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Sample records for evaporating fuel sprays

  1. Evaporation And Ignition Of Dense Fuel Sprays

    NASA Technical Reports Server (NTRS)

    Bellan, Josette; Harstad, Kenneth G.

    1988-01-01

    Simple theoretical model makes useful predictions of trends. Pair of reports presents theoretical model of evaporation and ignition of sprayed liquid fuel. Developed as part of research in combustion of oil and liquid fuels derived from coal, tar sand, and shale in furnace. Work eventually contributes to increase efficiency of combustion and decrease pollution generated by burning of such fuels.

  2. Characterization of Liquid Fuel Evaporation of a Lifted Methanol Spray Flame in a Vitiated Coflow Burner

    NASA Technical Reports Server (NTRS)

    Cabra, Ricardo; Dibble, Robert W.; Chen, Jyh-Yuan

    2002-01-01

    An experimental investigation of lifted spray flames in a coflow of hot, vitiated gases is presented. The vitiated coflow burner is a spray flame that issues into a coaxial flow of hot combustion products from a lean, premixed H2/Air flame. The spray flame in a vitiated coflow emulates the combustion that occurs in many advanced combustors without the detailed fluid mechanics. Two commercially available laser diagnostic systems are used to characterize the spray flame and to demonstrate the vitiated coflow burner's amenability to optical investigation. The Ensemble Particle Concentration and Size (EPCS) system is used to measure the path-average droplet size distribution and liquid volume fraction at several axial locations while an extractive probe instrument named the Real-time Fuel-air Analyzer (RFA) is used to measure the air to fuel ratio downstream of the spray nozzle with high temporal and spatial resolution. The effect of coflow conditions (stoichiometry) and dilution of the fuel with water was studied with the EPCS optical system. As expected, results show that water retards the evaporation and combustion of fuels. Measurements obtained by the RFA extractive probe show that while the Delavan manufactured nozzle does distribute the fuel over the manufacturer specified spray angle, it unfortunately does not distribute the fuel uniformly, providing conditions that may result in the production of unwanted NOx. Despite some limitations due to the inherent nature of the experimental techniques, the two diagnostics can be readily applied to spray flames in the vitiated coflow environment.

  3. Numerical prediction of a turbulent evaporating fuel spray in a recirculating flow

    NASA Astrophysics Data System (ADS)

    Chen, Xi-Qing; Pereira, Fernandes

    1994-03-01

    A comprehensive spray evaporation model, based on a Eulerian model of the gas field and a Lagrangian model of the droplet field in conjunction with the stochastic description of gas turbulence effect on the droplet motion, is applied to a turbulent evaporating spray in a recirculating flow and validated by comparison between predictions and measurements. Unlike many previous numerical predictions this note has been able to avoid the usual problem of a lack of detailed initial droplet-size and velocity-distribution conditions, and incorporated the turbulent temporal and directional correlation. We have adopted Zhou and Leschziner's methodology to include turbulent temporal and directional correlations in the numerical modeling, which has proved to be an improvement over the conventional particle-eddy modeling in simple flows.

  4. Quantitative fuel vapor/air mixing imaging in droplet/gas regions of an evaporating spray flow using filtered Rayleigh scattering.

    PubMed

    Allison, Patton M; McManus, Thomas A; Sutton, Jeffrey A

    2016-03-15

    This Letter demonstrates the application of filtered Rayleigh scattering (FRS) for quantitative two-dimensional fuel vapor/air mixing measurements in an evaporating hydrocarbon fuel spray flow. Using the FRS approach, gas-phase measurements are made in the presence of liquid-phase droplets without interference. Effective suppression of the liquid-phase droplet scattering using FRS is enabled by the high spectral purity of the current Nd:YAG laser system. Simultaneous Mie-scattering imaging is used to visualize the droplet field and illustrate the droplet loading under which the FRS imaging is applied in the current spray flows. The initial quantification of the FRS imaging is based on calibration measurements from a flow cell of known fuel vapor/air mixtures, while future work targets the utilization of a Rayleigh-Brillouin spectral model for quantification of the FRS signals.

  5. Feasibility Demonstration of Exciplex Fluorescence Measurements in Evaporating Laminar Sprays of Diesel Fuel

    DTIC Science & Technology

    2011-05-15

    Next, we introduce PDPA measurements of the droplet size and velocity distributions to correlate them with the spectroscopic ones. Ultimately we...reflection from a dye cell used for intensity calibration of the laser beam. A TSI Phase Doppler Particle Analyzer ( PDPA ) is used to measure the...temperature temperature. PDPA Measurements Figure 6 shows histograms of the droplet diameter at different fuel flow rates. The droplet diameter

  6. Measurements in liquid fuel sprays

    NASA Technical Reports Server (NTRS)

    Chigier, N.

    1984-01-01

    Techniques for studying the events directly preceding combustion in the liquid fuel sprays are being used to provide information as a function of space and time on droplet size, shape, number density, position, angle of flight and velocity. Spray chambers were designed and constructed for: (1) air-assist liquid fuel research sprays; (2) high pressure and temperature chamber for pulsed diesel fuel sprays; and (3) coal-water slurry sprays. Recent results utilizing photography, cinematography, and calibration of the Malvern particle sizer are reported. Systems for simultaneous measurement of velocity and particle size distributions using laser Doppler anemometry interferometry and the application of holography in liquid fuel sprays are being calibrated.

  7. PDF modeling of vapour micromixing in turbulent evaporating sprays

    NASA Astrophysics Data System (ADS)

    Anand, Gaurav; Jenny, Patrick

    Spray combustion is a complex phenomena finding its application in many combustion devices like gas turbines, diesel engines, liquid-fueled rocket engines etc. This phenomena is characterised by the break up of the liquid fuel sheet, followed by atomisation, droplet dispersion and its evaporation, mixing of the fuel vapour with the oxidiser and eventually its combustion. However, the present study is focused on the turbulence modification of the carrier phase (i.e. gas) and the fuel vapour mixing. Flows seeded with droplet volume fraction less than 10-3 are considered so that the inter-droplet collision effects are negligible.

  8. Dense spray evaporation as a mixing process

    NASA Astrophysics Data System (ADS)

    de Rivas, A.; Villermaux, E.

    2016-05-01

    We explore the processes by which a dense set of small liquid droplets (a spray) evaporates in a dry, stirred gas phase. A dense spray of micron-sized liquid (water or ethanol) droplets is formed in air by a pneumatic atomizer in a closed chamber. The spray is conveyed in ambient air as a plume whose extension depends on the relative humidity of the diluting medium. Standard shear instabilities develop at the plume edge, forming the stretched lamellar structures familiar with passive scalars. Unlike passive scalars however, these lamellae vanish in a finite time, because individual droplets evaporate at their border in contact with the dry environment. Experiments demonstrate that the lifetime of an individual droplet embedded in a lamellae is much larger than expected from the usual d2 law describing the fate of a single drop evaporating in a quiescent environment. By analogy with the way mixing times are understood from the convection-diffusion equation for passive scalars, we show that the lifetime of a spray lamellae stretched at a constant rate γ is tv=1/γ ln(1/+ϕ ϕ ) , where ϕ is a parameter that incorporates the thermodynamic and diffusional properties of the vapor in the diluting phase. The case of time-dependent stretching rates is examined too. A dense spray behaves almost as a (nonconserved) passive scalar.

  9. Modeling of gas turbine fuel nozzle spray

    SciTech Connect

    Rizk, N.K.; Chin, J.S.; Razdan, M.K.

    1997-01-01

    Satisfactory performance of the gas turbine combustor relies on the careful design of various components, particularly the fuel injector. It is, therefore, essential to establish a fundamental basis for fuel injection modeling that involves various atomization processes. A two-dimensional fuel injection model has been formulated to simulate the airflow within and downstream of the atomizer and address the formation and breakup of the liquid sheet formed at the atomizer exit. The sheet breakup under the effects of airblast, fuel pressure, or the combined atomization mode of the air-assist type is considered in the calculation. The model accounts for secondary breakup of drops and the stochastic Lagrangian treatment of spray. The calculation of spray evaporation addresses both droplet heat-up and steady-state mechanisms, and fuel vapor concentration is based on the partial pressure concept. An enhanced evaporation model has been developed that accounts for multicomponent, finite mass diffusivity and conductivity effects, and addresses near-critical evaporation. The present investigation involved predictions of flow and spray characteristics of two distinctively different fuel atomizers under both nonreacting and reacting conditions. The predictions of the continuous phase velocity components and the spray mean drop sizes agree well with the detailed measurements obtained for the two atomizers, which indicates the model accounts for key aspects of atomization. The model also provides insight into ligament formation and breakup at the atomizer exit and the initial drop sizes formed in the atomizer near field region where measurements are difficult to obtain. The calculations of the reacting spray show the fuel-rich region occupied most of the spray volume with two-peak radial gas temperature profiles. The results also provided local concentrations of unburned hydrocarbon and CO in atomizer flowfield.

  10. On the role of physiochemical properties on evaporation behavior of DISI biofuel sprays

    NASA Astrophysics Data System (ADS)

    Knorsch, Tobias; Heldmann, Markus; Zigan, Lars; Wensing, Michael; Leipertz, Alfred

    2013-06-01

    Biofuels and alternative fuels are increasingly being blended to conventional gasoline fuel to reduce the overall CO2 emissions. The effect on NOx and soot formation is still unclear as the atomization and evaporation of gasoline with biocomponents differ depending on fuel specific physiochemical properties. This work focuses on describing the biofuel evaporation behavior of gasoline sprays at homogeneous charge (early injection timing) and stratified-charge conditions (late injection timing mode) used in modern direct injection spark ignition engines (DISI). A spray plume of a 6-hole solenoid injector is analyzed in terms of liquid spray propagation, and local droplet sizes studied in an injection chamber. Depending on the operating conditions, different physiochemical properties are found to dominate the atomization and evaporation processes: For low and moderate ambient temperature and pressure, high-boiling point components show a strong influence on the spray droplet size distribution. However, at elevated temperature and pressure, the evaporation behavior changes completely. Due to a high degree of evaporation, the evaporation cooling effect dominates the local droplet sizes. Fuel mixtures owing a larger heat of vaporization show larger droplet sizes—even if these fuels have a lower boiling point. Depending on the local evaporation behavior, the different remaining droplet momentum in the spray controls the air entrainment and the subsequent progress of evaporation and mixing. Overall, it can be stated that the heat of vaporization is a dominating physiochemical property for the droplet evaporation rate at high-level supercharged conditions.

  11. Statistical Model of Evaporating Multicomponent Fuel Drops

    NASA Technical Reports Server (NTRS)

    Harstad, Kenneth; LeClercq, Patrick; Bellan, Josette

    2007-01-01

    An improved statistical model has been developed to describe the chemical composition of an evaporating multicomponent- liquid drop and of the mixture of gases surrounding the drop. The model is intended for use in computational simulations of the evaporation and combustion of sprayed liquid fuels, which are typically mixtures of as many as hundreds of different hydrocarbon compounds. The present statistical model is an approximation designed to afford results that are accurate enough to contribute to understanding of the simulated physical and chemical phenomena, without imposing an unduly large computational burden.

  12. Simulations of Evaporating Multicomponent Fuel Drops

    NASA Technical Reports Server (NTRS)

    Bellan, Josette; Le Clercq, Patrick

    2005-01-01

    A paper presents additional information on the subject matter of Model of Mixing Layer With Multicomponent Evaporating Drops (NPO-30505), NASA Tech Briefs, Vol. 28, No. 3 (March 2004), page 55. To recapitulate: A mathematical model of a three-dimensional mixing layer laden with evaporating fuel drops composed of many chemical species has been derived. The model is used to perform direct numerical simulations in continuing studies directed toward understanding the behaviors of sprays of liquid petroleum fuels in furnaces, industrial combustors, and engines. The model includes governing equations formulated in an Eulerian and a Lagrangian reference frame for the gas and drops, respectively, and incorporates a concept of continuous thermodynamics, according to which the chemical composition of a fuel is described by use of a distribution function. In this investigation, the distribution function depends solely on the species molar weight. The present paper reiterates the description of the model and discusses further in-depth analysis of the previous results as well as results of additional numerical simulations assessing the effect of the mass loading. The paper reiterates the conclusions reported in the cited previous article, and states some new conclusions. Some new conclusions are: 1. The slower evaporation and the evaporation/ condensation process for multicomponent-fuel drops resulted in a reduced drop-size polydispersity compared to their single-component counterpart. 2. The inhomogeneity in the spatial distribution of the species in the layer increases with the initial mass loading. 3. As evaporation becomes faster, the assumed invariant form of the molecular- weight distribution during evaporation becomes inaccurate.

  13. Photomicrographic Studies of Fuel Sprays

    NASA Technical Reports Server (NTRS)

    Lee, Dana W; Spencer, Robert C

    1934-01-01

    A large number of photomicrographs of fuel sprays were taken for the purpose of studying the spray structure and the process of spray formation. They were taken at magnifying powers of 2.5, 3.25, and 10, using a spark discharge of very short duration for illumination. Several types and sizes of nozzles were investigated, different liquids were used, and a wide range of injection pressures was employed. The sprays were photographed as they were injected into a glass-walled chamber in which the air density was varied from 14 atmospheres to 0.0013 atmosphere.

  14. 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.

  15. A parametric study of a multiple droplet spray evaporator

    NASA Astrophysics Data System (ADS)

    Rizza, J. J.

    1984-06-01

    In this paper, a closed form solution is presented for spray evaporation on the surface of a spray evaporator. A parametric analysis is performed using a multiple droplet model. Droplets on the evaporator surface are considered as point sinks of heat in a fixed geometric pattern. The method of image systems is used to satisfy both the heat conduction equation and the boundary condition equations. The evaporator parameters considered in the model are droplet size, distnces between droplets, evaporator wall thickness, wall conductivity and evaporator wall temperatures. The results include the heat flux profiles for a number of droplet spray densities and evaporator wall thicknesses. The results illustrate the importance of a number of physical parameters on the design of a spray evaporator. The relative spacing of the droplets on the surface of the evaporator is of paramount importance to the optimum utilization of the evaporator surface area. Both qualitative and quantitative information is presented on the system performance relative to parameter variability. In particular, information is provided to determine which set of conditions provides a uniform evaporator heat flux. This condition is desirable, since it makes optimum use of the evaporator surface relative to evaporation rate and heat transfer rate. The validity of the presentation is demonstrated by comparison with previously published experimental data.

  16. Detailed fuel spray analysis techniques

    NASA Technical Reports Server (NTRS)

    Mularz, E. J.; Bosque, M. A.; Humenik, F. M.

    1983-01-01

    Detailed fuel spray analyses are a necessary input to the analytical modeling of the complex mixing and combustion processes which occur in advanced combustor systems. It is anticipated that by controlling fuel-air reaction conditions, combustor temperatures can be better controlled, leading to improved combustion system durability. Thus, a research program is underway to demonstrate the capability to measure liquid droplet size, velocity, and number density throughout a fuel spray and to utilize this measurement technique in laboratory benchmark experiments. The research activities from two contracts and one grant are described with results to data. The experiment to characterize fuel sprays is also described. These experiments and data should be useful for application to and validation of turbulent flow modeling to improve the design systems of future advanced technology engines.

  17. Mechanisms of Smoke Reduction in the High-Pressure Combustion of Emulsified Fuels. Volume 3. Experimental Measurements and Computer Modeling of Evaporating Emulsified and Neat Fuel Sprays.

