some insight was obtained into the standard free energy change, DeltaG(o), for CO(2) ligation from equilibrium constant measurements. A periodic variation in DeltaG(o) was observed for first row cations that is consistent with previous calculations of bond energies D(0)(M(+)-CO(2)). The observed trends in D(0) and DeltaG(o) are expected from the variation in electrostatic attraction between M(+) and CO(2) which follows the trend in atomic-ion size and the trend in repulsion between the orbitals of the atomic cations and the occupied orbitals of CO(2). Higher-order CO(2) cluster ions with up to four CO(2) ligands also were observed for 24 of the atomic cations while MO(2)(+) dioxide formation by sequential O atom transfer was seen only with Hf(+), Nb(+), Ta(+), and W(+).

Modeling of Turbulence Effect on Liquid Jet Atomization

NASA Technical Reports Server (NTRS)

Trinh, H. P.

2007-01-01

Recent studies indicate that turbulence behaviors within a liquid jet have considerable effect on the atomization process. Such turbulent flow phenomena are encountered in most practical applications of common liquid spray devices. This research aims to model the effects of turbulence occurring inside a cylindrical liquid jet to its atomization process. The two widely used atomization models Kelvin-Helmholtz (KH) instability of Reitz and the Taylor analogy breakup (TAB) of O'Rourke and Amsden portraying primary liquid jet disintegration and secondary droplet breakup, respectively, are examined. Additional terms are formulated and appropriately implemented into these two models to account for the turbulence effect. Results for the flow conditions examined in this study indicate that the turbulence terms are significant in comparison with other terms in the models. In the primary breakup regime, the turbulent liquid jet tends to break up into large drops while its intact core is slightly shorter than those without turbulence. In contrast, the secondary droplet breakup with the inside liquid turbulence consideration produces smaller drops. Computational results indicate that the proposed models provide predictions that agree reasonably well with available measured data.

Analytical performance of a low-gas-flow torch optimized for inductively coupled plasma atomic emission spectrometry

USGS Publications Warehouse

Montaser, A.; Huse, G.R.; Wax, R.A.; Chan, S.-K.; Golightly, D.W.; Kane, J.S.; Dorrzapf, A.F.

1984-01-01

An inductively coupled Ar plasma (ICP), generated in a lowflow torch, was investigated by the simplex optimization technique for simultaneous, multielement, atomic emission spectrometry (AES). The variables studied included forward power, observation height, gas flow (outer, intermediate, and nebulizer carrier) and sample uptake rate. When the ICP was operated at 720-W forward power with a total gas flow of 5 L/min, the signal-to-background ratios (S/B) of spectral lines from 20 elements were either comparable or inferior, by a factor ranging from 1.5 to 2, to the results obtained from a conventional Ar ICP. Matrix effect studies on the Ca-PO4 system revealed that the plasma generated in the low-flow torch was as free of vaporizatton-atomizatton interferences as the conventional ICP, but easily ionizable elements produced a greater level of suppression or enhancement effects which could be reduced at higher forward powers. Electron number densities, as determined via the series until line merging technique, were tower ht the plasma sustained in the low-flow torch as compared with the conventional ICP. ?? 1984 American Chemical Society.

Studies on the effect of ammonia flow rate induced defects in gallium nitride grown by MOCVD

NASA Astrophysics Data System (ADS)

Suresh, S.; Lourdudoss, S.; Landgren, G.; Baskar, K.

2010-10-01

Gallium nitride (GaN) epitaxial layers were grown with different V/III ratios by varying the ammonia (NH 3) flow rate, keeping the flow rate of the other precursor, trimethylgallium (TMG), constant, in an MOCVD system. X-ray rocking curve widths of a (1 0 2) reflection increase with an increase in V/III ratio while the (0 0 2) rocking curve widths decrease. The dislocation density was found to increase with an increase in ammonia flow rate, as determined by hot-wet chemical etching and atomic force microscopy. 77 K photoluminescence studies show near band emission at 3.49 eV and yellow luminescence peaking at 2.2 eV. The yellow luminescence (YL) intensity decreases with an increase in V/III ratio. Positron annihilation spectroscopy studies show that the concentration of Ga-like vacancies increases with an increase in ammonia flow rate. This study confirms that the yellow luminescence in the GaN arises due to deep levels formed by gallium vacancies decorated with oxygen atoms.

MEMS testing and applications in automotive and aerospace industries

NASA Astrophysics Data System (ADS)

Ma, Zhichun; Chen, Xuyuan

2009-05-01

MEMS technology combines micromachining and integrated circuit fabrication technologies to produce highly reliable MEMS transducers. This paper presents an overview of MEMS transducers applications, particularly in automotive and aerospace industries, which includes inertia sensors for safety, navigation, and guidance control, thermal anemometer for temperature and heat-flux sensors in engine applications, MEMS atomizers for fuel injection, and micromachined actuators for flow control applications. Design examples for the devices in above mentioned applications are also presented and test results are given.

Aviation fuel property effects on altitude relight

NASA Technical Reports Server (NTRS)

Venkataramani, K.

1987-01-01

The major objective of this experimental program was to investigate the effects of fuel property variation on altitude relight characteristics. Four fuels with widely varying volatility properties (JP-4, Jet A, a blend of Jet A and 2040 Solvent, and Diesel 2) were tested in a five-swirl-cup-sector combustor at inlet temperatures and flows representative of windmilling conditions of turbofan engines. The effects of fuel physical properties on atomization were eliminated by using four sets of pressure-atomizing nozzles designed to give the same spray Sauter mean diameter (50 + or - 10 micron) for each fuel at the same design fuel flow. A second series of tests was run with a set of air-blast nozzles. With comparable atomization levels, fuel volatility assumes only a secondary role for first-swirl-cup lightoff and complete blowout. Full propagation first-cup blowout were independent of fuel volatility and depended only on the combustor operating conditions.

Spray scrubbing of particulate-laden SO(2) using a critical flow atomizer.

PubMed

Bandyopadhyay, Amitava; Biswas, Manindra Nath

2008-08-01

The performance of a spray tower using an energy efficient two-phase critical flow atomizer on the scrubbing of particulate-laden SO(2) using water and dilute NaOH is reported in this article. Experimentation revealed that SO(2) removal was enhanced due to presence of particles (fly-ash) and almost 100% removal efficiency was achieved in water scrubbing. The removal efficiency is elucidated in reference to atomizing air pressure, droplet diameter and droplet velocity besides other pertinent variables of the system studied. The presence of fly-ash particles improved the removal efficiency to about 20% within the range of variables studied. Empirical and semi-empirical correlations were developed for predicting the removal efficiency in water and dilute NaOH respectively. Predicted data fitted excellently well with experimental values. The performance of the spray tower is compared with the performances of existing systems and very encouraging results are obtained.

Repetitive Interrogation of 2-Level Quantum Systems

NASA Technical Reports Server (NTRS)

Prestage, John D.; Chung, Sang K.

2010-01-01

Trapped ion clocks derive information from a reference atomic transition by repetitive interrogations of the same quantum system, either a single ion or ionized gas of many millions of ions. Atomic beam frequency standards, by contrast, measure reference atomic transitions in a continuously replenished "flow through" configuration where initial ensemble atomic coherence is zero. We will describe some issues and problems that can arise when atomic state selection and preparation of the quantum atomic system is not completed, that is, optical pumping has not fully relaxed the coherence and also not fully transferred atoms to the initial state. We present a simple two-level density matrix analysis showing how frequency shifts during the state-selection process can cause frequency shifts of the measured clock transition. Such considerations are very important when a low intensity lamp light source is used for state selection, where there is relatively weak relaxation and re-pumping of ions to an initial state and much weaker 'environmental' relaxation of the atomic coherence set-up in the atomic sample.

Mechanistic modeling study on process optimization and precursor utilization with atmospheric spatial atomic layer deposition

DOE Office of Scientific and Technical Information (OSTI.GOV)

Deng, Zhang; He, Wenjie; Duan, Chenlong

2016-01-15

Spatial atomic layer deposition (SALD) is a promising technology with the aim of combining the advantages of excellent uniformity and conformity of temporal atomic layer deposition (ALD), and an industrial scalable and continuous process. In this manuscript, an experimental and numerical combined model of atmospheric SALD system is presented. To establish the connection between the process parameters and the growth efficiency, a quantitative model on reactant isolation, throughput, and precursor utilization is performed based on the separation gas flow rate, carrier gas flow rate, and precursor mass fraction. The simulation results based on this model show an inverse relation betweenmore » the precursor usage and the carrier gas flow rate. With the constant carrier gas flow, the relationship of precursor usage and precursor mass fraction follows monotonic function. The precursor concentration, regardless of gas velocity, is the determinant factor of the minimal residual time. The narrow gap between precursor injecting heads and the substrate surface in general SALD system leads to a low Péclet number. In this situation, the gas diffusion act as a leading role in the precursor transport in the small gap rather than the convection. Fluid kinetics from the numerical model is independent of the specific structure, which is instructive for the SALD geometry design as well as its process optimization.« less

Molecular dynamic simulation of Ar-Kr mixture across a rough walled nanochannel: Velocity and temperature profiles

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pooja,, E-mail: pupooja16@gmail.com; Ahluwalia, P. K., E-mail: pk-ahluwalia7@yahoo.com; Pathania, Y.

2015-05-15

This paper presents the results from a molecular dynamics simulation of mixture of argon and krypton in the Poiseuille flow across a rough walled nanochannel. The roughness effect on liquid nanoflows has recently drawn attention The computational software used for carrying out the molecular dynamics simulations is LAMMPS. The fluid flow takes place between two parallel plates and is bounded by horizontal rough walls in one direction and periodic boundary conditions are imposed in the other two directions. Each fluid atom interacts with other fluid atoms and wall atoms through Leenard-Jones (LJ) potential with a cut off distance of 5.0.more » To derive the flow a constant force is applied whose value is varied from 0.1 to 0.3 and velocity profiles and temperature profiles are noted for these values of forces. The velocity profile and temperature profiles are also looked at different channel widths of nanochannel and at different densities of mixture. The velocity profile and temperature profile of rough walled nanochannel are compared with that of smooth walled nanochannel and it is concluded that mean velocity increases with increase in channel width, force applied and decrease in density also with introduction of roughness in the walls of nanochannel mean velocity again increases and results also agree with the analytical solution of a Poiseuille flow.« less

Molecular dynamic simulation of Ar-Kr mixture across a rough walled nanochannel: Velocity & temperature profiles

NASA Astrophysics Data System (ADS)

Pooja, Pathania, Y.; Ahluwalia, P. K.

2015-05-01

This paper presents the results from a molecular dynamics simulation of mixture of argon and krypton in the Poiseuille flow across a rough walled nanochannel. The roughness effect on liquid nanoflows has recently drawn attention The computational software used for carrying out the molecular dynamics simulations is LAMMPS. The fluid flow takes place between two parallel plates and is bounded by horizontal rough walls in one direction and periodic boundary conditions are imposed in the other two directions. Each fluid atom interacts with other fluid atoms and wall atoms through Leenard-Jones (LJ) potential with a cut off distance of 5.0. To derive the flow a constant force is applied whose value is varied from 0.1 to 0.3 and velocity profiles and temperature profiles are noted for these values of forces. The velocity profile and temperature profiles are also looked at different channel widths of nanochannel and at different densities of mixture. The velocity profile and temperature profile of rough walled nanochannel are compared with that of smooth walled nanochannel and it is concluded that mean velocity increases with increase in channel width, force applied and decrease in density also with introduction of roughness in the walls of nanochannel mean velocity again increases and results also agree with the analytical solution of a Poiseuille flow.

Physical Chemistry of Energetic Nitrogen Compounds

DTIC Science & Technology

1993-10-01

2177 (1981). 8. R.F. Heiner, III, H . Helvajian , G.ý. Holloway,-and J.B. Koffend, J. Phys. Chem . 93, 7813 (1989). 9. D.D. Bell and R.D. Coombe, J. Chem...Deuterium Atom Reactions with NFC12 . . . . . . . . . . . . . . . . . . . . . . . . . 15 3. The Reaction of H Atomps with NF2Cl .............. 22 V...or Br,) was admitted downstream such that a portion of the F atoms were converted to H , Cl or Br atoms prior to the admission of HN3 to the flow. When

Increase the threshold voltage of high voltage GaN transistors by low temperature atomic hydrogen treatment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Erofeev, E. V., E-mail: erofeev@micran.ru; Fedin, I. V.; Kutkov, I. V.

High-electron-mobility transistors (HEMTs) based on AlGaN/GaN epitaxial heterostructures are a promising element base for the fabrication of high voltage electronic devices of the next generation. This is caused by both the high mobility of charge carriers in the transistor channel and the high electric strength of the material, which makes it possible to attain high breakdown voltages. For use in high-power switches, normally off-mode GaN transistors operating under enhancement conditions are required. To fabricate normally off GaN transistors, one most frequently uses a subgate region based on magnesium-doped p-GaN. However, optimization of the p-GaN epitaxial-layer thickness and the doping levelmore » makes it possible to attain a threshold voltage of GaN transistors close to V{sub th} = +2 V. In this study, it is shown that the use of low temperature treatment in an atomic hydrogen flow for the p-GaN-based subgate region before the deposition of gate-metallization layers makes it possible to increase the transistor threshold voltage to V{sub th} = +3.5 V. The effects under observation can be caused by the formation of a dipole layer on the p-GaN surface induced by the effect of atomic hydrogen. The heat treatment of hydrogen-treated GaN transistors in a nitrogen environment at a temperature of T = 250°C for 12 h reveals no degradation of the transistor’s electrical parameters, which can be caused by the formation of a thermally stable dipole layer at the metal/p-GaN interface as a result of hydrogenation.« less

Effect of Annealing Temperature and Oxygen Flow in the Properties of Ion Beam Sputtered SnO-₂x Thin Films.

PubMed

Wang, Chun-Min; Huang, Chun-Chieh; Kuo, Jui-Chao; Sahu, Dipti Ranjan; Huang, Jow-Lay

2015-08-14

Tin oxide (SnO 2-x ) thin films were prepared under various flow ratios of O₂/(O₂ + Ar) on unheated glass substrate using the ion beam sputtering (IBS) deposition technique. This work studied the effects of the flow ratio of O₂/(O₂ + Ar), chamber pressures and post-annealing treatment on the physical properties of SnO₂ thin films. It was found that annealing affects the crystal quality of the films as seen from both X-ray diffraction (XRD) and transmission electron microscopy (TEM) analysis. In addition, the surface RMS roughness was measured with atomic force microscopy (AFM). Auger electron spectroscopy (AES) analysis was used to obtain the changes of elemental distribution between tin and oxygen atomic concentration. The electrical property is discussed with attention to the structure factor.

Modeling of Flow Blockage in a Liquid Metal-Cooled Reactor Subassembly with a Subchannel Analysis Code

DOE Office of Scientific and Technical Information (OSTI.GOV)

Jeong, Hae-Yong; Ha, Kwi-Seok; Chang, Won-Pyo

The local blockage in a subassembly of a liquid metal-cooled reactor (LMR) is of importance to the plant safety because of the compact design and the high power density of the core. To analyze the thermal-hydraulic parameters in a subassembly of a liquid metal-cooled reactor with a flow blockage, the Korea Atomic Energy Research Institute has developed the MATRA-LMR-FB code. This code uses the distributed resistance model to describe the sweeping flow formed by the wire wrap around the fuel rods and to model the recirculation flow after a blockage. The hybrid difference scheme is also adopted for the descriptionmore » of the convective terms in the recirculating wake region of low velocity. Some state-of-the-art turbulent mixing models were implemented in the code, and the models suggested by Rehme and by Zhukov are analyzed and found to be appropriate for the description of the flow blockage in an LMR subassembly. The MATRA-LMR-FB code predicts accurately the experimental data of the Oak Ridge National Laboratory 19-pin bundle with a blockage for both the high-flow and low-flow conditions. The influences of the distributed resistance model, the hybrid difference method, and the turbulent mixing models are evaluated step by step with the experimental data. The appropriateness of the models also has been evaluated through a comparison with the results from the COMMIX code calculation. The flow blockage for the KALIMER design has been analyzed with the MATRA-LMR-FB code and is compared with the SABRE code to guarantee the design safety for the flow blockage.« less

Ultralow temperature synthesis and improved adsorption performance of graphene oxide nanosheets

NASA Astrophysics Data System (ADS)

Tao, Xiaojun; Wang, Xiaodong; Li, Zhiwei; Zhou, Shaomin

2015-01-01

In this article, we first report an ultralow temperature (-60 °C) synthesis of graphene oxide nanosheets (GONs), which is achieved via the reduction reaction of tetrachloroethylene (C2Cl4) and potassium in liquid ammonia solution at atmospheric pressure. The as-obtained multilayer GONs with a high quality exhibit a low C/O atomic ratio of approximately 2:1, indicating that GONs are rich in the oxygen-containing functional groups. In order to improve their adsorption property, GONs are reduced at 500 °C for 2 h in flowing N2, which results in the successful preparation of graphene nanosheets (GNs) with a high C/O atomic ratio of approximately 32:1. GNs show high specific surface area (508 m2/g), high adsorption capacity (Qe = 148.36 mg/g, Co = 180 mg/L), and rapid adsorption rate (>96%, 10 min) of organic dye rhodamine B (RhB) from water, suggesting that GNs have potential environmental applications as alternatives to commercial materials in wastewater treatment for the removal of organic dye. Compared with the reported methods to prepare GONs, our techniques have attractive advantages, such as low reaction temperature and being friendly to environment.

Reliable and Affordable Control Systems Active Combustor Pattern Factor Control

NASA Technical Reports Server (NTRS)

McCarty, Bob; Tomondi, Chris; McGinley, Ray

2004-01-01

Active, closed-loop control of combustor pattern factor is a cooperative effort between Honeywell (formerly AlliedSignal) Engines and Systems and the NASA Glenn Research Center to reduce emissions and turbine-stator vane temperature variations, thereby enhancing engine performance and life, and reducing direct operating costs. Total fuel flow supplied to the engine is established by the speed/power control, but the distribution to individual atomizers will be controlled by the Active Combustor Pattern Factor Control (ACPFC). This system consist of three major components: multiple, thin-film sensors located on the turbine-stator vanes; fuel-flow modulators for individual atomizers; and control logic and algorithms within the electronic control.

Flow injection analysis-flame atomic absorption spectrometry system for indirect determination of sulfite after on-line reduction of solid-phase manganese (IV) dioxide reactor.

PubMed

Zare-Dorabei, Rouholah; Boroun, Shokoufeh; Noroozifar, Meissam

2018-02-01

A new and simple flow injection method followed by atomic absorption spectrometry was developed for indirect determination of sulfite. The proposed method is based on the oxidation of sulfite to sulphate ion using solid-phase manganese dioxide (30% W/W suspended on silica gel beads) reactor. MnO 2 will be reduced to Mn(II) by sample injection in to the column under acidic carrier stream of HNO 3 (pH 2) with flow rate of 3.5mLmin -1 at room temperature. Absorption measurement of Mn(II) which is proportional to the concentration of sulfite in the sample was carried out by atomic absorption spectrometry. The calibration curve was linear up to 25mgL -1 with a detection limit (DL) of 0.08mgL -1 for 400µL injection sample volume. The presented method is efficient toward sulfite determination in sugar and water samples with a relative standard deviation (RSD) less than 1.2% and a sampling rate of about 60h -1 . Copyright © 2017 Elsevier B.V. All rights reserved.

Water Atomization of Barium Fluoride: Calcium Fluoride for Enhanced Flow Characteristics of PS304 Feedstock Powder Blend

NASA Technical Reports Server (NTRS)

Stanford, Malcolm K.; DellaCorte, Christopher

2003-01-01

PS304 is a plasma spray deposited solid lubricant coating with feedstock composed of NiCr, Cr2O3, Ag, and BaF2-CaF2 powders. The effects of rounded BaF2-CaF2 particles on the gravity-fed flow characteristics of PS304 feedstock have been investigated. The BaF2-CaF2 powder was fabricated by water atomization using four sets of process parameters. Each of these powders was then characterized by microscopy and classified by screening to obtain 45 to 106 micron particles and added incrementally from 0 to 10 wt% to the other constituents of the PS304 feedstock, namely nichrome, chromia, and silver powders. The relationship between feedstock flow rate, measured with the Hall flowmeter, and concentration of fluorides was found to be linear in each case. The slopes of the lines were between those of the linear relationships previously reported using angular and spherical fluorides and were closer to the relationship predicted using the rule of mixtures. The results offer a fluoride fabrication technique potentially more cost-effective than gas atomization processes or traditional comminution processes.

Experimental study on the effect of nozzle hole-to-hole angle on the near-field spray of diesel injector using fast X-ray phase-contrast imaging

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhang, Xusheng; Moon, Seoksu; Gao, Jian

Fuel atomization and vaporization process play a critical role in determining the engine combustion and emission. The primary near-nozzle breakup is the vital link between the fuel emerging from the nozzle and the fully atomized spray. In this study, the near-nozzle spray characteristics of diesel injector with different umbrella angle (UA) were investigated using high-speed X-ray phase-contrast imaging and quantitative image processing. A classic ‘dumbbell’ profile of spray width (SW) composed of three stages: opening stage, semisteady stage and closing stage. The SW peak of two-hole injectors was more than twice of that of single-hole injector at the opening andmore » closing stages, corresponding to the hollow-cone spray. This indicated the vortex flow was formed with the increase of the UA. The higher injection pressure had little influence on the SW while led to earlier breakup closer to the nozzle. Significant fuel effect on the SW at higher needle lift was found. However, this effect could be neglect at lower needle lift due to the leading role of internal flow and cavitation on the near-field spray characteristics. In addition, the morphology-based breakup process was observed, which highlighted the important effect of internal flow on the spray development. The possibility of using hollow-cone spray in diesel injector was also discussed.« less

Atomic-scale reversibility in sheared glasses

NASA Astrophysics Data System (ADS)

Fan, Meng; Wang, Minglei; Liu, Yanhui; Schroers, Jan; Shattuck, Mark; O'Hern, Corey

Systems become irreversible on a macroscopic scale when they are sheared beyond the yield strain and begin flowing. Using computer simulations of oscillatory shear, we investigate atomic scale reversibility. We employ molecular dynamics simulations to cool binary Lennard-Jones liquids to zero temperature over a wide range of cooling rates. We then apply oscillatory quasistatic shear at constant pressure to the zero-temperature glasses and identify neighbor-switching atomic rearrangement events. We determine the critical strain γ*, beyond which atoms in the system do not return to their original positions upon reversing the strain. We show that for more slowly cooled glasses, the average potential energy is lower and the typical size of atomic rearrangements is smaller, which correlates with larger γ*. Finally, we connect atomic- and macro-scale reversibility by determining the number of and correlations between the atomic rearrangements that occur as the system reaches the yield strain.

Direct rate constant measurements for the reaction of ground-state atomic oxygen with ethylene, 244-1052 K

DOE Office of Scientific and Technical Information (OSTI.GOV)

Klemm, R.B.; Nesbitt, F.L.; Skolnik, E.G.

The rate constant for the reaction of ground-state atomic oxygen with ethylene was determined by using two techniques: flash photolysis-resonance fluorescence (FP-RF, 244-1052 K) and discharge flow-resonance fluorescence (DF-RF, 298-1017 K). Kinetic complications due to the presence of molecular oxygen in the FP-RF experiments at high temperatures (T > 800 K) were overcome by using NO as the photolytic source of the O atoms. The rate constant, k/sub 1/ (T), derived in this study exhibits extreme non-Arrhenius behavior, but it can be successfully fit to the sum of exponentials expression, 244-1052 K, k/sub 1/(T) = (1.02 +/- 0.06) x 10/supmore » -11/ exp(-753 +/- 17 K/T) + (2.75 +/- 0.26) x 10/sup -10/ exp(-4220 +/- 550 K/T), in units of cm/sup 3/ molecule/sup -1/ s/sup -1/. Additionally, a fit of the results of this work to a simple transition-state theory expression and the comparison of these results with those of other workers are discussed.« less

Momentum rate probe for use with two-phase flows

NASA Astrophysics Data System (ADS)

Bush, S. G.; Bennett, J. B.; Sojka, P. E.; Panchagnula, M. V.; Plesniak, M. W.

1996-05-01

An instrument for measuring the momentum rate of two-phase flows is described, and design and construction details are provided. The device utilizes a conelike body to turn the flow from the axial to the radial direction. The force resulting from the change in momentum rate of the turning flow is measured using a strain-gage-instrumented cantilevered beam. The instrument is applicable to a wide range of flows including nuclear reactor coolant streams, refrigerants in heating-ventilating air-conditioning equipment, impingement cooling of small scale electronic hardware (computer chips are one example), supercritical fuel injection (in Diesel engines, for instance), and consumer product sprays (such as hair-care product sprays produced using effervescent atomizers). The latter application is discussed here. Features of the instrument include sensitivity to a wide range of forces and the ability to damp oscillations of the deflection cone. Instrument sensitivity allows measurement of momentum rates considerably lower (below 0.01 N) than those that could be obtained using previous devices. This feature is a direct result of our use of precision strain gages, capable of sensing strains below 20 μm/m, and the damping of oscillations which can overwhelm the force measurements. Oscillation damping results from a viscous fluid damper whose resistance is easily varied by changing fluids. Data used to calibrate the instrument are presented to demonstrate the effectiveness of the technique. As an example of the instrument's utility, momentum rate data obtained using it will be valuable in efforts to explain entrainment of surrounding air into effervescent atomizer-produced sprays and also to model the effervescent atomization process.

Carbon-, sulfur-, and phosphorus-based charge transfer reactions in inductively coupled plasma-atomic emission spectrometry

NASA Astrophysics Data System (ADS)

Grindlay, Guillermo; Gras, Luis; Mora, Juan; de Loos-Vollebregt, Margaretha T. C.

2016-01-01

In this work, the influence of carbon-, sulfur-, and phosphorus-based charge transfer reactions on the emission signal of 34 elements (Ag, Al, As, Au, B, Ba, Be, Ca, Cd, Co, Cr, Cu, Fe, Ga, Hg, I, In, Ir, K, Li, Mg, Mn, Na, Ni, P, Pb, Pd, Pt, S, Sb, Se, Sr, Te, and Zn) in axially viewed inductively coupled plasma-atomic emission spectrometry has been investigated. To this end, atomic and ionic emission signals for diluted glycerol, sulfuric acid, and phosphoric acid solutions were registered and results were compared to those obtained for a 1% w w- 1 nitric acid solution. Experimental results show that the emission intensities of As, Se, and Te atomic lines are enhanced by charge transfer from carbon, sulfur, and phosphorus ions. Iodine and P atomic emission is enhanced by carbon- and sulfur-based charge transfer whereas the Hg atomic emission signal is enhanced only by carbon. Though signal enhancement due to charge transfer reactions is also expected for ionic emission lines of the above-mentioned elements, no experimental evidence has been found with the exception of Hg ionic lines operating carbon solutions. The effect of carbon, sulfur, and phosphorus charge transfer reactions on atomic emission depends on (i) wavelength characteristics. In general, signal enhancement is more pronounced for electronic transitions involving the highest upper energy levels; (ii) plasma experimental conditions. The use of robust conditions (i.e. high r.f. power and lower nebulizer gas flow rates) improves carbon, sulfur, and phosphorus ionization in the plasma and, hence, signal enhancement; and (iii) the presence of other concomitants (e.g. K or Ca). Easily ionizable elements reduce ionization in the plasma and consequently reduce signal enhancement due to charge transfer reactions.

Rapid brain scanning radiopharmaceutical

DOEpatents

Sargent, T.W. III; Shulgin, A.T.; Mathis, C.A.

1987-03-03

A method for detecting the blood flow in animals, particularly in the brain, is provided wherein a detectable amount of a novel radioactive compound of the formula 1 is administered to one animal: as given in figure in patent wherein R[sub 1] and R[sub 2] are independently alkyl of 1 to 6 carbon atoms or benzyl; R[sub 3] is alkyl of 1 to 6 carbon atoms, benzyl, cyclopropylalkyl of 4 to 6 carbon atoms, or cyanoalkyl of 2 to 6 carbon atoms; R[sub 4] is hydrogen, benzyl or alkyl of 1 to 6 carbon atoms; with the provisos that R[sub 4] is not isopropyl and when R[sub 4] is methyl, R[sub 3] is not benzyl; and X is a radioactive halogen. 2 figs.

Rapid brain scanning radiopharmaceutical

DOEpatents

Sargent, III, Thornton W.; Shulgin, Alexander T.; Mathis, Chester A.

1987-01-01

A method for detecting the blood flow in animals, particularly in the brain, is provided wherein a detectable amount of a novel radioactive compound of the formula I is administered to one animal: ##STR1## wherein R.sub.1 and R.sub.2 are independently alkyl of 1 to 6 carbon atoms or benzyl; R.sub.3 is alkyl of 1 to 6 carbon atoms, benzyl, cyclopropylalkyl of 4 to 6 carbon atoms, or cyanoalkyl of 2 to 6 carbon atoms; R.sub.4 is hydrogen, benzyl or alkyl of 1 to 6 carbon atoms; with the provisos that R.sub.4 is not isopropyl and when R.sub.4 is methyl, R.sub.3 is not benzyl; and X is a radioactive halogen.

Mitigating leaks in membranes

DOEpatents

Karnik, Rohit N.; Bose, Suman; Boutilier, Michael S.H.; Hadjiconstantinou, Nicolas G.; Jain, Tarun Kumar; O'Hern, Sean C.; Laoui, Tahar; Atieh, Muataz A.; Jang, Doojoon

2018-02-27

Two-dimensional material based filters, their method of manufacture, and their use are disclosed. In one embodiment, a membrane may include an active layer including a plurality of defects and a deposited material associated with the plurality of defects may reduce flow therethrough. Additionally, a majority of the active layer may be free from the material. In another embodiment, a membrane may include a porous substrate and an atomic layer deposited material disposed on a surface of the porous substrate. The atomic layer deposited material may be less hydrophilic than the porous substrate and an atomically thin active layer may be disposed on the atomic layer deposited material.

Measurements and kinetic modeling of atomic species in fuel-oxidizer mixtures excited by a repetitive nanosecond pulse discharge

NASA Astrophysics Data System (ADS)

Winters, C.; Eckert, Z.; Yin, Z.; Frederickson, K.; Adamovich, I. V.

2018-01-01

This work presents the results of number density measurements of metastable Ar atoms and ground state H atoms in diluted mixtures of H2 and O2 with Ar, as well as ground state O atoms in diluted H2-O2-Ar, CH4-O2-Ar, C3H8-O2-Ar, and C2H4-O2-Ar mixtures excited by a repetitive nanosecond pulse discharge. The measurements have been made in a nanosecond pulse, double dielectric barrier discharge plasma sustained in a flow reactor between two plane electrodes encapsulated within dielectric material, at an initial temperature of 500 K and pressures ranging from 300 Torr to 700 Torr. Metastable Ar atom number density distribution in the afterglow is measured by tunable diode laser absorption spectroscopy, and used to characterize plasma uniformity. Temperature rise in the reacting flow is measured by Rayleigh scattering. H atom and O atom number densities are measured by two-photon absorption laser induced fluorescence. The results are compared with kinetic model predictions, showing good agreement, with the exception of extremely lean mixtures. O atoms and H atoms in the plasma are produced mainly during quenching of electronically excited Ar atoms generated by electron impact. In H2-Ar and O2-Ar mixtures, the atoms decay by three-body recombination. In H2-O2-Ar, CH4-O2-Ar, and C3H8-O2-Ar mixtures, O atoms decay in a reaction with OH, generated during H atom reaction with HO2, with the latter produced by three-body H atom recombination with O2. The net process of O atom decay is O  +  H  →  OH, such that the decay rate is controlled by the amount of H atoms produced in the discharge. In extra lean mixtures of propane and ethylene with O2-Ar the model underpredicts the O atom decay rate. At these conditions, when fuel is completely oxidized by the end of the discharge burst, the net process of O atom decay, O  +  O  →  O2, becomes nearly independent of H atom number density. Lack of agreement with the data at these conditions is likely due to diffusion of H atoms from the partially oxidized regions near the side walls of the reactor into the plasma. Although significant fractions of hydrogen and hydrocarbon fuels are oxidized by O atoms produced in the plasma, chain branching remains a minor effect at these relatively low temperature conditions.

Concentration of atomic hydrogen in a dielectric barrier discharge measured by two-photon absorption fluorescence

NASA Astrophysics Data System (ADS)

Dvořák, P.; Talába, M.; Obrusník, A.; Kratzer, J.; Dědina, J.

2017-08-01

Two-photon absorption laser-induced fluorescence (TALIF) was utilized for measuring the concentration of atomic hydrogen in a volume dielectric barrier discharge (DBD) ignited in mixtures of Ar, H2 and O2 at atmospheric pressure. The method was calibrated by TALIF of krypton diluted in argon at atmospheric pressure, proving that three-body collisions had a negligible effect on quenching of excited krypton atoms. The diagnostic study was complemented with a 3D numerical model of the gas flow and a zero-dimensional model of the chemistry in order to better understand the reaction kinetics and identify the key pathways leading to the production and destruction of atomic hydrogen. It was determined that the density of atomic hydrogen in Ar-H2 mixtures was in the order of 1021 m-3 and decreased when oxygen was added into the gas mixture. Spatially resolved measurements and simulations revealed a sharply bordered region with low atomic hydrogen concentration when oxygen was added to the gas mixture. At substoichiometric oxygen/hydrogen ratios, this H-poor region is confined to an area close to the gas inlet and it is shown that the size of this region is not only influenced by the chemistry but also by the gas flow patterns. Experimentally, it was observed that a decrease in H2 concentration in the feeding Ar-H2 mixture led to an increase in H production in the DBD.

Observation of dynamic atom-atom correlation in liquid helium in real space

DOE PAGES

Dmowski, W.; Diallo, S. O.; Lokshin, K.; ...

2017-05-04

Liquid 4He becomes superfluid and flows without resistance below temperature 2.17 K. Superfluidity has been a subject of intense studies and notable advances were made in elucidating the phenomenon by experiment and theory. Nevertheless, details of the microscopic state, including dynamic atom–atom correlations in the superfluid state, are not fully understood. Here using a technique of neutron dynamic pair-density function (DPDF) analysis we show that 4He atoms in the Bose–Einstein condensate have environment significantly different from uncondensed atoms, with the interatomic distance larger than the average by about 10%, whereas the average structure changes little through the superfluid transition. DPDFmore » peak not seen in the snap-shot pair-density function is found at 2.3 Å, and is interpreted in terms of atomic tunnelling. The real space picture of dynamic atom–atom correlations presented here reveal characteristics of atomic dynamics not recognized so far, compelling yet another look at the phenomenon.« less

Observation of dynamic atom-atom correlation in liquid helium in real space

DOE Office of Scientific and Technical Information (OSTI.GOV)

Dmowski, W.; Diallo, S. O.; Lokshin, K.

Liquid 4He becomes superfluid and flows without resistance below temperature 2.17 K. Superfluidity has been a subject of intense studies and notable advances were made in elucidating the phenomenon by experiment and theory. Nevertheless, details of the microscopic state, including dynamic atom–atom correlations in the superfluid state, are not fully understood. Here using a technique of neutron dynamic pair-density function (DPDF) analysis we show that 4He atoms in the Bose–Einstein condensate have environment significantly different from uncondensed atoms, with the interatomic distance larger than the average by about 10%, whereas the average structure changes little through the superfluid transition. DPDFmore » peak not seen in the snap-shot pair-density function is found at 2.3 Å, and is interpreted in terms of atomic tunnelling. The real space picture of dynamic atom–atom correlations presented here reveal characteristics of atomic dynamics not recognized so far, compelling yet another look at the phenomenon.« less

JAERI instrumented spool piece performance in two-phase flow

DOE Office of Scientific and Technical Information (OSTI.GOV)

Colson, J.B.; Gilbert, J.V.

1979-01-01

Instrumented spool pieces to be installed in horizontal piping on the Cylindrical Core Test Facility (CCTF) at the Japanese Atomic Energy Institute (JAERI) have been designed and tested. The instrumented spool pieces will provide measurements from which mass flow rates can be computed. The primary instruments included in the spool pieces are a full-flow turbine, a full-flow perforated drag plate, and a low energy three-beam photon densitometer. Secondary instruments are provided to measured absolute pressure, fluid temperature, and differential pressure across the full-flow perforated drag plate.

Using Asymmetric Flow Field-Flow Fractionation (AF4) to Determine C60 Colloidal Size Distributions

EPA Science Inventory

The formation of aqueous fullerene suspensions by solvent exchange, sonication, or extended mixing in water is widely reported. Commonly used methods for determining the size of these aggregates rely on static and dynamic light scattering, electron microscopy (EM), or atomic forc...

Asymmetric Flow-Field Flow Fractionation (AF4) of Aqueous C60 Aggregates with Dynamic Light Scattering Size and LC-MS

EPA Science Inventory

Current methods for the size determination of nanomaterials in aqueous suspension include dynamic or static light scattering and electron or atomic force microscopy techniques. Light scattering techniques are limited by poor resolution and the scattering intensity dependence on p...

Studies of Elementary Reactions of Chemical Importance in the Atmospheres of Planets

NASA Technical Reports Server (NTRS)

Nesbitt, Fred L.

2001-01-01

The methyl self-reaction was studied at T = 298 K and 202 K and at three different pressures, P = 0.5, 1.0, and 2.1 Torr. The experimental measurements were performed in our discharge flow-mass spectrometer (DF-MS) apparatus. The methyl radicals were generated by the reaction of F with methane. Passing a mixture of molecular fluorine, F2, in helium through a microwave cavity generated the atomic fluorine reagent. The atomic F enters the flow tube through a rear port on the flow tube. The methane reagent enters the flow tube through a movable injector located coaxial in the flow tube. The decay of methyl radical signal was monitored at a mass/charge ratio (m/z) of 15 as a function of the injector distance. To minimize secondary chemistry from the reaction CH3 + F to CH2 + HF the initial [CH4](sub 0)/[F](sub 0) was above 37.0 and typically 100. This ensures a 1:1 relationship between initial [F] and [CH3]. A titration of F with excess Cl2 yields the initial [F](sub 0). Our experimental methodology to accurately measure the mass spectrometer scaling factor, i.e., the relationship between initial signal and [CH3](sub 0) has been improved. Now we measure the CH3 signal decay under exponential decay conditions at low initial [F](sub 0), 3x10(exp 11) molecule/cc, in the presence of Cl2. This minimizes the second-order decay contributed by the CH3 self-reaction and a simple extrapolation of the 1n(signal) vs time plot to t = 0 gives the initial signal. This provides the desired relationship between initial signal at 15 amu and [CH3](sub 0). The resulting calibration is then applied to the observed decay of the CH3 signal at high concentrations of CH3 assuming linearity of this scaling factor.

Shuttle atmospheric lidar research program

NASA Technical Reports Server (NTRS)

1979-01-01

The Shuttle atmospheric lidar program is discussed in relation to an understanding of the processes governing the Earth's atmosphere and in the capacity to evaluate the atmospheric susceptibility to manmade and natural perturbations. Applications of the lidar which are discussed are the determination of the global flow of water vapor and pollutants in the troposphere, improvement of chemical and transport models of the stratosphere and mesosphere, evaluation of radiative models of the atmosphere, investigation of chemistry and transport of thermospheric atomic species, and investigation of magnetospheric aspects of sun/weather relationships. The features of the lidar measurements discussed are the high spatial resolution, control of the source wavelength and intensity, and high measurement specificity.

High-Throughput Continuous Hydrothermal Synthesis of Transparent Conducting Aluminum and Gallium Co-doped Zinc Oxides.

PubMed

Howard, Dougal P; Marchand, Peter; McCafferty, Liam; Carmalt, Claire J; Parkin, Ivan P; Darr, Jawwad A

2017-04-10

High-throughput continuous hydrothermal flow synthesis was used to generate a library of aluminum and gallium-codoped zinc oxide nanoparticles of specific atomic ratios. Resistivities of the materials were determined by Hall Effect measurements on heat-treated pressed discs and the results collated into a conductivity-composition map. Optimal resistivities of ∼9 × 10 -3 Ω cm were reproducibly achieved for several samples, for example, codoped ZnO with 2 at% Ga and 1 at% Al. The optimum sample on balance of performance and cost was deemed to be ZnO codoped with 3 at% Al and 1 at% Ga.

Bose-Einstein Condensate-Hidden Riches for New Forms of Technology and Energy Generation; Potential for Glimpse into Inner Reality

NASA Astrophysics Data System (ADS)

Reed, Don

With the announcement of the recent successful production of a Bose-Einstein condensate (BEC) of photons, a circle has been completed which started in 1925 with the vision of Albert Einstein and Satyendra Nath Bose - a sustained macroscopic condensed state of matter where all atoms are in the same lowest quantum state. The creation of an all-optical BEC, involving a surprisingly straightforward "tabletop" method which bypasses the normally requisite laser/evaporative cooling equipment and ultra-high vacuum chambers necessary for production of the standard delicate atomic BEC, elevates this phenomenon to a new level well beyond its current perception as mere laboratory curiosity. Accordingly, this development certainly heralds eventual incorporation of atomic and photon BECs as standard operating components of energy-efficient mechanical, optical and electrical systems, implying novel ingenious engineering protocols amenable to all the tools of non-linear and quantum optics. Pointing towards such a promising technological future are the suggestion that a photon BEC could serve as a new high-energy ultra-violet (UV) laser photon source, as well as the recent unprecedented implementation of a closed-loop atom circuit (toroidal atomic BEC) demonstrating precise control of superfluid current flow, forecasting the coveted development of an atomic SQUID. Perhaps more significantly, the new highly robust and manageable optical BEC will allow heretofore unfathomable precise probing of the atomic and nano-levels of nature, affording novel high-quality testing procedures of the major foundations of quantum mechanics itself. Such a primary advancement, providing a clearer glimpse into the microscopic realms, may present us as never before with an unprecedented view of the quantum engine that underpins physical reality itself and help place the contextual nature of entanglement and quantum superposition on a firmer foundation. Thus, further progress in achieving mastery over the precise flexible manipulation of BEC states could demonstrate that quantum contextuality might be an unsuspected over-arching archetypal principle in nature, leading to new insight in regards to the interpretation of quantum mechanics as applied to all levels of nature. Moreover, it will be shown that this concealed and hence heretofore unsuspected contextual aspect of natural laws, as exemplified by the dynamics underlying BEC structure, could be brought to bear to account for physical anomalies inexplicable using current paradigms, such as the claimed energy yields from low-energy nuclear reactions (as represented by the so-called process of "cold fusion"), making this phenomenon more tractable and rendered less controversial.

Experimental study of thermal rectification in suspended monolayer graphene

PubMed Central

Wang, Haidong; Hu, Shiqian; Takahashi, Koji; Zhang, Xing; Takamatsu, Hiroshi; Chen, Jie

2017-01-01

Thermal rectification is a fundamental phenomenon for active heat flow control. Significant thermal rectification is expected to exist in the asymmetric nanostructures, such as nanowires and thin films. As a one-atom-thick membrane, graphene has attracted much attention for realizing thermal rectification as shown by many molecular dynamics simulations. Here, we experimentally demonstrate thermal rectification in various asymmetric monolayer graphene nanostructures. A large thermal rectification factor of 26% is achieved in a defect-engineered monolayer graphene with nanopores on one side. A thermal rectification factor of 10% is achieved in a pristine monolayer graphene with nanoparticles deposited on one side or with a tapered width. The results indicate that the monolayer graphene has great potential to be used for designing high-performance thermal rectifiers for heat flow control and energy harvesting. PMID:28607493

Nonequilibrium combustion effects in supersonic streams

NASA Technical Reports Server (NTRS)

Jensen, R. M.; Bryce, C. A.; Reese, B. A.

1972-01-01

This research program is a theoretical and experimental investigation of the effect of nonequilibrium conditions upon the performance of combustors employing supersonic flows. Calculations and experiments are made regarding the effects on the ignition of hydrogen of the nonequilibrium species (free radicals, atoms, water vapor, etc.) obtained using vitiated air. Results of this investigation show that the nonequilibrium free-radical content from a supersonic vitiated air source will cause early ignition of the hydrogen. An analysis of heated air expended from a high temperature source to test section conditions also indicates that there is sufficient free radical content in the incoming flow to cause early ignition. Water vapor, an inherent contaminant in the generation of vitiated air, was found to reduce the ignition delay period under the experimental conditions considered.

Experimental study of thermal rectification in suspended monolayer graphene.

PubMed

Wang, Haidong; Hu, Shiqian; Takahashi, Koji; Zhang, Xing; Takamatsu, Hiroshi; Chen, Jie

2017-06-13

Thermal rectification is a fundamental phenomenon for active heat flow control. Significant thermal rectification is expected to exist in the asymmetric nanostructures, such as nanowires and thin films. As a one-atom-thick membrane, graphene has attracted much attention for realizing thermal rectification as shown by many molecular dynamics simulations. Here, we experimentally demonstrate thermal rectification in various asymmetric monolayer graphene nanostructures. A large thermal rectification factor of 26% is achieved in a defect-engineered monolayer graphene with nanopores on one side. A thermal rectification factor of 10% is achieved in a pristine monolayer graphene with nanoparticles deposited on one side or with a tapered width. The results indicate that the monolayer graphene has great potential to be used for designing high-performance thermal rectifiers for heat flow control and energy harvesting.

Resonant Doppler velocimeter. Ph.D. Thesis. Final Report, 1 Jul. 1974 - 31 Oct. 1979; [velocity, temperature, and pressure measurement

NASA Technical Reports Server (NTRS)

Zimmermann, M.

1980-01-01

A technique is presented for visualizing and quantitatively measuring velocity, temperature, and pressure by shining a single frequency laser beam into a gaseous flow which is seeded with an atomic species. The laser is tuned through the absorption frequencies of the seeded species and the absorption profile is detected by observing fluorescence as the atoms relax back to the ground state. The flow velocity is determined by observing the Doppler shift in the absorption frequency. Spectroscopic absorption line broadening mechanisms furnish information regarding the static temperature and pressure of the moving gas. Results of experiments conducted in the free stream and in the bow shock of a conical model mounted in a hypersonic wind tunnel indicate that the experimental uncertainties in the measurement of average values for the velocity, temperature and pressure of the flow are 0.1, 5 and 10 percent respectively.

Turbulent mixing layers in the interstellar medium of galaxies

NASA Technical Reports Server (NTRS)

Slavin, J. D.; Shull, J. M.; Begelman, M. C.

1993-01-01

We propose that turbulent mixing layers are common in the interstellar medium (ISM). Injection of kinetic energy into the ISM by supernovae and stellar winds, in combination with density and temperature inhomogeneities, results in shear flows. Such flows will become turbulent due to the high Reynolds number (low viscosity) of the ISM plasma. These turbulent boundary layers will be particularly interesting where the shear flow occurs at boundaries of hot (approximately 10(exp 6) K) and cold or warm (10(exp 2) - 10(exp 4) K) gas. Mixing will occur in such layers producing intermediate-temperature gas at T is approximately equal to 10(exp 5.0) - 10(exp 5.5) that radiates strongly in the optical, ultraviolet, and EUV. We have modeled these layers under the assumptions of rapid mixing down to the atomic level and steady flow. By including the effects of non-equilibrium ionization and self-photoionization of the gas as it cools after mixing, we predict the intensities of numerous optical, infrared, and ultraviolet emission lines, as well as absorption column densities of C 4, N 5, Si 4, and O 6.

Evaluation of Liquid Fuel Spray Models for Hybrid RANS/LES and DLES Prediction of Turbulent Reactive Flows

NASA Astrophysics Data System (ADS)

Afshar, Ali

An evaluation of Lagrangian-based, discrete-phase models for multi-component liquid sprays encountered in the combustors of gas turbine engines is considered. In particular, the spray modeling capabilities of the commercial software, ANSYS Fluent, was evaluated. Spray modeling was performed for various cold flow validation cases. These validation cases include a liquid jet in a cross-flow, an airblast atomizer, and a high shear fuel nozzle. Droplet properties including velocity and diameter were investigated and compared with previous experimental and numerical results. Different primary and secondary breakup models were evaluated in this thesis. The secondary breakup models investigated include the Taylor analogy breakup (TAB) model, the wave model, the Kelvin-Helmholtz Rayleigh-Taylor model (KHRT), and the Stochastic secondary droplet (SSD) approach. The modeling of fuel sprays requires a proper treatment for the turbulence. Reynolds-averaged Navier-Stokes (RANS), large eddy simulation (LES), hybrid RANS/LES, and dynamic LES (DLES) were also considered for the turbulent flows involving sprays. The spray and turbulence models were evaluated using the available benchmark experimental data.

A physical-based gas-surface interaction model for rarefied gas flow simulation

NASA Astrophysics Data System (ADS)

Liang, Tengfei; Li, Qi; Ye, Wenjing

2018-01-01

Empirical gas-surface interaction models, such as the Maxwell model and the Cercignani-Lampis model, are widely used as the boundary condition in rarefied gas flow simulations. The accuracy of these models in the prediction of macroscopic behavior of rarefied gas flows is less satisfactory in some cases especially the highly non-equilibrium ones. Molecular dynamics simulation can accurately resolve the gas-surface interaction process at atomic scale, and hence can predict accurate macroscopic behavior. They are however too computationally expensive to be applied in real problems. In this work, a statistical physical-based gas-surface interaction model, which complies with the basic relations of boundary condition, is developed based on the framework of the washboard model. In virtue of its physical basis, this new model is capable of capturing some important relations/trends for which the classic empirical models fail to model correctly. As such, the new model is much more accurate than the classic models, and in the meantime is more efficient than MD simulations. Therefore, it can serve as a more accurate and efficient boundary condition for rarefied gas flow simulations.

Atomic Resonance Radiation Energetics Investigation as a Diagnostic Method for Non-Equilibrium Hypervelocity Flows

NASA Technical Reports Server (NTRS)

Meyer, Scott A.; Bershader, Daniel; Sharma, Surendra P.; Deiwert, George S.

1996-01-01

Absorption measurements with a tunable vacuum ultraviolet light source have been proposed as a concentration diagnostic for atomic oxygen, and the viability of this technique is assessed in light of recent measurements. The instrumentation, as well as initial calibration measurements, have been reported previously. We report here additional calibration measurements performed to study the resonance broadening line shape for atomic oxygen. The application of this diagnostic is evaluated by considering the range of suitable test conditions and requirements, and by identifying issues that remain to be addressed.

Highly sensitive protein detection by biospecific AFM-based fishing with pulsed electrical stimulation.

PubMed

Pleshakova, Tatyana O; Malsagova, Kristina A; Kaysheva, Anna L; Kopylov, Arthur T; Tatur, Vadim Yu; Ziborov, Vadim S; Kanashenko, Sergey L; Galiullin, Rafael A; Ivanov, Yuri D

2017-08-01

We report here the highly sensitive detection of protein in solution at concentrations from 10 -15 to 10 -18 m using the combination of atomic force microscopy (AFM) and mass spectrometry. Biospecific detection of biotinylated bovine serum albumin was carried out by fishing out the protein onto the surface of AFM chips with immobilized avidin, which determined the specificity of the analysis. Electrical stimulation was applied to enhance the fishing efficiency. A high sensitivity of detection was achieved by application of nanosecond electric pulses to highly oriented pyrolytic graphite placed under the AFM chip. A peristaltic pump-based flow system, which is widely used in routine bioanalytical assays, was employed throughout the analysis. These results hold promise for the development of highly sensitive protein detection methods using nanosensor devices.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Park, Jeewoo; Kucharek, Harald; Möbius, Eberhard

In this study, we investigate the directional distributions of the secondary interstellar neutral (ISN) He and O populations at Earth's orbit. The secondary populations are created by charge exchange between ISN atoms and interstellar ions in the outer heliosheath. Using the IBEX -Lo He and O observations during the winter–spring seasons (early December to early June) in 2009–2011, we produced all-sky maps for He and O atoms with sputtering corrections. These sky maps include the directional distributions of the primary ISN gas and secondary populations. Our investigations reveal that the secondary He and O populations are observed in the eclipticmore » longitude range 160°–210°. The peak longitudes of the secondary He and O appear to be 14°–34° and 38°–43° away from the peak longitude of the primary interstellar gas flow, respectively. These results indicate that the secondary populations have lower bulk speeds relative to the Sun and their flow directions deviate from the primary gas flow. These results may indicate that one side of the outer heliosheath is thicker than the other side relative to the flow direction of the primary interstellar gas flow.« less

Rapid food decomposition by H2O2-H2SO4 for determination of total mercury by flow injection cold vapor atomic absorption spectrometry.

PubMed

Zenebon, Odair; Sakuma, Alice M; Dovidauskas, Sergio; Okada, Isaura A; de, MaioFrancaD; Lichtig, Jaim

2002-01-01

A mixture of 50% H2O2-H2SO4 (3 + 1, v/v) was used for decomposition of food in open vessels at 80 degrees C. The treatment allowed rapid total mercury determination by flow injection cold vapor atomic absorption spectrometry. Cabbage, potatoes, peanuts paste, hazelnuts paste, oats, tomatoes and their derivatives, oysters, shrimps, prawns, shellfish, marine algae, and many kinds of fish were analyzed by the proposed methodology with a limit of quantitation of 0.86 +/- 0.08 microg/L mercury in the final solution. Reference materials tested also gave excellent recovery.

Investigation of aluminum surface cleaning using cavitating fluid flow

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ralys, Aurimas; Striška, Vytautas; Mokšin, Vadim

This paper investigates efficiency of specially designed atomizer used to spray water and cavitate microbubbles in water flow. Surface cleaning system was used to clean machined (grinded) aluminum surface from abrasive particles. It is established that cleaning efficiency depends on diameter of the diffuser, water pressure and distance between nozzle and metal surface. It is obtained that the best cleaning efficiency (100%) is achieved at pressure 36 bar, when diameter of diffuser is 0.4 mm and distance between nozzle and surface is 1 mm. It is also established that satisfactory cleaning efficiency (80%) is achieved not only when atomizer ismore » placed closer to metal surface, but also at larger (120 mm) distances.« less

Noncontact Viscoelastic Imaging of Living Cells Using a Long-Needle Atomic Force Microscope with Dual-Frequency Modulation

NASA Astrophysics Data System (ADS)

Guan, Dongshi; Charlaix, Elisabeth; Qi, Robert Z.; Tong, Penger

2017-10-01

Imaging of surface topography and elasticity of living cells can provide insight into the roles played by the cells' volumetric and mechanical properties and their response to external forces in regulating the essential cellular events and functions. Here, we report a unique technique of noncontact viscoelastic imaging of live cells using atomic force microscopy (AFM) with a long-needle glass probe. Because only the probe tip is placed in a liquid medium near the cell surface, the AFM cantilever in air functions well under dual-frequency modulation, retaining its high-quality resonant modes. The probe tip interacts with the cell surface through a minute hydrodynamic flow in the nanometer-thin gap region between them without physical contact. Quantitative measurements of the cell height, volume, and Young's modulus are conducted simultaneously. The experiment demonstrates that the long-needle AFM has a wide range of applications in the study of cell mechanics.

Modeling growth kinetics of thin films made by atomic layer deposition in lateral high-aspect-ratio structures

NASA Astrophysics Data System (ADS)

Ylilammi, Markku; Ylivaara, Oili M. E.; Puurunen, Riikka L.

2018-05-01

The conformality of thin films grown by atomic layer deposition (ALD) is studied using all-silicon test structures with long narrow lateral channels. A diffusion model, developed in this work, is used for studying the propagation of ALD growth in narrow channels. The diffusion model takes into account the gas transportation at low pressures, the dynamic Langmuir adsorption model for the film growth and the effect of channel narrowing due to film growth. The film growth is calculated by solving the diffusion equation with surface reactions. An efficient analytic approximate solution of the diffusion equation is developed for fitting the model to the measured thickness profile. The fitting gives the equilibrium constant of adsorption and the sticking coefficient. This model and Gordon's plug flow model are compared. The simulations predict the experimental measurement results quite well for Al2O3 and TiO2 ALD processes.

An investigation of air solubility in Jet A fuel at high pressures

NASA Technical Reports Server (NTRS)

Faeth, G. M.

1981-01-01

Problems concerned with the supercritical injection concept are discussed. Supercritical injection involves dissolving air into a fuel prior to injection. A similar effect is obtained by preheating the fuel so that a portion of the fuel flashes when its pressure is reduced. Flashing improves atomization properties and the presence of air in the primary zone of a spray flame reduces the formation of pollutants. The investigation is divided into three phases: (1) measure the solubility and density properties of fuel/gas mixtures, including Jet A/air, at pressures and correlate these results using theory; (2) investigate the atomization properties of flashing liquids, including fuel/dissolved gas systems. Determine and correlate the effect of inlet properties and injector geometry on mass flow rates, Sauter mean diameter and spray angles; (3) examine the combustion properties of flashing injection in an open burner flame, considering flame shape and soot production.