    DTIC Science & Technology

    1984-05-01

    20 9. COMPARISON OF SMD ON CENTERLINE AND EDGE OF SPRAY ....... 24 . 10. COMPARISON OF ROSIN - RAMMLER N PARAMETER...of two parameters defining a Rosin - Rammler , log-normal, or normal distribution, or as a histogram of 15 size . classes of drops without any assumption...about the shape of the distribution. Although .- all of the distributions have been tried, the Rosin - Rammler has generally provided the best fit and

  18. Ignition of Fuel Sprays.

    DTIC Science & Technology

    1986-06-01

    bidisperse distribution, k = 2. For a continuous size distribution such as Rosin - Rammler distribution [15], k will be infinite and the summation in Eq...with do = 50 microns. In Figure 2, the ignition time delays are plotted versus the overall equivalence ratios for decane fuel. Note that for the...ignition-delay plots in Figures 1-4, we could have plotted ignition energies, but the conclusions would be the same. 15.0 ~~~Q( ,) .._ 10.0 A - do - 100

  19. Fine structure of the vapor field in evaporating dense sprays

    NASA Astrophysics Data System (ADS)

    Villermaux, E.; Moutte, A.; Amielh, M.; Meunier, P.

    2017-07-01

    Making use of an original technique which permits the simultaneous measurement of both the displacement field of evaporating droplets in a spray, and of their vapor, we investigate the relevance of a scenario introduced earlier to describe the evaporation dynamics of dense sprays [Phys. Rev. Fluids 1, 014201 (2016), 10.1103/PhysRevFluids.1.014201]. A plume of dense acetone droplets evaporating in air is studied, for which the stirring field is measured by particle image velocimetry of the droplets, and the vapor field is imaged quantitatively by laser-induced fluorescence. We show, thanks to these unique in situ measurements, that the spray boundary with the diluting environment is slaved at the dynamics of its saturating vapor concentration field, whose structure is analyzed for different well defined local flow topologies.

  20. Evaluation of a locally homogeneous model of spray evaporation

    NASA Technical Reports Server (NTRS)

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

    1979-01-01

    A model of spray evaporation which employs a second-order turbulence model in conjunction with the locally homogeneous flow approximation, which implies infinitely fast interphase transport rates is presented. Measurements to test the model were completed for single phase constant and variable density jets, as well as an evaporating spray in stagnant air. Profiles of mean velocity, composition, temperature and drop size distribution as well as velocity fluctuations and Reynolds stress, were measured within the spray. Predictions were in agreement with measurements in single phase flows and also with many characteristics of the spray, e.g. flow width, radial profiles of mean and turbulent quantities, and the axial rate of decay of mean velocity and mixture fraction.

  1. Structure of Evaporating and Combusting Sprays: Measurements and Predictions

    NASA Technical Reports Server (NTRS)

    Shuen, J. S.; Solomon, A. S. P.; Faeth, G. M.

    1983-01-01

    Complete measurements of the structure of nonevaporating, evaporating and combusting sprays for sufficiently well defined boundary conditions to allow evaluation of models of these processes were obtained. The development of rational design methods for aircraft combustion chambers and other devices involving spray combustion were investigated. Three methods for treating the discrete phase are being considered: a locally homogeneous flow (LHF) model, a deterministic separated flow (DSF) model, and a stochastic separated flow (SSF) model. The main properties of these models are summarized.

  2. Apparatus for Spraying Thin Films by the Flash Evaporation Method,

    DTIC Science & Technology

    The article describes a flash evaporation apparatus used for coating materials with compounds and alloys. The apparatus is simple and easy to produce and can be mounted in a conventional vacuum apparatus. The operation of this apparatus was tested during the spraying of the InSb thin films .

  3. Experiments on the Distribution of Fuel in Fuel Sprays

    NASA Technical Reports Server (NTRS)

    Lee, Dana W

    1933-01-01

    The distribution of fuel in sprays for compression-ignition engines was investigated by taking high-speed spark photographs of fuel sprays reproduced under a wide variety of conditions, and also by injecting them against pieces of plasticine. A photographic study was made of sprays injected into evacuated chambers, into the atmosphere, into compressed air, and into transparent liquids. Pairs of identical sprays were injected counter to each other and their behavior analyzed. Small high velocity air jets were directed normally to the axes of fuel sprays, with the result that the envelope of spray which usually obscures the core was blown aside, leaving the core exposed on one side. The results showed that the distribution of the fuel within the sprays was very uneven.

  4. The influence of droplet evaporation on fuel-air mixing rate in a burner

    NASA Technical Reports Server (NTRS)

    Komiyama, K.; Flagan, R. C.; Heywood, J. B.

    1977-01-01

    Experiments involving combustion of a variety of hydrocarbon fuels in a simple atmospheric pressure burner were used to evaluate the role of droplet evaporation in the fuel/air mixing process in liquid fuel spray flames. Both air-assist atomization and pressure atomization processes were studied; fuel/air mixing rates were determined on the basis of cross-section average oxygen concentrations for stoichiometric overall operation. In general, it is concluded that droplets act as point sources of fuel vapor until evaporation, when the fuel jet length scale may become important in determining nonuniformities of the fuel vapor concentration. In addition, air-assist atomizers are found to have short droplet evaporation times with respect to the duration of the fuel/air mixing process, while for the pressure jet atomizer the characteristic evaporation and mixing times are similar.

  5. Dynamic characteristics of pulsed supersonic fuel sprays

    NASA Astrophysics Data System (ADS)

    Pianthong, K.; Matthujak, A.; Takayama, K.; Milton, B. E.; Behnia, M.

    2008-06-01

    This paper describes the dynamic characteristics of pulsed, supersonic liquid fuel sprays or jets injected into ambient air. Simple, single hole nozzles were employed with the nozzle sac geometries being varied. Different fuel types, diesel fuel, bio-diesel, kerosene, and gasoline were used to determine the effects of fuel properties on the spray characteristics. A vertical two-stage light gas gun was employed as a projectile launcher to provide a high velocity impact to produce the liquid jet. The injection pressure was around 0.88-1.24 GPa in all cases. The pulsed, supersonic fuel sprays were visualized by using a high-speed video camera and shadowgraph method. The spray tip penetration and velocity attenuation and other characteristics were examined and are described here. An instantaneous spray tip velocity of 1,542 m/s (Mach number 4.52) was obtained. However, this spray tip velocity can be sustained for only a very short period (a few microseconds). It then attenuates very quickly. The phenomenon of multiple high frequency spray pulses generated by a single shot impact and the changed in the angle of the shock structure during the spray flight, which had already been observed in previous studies, is again noted. Multiple shock waves from the conical nozzle spray were also clearly captured.

  6. CFD Modeling of Superheated Fuel Sprays

    NASA Technical Reports Server (NTRS)

    Raju, M. S.

    2008-01-01

    An understanding of fuel atomization and vaporization behavior at superheat conditions is identified to be a topic of importance in the design of modern supersonic engines. As a part of the NASA aeronautics initiative, we have undertaken an assessment study to establish baseline accuracy of existing CFD models used in the evaluation of a ashing jet. In a first attempt towards attaining this goal, we have incorporated an existing superheat vaporization model into our spray solution procedure but made some improvements to combine the existing models valid at superheated conditions with the models valid at stable (non-superheat) evaporating conditions. Also, the paper reports some validation results based on the experimental data obtained from the literature for a superheated spray generated by the sudden release of pressurized R134A from a cylindrical nozzle. The predicted profiles for both gas and droplet velocities show a reasonable agreement with the measured data and exhibit a self-similar pattern similar to the correlation reported in the literature. Because of the uncertainty involved in the specification of the initial conditions, we have investigated the effect of initial droplet size distribution on the validation results. The predicted results were found to be sensitive to the initial conditions used for the droplet size specification. However, it was shown that decent droplet size comparisons could be achieved with properly selected initial conditions, For the case considered, it is reasonable to assume that the present vaporization models are capable of providing a reasonable qualitative description for the two-phase jet characteristics generated by a ashing jet. However, there remains some uncertainty with regard to the specification of certain initial spray conditions and there is a need for experimental data on separate gas and liquid temperatures in order to validate the vaporization models based on the Adachi correlation for a liquid involving R134A.

  7. Modeling subgrid scale mixture fraction variance in LES of evaporating spray

    SciTech Connect

    Pera, Cecile; Reveillon, Julien; Vervisch, Luc; Domingo, Pascale

    2006-09-15

    Simulations of a dilute spray evaporating in spatially decaying homogeneous turbulence are performed. An Eulerian description of the flow is adopted, while the behavior of the discrete liquid phase is captured using Lagrangian modeling. Time and length scales of the continuous carrier phase are fully simulated; and by varying the properties of the modeled spray, a database of spray carrier phase direct numerical simulation (CP-DNS) is obtained. The CP-DNS is then filtered on a coarse grid to conduct a priori tests of subgrid scale (SGS) closures. The objective is to provide methods for approximating the level of SGS mixture fraction variance in large eddy simulation (LES) of fuel spray turbulent combustion. Direct estimation of the variance from the scales resolved in LES is first discussed. Then, the solving of a balance equation to get the variance is addressed, with closures for the scalar dissipation rate and the correlation between vapor source and mixture fraction. From the results, a procedure to couple spray evaporation with SGS turbulent combustion modeling emerges. (author)

  8. Evaluation of a locally homogeneous model of spray evaporation

    NASA Technical Reports Server (NTRS)

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

    1978-01-01

    Measurements were conducted on an evaporating spray in a stagnant environment. The spray was formed using an air-atomizing injector to yield a Sauter mean diameter of the order of 30 microns. The region where evaporation occurred extended approximately 1 m from the injector for the test conditions. Profiles of mean velocity, temperature, composition, and drop size distribution, as well as velocity fluctuations and Reynolds stress, were measured. The results are compared with a locally homogeneous two-phase flow model which implies no velocity difference and thermodynamic equilibrium between the phases. The flow was represented by a k-epsilon-g turbulence model employing a clipped Gaussian probability density function for mixture fraction fluctuations. The model provides a good representation of earlier single-phase jet measurements, but generally overestimates the rate of development of the spray. Using the model predictions to represent conditions along the centerline of the spray, drop life-history calculations were conducted which indicate that these discrepancies are due to slip and loss of thermodynamic equilibrium between the phases.

  9. Preliminary Photomicrographic Studies of Fuel Sprays

    NASA Technical Reports Server (NTRS)

    Lee, Dana W; Spencer, Robert C

    1932-01-01

    Photomicrographs were taken of fuel sprays injected into air at various densities for the purpose of studying the spray structure and the stages in the atomization of the fuel. The photomicrographs were taken at magnifying powers of 2.5, 3.25, and 10, using a spark discharge of very short duration for illumination. The results indicate that the theory advanced by Dr. R. A. Castleman, Jr., on the atomization of fuel in carburetors may also be applied to the atomization of fuel sprays of the solid-injection type. The fuel leaves the nozzle as a solid column, is ruffled and then torn into small, irregular ligaments by the action of the air. These ligaments are then quickly broken up into drops by the surface tension of the fuel. The photomicrographs also show that the dispersion of a fuel spray at a given distance from the nozzle increases with an increase in the jet velocity or an increase in the air density. The first portions of fuel sprays injected from an automatic injection valve into air at atmospheric density have a much greater dispersion than the later portions, but this difference decreases rapidly as the air density is increased.

  10. Modeling evaporation effects in conditional moment closure for spray autoignition

    NASA Astrophysics Data System (ADS)

    Borghesi, Giulio; Mastorakos, Epaminondas; Devaud, Cécile B.; Bilger, Robert W.

    2011-10-01

    Simulations of an n-heptane spray autoigniting under conditions relevant to a diesel engine are performed using two-dimensional, first-order conditional moment closure (CMC) with full treatment of spray terms in the mixture fraction variance and CMC equations. The conditional evaporation term in the CMC equations is closed assuming interphase exchange to occur at the droplet saturation mixture fraction values only. Modeling of the unclosed terms in the mixture fraction variance equation is done accordingly. Comparison with experimental data for a range of ambient oxygen concentrations shows that the ignition delay is overpredicted. The trend of increasing ignition delay with decreasing oxygen concentration, however, is correctly captured. Good agreement is found between the computed and measured flame lift-off height for all conditions investigated. Analysis of source terms in the CMC temperature equation reveals that a convective-reactive balance sets in at the flame base, with spatial diffusion terms being important, but not as important as in lifted jet flames in cold air. Inclusion of droplet terms in the governing equations is found to affect the mixture fraction variance field in the region where evaporation is the strongest, and to slightly increase the ignition delay time due to the cooling associated with the evaporation. Both flame propagation and stabilization mechanisms, however, remain unaffected.

  11. Computations of spray, fuel-air mixing, and combustion in a lean-premixed-prevaporized combustor

    NASA Technical Reports Server (NTRS)

    Dasgupta, A.; Li, Z.; Shih, T. I.-P.; Kundu, K.; Deur, J. M.

    1993-01-01

    A code was developed for computing the multidimensional flow, spray, combustion, and pollutant formation inside gas turbine combustors. The code developed is based on a Lagrangian-Eulerian formulation and utilizes an implicit finite-volume method. The focus of this paper is on the spray part of the code (both formulation and algorithm), and a number of issues related to the computation of sprays and fuel-air mixing in a lean-premixed-prevaporized combustor. The issues addressed include: (1) how grid spacings affect the diffusion of evaporated fuel, and (2) how spurious modes can arise through modelling of the spray in the Lagrangian computations. An upwind interpolation scheme is proposed to account for some effects of grid spacing on the artificial diffusion of the evaporated fuel. Also, some guidelines are presented to minimize errors associated with the spurious modes.

  12. A Three-Dimensional Model of Spray Evaporation in Gas Turbine Combustors.

    DTIC Science & Technology

    1980-04-01

    particle diameter D Rosin - Rammler mean diameter L Latent heat of evaporation m Mass m Mass flowrat e n Rosin - Rammler spread par.meter Nu Nusselt...spray leaving the atomiser obeys a Rosin - Rammler size distribution. In this model, the mass fraction of fuel having a droplet diameter greater than D is...given as: Tn. (25) where D is the Rosin - Rammler mean diameter and n is the spread parameter. For this study a value 50 microns was chosen for and the

  13. Fuel evaporation rate control system for a direct fuel injection type internal combustion engine

    SciTech Connect

    Sasaki, S.

    1987-05-26

    A fuel evaporation rate control system is described for a direct fuel injection type spark ignition internal combustion engine including a cylinder, a piston reciprocally movable in the cylinder, a concave wall portion located in the top of the piston to define a combustion chamber. The wall portion has a front surface facing the inside of the piston. Means directly inject fuel into the combustion chamber onto the front surface of the combustion chamber wall such that the fuel adhering onto the combustion chamber wall is evaporated by heat from the wall to generate a combustible mixture gas. The system comprises: an oil path for supplying oil to the engine; and a nozzle means connected to the oil path for spraying a cooling oil jet onto the back surface of the combustion chamber wall so as to control the combustion chamber wall temperature for limiting the evaporation rate of the fuel adhering onto the front surface of the combustion chamber wall. The wall has a heat insulating structure and the nozzle means are located below the piston.

  14. The structure of evaporating and combusting sprays: Measurements and predictions

    NASA Technical Reports Server (NTRS)

    Shuen, J. S.; Solomon, A. S. P.; Faeth, G. M.

    1984-01-01

    An apparatus developed, to allow observations of monodisperse sprays, consists of a methane-fueled turbulent jet diffusion flame with monodisperse methanol drops injected at the burner exit. Mean and fluctuating-phase velocities, drop sizes, drop-mass fluxes and mean-gas temperatures were measured. Initial drop diameters of 100 and 180 microns are being considered in order to vary drop penetration in the flow and effects of turbulent dispersion. Baseline tests of the burner flame with no drops present were also conducted. Calibration tests, needed to establish methods for predicting drop transport, involve drops supported in the post-flame region of a flat-flame burner operated at various mixture ratios. Spray models which are being evaluated include: (1) locally homogeneous flow (LFH) analysis, (2) deterministic separated flow (DSF) analysis and (3) stochastic separated flow (SSF) analysis.

  15. Structure of evaporating and combusting sprays: measurements and predictions

    SciTech Connect

    Shuen, J.S.; Solomon, A.S.P.; Faeth, G.M.