Study of continuous precipitation of ADU for the implantation in the pilot installation at the Atomic Energy Institute, Brazil. Estudo de precipitacao continua de DUA para a implantacao na instalacao piloto CEQ-IEA (in Portuguese)

DOE Office of Scientific and Technical Information (OSTI.GOV)

Araujo, Jose Adroalado de

1974-05-15

The paper deals with the ammonium diuranate continuous precipitation with a high chemical purity degree from uranyl nitrate solutions, using 1.2 and 2.4 ammonium hydroxide solutions and gaseous NH{sub 3} as a precipitating agent. The precipitations were carried out in a continuous procedure with one and two stages. The variables studied were the NH[sub 4}OH solutions concentration, ADU precipitation curve, the flow rate of reactants, the temperature of the precipitation, pH of the suspended ADU, and ammonium diuranate filtrability. The experimental work performed and the data obtained permitted the design of a chemical reactor for the continuous nuclear grade ADUmore » precipitation at the Chemical Engineering Department of the Atomic Energy Institute of Sao Paulo.« less

A preliminary evaluation of regional ground-water flow in south-central Washington

USGS Publications Warehouse

La Sala, A. M.; Doty, G.C.; Pearson, F.J.

1973-01-01

The characteristics of regional ground-water flow were investigated in a 4,500-square-mile region of south-central Washington, centered on the U.S. Atomic Energy Commission Hanford Reservation. The investigation is part of the Commission's feasibility study on storing high-level radioactive waste in chambers mined in basaltic rocks at a. depth of about 3,000 feet or more below the surface. Ground-water flow., on a regional scale, occurs principally in the basalt and-in interbedded sediments of the Columbia River Group, and is controlled by topography, the structure of the basalt, and the large streams--the Columbia, Snake, and Yakima Rivers. The ground water beneath the main part of the Hanford Reservation, south and west of the Columbia River, inures southeastward from recharge areas in the uplands, including Cold Creek and Dry Creek valleys, and ultimately discharges to the Columbia River south of the reservation: East and southeast of the Columbia River, ground water flows generally southwestward and discharges to the River. The Yakima River valley contains a distinct flow system in which movement is toward the Yakima River from the topographic divides. A large southward-flowing ground-water system beneath the southern flank of the Horse Heaven Hills discharges to the Columbia River in the westward-trending reach downstream from Wallula Gap.

Massive radius-dependent flow slippage in carbon nanotubes.

PubMed

Secchi, Eleonora; Marbach, Sophie; Niguès, Antoine; Stein, Derek; Siria, Alessandro; Bocquet, Lydéric

2016-09-08

Measurements and simulations have found that water moves through carbon nanotubes at exceptionally high rates owing to nearly frictionless interfaces. These observations have stimulated interest in nanotube-based membranes for applications including desalination, nano-filtration and energy harvesting, yet the exact mechanisms of water transport inside the nanotubes and at the water-carbon interface continue to be debated because existing theories do not provide a satisfactory explanation for the limited number of experimental results available so far. This lack of experimental results arises because, even though controlled and systematic studies have explored transport through individual nanotubes, none has met the considerable technical challenge of unambiguously measuring the permeability of a single nanotube. Here we show that the pressure-driven flow rate through individual nanotubes can be determined with unprecedented sensitivity and without dyes from the hydrodynamics of water jets as they emerge from single nanotubes into a surrounding fluid. Our measurements reveal unexpectedly large and radius-dependent surface slippage in carbon nanotubes, and no slippage in boron nitride nanotubes that are crystallographically similar to carbon nanotubes, but electronically different. This pronounced contrast between the two systems must originate from subtle differences in the atomic-scale details of their solid-liquid interfaces, illustrating that nanofluidics is the frontier at which the continuum picture of fluid mechanics meets the atomic nature of matter.

Massive radius-dependent flow slippage in carbon nanotubes

NASA Astrophysics Data System (ADS)

Secchi, Eleonora; Marbach, Sophie; Niguès, Antoine; Stein, Derek; Siria, Alessandro; Bocquet, Lydéric

2016-09-01

Measurements and simulations have found that water moves through carbon nanotubes at exceptionally high rates owing to nearly frictionless interfaces. These observations have stimulated interest in nanotube-based membranes for applications including desalination, nano-filtration and energy harvesting, yet the exact mechanisms of water transport inside the nanotubes and at the water-carbon interface continue to be debated because existing theories do not provide a satisfactory explanation for the limited number of experimental results available so far. This lack of experimental results arises because, even though controlled and systematic studies have explored transport through individual nanotubes, none has met the considerable technical challenge of unambiguously measuring the permeability of a single nanotube. Here we show that the pressure-driven flow rate through individual nanotubes can be determined with unprecedented sensitivity and without dyes from the hydrodynamics of water jets as they emerge from single nanotubes into a surrounding fluid. Our measurements reveal unexpectedly large and radius-dependent surface slippage in carbon nanotubes, and no slippage in boron nitride nanotubes that are crystallographically similar to carbon nanotubes, but electronically different. This pronounced contrast between the two systems must originate from subtle differences in the atomic-scale details of their solid-liquid interfaces, illustrating that nanofluidics is the frontier at which the continuum picture of fluid mechanics meets the atomic nature of matter.

Applications of Nanoparticle-Containing Plasmas for High-Order Harmonic Generation of Laser Radiation

NASA Astrophysics Data System (ADS)

Ganeev, Rashid A.

The use of nanoparticles for efficient conversion of the wavelength of ultrashort laser toward the deep UV spectral range through harmonic generation is an attractive application of cluster-containing plasmas. Note that earlier observations of HHG in nanoparticles were limited by using the exotic gas clusters formed during fast cooling of atomic flow from the gas jets 1-4. One can assume the difficulties in definition of the structure of such clusters and the ratio between nanoparticles and atoms/ions in the gas flow. The characterization of gas phase cluster production was currently improved using the sophisticated techniques (e.g., a control of nanoparticle mass and spatial distribution, see the review 5). In the meantime, the plasma nanoparticle HHG has demonstrated some advantages over gas cluster HHG 6. The application of commercially available nanopowders allowed for precisely defining the sizes and structure of these clusters in the plume. The laser ablation technique made possible the predictable manipulation of plasma characteristics, which led to the creation of laser plumes containing mainly nanoparticles with known spatial structure. The latter allows the application of such plumes in nonlinear optics, X-ray emission of clusters, deposition of nanoparticles with fixed parameters on the substrates for semiconductor industry, production of nanostructured and nanocomposite films, etc.

Atomic Spectra Bibliography Databases at NIST

NASA Astrophysics Data System (ADS)

Kramida, Alexander

2010-03-01

NIST's Atomic Spectroscopy Data Center maintains three online Bibliographic Databases (BD) [http://physics.nist.gov/PhysRefData/ASBib1/index.html]: -- Atomic Energy Levels and Spectra (AEL BD), Atomic Transition Probability (ATP BD), and Atomic Spectral Line Broadening (ALB BD). This year marks new releases of these BDs -- AEL BD v.2.0, ATP BD v.9.0, and ALB DB v.3.0. These releases incorporate significant improvements in the quantity and quality of bibliographic data since the previous versions published first in 2006. The total number of papers in the three DBs grew from 20,000 to 30,000. The data search is now made easier, and the returned content is enriched with direct links to online journal articles and universal Digital Object Identifiers. Statistics show a nearly constant flow of new publications on atomic spectroscopy, about 600 new papers published each year since 1968. New papers are inserted in our BDs every two weeks on average.

On ionizing shock waves

NASA Astrophysics Data System (ADS)

Kaniel, A.; Igra, O.; Ben-Dor, G.; Mond, M.

The flow field in the ionizing relaxation zone developed behind a normal shock wave in an electrically neutral, homogeneous, two temperature mixture of thermally ideal gases (molecules, atoms, ions, electrons) was numerically solved. The heat transfer between the electron gas and the other components was taken into account while all the other transport phenomena (molecular, turbulent and radiative) were neglected in the relaxation zone, since it is dominated by inelastic collisions. The threshold cross sections measured by Specht (1981), for excitation of argon by electron collisions, were used. The calculated results show good agreement with the results of the shock tube experiments presented by Glass and Liu (1978), especially in the electron avalanche region. A critical examination was made of the common assumptions regarding the average energy with which electrons are produced by atom-atom collisions and the relative effectiveness of atom-atom collisions (versus electron-atom collisions) in ionizing excited argon.

Studies of oxygen-helium discharges for use in electric oxygen-iodine lasers

NASA Astrophysics Data System (ADS)

Zimmerman, Joseph William

In recent work, the performance of the Electric Oxygen-Iodine Laser (ElectricOIL), developed in partnership by researchers at the University of Illinois and CU Aerospace, has been greatly improved through systematic study of various components of this new laser technology. One major contribution to the advancement of ElectricOIL technology has been the development of electric discharges capable of producing significant flow rates of the precursor electronically-excited molecular oxygen, O2(a1Delta). O2(a 1Delta) serves as an energy reservoir in the laser system, pumping atomic iodine by near-resonant energy transfer producing gain and laser on the I(2P1/2) → I(2P3/2 ) transition at 1315 nm. Initial experimental work with radio-frequency discharges showed the importance of controlling O-atom flow rates to reduce quenching losses of energy stored in O2(a1Delta), and determined proper selection of the helium diluent ratio and specific power deposition (power per O2 flow rate). Further experimental investigations with transverse capacitive radio-frequency discharges in O2/He/NO mixtures in the pressure range of 1-100 Torr and power range of 0.1-1.2 kW have indicated that O2(a1Delta) production is a strong function of geometry (transverse gap), excitation frequency, and pressure. These parameters along with gas flow mixture dictate the current density at which the discharge operates, and its modal characteristics (normal vs. abnormal, homogeneous vs. inhomogeneous). A key result is that to encourage efficient O2(a1Delta) production these parameters should be selected in order to promote a homogeneous (low current density) discharge. The discharge behavior is characterized using terminal current-voltage-characteristics, microwave interferometer measurements, and plasma emission intensity measurements. Numerous spectroscopic measurements of O2(a1Delta), oxygen atoms, and discharge excited states are made in order to describe the discharge performance dependent on various parameters. The influence of NO on O-atom flow rates and O2(a1Delta) production is investigated. Progress of laser power extraction since initial reports in 2005 is overviewed.

Two-photon absorption laser-induced fluorescence measurements of atomic nitrogen in a radio-frequency atmospheric-pressure plasma jet

NASA Astrophysics Data System (ADS)

Wagenaars, E.; Gans, T.; O'Connell, D.; Niemi, K.

2012-08-01

The first direct measurements of atomic nitrogen species in a radio-frequency atmospheric-pressure plasma jet (APPJ) are presented. Atomic nitrogen radicals play a key role in new plasma medicine applications of APPJs. The measurements were performed with a two-photon absorption laser-induced fluorescence diagnostic, using 206.65 nm laser photons for the excitation of ground-state N atoms and observing fluorescence light around 744 nm. The APPJ was run with a helium gas flow of 1 slm and varying small admixtures of molecular nitrogen of 0-0.7 vol%. A maximum in the measured N concentration was observed for an admixture of 0.25 vol% N2.

Experimental study of plume induced by nanosecond repetitively pulsed spark microdischarges in air at atmospheric pressure

NASA Astrophysics Data System (ADS)

Orriere, Thomas; Benard, Nicolas; Moreau, Eric; Pai, David

2016-09-01

Nanosecond repetitively pulsed (NRP) spark discharges have been widely studied due to their high chemical reactivity, low gas temperature, and high ionization efficiency. They are useful in many research areas: nanomaterials synthesis, combustion, and aerodynamic flow control. In all of these fields, particular attention has been devoted to chemical species transport and/or hydrodynamic and thermal effects for applications. The aim of this study is to generate an electro-thermal plume by combining an NRP spark microdischarge in a pin-to-pin configuration with a third DC-biased electrode placed a few centimeters away. First, electrical characterization and optical emission spectroscopy were performed to reveal important plasma processes. Second, particle image velocimetry was combined with schlieren photography to investigate the main characteristics of the generated flow. Heating processes are measured by using the N2(C ->B) (0,2) and (1,3) vibrational bands, and effects due to the confinement of the discharge are described. Moreover, the presence of atomic ions N+ and O+ is discussed. Finally, the electro-thermal plume structure is characterized by a flow velocity around 1.8 m.s-1, and the thermal kernel has a spheroidal shape.

Raman-scattered O VI λ1032 and He II λ1025 and Bipolar Outflow in the Symbiotic Star V455 Sco

NASA Astrophysics Data System (ADS)

Heo, Jeong-Eun; Angeloni, Rodolfo; Di Mille, Francesco; Palma, Tali; Chang, Seok-Jun; Hong, Chae-Lin; Lee, Hee-Won

2016-07-01

Raman-scattering by atomic hydrogen is a unique spectroscopic process that may probe the mass transfer and mass loss phenomena in symbiotic stars(SSs). In the optical high- resolution spectra of the S-type SS V455 Sco, we note the presence of two Raman-scattered features, one at around 6825 Å with a triple-peak profile formed from Raman-scattering of O VI λ1032 and the other Raman-scattered He II λ1025 at around 6545 Å. Adopting an accretion flow model with additional contribution from a collimated bipolar outflow, we propose that the blue and central peaks are contributed from the accretion flow and the bipolar flow is responsible for the remaining red peak. With the absence of [N II] λ6548, the Raman-scattered He II λ1025 at around 6545 Å is immersed in the broad Ha wings that appear to be formed by Raman-scattering of far-UV continuum near Lyman series.

Modeling Primary Atomization of Liquid Fuels using a Multiphase DNS/LES Approach

DOE Office of Scientific and Technical Information (OSTI.GOV)

Arienti, Marco; Oefelein, Joe; Doisneau, Francois

2016-08-01

As part of a Laboratory Directed Research and Development project, we are developing a modeling-and-simulation capability to study fuel direct injection in automotive engines. Predicting mixing and combustion at realistic conditions remains a challenging objective of energy science. And it is a research priority in Sandia’s mission-critical area of energy security, being also relevant to many flows in defense and climate. High-performance computing applied to this non-linear multi-scale problem is key to engine calculations with increased scientific reliability.

21 CFR 1020.20 - Cold-cathode gas discharge tubes.

Code of Federal Regulations, 2014 CFR

2014-04-01

... discharge tubes designed to demonstrate the effects of a flow of electrons or the production of x-radiation... electron flow is produced and sustained by ionization of contained gas atoms and ion bombardment of the... the ions of one sign produced in air when all electrons liberated by photons in a volume element of...

21 CFR 1020.20 - Cold-cathode gas discharge tubes.

Code of Federal Regulations, 2012 CFR

2012-04-01

... discharge tubes designed to demonstrate the effects of a flow of electrons or the production of x-radiation... electron flow is produced and sustained by ionization of contained gas atoms and ion bombardment of the... the ions of one sign produced in air when all electrons liberated by photons in a volume element of...

21 CFR 1020.20 - Cold-cathode gas discharge tubes.

Code of Federal Regulations, 2013 CFR

2013-04-01

... discharge tubes designed to demonstrate the effects of a flow of electrons or the production of x-radiation... electron flow is produced and sustained by ionization of contained gas atoms and ion bombardment of the... the ions of one sign produced in air when all electrons liberated by photons in a volume element of...

21 CFR 1020.20 - Cold-cathode gas discharge tubes.

Code of Federal Regulations, 2011 CFR

2011-04-01

... discharge tubes designed to demonstrate the effects of a flow of electrons or the production of x-radiation... electron flow is produced and sustained by ionization of contained gas atoms and ion bombardment of the... the ions of one sign produced in air when all electrons liberated by photons in a volume element of...

Emission Spectroscopy and Radiometric Measurements in the NASA Ames IHF Arc Jet Facility

NASA Technical Reports Server (NTRS)

Winter, Michael W.; Raiche, George A.; Prabhu, Dinesh K.

2012-01-01

Plasma diagnostic measurement campaigns in the NASA Ames Interaction Heating Facility (IHF) have been conducted over the last several years with a view towards characterizing the flow in the arc jet facility by providing data necessary for modeling and simulation. Optical emission spectroscopy has been used in the plenum and in the free jet of the nozzle. Radiation incident over a probe surface has also been measured using radiometry. Plenum measurements have shown distinct radial profiles of temperature over a range of operating conditions. For cases where large amounts of cold air are added radially to the main arc-heated stream, the temperature profiles are higher by as much as 1500 K than the profiles assumed in flow simulations. Optical measurements perpendicular to the flow direction in the free jet showed significant contributions to the molecule emission through inverse pre-dissociation, thus allowing determination of atom number densities from molecular emission. This has been preliminarily demonstrated with the N2 1st Positive System. Despite the use of older rate coefficients, the resulting atom densities are reasonable and surprisingly close to flow predictions.

Analytic expressions for Atomic Layer Deposition: coverage, throughput, and materials utilization in cross-flow, particle coating, and spatial ALD

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yanguas-Gil, Angel; Elam, Jeffrey W.

2014-05-01

In this work, the authors present analytic models for atomic layer deposition (ALD) in three common experimental configurations: cross-flow, particle coating, and spatial ALD. These models, based on the plug-flow and well-mixed approximations, allow us to determine the minimum dose times and materials utilization for all three configurations. A comparison between the three models shows that throughput and precursor utilization can each be expressed by universal equations, in which the particularity of the experimental system is contained in a single parameter related to the residence time of the precursor in the reactor. For the case of cross-flow reactors, the authorsmore » show how simple analytic expressions for the reactor saturation profiles agree well with experimental results. Consequently, the analytic model can be used to extract information about the ALD surface chemistry (e. g., the reaction probability) by comparing the analytic and experimental saturation profiles, providing a useful tool for characterizing new and existing ALD processes. (C) 2014 American Vacuum Society« less

The influence of electrohydrodynamic flow on the distribution of chemical species in positive corona

NASA Astrophysics Data System (ADS)

Pontiga, Francisco; Yanallah, Khelifa; Bouazza, R.; Chen, Junhong

2015-09-01

A numerical simulation of positive corona discharge in air, including the effect of electrohydrodynamic (EHD) motion of the gas, has been carried out. Air flow is assumed to be confined between two parallel plates, and corona discharge is produced around a thin wire, midway between the plates. Therefore, fluid dynamics equations, including electrical forces, have been solved together with the continuity equation of each neutral species. The plasma chemical model included 24 chemical reactions and ten neutral species, in addition to electrons and positive ions. The results of the simulation have shown that the influence of EHD flow on the spatial distributions of the species is quite different depending on the species. Hence, reactive species like atomic oxygen and atomic nitrogen are confined to the vicinity of the wire, and they are weakly affected by the EHD gas motion. In contrast, nitrogen oxides and ozone are efficiently dragged outside the active region of the corona discharge by the EHD flow. This work was supported by the Spanish Government Agency ``Ministerio de Ciencia e Innovación'' under Contract No. FIS2011-25161.

Measurements of C V flows from thermal charge-exchange excitation in divertor plasmas

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zaniol, B.; Isler, R. C.; Brooks, N. H.

2001-10-01

Certain transitions of C IV (C{sup 3+}) from n=7 to n=6 ({approx}7226 {angstrom}) and from n=6 to n=5 ({approx}4660 {angstrom}) sometimes appear much brighter in tokamak divertors than expected for electron-impact excitation from the ground state. This situation occurs because of charge exchange between C V (C{sup 4+}) and recycling thermal deuterium atoms in the n=2 level. As a result, it is possible to extend parallel flow measurements of carbon, which have previously been performed on C II--C IV ions using Doppler shift spectroscopy, to include flows of the He-like C V ions. The work described here includes modeling ofmore » the spectral features, correlation of state populations with classical Monte Carlo trajectory (CTMC) predictions, and applications to flow measurements in the DIII-D divertor [Plasma Physics Controlled Nuclear Fusion Research 1986 (International Atomic Energy Agency, Vienna, 1987), Vol. I, p. 159; Proceedings of the 18th IEEE/NPSS Symposium on Fusion Engineering, Albuquerque (Institute of Electrical and Electronic Engineers, Piscataway, 1999), p. 515].« less

Measurements of C V flows from thermal charge-exchange excitation in divertor plasmas

NASA Astrophysics Data System (ADS)

Zaniol, B.; Isler, R. C.; Brooks, N. H.; West, W. P.; Olson, R. E.

2001-10-01

Certain transitions of C IV (C3+) from n=7 to n=6 (≈7226 Å) and from n=6 to n=5 (≈4660 Å) sometimes appear much brighter in tokamak divertors than expected for electron-impact excitation from the ground state. This situation occurs because of charge exchange between C V (C4+) and recycling thermal deuterium atoms in the n=2 level. As a result, it is possible to extend parallel flow measurements of carbon, which have previously been performed on C II-C IV ions using Doppler shift spectroscopy, to include flows of the He-like C V ions. The work described here includes modeling of the spectral features, correlation of state populations with classical Monte Carlo trajectory (CTMC) predictions, and applications to flow measurements in the DIII-D divertor [Plasma Physics Controlled Nuclear Fusion Research 1986 (International Atomic Energy Agency, Vienna, 1987), Vol. I, p. 159; Proceedings of the 18th IEEE/NPSS Symposium on Fusion Engineering, Albuquerque (Institute of Electrical and Electronic Engineers, Piscataway, 1999), p. 515].

Automatic flow-batch system for cold vapor atomic absorption spectroscopy determination of mercury in honey from Argentina using online sample treatment.

PubMed

Domínguez, Marina A; Grünhut, Marcos; Pistonesi, Marcelo F; Di Nezio, María S; Centurión, María E

2012-05-16

An automatic flow-batch system that includes two borosilicate glass chambers to perform sample digestion and cold vapor atomic absorption spectroscopy determination of mercury in honey samples was designed. The sample digestion was performed by using a low-cost halogen lamp to obtain the optimum temperature. Optimization of the digestion procedure was done using a Box-Behnken experimental design. A linear response was observed from 2.30 to 11.20 μg Hg L(-1). The relative standard deviation was 3.20% (n = 11, 6.81 μg Hg L(-1)), the sample throughput was 4 sample h(-1), and the detection limit was 0.68 μg Hg L(-1). The obtained results with the flow-batch method are in good agreement with those obtained with the reference method. The flow-batch system is simple, allows the use of both chambers simultaneously, is seen as a promising methodology for achieving green chemistry goals, and is a good proposal to improving the quality control of honey.

Atomic Force Microscope Mediated Chromatography

NASA Technical Reports Server (NTRS)

Anderson, Mark S.

2013-01-01

The atomic force microscope (AFM) is used to inject a sample, provide shear-driven liquid flow over a functionalized substrate, and detect separated components. This is demonstrated using lipophilic dyes and normal phase chromatography. A significant reduction in both size and separation time scales is achieved with a 25-micron-length column scale, and one-second separation times. The approach has general applications to trace chemical and microfluidic analysis. The AFM is now a common tool for ultra-microscopy and nanotechnology. It has also been demonstrated to provide a number of microfluidic functions necessary for miniaturized chromatography. These include injection of sub-femtoliter samples, fluidic switching, and sheardriven pumping. The AFM probe tip can be used to selectively remove surface layers for subsequent microchemical analysis using infrared and tip-enhanced Raman spectroscopy. With its ability to image individual atoms, the AFM is a remarkably sensitive detector that can be used to detect separated components. These diverse functional components of microfluidic manipulation have been combined in this work to demonstrate AFM mediated chromatography. AFM mediated chromatography uses channel-less, shear-driven pumping. This is demonstrated with a thin, aluminum oxide substrate and a non-polar solvent system to separate a mixture of lipophilic dyes. In conventional chromatographic terms, this is analogous to thin-layer chromatography using normal phase alumina substrate with sheardriven pumping provided by the AFM tip-cantilever mechanism. The AFM detection of separated components is accomplished by exploiting the variation in the localized friction of the separated components. The AFM tip-cantilever provides the mechanism for producing shear-induced flows and rapid pumping. Shear-driven chromatography (SDC) is a relatively new concept that overcomes the speed and miniaturization limitations of conventional liquid chromatography. SDC is based on a sliding plate system, consisting of two flat surfaces, one of which has a recessed channel. A fluid flow is produced by axially sliding one plate past another, where the fluid has mechanical shear forces imposed at each point along the channel length. The shear-induced flow rates are very reproducible, and do not have pressure or voltage gradient limitations. SDC opens up a new range of enhanced separation kinetics by permitting the sample confinement with submicron dimensions. Small, highly confined liquid is advantageous for chromatographic separation because the separation rate is known to scale according to the square of the confined sample diameter. In addition, because shear-driven flows are not limited by fluid velocity, shear-driven liquid chromatography may provide up to 100,000 plate efficiency.

Capturing Gases in Carbon Honeycomb

NASA Astrophysics Data System (ADS)

Krainyukova, Nina V.

2017-04-01

In our recent paper (Krainyukova and Zubarev in Phys Rev Lett 116:055501, 2016. doi: 10.1103/PhysRevLett.116.055501) we reported the observation of an exceptionally stable honeycomb carbon allotrope obtained by deposition of vacuum-sublimated graphite. A family of structures can be built from absolutely dominant {sp}2-bonded carbon atoms, and may be considered as three-dimensional graphene. Such structures demonstrate high absorption capacity for gases and liquids. In this work we show that the formation of honeycomb structures is highly sensitive to the carbon evaporation temperature and deposition rates. Both parameters are controlled by the electric current flowing through thin carbon rods. Two distinctly different regimes were found. At lower electric currents almost pure honeycomb structures form owing to sublimation. At higher currents the surface-to-bulk rod melting is observed. In the latter case densification of the carbon structures and a large contribution of glassy graphite emerge. The experimental diffraction patterns from honeycomb structures filled with absorbed gases and analyzed by the advanced method are consistent with the proposed models for composites which are different for Ar, Kr and Xe atoms in carbon matrices.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Loehle, Stefan; Lein, Sebastian

A revised scientific instrument to measure simultaneously kinetic temperatures of different atoms from their optical emission profile is reported. Emission lines are simultaneously detected using one single scanning Fabry-Perot-interferometer (FPI) for a combined spectroscopic setup to acquire different emission lines simultaneously. The setup consists in a commercial Czerny-Turner spectrometer configuration which is combined with a scanning Fabry-Perot interferometer. The fast image acquisition mode of an intensified charge coupled device camera allows the detection of a wavelength interval of interest continuously while acquiring the highly resolved line during the scan of the FPI ramp. Results using this new setup are presentedmore » for the simultaneous detection of atomic nitrogen and oxygen in a high enthalpy air plasma flow as used for atmospheric re-entry research and their respective kinetic temperatures derived from the measured line profiles. The paper presents the experimental setup, the calibration procedure, and an exemplary result. The determined temperatures are different, a finding that has been published so far as due to a drawback of the experimental setup of sequential measurements, and which has now to be investigated in more detail.« less

Mechanical phenotyping of tumor cells using a microfluidic cell squeezer device

NASA Astrophysics Data System (ADS)

Khan, Zeina S.; Kamyabi, Nabiollah; Vanapalli, Siva A.

2013-03-01

Studies have indicated that cancer cells have distinct mechanical properties compared to healthy cells. We are investigating the potential of cell mechanics as a biophysical marker for diagnostics and prognosis of cancer. To establish the significance of mechanical properties for cancer diagnostics, a high throughput method is desired. Although techniques such as atomic force microscopy are very precise, they are limited in throughput for cellular mechanical property measurements. To develop a device for high throughput mechanical characterization of tumor cells, we have fabricated a microfludic cell squeezer device that contains narrow micrometer-scale pores. Fluid flow is used to drive cells into these pores mimicking the flow-induced passage of circulating tumor cells through microvasculature. By integrating high speed imaging, the device allows for the simultaneous characterization of five different parameters including the blockage pressure, cell velocity, cell size, elongation and the entry time into squeezer. We have tested a variety of in vitro cell lines, including brain and prostate cancer cell lines, and have found that the entry time is the most sensitive measurement capable of differentiating between cell lines with differing invasiveness.

Infrared Chemiluminescence Studies of Ion-Molecule Reactions in a Flowing Afterglow.

DTIC Science & Technology

1982-01-01

reaction rate constants and branching ratios have been addressed in drift tubes and flow drift systems, and the translational energy distribution of atomic...composed of about 40 thin cylindrical sections of flow tube , separated by mylar spacers and connected by precision resistors. In the region of LIF... tube radius (Albritton, 1967). For proper operation of a drift tube , ionic species of only one polarity can be present. Efficient separation of

Continuation through Singularity of Continuum Multiphase Algorithms

DTIC Science & Technology

2013-03-01

capturing simulation of two-phase flow ; a singularity- free mesoscopic simulation that bridges atomic and continuum scales; and a physics-based closure...for free surface flow . The full two-way coupling was found to be irrelevant to the overall objective of developing a closure model to allow...The method can be used for the study of single species free - surface flow , for instance, in the case of pinch-off of a liquid thread during the

Flow reversal, convection, and modeling in the DIII-D divertor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Boedo, J.A.; Porter, G.D.; Schaffer, M.J.