    1984-07-01

    An apparatus developed, to allow observations of monodisperse sprays, consists of a methane-fueled turbulent jet diffusion flame with monodisperse methanol drops injected at the burner exit. Mean and fluctuating-phase velocities, drop sizes, drop-mass fluxes and mean-gas temperatures were measured. Initial drop diameters of 100 and 180 microns are being considered in order to vary drop penetration in the flow and effects of turbulent dispersion. Baseline tests of the burner flame with no drops present were also conducted. Calibration tests, needed to establish methods for predicting drop transport, involve drops supported in the post-flame region of a flat-flame burner operated at various mixture ratios. Spray models which are being evaluated include: (1) locally homogeneous flow (LFH) analysis, (2) deterministic separated flow (DSF) analysis and (3) stochastic separated flow (SSF) analysis.

  16. Analysis of polydisperse fuel spray flame

    NASA Astrophysics Data System (ADS)

    Nave, Ophir; Lehavi, Yaron; Ajadi, Suraju; Gol'dshtein, Vladimir

    2017-02-01

    In this paper we analyzed the model of polydisperse fuel spray flame by using the sectional approach to describe the droplet-droplet interaction within the spray. The radii of the droplets are described by a probability density function. Our numerical simulations include a comparative analysis between three empirical droplet size distributions: the Rosin-Rammler distribution, the log-normal distribution and the Nakiyama-Tanasawa distribution. The log-normal distribution was found to produce a reasonable approximation to both the number and volume size distribution function. In addition our comparative analysis includes the application of the homotopy analysis method which yields convergent solutions for all values of the relevant parameters. We compared the above results to experimental fuel spray data such as {it{Tetralin}}, n-{it{Decane}}, and n-{it{Heptane}}.

  17. A theoretical and experimental study of turbulent evaporating sprays

    NASA Technical Reports Server (NTRS)

    Solomon, A. S. P.; Shuen, J. S.; Zhang, Q. F.; Faeth, G. M.

    1984-01-01

    Measurements and analysis limited to the dilute portions of turbulent evaporating sprays, injected into a still air environment were completed. Mean and fluctuating velocities and Reynolds stress were measured in the continuous phase. Liquid phase measurements included liquid mass fluxes, drop sizes and drop size and velocity correlation. Initial conditions needed for model evaluation were measured at a location as close to the injector exit as possible. The test sprays showed significant effects of slip and turbulent dispersion of the discrete phase. The measurements were used to evaluate three typical models of these processes: (1) a locally homogeneous flow (LHF) model, where slip between the phases were neglected; (2) a deterministic separated flow (DSF) model, where slip was considered but effects of drop dispersion by turbulence were ignored; and (3) a stochastic separated flow (SSF) model, where effects of interphase slip and turbulent dispersion were considered using random-walk computations for drop motion. For all three models, a k-epsilon model as used to find the properties of the continuous phase. The LHF and DSF models did not provide very satisfactory predictions for the present measurements. In contrast, the SSF model performed reasonably well--with no modifications in the prescription of eddy properties from its original calibration.

  18. Comparison of Global Sizing Velocimetry and Phase Doppler Anemometry measurements of alternative jet fuel sprays

    NASA Astrophysics Data System (ADS)

    Sadr, Reza; Kannaiyan, Kumaran

    2013-11-01

    Atomization plays a crucial precursor role in liquid fuel combustion that directly affects the evaporation, mixing, and emission levels. Laser diagnostic techniques are often used to study the spray characteristics of liquid fuels. The objective of this work is to compare the spray measurements of Gas-to Liquid (GTL) jet fuels obtained using Global Sizing Velocimetry (GSV) and Phase Doppler Anemometry (PDA) techniques at global and local levels, respectively. The chemical and physical properties of GTL fuels are different from conventional jet fuels, owing to the difference in their production methodology. In this work, the experimental facility, the measurement techniques, and spray characteristics of two different GTL fuels are discussed and compared with those of Jet A-1 fuel. Results clearly demonstrate that although the global measurement gives an overall picture of the spray, fine details are obtained only through local measurements and complement in gaining more inferences into the spray characteristics. The results also show a close similarity in spray characteristics between GTL and Jet A-1 fuels. Funded by Qatar Science and Technology Park.

  19. High Speed Imaging of Diesel Fuel Sprays

    NASA Astrophysics Data System (ADS)

    Jackson, Ja'kira; Bittle, Joshua

    2016-11-01

    Fuel sprays primarily serve as methods for fuel distribution, fuel/air mixing, and atomization. In this research, a constant pressure flow rig vessel is being tested at various pressures and temperatures using n-heptane. The experiment requires two imaging techniques: color Schlieren and Mie-scatter. Schlieren captures density gradients in a spray which includes both liquid and vapor phases while Mie-scatter is only sensitive to the liquid phase of the fuel spray. Essentially, studies are mainly focused on extracting the liquid boundary from the Schlieren to possibly eliminate the need for acquiring the Mie-Scatter technique. Four test conditions (combination of low and high pressure and temperatures) are used in the application to attempt to find the liquid boundary independent of the Mie-scatter technique. In this pursuit the following methods were used: a color threshold, a value threshold, and the time variation in color. All methods provided some indication of the liquid region but none were able to capture the full liquid boundary as obtained by the Mie-scatter results. Funding from NSF REU site Grant EEC 1358991 is greatly appreciated.

  20. Efficiency of using solid wood fuels in maple syrup evaporators

    Treesearch

    Lawrence D. Garrett

    1981-01-01

    A study of commercial, wood-fired evaporators revealed that normal expected thermal efficiencies are between 35 and 50 percent. The moisture content and quality of wood fuels used and the design and method of firing the evaporator are critical in determining evaporator efficiency and the economic implications of using wood.

  1. Experimental study on spray characteristics of alternate jet fuels using Phase Doppler Anemometry

    NASA Astrophysics Data System (ADS)

    Kannaiyan, Kumaran; Sadr, Reza

    2013-11-01

    Gas-to-Liquid (GTL) fuels have gained global attention due to their cleaner combustion characteristics. The chemical and physical properties of GTL jet fuels are different from conventional jet fuels owing to the difference in their production methodology. It is important to study the spray characteristics of GTL jet fuels as the change of physical properties can affect atomization, mixing, evaporation and combustion process, ultimately affecting emission process. In this work, spray characteristics of two GTL synthetic jet fuels are studied using a pressure-swirl nozzle at different injection pressures and atmospheric ambient condition. Phase Doppler Anemometry (PDA) measurements of droplet size and velocity are compared with those of regular Jet A-1 fuel at several axial and radial locations downstream of the nozzle exit. Experimental results show that although the GTL fuels have different physical properties such as viscosity, density, and surface tension, among each other the resultant change in the spray characteristics is insignificant. Furthermore, the presented results show that GTL fuel spray characteristics exhibit close similarity to those of Jet A-1 fuel. Funded by Qatar Science and Technology Park.

  2. Modeling of turbulence effects on the heat and mass transfer of evaporating sprays

    NASA Astrophysics Data System (ADS)

    Madhanabharatam, Balasubramanyam

    A large diversity of two-phase gas-liquid flows of both scientific and practical interest involves the evaporation of near spherical liquid droplets in high temperature turbulent environments. Current numerical modeling approaches are predominantly focused towards the effects of continuous phase (gas phase) turbulence on the evaporation rates of liquid fuel sprays during the evaporation process, failing to account for the inherent turbulence present in the dispersed phase (liquid phase), due to the injection of sprays at high velocities. Existing models accounting for internal turbulence effects use Direct Numerical Simulations and Large Eddy Simulations that are computationally intensive. This research provides an alternative phenomenological approach of modeling droplet internal turbulence effects through the mass and heat transfer between the droplet surface and the external gas phase within a thin film inside the droplet. This finite conductivity (F-C) model was based on the two-temperature film theory, where the turbulence characteristics of the droplet are used to estimate the effective thermal diffusivity (alphaeff) within the droplet phase. The alphaeff is estimated from the physical properties of the flow within the droplet rather than from a 'curve-fit' as done conventionally. The results of the one-way coupled study indicated that the equilibrium drop temperature predictions were higher than calculations by the infinite conductivity (I-C) model. The liquid internal turbulence has a considerable effect on the diffusivity in the primary atomization regime. The thermal boundary layer was found to be substantially thick initially, decreasing quickly to a small value, exhibiting a reasonable physical trend. The two-way coupled studies (CFD) indicated that the F-C model, slowed down the evaporation process, produced larger droplets and longer tip penetration lengths during the initial stages of injection. For a jet in a supersonic cross-flow, results indicated

  3. Design Optimization of Liquid Fueled High Velocity Oxy- Fuel Thermal Spraying Technique for Durable Coating for Fossil Power Systems

    SciTech Connect

    Choudhuri, Ahsan; Love, Norman

    2016-11-04

    High-velocity oxy–fuel (HVOF) thermal spraying was developed in 1930 and has been commercially available for twenty-five years. HVOF thermal spraying has several benefits over the more conventional plasma spray technique including a faster deposition rate which leads to quicker turn-around, with more durable coatings and higher bond strength, hardness and wear resistance due to a homogeneous distribution of the sprayed particles. HVOF thermal spraying is frequently used in engineering to deposit cermets, metallic alloys, composites and polymers, to enhance product life and performance. HVOF thermal spraying system is a highly promising technique for applying durable coatings on structural materials for corrosive and high temperature environments in advanced ultra-supercritical coal- fired (AUSC) boilers, steam turbines and gas turbines. HVOF thermal spraying is the preferred method for producing coatings with low porosity and high adhesion. HVOF thermal spray process has been shown to be one of the most efficient techniques to deposit high performance coatings at moderate cost. Variables affecting the deposit formation and coating properties include hardware characteristics such as nozzle geometry and spraying distance and process parameters such as equivalence ratio, gas flow density, and powder feedstock. In the spray process, the powder particles experience very high speeds combined with fast heating to the powder material melting point or above. This high temperature causes evaporation of the powder, dissolution, and phase transformations. Due to the complex nature of the HVOF technique, the control and optimization of the process is difficult. In general, good coating quality with suitable properties and required performance for specific applications is the goal in producing thermal spray coatings. In order to reach this goal, a deeper understanding of the spray process as a whole is needed. Although many researchers studied commercial HVOF thermal spray

  4. Spark Ignition of Monodisperse Fuel Sprays. Ph.D. Thesis

    NASA Technical Reports Server (NTRS)

    Danis, Allen M.; Cernansky, Nicholas P.; Namer, Izak

    1987-01-01

    A study of spark ignition energy requirements was conducted with a monodisperse spray system allowing independent control of droplet size, equivalent ratio, and fuel type. Minimum ignition energies were measured for n-heptane and methanol sprays characterized at the spark gap in terms of droplet diameter, equivalence ratio (number density) and extent of prevaporization. In addition to sprays, minimum ignition energies were measured for completely prevaporized mixtures of the same fuels over a range of equivalence ratios to provide data at the lower limit of droplet size. Results showed that spray ignition was enhanced with decreasing droplet size and increasing equivalence ratio over the ranges of the parameters studied. By comparing spray and prevaporized ignition results, the existence of an optimum droplet size for ignition was indicated for both fuels. Fuel volatility was seen to be a critical factor in spray ignition. The spray ignition results were analyzed using two different empirical ignition models for quiescent mixtures. Both models accurately predicted the experimental ignition energies for the majority of the spray conditions. Spray ignition was observed to be probabilistic in nature, and ignition was quantified in terms of an ignition frequency for a given spark energy. A model was developed to predict ignition frequencies based on the variation in spark energy and equivalence ratio in the spark gap. The resulting ignition frequency simulations were nearly identical to the experimentally observed values.

  5. Preliminary Tests on the Vaporization of Fuel Sprays

    NASA Technical Reports Server (NTRS)

    Rothrock, A M

    1932-01-01

    High-speed motion pictures were taken of fuel sprays injected into the combustion chamber of the N.A.C.A. combustion apparatus. Three fuels, ethyl alcohol, gasoline, and fuel oil, which differed considerably in volatility were tested. By maintaining the engine temperature below that required for ignition the spray could be studied from soon after the start of injection until 130 crank degrees later. The results show that the sprays vaporize appreciably so that it is possible for the ignition in high speed compression-ignition engines to take place from the vapor phase.

  6. Spray Characterization of Gas-to-Liquid Synthetic Jet Fuels

    NASA Astrophysics Data System (ADS)

    Kannaiyan, Kumaran; Sadr, Reza; GTL jet fuel Consortium Team

    2012-11-01

    Gas-to-Liquid (GTL) Synthetic Paraffinic Kerosene (SPK) fuel obtained from Fischer-Tropsch synthesis has grabbed the global attention due to its cleaner combustion characteristics. GTL fuels are expected to meet the vital qualities such as atomization, combustion and emission characteristics of conventional jet fuels. It is imperative to understand fuel atomization in order to gain insights on the combustion and emission aspects of an alternative fuel. In this work spray characteristics of GTL-SPK, which could be used as a drop-in fuel in aircraft gas turbine engines, is studied. This work outlines the spray experimental facility, the methodology used and the results obtained using two SPK's with different chemical compositions. The spray characteristics, such as droplet size and distribution, are presented at three differential pressures across a simplex nozzle and compared with that of the conventional Jet A-1 fuel. Experimental results clearly show that although the chemical composition is significantly different between SPK's, the spray characteristics are not very different. This could be attributed to the minimal difference in fluid properties between the SPK's. Also, the spray characteristics of SPK's show close resemblance to the spray characteristics of Jet A-1 fuel.

  7. The structure of evaporating and combusting sprays: Measurements and predictions

    NASA Technical Reports Server (NTRS)

    Shuen, J. S.; Solomon, A. S. P.; Faeth, G. M.

    1982-01-01

    An apparatus was constructed to provide measurements in open sprays with no zones of recirculation, in order to provide well-defined conditions for use in evaluating spray models. Measurements were completed in a gas jet, in order to test experimental methods, and are currently in progress for nonevaporating sprays. A locally homogeneous flow (LHF) model where interphase transport rates are assumed to be infinitely fast; a separated flow (SF) model which allows for finite interphase transport rates but neglects effects of turbulent fluctuations on drop motion; and a stochastic SF model which considers effects of turbulent fluctuations on drop motion were evaluated using existing data on particle-laden jets. The LHF model generally overestimates rates of particle dispersion while the SF model underestimates dispersion rates. The stochastic SF flow yield satisfactory predictions except at high particle mass loadings where effects of turbulence modulation may have caused the model to overestimate turbulence levels.

  8. Spray Characterization of Gas-to-Liquid Synthetic Jet Fuels

    NASA Astrophysics Data System (ADS)

    Kannaiyan, Kumaran; Sadr, Reza

    2011-11-01

    In the recent years, development of alternative jet fuels is gaining importance owing to the demand for cleaner combustion. In addition to having energy density that matches those of conventional fuels, alternate jet fuels need to possess vital qualities such as rapid atomization and vaporization, quick re-ignition at high altitude, less emission, and poses ease of handling. The fuel preparatory steps (atomization and vaporization) and mixing in a combustion chamber play a crucial role on the subsequent combustion and emission characteristics. Gas-to-Liquid (GTL) synthetic jet fuel obtained from Fischer-Tropsch synthesis has grabbed the global attention due to its cleaner combustion characteristics as a result of the absence of aromatics and sulphur. As a part of an on-going joint effort between Texas A&M at Qatar (TAMUQ), Rolls-Royce (UK), and German Aerospace Laboratory (DLR), a spray characterization experimental facility is set up at TAMUQ to study the spray characteristics of GTL fuel and highlights the influence of change in fuel composition on the spray characteristics. In this work, spray characteristics such as droplet size, velocity, and distribution of different GTL fuel blends is investigated and compared with the spray characteristics of conventional JetA1 fuel. Supported by Qatar Science and Technology Park, QSTP.

  9. Numerical Modeling of Turbulence Effects within an Evaporating Droplet in Atomizing Sprays

    NASA Technical Reports Server (NTRS)

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

    2006-01-01

    A new approach to account for finite thermal conductivity and turbulence effects within atomizing liquid sprays is presented in this paper. The model is an extension of the T-blob and T-TAB atomization/spray model of Trinh and Chen (2005). This finite conductivity model is based on the two-temperature film theory, where the turbulence characteristics of the droplet are used to estimate the effective thermal diffhsivity within the droplet phase. Both one-way and two-way coupled calculations were performed to investigate the performance of this model. The current evaporation model is incorporated into the T-blob atomization model of Trinh and Chen (2005) and implemented in an existing CFD Eulerian-Lagrangian two-way coupling numerical scheme. Validation studies were carried out by comparing with available evaporating atomization spray experimental data in terms of jet penetration, temperature field, and droplet SMD distribution within the spray. Validation results indicate the superiority of the finite-conductivity model in low speed parallel flow evaporating spray.

  10. The spray contribution to net evaporation from the sea: A review of recent progress

    NASA Astrophysics Data System (ADS)

    Andreas, Edgar L.; Edson, James B.; Monahan, Edward C.; Rouault, Mathieu P.; Smith, Stuart D.

    1995-01-01

    The part that sea spray plays in the air-sea transfer of heat and moisture has been a controversial question for the last two decades. With general circulation models (GCMs) suggesting that perturbations in the Earth's surface heat budget of only a few W m-2 can initiate major climatic variations, it is crucial that we identify and quantify all the terms in that heat budget. Thus, here we review recent work on how sea spray contributes to the sea surface heat and moisture budgets. In the presence of spray, the near-surface atmosphere is characterized by a droplet evaporation layer (DEL) with a height that scales with the significant-wave amplitude. The majority of spray transfer processes occur within this layer. As a result, the DEL is cooler and more moist than the atmospheric surface layer would be under identical conditions but without the spray. Also, because the spray in the DEL provides elevated sources and sinks for heat and moisture, the vertical heat fluxes are no longer constant with height. We use Eulerian and Lagrangian models and a simple analytical model to study the processes important in spray droplet dispersion and evaporation within this DEL. These models all point to the conclusion that, in high winds (above about 15 m/s), sea spray begins to contribute significantly to the air-sea fluxes of heat and moisture. For example, we estimate that, in a 20-m/s wind, with an air temperature of 20°C, a sea surface temperature of 22°C, and a relative humidity of 80%, the latent and sensible heat fluxes resulting from the spray alone will have magnitudes of order 150 and 15 W/m2, respectively, in the DEL. Finally, we speculate on what fraction of these fluxes rise out of the DEL and, thus, become available to the entire marine boundary layer.

  11. Computational sensitivity study of spray dispersion and mixing on the fuel properties in a gas turbine combustor

    NASA Astrophysics Data System (ADS)

    Grosshans, Holger; Cao, Le; Fuchs, Laszlo; Szász, Robert-Zoltán

    2017-04-01

    A swirl stabilized gas turbine burner has been simulated in order to assess the effects of the fuel properties on spray dispersion and fuel-air mixing. The properties under consideration include fuel surface tension, viscosity and density. The turbulence of the gas phase is modeled applying the methodology of large eddy simulation whereas the dispersed liquid phase is described by Lagrangian particle tracking. The exchange of mass, momentum and energy between the two phases is accounted for by two-way coupling. Bag and stripping breakup regimes are considered for secondary droplet breakup, using the Reitz-Diwakar and the Taylor analogy breakup models. Moreover, a model for droplet evaporation is included. The results reveal a high sensitivity of the spray structure to variations of all investigated parameters. In particular, a decrease in the surface tension or the fuel viscosity, or an increase in the fuel density, lead to less stable liquid structures. As a consequence, smaller droplets are generated and the overall spray surface area increases, leading to faster evaporation and mixing. Furthermore, with the trajectories of the small droplets being strongly influenced by aerodynamic forces (and less by their own inertia), the spray is more affected by the turbulent structures of the gaseous phase and the spray dispersion is enhanced.

  12. Some Characteristics of Fuel Sprays at Low-injection Pressures

    NASA Technical Reports Server (NTRS)

    Rothrock, A M; Waldron, C D

    1931-01-01

    This report presents the results of tests conducted at the Langley Memorial Aeronautical Laboratory, Langley Field, Va., to determine some of the characteristics of the fuel sprays obtained from an 0.008-inch and a 0.020-inch open nozzle when injection pressures from 100 to 500 pounds per square inch were used. Fuel oil and gasoline were injected into air at densities of atmospheric land 0.325 pound per cubic foot. It was found that the penetration rate at these low pressures was about the same as the rate obtained with higher pressures. Spray cone-angles were small and individual oil drops were visible in all the sprays. Gasoline and fuel oil sprays had similar characteristics.

  13. Computational Studies of Evaporating Sprays in a Shear Layer

    DTIC Science & Technology

    1988-10-21

    utilized for calculating their trajectories, temperatures and evaporation rates. Typically, a Rosin - Rammler size distribution function was employed for...Two distribution functions ( the binomial and the Rosin - Rammler ) were employed to characterize the droplet sizes at the inlet. For the binomial...1.0 (111.24) As IL -4 c, the binomial distribution function approaches the normal (Gaussian) distribution function. 53 The Rosin - Rammler distribution

  14. Eulerian CFD modeling and X-ray validation of non-evaporating diesel spray

    NASA Astrophysics Data System (ADS)

    Xue, Qingluan; Som, Sibendu; Quan, Shaoping; Pomraning, Eric; Senecal, P. K.

    2013-11-01

    This work implemented an Eulerian single-phase approach by Vallet et al. into CFD software (Convergent) for diesel spray simulations. This Eulerian approach considers liquid and gas phase as a complex mixture of a single flow with a highly variable density to describe the near nozzle dense sprays. The mean density is obtained form the Favre-averaged liquid mass fraction. Liquid mass fraction is transported with a model for the turbulent liquid diffusion flux into the gas. A mean gradient-based model is employed for the diffusion flux in this study. A non-evaporating diesel spray was measured using x-ray radiography at Argonne National Laboratory. The quantitative and time-resolved data of liquid penetration and mass distribution in the dense spray region are used to validate this approach. The different turbulence models are also used for the simulations. The comparison between the simulated results and experimental data and the turbulence model effect are discussed.

  15. Comprehensive Fuel Spray Modeling and Impacts on Chamber Acoustics in Combustion Dynamics Simulations

    DTIC Science & Technology

    2013-05-01

    susceptible to thermoacoustic instabilities. Since the LDI engine is operated at fuel-lean conditions, the chemical ki- netics and flame surface are...iments of reacting sprays are used to characterize thermoacoustic instabilities in the LDI gas turbine combustor. Fuel Spray Modeling The fuel spray model

  16. Evaporation and Deposition Coverage Area of Droplets Containing Insecticides and Spray Additives on Hydrophilic, Hydrophobic and Crabapple Leaf Surfaces

    USDA-ARS?s Scientific Manuscript database

    The efficiency of foliar spray applications is influenced by the evaporation and residual pattern of pesticide droplets on targets. Evaporation time and maximal coverage area of a single droplet sizing from 246 to 886 µm at relative humidity (RH) ranging from 30 to 90% were measured with sequential ...

  17. High-pressure combustion of binary fuel sprays

    NASA Technical Reports Server (NTRS)

    Mikami, Masato; Kono, Michikata; Sato, Jun'ichi; Dietrich, Daniel L.; Williams, Forman A.

    1995-01-01

    The ultimate objective of this study is to obtain fundamental information relevant to combustion processes that occur in fuel sprays of practical interest at high pressures in internal combustion engines. Since practical fuels are multicomponent and derived from petroleum, the present work involves the model alkane mixture of n-heptane and n-hexadecane. Since burning droplets in sprays can interact with each other, the present work involves investigation of the effects of this interaction on flame shapes and droplet burning times. The small droplets in practical combustion chambers are not significantly influenced by buoyancy. Since such small droplets are difficult to study experimentally, the present work takes advantage of microgravity to lessen buoyancy and enable information about droplet interactions to be obtained by studying larger droplets. The results are intended to provide fundamental understanding that can be used in improving descriptions of practical spray combustion.

  18. Measuring the Nonuniform Evaporation Dynamics of Sprayed Sessile Microdroplets with Quantitative Phase Imaging.

    PubMed

    Edwards, Chris; Arbabi, Amir; Bhaduri, Basanta; Wang, Xiaozhen; Ganti, Raman; Yunker, Peter J; Yodh, Arjun G; Popescu, Gabriel; Goddard, Lynford L

    2015-10-13

    We demonstrate real-time quantitative phase imaging as a new optical approach for measuring the evaporation dynamics of sessile microdroplets. Quantitative phase images of various droplets were captured during evaporation. The images enabled us to generate time-resolved three-dimensional topographic profiles of droplet shape with nanometer accuracy and, without any assumptions about droplet geometry, to directly measure important physical parameters that characterize surface wetting processes. Specifically, the time-dependent variation of the droplet height, volume, contact radius, contact angle distribution along the droplet's perimeter, and mass flux density for two different surface preparations are reported. The studies clearly demonstrate three phases of evaporation reported previously: pinned, depinned, and drying modes; the studies also reveal instances of partial pinning. Finally, the apparatus is employed to investigate the cooperative evaporation of the sprayed droplets. We observe and explain the neighbor-induced reduction in evaporation rate, that is, as compared to predictions for isolated droplets. In the future, the new experimental methods should stimulate the exploration of colloidal particle dynamics on the gas-liquid-solid interface.

  19. A fundamental study of liquid spray evaporation at a heated surface

    NASA Technical Reports Server (NTRS)

    Wierum, F. A.

    1979-01-01

    The influence of feedwater temperature and the influence of pulsing nozzle flow on the heat transfer characteristics in the spray evaporative cooling process were investigated. A commercial water circulation heater was installed in the feedwater line between the supply reservoir and the nozzle. A pass through the heater provided water at temperatures up to 50 C at the nozzle; higher temperatures were obtained by multiple heater passes. A thermocouple installed in the water line just upstream of the nozzle provided a measure of the feedwater temperature. Initial tests were run with belljar exhaust orifice number two which provided a pressure in a range about 7mm Hg abs. The feedwater temperature was heated to a temperature of 45 C. Results indicate that for a given system operating pressure, there is an upper limit on the feedwater temperature above which the spray will flash to vapor before hitting the surface to be cooled.

  20. Measurement of vapor/liquid distributions in a binary-component fuel spray using laser imaging of droplet scattering and vapor absorption

    NASA Astrophysics Data System (ADS)

    Li, Shiyan; Zhang, Yuyin; Wu, Shenqi; Xu, Bin

    2014-08-01

    Fuel volatility has a great effect on its evaporation processes and the mixture formation and thus combustion and emissions formation processes in internal combustion engines. To date, however, instead of the actual gasoline or diesel fuel, many researchers have been using single-component fuel in their studies, because the composition of the former is too complicated to understand the real physics behind the evaporation and combustion characteristics. Several research groups have reported their results on droplets evaporation in a spray of multi-component fuel, carried out both numerically and experimentally. However, there are plenty of difficulties in quantitative determination of vapor concentration and droplet distributions of each component in a multicomponent fuel spray. In this study, to determine the vapor phase concentration and droplet distributions in an evaporating binary component fuel spray, a laser diagnostics based on laser extinction by droplet scattering and vapor absorption was developed. In practice, measurements of the vapor concentration distributions of the lower (n-tridencane) and higher (n-octane) volatility components in the binary component fuel sprays have been carried out at ambient temperatures of 473K and 573K, by substituting p-xylene for noctane or α-methylnaphthalene for n-tridecane. p-Xylene and α-methylnaphthalene were selected as the substitutes is because they have strong absorption band near 266nm and transparent near 532nm and, their thermo-physical properties are similar to those of the original component. As a demonstration experiment, vapor/liquid distribution of the lower boiling point (LBP) and higher boiling point (HBP) components in the binary component fuel spray have been obtained.

  1. Effects of fuel evaporation on the octane number of methanol-gasoline blended fuels

    SciTech Connect

    Moran, D.P.

    1994-10-01

    A procedure is described to estimate the influence of end-gas temperature on Octane Number. Blending methanol with gasoline is known to cause a disproportionate increase in Research Octane Number, and this is found to correlate well with the evaporative cooling characteristics of these blends. The Motor Octane Number test eliminates evaporative effects, and the difference between the two test methods is evaluated in terms of evaporative cooling. It is concluded that the high heat of vaporization of methanol is largely responsible for the excellent RON performance of methanol-gasoline blended fuels. 17 refs., 11 refs., 2 tabs.

  2. Air/fuel ratio visualization in a diesel spray

    NASA Astrophysics Data System (ADS)

    Carabell, Kevin David

    1993-01-01

    To investigate some features of high pressure diesel spray ignition, we have applied a newly developed planar imaging system to a spray in an engine-fed combustion bomb. The bomb is designed to give flow characteristics similar to those in a direct injection diesel engine yet provide nearly unlimited optical access. A high pressure electronic unit injector system with on-line manually adjustable main and pilot injection features was used. The primary scalar of interest was the local air/fuel ratio, particularly near the spray plumes. To make this measurement quantitative, we have developed a calibration LIF technique. The development of this technique is the key contribution of this dissertation. The air/fuel ratio measurement was made using biacetyl as a seed in the air inlet to the engine. When probed by a tripled Nd:YAG laser the biacetyl fluoresces, with a signal proportional to the local biacetyl concentration. This feature of biacetyl enables the fluorescent signal to be used as as indicator of local fuel vapor concentration. The biacetyl partial pressure was carefully controlled, enabling estimates of the local concentration of air and the approximate local stoichiometry in the fuel spray. The results indicate that the image quality generated with this method is sufficient for generating air/fuel ratio contours. The processes during the ignition delay have a marked effect on ignition and the subsequent burn. These processes, vaporization and pre-flame kinetics, very much depend on the mixing of the air and fuel. This study has shown that poor mixing and over-mixing of the air and fuel will directly affect the type of ignition. An optimal mixing arrangement exists and depends on the swirl ratio in the engine, the number of holes in the fuel injector and the distribution of fuel into a pilot and main injection. If a short delay and a diffusion burn is desired, the best mixing parameters among those surveyed would be a high swirl ratio, a 4-hole nozzle and a

  3. Measurement of fuel spray vaporisation by laser techniques

    NASA Technical Reports Server (NTRS)

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

    1980-01-01

    Comparison of fuel spray structures in heated and in cold environments is made by using a new laser tomographic technique and laser anemometry. The tomography technique is shown to give accurate and rapid 'point' measurements of droplet sizes and concentrations. Experimental results show acceleration of droplets to the local gas velocity, preferential vaporisation of the smallest droplets and the dispersion of droplets by the turbulence.

  4. Vacuum plasma spray applications on liquid fuel rocket engines

    NASA Technical Reports Server (NTRS)

    Mckechnie, T. N.; Zimmerman, F. R.; Bryant, M. A.

    1992-01-01

    The vacuum plasma spray process (VPS) has been developed by NASA and Rocketdyne for a variety of applications on liquid fuel rocket engines, including the Space Shuttle Main Engine. These applications encompass thermal barrier coatings which are thermal shock resistant for turbopump blades and nozzles; bond coatings for cryogenic titanium components; wear resistant coatings and materials; high conductivity copper, NaRloy-Z, combustion chamber liners, and structural nickel base material, Inconel 718, for nozzle and combustion chamber support jackets.

  5. Vacuum plasma spray applications on liquid fuel rocket engines

    NASA Astrophysics Data System (ADS)

    McKechnie, T. N.; Zimmerman, F. R.; Bryant, M. A.