1998-12-01

Measurements of the parallel Mach number of background plasma in the DIII-D tokamak divertor [M. A. Mahdavi {ital et al.} in {ital Proceedings, 16th International Conference}, Montreal, 1996 (International Atomic Energy Agency, Vienna, 1997) Vol. I, p. 397] were performed using a fast scanning Mach probe. The parallel particle flow shows evidence of complex behavior such as reverse flow, i.e., flow away from the target plate, stagnant flow, and large scale convection. For detached discharges, measurements confirm predictions of convective flow towards the divertor target plate at near sound speed over large regions in the divertor. The resulting convected heatmore » flux is a dominant heat transport mechanism in the divertor. For attached discharges with high recycling, particle flow reversal in a thin region at or near the outer separatrix, thereby confirming the existence of a mechanism by which impurities can be transported away from the divertor target plates. Modeling results from the two-dimensional fluid code UEDGE [G. D. Porter and the DIII-D Team, {open_quotes}Divertor characterization experiments and modelling in DIII-D,{close_quotes} in {ital Proceedings of the 23rd European Conference on Controlled Fusion and Plasma Physics}, 24{endash}28 June 1996, Kiev, Ukraine (European Physical Society, Petit-Lancy, Switzerland, 1996), Vol. 20C, Part II, p. 699] can reproduce the main features of the experimental observations. {copyright} {ital 1998 American Institute of Physics.}« less

Photographic characterization of spark-ignition engine fuel injectors

NASA Technical Reports Server (NTRS)

Evanich, P. L.

1978-01-01

Manifold port fuel injectors suitable for use in general aviation spark-ignition engines were evaluated qualitatively on the basis of fuel spray characteristics. Photographs were taken at various fuel flow rates or pressure levels. Mechanically and electronically operated pintle injectors generally produced the most atomization. The plain-orifice injectors used on most fuel-injected general aviation engines did not atomize the fuel when sprayed into quiescent air.

The terrestrial ring current - From in situ measurements to global images using energetic neutral atoms

NASA Technical Reports Server (NTRS)

Roelof, Edmond C.; Williams, Donald J.

1988-01-01

Electrical currents flowing in the equatorial magnetosphere, first inferred from ground-based magnetic disturbances, are carried by trapped energetic ions. Spacecraft measurements have determined the spectrum and composition of those currents, and the newly developed technique of energetic-neutral-atom imaging allows the global dynamics of that entire ion population to be viewed from a single spacecraft.

Argon metastable dynamics and lifetimes in a direct current microdischarge

NASA Astrophysics Data System (ADS)

Stefanović, Ilija; Kuschel, Thomas; Schröter, Sandra; Böke, Marc

2014-09-01

In this paper we study the properties of a pulsed dc microdischarge with the continuous flow of argon. Argon metastable lifetimes are measured by tunable diode laser absorption spectroscopy (TDLAS) and are compared with calculated values which yield information about excitation and de-excitation processes. By increasing the gas flow-rate about 5 times from 10 to 50 sccm, the Arm lifetime increases from 1 to 5 μs due to the reduction of metastable quenching with gas impurities. Optical emission spectroscopy reveals nitrogen and water molecules as the main gas impurities. The estimated N2 density [N2] = 0.1% is too low to explain the measured metastable lifetimes. Water impurity was found to be the main de-excitation source of argon metastable atoms due to high quenching coefficients. The water impurity level of [H2O] = 0.15% to 1% is sufficient to bring calculated metastable lifetimes in line with experiments. The maximum value of water content in the discharge compared to the argon atoms is estimated to approximately 6%, due to the large surface to volume ratio of the microdischarge. The current pulse releases the water molecules from the electrode surface and they are either re-adsorbed in the time between 0.4 ms for [H2O] = 1% and 2.6 ms for [H2O] = 0.15% or pumped out of the discharge with the speed equal to the gas flow-rate. Depending on its partial pressure, the water impurity re-adsorption time is of the order of magnitude or less then the argon gas residence time.

Large scale motions of multiple limit-cycle high Reynolds number annular and toroidal rotor/stator cavities

NASA Astrophysics Data System (ADS)

Bridel-Bertomeu, Thibault; Gicquel, L. Y. M.; Staffelbach, G.

2017-06-01

Rotating cavity flows are essential components of industrial applications but their dynamics are still not fully understood when it comes to the relation between the fluid organization and monitored pressure fluctuations. From computer hard-drives to turbo-pumps of space launchers, designed devices often produce flow oscillations that can either destroy the component prematurely or produce too much noise. In such a context, large scale dynamics of high Reynolds number rotor/stator cavities need better understanding especially at the flow limit-cycle or associated statistically stationary state. In particular, the influence of curvature as well as cavity aspect ratio on the large scale organization and flow stability at a fixed rotating disc Reynolds number is fundamental. To probe such flows, wall-resolved large eddy simulation is applied to two different rotor/stator cylindrical cavities and one annular cavity. Validation of the predictions proves the method to be suited and to capture the disc boundary layer patterns reported in the literature. It is then shown that in complement to these disc boundary layer analyses, at the limit-cycle the rotating flows exhibit characteristic patterns at mid-height in the homogeneous core pointing the importance of large scale features. Indeed, dynamic modal decomposition reveals that the entire flow dynamics are driven by only a handful of atomic modes whose combination links the oscillatory patterns observed in the boundary layers as well as in the core of the cavity. These fluctuations form macro-structures, born in the unstable stator boundary layer and extending through the homogeneous inviscid core to the rotating disc boundary layer, causing its instability under some conditions. More importantly, the macro-structures significantly differ depending on the configuration pointing the need for deeper understanding of the influence of geometrical parameters as well as operating conditions.

Direct droplet production from a liquid film: a new gas-assisted atomization mechanism

NASA Astrophysics Data System (ADS)

Snyder, Herman E.; Reitz, Rolf D.

1998-11-01

X-ray lithography and micro-machining have been used to study gas-assisted liquid atomization in which a liquid film was impinged by a large number of sonic micro-gas jets. Three distinct breakup regimes were demonstrated. Two of these regimes share characteristics with previously observed atomization processes: a bubble bursting at a free surface (Newitt et al. 1954; Boulton-Stone & Blake 1993) and liquid sheet disintegration in a high gas/liquid relative velocity environment (Dombrowski & Johns 1963). The present work shows that suitable control of the gas/liquid interface creates a third regime, a new primary atomization mechanism, in which single liquid droplets are ejected directly from the liquid film without experiencing an intermediate ligament formation stage. The interaction produces a stretched liquid sheet directly above each gas orifice. This effectively pre-films the liquid prior to its breakup. Following this, surface tension contracts the stretched film of liquid into a sphere which subsequently detaches from the liquid sheet and is entrained by the gas jet that momentarily pierces the film. After droplet ejection, the stretched liquid film collapses, covering the gas orifice, and the process repeats. This new mechanism is capable of the efficient creation of finely atomized sprays at low droplet ejection velocities (e.g. 20 [mu]m Sauter mean diameter methanol sprays using air at 239 kPa, with air-to-liquid mass ratios below 1.0, and droplet velocities lower than 2.0 m s[minus sign]1). Independent control of the gas and the liquid flows allows the droplet creation process to be effectively de-coupled from the initial droplet momentum, a characteristic not observed with standard gas-assisted atomization mechanisms.

Trace determination of antimony by hydride generation atomic absorption spectrometry with analyte preconcentration/atomization in a dielectric barrier discharge atomizer.

PubMed

Zurynková, Pavla; Dědina, Jiří; Kratzer, Jan

2018-06-20

Atomization conditions for antimony hydride in the plasma atomizer based on a dielectric barrier discharge (DBD) with atomic absorption spectrometric detection were optimized. Argon was found as the best discharge gas under a flow rate of 50 mL min - 1 while the DBD power was optimum at 30 W. Analytical figures of merit including interference study of As, Se and Bi have been subsequently investigated and the results compared to those found in an externally heated quartz tube atomizer (QTA). The limit of detection (LOD) reached in DBD (0.15 ng mL -1  Sb) is comparable to that observed in QTA (0.14 ng mL -1  Sb). Finally, possibility of Sb preconcentration by stibane in situ trapping in a DBD atomizer was studied. For trapping time of 300 s, the preconcentration efficiency and LOD, respectively, were 103 ± 2% and 0.02 ng mL -1 . Copyright © 2018 Elsevier B.V. All rights reserved.

Ignition and combustion characteristics of metallized propellants, phase 2

NASA Technical Reports Server (NTRS)

Mueller, D. C.; Turns, S. R.

1994-01-01

Experimental and analytical investigations focusing on aluminum/hydrocarbon gel droplet secondary atomization and its effects on gel-fueled rocket engine performance are being conducted. A single laser sheet sizing/velocimetry diagnostic technique, which should eliminate sizing bias in the data collection process, has been designed and constructed to overcome limitations of the two-color forward-scatter technique used in previous work. Calibration of this system is in progress and the data acquisition/validation code is being written. Narrow-band measurements of radiant emission, discussed in previous reports, will be used to determine if aluminum ignition has occurred in a gel droplet. A one-dimensional model of a gel-fueled rocket combustion chamber, described in earlier reports, has been exercised in conjunction with a two-dimensional, two-phase nozzle code to predict the performance of an aluminum/hydrocarbon fueled engine. Estimated secondary atomization effects on propellant burnout distance, condensed particle radiation losses to the chamber walls, and nozzle two phase flow losses are also investigated. Calculations indicate that only modest secondary atomization is required to significantly reduce propellant burnout distances, aluminum oxide residual size, and radiation heat losses. Radiation losses equal to approximately 2-13 percent of the energy released during combustion were estimated, depending on secondary atomization intensity. A two-dimensional, two-phase nozzle code was employed to estimate radiation and nozzle two phase flow effects on overall engine performance. Radiation losses yielded a one percent decrease in engine Isp. Results also indicate that secondary atomization may have less effect on two-phase losses than it does on propellant burnout distance and no effect if oxide particle coagulation and shear induced droplet breakup govern oxide particle size. Engine Isp was found to decrease from 337.4 to 293.7 seconds as gel aluminum mass loading was varied from 0-70 wt percent. Engine Isp efficiencies, accounting for radiation and two phase flow effects, on the order of 0.946 were calculated for a 60 wt percent gel, assuming a fragmentation ratio of five.

Revealing flow behaviors of metallic glass based on activation of flow units

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ge, T. P.; Wang, W. H.; Bai, H. Y., E-mail: hybai@iphy.ac.cn

2016-05-28

Atomic level flow plays a critical role in the mechanical behavior of metallic glass (MG) while the connection between the flow and the heterogeneous microstructure of the glass remains unclear. We describe the heterogeneity of MGs as the elastic matrix with “inclusions” of nano-scale liquid-like flow units, and the plastic flow behavior of MGs is considered to be accommodated by the flow units. We show that the model can explain the various deformation behaviors, the transformation from inhomogeneous deformation to homogeneous flow upon strain rate or temperature, and the deformation map in MGs, which might provide insights into the flowmore » mechanisms in glasses and inspiration for improving the plasticity of MGs.« less

Electric oxygen-iodine laser discharge scaling and laser performance

NASA Astrophysics Data System (ADS)

Woodard, Brian S.

In 2004, a research partnership between the University of Illinois and CU Aerospace demonstrated the first electric discharge pumped oxygen-iodine laser referred to as ElectricOIL. This exciting improvement over the standard oxygen-iodine laser utilizes a gas discharge to produce the necessary electronically-excited molecular oxygen, O2(a 1Delta), that serves as the energy reservoir in the laser system. Pumped by a near-resonant energy transfer, the atomic iodine lases on the I(2P1/2) → I(2P3/2) transition at 1315 nm. Molecular oxygen diluted with helium and a small fraction of nitric oxide flows through a radiofrequency discharge where O2(a 1Delta) and many other excited species are created. Careful investigations to understand the benefits and problems associated with these other states in the laser system allowed this team to succeed where other research groups had failed, and after the initial demonstration, the ElectricOIL research focus shifted to increasing the efficiencies along with the output laser energy. Among other factors, the laser power scales with the flow rate of oxygen in the desired excited state. Therefore, high yields of O2(a 1Delta) are desired along with high input oxygen flow rates. In the early ElectricOIL experiments, the pressure in the discharge was approximately 10 Torr, but increased flow rates forced the pressure to between 50 and 60 Torr requiring a number of new discharge designs in order to produce similar yields of O2(a1Delta) efficiently. Experiments were conducted with only the electric discharge portion of the laser system using emission diagnostics to study the effects of changing the discharge geometry, flow residence time, and diluent. The power carried by O2(a 1Delta) is the maximum power that could be extracted from the laser, and the results from these studies showed approximately 2500 W stored in the O2(a1Delta) state. Transferring this energy into the atomic iodine has been another challenge in ElectricOIL as experiments have shown that the iodine is pumped into the excited state slower than is predicted by the known kinetics, resulting in reduced output power. An elementary model is presented that may partially explain this problem. Larger laser resonator volumes are employed to improve power extraction by providing more flow time for iodine pumping. The results presented in this work in conjunction with the efforts of others led to ElectricOIL scaling from 200 mW in the initial demonstration to nearly 500 W.

Laser-Induced Translative Hydrodynamic Mass Snapshots: Noninvasive Characterization and Predictive Modeling via Mapping at Nanoscale

NASA Astrophysics Data System (ADS)

Wang, X. W.; Kuchmizhak, A. A.; Li, X.; Juodkazis, S.; Vitrik, O. B.; Kulchin, Yu. N.; Zhakhovsky, V. V.; Danilov, P. A.; Ionin, A. A.; Kudryashov, S. I.; Rudenko, A. A.; Inogamov, N. A.

2017-10-01

Subwavelength structures (meta-atoms) with artificially engineered permittivity and permeability have shown promising applications for guiding and controlling the flow of electromagnetic energy on the nanoscale. Ultrafast laser nanoprinting emerges as a promising single-step, green and flexible technology in fabricating large-area arrays of meta-atoms through the translative or ablative modification of noble-metal thin films. Ultrafast laser energy deposition in noble-metal films produces irreversible, intricate nanoscale translative mass redistributions after resolidification of the transient thermally assisted hydrodynamic melt perturbations. Such mass redistribution results in the formation of a radially symmetric frozen surface with modified hidden nanofeatures, which strongly affect the optical response harnessed in plasmonic sensing and nonlinear optical applications. Here, we demonstrate that side-view electron microscopy and ion-beam cross sections together with low-energy electron x-ray dispersion microscopy provide exact information about such three-dimensional patterns, enabling an accurate acquisition of their cross-sectional mass distributions. Such nanoscale solidified structures are theoretically modeled, considering the underlying physical processes associated with laser-induced energy absorption, electron-ion energy exchange, acoustic relaxation, and hydrodynamic flows. A theoretical approach, separating slow and fast physical processes and combining hybrid analytical two-temperature calculations, scalable molecular-dynamics simulations, and a semianalytical thin-shell model is synergistically applied. These advanced characterization approaches are required for a detailed modeling of near-field electromagnetic response and pave the way to a fully automated noninvasive in-line control of a high-throughput and large-scale laser fabrication. This theoretical modeling provides an accurate prediction of scales and topographies of the laser-fabricated meta-atoms and metasurfaces.

Deposition of device quality, low hydrogen content, hydrogenated amorphous silicon at high deposition rates with increased stability using the hot wire filament technique

DOEpatents

Molenbroek, Edith C.; Mahan, Archie Harvin; Gallagher, Alan C.

2000-09-26

A method or producing hydrogenated amorphous silicon on a substrate, comprising the steps of: positioning the substrate in a deposition chamber at a distance of about 0.5 to 3.0 cm from a heatable filament in the deposition chamber; maintaining a pressure in said deposition chamber in the range of about 10 to 100 millitorr and pressure times substrate-filament spacing in the range of about 10 to 100 millitorr-cm, heating the filament to a temperature in the range of about 1,500 to 2,000.degree. C., and heating the substrate to a surface temperature in the range of about 280 to 475.degree. C.; and flowing silicohydride gas into the deposition chamber with said heated filament, decomposing said silicohydride gas into silicon and hydrogen atomic species and allowing products of gas reactions between said atomic species and the silicohydride gas to migrate to and deposit on said substrate while adjusting and maintaining said pressure times substrate-filament spacing in said deposition chamber at a value in said 10 to 100 millitorr range to produce statistically about 3 to 50 atomic collisions between the silicon and hydrogen atomic species migrating to said substrate and undecomposed molecules of the silane or other silicohydride gas in the deposition chamber.

Data Base for CFD Validation

NASA Technical Reports Server (NTRS)

Deiwert, George S.

1997-01-01

The flow behind the shock wave formed around objects which fly at hypervelocity behaves differently from that of a perfect gas. Molecules become vibrationally excited, dissociated, and ionized. The hot gas may emit or absorb radiation. When the atoms produced by dissociation reach the wall surface, chemical reactions, including recombination, may occur. The thermochemical phenomena of vibration, dissociation, ionization, surface chemical reaction, and radiation are referred to commonly as high-temperature real-gas phenomena. The phenomena cause changes in the dynamic behavior of the flow and the surface pressure and heat transfer distribution around the object. The character of a real gas is described by the internal degrees of freedom and state of constituent molecules; nitrogen and oxygen for air. The internal energy states, rotation, vibration and electronic, of the molecules are excited and, in the limit, the molecular bonds are exceeded and the gas dissociated into atomic and, possibly, ionic constituents. The process of energy transfer causing excitation, dissociation and recombination is a rate process controlled by particle collisions. Binary, two-body, collisions are sufficient to cause internal excitation, dissociation and ionization while three-body collisions are required to recombine the particles into molecular constituents. If the rates of energy transfer are fast with respect to the local fluid dynamic time scale the gas is in, or nearly in, equilibrium. If the energy transfer rates are very slow the gas can be described as frozen. In all other instances, wherein any of the energy exchange rates are comparable to the local fluid time scale, the gas will be thermally or chemically reacting and out of equilibrium. Real gas thermochemical nonequilibrium processes are important in the determination of aerodynamic heating; both convective (including wall catalytic effects) and radiative heating. To illustrate this we consider the hypervelocity flow over a bluff body typical of an atmospheric entry vehicle or an aerospace transfer vehicle (ASTV). The qualitative aspects of a hypersonic flow field over a bluff body are discussed in two parts, forebody and afterbody, with attention to which particular physical effects must be included in an analysis. This will indicate what type of numerical modeling will be adequate in each region of the flow. A bluff forebody flow field is dominated by the presence of the strong bow shock wave and the consequent heating, and chemical reaction of the gas. At high altitude hypersonic flight conditions the thermal excitation and chemical reaction of the gas occur slowly enough that a significant portion of the flow field is in a state of thermochemical nonequilibrium. A second important effect is the presence of the thick boundary layer along the forebody surface. In this region there are large thermal and chemical species gradients due to the interaction of the gas with the wall. Also at high altitudes the shock wave and the boundary layer may become so thick that they merge; in this case the entire shock layer is dominated by viscous effects.

Ligament Mediated Fragmentation of Viscoelastic Liquids

NASA Astrophysics Data System (ADS)

Keshavarz, Bavand; Houze, Eric C.; Moore, John R.; Koerner, Michael R.; McKinley, Gareth H.

2016-10-01

The breakup and atomization of complex fluids can be markedly different than the analogous processes in a simple Newtonian fluid. Atomization of paint, combustion of fuels containing antimisting agents, as well as physiological processes such as sneezing are common examples in which the atomized liquid contains synthetic or biological macromolecules that result in viscoelastic fluid characteristics. Here, we investigate the ligament-mediated fragmentation dynamics of viscoelastic fluids in three different canonical flows. The size distributions measured in each viscoelastic fragmentation process show a systematic broadening from the Newtonian solvent. In each case, the droplet sizes are well described by Gamma distributions which correspond to a fragmentation-coalescence scenario. We use a prototypical axial step strain experiment together with high-speed video imaging to show that this broadening results from the pronounced change in the corrugated shape of viscoelastic ligaments as they separate from the liquid core. These corrugations saturate in amplitude and the measured distributions for viscoelastic liquids in each process are given by a universal probability density function, corresponding to a Gamma distribution with nmin=4 . The breadth of this size distribution for viscoelastic filaments is shown to be constrained by a geometrical limit which can not be exceeded in ligament-mediated fragmentation phenomena.

IMPACT OF PLANETARY GRAVITATION ON HIGH-PRECISION NEUTRAL ATOM MEASUREMENTS

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kucharek, H.; Möbius, E.; Lee, M. A.

2015-10-15

Measurements of energetic neutral atoms (ENAs) have been extremely successful in providing very important information on the physical processes inside and outside of our heliosphere. For instance, recent Interstellar Boundary Explorer (IBEX) observations have provided new insights into the local interstellar environment and improved measurements of the interstellar He temperature, velocity, and direction of the interstellar flow vector. Since particle collisions are rare, and radiation pressure is negligible for these neutrals, gravitational forces mainly determine the trajectories of neutral He atoms. Depending on the distance of an ENA to the source of a gravitational field and its relative speed andmore » direction, this can result in significant deflection and acceleration. In this paper, we investigate the impact of the gravitational effects of Earth, the Moon, and Jupiter on ENA measurements performed in Earth’s orbit. The results show that current analysis of the interstellar neutral parameters by IBEX is not significantly affected by planetary gravitational effects. We further studied the possibility of whether or not the Helium focusing cone of the Sun and Jupiter could be measured by IBEX and whether or not these cones could be used as an independent measure of the temperature of interstellar Helium.« less

Ligament Mediated Fragmentation of Viscoelastic Liquids.

PubMed

Keshavarz, Bavand; Houze, Eric C; Moore, John R; Koerner, Michael R; McKinley, Gareth H

2016-10-07

The breakup and atomization of complex fluids can be markedly different than the analogous processes in a simple Newtonian fluid. Atomization of paint, combustion of fuels containing antimisting agents, as well as physiological processes such as sneezing are common examples in which the atomized liquid contains synthetic or biological macromolecules that result in viscoelastic fluid characteristics. Here, we investigate the ligament-mediated fragmentation dynamics of viscoelastic fluids in three different canonical flows. The size distributions measured in each viscoelastic fragmentation process show a systematic broadening from the Newtonian solvent. In each case, the droplet sizes are well described by Gamma distributions which correspond to a fragmentation-coalescence scenario. We use a prototypical axial step strain experiment together with high-speed video imaging to show that this broadening results from the pronounced change in the corrugated shape of viscoelastic ligaments as they separate from the liquid core. These corrugations saturate in amplitude and the measured distributions for viscoelastic liquids in each process are given by a universal probability density function, corresponding to a Gamma distribution with n_{min}=4. The breadth of this size distribution for viscoelastic filaments is shown to be constrained by a geometrical limit which can not be exceeded in ligament-mediated fragmentation phenomena.

A Computational and Experimental Investigation of Shear Coaxial Jet Atomization

NASA Technical Reports Server (NTRS)

Ibrahim, Essam A.; Kenny, R. Jeremy; Walker, Nathan B.

2006-01-01

The instability and subsequent atomization of a viscous liquid jet emanated into a high-pressure gaseous surrounding is studied both computationally and experimentally. Liquid water issued into nitrogen gas at elevated pressures is used to simulate the flow conditions in a coaxial shear injector element relevant to liquid propellant rocket engines. The theoretical analysis is based on a simplified mathematical formulation of the continuity and momentum equations in their conservative form. Numerical solutions of the governing equations subject to appropriate initial and boundary conditions are obtained via a robust finite difference scheme. The computations yield real-time evolution and subsequent breakup characteristics of the liquid jet. The experimental investigation utilizes a digital imaging technique to measure resultant drop sizes. Data were collected for liquid Reynolds number between 2,500 and 25,000, aerodynamic Weber number range of 50-500 and ambient gas pressures from 150 to 1200 psia. Comparison of the model predictions and experimental data for drop sizes at gas pressures of 150 and 300 psia reveal satisfactory agreement particularly for lower values of investigated Weber number. The present model is intended as a component of a practical tool to facilitate design and optimization of coaxial shear atomizers.

Investigation of Spray Cooling Schemes for Dynamic Thermal Management

NASA Astrophysics Data System (ADS)

Yata, Vishnu Vardhan Reddy

This study aims to investigate variable flow and intermittent flow spray cooling characteristics for efficiency improvement in active two-phase thermal management systems. Variable flow spray cooling scheme requires control of pump input voltage (or speed), while intermittent flow spray cooling scheme requires control of solenoid valve duty cycle and frequency. Several testing scenarios representing dynamic heat load conditions are implemented to characterize the overall performance of variable flow and intermittent flow spray cooling cases in comparison with the reference, steady flow spray cooling case with constant flowrate, continuous spray cooling. Tests are conducted on a small-scale, closed loop spray cooling system featuring a pressure atomized spray nozzle. HFE-7100 dielectric liquid is selected as the working fluid. Two types of test samples are prepared on 10 mm x 10 mm x 2 mm copper substrates with matching size thick film resistors attached onto the opposite side, to generate heat and simulate high heat flux electronic devices. The test samples include: (i) plain, smooth surface, and (ii) microporous surface featuring 100 ?m thick copper-based coating prepared by dual stage electroplating technique. Experimental conditions involve HFE-7100 at atmospheric pressure and 30°C and 10°C subcooling. Steady flow spray cooling tests are conducted at flow rates of 2-5 ml/cm2.s, by controlling the heat flux in increasing steps, and recording the corresponding steady-state temperatures to obtain cooling curves in the form of surface superheat vs. heat flux. Variable flow and intermittent flow spray cooling tests are done at selected flowrate and subcooling conditions to investigate the effects of dynamic flow conditions on maintaining the target surface temperatures defined based on reference steady flow spray cooling performance.

Horizon in random matrix theory, the Hawking radiation, and flow of cold atoms.

PubMed

Franchini, Fabio; Kravtsov, Vladimir E

2009-10-16

We propose a Gaussian scalar field theory in a curved 2D metric with an event horizon as the low-energy effective theory for a weakly confined, invariant random matrix ensemble (RME). The presence of an event horizon naturally generates a bath of Hawking radiation, which introduces a finite temperature in the model in a nontrivial way. A similar mapping with a gravitational analogue model has been constructed for a Bose-Einstein condensate (BEC) pushed to flow at a velocity higher than its speed of sound, with Hawking radiation as sound waves propagating over the cold atoms. Our work suggests a threefold connection between a moving BEC system, black-hole physics and unconventional RMEs with possible experimental applications.

Dynamics of fractional condensation of a substance on a probe for spectral analysis

NASA Astrophysics Data System (ADS)

Zakharov, Yu. A.; Kokorina, O. B.; Lysogorskiĭ, Yu. V.; Sevastianov, A. A.

2008-11-01

The fractional separation of trace metals on a cold tungsten probe from salt matrix vapor, which interferes with the spectral analysis, is studied. The spatial structure of the vapor flows of sodium chloride, potassium sulfate, and indium atoms is visualized at characteristic wavelengths as they interact with the probe. The vapor flow rate and the probe orientation were varied. It is found that the smoke of the matrix does not prevent the deposition of the metal on the probe because of spatial separation of these fractions and that the detrimental effect of thermal gas expansion and other factors is eliminated. The sensitivity of the atomic absorption analysis of indium impurities in these salts is increased by an order of magnitude.

Time-dependent density-functional theory simulation of local currents in pristine and single-defect zigzag graphene nanoribbons

DOE Office of Scientific and Technical Information (OSTI.GOV)

He, Shenglai, E-mail: shenglai.he@vanderbilt.edu; Russakoff, Arthur; Li, Yonghui

2016-07-21

The spatial current distribution in H-terminated zigzag graphene nanoribbons (ZGNRs) under electrical bias is investigated using time-dependent density-functional theory solved on a real-space grid. A projected complex absorbing potential is used to minimize the effect of reflection at simulation cell boundary. The calculations show that the current flows mainly along the edge atoms in the hydrogen terminated pristine ZGNRs. When a vacancy is introduced to the ZGNRs, loop currents emerge at the ribbon edge due to electrons hopping between carbon atoms of the same sublattice. The loop currents hinder the flow of the edge current, explaining the poor electric conductancemore » observed in recent experiments.« less

Atomization simulations using an Eulerian-VOF-Lagrangian method

NASA Technical Reports Server (NTRS)

Chen, Yen-Sen; Shang, Huan-Min; Liaw, Paul; Chen, C. P.

1994-01-01

This paper summarizes the technical development and validation of a multiphase computational fluid dynamics (CFD) numerical method using the volume-of-fluid (VOF) model and a Lagrangian tracking model which can be employed to analyze general multiphase flow problems with free surface mechanism. The gas-liquid interface mass, momentum and energy conservations are modeled by continuum surface mechanisms. A new solution method is developed such that the present VOF model can be applied for all-speed flow regimes. The objectives of the present study are to develop and verify the fractional volume-of-fluid cell partitioning approach into a predictor-corrector algorithm and to demonstrate the effectiveness of the present innovative approach by simulating benchmark problems including the coaxial jet atomization.

Electric discharges in air - Near infrared emission spectrum.

NASA Technical Reports Server (NTRS)

Benesch, W. M.; Saum, K. A.

1972-01-01

The emission from glow discharges in flowing air has been investigated in the 1- to 5-micron wavelength region with a vacuum spectrometer. Most of the spectral features observed in the pressure range of .5 to 10 torr are identified, including atomic lines of OI, NI, and HI and molecular bands of N2, NO, N2O, CO2, and CO. The spectra are presented as a function of pressure and a table compiled of the atomic lines. Of particular interest are the contrasts between the emission of the air discharge and that of the pure gases, nitrogen and oxygen. In addition, the results of studies of several discharge modes, employing steady voltages and pulsed, provide data on details of the energy flow within the plasma.

Ion implantation disorder in strained-layer superlattices

NASA Astrophysics Data System (ADS)

Arnold, G. W.; Picraux, S. T.; Peercy, P. S.; Myers, D. R.; Biefeld, R. M.; Dawson, L. R.

Cantilever beam bending and RBS channeling measurements have been used to examine implantation induced disorder and stress buildup in InO 2GaO 8As/GaAs SLS structures. The critical fluence for saturation of compressive stress occurs prior to amorphous layer formation and is followed by stress relief. For all the ions the maximum ion induced stress scales with energy density into atomic processes and stress relief occurs above approximately 1x10 to the 20th keV/1 cubic cm. Stress relief is more pronounced for the SLSs than for bulk GaAs. Stress relief may lead to slip or other forms of inelastic material flow in SLSs, which would be undesirable for active regions in device applications. Such material flow may be avoided by limiting maximum fluences or by multiple step or simultaneous implantation and annealing for high fluences.

Fundamental Mechanisms, Predictive Modeling, and Novel Aerospace Applications of Plasma Assisted Combustion: Laminar Flow Reactor and Nanoparticle Studies at Low to Intermediate Temperatures. Program Overview

DTIC Science & Technology

2009-11-04

plasma enhanced combustion in flow  reactors and flames Motivation •Nano‐ particles  are known to be ionized more easily than  molecules  and atoms (due to...aluminum nano‐ particles  at high  temperature (~1100 K), providing a strong driving force for ion  transport •Nano‐ particles  are chemically and catalytically...active in plasma  •Functionalized nano‐ particles  may enhance the effectiveness of  plasma  Functionalized graphene sheet colloids enhance fuel

Basic governing equations for the flight regimes of aeroassisted orbital transfer vehicles

NASA Technical Reports Server (NTRS)

Lee, J.-H.

1984-01-01

The basic governing equations for the low-density, high-enthalpy flow regimes expected in the shock layers over the heat shields of the proposed aeroassisted orbital transfer vehicles are derived by combining and extending existing theories. The conservation equations are derived from gas kinetic principles for a four-component ionized gas consisting of neutral molecules, neutral atoms, singly ionized ions, and electrons, assuming a continuum flow. The differences among translational-rotational, vibrational, and electron temperatures are accounted for, as well as chemical nonequilibrium and electric-charge separation. Expressions for convective and viscous fluxes, transport properties, and the terms representing interactions among various energy modes are given explicitly. The expressions for the rate of electron-vibration energy transfer, which violates the Landau-Teller conditions, is derived by solving the system of master equations accounting for the multiple-level transitions.

Basic Governing Equations for the Flight Regimes of Aeroassisted Orbital Transfer Vehicles

NASA Technical Reports Server (NTRS)

Lee, Jong-Hun

1985-01-01

The basic governing equations for the low-density, high-enthalpy flow regimes expected in the shock layers over the heat shields of the proposed aeroassisted orbital transfer vehicles are derived by combining and extending existing theories. The conservation equations are derived from gas kinetic principles for a four-component ionized gas consisting of neutral molecules, neutral atoms, singly ionized ions, and electrons, assuming a continuum flow. The differences among translational-rotational, vibrational, and electron temperatures are accounted for, as well as chemical nonequilibrium and electric-charge separation. Expressions for convective and viscous fluxes, transport properties, and the terms representing interactions among various energy modes are explicitly given. The expressions for the rate of electron-vibration energy transfer, which violates the Landau-Teller conditions, are derived by solving the system of master equations accounting for the multiple-level transitions.

Size-dependent microstructures in rapidly solidified uranium-niobium powder particles

DOE PAGES

McKeown, Joseph T.; Hsiung, Luke L.; Park, Jong M.; ...

2016-06-14

The microstructures of rapidly solidified U-6wt%Nb powder particles synthesized by centrifugal atomization were characterized using scanning electron microscopy and transmission electron microscopy. Observed variations in microstructure are related to particle sizes. All of the powder particles exhibited a two-zone microstructure. The formation of this two-zone microstructure is described by a transition from solidification controlled by internal heat flow and high solidification rate during recalescence (micro-segregation-free or partitionless growth) to solidification controlled by external heat flow with slower solidification rates (dendritic growth with solute redistribution). The extent of partitionless solidification increased with decreasing particle size due to larger undercoolings in smallermore » particles prior to solidification. The metastable phases that formed are related to variations in Nb concentration across the particles. Lastly, the microstructures of the powders were heavily twinned.« less

Validation of chemistry models employed in a particle simulation method

NASA Technical Reports Server (NTRS)

Haas, Brian L.; Mcdonald, Jeffrey D.

1991-01-01

The chemistry models employed in a statistical particle simulation method, as implemented in the Intel iPSC/860 multiprocessor computer, are validated and applied. Chemical relaxation of five-species air in these reservoirs involves 34 simultaneous dissociation, recombination, and atomic-exchange reactions. The reaction rates employed in the analytic solutions are obtained from Arrhenius experimental correlations as functions of temperature for adiabatic gas reservoirs in thermal equilibrium. Favorable agreement with the analytic solutions validates the simulation when applied to relaxation of O2 toward equilibrium in reservoirs dominated by dissociation and recombination, respectively, and when applied to relaxation of air in the temperature range 5000 to 30,000 K. A flow of O2 over a circular cylinder at high Mach number is simulated to demonstrate application of the method to multidimensional reactive flows.

Numerical modeling of carrier gas flow in atomic layer deposition vacuum reactor: A comparative study of lattice Boltzmann models

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pan, Dongqing; Chien Jen, Tien; Li, Tao

2014-01-15

This paper characterizes the carrier gas flow in the atomic layer deposition (ALD) vacuum reactor by introducing Lattice Boltzmann Method (LBM) to the ALD simulation through a comparative study of two LBM models. Numerical models of gas flow are constructed and implemented in two-dimensional geometry based on lattice Bhatnagar–Gross–Krook (LBGK)-D2Q9 model and two-relaxation-time (TRT) model. Both incompressible and compressible scenarios are simulated and the two models are compared in the aspects of flow features, stability, and efficiency. Our simulation outcome reveals that, for our specific ALD vacuum reactor, TRT model generates better steady laminar flow features all over the domainmore » with better stability and reliability than LBGK-D2Q9 model especially when considering the compressible effects of the gas flow. The LBM-TRT is verified indirectly by comparing the numerical result with conventional continuum-based computational fluid dynamics solvers, and it shows very good agreement with these conventional methods. The velocity field of carrier gas flow through ALD vacuum reactor was characterized by LBM-TRT model finally. The flow in ALD is in a laminar steady state with velocity concentrated at the corners and around the wafer. The effects of flow fields on precursor distributions, surface absorptions, and surface reactions are discussed in detail. Steady and evenly distributed velocity field contribute to higher precursor concentration near the wafer and relatively lower particle velocities help to achieve better surface adsorption and deposition. The ALD reactor geometry needs to be considered carefully if a steady and laminar flow field around the wafer and better surface deposition are desired.« less

DSMC Modeling of Flows with Recombination Reactions

DTIC Science & Technology

2017-06-23

Rogasinsky, “Analysis of the numerical techniques of the direct simulation Monte Carlo method in the rarefied gas dynamics,” Russ. J. Numer. Anal. Math ...reflection in steady flows,” Comput. Math . Appl. 35(1-2), 113–126 (1998). 45K. L. Wray, “Shock-tube study of the recombination of O atoms by Ar catalysts at

Roles of additives and surface control in slurry atomization

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tsai, S.C.

1990-03-01

This quarterly report describes a quantitative correlation between the flow behavior index of a micronized coal slurry and the interparticular van der Waals attraction force as measured by the Hamaker constant. Preliminary results on the effects of interparticular electrostatic repulsion and the liquid viscosity on both the flow behavior and the relative viscosity are also presented.

High-dimensional atom localization via spontaneously generated coherence in a microwave-driven atomic system.

PubMed

Wang, Zhiping; Chen, Jinyu; Yu, Benli

2017-02-20

We investigate the two-dimensional (2D) and three-dimensional (3D) atom localization behaviors via spontaneously generated coherence in a microwave-driven four-level atomic system. Owing to the space-dependent atom-field interaction, it is found that the detecting probability and precision of 2D and 3D atom localization behaviors can be significantly improved via adjusting the system parameters, the phase, amplitude, and initial population distribution. Interestingly, the atom can be localized in volumes that are substantially smaller than a cubic optical wavelength. Our scheme opens a promising way to achieve high-precision and high-efficiency atom localization, which provides some potential applications in high-dimensional atom nanolithography.

Atomization of Wall-Bounded Two-Phase Flows (Preprint)

DTIC Science & Technology

2006-11-07

are given in Fig. 2. In the Rayleigh mode hydrodynamic instabilities produced by surface tension cause the jet surface to undulate [16]. Eventually...18], hydrodynamic instabilities [16] or the interaction of vortices in the gas phase [19]. Various mechanisms, discussed in the Atomization...width of the leading edge of the sheet. This regime is analogous to the Rayleigh mode in jets— hydrodynamic instabilities cause the surface of the

Atomic Oxygen Cleaning Shown to Remove Organic Contaminants at Atmospheric Pressure

NASA Technical Reports Server (NTRS)

Rutledge, Sharon K.

1998-01-01

The NASA Lewis Research Center has developed and filed for a patent on a method to produce atomic oxygen at atmospheric pressure by using a direct current arc in a gas flow mixture of oxygen and helium. A prototype device has been tested for its ability to remove various soot residues from surfaces exposed to fire, and various varnishes such as acrylic and egg white.

Electrical characterization of grain boundaries of CZTS thin films using conductive atomic force microscopy techniques

DOE Office of Scientific and Technical Information (OSTI.GOV)

Muhunthan, N.; Singh, Om Pal; Toutam, Vijaykumar, E-mail: toutamvk@nplindia.org

2015-10-15

Graphical abstract: Experimental setup for conducting AFM (C-AFM). - Highlights: • Cu{sub 2}ZnSnS{sub 4} (CZTS) thin film was grown by reactive co-sputtering. • The electronic properties were probed using conducting atomic force microscope, scanning Kelvin probe microscopy and scanning capacitance microscopy. • C-AFM current flow mainly through grain boundaries rather than grain interiors. • SKPM indicated higher potential along the GBs compared to grain interiors. • The SCM explains that charge separation takes place at the interface of grain and grain boundary. - Abstract: Electrical characterization of grain boundaries (GB) of Cu-deficient CZTS (Copper Zinc Tin Sulfide) thin films wasmore » done using atomic force microscopic (AFM) techniques like Conductive atomic force microscopy (CAFM), Kelvin probe force microscopy (KPFM) and scanning capacitance microscopy (SCM). Absorbance spectroscopy was done for optical band gap calculations and Raman, XRD and EDS for structural and compositional characterization. Hall measurements were done for estimation of carrier mobility. CAFM and KPFM measurements showed that the currents flow mainly through grain boundaries (GB) rather than grain interiors. SCM results showed that charge separation mainly occurs at the interface of grain and grain boundaries and not all along the grain boundaries.« less

DOE Office of Scientific and Technical Information (OSTI.GOV)

Thayer, K.J.

The past year has seen several of the Physics Division`s new research projects reach major milestones with first successful experiments and results: the atomic physics station in the Basic Energy Sciences Research Center at the Argonne Advanced Photon Source was used in first high-energy, high-brilliance x-ray studies in atomic and molecular physics; the Short Orbit Spectrometer in Hall C at the Thomas Jefferson National Accelerator (TJNAF) Facility that the Argonne medium energy nuclear physics group was responsible for, was used extensively in the first round of experiments at TJNAF; at ATLAS, several new beams of radioactive isotopes were developed andmore » used in studies of nuclear physics and nuclear astrophysics; the new ECR ion source at ATLAS was completed and first commissioning tests indicate excellent performance characteristics; Quantum Monte Carlo calculations of mass-8 nuclei were performed for the first time with realistic nucleon-nucleon interactions using state-of-the-art computers, including Argonne`s massively parallel IBM SP. At the same time other future projects are well under way: preparations for the move of Gammasphere to ATLAS in September 1997 have progressed as planned. These new efforts are imbedded in, or flowing from, the vibrant ongoing research program described in some detail in this report: nuclear structure and reactions with heavy ions; measurements of reactions of astrophysical interest; studies of nucleon and sub-nucleon structures using leptonic probes at intermediate and high energies; atomic and molecular structure with high-energy x-rays. The experimental efforts are being complemented with efforts in theory, from QCD to nucleon-meson systems to structure and reactions of nuclei. Finally, the operation of ATLAS as a national users facility has achieved a new milestone, with 5,800 hours beam on target for experiments during the past fiscal year.« less

Study of nitrogen flowing afterglow with mercury vapor injection

DOE Office of Scientific and Technical Information (OSTI.GOV)

Mazánková, V., E-mail: mazankova@fch.vutbr.cz; Krčma, F.; Trunec, D.

2014-10-21

The reaction kinetics in nitrogen flowing afterglow with mercury vapor addition was studied by optical emission spectroscopy. The DC flowing post-discharge in pure nitrogen was created in a quartz tube at the total gas pressure of 1000 Pa and discharge power of 130 W. The mercury vapors were added into the afterglow at the distance of 30 cm behind the active discharge. The optical emission spectra were measured along the flow tube. Three nitrogen spectral systems – the first positive, the second positive, and the first negative, and after the mercury vapor addition also the mercury resonance line at 254more » nm in the spectrum of the second order were identified. The measurement of the spatial dependence of mercury line intensity showed very slow decay of its intensity and the decay rate did not depend on the mercury concentration. In order to explain this behavior, a kinetic model for the reaction in afterglow was developed. This model showed that the state Hg(6 {sup 3}P{sub 1}), which is the upper state of mercury UV resonance line at 254 nm, is produced by the excitation transfer from nitrogen N{sub 2}(A{sup 3}Σ{sup +}{sub u}) metastables to mercury atoms. However, the N{sub 2}(A{sup 3}Σ{sup +}{sub u}) metastables are also produced by the reactions following the N atom recombination, and this limits the decay of N{sub 2}(A{sup 3}Σ{sup +}{sub u}) metastable concentration and results in very slow decay of mercury resonance line intensity. It was found that N atoms are the most important particles in this late nitrogen afterglow, their volume recombination starts a chain of reactions which produce excited states of molecular nitrogen. In order to explain the decrease of N atom concentration, it was also necessary to include the surface recombination of N atoms to the model. The surface recombination was considered as a first order reaction and wall recombination probability γ = (1.35 ± 0.04) × 10{sup −6} was determined from the experimental data. Also sensitivity analysis was applied for the analysis of kinetic model in order to reveal the main control parameters in the model.« less

Measuring heterogenous stress fields in a 3D colloidal glass

NASA Astrophysics Data System (ADS)

Lin, Neil; Bierbaum, Matthew; Bi, Max; Sethna, James; Cohen, Itai

Glass in our common experience is hard and fragile. But it still bends, yields, and flows slowly under loads. The yielding of glass, a well documented yet not fully understood flow behavior, is governed by the heterogenous local stresses in the material. While resolving stresses at the atomic scale is not feasible, measurements of stresses at the single particle level in colloidal glasses, a widely used model system for atomic glasses, has recently been made possible using Stress Assessment from Local Structural Anisotropy (SALSA). In this work, we use SALSA to visualize the three dimensional stress network in a hard-sphere glass during start-up shear. By measuring the evolution of this stress network we identify local-yielding. We find that these local-yielding events often require only minimal structural rearrangement and as such have most likely been ignored in previous analyses. We then relate these micro-scale yielding events to the macro-scale flow behavior observed using bulk measurements.

Performance estimation of a Venturi scrubber using a computational model for capturing dust particles with liquid spray.

PubMed

Pak, S I; Chang, K S

2006-12-01

A Venturi scrubber has dispersed three-phase flow of gas, dust, and liquid. Atomization of a liquid jet and interaction between the phases has a large effect on the performance of Venturi scrubbers. In this study, a computational model for the interactive three-phase flow in a Venturi scrubber has been developed to estimate pressure drop and collection efficiency. The Eulerian-Lagrangian method is used to solve the model numerically. Gas flow is solved using the Eulerian approach by using the Navier-Stokes equations, and the motion of dust and liquid droplets, described by the Basset-Boussinesq-Oseen (B-B-O) equation, is solved using the Lagrangian approach. This model includes interaction between gas and droplets, atomization of a liquid jet, droplet deformation, breakup and collision of droplets, and capture of dust by droplets. A circular Pease-Anthony Venturi scrubber was simulated numerically with this new model. The numerical results were compared with earlier experimental data for pressure drop and collection efficiency, and gave good agreements.

Fisher information due to a phase noisy laser under non-Markovian environment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Abdel-Khalek, S., E-mail: sayedquantum@yahoo.co.uk

2014-12-15

More recently, K. Berrada [Annals of Physics 340 (2014) 60-69] [1] studied the geometric phase of a two-level atom system driven by a phase noise laser under non-Markovian dynamics in terms of different parameters involved in the whole system, and collapse and revival phenomena were found for large class of states. In this paper, using this noise effect, we study the quantum fisher information (QFI) for a two-level atom system driven by a phase noise laser under non-Markovian dynamics. A new quantity, called QFI flow is used to characterize the damping effect and unveil a fundamental connection between non-Markovian behaviormore » and dynamics of system–environment correlations under phase noise laser. It is shown that QFI flow has disappeared suddenly followed by a sudden birth depending on the kind of the environment damping. QFI flow provides an indicator to characterize the dissipative quantum system’s decoherence by analyzing the behavior of the dynamical non-Markovian coefficients.« less

Modeling Solar Wind Flow with the Multi-Scale Fluid-Kinetic Simulation Suite

DOE PAGES

Pogorelov, N.V.; Borovikov, S. N.; Bedford, M. C.; ...

2013-04-01

Multi-Scale Fluid-Kinetic Simulation Suite (MS-FLUKSS) is a package of numerical codes capable of performing adaptive mesh refinement simulations of complex plasma flows in the presence of discontinuities and charge exchange between ions and neutral atoms. The flow of the ionized component is described with the ideal MHD equations, while the transport of atoms is governed either by the Boltzmann equation or multiple Euler gas dynamics equations. We have enhanced the code with additional physical treatments for the transport of turbulence and acceleration of pickup ions in the interplanetary space and at the termination shock. In this article, we present themore » results of our numerical simulation of the solar wind (SW) interaction with the local interstellar medium (LISM) in different time-dependent and stationary formulations. Numerical results are compared with the Ulysses, Voyager, and OMNI observations. Finally, the SW boundary conditions are derived from in-situ spacecraft measurements and remote observations.« less

Effects of Mg pre-flow, memory, and diffusion on the growth of p-GaN with MOCVD (Conference Presentation)

NASA Astrophysics Data System (ADS)

Tu, Charng-Gan; Chen, Hao-Tsung; Chen, Sheng-Hung; Chao, Chen-Yao; Kiang, Yean-Woei; Yang, Chih-Chung

2017-02-01

In MOCVD growth, two key factors for growing a p-type structure, when the modulation growth or delta-doping technique is used, include Mg memory and diffusion. With high-temperature growth (>900 degree C), doped Mg can diffuse into the under-layer. Also, due to the high-pressure growth and growth chamber coating in MOCVD, plenty Mg atoms exist in the growth chamber for a duration after Mg supply is ended. In this situation, Mg doping continues in the following designated un-doped layers. In this paper, we demonstrate the study results of Mg preflow, memory, and diffusion. The results show that pre-flow of Mg into the growth chamber can lead to a significantly higher Mg doping concentration in growing a p-GaN layer. In other words, a duration for Mg buildup is required for high Mg incorporation. Based on SIMS study, we find that with the pre-flow growth, a high- and a low-doping p-GaN layer are formed. The doping concentration difference between the two layers is about 10 times. The thickness of the high- (low-) doping layer is about 40 (65) nm. The growth of the high-doping layer starts 10-15 min after Mg supply starts (Mg buildup time). The diffusion length of Mg into the AlGaN layer beneath (Mg content reduced to <5%) is about 10 nm. The memory time of Mg in the growth chamber is about 60 min, after which the Mg doping concentration is reduced to <1%.

Low to high confinement transition theory of finite-beta drift-wave driven shear flow and its comparison with data from DIII-D

NASA Astrophysics Data System (ADS)

Guzdar, P. N.; Kleva, R. G.; Groebner, R. J.; Gohil, P.

2004-03-01

Shear flow stabilization of edge turbulence in tokamaks has been the accepted paradigm for the improvement in confinement observed in high (H) confinement mode plasmas. Results on the generation of zonal flow and fields in finite β plasmas are presented. This theory yields a criterion for bifurcation from low to high (L-H) confinement mode, proportional to Te/√Ln , where Te is the electron temperature and Ln is the density scale-length at the steepest part of the density gradient. When this parameter exceeds a critical value (mostly determined by the strength of the toroidal magnetic field), the transition occurs. The predicted threshold based on this parameter shows good agreement with edge measurements on discharges undergoing L-H transitions in DIII-D [J. L. Luxon, R. Anderson, F. Batty et al., in Proceedings of the 11th Conference on Plasma Physics and Controlled Fusion Research, 1986 (International Atomic Energy Agency, Vienna, 1987), Vol. I, p. 159]. The observed differences in the transitions with the reversal of the toroidal magnetic field are reconciled in terms of this critical parameter due to the differences in the density gradient scale-lengths in the edge. The theory also provides a possible explanation for lowered threshold power, pellet injection H modes in DIII-D, thereby providing a unified picture of the varied observations on the L-H transition.

Comparison of direct and flow integration based charge density population analyses.

PubMed

Francisco, E; Martín Pendas, A; Blanco, M A; Costales, A

2007-12-06

Different exhaustive and fuzzy partitions of the molecular electron density (rho) into atomic densities (rho(A)) are used to compute the atomic charges (Q(A)) of a representative set of molecules. The Q(A)'s derived from a direct integration of rho(A) are compared to those obtained from integrating the deformation density rho(def) = rho - rho(0) within each atomic domain. Our analysis shows that the latter methods tend to give Q(A)'s similar to those of the (arbitrary) reference atomic densities rho(A)(0) used in the definition of the promolecular density, rho(0) = SigmaArho(A)(0). Moreover, we show that the basis set independence of these charges is a sign not of their intrinsic quality, as commonly stated, but of the practical insensitivity on the basis set of the atomic domains that are employed in this type of methods.

Synchrotron X-Ray Interrogation of Turbulent Gas–Liquid Mixing in Cryogenic Rocket Sprays

DOE PAGES

Radke, Christopher D.; McManamen, J. Patrick; Kastengren, Alan L.; ...

2017-07-31

The atomization and vaporization of liquid jets within turbulent gaseous flows are characterized by the mixing phenomena occurring over a wide range of spatiotemporal scales. This creates a complex, turbid medium that is not easily interrogated using conventional optical-measurement techniques. In the current study, the optically dense, multiphase flow created by a cryogenic liquid jet injected into a turbulent gaseous coflow is probed using high-speed (MHz) X-ray radiography from a focused, narrowband synchrotron source to resolve the internal cascade of scales and the evolution to isotropic, homogeneous turbulence. Changes in the spectral characteristics for different flow conditions are furthermore correlatedmore » with changes in the spatial distributions of the liquid and gas phases within the spray using simultaneous X-ray radiography and tracer (krypton) fluorescence. It is found that an increase in entrainment and mixing infers an evolution in spectral characteristics toward the well-known -5/3 law of energy dissipation in the context of the classical Kolmogorov theory. Finally, these data demonstrate the utility of the synchrotron-based X-ray radiography and fluorescence for uncovering the internal, turbulent mixing processes in multiphase and optically dense flows.« less

Study of spectral characteristics of radiation from a thermal wake of a pulsating optical discharge in a supersonic air flow

DOE Office of Scientific and Technical Information (OSTI.GOV)

Malov, A N; Orishich, A M; Terent'eva, Ya S

The spectral characteristics of the thermal wake of a pulsating optical discharge (POD) in a supersonic air flow are studied. The POD is stimulated by radiation of a mechanically Q-switched, repetitively pulsed CO{sub 2} laser with a pulse repetition rate of 7 – 150 kHz and a power up to 4.5 kW. The flow is produced by means of the supersonic aerodynamic MAU-M setup having a conic nozzle with a critical cross-section size of 50 mm, the Mach number being 1.3 – 1.6. We describe in detail the system of optical diagnostics that allows the detection of the spectrum ofmore » the weak thermal wake glow against the background of high-power POD radiation. The glow of the thermal wake is due to the emission of light by atoms and ions of nitrogen and oxygen, carried by the flow in the form of hot low-density gas clouds (caverns). The wavelengths of the thermal wake emission and the data on the transitions, corresponding to the spectral lines are presented. (laser applications and other topics in quantum electronics)« less

Synchrotron X-Ray Interrogation of Turbulent Gas–Liquid Mixing in Cryogenic Rocket Sprays

DOE Office of Scientific and Technical Information (OSTI.GOV)

Radke, Christopher D.; McManamen, J. Patrick; Kastengren, Alan L.

The atomization and vaporization of liquid jets within turbulent gaseous flows are characterized by the mixing phenomena occurring over a wide range of spatiotemporal scales. This creates a complex, turbid medium that is not easily interrogated using conventional optical-measurement techniques. In the current study, the optically dense, multiphase flow created by a cryogenic liquid jet injected into a turbulent gaseous coflow is probed using high-speed (MHz) X-ray radiography from a focused, narrowband synchrotron source to resolve the internal cascade of scales and the evolution to isotropic, homogeneous turbulence. Changes in the spectral characteristics for different flow conditions are furthermore correlatedmore » with changes in the spatial distributions of the liquid and gas phases within the spray using simultaneous X-ray radiography and tracer (krypton) fluorescence. It is found that an increase in entrainment and mixing infers an evolution in spectral characteristics toward the well-known -5/3 law of energy dissipation in the context of the classical Kolmogorov theory. Finally, these data demonstrate the utility of the synchrotron-based X-ray radiography and fluorescence for uncovering the internal, turbulent mixing processes in multiphase and optically dense flows.« less

Slip length measurement of gas flow.

PubMed

Maali, Abdelhamid; Colin, Stéphane; Bhushan, Bharat

2016-09-16

In this paper, we present a review of the most important techniques used to measure the slip length of gas flow on isothermal surfaces. First, we present the famous Millikan experiment and then the rotating cylinder and spinning rotor gauge methods. Then, we describe the gas flow rate experiment, which is the most widely used technique to probe a confined gas and measure the slip. Finally, we present a promising technique using an atomic force microscope introduced recently to study the behavior of nanoscale confined gas.

Roles of additives and surface control in slurry atomization

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tsai, S.C.

1990-03-01

This quartery report describes a quantitative correlation between the flow behavior index of a micronized coal slurry and the interparticular van der Waals attraction force a measured by the Hamaker constant. Preliminary results on the effects of interparticular electrostatic repulsion and the liquid viscosity on both the flow behavior and the relative viscosity are also presented. 4 refs., 2 figs., 1 tab.

Roles of additives and surface control in slurry atomization. Quarterly report, April 5, 1990

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tsai, S.C.

1990-03-01

This quarterly report describes a quantitative correlation between the flow behavior index of a micronized coal slurry and the interparticular van der Waals attraction force as measured by the Hamaker constant. Preliminary results on the effects of interparticular electrostatic repulsion and the liquid viscosity on both the flow behavior and the relative viscosity are also presented.

Heat Transfer to Surfaces of Finite Catalytic Activity in Frozen Dissociated Hypersonic Flow

NASA Technical Reports Server (NTRS)

Chung, Paul M.; Anderson, Aemer D.