    1992-07-01

    The vacuum plasma spray process (VPS) has been developed by NASA and Rocketdyne for a variety of applications on liquid fuel rocket engines, including the Space Shuttle Main Engine. These applications encompass thermal barrier coatings which are thermal shock resistant for turbopump blades and nozzles; bond coatings for cryogenic titanium components; wear resistant coatings and materials; high conductivity copper, NaRloy-Z, combustion chamber liners, and structural nickel base material, Inconel 718, for nozzle and combustion chamber support jackets.

  6. Experimental investigation on the characteristics of supersonic fuel spray and configurations of induced shock waves

    PubMed Central

    Wang, Yong; Yu, Yu-song; Li, Guo-xiu; Jia, Tao-ming

    2017-01-01

    The macro characteristics and configurations of induced shock waves of the supersonic sprays are investigated by experimental methods. Visualization study of spray shape is carried out with the high-speed camera. The macro characteristics including spray tip penetration, velocity of spray tip and spray angle are analyzed. The configurations of shock waves are investigated by Schlieren technique. For supersonic sprays, the concept of spray front angle is presented. Effects of Mach number of spray on the spray front angle are investigated. The results show that the shape of spray tip is similar to blunt body when fuel spray is at transonic region. If spray entered the supersonic region, the oblique shock waves are induced instead of normal shock wave. With the velocity of spray increasing, the spray front angle and shock wave angle are increased. The tip region of the supersonic fuel spray is commonly formed a cone. Mean droplet diameter of fuel spray is measured using Malvern’s Spraytec. Then the mean droplet diameter results are compared with three popular empirical models (Hiroyasu’s, Varde’s and Merrigton’s model). It is found that the Merrigton’s model shows a relative good correlation between models and experimental results. Finally, exponent of injection velocity in the Merrigton’s model is fitted with experimental results. PMID:28054555

  7. Experimental investigation on the characteristics of supersonic fuel spray and configurations of induced shock waves

    NASA Astrophysics Data System (ADS)

    Wang, Yong; Yu, Yu-Song; Li, Guo-Xiu; Jia, Tao-Ming

    2017-01-01

    The macro characteristics and configurations of induced shock waves of the supersonic sprays are investigated by experimental methods. Visualization study of spray shape is carried out with the high-speed camera. The macro characteristics including spray tip penetration, velocity of spray tip and spray angle are analyzed. The configurations of shock waves are investigated by Schlieren technique. For supersonic sprays, the concept of spray front angle is presented. Effects of Mach number of spray on the spray front angle are investigated. The results show that the shape of spray tip is similar to blunt body when fuel spray is at transonic region. If spray entered the supersonic region, the oblique shock waves are induced instead of normal shock wave. With the velocity of spray increasing, the spray front angle and shock wave angle are increased. The tip region of the supersonic fuel spray is commonly formed a cone. Mean droplet diameter of fuel spray is measured using Malvern’s Spraytec. Then the mean droplet diameter results are compared with three popular empirical models (Hiroyasu’s, Varde’s and Merrigton’s model). It is found that the Merrigton’s model shows a relative good correlation between models and experimental results. Finally, exponent of injection velocity in the Merrigton’s model is fitted with experimental results.

  8. Spray deposition of Nafion membranes: Electrode-supported fuel cells

    NASA Astrophysics Data System (ADS)

    Bayer, Thomas; Pham, Hung Cuong; Sasaki, Kazunari; Lyth, Stephen Matthew

    2016-09-01

    Fuel cells are a key technology for the successful transition towards a hydrogen society. In order to accelerate fuel cell commercialization, improvements in performance are required. Generally, polymer electrolyte membrane fuel cells (PEFCs) are membrane-supported; the electrocatalyst layer is sprayed onto both sides of the membrane, and sandwiched between carbon-based gas diffusion layers (GDLs). In this work we redesign the membrane electrode assembly (MEA) and fabricate an electrode-supported PEFC. First the electrocatalyst layer is sprayed onto the GDL, and then Nafion dispersion is sprayed over the top of this to form a thin membrane. This method has the advantage of simplifying the fabrication process, allowing the fabrication of extremely thin electrolyte layers (down to ∼10 μm in this case), and reducing the amount of ionomer required in the cell. Electrode-supported PEFCs operate at significantly increased power density compared to conventional membrane-supported PEFCs, with a maximum of 581 mW/cm2 at 80 °C (atmospheric pressure, air at the cathode). Impedance spectroscopy confirmed that the origin of the improved performance was an 80% reduction in the membrane resistance due the thinner Nafion layer. This novel fabrication method is a step towards cheaper, thinner, fully printable PEFCs with high power density and efficiency.

  9. Spray sealing: A breakthrough in integral fuel tank sealing technology

    NASA Astrophysics Data System (ADS)

    Richardson, Martin D.; Zadarnowski, J. H.

    1989-11-01

    In a continuing effort to increase readiness, a new approach to sealing integral fuel tanks is being developed. The technique seals potential leak sources by spraying elastomeric materials inside the tank cavity. Laboratory evaluations project an increase in aircraft supportability and reliability, an improved maintainability, decreasing acquisition and life cycle costs. Increased usable fuel volume and lower weight than conventional bladders improve performance. Concept feasibility was demonstrated on sub-scale aircraft fuel tanks. Materials were selected by testing sprayable elastomers in a fuel tank environment. Chemical stability, mechanical properties, and dynamic durability of the elastomer are being evaluated at the laboratory level and in sub-scale and full scale aircraft component fatigue tests. The self sealing capability of sprayable materials is also under development. Ballistic tests show an improved aircraft survivability, due in part to the elastomer's mechanical properties and its ability to damp vibrations. New application equipment, system removal, and repair methods are being investigated.

  10. A Comparison of Fuel Sprays from Several Types of Injection Nozzles

    NASA Technical Reports Server (NTRS)

    Lee, Dana W

    1936-01-01

    This report presents the tests results of a series of tests made of the sprays from 14 fuel injection nozzles of 9 different types, the sprays being injected into air at atmospheric density and at 6 and 14 times atmospheric density. High-speed spark photographs of the sprays from each nozzle at each air density were taken at the rate of 2,000 per second, and from them were obtained the dimensions of the sprays and the rates of spray-tip penetration. The sprays were also injected against plasticine targets placed at different distances from the nozzles, and the impressions made in the plasticine were used as an indication of the distribution of the fuel within the spray. Cross-sectional sketches of the different types of sprays are given showing the relative sizes of the spray cores and envelopes. The characteristics of the sprays are compared and discussed with respect to their application to various types of engines.

  11. A Nonlinear Model for Fuel Atomization in Spray Combustion

    NASA Technical Reports Server (NTRS)

    Liu, Nan-Suey (Technical Monitor); Ibrahim, Essam A.; Sree, Dave

    2003-01-01

    Most gas turbine combustion codes rely on ad-hoc statistical assumptions regarding the outcome of fuel atomization processes. The modeling effort proposed in this project is aimed at developing a realistic model to produce accurate predictions of fuel atomization parameters. The model involves application of the nonlinear stability theory to analyze the instability and subsequent disintegration of the liquid fuel sheet that is produced by fuel injection nozzles in gas turbine combustors. The fuel sheet is atomized into a multiplicity of small drops of large surface area to volume ratio to enhance the evaporation rate and combustion performance. The proposed model will effect predictions of fuel sheet atomization parameters such as drop size, velocity, and orientation as well as sheet penetration depth, breakup time and thickness. These parameters are essential for combustion simulation codes to perform a controlled and optimized design of gas turbine fuel injectors. Optimizing fuel injection processes is crucial to improving combustion efficiency and hence reducing fuel consumption and pollutants emissions.

  12. A Nonlinear Model for Fuel Atomization in Spray Combustion

    NASA Technical Reports Server (NTRS)

    Liu, Nan-Suey (Technical Monitor); Ibrahim, Essam A.; Sree, Dave

    2003-01-01

    Most gas turbine combustion codes rely on ad-hoc statistical assumptions regarding the outcome of fuel atomization processes. The modeling effort proposed in this project is aimed at developing a realistic model to produce accurate predictions of fuel atomization parameters. The model involves application of the nonlinear stability theory to analyze the instability and subsequent disintegration of the liquid fuel sheet that is produced by fuel injection nozzles in gas turbine combustors. The fuel sheet is atomized into a multiplicity of small drops of large surface area to volume ratio to enhance the evaporation rate and combustion performance. The proposed model will effect predictions of fuel sheet atomization parameters such as drop size, velocity, and orientation as well as sheet penetration depth, breakup time and thickness. These parameters are essential for combustion simulation codes to perform a controlled and optimized design of gas turbine fuel injectors. Optimizing fuel injection processes is crucial to improving combustion efficiency and hence reducing fuel consumption and pollutants emissions.

  13. Measurements of Fuel Distribution Within Sprays for Fuel-Injection Engines

    NASA Technical Reports Server (NTRS)

    Lee, Dana W

    1937-01-01

    Two methods were used to measure fuel distribution within sprays from several types of fuel-injection nozzles. A small tube inserted through the wall of an air tight chamber into which the sprays were injected could be moved about inside the chamber. When the pressure was raised to obtain air densities of 6 and 14 atmospheres, some air was forced through the tube and the fuel that was carried with it was separated by absorbent cotton and weighed. Cross sections of sprays from plain, pintle, multiple-orifice, impinging-jets, centrifugal, lip, slit, and annular-orifice nozzles were investigated, at distances of 1, 3, 5, and 7 inches from the nozzles.

  14. Evaporation of multi-component mixtures and shell formation in spray dried droplets

    NASA Astrophysics Data System (ADS)

    Valente, Pedro; Duarte, Íris; Porfirio, Tiago; Temtem, Márcio

    2015-11-01

    Drug particles where the active pharmaceutical ingredient (APIs) is dispersed in a polymer matrix forming an amorphous solid dispersion (ASD) is a commonly used strategy to increase the solubility and dissolution rate of poorly water soluble APIs. However, the formation and stability of an amorphous solid dispersion depends on the polymer/API combination and process conditions to generate it. The focus of the present work is to further develop a numerical tool to predict the formation of ASDs by spray drying solutions of different polymer/API combinations. Specifically, the evaporation of a multi-component droplet is coupled with a diffusion law within the droplet that minimizes the Gibbs free energy of the polymer/API/solvents system, following the Flory-Huggins model. Prior to the shell formation, the evaporation of the solvents is modelled following the simplified approach proposed by Abramzon & Sirignano (1989) which accounts for the varying relative velocity between the droplet and the drying gas. After shell formation, the diffusion of the solvents across the porous shell starkly modifies the evaporative dynamics.

  15. The Effects of Fuel and Cylinder Gas Densities on the Characteristics of Fuel Sprays for Oil Engines

    NASA Technical Reports Server (NTRS)

    Joachim, W F; Beardsley, Edward G

    1928-01-01

    This investigation was conducted as a part of a general research on fuel-injection engines for aircraft. The purpose of the investigation was to determine the effects of fuel and cylinder gas densities with several characteristics of fuel sprays for oil engines. The start, growth, and cut-off of single fuel sprays produced by automatic injection valves were recorded on photographic film by means of special high-speed motion-picture apparatus. This equipment, which has been described in previous reports, is capable of taking twenty-five consecutive pictures of the moving spray at the rate of 4,000 per second. The penetrations of the fuel sprays increased and the cone angles and relative distributions decreased with increase in the specific gravity of the fuel. The density of the gas into which the fuel sprays were injected controlled their penetration. This was the only characteristic of the chamber gas that had a measurable effect upon the fuel sprays. Application of fuel-spray penetration data to the case of an engine, in which the pressure is rising during injection, indicated that fuel sprays may penetrate considerably farther than when injected into a gas at a density equal to that of the gas in an engine cylinder at top center.

  16. Method and apparatus for the automated testing of vehicle fuel evaporation control systems

    SciTech Connect

    Rogers, J.N.; Timmerman, G.

    1993-08-31

    Apparatus is described for testing a vehicle fuel evaporation control system comprising a fuel tank, a fuel vapor collection canister and a canister purge control valve, the apparatus comprising an inert gas source, means for connecting said source to the automobile fuel evaporation control system under test, means for monitoring the flow of said inert gas into said fuel evaporation control system, means for determining the integrity of said canister by detection of the outflow of said inert gas from said canister, and monitoring means connected to the exhaust pipe of the automobile to determine the presence of said inert gas in the engine exhaust.

  17. Photo-ignition of Carbon Nanotube for Ignition of Liquid Fuel Spray and Solid Fuel

    DTIC Science & Technology

    2012-03-01

    photoignition of the gaseous fuel and air mixture showed distributed ignition.10,11 There has been a recent report on the photoignition of graphene ...is scalable, while the application of the photoignition has been demonstrated for small scale fuel spray and simulated solid propellants in this...Sergey Dubin, Alireza Badakhshan, Jabari Farrar, Stephen. A. Danczyk, Richard B. Kaner, “Photothermal Deoxygenation of Graphene Oxide for Patterning

  18. Ion/molecule reaction and ion evaporation in atmospheric pressure spray ionization

    NASA Astrophysics Data System (ADS)

    Hirabayashi, Atsumu; Takada, Yasuaki; Kambara, Hideki; Umemura, Yuta; Ohta, Hitoshi; Ito, Haruhiko; Kuchitsu, Kozo

    1992-12-01

    The positive ions produced in atmospheric pressure spray ionization of ammonia, alanine and sucrose in aqueous solution were detected with a double-focusing mass spectrometer. The relative intensities of the quasi-molecular ions of ammonia, NH+4 (H2O)n (n = 0-3), were found to be proportional to the concentration of the ammonia solution and to increase with increasing distance d between the nozzle tip and the sample aperture of the mass spectrometer; this observation shows that the ammonia molecule is produced by the spray and is protonated at atmospheric pressure by a proton transfer reaction with the hydronium ion and its hydrated clusters. The observed dependences of the relative intensities of the protonated alanine molecules from alanine solution and the cationized sucrose molecules from sucrose solution on d show that some part of these quasi-molecular ions are also produced by the ion/molecule reaction in the gas phase. However, their dependences on the concentration, which are steeper than that in the ammonia case, indicate that a significant proportion of these ions are produced by ion evaporation from a droplet or liquid.

  19. Optical Properties and Radiation-Enhanced Evaporation of Nanofluid Fuels Containing Carbon-Based Nanostructures

    DTIC Science & Technology

    2012-05-29

    Optical Properties and Radiation-Enhanced Evaporation of Nanofluid Fuels Containing Carbon-Based Nanostructures Yanan Gan and Li Qiao* School of...evaporation characteristics of nanofluid fuels with stable suspension of carbon-based nanostructures under radiation absorption in the ultraviolet...visible range. The results show that the evaporation rates of the ethanol-based nanofluids containing multiwalled carbon nanotubes (MWCNTs) or carbon

  20. High Resolution Numerical Simulations of Primary Atomization in Diesel Sprays with Single Component Reference Fuels

    DTIC Science & Technology

    2015-09-01

    ARL-RP-0549 ● SEP 2015 US Army Research Laboratory High Resolution Numerical Simulations of Primary Atomization in Diesel Sprays...0549 ● SEP 2015 US Army Research Laboratory High Resolution Numerical Simulations of Primary Atomization in Diesel Sprays with Single...AND SUBTITLE High Resolution Numerical Simulations of Primary Atomization in Diesel Sprays with Single Component Reference Fuels 5a. CONTRACT NUMBER

  1. Combustion characteristics in the transition region of liquid fuel sprays

    NASA Technical Reports Server (NTRS)

    Cernansky, N. P.; Namer, I.; Tidona, R. J.