1961-01-01

The heat transfer due to catalytic recombination of a partially dissociated diatomic gas along the surfaces of two-dimensional and axisymmetric bodies with finite catalytic efficiencies is studied analytically. An integral method is employed resulting in simple yet relatively complete solutions for the particular configurations considered. A closed form solution is derived which enables one to calculate atom mass-fraction distribution, therefore catalytic heat transfer distribution, along the surface of a flat plate in frozen compressible flow with and without transpiration. Numerical calculations are made to determine the atom mass-fraction distribution along an axisymmetric conical body with spherical nose in frozen hypersonic compressible flow. A simple solution based on a local similarity concept is found to be in good agreement with these numerical calculations. The conditions are given for which the local similarity solution is expected to be satisfactory. The limitations on the practical application of the analysis to the flight of the blunt bodies in the atmosphere are discussed. The use of boundary-layer theory and the assumption of frozen flow restrict application of the analysis to altitudes between about 150,000 and 250,000 feet.

Determination of mercury by multisyringe flow injection system with cold-vapor atomic absorption spectrometry.

PubMed

Leal, L O; Elsholz, O; Forteza, R; Cerdà, V

2006-07-28

A new software-controlled time-based multisyringe flow injection system for mercury determination by cold-vapor atomic absorption spectrometry is proposed. Precise known volumes of sample, reducing agent (1.1% SnCl2 in 3% HCl) and carrier (3% HCl) are dispensed into a gas-liquid separation cell with a multisyringe burette coupled with one three-way solenoid valve. An argon flow delivers the reduced mercury to the spectrometer. The optimization of the system was carried out testing reaction coils and gas-liquid separators of different design as well as changing parameters, such as sample and reagents volumes, reagent concentrations and carrier gas flow rate, among others. The analytical curves were obtained within the range 50-5000 ng L(-1). The detection limit (3sigma(b)/S) achieved is 5 ng L(-1). The relative standard deviation (R.S.D.) was 1.4%, evaluated from 16 successive injections of 250 ng L(-1) Hg standard solution. The injection and sample throughput per hour were 44 and 11, respectively. This technique was validated by means of solid and water reference materials with good agreement with the certified values and was successfully applied to fish samples.

On the coupling of hydride generation with atmospheric pressure glow discharge in contact with the flowing liquid cathode for the determination of arsenic, antimony and selenium with optical emission spectrometry.

PubMed

Greda, Krzysztof; Jamroz, Piotr; Jedryczko, Dominika; Pohl, Pawel

2015-05-01

The miniaturized atmospheric pressure glow discharge (APGD) sustained between a liquid flowing cathode and a He nozzle jet anode was combined with hydride generation (HG) to improve the performance of the determination of As, Sb and Se with optical emission spectrometry (OES). As(III), Sb(III) and Se(IV) species were converted into volatile hydrides in the reaction with NaBH4 and right after that they were delivered to the near-anode region of APGD through the nozzle. The transport efficiency of As, Sb and Se to the discharge was several times higher, while intensities of atomic emission lines of As, Sb and Se were improved 3 orders of magnitude (as compared to intensities acquired for the near-cathode region in a APGD system with a typical introduction of analytes through sputtering of the flowing liquid cathode). The effect of the concentration of NaBH4 and HCl in a sample solution, the discharge current, the flow rate of He carrier/jet-supporting and He shielding gases on the emission yield coming from As, Sb, Se, He and H atomic lines and OH and N2 band heads as well as the electron number density was thoroughly studied. Under compromised conditions, limits of detection (3σ criterion) of As, Sb and Se were respectively 4.2, 1.2 and 3.1 µg L(-1). Usefulness of the method was confirmed by the analysis of Sniadecki and Marchlewski highly mineralized spring waters (Kudowa Zdroj, Poland) on the content of As, Sb and Se. Recoveries of elements added to these spring waters were within 90.3-103.7% proving good accuracy of the HG-APGD-OES method. Copyright © 2015 Elsevier B.V. All rights reserved.

In situ S-K XANES study of polymer electrolyte fuel cells: changes in the chemical states of sulfonic groups depending on humidity.

PubMed

Isegawa, Kazuhisa; Nagami, Tetsuo; Jomori, Shinji; Yoshida, Masaaki; Kondoh, Hiroshi

2016-09-14

Changes in the chemical states of sulfonic groups of Nafion in polymer electrolyte fuel cells (PEFCs) under gas-flowing conditions were studied using in situ S-K XANES spectroscopy. The applied potential to the electrodes and the humidity of the cell were changed under flowing H 2 gas in the anode and He gas in the cathode. While the potential shows no significant effect on the S-K XANES spectra, the humidity is found to induce reversible changes in the spectra. Comparison of the spectral changes with simulations based on the density functional theory calculations indicates that the humidity influences the chemical state of the sulfonic group; under wet conditions the sulfonic group is in the form of a sulfonate ion. By drying treatment the sulfonate ion binds to hydrogen and becomes sulfonic acid. Furthermore, a small fraction of the sulfonic acid irreversibly decomposes to atomic sulfur. The peak energy of the atomic sulfur suggests that the generated atomic sulfur is adsorbed on the Pt catalyst surfaces.

Electrical current flow at conductive nanowires formed in GaN thin films by a dislocation template technique

NASA Astrophysics Data System (ADS)

Amma, Shin-ichi; Tokumoto, Yuki; Edagawa, Keiichi; Shibata, Naoya; Mizoguchi, Teruyasu; Yamamoto, Takahisa; Ikuhara, Yuichi

2010-05-01

Conductive nanowires were fabricated in GaN thin film by selectively doping of Al along threading dislocations. Electrical current flow localized at the nanowires was directly measured by a contact mode atomic force microscope. The current flow at the nanowires was considered to be Frenkel-Poole emission mode, suggesting the existence of the deep acceptor level along the nanowires as a possible cause of the current flow. The results obtained in this study show the possibility for fabricating nanowires using pipe-diffusion at dislocations in solid thin films.

Numerical Prediction of the Influence of Process Parameters on Large Area Diamond Deposition by DC Arcjet with ARC Roots Rotating and Operating at Gas Recycling Mode

NASA Astrophysics Data System (ADS)

Lu, F. X.; Huang, T. B.; Tang, W. Z.; Song, J. H.; Tong, Y. M.

A computer model have been set up for simulation of the flow and temperature field, and the radial distribution of atomic hydrogen and active carbonaceous species over a large area substrate surface for a new type dc arc plasma torch with rotating arc roots and operating at gas recycling mode A gas recycling radio of 90% was assumed. In numerical calculation of plasma chemistry, the Thermal-Calc program and a powerful thermodynamic database were employed. Numerical calculations to the computer model were performed using boundary conditions close to the experimental setup for large area diamond films deposition. The results showed that the flow and temperature field over substrate surface of Φ60-100mm were smooth and uniform. Calculations were also made with plasma of the same geometry but no arc roots rotation. It was clearly demonstrated that the design of rotating arc roots was advantageous for high quality uniform deposition of large area diamond films. Theoretical predictions on growth rate and film quality as well as their radial uniformity, and the influence of process parameters on large area diamond deposition were discussed in detail based on the spatial distribution of atomic hydrogen and the carbonaceous species in the plasma over the substrate surface obtained from thermodynamic calculations of plasma chemistry, and were compared with experimental observations.

Massive radius-dependent flow slippage in carbon nanotubes

PubMed Central

Secchi, Eleonora; Marbach, Sophie; Niguès, Antoine; Stein, Derek; Siria, Alessandro; Bocquet, Lydéric

2016-01-01

Simulations and measurements have established that water moves through carbon nanotubes with exceptionally high rates due to nearly frictionless interfaces1–4. These observations have stimulated interest in nanotube-based membranes for applications that range from desalination to nano-filtration and energy harvesting5–10, yet the exact water transport mechanisms inside the nanotubes and at the water-carbon interface continue to be controversially discussed11,12 because existing theories fail to provide a satisfying explanation for the limited number of experimental results available to date13. This is because even though controlled and systematic studies have explored transport through individual nanotubes8,9,14–7, none has met the considerable technical challenge of unambiguously measuring the permeability of a single nanotube11. Here we show that the pressure-driven flow rate across individual nanotubes can be determined with unprecedented sensitivity and without dyes from the hydrodynamics of water jets as they emerge from single nanotubes into a surrounding fluid. Our measurements reveal unexpectedly large and radius-dependent surface slippage in carbon nanotubes (CNT), and no slippage in boron-nitride nanotubes (BNNT) that are crystallographically similar to CNTs but differ electronically. This pronounced contrast between the two systems must originate from subtle differences in atomic-scale details of their solid-liquid interfaces, strikingly illustrating that nanofluidics is the frontier where the continuum picture of fluid mechanics confronts the atomic nature of matter. PMID:27604947

Photochemical Ignition Studies. I. Laser Ignition of Flowing Premixed Gases

DTIC Science & Technology

1985-02-01

Combustion," Army Science Conference, West Point, 1984. 1 ? -A.W. Miziolek, R.C. Sausa, and A.J. Alfano , "Efficient Detection of Carbon Atoms Produced...Science Conference, West Point, 1984. 12. A.W. Miziolek, R.C. Sausa, and A.J. Alfano , "Efficient Detection of Carbon Atoms Produced by Argon...61801 Johns Hopkins University/APL Chemical Propulsion Information Agency ATTN: T.W. Christian Johns Hopkins Road Laurel, MD 20707

Atomic-Scale Control of Electron Transport through Single Molecules

NASA Astrophysics Data System (ADS)

Wang, Y. F.; Kröger, J.; Berndt, R.; Vázquez, H.; Brandbyge, M.; Paulsson, M.

2010-04-01

Tin-phthalocyanine molecules adsorbed on Ag(111) were contacted with the tip of a cryogenic scanning tunneling microscope. Orders-of-magnitude variations of the single-molecule junction conductance were achieved by controllably dehydrogenating the molecule and by modifying the atomic structure of the surface electrode. Nonequilibrium Green’s function calculations reproduce the trend of the conductance and visualize the current flow through the junction, which is guided through molecule-electrode chemical bonds.

Mass analyzer ``MASHA'' high temperature target and plasma ion source

NASA Astrophysics Data System (ADS)

Semchenkov, A. G.; Rassadov, D. N.; Bekhterev, V. V.; Bystrov, V. A.; Chizov, A. Yu.; Dmitriev, S. N.; Efremov, A. A.; Guljaev, A. V.; Kozulin, E. M.; Oganessian, Yu. Ts.; Starodub, G. Ya.; Voskresensky, V. M.; Bogomolov, S. L.; Paschenko, S. V.; Zelenak, A.; Tikhonov, V. I.

2004-05-01

A new separator and mass analyzer of super heavy atoms (MASHA) has been created at the FLNR JINR Dubna to separate and measure masses of nuclei and molecules with precision better than 10-3. First experiments with the FEBIAD plasma ion source have been done and give an efficiency of ionization of up to 20% for Kr with a low flow test leak (6 particle μA). We suppose a magnetic field optimization, using the additional electrode (einzel lens type) in the extracting system, and an improving of the vacuum conditions in order to increase the ion source efficiency.

Image fusion based on Bandelet and sparse representation

NASA Astrophysics Data System (ADS)

Zhang, Jiuxing; Zhang, Wei; Li, Xuzhi

2018-04-01

Bandelet transform could acquire geometric regular direction and geometric flow, sparse representation could represent signals with as little as possible atoms on over-complete dictionary, both of which could be used to image fusion. Therefore, a new fusion method is proposed based on Bandelet and Sparse Representation, to fuse Bandelet coefficients of multi-source images and obtain high quality fusion effects. The test are performed on remote sensing images and simulated multi-focus images, experimental results show that the performance of new method is better than tested methods according to objective evaluation indexes and subjective visual effects.

Horizon in Random Matrix Theory, the Hawking Radiation, and Flow of Cold Atoms

DOE Office of Scientific and Technical Information (OSTI.GOV)

Franchini, Fabio; Kravtsov, Vladimir E.

2009-10-16

We propose a Gaussian scalar field theory in a curved 2D metric with an event horizon as the low-energy effective theory for a weakly confined, invariant random matrix ensemble (RME). The presence of an event horizon naturally generates a bath of Hawking radiation, which introduces a finite temperature in the model in a nontrivial way. A similar mapping with a gravitational analogue model has been constructed for a Bose-Einstein condensate (BEC) pushed to flow at a velocity higher than its speed of sound, with Hawking radiation as sound waves propagating over the cold atoms. Our work suggests a threefold connectionmore » between a moving BEC system, black-hole physics and unconventional RMEs with possible experimental applications.« less

Determination of total mercury in environmental and biological samples by flow injection cold vapour atomic absorption spectrometry

NASA Astrophysics Data System (ADS)

Murphy, James; Jones, Phil; Hill, Steve J.

1996-12-01

A simple and accurate method has been developed for the determination of total mercury in environmental and biological samples. The method utilises an off-line microwave digestion stage followed by analysis using a flow injection system with detection by cold vapour atomic absorption spectrometry. The method has been validated using two certified reference materials (DORM-1 dogfish and MESS-2 estuarine sediment) and the results agreed well with the certified values. A detection limit of 0.2 ng g -1 Hg was obtained and no significant interference was observed. The method was finally applied to the determination of mercury in river sediments and canned tuna fish, and gave results in the range 0.1-3.0 mg kg -1.

Applications of Quantum Theory of Atomic and Molecular Scattering to Problems in Hypersonic Flow

NASA Technical Reports Server (NTRS)

Malik, F. Bary

1995-01-01

The general status of a grant to investigate the applications of quantum theory in atomic and molecular scattering problems in hypersonic flow is summarized. Abstracts of five articles and eleven full-length articles published or submitted for publication are included as attachments. The following topics are addressed in these articles: fragmentation of heavy ions (HZE particles); parameterization of absorption cross sections; light ion transport; emission of light fragments as an indicator of equilibrated populations; quantum mechanical, optical model methods for calculating cross sections for particle fragmentation by hydrogen; evaluation of NUCFRG2, the semi-empirical nuclear fragmentation database; investigation of the single- and double-ionization of He by proton and anti-proton collisions; Bose-Einstein condensation of nuclei; and a liquid drop model in HZE particle fragmentation by hydrogen.

Solution of the comoving-frame equation of transfer in spherically symmetric flows. V - Multilevel atoms. [in early star atmospheres

NASA Technical Reports Server (NTRS)

Mihalas, D.; Kunasz, P. B.

1978-01-01

The coupled radiative transfer and statistical equilibrium equations for multilevel ionic structures in the atmospheres of early-type stars are solved. Both lines and continua are treated consistently; the treatment is applicable throughout a transonic wind, and allows for the presence of background continuum sources and sinks in the transfer. An equivalent-two-level-atoms approach provides the solution for the equations. Calculations for simplified He (+)-like model atoms in parameterized isothermal wind models indicate that subordinate line profiles are sensitive to the assumed mass-loss rate, and to the assumed structure of the velocity law in the atmospheres.

Diode laser-based thermometry using two-line atomic fluorescence of indium and gallium

NASA Astrophysics Data System (ADS)

Borggren, Jesper; Weng, Wubin; Hosseinnia, Ali; Bengtsson, Per-Erik; Aldén, Marcus; Li, Zhongshan

2017-12-01

A robust and relatively compact calibration-free thermometric technique using diode lasers two-line atomic fluorescence (TLAF) for reactive flows at atmospheric pressures is investigated. TLAF temperature measurements were conducted using indium and, for the first time, gallium atoms as temperature markers. The temperature was measured in a multi-jet burner running methane/air flames providing variable temperatures ranging from 1600 to 2000 K. Indium and gallium were found to provide a similar accuracy of 2.7% and precision of 1% over the measured temperature range. The reliability of the TLAF thermometry was further tested by performing simultaneous rotational CARS measurements in the same experiments.

Effects of solvent evaporation conditions on solvent vapor annealed cylinder-forming block polymer thin films

NASA Astrophysics Data System (ADS)

Grant, Meagan; Jakubowski, William; Nelson, Gunnar; Drapes, Chloe; Baruth, A.

Solvent vapor annealing is a less time and energy intensive method compared to thermal annealing, to direct the self-assembly of block polymer thin films. Periodic nanostructures have applications in ultrafiltration, magnetic arrays, or other structures with nanometer dimensions, driving its continued interest. Our goal is to create thin films with hexagonally packed, perpendicular aligned cylinders of poly(lactide) in a poly(styrene) matrix that span the thickness of the film with low anneal times and low defect densities, all with high reproducibility, where the latter is paramount. Through the use of our computer-controlled, pneumatically-actuated, purpose-built solvent vapor annealing chamber, we have the ability to monitor and control vapor pressure, solvent concentration within the film, and solvent evaporation rate with unprecedented precision and reliability. Focusing on evaporation, we report on two previously unexplored areas, chamber pressure during solvent evaporation and the flow rate of purging gas aiding the evaporation. We will report our exhaustive results following atomic force microscopy analysis of films exposed to a wide range of pressures and flow rates. Reliably achieving well-ordered films, while occurring within a large section of this parameter space, was correlated with high-flow evaporation rates and low chamber pressures. These results have significant implications on other methods of solvent annealing, including ``jar'' techniques.

Dual-mode nonlinear instability analysis of a confined planar liquid sheet sandwiched between two gas streams of unequal velocities and prediction of droplet size and velocity distribution using maximum entropy formulation

NASA Astrophysics Data System (ADS)

Dasgupta, Debayan; Nath, Sujit; Bhanja, Dipankar

2018-04-01

Twin fluid atomizers utilize the kinetic energy of high speed gases to disintegrate a liquid sheet into fine uniform droplets. Quite often, the gas streams are injected at unequal velocities to enhance the aerodynamic interaction between the liquid sheet and surrounding atmosphere. In order to improve the mixing characteristics, practical atomizers confine the gas flows within ducts. Though the liquid sheet coming out of an injector is usually annular in shape, it can be considered to be planar as the mean radius of curvature is much larger than the sheet thickness. There are numerous studies on breakup of the planar liquid sheet, but none of them considered the simultaneous effects of confinement and unequal gas velocities on the spray characteristics. The present study performs a nonlinear temporal analysis of instabilities in the planar liquid sheet, produced by two co-flowing gas streams moving with unequal velocities within two solid walls. The results show that the para-sinuous mode dominates the breakup process at all flow conditions over the para-varicose mode of breakup. The sheet pattern is strongly influenced by gas velocities, particularly for the para-varicose mode. Spray characteristics are influenced by both gas velocity and proximity to the confining wall, but the former has a much more pronounced effect on droplet size. An increase in the difference between gas velocities at two interfaces drastically shifts the droplet size distribution toward finer droplets. Moreover, asymmetry in gas phase velocities affects the droplet velocity distribution more, only at low liquid Weber numbers for the input conditions chosen in the present study.

Liquid chromatography mass spectrometry determination of perfluoroalkyl acids in environmental solid extracts after phospholipid removal and on-line turbulent flow chromatography purification.

PubMed

Mazzoni, M; Polesello, S; Rusconi, M; Valsecchi, S

2016-07-01

An on-line TFC (Turbulent Flow Chromatography) clean up procedures coupled with UHPLC-MS/MS (Ultra High Performance Liquid Chromatography Mass Spectrometry) multi-residue method was developed for the simultaneous determination of 8 perfluroalkyl carboxylic acids (PFCA, from 5 to 12 carbon atoms) and 3 perfluoroalkyl sulfonic acids (PFSA, from 4 to 8 carbon atoms) in environmental solid matrices. Fast sample preparation procedure was based on a sonication-assisted extraction with acetonitrile. Phospholipids in biological samples were fully removed by an off-line SPE purification before injection, using HybridSPE(®) Phospholipid Ultra cartridges. The development of the on-line TFC clean-up procedure regarded the choice of the stationary phase, the optimization of the mobile phase composition, flow rate and injected volume. The validation of the optimized method included the evaluation of matrix effects, accuracy and reproducibility. Signal suppression in the analysis of fortified extracts ranged from 1 to 60%, and this problem was overcome by using isotopic dilution. Since no certified reference materials were available for PFAS in these matrices, accuracy was evaluated by recoveries on spiked clam samples which were 98-133% for PFCAs and 40-60% for PFSAs. MLDs and MLQs ranged from 0.03 to 0.3ngg(-1) wet weight and from 0.1 to 0.9ngg(-1) wet weight respectively. Repeatability (intra-day precision) and reproducibility (inter-day precision) showed RSD from 3 to 13% and from 4 to 27% respectively. Validated on-line TFC/UHPLC-MS/MS method has been applied for the determination of perfluoroalkyl acids in different solid matrices (sediment, fish, bivalves and bird yolk). Copyright © 2016 Elsevier B.V. All rights reserved.

Ion thruster performance model

NASA Technical Reports Server (NTRS)

Brophy, J. R.

1984-01-01

A model of ion thruster performance is developed for high flux density, cusped magnetic field thruster designs. This model is formulated in terms of the average energy required to produce an ion in the discharge chamber plasma and the fraction of these ions that are extracted to form the beam. The direct loss of high energy (primary) electrons from the plasma to the anode is shown to have a major effect on thruster performance. The model provides simple algebraic equations enabling one to calculate the beam ion energy cost, the average discharge chamber plasma ion energy cost, the primary electron density, the primary-to-Maxwellian electron density ratio and the Maxwellian electron temperature. Experiments indicate that the model correctly predicts the variation in plasma ion energy cost for changes in propellant gas (Ar, Kr and Xe), grid transparency to neutral atoms, beam extraction area, discharge voltage, and discharge chamber wall temperature. The model and experiments indicate that thruster performance may be described in terms of only four thruster configuration dependent parameters and two operating parameters. The model also suggests that improved performance should be exhibited by thruster designs which extract a large fraction of the ions produced in the discharge chamber, which have good primary electron and neutral atom containment and which operate at high propellant flow rates.

Recent advances at NASA in calculating the electronic spectra of diatomic molecules

NASA Technical Reports Server (NTRS)

Whiting, Ellis E.; Paterson, John A.

1988-01-01

Advanced entry vehicles, such as the proposed Aero-assisted Orbital Transfer Vehicle, provide new and challenging problems for spectroscopy. Large portions of the flow field about such vehicles will be characterized by chemical and thermal nonequilibrium. Only by considering the actual overlap of the atomic and rotational lines emitted by the species present can the impact of radiative transport within the flow field be assessed correctly. To help make such an assessment, a new computer program is described that can generate high-resolution, line-by-line spectra for any spin-allowed transitions in diatomic molecules. The program includes the matrix elements for the rotational energy and distortion to the fourth order; the spin-orbit, spin-spin, and spin-rotation interactions to first order; and the lambda splitting by a perturbation calculation. An overview of the Computational Chemistry Branch at Ames Research Center is also presented.

Determination of hexabromocyclododecane by flowing atmospheric pressure afterglow mass spectrometry.

PubMed

Smoluch, Marek; Silberring, Jerzy; Reszke, Edward; Kuc, Joanna; Grochowalski, Adam

2014-10-01

The first application of a flowing atmospheric-pressure afterglow ion source for mass spectrometry (FAPA-MS) for the chemical characterization and determination of hexabromocyclododecane (HBCD) is presented. The samples of technical HBCD and expanded polystyrene foam (EPS) containing HBCD as a flame retardant were prepared by dissolving the appropriate solids in dichloromethane. The ionization of HBCD was achieved with a prototype FAPA source. The ions were detected in the negative-ion mode. The ions corresponding to a deprotonated HBCD species (m/z 640.7) as well as chlorine (m/z 676.8), nitrite (m/z 687.8) and nitric (m/z 703.8) adducts were observed in the spectra. The observed isotope pattern is characteristic for a compound containing six bromine atoms. This technique is an effective approach to detect HBCD, which is efficiently ionized in a liquid phase, resulting in high detection efficiency and sensitivity. Copyright © 2014 Elsevier B.V. All rights reserved.

Optimization of Simplex Atomizer Inlet Port Configuration through Computational Fluid Dynamics and Experimental Study for Aero-Gas Turbine Applications

NASA Astrophysics Data System (ADS)

Marudhappan, Raja; Chandrasekhar, Udayagiri; Hemachandra Reddy, Koni

2017-10-01

The design of plain orifice simplex atomizer for use in the annular combustion system of 1100 kW turbo shaft engine is optimized. The discrete flow field of jet fuel inside the swirl chamber of the atomizer and up to 1.0 mm downstream of the atomizer exit are simulated using commercial Computational Fluid Dynamics (CFD) software. The Euler-Euler multiphase model is used to solve two sets of momentum equations for liquid and gaseous phases and the volume fraction of each phase is tracked throughout the computational domain. The atomizer design is optimized after performing several 2D axis symmetric analyses with swirl and the optimized inlet port design parameters are used for 3D simulation. The Volume Of Fluid (VOF) multiphase model is used in the simulation. The orifice exit diameter is 0.6 mm. The atomizer is fabricated with the optimized geometric parameters. The performance of the atomizer is tested in the laboratory. The experimental observations are compared with the results obtained from 2D and 3D CFD simulations. The simulated velocity components, pressure field, streamlines and air core dynamics along the atomizer axis are compared to previous research works and found satisfactory. The work has led to a novel approach in the design of pressure swirl atomizer.

Cold Flow Testing for Liquid Propellant Rocket Injector Scaling and Throttling

NASA Technical Reports Server (NTRS)

Kenny, Jeremy R.; Moser, Marlow D.; Hulka, James; Jones, Gregg

2006-01-01

Scaling and throttling of combustion devices are important capabilities to demonstrate in development of liquid rocket engines for NASA's Space Exploration Mission. Scaling provides the ability to design new injectors and injection elements with predictable performance on the basis of test experience with existing injectors and elements, and could be a key aspect of future development programs. Throttling is the reduction of thrust with fixed designs and is a critical requirement in lunar and other planetary landing missions. A task in the Constellation University Institutes Program (CUIP) has been designed to evaluate spray characteristics when liquid propellant rocket engine injectors are scaled and throttled. The specific objectives of the present study are to characterize injection and primary atomization using cold flow simulations of the reacting sprays. These simulations can provide relevant information because the injection and primary atomization are believed to be the spray processes least affected by the propellant reaction. Cold flow studies also provide acceptable test conditions for a university environment. Three geometric scales - 1/4- scale, 1/2-scale, and full-scale - of two different injector element types - swirl coaxial and shear coaxial - will be designed, fabricated, and tested. A literature review is currently being conducted to revisit and compile the previous scaling documentation. Because it is simple to perform, throttling will also be examined in the present work by measuring primary atomization characteristics as the mass flow rate and pressure drop of the six injector element concepts are reduced, with corresponding changes in chamber backpressure. Simulants will include water and gaseous nitrogen, and an optically accessible chamber will be used for visual and laser-based diagnostics. The chamber will include curtain flow capability to repress recirculation, and additional gas injection to provide independent control of the backpressure. This paper provides a short review of the appropriate literature, as well as descriptions of plans for experimental hardware, test chamber instrumentation, diagnostics, and testing.

Asymmetrical flow field-flow fractionation with multi-angle light scattering and quasi-elastic light scattering for characterization of polymersomes: comparison with classical techniques.

PubMed

Till, Ugo; Gaucher-Delmas, Mireille; Saint-Aguet, Pascale; Hamon, Glenn; Marty, Jean-Daniel; Chassenieux, Christophe; Payré, Bruno; Goudounèche, Dominique; Mingotaud, Anne-Françoise; Violleau, Frédéric

2014-12-01

Polymersomes formed from amphiphilic block copolymers, such as poly(ethyleneoxide-b-ε-caprolactone) (PEO-b-PCL) or poly(ethyleneoxide-b-methylmethacrylate), were characterized by asymmetrical flow field-flow fractionation coupled with quasi-elastic light scattering (QELS), multi-angle light scattering (MALS), and refractive index detection, leading to the determination of their size, shape, and molecular weight. The method was cross-examined with more classical ones, like batch dynamic and static light scattering, electron microscopy, and atomic force microscopy. The results show good complementarities between all the techniques; asymmetrical flow field-flow fractionation being the most pertinent one when the sample exhibits several different types of population.

Synthesis and Mechanical Characterization of Binary and Ternary Intermetallic Alloys Based on Fe-Ti-Al by Resonant Ultrasound Vibrational Methods.

PubMed

Chanbi, Daoud; Ogam, Erick; Amara, Sif Eddine; Fellah, Z E A

2018-05-07

Precise but simple experimental and inverse methods allowing the recovery of mechanical material parameters are necessary for the exploration of materials with novel crystallographic structures and elastic properties, particularly for new materials and those existing only in theory. The alloys studied herein are of new atomic compositions. This paper reports an experimental study involving the synthesis and development of methods for the determination of the elastic properties of binary (Fe-Al, Fe-Ti and Ti-Al) and ternary (Fe-Ti-Al) intermetallic alloys with different concentrations of their individual constituents. The alloys studied were synthesized from high purity metals using an arc furnace with argon flow to ensure their uniformity and homogeneity. Precise but simple methods for the recovery of the elastic constants of the isotropic metals from resonant ultrasound vibration data were developed. These methods allowed the fine analysis of the relationships between the atomic concentration of a given constituent and the Young’s modulus or alloy density.

Atmospheric pressure spatial atomic layer deposition web coating with in situ monitoring of film thickness

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yersak, Alexander S.; Lee, Yung C.; Spencer, Joseph A.