    1986-01-01

    A number of important effects have been observed in the droplet size transition region in spray combustion systems. In this region, where the mechanism of flame propagation is transformed from diffusive to premixed dominated combustion, the following effects have been observed: (1) maxima in burning velocity; (2) extension of flammability limits; (3) minima in ignition energy; and (4) minima in NOx formation. A monodisperse aerosol generator has been used to form and deliver a well controlled liquid fuel spray to the combustion test section where measurements of ignition energy have been made. The ignition studies were performed on monodisperse n-heptane sprays at atmospheric pressure over a range of equivalence ratios and droplet diameters. A capacitive discharge spark ignition system was used as the ignition source, providing independent control of spark energy and duration. Preliminary measurements were made to optimize spark duration and spark gap, optimum conditions being those at which the maximum frequency or probability of ignition was observed. Using the optimum electrode spacing and spark duration, the frequency of ignition was determined as a function of spark energy for three overall equivalence ratios (0.6, 0.8, and 1.0) and for initial droplet diameters of 25, 40, 50, 60, and 70 micro m.

  2. Carbon nanotube reinforced aluminum nanocomposite via plasma and high velocity oxy-fuel spray forming.

    PubMed

    Laha, T; Liu, Y; Agarwal, A

    2007-02-01

    Free standing structures of hypereutectic aluminum-23 wt% silicon nanocomposite with multiwalled carbon nanotubes (MWCNT) reinforcement have been successfully fabricated by two different thermal spraying technique viz Plasma Spray Forming (PSF) and High Velocity Oxy-Fuel (HVOF) Spray Forming. Comparative microstructural and mechanical property evaluation of the two thermally spray formed nanocomposites has been carried out. Presence of nanosized grains in the Al-Si alloy matrix and physically intact and undamaged carbon nanotubes were observed in both the nanocomposites. Excellent interfacial bonding between Al alloy matrix and MWCNT was observed. The elastic modulus and hardness of HVOF sprayed nanocomposite is found to be higher than PSF sprayed composites.

  3. The Effect of Fuel Injector Nozzle Configuration on JP-8 Sprays at Diesel Engine Conditions

    DTIC Science & Technology

    2014-10-01

    CFD study was conducted to compare modeling to experimental results. Fuel spray studies investigating liquid and vapor penetrations lengths can be...injectors tested. In addition, a 3D CFD study was conducted to compare modeling to experimental results. Fuel spray studies investigating liquid and...with six fuels including conventional (No. 2 Diesel, JP-8, Jet -A), alternative fuels, and a surrogate with the objective of assessing the performance

  4. Fuel Surrogate Physical Property Effects on Direct Injection Spray and Ignition Behavior

    DTIC Science & Technology

    2015-09-01

    emissions, and spray characteristics to the properties of alternative diesel fuels, such as dimethyl ether ( DME ), biodiesel, and jet fuel, which are... kinetic energy flow rate from the fuel injection (Ėkinetic,injection) as follows: fuel fuelU ρ 1 ∝ (Eq. 5) fuelfuelm ρ∝ (Eq. 6) ( ) fuel...fuelfuelinjectionkinetic UmE ρ 12 , ∝∝  (Eq. 7) 15 UNCLASSIFIED UNCLASSIFIED As indicated by Equation 7, the kinetic energy introduced by the fuel

  5. Characterization of simulated small-droplet fuel sprays

    NASA Technical Reports Server (NTRS)

    Ingebo, R. D.

    1986-01-01

    A two-fluid pneumatic atomizer operating at relatively high liquid and gas pressures produced water sprays that simulated small-droplet clouds of liquid fuel for use in studying vaporization and fuel-air mixing effects on combustor performance and emissions. To characterize the sprays, a scattered-light scanning instrument was developed and measurements of volume median or volume mean diameter, D sub V.5, were correlated with D sub O, W sub w, and W sub n, i.e., orifice diameter, water, and nitrogen gas flow rates, respectively, to give the general expression: D sub v.5 approx. (D sub o sup 0.2) (W sub w sup m) (W sub n sup n), which yields D sub v.5 = 45 (D sub o sup 0.2) (W sub w sup 0.2) (W sub w sup - 1.2). Values of D sub o, W sub w, and W sub n are in centimeters and grams/second, respectively. Farther downstream at an axial distance of 6.7 cm, exponent m increased from 0.2 to 0.4 and exponent n decreased from -1.2 to -1.0 and at a distance of 25 cm downstream of the atomizer, n decreased to -0.8. The increase in exponent m and decrease in exponent n was attributed to a loss of very small droplets from the spray due primarily to vaporization and diffusion effects on clouds of small droplets traveling a distance of 25 cm.

  6. Effect of Fuel Additives on Spray Performance of Alternative Jet Fuels

    NASA Astrophysics Data System (ADS)

    Kannaiyan, Kumaran; Sadr, Reza

    2015-11-01

    Role of alternative fuels on reducing the combustion pollutants is gaining momentum in both land and air transport. Recent studies have shown that addition of nanoscale metal particles as fuel additives to liquid fuels have a positive effect not only on their combustion performance but also in reducing the pollutant formation. However, most of those studies are still in the early stages of investigation with the addition of nanoparticles at low weight percentages. Such an addition can affect the hydrodynamic and thermo-physical properties of the fuel. In this study, the near nozzle spray performance of gas-to-liquid jet fuel with and without the addition of alumina nanoparticles are investigated at macro- and microscopic levels using optical diagnostic techniques. At macroscopic level, the addition of nanoparticles is seen to enhance the sheet breakup process when compared to that of the base fuel. Furthermore, the microscopic spray characteristics such as droplet size and velocity are also found to be affected. Although the addition of nanoscale metal particles at low weight percentages does not affect the bulk fluid properties, the atomization process is found to be affected in the near nozzle region. Funded by Qatar National Research Fund.

  7. Calculation of the two-phase flow in an evaporating spray using an Eulerian-Lagrangian analysis

    NASA Astrophysics Data System (ADS)

    Sabnis, Jayant S.; de Jong, Frederik J.

    1990-01-01

    The two-phase flow in an evaporating spray has been simulated using a combined Eulerian-Lagrangian analysis. This analysis couples a linearized block implicit Navier-Stokes analysis for the gaseous phase with a Lagrangian analysis for the droplet phase, resulting in an efficient scheme for the computation of the poly-dispersed two-phase flow. The motion of the droplet phase is tracked in the coordinate space, resulting in improved computational efficiency, and the inter-phase coupling terms are computed from the instantaneous distribution of the droplets rather than the trajectory information. The effect of the gas phase turbulence on the motion of the droplet phase has also been included in the analysis. The computed results have been compared with experimetnal data available on an evaporating spray with liquid freon.

  8. Investigation of Fuel Oil/Lube Oil Spray Fires On Board Vessels. Volume 3.

    DTIC Science & Technology

    1998-11-01

    U.S. Coast Guard Research and Development Center 1082 Shennecossett Road, Groton, CT 06340-6096 Report No. CG-D-01-99, III Investigation of Fuel ...4. Title and Subtitle Investigation of Fuel Oil/Lube Oil Spray Fires On Board Vessels - Volume Appendix C: LMIS Events and Associated Event Trees...measures (technological advancements as well as safety management systems) for preventing or mitigating the impacts of fuel oil or lube oil spray fires on

  9. Some Effects of Air and Fuel Oil Temperatures on Spray Penetration and Dispersion

    NASA Technical Reports Server (NTRS)

    Gelalles, A G

    1930-01-01

    Presented here are experimental results obtained from a brief investigation of the appearance, penetration, and dispersion of oil sprays injected into a chamber of highly heated air at atmospheric pressure. The development of single sprays injected into a chamber containing air at room temperature and at high temperature was recorded by spray photography equipment. A comparison of spray records showed that with the air at the higher temperature, the spray assumed the appearance of thin, transparent cloud, the greatest part of which rapidly disappeared from view. With the chamber air at room temperature, a compact spray with an opaque core was obtained. Measurements of the records showed a decrease in penetration and an increase in the dispersion of the spray injected into the heated air. No ignition of the fuel injected was observed or recorded until the spray particles came in contact with the much hotter walls of the chamber about 0.3 second after the start of injection.

  10. Simulation of fundamental atomization mechanisms in fuel sprays

    NASA Technical Reports Server (NTRS)

    Childs, Robert, E.; Mansour, Nagi N.

    1988-01-01

    Growth of instabilities on the liquid/gas interface in the initial region of fuel sprays is studied by means of numerical simulations. The simulations are based on solutions of the variable-density incompressible Navier-Stokes equations, which are obtained with a new numerical algorithm. The simulations give good agreement with analytical results for the instabilities on a liquid cylinder induced by surface tension and wind-induced instabilities. The effects of boundary layers on the wind-induced instabilities are investigated. It is found that a boundary layer reduces the growth rate for a single interface, and a comparison with inviscid theory suggests that boundary layer effects may be significantly more important than surface tension effects. The results yield a better estimate than inviscid theory for the drop sizes as reported for diesel sprays. Results for the planar jet show that boundary layer effects hasten the growth of Squire's 'symmetric' mode, which is responsible for jet disintegration. This result helps explain the rapid atomization which occurs in swirl and air-blast atomizers.

  11. 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.

  12. Study on diesel-DME spray using open-source CFD (OpenFoam)

    NASA Astrophysics Data System (ADS)

    Fajar, Rizqon; Sugiarto, Bambang; Darsono, Dody

    2012-06-01

    In this work, a numerical study has been performed to evaluate the fuel spray of diesel, dimethyl ether (DME) and its mixture using CFD code OpenFoam. This study uses a general method, based on simulating fuel sprays injected into a constant volume vessel. Calculations results are presented as profiles of diameter (MD) and temperature of fuel droplets as function of fuel type. The results have shown that the diameter of fuel droplet decreased as the fraction of DME in the mixture is higher. Fuel properties affected the atomization and evaporation process. The SMD increased with viscosity and the evaporation rate of fuel spray increased with fuel volatility.

  13. Injector spray characterization of methanol in reciprocating engines

    SciTech Connect

    Dodge, L.; Naegeli, D.

    1994-06-01

    This report covers a study that addressed cold-starting problems in alcohol-fueled, spark-ignition engines by using fine-spray port-fuel injectors to inject fuel directly into the cylinder. This task included development and characterization of some very fine-spray, port-fuel injectors for a methanol-fueled spark-ignition engine. After determining the spray characteristics, a computational study was performed to estimate the evaporation rate of the methanol fuel spray under cold-starting and steady-state conditions.

  14. Study of ethanol and gasoline fuel sprays using mie-scatter and schlieren imaging

    NASA Astrophysics Data System (ADS)

    Bouchard, Lauren; Bittle, Joshua; Puzinauskas, Paul

    2016-11-01

    Many cars today are capable of running on both gasoline and ethanol, however it is not clear how well optimized the engines are for the multiple fuels. This experiment looks specifically at the fuel spray in a direct injection system. The length and angle of direct injection sprays were characterized and a comparison between ethanol and gasoline sprays was made. Fuels were tested using a modified diesel injector in a test chamber at variable ambient pressures and temperatures in order to simulate both high and low load combustion chamber conditions. Rainbow schlieren and mie-scatter imaging were both used to investigate the liquid and vapor portions of the sprays. The sprays behaved as expected with temperature and pressure changes. There was no noticeable fuel effect on the liquid portion of the spray (mie-scatter), though the gasoline vapor spray angles were wider than ethanol spray angles (possible a result of the distillation curves of the two fuels). Funding from NSF REU site Grant EEC 1358991 is greatly appreciated.

  15. Behavior Of Evaporating Liquid Drops In Clusters

    NASA Technical Reports Server (NTRS)

    Bellan, Josette

    1990-01-01

    Report presents critical analysis of methods, developed for calculating behavior of evaporating liquid drops in dense and dilute clusters. Essential to understanding variety of physical and chemical phenomena occurring in combustion of sprayed fuels and in sprays used in agriculture, food industry, and painting. Presents insights on important aspects of two-phase flow.

  16. Characterization of coal-water slurry fuel sprays from diesel engine injectors

    SciTech Connect

    Caton, J.A.; Kihm, K.D.

    1993-06-01

    Experiments were conducted to characterize coal-water slurry fuel sprays from diesel engine injectors. Since the combustion event is a strong function of the fuel spray, full characterization of the spray is a necessity for successful engine design and for modeling of the combustion process. Two experimental facilities were used at TAMU to study the injection of coal slurry fuels. The first experimental facility incorporates General Electric locomotive engine components (injection pump, fuel line, and nozzle) and a specially designed diaphragm to separate the abrasive coal slurry fuel from the moving parts of the pump. The second experimental facility is based on an accumulator injector from General Electric. Instrumentation includes instantaneous needle lift and fuel line pressure. A pressurized visualization chamber was used to provide a spray environment which simulated the engine gas density and permitted the use of spray diagnostic techniques. The study was divided into two phases: (1) overall characterization of the spray, and (2) detailed droplet size and size distribution characterization. In addition to this overall characterization of the spray, the second phase of this study characterized the details of the atomization quality.

  17. A laser tomographic investigation of liquid fuel sprays

    NASA Technical Reports Server (NTRS)

    Yule, A. J.; Ahseng, C.; Felton, P.; Ungut, A.; Chigier, N. A.

    1980-01-01

    A light scattering technique is combined with a tomographic transformation to convert line of sight integrated data, measured in sprays, to measurements of droplet size and concentration in volume elements within the spray. The technique is developed and assessed by systematic experiments in axisymmetric sprays generated by twin-fluid atomisers. The good agreement found shows that, provided certain conditions are satisfied by the local spray structure, the technique provides information on spray structure, similar in detail and extent to that derived by photography, but with reduced experimental time. The technique is applied to an investigation of a kerosene spray vaporizing in a hot gas stream.

  18. Modeling evaporation from spent nuclear fuel storage pools: A diffusion approach

    NASA Astrophysics Data System (ADS)

    Hugo, Bruce Robert

    Accurate prediction of evaporative losses from light water reactor nuclear power plant (NPP) spent fuel storage pools (SFPs) is important for activities ranging from sizing of water makeup systems during NPP design to predicting the time available to supply emergency makeup water following severe accidents. Existing correlations for predicting evaporation from water surfaces are only optimized for conditions typical of swimming pools. This new approach modeling evaporation as a diffusion process has yielded an evaporation rate model that provided a better fit of published high temperature evaporation data and measurements from two SFPs than other published evaporation correlations. Insights from treating evaporation as a diffusion process include correcting for the effects of air flow and solutes on evaporation rate. An accurate modeling of the effects of air flow on evaporation rate is required to explain the observed temperature data from the Fukushima Daiichi Unit 4 SFP during the 2011 loss of cooling event; the diffusion model of evaporation provides a significantly better fit to this data than existing evaporation models.

  19. Effect of fuel volatility and methanol blend usage on evaporative emissions

    SciTech Connect

    Gabele, P.A. )

    1987-01-01

    This study examines evaporative emissions and canister performance as a function of methanol usage and fuel volatility. A total of six different fuels are examined: three methanol blends and three gasoline fuels. Each methanol blend has been specially prepared so that its Reid vapor pressure (RVF) is matched with one of the gasoline fuels. The result is three methanol blend-gasoline fuel pairs having volatilities of 9 psi., 11.2 psi., and 14.4 psi RVP. Evaporative emissions from an automobile tested with these fuels are measured and characterized. In addition to these data, data detailing the composition of fuel tank head-space and canister weight gain and loss fluctuations are also presented.