Spectral reflectometry was implemented as a method for in situ thickness monitoring in a spatial atomic layer deposition (ALD) system. Al{sub 2}O{sub 3} films were grown on a moving polymer web substrate at 100 °C using an atmospheric pressure ALD web coating system, with film growth of 0.11–0.13 nm/cycle. The modular coating head design and the in situ monitoring allowed for the characterization and optimization of the trimethylaluminum and water precursor exposures, purge flows, and web speed. A thickness uniformity of ±2% was achieved across the web. ALD cycle times as low as 76 ms were demonstrated with a web speed of 1 m/smore » and a vertical gap height of 0.5 mm. This atmospheric pressure ALD system with in situ process control demonstrates the feasibility of low-cost, high throughput roll-to-roll ALD.« less

Demonstration of asymmetric electron conduction in pseudosymmetrical photosynthetic reaction centre proteins in an electrical circuit

PubMed Central

Kamran, Muhammad; Friebe, Vincent M.; Delgado, Juan D.; Aartsma, Thijs J.; Frese, Raoul N.; Jones, Michael R.

2015-01-01

Photosynthetic reaction centres show promise for biomolecular electronics as nanoscale solar-powered batteries and molecular diodes that are amenable to atomic-level re-engineering. In this work the mechanism of electron conduction across the highly tractable Rhodobacter sphaeroides reaction centre is characterized by conductive atomic force microscopy. We find, using engineered proteins of known structure, that only one of the two cofactor wires connecting the positive and negative termini of this reaction centre is capable of conducting unidirectional current under a suitably oriented bias, irrespective of the magnitude of the bias or the applied force at the tunnelling junction. This behaviour, strong functional asymmetry in a largely symmetrical protein–cofactor matrix, recapitulates the strong functional asymmetry characteristic of natural photochemical charge separation, but it is surprising given that the stimulus for electron flow is simply an externally applied bias. Reasons for the electrical resistance displayed by the so-called B-wire of cofactors are explored. PMID:25751412

Demonstration of asymmetric electron conduction in pseudosymmetrical photosynthetic reaction centre proteins in an electrical circuit.

PubMed

Kamran, Muhammad; Friebe, Vincent M; Delgado, Juan D; Aartsma, Thijs J; Frese, Raoul N; Jones, Michael R

2015-03-09

Photosynthetic reaction centres show promise for biomolecular electronics as nanoscale solar-powered batteries and molecular diodes that are amenable to atomic-level re-engineering. In this work the mechanism of electron conduction across the highly tractable Rhodobacter sphaeroides reaction centre is characterized by conductive atomic force microscopy. We find, using engineered proteins of known structure, that only one of the two cofactor wires connecting the positive and negative termini of this reaction centre is capable of conducting unidirectional current under a suitably oriented bias, irrespective of the magnitude of the bias or the applied force at the tunnelling junction. This behaviour, strong functional asymmetry in a largely symmetrical protein-cofactor matrix, recapitulates the strong functional asymmetry characteristic of natural photochemical charge separation, but it is surprising given that the stimulus for electron flow is simply an externally applied bias. Reasons for the electrical resistance displayed by the so-called B-wire of cofactors are explored.

Synthesis and Mechanical Characterization of Binary and Ternary Intermetallic Alloys Based on Fe-Ti-Al by Resonant Ultrasound Vibrational Methods

PubMed Central

Chanbi, Daoud; Amara, Sif Eddine; Fellah, Z. E. A.

2018-01-01

Precise but simple experimental and inverse methods allowing the recovery of mechanical material parameters are necessary for the exploration of materials with novel crystallographic structures and elastic properties, particularly for new materials and those existing only in theory. The alloys studied herein are of new atomic compositions. This paper reports an experimental study involving the synthesis and development of methods for the determination of the elastic properties of binary (Fe-Al, Fe-Ti and Ti-Al) and ternary (Fe-Ti-Al) intermetallic alloys with different concentrations of their individual constituents. The alloys studied were synthesized from high purity metals using an arc furnace with argon flow to ensure their uniformity and homogeneity. Precise but simple methods for the recovery of the elastic constants of the isotropic metals from resonant ultrasound vibration data were developed. These methods allowed the fine analysis of the relationships between the atomic concentration of a given constituent and the Young’s modulus or alloy density. PMID:29735946

Glassy carbon/multi walled carbon nanotube/cadmium sulphide photoanode for light energy storage in vanadium photoelectrochemical cell

NASA Astrophysics Data System (ADS)

Peimanifard, Zahra; Rashid-Nadimi, Sahar

2015-12-01

The aim of this study is utilizing the artificial photosynthesis, which is an attractive and challenging theme in the photoelectrocatalytic water splitting, to charge the vanadium redox flow battery (VRFB). In this work multi walled carbon nanotube/cadmium sulphide hybrid is employed as a photoanode material to oxidize VO2+ toVO2+ for charging the positive vanadium redox flow battery's half-cell. Characterization studies are also described using the scanning electron microscopic-energy-dispersive X-ray spectroscopy (SEM-EDS), inductively coupled plasma atomic emission spectroscopy (ICP-AES) and UV-Visible methods. The phtoelectrochemical performance is characterized by cyclic voltammetry and chronoamperometry. Applied bias photon-to-current efficiency (ABPE) is achieved for both two and three-electrode configurations. The glassy carbon/multi walled carbon nanotube/cadmium sulphide yields high maximum ABPE of 2.6% and 2.12% in three and two-electrode setups, respectively. These results provide a useful guideline in designing photoelectrochemical cells for charging the vanadium redox flow batteries by sunlight as a low cost, free and abundant energy source, which does not rely on an external power input.

Catalytic nanoporous membranes

DOEpatents

Pellin, Michael J; Hryn, John N; Elam, Jeffrey W

2013-08-27

A nanoporous catalytic membrane which displays several unique features Including pores which can go through the entire thickness of the membrane. The membrane has a higher catalytic and product selectivity than conventional catalysts. Anodic aluminum oxide (AAO) membranes serve as the catalyst substrate. This substrate is then subjected to Atomic Layer Deposition (ALD), which allows the controlled narrowing of the pores from 40 nm to 10 nm in the substrate by deposition of a preparatory material. Subsequent deposition of a catalytic layer on the inner surfaces of the pores reduces pore sizes to less than 10 nm and allows for a higher degree of reaction selectivity. The small pore sizes allow control over which molecules enter the pores, and the flow-through feature can allow for partial oxidation of reactant species as opposed to complete oxidation. A nanoporous separation membrane, produced by ALD is also provided for use in gaseous and liquid separations. The membrane has a high flow rate of material with 100% selectivity. Also provided is a method for producing a catalytic membrane having flow-through pores and discreet catalytic clusters adhering to the inside surfaces of the pores.

Flow Structure Comparison for Two 7-Point LDI Configurations

NASA Technical Reports Server (NTRS)

Hicks, Yolanda R.; Tacina, Kathleen M.

2017-01-01

This paper presents a comparison primarily of the 2-D velocity profiles in the non-burning system; and for the luminescent flame structure for a 7-point Lean Direct Injector (LDI). This circular LDI array consists of a center element surrounded by six outer elements spaced 60 degrees apart; the spacing between all adjacent elements is the same. Each element consists of simplex atomizer that injects at the throat of a converging-diverging venturi, and an axial swirler upstream of the venturi throat to generate swirl. The two configurations were: 1) one which consists of all 60 co-swirling axial air swirlers, and; 2) one configuration which uses a 60 swirler in the center, surrounded by counter-swirling 45 swirlers. Testing was done at 5 atm and an inlet temperature of 800F. Two air reference velocities were considered in the cold flow measurements and one common air flow condition for the burning case.The 2D velocity profiles were determined using particle image velocimetry and the flame structure was determined using high speed photography.

Investigation on structural, optical and electrical properties of Cp2Mg flow varied p-GaN grown by MOCVD

NASA Astrophysics Data System (ADS)

Surender, S.; Pradeep, S.; Ramesh, R.; Baskar, K.

2016-05-01

In this work the effect of different concentration of Magnesium doped GaN (p-GaN) were systematically studied. The p-GaN epilayers were grown on c-plane sapphire substrate by horizontal flow Metal Organic Chemical Vapor Deposition (MOCVD) with various flow rates of 100 sccm to 300 sccm using bis-(cyclopentadienyl) - magnesium (Cp2Mg) precursor. The samples were subjected to structural, optical, morphological and electrical studies using High Resolution X-ray diffraction (HRXRD), room temperature photoluminescence (PL), Atomic Force Microscopy (AFM) and Hall measurement respectively. Results indicated that the Mg doped GaN of 200 sccm Cp2Mg has the root mean square (rms) roughness of about 0.3 nm for a scan area of 5×5 µm2 which has good two dimensional growth. Moreover, Hall measurements results shows that (200 sccm Cp2Mg) Mg-doped GaN possess the highest hole concentration of 5.4×1017cm-3 and resistivity of 1.7 Ωcm at room temperature.

Numerical Study of Suspension Plasma Spraying

NASA Astrophysics Data System (ADS)

Farrokhpanah, Amirsaman; Coyle, Thomas W.; Mostaghimi, Javad

2017-01-01

A numerical study of suspension plasma spraying is presented in the current work. The liquid suspension jet is replaced with a train of droplets containing the suspension particles injected into the plasma flow. Atomization, evaporation, and melting of different components are considered for droplets and particles as they travel toward the substrate. Effect of different parameters on particle conditions during flight and upon impact on the substrate is investigated. Initially, influence of the torch operating conditions such as inlet flow rate and power is studied. Additionally, effect of injector parameters like injection location, flow rate, and angle is examined. The model used in the current study takes high-temperature gradients and non-continuum effects into account. Moreover, the important effect of change in physical properties of suspension droplets as a result of evaporation is included in the model. These mainly include variations in heat transfer properties and viscosity. Utilizing this improved model, several test cases have been considered to better evaluate the effect of different parameters on the quality of particles during flight and upon impact on the substrate.

Investigation on structural, optical and electrical properties of Cp2Mg flow varied p-GaN grown by MOCVD

DOE Office of Scientific and Technical Information (OSTI.GOV)

Surender, S.; Pradeep, S.; Ramesh, R.

2016-05-23

In this work the effect of different concentration of Magnesium doped GaN (p-GaN) were systematically studied. The p-GaN epilayers were grown on c-plane sapphire substrate by horizontal flow Metal Organic Chemical Vapor Deposition (MOCVD) with various flow rates of 100 sccm to 300 sccm using bis-(cyclopentadienyl) - magnesium (Cp2Mg) precursor. The samples were subjected to structural, optical, morphological and electrical studies using High Resolution X-ray diffraction (HRXRD), room temperature photoluminescence (PL), Atomic Force Microscopy (AFM) and Hall measurement respectively. Results indicated that the Mg doped GaN of 200 sccm Cp2Mg has the root mean square (rms) roughness of about 0.3more » nm for a scan area of 5×5 µm{sup 2} which has good two dimensional growth. Moreover, Hall measurements results shows that (200 sccm Cp2Mg) Mg-doped GaN possess the highest hole concentration of 5.4×10{sup 17}cm{sup −3} and resistivity of 1.7 Ωcm at room temperature.« less

Theoretical investigation of non-equilibrium chemistry and optical radiation in hypersonic flow fields

NASA Technical Reports Server (NTRS)

Whiting, Ellis E.

1990-01-01

Future space vehicles returning from distant missions or high earth orbits may enter the upper regions of the atmosphere and use aerodynamic drag to reduce their velocity before they skip out of the atmosphere and enter low earth orbit. The Aeroassist Flight Experiment (AFE) is designed to explore the special problems encountered in such entries. A computer code was developed to calculate the radiative transport along line-or-sight in the general 3-D flow field about an arbitrary entry vehicle, if the temperatures and species concentrations along the line-of-sight are known. The radiative heating calculation at the stagnation point of the AFE vehicle along the entry trajectory was performed, including a detailed line-by-line accounting of the radiative transport in the vacuum ultraviolet (below 200 nm) by the atomic N and O lines. A method was developed for making measurements of the haze particles in the Titan atmosphere above 200 km altitude. Several other tasks of a continuing nature, to improve the technical ability to calculate the nonequilibrium gas dynamic flow field and radiative heating of entry vehicles, were completed or advanced.

The route of liquid precursor to ZnO nanoparticles in premixed combustion spray pyrolysis

NASA Astrophysics Data System (ADS)

Widiyastuti, W.; Machmudah, Siti; Nurtono, Tantular; Winardi, Sugeng

2018-04-01

Zinc oxide nanoparticles had been successfully synthesized by premixed combustion spray pyrolysis. Zinc acetate was dissolved in distilled water was selected as a liquid precursor. Zinc nitrate was also used for comparison the effect of precursor type on the generated particles morphology and the crystallinity. The premixed combustion reaction used liquefied petroleum gas (LPG) mainly consisting of butane and propane as a fuel and compressed air used as an oxidizer. The liquid precursor was atomized using a custom two fluid nozzle to generate droplets. Then, the droplets were sprayed by the flow of air as a carrier gas into the premixed combustion reactor. The zinc precursor was decomposed to zinc oxide due to the high temperature as a result of combustion reaction inside the reactor resulting in nanoparticles formation. The particle size decreased with the increase of the fuel flow rate. In addition, it can be found that at the same flow rate of fuel, the particle size of zinc oxide synthesized using zinc nitrate is larger than that of the use of zinc acetate as a precursor.

On relaxation nature of glass transition in amorphous materials

NASA Astrophysics Data System (ADS)

Sanditov, Damba S.; Ojovan, Michael I.

2017-10-01

A short review on relaxation theories of glass transition is presented. The main attention is paid to modern aspects of the glass transition equation qτg = C, suggested by Bartenev in 1951 (q - cooling rate of the melt, τg - structural relaxation time at the glass transition temperature Tg). This equation represents a criterion of structural relaxation at transition from liquid to glass at T = Tg (analogous to the condition of mechanical relaxation ωτ = 1, where the maximum of mechanical loss is observed). The empirical parameter С = δTg has the meaning of temperature range δTg that characterizes the liquid-glass transition. Different approaches of δTg calculation are reviewed. In the framework of the model of delocalized atoms a modified kinetic criterion of glass transition is proposed (q/Tg)τg = Cg, where Cg ≅ 7·10-3 is a practically universal dimensionless constant. It depends on fraction of fluctuation volume fg, which is frozen at the glass transition temperature Cg = fg/ln(1/fg). The value of fg is approximately constant fg ≅ 0.025. At Tg the process of atom delocalization, i.e. its displacement from the equilibrium position, is frozen. In silicate glasses atom delocalization is reduced to critical displacement of bridge oxygen atom in Si-O-Si bridge necessary to switch a valence bond according to Muller and Nemilov. An equation is derived for the temperature dependence of viscosity of glass-forming liquids in the wide temperature range, including the liquid-glass transition and the region of higher temperatures. Notion of (bridge) atom delocalization is developed, which is related to necessity of local low activation deformation of structural network for realization of elementary act of viscous flow - activated switch of a valence (bridge) bond. Without atom delocalization (;trigger mechanism;) a switch of the valence bond is impossible and, consequently, the viscous flow. Thus the freezing of atom delocalization process at low temperatures, around Tg, leads to the cease of the viscous flow and transition of a melt to a glassy state. This occurs when the energy of disordered lattice thermal vibrations averaged to one atom becomes equal or less than the energy of atom delocalization. The Bartenev equation for cooling rate dependence of glass transition temperature Tg = Tg(q) is discussed. The value of fg calculated from the data on the Tg(q) dependence coincides with result of the fg calculation using the data on viscosity near the glass transition. Derivation of the Bartenev equation with the account of temperature dependence of activation energy of glass transition process is considered. The obtained generalized relation describes the Tg(q) dependence in a wider interval of the cooling rate compared Bartenev equation. Experimental data related to standard cooling rate q = 3 K/min were used in this work.

Photo-excitation of electrons in cytochrome c oxidase as a theory of the mechanism of the increase of ATP production in mitochondria by laser therapy

NASA Astrophysics Data System (ADS)

Zielke, Andrzej

2014-02-01

The hypothesis explains the molecular basis for restoring mitochondrial function by laser therapy. It also explains how laser therapy reverses both excessive oxidation (lack of NADH/FADH2) and excessive reduction (lack of O2) states of cytochrome c oxidase complex. It is proposed that photons interact with heme molecules of cytochrome c oxidase. A molecule of heme contains a porphyrin ring and an atom of iron in the center. The iron atom (Fe) can switch oxidation states back and forth between ferrous (Fe2+) and ferric (Fe3+) by accepting or releasing an electron. The porphyrin ring is a complex aromatic molecule that has 26 pi electrons which are "delocalized", spinning in the carbon rings creating a resonating electromagnetic cloud. Photons with similar wavelengths are absorbed by the cloud increasing its energy. The energy is then passed on to the centrally located atom of iron existing in a reduced state (Fe2+). The electrons on the orbits of the iron atom accept this electromagnetic energy, and change orbitals to a higher energetic level. If the energy is sufficient, electrons leave the atom entirely. If this occurs, Fe2+ become oxidized to Fe3+ releasing electrons, thus restoring electron flow and the production of ATP. At the same time, electrons freed from complex IV may have sufficient energy to be picked by NAD+/FADH and re-enter the chain at the complex I or II amplifying the flow of electrons.

Joint Detect and Avoid Flight Testing

NASA Technical Reports Server (NTRS)

Maliska, Heather; Estrada, Ramon; Euteneuer, Eric; Gong, Chester; Arthur, Keith

2015-01-01

This presentation gives insight into a joint flight testing effort that included participation from NASA, Honeywell, and General Atomics. The presentation includes roles and responsibilities, test flow, and encounter requirements and summary.

Iron catalyst chemistry in modeling a high-pressure carbon monoxide nanotube reactor

NASA Technical Reports Server (NTRS)

Scott, Carl D.; Povitsky, Alexander; Dateo, Christopher; Gokcen, Tahir; Willis, Peter A.; Smalley, Richard E.

2003-01-01

The high-pressure carbon monoxide (HiPco) technique for producing single-wall carbon nanotubes (SWNTs) is analyzed with the use of a chemical reaction model coupled with flow properties calculated along streamlines, calculated by the FLUENT code for pure carbon monoxide. Cold iron pentacarbonyl, diluted in CO at about 30 atmospheres, is injected into a conical mixing zone, where hot CO is also introduced via three jets at 30 degrees with respect to the axis. Hot CO decomposes the Fe(CO)5 to release atomic Fe. Then iron nucleates and forms clusters that catalyze the formation of SWNTs by a disproportionation reaction (Boudouard) of CO on Fe-containing clusters. Alternative nucleation rates are estimated from the theory of hard sphere collision dynamics with an activation energy barrier. The rate coefficient for carbon nanotube growth is estimated from activation energies in the literature. The calculated growth was found be about an order of magnitude greater than measured, regardless of the nucleation rate. A study of cluster formation in an incubation zone prior to injection into the reactor shows that direct dimer formation from Fe atoms is not as important as formation via an exchange reaction of Fe with CO in FeCO.

Concept for Inclusion of Analytical and Computational Capability in Optical Plume Anomaly Detection (OPAD) for Measurement of Neutron Flux

NASA Technical Reports Server (NTRS)

Patrick, M. Clinton; Cooper, Anita E.; Powers, W. T.

2004-01-01

Researchers are working on many konts to make possible high speed, automated classification and quantification of constituent materials in numerous environments. NASA's Marshall Space Flight Center has implemented a system for rocket engine flow fields/plumes; the Optical Plume Anomaly Detection (OPAD) system was designed to utilize emission and absorption spectroscopy for monitoring molecular and atomic particulates in gas plasma. An accompanying suite of tools and analytical package designed to utilize information collected by OPAD is known as the Engine Diagnostic Filtering System (EDIFIS). The current combination of these systems identifies atomic and molecular species and quantifies mass loss rates in H2/O2 rocket plumes. Additionally, efforts are being advanced to hardware encode components of the EDIFIS in order to address real-time operational requirements for health monitoring and management. This paper addresses the OPAD with its tool suite, and discusses what is considered a natural progression: a concept for migrating OPAD towards detection of high energy particles, including neutrons and gamma rays. The integration of these tools and capabilities will provide NASA with a systematic approach to monitor space vehicle internal and external environment.

Iron catalyst chemistry in modeling a high-pressure carbon monoxide nanotube reactor.

PubMed

Scott, Carl D; Povitsky, Alexander; Dateo, Christopher; Gökçen, Tahir; Willis, Peter A; Smalley, Richard E

2003-01-01

The high-pressure carbon monoxide (HiPco) technique for producing single-wall carbon nanotubes (SWNTs) is analyzed with the use of a chemical reaction model coupled with flow properties calculated along streamlines, calculated by the FLUENT code for pure carbon monoxide. Cold iron pentacarbonyl, diluted in CO at about 30 atmospheres, is injected into a conical mixing zone, where hot CO is also introduced via three jets at 30 degrees with respect to the axis. Hot CO decomposes the Fe(CO)5 to release atomic Fe. Then iron nucleates and forms clusters that catalyze the formation of SWNTs by a disproportionation reaction (Boudouard) of CO on Fe-containing clusters. Alternative nucleation rates are estimated from the theory of hard sphere collision dynamics with an activation energy barrier. The rate coefficient for carbon nanotube growth is estimated from activation energies in the literature. The calculated growth was found be about an order of magnitude greater than measured, regardless of the nucleation rate. A study of cluster formation in an incubation zone prior to injection into the reactor shows that direct dimer formation from Fe atoms is not as important as formation via an exchange reaction of Fe with CO in FeCO.

Method and apparatus for duct sealing using a clog-resistant insertable injector

DOEpatents

Wang, Duo; Modera, Mark P.

2010-12-14

A method for forming a duct access region through one side of a previously installed air duct, wherein the air duct has an air flow with an air flow direction by inserting an aerosol injector into a previously installed air duct through the access region. The aerosol injector includes a liquid tube having a liquid tube orifice for ejecting a liquid to be atomized; and a propellant cap. The method is accomplished by aligning the aerosol injector with the direction of air flow in the duct; activating an air flow within the duct; and spraying a sealant through the aerosol injector to seal the duct in the direction of the air flow.

Metal shell technology based upon hollow jet instability. [for inertial confinement fusion

NASA Technical Reports Server (NTRS)

Kendall, J. M.; Lee, M. C.; Wang, T. G.

1982-01-01

Spherical shells of submillimeter size are sought as ICF targets. Such shells must be dimensionally precise, smooth, of high strength, and composed of a high atomic number material. A technology for the production of shells based upon the hydrodynamic instability of an annular jet of molten metal is described. Shells in the 0.7-2.0 mm size range have been produced using tin as a test material. Specimens exhibit good sphericity, fair concentricity, and excellent finish over most of the surface. Work involving a gold-lead-antimony alloy is in progress. Droplets of this are amorphous and possess superior surface finish. The flow of tin models that of the alloy well; experiments on both metals show that the technique holds considerable promise.

Partial Hydrothermal Oxidation of High Molecular Weight Unsaturated Carboxylic Acids for Upgrading of Biodiesel Fuel

NASA Astrophysics Data System (ADS)

Kawasaki, K.; Jin, F.; Kishita, A.; Tohji, K.; Enomoto, H.

2007-03-01

With increasing environmental awareness and crude oil price, biodiesel fuel (BDF) is gaining recognition as a renewable fuel which may be used as an alternative diesel fuel without any modification to the engine. The cold flow and viscosity of BDF, however, is a major drawback that limited its use in cold area. In this study, therefore, we investigated that partial oxidation of high molecular weight unsaturated carboxylic acids in subcritical water, which major compositions in BDF, to upgrade biodiesel fuel. Oleic acid, (HOOC(CH2)7CH=CH(CH2)7CH3), was selected as a model compound of high molecular weight unsaturated carboxylic acids. All experiments were performed with a batch reactor made of SUS 316 with an internal volume of 5.7 cm3. Oleic acid was oxidized at 300 °C with oxygen supply varying from 1-10 %. Results showed that a large amount of carboxylic acids and aldehydes having 8-9 carbon atoms were formed. These experimental results suggest that the hydrothermal oxidative cleavage may mainly occur at double bonds and the cleavage of double bonds could improve the cold flow and viscosity of BDF.

Processes of conversion of a hot metal particle into aerogel through clusters

NASA Astrophysics Data System (ADS)

Smirnov, B. M.

2015-10-01

Processes are considered for conversion into a fractal structure of a hot metal micron-size particle that is located in a buffer gas or a gas flow and is heated by an external electric or electromagnetic source or by a plasma. The parameter of this heating is the particle temperature, which is the same in the entire particle volume because of its small size and high conductivity. Three processes determine the particle heat balance: particle radiation, evaporation of metal atoms from the particle surface, and heat transport to the surrounding gas due to its thermal conductivity. The particle heat balance is analyzed based on these processes, which are analogous to those for bulk metals with the small particle size, and its high temperature taken into account. Outside the particle, where the gas temperature is lower than on its surface, the formed metal vapor in a buffer gas flow is converted into clusters. Clusters grow as a result of coagulation until they become liquid, and then clusters form fractal aggregates if they are removed form the gas flow. Subsequently, associations of fractal aggregates join into a fractal structure. The rate of this process increases in medium electric fields, and the formed fractal structure has features of aerogels and fractal fibers. As a result of a chain of the above processes, a porous metal film may be manufactured for use as a filter or catalyst for gas flows.

Nanoscale Pore Imaging and Pore Scale Fluid Flow Modeling in Chalk

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tomutsa, Liviu; Silin, Dmitriy

2004-08-19

For many rocks of high economic interest such as chalk, diatomite, tight gas sands or coal, nanometer scale resolution is needed to resolve the 3D-pore structure, which controls the flow and trapping of fluids in the rocks. Such resolutions cannot be achieved with existing tomographic technologies. A new 3D imaging method, based on serial sectioning and using the Focused Ion Beam (FIB) technology has been developed. FIB allows for the milling of layers as thin as 10 nanometers by using accelerated Ga+ ions to sputter atoms from the sample surface. After each milling step, as a new surface is exposed,more » a 2D image of this surface is generated. Next, the 2D images are stacked to reconstruct the 3D pore or grain structure. Resolutions as high as 10 nm are achievable using such a technique. A new robust method of pore-scale fluid flow modeling has been developed and applied to sandstone and chalk samples. The method uses direct morphological analysis of the pore space to characterize the petrophysical properties of diverse formations. Not only petrophysical properties (porosity, permeability, relative permeability and capillary pressures) can be computed but also flow processes, such as those encountered in various IOR approaches, can be simulated. Petrophysical properties computed with the new method using the new FIB data will be presented. Present study is a part of the development of an Electronic Core Laboratory at LBNL/UCB.« less

Heat transfer in nonequilibrium boundary layer flow over a partly catalytic wall

NASA Astrophysics Data System (ADS)

Wang, Zhi-Hui

2016-11-01

Surface catalysis has a huge influence on the aeroheating performance of hypersonic vehicles. For the reentry flow problem of a traditional blunt vehicle, it is reasonable to assume a frozen boundary layer surrounding the vehicles' nose, and the catalytic heating can be decoupled with the heat conduction. However, when considering a hypersonic cruise vehicle flying in the medium-density near space, the boundary layer flow around its sharp leading-edge is likely to be nonequilibrium rather than frozen due to rarefied gas effects. As a result, there will be a competition between the heat conduction and the catalytic heating. In this paper, the theoretical modeling and the direct simulation Monte Carlo (DSMC) method are employed to study the corresponding rarefied nonequilibrium flow and heat transfer phenomena near the leading edge of the near space hypersonic vehicles. It is found that even under identical rarefication degree, the nonequilibrium degree of the flow and the corresponding heat transfer performance of the sharp leading edges could be different from that of the big blunt noses. A generalized model is preliminarily proposed to describe and to evaluate the competitive effects between the homogeneous recombination of atoms inside the nonequilibrium boundary layer and the heterogeneous recombination of atoms on the catalytic wall surface. The introduced nonequilibrium criterion and the analytical formula are validated and calibrated by the DSMC results, and the physical mechanism is discussed.

Development of a flow system for the determination of cadmium in fuel alcohol using vermicompost as biosorbent and flame atomic absorption spectrometry.