  20. Combustion and evaporation characteristics of fuel droplets containing suspended energetic nanoparticles

    NASA Astrophysics Data System (ADS)

    Gan, Yanan

    Nanofluid fuel is a novel concept and has drawn great attentions in combustion and propulsion community recently. The focus of this research is to gain a fundamental understanding of the combustion and evaporation characteristics of nanofluids fuels. This study starts with the investigation of the physical and chemical methods to form a homogenous and stable nanofluid with low levels of agglomeration and the morphology of nanostructures were characterized. Then, we investigated the combustion characteristics of nanofluid fuel droplets using high-speed photography with and without backlight respectively. Droplet diameters and temperature histories were simultaneously measured. The emphasis is to explore the effects of particle size, materials, loading rate, surfactant concentration and type of base fuel on droplet combustion characteristics. Besides the combustion characteristics, we also studied the effect of added nanostructures on the evaporation characteristics of nanofluid fuel droplets. The evaporation rates of nanofluid droplets under well-controlled convection and radiation were measured and the effect of particle size, materials, loading rate and type of base fuel on the evaporation rates were analyzed. Theoretical studies were conducted to understand the particle transportation and aggregation mechanisms in the nanofluids. The importance of different aggregation mechanisms was evaluated to explain the different combustion behavior of liquid fuels droplet with nano- and micron particles. Furthermore, the nanoparticle aggregation history was numerically modeled by solving population balance equation in order to understand the potential role of particle aggregation on droplet evaporation rate under convection. In addition, the radiative properties of various nanofluid fuels were determined theoretically and further validated by the experimental data from spectroscopy analysis. Then, their effects on droplet evaporation rates under radiation were determined

  1. Evaporative cooling by a pulsed jet spray of binary ethanol-water mixture

    NASA Astrophysics Data System (ADS)

    Karpov, P. N.; Nazarov, A. D.; Serov, A. F.; Terekhov, V. I.

    2015-07-01

    We have experimentally studied the heat transfer under conditions of pulsed multinozzle jet spray impact onto a vertical surface. The working coolant fluid was aqueous ethanol solution in a range of concentrations K 1 = 0-96%. The duration of spray pulses was τ = 2, 4, and 10 ms at a repetition frequency of 10 Hz. The maximum heat transfer coefficient was achieved at an ethanol solution concentration within 50-60%. The thermal efficiency of pulsed spray cooling grows with increasing ethanol concentration and decreasing jet spray pulse duration.

  2. Mixing of an Airblast-atomized Fuel Spray Injected into a Crossflow of Air

    NASA Technical Reports Server (NTRS)

    Leong, May Y.; McDonell, Vincent G.; Samuelsen, G. Scott

    2000-01-01

    The injection of a spray of fuel droplets into a crossflow of air provides a means of rapidly mixing liquid fuel and air for combustion applications. Injecting the liquid as a spray reduces the mixing length needed to accommodate liquid breakup, while the transverse injection of the spray into the air stream takes advantage of the dynamic mixing induced by the jet-crossflow interaction. The structure of the spray, formed from a model plain-jet airblast atomizer, is investigated in order to determine and understand the factors leading to its dispersion. To attain this goal, the problem is divided into the following tasks which involve: (1) developing planar imaging techniques that visualize fuel and air distributions in the spray, (2) characterizing the airblast spray without a crossflow, and (3) characterizing the airblast spray upon injection into a crossflow. Geometric and operating conditions are varied in order to affect the atomization, penetration, and dispersion of the spray into the crossflow. The airblast spray is first characterized, using imaging techniques, as it issues into a quiescent environment. The spray breakup modes are classified in a liquid Reynolds number versus airblast Weber number regime chart. This work focuses on sprays formed by the "prompt" atomization mode, which induces a well-atomized and well-dispersed spray, and which also produces a two-lobed liquid distribution corresponding to the atomizing air passageways in the injector. The characterization of the spray jet injected into the crossflow reveals the different processes that control its dispersion. Correlations that describe the inner and outer boundaries of the spray jet are developed, using the definition of a two-phase momentum-flux ratio. Cross-sections of the liquid spray depict elliptically-shaped distributions, with the exception of the finely-atomized sprays which show kidney-shaped distributions reminiscent of those obtained in gaseous jet in crossflow systems. A droplet

  3. X-ray imaging of shock waves generated by high-pressure fuel sprays.

    PubMed

    MacPhee, Andrew G; Tate, Mark W; Powell, Christopher F; Yue, Yong; Renzi, Matthew J; Ercan, Alper; Narayanan, Suresh; Fontes, Ernest; Walther, Jochen; Schaller, Johannes; Gruner, Sol M; Wang, Jin

    2002-02-15

    Synchrotron x-radiography and a fast x-ray detector were used to record the time evolution of the transient fuel sprays from a high-pressure injector. A succession of 5.1-microsecond radiographs captured the propagation of the spray-induced shock waves in a gaseous medium and revealed the complex nature of the spray hydrodynamics. The monochromatic x-radiographs also allow quantitative analysis of the shock waves that has been difficult if not impossible with optical imaging. Under injection conditions similar to those found in operating engines, the fuel jets can exceed supersonic speeds and result in gaseous shock waves.

  4. Modelling of automotive fuel droplet heating and evaporation: mathematical tools and approximations

    NASA Astrophysics Data System (ADS)

    Sazhin, Sergei S.; Qubeissi, Mansour Al

    2016-06-01

    New mathematical tools and approximations developed for the analysis of automotive fuel droplet heating and evaporation are summarised. The approach to modelling biodiesel fuel droplets is based on the application of the Discrete Component Model (DCM), while the approach to modelling Diesel fuel droplets is based on the application of the recently developed multi-dimensional quasi-discrete model. In both cases, the models are applied in combination with the Effective Thermal Conductivity/Effective Diffusivity model and the implementation in the numerical code of the analytical solutions to heat transfer and species diffusion equations inside droplets. It is shown that the approximation of biodiesel fuel by a single component leads to under-prediction of droplet evaporation time by up to 13% which can be acceptable as a crude approximation in some applications. The composition of Diesel fuel was simplified and reduced to only 98 components. The approximation of 98 components of Diesel fuel with 15 quasi-components/components leads to under-prediction of droplet evaporation time by about 3% which is acceptable in most engineering applications. At the same time, the approximation of Diesel fuel by a single component and 20 alkane components leads to a decrease in the evaporation time by about 19%, compared with the case of approximation of Diesel fuel with 98 components. The approximation of Diesel fuel with a single alkane quasi-component (C14.763H31.526) leads to under-prediction of the evaporation time by about 35% which is not acceptable even for qualitative analysis of the process. In the case when n-dodecane is chosen as the single alkane component, the above-mentioned under-prediction increases to about 44%.

  5. Coal-water slurry spray characteristics of a positive displacement fuel injection system

    SciTech Connect

    Seshadri, A.K.; Caton, J.A.; Kihm, K.D.

    1992-12-31

    Experiments have been completed to characterized coal-water slurry sprays from a modified positive displacement fuel injection system of a diesel engine. The injection system includes an injection jerk pump driven by an electric motor, a specially designed diaphragm to separate the abrasive coal from the pump, and a single-hole fuel nozzle. The sprays were injected into a pressurized chamber equipped with windows. High speed movies and instantaneous fuel line pressures were obtained. For injection pressures of order 30 MPa or higher, the sprays were similar for coal-water slurry, diesel fuel and water. The time until the center core of the spray broke-up (break-up time) was determined from both the movies and from a model using the fuel line pressures. Results from these two independent procedures were in good agreement. For the base conditions, the break-up time was 0.58 and 0.50 ms for coal-water slurry and diesel fuel, respectively. The break-up times increased with increasing nozzle orifice size and with decreasing chamber density. The break-up time was not a function of coal loading for coal loadings up to 53%. Cone angles of the sprays were dependent on the operating conditions and fluid, as well as on the time and location of the measurement. For one set of cases studied, the time-averaged cone angle was 15.9{degree} and 16.3{degree} for coal-water slurry and diesel fuel, respectively.

  6. Study of optical and structural properties of CZTS thin films grown by co-evaporation and spray pyrolysis

    NASA Astrophysics Data System (ADS)

    Moreno, R.; Ramirez, E. A.; Gordillo Guzmán, G.

    2016-02-01

    Results regarding optical and structural properties of Cu2ZnSnS4 (CZTS) thin films prepared by co-evaporation using a novel procedure are compared with those obtained with CZTS films grown using a solution based route. The lattice strain ε and crystallite size D of CZTS films prepared by co-evaporation and by spray pyrolysis were estimated through X-ray diffraction (XRD) measurements using Williamson-Hall-isotropic strain model. The results of estimated average crystallite size of CZTS films by Scherrer and Williamson-Hall plot methods were compared with AFM (atomic force microscopy) measurements. It was found that the average crystallite size measured by Williamson-Hall plot methods agree quite well with AFM results. Further, information regarding the influence of preparation method on both, crystalline phases and the formation of structural defects was achieved through Raman and Urbach energy measurements.

  7. Group evaporation

    NASA Technical Reports Server (NTRS)

    Shen, Hayley H.

    1991-01-01

    Liquid fuel combustion process is greatly affected by the rate of droplet evaporation. The heat and mass exchanges between gas and liquid couple the dynamics of both phases in all aspects: mass, momentum, and energy. Correct prediction of the evaporation rate is therefore a key issue in engineering design of liquid combustion devices. Current analytical tools for characterizing the behavior of these devices are based on results from a single isolated droplet. Numerous experimental studies have challenged the applicability of these results in a dense spray. To account for the droplets' interaction in a dense spray, a number of theories have been developed in the past decade. Herein, two tasks are examined. One was to study how to implement the existing theoretical results, and the other was to explore the possibility of experimental verifications. The current theoretical results of group evaporation are given for a monodispersed cluster subject to adiabatic conditions. The time evolution of the fluid mechanic and thermodynamic behavior in this cluster is derived. The results given are not in the form of a subscale model for CFD codes.

  8. Exhaust and evaporative emissions from motorcycles fueled with ethanol gasoline blends.

    PubMed

    Li, Lan; Ge, Yunshan; Wang, Mingda; Peng, Zihang; Song, Yanan; Zhang, Liwei; Yuan, Wanli

    2015-01-01

    The emission characteristics of motorcycles using gasoline and E10 (90% gasoline and 10% ethanol by volume) were investigated in this article. Exhaust and evaporative emissions of three motorcycles were investigated on the chassis dynamometer over the Urban Driving Cycle (UDC) and in the Sealed Housing for Evaporative Determination (SHED) including regulated and unregulated emissions. The regulated emissions were detected by an exhaust gas analyzer directly. The unregulated emissions including carbonyls and volatile organic compounds (VOCs) were sampled through battery-operated air pumps using tubes coated with 2,4-dinitrophenylhydrazine (DNPH) and Tenax TA, respectively. The experimental results showed that the emission factors of total hydrocarbons (THC) and carbon monoxide (CO) from E10 fueling motorcycles decreased by 26%-45% and 63%-73%, while the emission factor of NOx increased by 36%-54% compared with those from gasoline fueling motorcycles. For unregulated emissions, the emission amount of VOCs from motorcycles fueled with E10 decreased by 18%-31% while total carbonyls were 2.6-4.5 times higher than those for gasoline. For evaporative emissions of THC and VOCs, for gasoline or E10, the diurnal breathing loss (DBL) was higher than hot soak loss (HSL). Using E10 as a fuel does not make much difference in the amount of evaporative THC, while resulted in a slightly growth of 14%-17% for evaporative BETX (benzene, toluene, ethylbenzene, xylene). Copyright © 2014 Elsevier B.V. All rights reserved.

  9. Effect of aviation fuel type and fuel injection conditions on the spray characteristics of pressure swirl and hybrid air blast fuel injectors

    NASA Astrophysics Data System (ADS)

    Feddema, Rick

    Feddema, Rick T. M.S.M.E., Purdue University, December 2013. Effect of Aviation Fuel Type and Fuel Injection Conditions on the Spray Characteristics of Pressure Swirl and Hybrid Air Blast Fuel Injectors. Major Professor: Dr. Paul E. Sojka, School of Mechanical Engineering Spray performance of pressure swirl and hybrid air blast fuel injectors are central to combustion stability, combustor heat management, and pollutant formation in aviation gas turbine engines. Next generation aviation gas turbine engines will optimize spray atomization characteristics of the fuel injector in order to achieve engine efficiency and emissions requirements. Fuel injector spray atomization performance is affected by the type of fuel injector, fuel liquid properties, fuel injection pressure, fuel injection temperature, and ambient pressure. Performance of pressure swirl atomizer and hybrid air blast nozzle type fuel injectors are compared in this study. Aviation jet fuels, JP-8, Jet A, JP-5, and JP-10 and their effect on fuel injector performance is investigated. Fuel injector set conditions involving fuel injector pressure, fuel temperature and ambient pressure are varied in order to compare each fuel type. One objective of this thesis is to contribute spray patternation measurements to the body of existing drop size data in the literature. Fuel droplet size tends to increase with decreasing fuel injection pressure, decreasing fuel injection temperature and increasing ambient injection pressure. The differences between fuel types at particular set conditions occur due to differences in liquid properties between fuels. Liquid viscosity and surface tension are identified to be fuel-specific properties that affect the drop size of the fuel. An open aspect of current research that this paper addresses is how much the type of aviation jet fuel affects spray atomization characteristics. Conventional aviation fuel specifications are becoming more important with new interest in alternative

  10. The Effect of Nozzle Design and Operating Conditions on the Atomization and Distribution of Fuel Sprays

    NASA Technical Reports Server (NTRS)

    Lee, Dana W

    1933-01-01

    The atomization and distribution characteristics of fuel sprays from automatic injection valves for compression-ignition engines were determined by catching the fuel drops on smoked-glass plates, and then measuring and counting the impressions made in the lampblack. The experiments were made in an air-tight chamber in which the air density was raised to values corresponding to engine conditions.

  11. Supersonic Turbulent Fuel-Air Mixing and Evaporation

    DTIC Science & Technology

    2007-11-02

    and testing , of an all speed numerical procedure for the simulation of turbulent mixing and evaporation of droplets. The numeric is based on a Multi...regimes, for the discrete and continuous phases. Three two-equation turbulence models are implemented and tested , with modifications to account for...thermal conductivity, and the gas enthalpy is defined as: hg = Ykhk ~k= (air,vap ) = Yair,ghair,g + Yvap,ghvap,g (34) where hair,g = cp,air,g Tg

  12. Experimental investigation of fuel evaporation in the vaporizing elements of combustion chambers

    NASA Technical Reports Server (NTRS)

    Vezhba, I.

    1979-01-01

    A description is given of the experimental apparatus and the methods used in the investigation of the degree of fuel (kerosene) evaporation in two types of vaporizing elements in combustion chambers. The results are presented as dependences of the degree of fuel evaporation on the factors which characterize the functioning of the vaporizing elements: the air surplus coefficient, the velocity of flow and temperature of the air at the entrance to the vaporizing element and the temperature of the wall of the vaporizing element.

  13. Numerical study of solid fuel evaporation and auto-ignition in a dump combustor

    NASA Astrophysics Data System (ADS)

    Tahsini, A. M.; Farshchi, M.

    2010-10-01

    Evaporation of polymeric solid fuels in backward facing step geometry subject to an inlet oxidizer flow at elevated temperatures is considered and convective heating of the fuel surface by the hot oxidizing inlet flow and subsequent mixing of the evaporated fuel with the oxidizer flow and its combustion is numerically studied. The objective of this work is to gain insight into the auto-ignition of the fuel and its controlling parameters in this configuration. The system of governing equations is solved with a finite volume approach using a structured grid in which the AUSM + scheme is used to calculate the gas phase convective fluxes. The flowfield is turbulent and the Spalart-Allmaras turbulence model is used in these simulations. Special attention is paid to the coupling of gas and solid phase to study the ignition process. Distinct intervals in ignition delay time are studied and evaporation time, mixing time, and reaction time are individually estimated. We have demonstrated that for inlet oxidizer streams with high initial oxygen concentration levels and high enough inlet temperatures a diffusion-controlled ignition mechanism controls the ignition time delay independent of the inlet velocity. This ignition time delay is directly related to the solid fuel evaporation time delay.

  14. Quantification of the evaporative cooling in an ethanol spray created by a gasoline direct-injection system measured by multiline NO-LIF gas-temperature imaging.