PubMed

Bianchin, Joyce Nunes; Martendal, Edmar; Mior, Renata; Alves, Vanessa Nunes; Araújo, Cleide Sandra Tavares; Coelho, Nívia Maria Melo; Carasek, Eduardo

2009-04-30

In this study a method for the determination of cadmium in fuel alcohol using solid-phase extraction with a flow injection analysis system and detection by flame atomic absorption spectrometry was developed. The sorbent material used was a vermicompost commonly used as a garden fertilizer. The chemical and flow variables of the on-line preconcentration system were optimized by means of a full factorial design. The selected factors were: sorbent mass, sample pH, buffer concentration and sample flow rate. The optimum extraction conditions were obtained using sample pH in the range of 7.3-8.3 buffered with tris(hydroxymethyl)aminomethane at 50 mmol L(-1), a sample flow rate of 4.5 mL min(-1) and 160 mg of sorbent mass. With the optimized conditions, the preconcentration factor, limit of detection and sample throughput were estimated as 32 (for preconcentration of 10 mL sample), 1.7 microg L(-1) and 20 samples per hour, respectively. The analytical curve was linear from 5 up to at least 50 microg L(-1), with a correlation coefficient of 0.998 and a relative standard deviation of 2.4% (35 microg L(-1), n=7). The developed method was successfully applied to spiked fuel alcohol, and accuracy was assessed through recovery tests, with recovery ranging from 94% to 100%.

A Theoretical Evaluation of Secondary Atomization Effects on Engine Performance for Aluminum Gel Propellants

NASA Technical Reports Server (NTRS)

Mueller, D. C.; Turns, S. R.

1994-01-01

A one-dimensional model of a gel-fueled rocket combustion chamber has been developed. This model includes the processes of liquid hydrocarbon burnout, secondary atomization. aluminum ignition, and aluminum combustion. Also included is a model of radiative heat transfer from the solid combustion products to the chamber walls. Calculations indicate that only modest secondary atomization is required to significantly reduce propellant burnout distances, aluminum oxide residual size and radiation heat wall losses. Radiation losses equal to approximately 2-13 percent of the energy released during combustion were estimated. A two-dimensional, two-phase nozzle code was employed to estimate radiation and nozzle two-phase flow effects on overall engine performance. Radiation losses yielded a 1 percent decrease in engine I(sub sp). Results also indicate that secondary atomization may have less effect on two-phase losses than it does on propellant burnout distance and no effect if oxide particle coagulation and shear induced droplet breakup govern oxide particle size. Engine I(sub sp) was found to decrease from 337.4 to 293.7 seconds as gel aluminum mass loading was varied from 0-70 wt percent. Engine I(sub sp) efficiencies, accounting for radiation and two-phase flow effects, on the order of 0.946 were calculated for a 60 wt percent gel, assuming a fragmentation ratio of 5.

What We've Learned from IBEX ENA Imaging of the Heliosheath

NASA Astrophysics Data System (ADS)

Zirnstein, E.

2017-12-01

The Interstellar Boundary Explorer (IBEX) is an Earth-orbiting spacecraft equipped with two single-pixel cameras that detect neutral atoms produced by the interaction of the solar wind (SW) with the very local interstellar medium (VLISM), as well as neutral atoms flowing in from the VLISM itself. Since its launch in 2009, IBEX has provided us with over half a solar cycle of measurements of energetic neutral atom (ENA) fluxes produced in the heliosphere. In particular, a large number of these ENAs originate in the inner heliosheath, a region of nearly incompressible SW plasma that is slowed, compressed, and heated at the termination shock. As the heated SW plasma flows through the heliosheath and down the heliotail, charge-exchange with cold neutral atoms from the VLISM generates ENAs that travel on ballistic trajectories. Some of these ENAs travel to Earth and are detected by IBEX. IBEX all-sky observations of these ENAs show a unique energy and spatial dependence, revealing the structural and plasma properties of the heliosheath. One of the prime scientific objectives of the Interstellar Mapping and Acceleration Probe (IMAP) mission is to understand the SW-VLISM interaction, including the properties of the heliosheath and heliotail. This talk will review key IBEX observations of the inner heliosheath environment, the way they have shaped our understanding of the SW-VLISM interaction, and their implications for the upcoming IMAP mission.

Investigations of the Application of CFD to Flow Expected in the Lower Plenum of the Prismatic VHTR

DOE Office of Scientific and Technical Information (OSTI.GOV)

Richard W.Johnson; Tara Gallaway; Donna P. Guillen

2006-09-01

The Generation IV (Gen IV) very high temperature reactor (VHTR) will either be a prismatic (block) or pebble bed design. However, a prismatic VHTR reference design, based on the General Atomics Gas Turbine-Modular Helium Reactor (GT-MHR) [General Atomics, 1996] has been developed for preliminary analysis purposes [MacDonald, et al., 2003]. Numerical simulation studies reported herein are based on this reference design. In the lower plenum of the prismatic reference design, the flow will be introduced by dozens of turbulent jets from the core above. The jet flow will encounter rows of columns that support the core. The flow from themore » core will have to turn ninety degrees and flow toward the exit duct as it passed through the forest of support columns. Due to the radial variation of the power density in the core, the jets will be at various temperatures at the inlet to the lower plenum. This presents some concerns, including that local hot spots may occur in the lower plenum. This may have a deleterious effect on the materials present as well as cause a variation in temperature to be present as the flow enters the power conversion system machinery, which could cause problems with the operation of the machinery. In the past, systems analysis codes have been used to model flow in nuclear reactor systems. It is recognized, however, that such codes are not capable of modeling the local physics of the flow to be able to analyze for local mixing and temperature variations. This has led to the determination that computational fluid dynamic (CFD) codes be used, which are generally regarded as having the capability of accurately simulating local flow physics. Accurate flow modeling involves determining appropriate modeling strategies needed to obtain accurate analyses. These include determining the fineness of the grid needed, the required iterative convergence tolerance, which numerical discretization method to use, and which turbulence model and wall treatment should be employed. It also involves validating the computer code and turbulence model against a series of separate and combined flow phenomena and selecting the data used for the validation. This report describes progress made to identify proper modeling strategies for simulating the lower plenum flow for the task entitled “CFD software validation of jets in crossflow,” which was designed to investigate the issues pertaining to the validation process. The flow phenomenon previously chosen to investigate is flow in a staggered tube bank because it is shown by preliminary simulations to be the location of the highest turbulence intensity in the lower plenum Numerical simulations were previously obtained assuming that the flow is steady. Various turbulence models were employed along with strategies to reduce numerical error to allow appropriate comparisons of the results. It was determined that the sophisticated Reynolds stress model (RSM) provided the best results. It was later determined that the flow is an unsteady flow wherein circulating eddies grow behind the tube and ‘peel off’ alternately from the top and the bottom of the tube. Additional calculations show that the mean velocity is well predicted when the flow is modeled as an unsteady flow. The results for U are clearly superior for the unsteady computations; the unsteady computations for the turbulence stress are similar to those for the steady calculations, showing the same trends. It is clear that strategie« less

Surface quality of silicon wafer improved by hydrodynamic effect polishing

NASA Astrophysics Data System (ADS)

Peng, Wenqiang; Guan, Chaoliang; Li, Shengyi

2014-08-01

Differing from the traditional pad polishing, hydrodynamic effect polishing (HEP) is non-contact polishing with the wheel floated on the workpiece. A hydrodynamic lubricated film is established between the wheel and the workpiece when the wheel rotates at a certain speed in HEP. Nanoparticles mixed with deionized water are employed as the polishing slurry, and with action of the dynamic pressure, nanoparticles with high chemisorption due to the high specific surface area can easily reacted with the surface atoms forming a linkage with workpiece surface. The surface atoms are dragged away when nanoparticles are transported to separate by the flow shear stress. The development of grand scale integration put extremely high requirements on the surface quality on the silicon wafer with surface roughness at subnanometer and extremely low surface damage. In our experiment a silicon sample was processed by HEP, and the surface topography before and after polishing was observed by the atomic force microscopy. Experiment results show that plastic pits and bumpy structures on the initial surface have been removed away clearly with the removal depth of 140nm by HEP process. The processed surface roughness has been improved from 0.737nm RMS to 0.175nm RMS(10μm×10μm) and the section profile shows peaks of the process surface are almost at the same height. However, the machining ripples on the wheel surface will duplicate on the silicon surface under the action of the hydrodynamic effect. Fluid dynamic simulation demonstrated that the coarse surface on the wheel has greatly influence on the distribution of shear stress and dynamic pressure on the workpiece surface.

Metabolic Profile as a Potential Modifier of Long-Term Radiation Effects on Peripheral Lymphocyte Subsets in Atomic Bomb Survivors.

PubMed

Yoshida, Kengo; Nakashima, Eiji; Kyoizumi, Seishi; Hakoda, Masayuki; Hayashi, Tomonori; Hida, Ayumi; Ohishi, Waka; Kusunoki, Yoichiro

2016-09-01

Immune system impairments reflected by the composition and function of circulating lymphocytes are still observed in atomic bomb survivors, and metabolic abnormalities including altered blood triglyceride and cholesterol levels have also been detected in such survivors. Based on closely related features of immune and metabolic profiles of individuals, we investigated the hypothesis that long-term effects of radiation exposure on lymphocyte subsets might be modified by metabolic profiles in 3,113 atomic bomb survivors who participated in health examinations at the Radiation Effect Research Foundation, Hiroshima and Nagasaki, in 2000-2002. The lymphocyte subsets analyzed involved T-, B- and NK-cell subsets, and their percentages in the lymphocyte fraction were assessed using flow cytometry. Health examinations included metabolic indicators, body mass index, serum levels of total cholesterol, high-density lipoprotein cholesterol, C-reactive protein and hemoglobin A1c, as well as diabetes and fatty liver diagnoses. Standard regression analyses indicated that several metabolic indicators of obesity/related disease, particularly high-density lipoprotein cholesterol levels, were positively associated with type-1 helper T- and B-cell percentages but were inversely associated with naïve CD4 T and NK cells. A regression analysis adjusted for high-density lipoprotein cholesterol revealed a radiation dose relationship with increasing NK-cell percentage. Additionally, an interaction effect was suggested between radiation dose and C-reactive protein on B-cell percentage with a negative coefficient of the interaction term. Collectively, these findings suggest that radiation exposure and subsequent metabolic profile changes, potentially in relationship to obesity-related inflammation, lead to such long-term alterations in lymphocyte subset composition. Because this study is based on cross-sectional and exploratory analyses, the implications regarding radiation exposure, metabolic profiles and circulating lymphocytes warrant future longitudinal and molecular mechanistic studies.

Water co-catalyzed selective dehydrogenation of methanol to formaldehyde and hydrogen

NASA Astrophysics Data System (ADS)

Shan, Junjun; Lucci, Felicia R.; Liu, Jilei; El-Soda, Mostafa; Marcinkowski, Matthew D.; Allard, Lawrence F.; Sykes, E. Charles H.; Flytzani-Stephanopoulos, Maria

2016-08-01

The non-oxidative dehydrogenation of methanol to formaldehyde is considered a promising method to produce formaldehyde and clean hydrogen gas. Although Cu-based catalysts have an excellent catalytic activity in the oxidative dehydrogenation of methanol, metallic Cu is commonly believed to be unreactive for the dehydrogenation of methanol in the absence of oxygen adatoms or oxidized copper. Herein we show that metallic Cu can catalyze the dehydrogenation of methanol in the absence of oxygen adatoms by using water as a co-catalyst both under realistic reaction conditions using silica-supported PtCu nanoparticles in a flow reactor system at temperatures below 250 °C, and in ultra-high vacuum using model PtCu(111) catalysts. Adding small amounts of isolated Pt atoms into the Cu surface to form PtCu single atom alloys (SAAs) greatly enhances the dehydrogenation activity of Cu. Under the same reaction conditions, the yields of formaldehyde from PtCu SAA nanoparticles are more than one order of magnitude higher than on the Cu nanoparticles, indicating a significant promotional effect of individual, isolated Pt atoms. Moreover, this study also shows the unexpected role of water in the activation of methanol. Water, a catalyst for methanol dehydrogenation at low temperatures, becomes a reactant in the methanol steam reforming reactions only at higher temperatures over the same metal catalyst.

Comparative Study on Hot Atom Coronae of Solar and Extrasolar Planets

NASA Astrophysics Data System (ADS)

Shematovich, Valery

Solar/stellar forcing on the upper atmospheres of the solar and extrasolar planets via both absorption of the XUV (soft X-rays and extreme ultraviolet) radiation and atmospheric sputtering results in the formation of an extended neutral corona populated by the suprathermal (hot) H, C, N, and O atoms (see, e.g., Johnson et al., 2008). The hot corona, in turn, is altered by an inflow of the solar wind/magnetospheric plasma and local pick-up ions onto the planetary exosphere. Such inflow results in the formation of the superthermal atoms (energetic neutral atoms - ENAs) due to the charge exchange with the high-energy precipitating ions and can affect the long-term evolution of the atmosphere due to the atmospheric escape. The origin, kinetics and transport of the suprathermal H, C, N, and O atoms in the transition regions (from thermosphere to exosphere) of the planetary atmospheres are discussed. Reactions of dissociative recombination of the ionospheric ions CO _{2} (+) , CO (+) , O _{2} (+) , and N _{2} (+) with thermal electrons are the main photochemical sources of hot atoms. The dissociation of atmospheric molecules by the solar/stellar XUV radiation and accompanying photoelectron fluxes and the induced exothermic photochemistry are also the important sources of the suprathermal atoms. Such kinetic systems with the non-thermal processes are usually investigated with the different (test particles, DSMC, and hybrid) versions of the kinetic Monte Carlo method. In our studies the kinetic energy distribution functions of suprathermal and superthermal atoms were calculated using the stochastic model of the hot planetary corona (Shematovich, 2004, 2010; Groeller et al., 2014), and the Monte Carlo model (Shematovich et al., 2011, 2013) of the high-energy proton and hydrogen atom precipitation into the atmosphere respectively. These functions allowed us to estimate the space distribution of suprathermals in the planetary transition regions. An application of these numerical models to study the atmospheric gas flow in the transition region from the collision-dominated thermosphere to collisionless exosphere, and the non-thermal escape will be discussed and illustrated with the simple 1D-models of the hot coronae of the solar and extrasolar planets. This work is supported by the RFBR project No. 14-02-00838a and by the Basic Research Program of the Presidium of the Russian Academy of Sciences (Program 22). begin{itemize} Johnson et al., Sp. Sci.Rev., 2008, v. 139, 355. Shematovich, Solar System Res., 2004, v.38, 28. Shematovich, Solar System Res., 2010, v.44, 96. Shematovich et al., J. Geophys. Res., 2011, v.116, A11320; 2013, v. 118, 1231. Groeller et al., Planet. Space Sci., 2014.

Disilane-based cyclic deposition/etch of Si, Si:P and Si1-yCy:P layers: I. The elementary process steps

NASA Astrophysics Data System (ADS)

Hartmann, J. M.; Benevent, V.; Barnes, J. P.; Veillerot, M.; Deguet, C.

2013-02-01

We have benchmarked the 550 °C, 20 Torr growth of Si:P and Si1-yCy:P using SiH4 and Si2H6. P segregation has prevented us from reaching P+ ion concentrations in Si higher than a few 1019 cm-3 using SiH4; the resulting surface ‘poisoning’ led to a severe growth rate reduction. Meanwhile, [P+] increased linearly with the phosphine flow when using Si2H6 as the Si precursor; values as high as 1.7 × 1020 cm-3 were obtained. The Si:P growth rate using Si2H6 was initially stable then increased as the PH3 flow increased. Mono-methylsilane flows 6.5-10 times higher were needed with Si2H6 than with SiH4 to reach the same substitutional C concentrations in intrinsic Si1-yCy layers ([C]subst. up to 1.9%). Growth rates were approximately six times higher with Si2H6 than with SiH4, however. 30 nm thick Si1-yCy layers became rough as [C]subst. exceeded 1.6% (formation of increasing numbers of islands). We have also studied the structural and electrical properties of ‘low’ and ‘high’ C content Si1-yCy:P layers (˜ 1.5 and 1.8%, respectively) grown with Si2H6. Adding significant amounts of PH3 led to a reduction of the tensile strain in the films. This was due to the incorporation of P atoms (at the expense of C atoms) in the substitutional sites of the Si matrix. Si1-yCy:P layers otherwise became rough as the PH3 flow increased. Resistivities lower than 1 mΩ cm were nevertheless associated with those Si1-yCy:P layers, with P atomic concentrations at most 3.9 × 1020 cm-3. Finally, we have quantified the beneficial impact of adding GeH4 to HCl for the low-temperature etching of Si. Etch rates 12-36 times higher with HCl + GeH4 than with pure HCl were achieved at 20 Torr. Workable etch rates close to 1 nm min-1 were obtained at 600 °C (versus 750 °C for pure HCl), enabling low-temperature cyclic deposition/etch strategies for the selective epitaxial growth of Si, Si:P and Si1-yCy:P layers on patterned wafers.

Microgravity

NASA Image and Video Library

2004-04-15

A semiconductor's usefulness is determined by how atoms are ordered within the crystal's underlying three-dimensional structure. While this mercury telluride and cadmium telluride alloy sample mixes completely in Earth -based laboratories, convective flows prevent them from mixing uniformly.

Hot Flow Anomalies at Venus

NASA Technical Reports Server (NTRS)

Collinson, G. A.; Sibeck, David Gary; Boardsen, Scott A.; Moore, Tom; Barabash, S.; Masters, A.; Shane, N.; Slavin, J.A.; Coates, A.J.; Zhang, T. L.;

When superfluids are a drag

DOE Office of Scientific and Technical Information (OSTI.GOV)

Roberts, David C

2008-01-01

The article considers the dramatic phenomenon of seemingly frictionless flow of slow-moving superfluids. Specifically the question of whether an object in a superfluid flow experiences any drag force is addressed. A brief account is given of the history of this problem and it is argued that recent advances in ultracold atomic physics can shed much new light on this problem. The article presents the commonly held notion that sufficiently slow-moving superfluids can flow without drag and also discusses research suggesting that scattering quantum fluctuations might cause drag in a superfluid moving at any speed.

Hydrodynamic flow of ions and atoms in partially ionized plasmas.

PubMed

Nemirovsky, R A; Fredkin, D R; Ron, A

2002-12-01

We have derived the hydrodynamic equations of motion for a partially ionized plasma, when the ionized component and the neutral components have different flow velocities and kinetic temperatures. Starting from the kinetic equations for a gas of ions and a gas of atoms we have considered various processes of encounters between the two species: self-collisions, interspecies collisions, ionization, recombination, and charge exchange. Our results were obtained by developing a general approach for the hydrodynamics of a gas in a binary mixture, in particular when the components drift with respect to each other. This was applied to a partially ionized plasma, when the neutral-species gas and the charged-species gas have separate velocities. We have further suggested a generalized version of the relaxation time approximation and obtained the contributions of the interspecies encounters to the transport equations.

Deflection of the Interstellar Neutral Hydrogen Flow Across the Heliospheric Interface: an Interstellar Magnetic Compass

NASA Astrophysics Data System (ADS)

Lallement, R.; Eric, Q.; Jean-Loup, B.; Dimitra, K.; Risto, P.

2005-05-01

Analyses of SOHO-SWAN observations show that the interstellar neutral H flow direction differs by about 4 degrees from the neutral He flow direction recently derived with an unprecedented accuracy using combined data sets (Mobius et al, 2004). The most likely explanation is a distortion of the heliospheric interface under the action of an inclined interstellar magnetic field, with imprints of the distorsion on the neutral H flow due to charge-transfer reactions between H atoms and ions. The direction of the ambient interstellar magnetic field and the heliospheric shape can be derived from the observed deviation. Implications for Voyager trajectories are discussed.

Specific Adaptation of Gas Atomization Processing for Al-Based Alloy Powder for Additive Manufacturing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Anderson, Iver; Siemon, John

The initial three atomization attempts resulted in “freeze-outs” within the pour tubes in the pilot-scale system and yielded no powder. Re-evaluation of the alloy liquidus temperatures and melting characteristics, in collaboration with Alcoa, showed further superheat to be necessary to allow the liquid metal to flow through the pour tube to the atomization nozzle. A subsequent smaller run on the experimental atomization system verified these parameters and was successful, as were all successive runs on the larger pilot scale system. One alloy composition froze-out part way through the atomization on both pilot scale runs. SEM images showed needle formation andmore » phase segregations within the microstructure. Analysis of the pour tube freeze-out microstructures showed that large needles formed within the pour tube during the atomization experiment, which eventually blocked the melt stream. Alcoa verified the needle formation in this alloy using theoretical modeling of phase solidification. Sufficient powder of this composition was still generated to allow powder characterization and additive manufacturing trials at Alcoa.« less

Thermal modeling using enthalpy methods to aid in the study of microstructural changes of multilayered phase change optical memories

NASA Astrophysics Data System (ADS)

Nagpal, Swati; Aurora, Aradhna

1999-11-01

In DOW type of phase change optical memories the focus has been mainly on gestate based systems due to their good overwriting capability and very high order cyclability. To avoid the material deterioration problems such as material flow, high melting point, high viscosity or high-density components such as CrTe, (which have the same refractive index) can be added to the active layer. This has led to an improved performance of overwrite cycles from 105 to 106. Material flow occurs due to void formation. Voids and sinks are formed due to porosity of the active layer because the active layer has a density lower than that of the bulk material. One of the reasons for the formation and coalescence of voids is the way in which the film is deposited viz. Sputtering which makes Ar atoms accumulate in the films during deposition. Also the mechanical strength of the protective layer effects the repeatability of the active layer. All the above mentioned processes occur during melting and re- solidification of the nano-sized spots which are laser irradiated. Since the structure of the protective layers is very important in controlling the void formation, it is very important to study the thermal modeling of the full layer structure.

Study of Spray Disintegration in Accelerating Flow Fields

NASA Technical Reports Server (NTRS)

Nurick, W. H.

1972-01-01

An analytical and experimental investigation was conducted to perform "proof of principlem experiments to establish the effects of propellant combustion gas velocity on propella'nt atomization characteristics. The propellants were gaseous oxygen (GOX) and Shell Wax 270. The fuel was thus the same fluid used in earlier primary cold-flow atomization studies using the frozen wax method. Experiments were conducted over a range in L* (30 to 160 inches) at two contraction ratios (2 and 6). Characteristic exhaust velocity (c*) efficiencies varied from SO to 90 percent. The hot fire experimental performance characteristics at a contraction ratio of 6.0 in conjunction with analytical predictions from the drovlet heat-up version of the Distributed Energy Release (DER) combustion computer proDam showed that the apparent initial dropsize compared well with cold-flow predictions (if adjusted for the gas velocity effects). The results also compared very well with the trend in perfomnce as predicted with the model. significant propellant wall impingement at the contraction ratio of 2.0 precluded complete evaluation of the effect of gross changes in combustion gas velocity on spray dropsize.

Flow Property Measurement Using Laser-Induced Fluorescence in the NASA Ames Interaction Heating Facility

NASA Technical Reports Server (NTRS)

Grinstead, Jay Henderson; Porter, Barry J.; Carballo, Julio Enrique

2011-01-01

The spectroscopic diagnostic technique of two photon absorption laser-induced fluorescence (TALIF) of atomic species has been applied to single-point measurements of velocity and static temperature in the NASA Ames Interaction Heating Facility (IHF) arc jet. Excitation spectra of atomic oxygen and nitrogen were recorded while scanning a tunable dye laser over the absorption feature. Thirty excitation spectra were acquired during 8 arc jet runs at two facility operating conditions; the number of scans per run varied between 2 and 6. Curve fits to the spectra were analyzed to recover their Doppler shifts and widths, from which the flow velocities and static temperatures, respectively, were determined. An increase in the number of independent flow property pairs from each as-measured scan was obtained by extracting multiple lower-resolution scans. The larger population sample size enabled the mean property values and their uncertainties for each run to be characterized with greater confidence. The average plus or minus 2 sigma uncertainties in the mean velocities and temperatures for all 8 runs were plus or minus 1.4% and plus or minus 11%, respectively.

Formation of manganese nanoclusters in a sputtering/aggregation source and the roles of individual operating parameters

NASA Astrophysics Data System (ADS)

Khojasteh, Malak; Kresin, Vitaly V.

2016-12-01

We describe the production of size selected manganese nanoclusters using a dc magnetron sputtering/aggregation source. Since nanoparticle production is sensitive to a range of overlapping operating parameters (in particular, the sputtering discharge power, the inert gas flow rates, and the aggregation length) we focus on a detailed map of the influence of each parameter on the average nanocluster size. In this way it is possible to identify the main contribution of each parameter to the physical processes taking place within the source. The discharge power and argon flow supply the atomic vapor, and argon also plays the crucial role in the formation of condensation nuclei via three-body collisions. However, neither the argon flow nor the discharge power have a strong effect on the average nanocluster size in the exiting beam. Here the defining role is played by the source residence time, which is governed by the helium supply and the aggregation path length. The size of mass selected nanoclusters was verified by atomic force microscopy of deposited particles.

Radiation-Spray Coupling for Realistic Flow Configurations

NASA Technical Reports Server (NTRS)

El-Asrag, Hossam; Iannetti, Anthony C.

2011-01-01

Three Large Eddy Simulations (LES) for a lean-direct injection (LDI) combustor are performed and compared. In addition to the cold flow simulation, the effect of radiation coupling with the multi-physics reactive flow is analyzed. The flame let progress variable approach is used as a subgrid combustion model combined with a stochastic subgrid model for spray atomization and an optically thin radiation model. For accurate chemistry modeling, a detailed Jet-A surrogate mechanism is utilized. To achieve realistic inflow, a simple recycling technique is performed at the inflow section upstream of the swirler. Good comparison is shown with the experimental data mean and root mean square profiles. The effect of combustion is found to change the shape and size of the central recirculation zone. Radiation is found to change the spray dynamics and atomization by changing the heat release distribution and the local temperature values impacting the evaporation process. The simulation with radiation modeling shows wider range of droplet size distribution by altering the evaporation rate. The current study proves the importance of radiation modeling for accurate prediction in realistic spray combustion configurations, even for low pressure systems.

Cosmic ray exposure dating with in situ produced cosmogenic 3He: results from young Hawaiian lava flows

USGS Publications Warehouse

Kurz, M.D.; Colodner, D.; Trull, T.W.; Moore, R.B.; O'Brien, K.

1990-01-01

In an effort to determine the in situ production rate of spallation-produced cosmogenic 3He, and evaluate its use as a surface exposure chronometer, we have measured cosmogenic helium contents in a suite of Hawaiian radiocarbon-dated lava flows. The lava flows, ranging in age from 600 to 13,000 years, were collected from Hualalai and Mauna Loa volcanoes on the island of Hawaii. Because cosmic ray surface-exposure dating requires the complete absence of erosion or soil cover, these lava flows were selected specifically for this purpose. The 3He production rate, measured within olivine phenocrysts, was found to vary significantly, ranging from 47 to 150 atoms g-1 yr-1 (normalized to sea level). Although there is considerable scatter in the data, the samples younger than 10,000 years are well-preserved and exposed, and the production rate variations are therefore not related to erosion or soil cover. Data averaged over the past 2000 years indicate a sea-level 3He production rate of 125 ?? 30 atoms g-1 yr-1, which agrees well with previous estimates. The longer record suggests a minimum in sea level normalized 3He production rate between 2000 and 7000 years (55 ?? 15 atoms g-1 yr-1), as compared to samples younger than 2000 years (125 ?? 30 atoms g-1 yr-1), and those between 7000 and 10,000 years (127 ?? 19 atoms g-1 yr-1). The minimum in production rate is similar in age to that which would be produced by variations in geomagnetic field strength, as indicated by archeomagnetic data. However, the production rate variations (a factor of 2.3 ?? 0.8) are poorly determined due to the large uncertainties in the youngest samples and questions of surface preservation for the older samples. Calculations using the atmospheric production model of O'Brien (1979) [35], and the method of Lal and Peters (1967) [11], predict smaller production rate variations for similar variation in dipole moment (a factor of 1.15-1.65). Because the production rate variations, archeomagnetic data, and theoretical estimates are not well determined at present, the relationship between dipole moment and production rate will require further study. Precise determination of the production rate is an important uncertainty in the surface-exposure technique, but the data demonstrate that it is feasible to date samples as young as 600 years of age providing that there has been no erosion or soil cover. Therefore, the technique will have important applications for volcanology, glacial geology, geomorphology and archaeology. ?? 1990.

Solar photolysis of ozone to singlet D oxygen atoms

NASA Technical Reports Server (NTRS)

Blackburn, Thomas E.; Bairai, Solomon T.; Stedman, Donald H.

1992-01-01

The ground-level photolysis frequency of ozone J(O3) to produce metastable singlet D oxygen atoms (O (D-1)) is measured using a novel instrumental technique involving electrical conductivity. The O(D-1) atoms produced react with nitrous oxide (N2O) carrier gas to form higher oxides of nitrogen (NO(x)). These oxides were detected by mixing with methanol and determining the increase in electrical conductivity with a continuous-flow dual conductivity cell. Over 70 days of data were collected under varying sky conditions. The effect of temperature on J(O3) was measured. The results agree with model predictions. The effects of atmospheric aerosols, changes in overhead ozone column, and local cloudiness are discussed.