    PubMed

    Kronemayer, Helmut; Omerbegovic, Kemal; Schulz, Christof

    2007-12-01

    Two-dimensional gas-phase temperature fields were quantitatively measured in an evaporating ethanol spray with multiline excitation thermometry based on laser-induced fluorescence of nitric oxide (NO-LIF). This technique yields absolute temperature fields without calibration and simultaneously detects the spray position. The accuracy of the presented temperature measurements is +/-1 K. Systematic errors of the scanned multiline thermometry approach due to time averaging in turbulent systems were investigated and found to be negligible. The pulsed spray was generated by a gasoline direct-injection nozzle with swirl injecting ethanol into air in a flow cell at room temperature and atmospheric pressure. The gas temperature inside the spray cloud was found to decrease by 10 K at approximately 5-10 ms after injection. Different injection pressures influence the evaporation behavior.

  15. Experimental analysis and semicontinuous simulation of low-temperature droplet evaporation of multicomponent fuels

    NASA Astrophysics Data System (ADS)

    Lehmann, S.; Lorenz, S.; Rivard, E.; Brüggemann, D.

    2015-01-01

    Low-pollutant and efficient combustion not only in internal combustion engines requires a balanced gaseous mixture of fuel and oxidizer. As fuels may contain several hundred different chemical species with different physicochemical properties as well as defined amounts of biogenic additives, e.g., ethanol, a thorough understanding of liquid fuel droplet evaporation processes is necessary to allow further engine optimization. We have studied the evaporation of fuel droplets at low ambient temperature. A non-uniform temperature distribution inside the droplet was already considered by including a finite thermal conductivity in a one-dimensional radial evaporation model (Rivard and Brüggemann in Chem Eng Sci 65(18):5137-5145, 2010). For a detailed analysis of droplet evaporation, two non-laser-based experimental setups have been developed. They allow a fast and relatively simple but yet precise measurement of diameter decrease and composition change. The first method is based on collecting droplets in a diameter range from 70 to 150 µm by a high-precision scale. A simultaneous evaluation of mass increase is employed for an accurate average diameter value determination. Subsequently, a gas chromatographic analysis of the collected droplets was conducted. In the second experiment, evaporation of even smaller droplets was optically analyzed by a high-speed shadowgraphy/schlieren microscope setup. A detailed analysis of evaporating E85 (ethanol/gasoline in a mass ratio of 85 %/15 %) and surrogate fuel droplets over a wide range of initial droplet diameters and ambient temperatures was conducted. The comparison of experimental and numerical results shows the applicability of the developed model over a large range of diameters and temperatures.

  16. Diffusion Of Mass In Evaporating Multicomponent Drops

    NASA Technical Reports Server (NTRS)

    Bellan, Josette; Harstad, Kenneth G.

    1992-01-01

    Report summarizes study of diffusion of mass and related phenomena occurring in evaporation of dense and dilute clusters of drops of multicomponent liquids intended to represent fuels as oil, kerosene, and gasoline. Cluster represented by simplified mathematical model, including global conservation equations for entire cluster and conditions on boundary between cluster and ambient gas. Differential equations of model integrated numerically. One of series of reports by same authors discussing evaporation and combustion of sprayed liquid fuels.

  17. Diffusion Of Mass In Evaporating Multicomponent Drops

    NASA Technical Reports Server (NTRS)

    Bellan, Josette; Harstad, Kenneth G.

    1992-01-01

    Report summarizes study of diffusion of mass and related phenomena occurring in evaporation of dense and dilute clusters of drops of multicomponent liquids intended to represent fuels as oil, kerosene, and gasoline. Cluster represented by simplified mathematical model, including global conservation equations for entire cluster and conditions on boundary between cluster and ambient gas. Differential equations of model integrated numerically. One of series of reports by same authors discussing evaporation and combustion of sprayed liquid fuels.

  18. Coal-water slurry spray characteristics of an electronically-controlled accumulator fuel injection system

    SciTech Connect

    Caton, J.A.; Payne, S.E.; Terracina, D.P.; Kihm, K.D.

    1993-12-31

    Experiments have been complete to characterize coal-water slurry sprays from a electronically-controlled accumulator fuel injection system of diesel engine. The sprays were injected into a pressurized chamber equipped with windows. High speed movies, fuel pressures and needle lifts were obtained as a function of time, orifice diameter, coal loading, gas density in the chamber, and accumulator fuel pressure. For the base conditions 50% (by mass) coal loading, 0.4 mm diameter nozzle hole, coal-water slurry pressure of 82 MPa (12,000 psi), and a chamber density of 25 kg/m{sup 3}, the break-up time was 0. 30 ms. An empirical correlation for both spray tip penetration and initial jet velocity was developed. For the conditions of this study, the spray tip penetration and initial jet velocity were 15% greater for coal-water slurry than for diesel fuel or water. Cone angles of the sprays were dependent on the operating conditions and fluid, as well as the time and locations of the measurement. The time-averaged cone angle for the base case conditions was 13.6{degree}. Results of this study and the correlation are specific to the tested coal-water slurry and are not general for other coal-water slurry fuels.

  19. Combustion of Drops and Sprays of Heavy Fuel Oils and Their Emulsions.

    DTIC Science & Technology

    1980-12-01

    of isolated drops can be generated by supplying the fuel from a pressurized fuel tank through a fine needle shaped hypodermic tube. For spray...Another severe problem that arose during these tests was clogging of the hypodermic needle through which single drops were injected. This was thought to be...caused essentially by the liquid phase cracking of the fuel inside the hypodermic needle . Therefore, we decided to use a slightly larger inside

  20. Penetration and Duration of Fuel Sprays from a Pump Injection System

    NASA Technical Reports Server (NTRS)

    Rothrock, A M; Marsh, E T

    1934-01-01

    High-speed motion pictures were taken of individual fuel sprays from a pump injection system. The changes in the spray-tip penetration with changes in the pump speed, injection-valve opening and closing pressures, discharge-orifice area, injection-tube length and diameter, and pump throttle setting were measured. The pump was used with and without a check valve. The results show that the penetration of the spray tip can be controlled by the dimensions of the injection tube, the area of the discharge orifice, and the injection-valve opening and closing pressures.

  1. Effect of Water Spray Evaporative Cooling at the Inlet of Regeneration Air Stream on the Performance of an Adsorption Desiccant Cooling Process

    NASA Astrophysics Data System (ADS)

    Ando, Kosuke; Kodama, Akio; Hirose, Tsutomu; Goto, Motonobu; Okano, Hiroshi

    This paper shows an influence of evaporative cooler at the inlet of regeneration air stream of an adsorptive desiccant cooling process on the cooling/dehumidifying performance. This evaporative cooling was expected to cause humidity increase in regeneration air reducing the dehumidifying performance of the honeycomb absorber, while the evaporative cooling plays an important role to produce a lower temperature in supply air. Two different airs to be used for the regeneration of the desiccant wheel were considered. One was fresh outside air (OA mode) and the other was air ventilated from the room (RA mode). Experimental results showed that the amount of dehumidified water obtained at the process without water spray evaporative cooler was actually larger than that of process with water spray evaporative cooler. This behavior was mainly due to increase of humidity or relative humidity in the regeneration air as expected. However, temperature of supply air produced by the process with the evaporator was rather lower than that of the other because of the cooled return air, resulting higher CE value. Regarding the operating mode, the evaporative cooler at the OA-mode was no longer useful at higher ambient humidity because of the difficulty of the evaporation of the water in such high humidity. It was also found that its dehumidifying performance was remarkably decreased at higher ambient humidity and lower regeneration temperature since the effective adsorption capacity at the resulting high relative humidity of the regeneration air decreased.

  2. Formation of oxides of nitrogen in monodisperse spray combustion of hydrocarbon fuels

    NASA Technical Reports Server (NTRS)

    Nizami, A. A.; Singh, S.; Cernansky, N. P.

    1982-01-01

    Experimental results of exit plane NO/NO(x) emissions from atmospheric monodisperse fuel spray combustion are presented. Six different hydrocarbon fuels were studied: isopropanol, n-propanol, n-octane, iso-octane, n-heptane and methanol. The results indicate an optimum droplet size for minimizing NO/NO(x) production for all of the test fuels. At the optimum droplet diameter, reductions in NO/NO(x) relative to the NO(x) occurred at droplet diameters of 55 and 48 microns respectively, as compared to a 50-micron droplet size for isopropanol. The occurrence of the minimum NO(x) point at different droplet diameters for the different fuels appears to be governed by the extent of prevaporization of the fuel in the spray, and is consistent with theoretical calculations based on each fuel's physical properties. Estimates are also given for the behavior of heavy fuels and of polydisperse fuel sprays in shifting the minimum NO(x) point compared to a monodisperse situation.

  3. 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.

  4. Fuel Spray and Flame Formation in a Compression-Ignition Engine Employing Air Flow

    NASA Technical Reports Server (NTRS)

    Rothrock, A M; Waldron, C D

    1937-01-01

    The effects of air flow on fuel spray and flame formation in a high-speed compression-ignition engine have been investigated by means of the NACA combustion apparatus. The process was studied by examining high-speed motion pictures taken at the rate of 2,200 frames a second. The combustion chamber was of the flat-disk type used in previous experiments with this apparatus. The air flow was produced by a rectangular displacer mounted on top of the engine piston. Three fuel-injection nozzles were tested: a 0.020-inch single-orifice nozzle, a 6-orifice nozzle, and a slit nozzle. The air velocity within the combustion chamber was estimated to reach a value of 425 feet a second. The results show that in no case was the form of the fuel spray completely destroyed by the air jet although in some cases the direction of the spray was changed and the spray envelope was carried away by the moving air. The distribution of the fuel in the combustion chamber of a compression-ignition engine can be regulated to some extent by the design of the combustion chamber, by the design of the fuel-injection nozzle, and by the use of air flow.

  5. Application of digital image analysis techniques to antimisting fuel spray characterization

    SciTech Connect

    Fleeter, R.; Sarohia, V.; Toaz, R.

    1983-01-01

    A system for fuel mist characterization using digital image analysis and processing techniques has been developed and applied to research on aviation safety fuels. Pulsed ruby laser sheet illumination of the spray is used for initial data recording on very high resolution photographic film. Digitization of mosaic elements is accomplished with a vidicon and video digitizer whose output is stored in computer RAM (Random Access Memory) memory for processing. Highly non-spherical elements and a wide range of drop diameters (8-2000 ..mu..m) resulting from the unusual rheological properties of the fuel-additive system are accomodated by the device configuration and algorithms. Generation of two-dimensional images via scattered light also eliminates errors resulting from variations in the index of refraction and from the presence of submicron scattering sites often present within the modified fuel. No a priori information on the drop size distribution nor on system response to various drop sizes is required. This wide dynamic range, insensitivity to drop optical properties and the lack of a priori assumptions concerning drop shape are some of the unique features of the present analysis technique which are not available in single currently available drop counting methods. A drop histogram is generated for any portion of a spray or for an entire spray field along with local and global spray Sauter mean diameter (SMD) and density information. The technique is applied to analysis of sprays formed in a simulation of an aircraft crash with fuel spillage. Measurements of spray SMD and density are correlated with the results of flammability tests.

  6. Investigation of spray dispersion and particulate formation in diesel fuel flames

    NASA Technical Reports Server (NTRS)

    Back, L. H.; Bankston, C. P.; Kwack, E. Y.; Bellan, J.; Harstad, K.

    1988-01-01

    An experimental study of electrostatical atomized and dispersed diesel fuel jets was conducted at various back pressures to 40 atm. A new electrostatic injection technique was utilized to generate continuous, stable fuel sprays at charge densities of 1.5 to 2.0 C/m3 of fluid at one atm, and about 1.0 C/m3 at 40 atm. Flowrates were varied from 0.5 to 2.5 ml/s and electric potentials to -18 kV. Visual observations showed that significant enhanced dispersion of charged fuel jets occurred at high back pressures compared to aerodynamic breakup and dispersion. The average drop size was about the same as the spray triode orifice diameter, and was between the Kelly theory and the Rayleigh limit. The ignition tests, done only at one atm, indicated stable combustion of the electrostatically dispersed fuel jets.

  7. Ceramic plasma-sprayed coating of melting crucibles for casting metal fuel slugs

    NASA Astrophysics Data System (ADS)

    Kim, Ki Hwan; Lee, Chong Tak; Lee, Chan Bock; Fielding, R. S.; Kennedy, J. R.

    2013-10-01

    Thermal cycling and melt reaction studies of ceramic coatings plasma-sprayed on Nb substrates were carried out to evaluate the performance of barrier coatings for metallic fuel casting applications. Thermal cycling tests of the ceramic plasma-sprayed coatings to 1450 °C showed that HfN, TiC, ZrC, and Y2O3 coating had good cycling characteristics with few interconnected cracks even after 20 cycles. Interaction studies by 1550 °C melt dipping tests of the plasma-sprayed coatings also indicated that HfN and Y2O3 do not form significant reaction layer between U-20 wt.% Zr melt and the coating layer. Plasma-sprayed Y2O3 coating exhibited the most promising characteristics among HfN, TiC, ZrC, and Y2O3 coating.

  8. Ceramic plasma-sprayed coating of melting crucibles for casting metal fuel slugs

    SciTech Connect

    K.H. Kim; C.T. Lee; C.B. Lee; R.S. Fielding; J.R. Kennedy

    2013-10-01

    Thermal cycling and melt reaction studies of ceramic coatings plasma-sprayed on Nb substrates were carried out to evaluate the performance of barrier coatings for metallic fuel casting applications. Thermal cycling tests of the ceramic plasma-sprayed coatings to 1450 degrees C showed that HfN, TiC, ZrC, and Y2O3 coating had good cycling characteristics with few interconnected cracks even after 20 cycles. Interaction studies by 1550 degrees C melt dipping tests of the plasma-sprayed coatings also indicated that HfN and Y2O3 do not form significant reaction layer between U–20 wt.% Zr melt and the coating layer. Plasma-sprayed Y2O3 coating exhibited the most promising characteristics among HfN, TiC, ZrC, and Y2O3 coating.

  9. Evaporative and exhaust emissions from cars fueled with gasoline containing ethanol or methyl tert-butyl ether

    SciTech Connect

    Furey, R.L.; King, J.B.

    1980-01-01

    Vehicle tests showed that evaporative emissions were increased significantly by adding 10% ethanol to gasoline, but were increased less with 15% MTBE in gasoline. The quantity of ethanol or MTBE in evaporative emissions was investigated in laboratory tests. Exhaust HC, CO, and NO/sub x/ emissions from a car without closed-loop fuel control were significantly lower with the ethanol and MTBE fuel blends than with gasoline. For cars equipped with closed-loop carburetors, the absolute differences in exhaust emissions among the fuels were small. Fuel economy and driveability were worse with ethanol and MTBE fuel blends than with gasoline.

  10. Combustion characteristics in the transition region of liquid fuel sprays

    NASA Technical Reports Server (NTRS)

    Cernansky, N. P.; Namer, I.; Tidona, R. J.

    1984-01-01

    A number of important effects were observed in the droplet size transition region in spray combustion systems. In this region, where the mechanism of flame propagation is transformed from diffusive to premixed dominated combustion, the following effects have been observed: (1) maxima in burning velocity; (2) extension of flammability limits; (3) minima in ignition energy; and (4) minima in NO(x) formation. Unfortunately, because of differences in experimental facilities and limitations in the ranges of experimental data, a unified description of these transition region effects is not available at this time. Consequently, a fundamental experimental investigation was initiated to study the effect of droplet size, size distribution, and operating parameters on these transition region phenomena in a single well controlled spray combustion facility.

  11. The Gas Dynamics of High-Velocity Oxy-Fuel Thermal Sprays

    NASA Astrophysics Data System (ADS)

    Hackett, Charles Marcou

    An experimental study of the gas dynamics of the High-Velocity Oxy-Fuel (HVOF) thermal spray process has been performed. With this process, a hot, combustion-driven, supersonic jet is used to propel particles onto a surface, thus forming metal coatings that provide wear, temperature, and corrosion resistance. The fundamental physics of the spray process were studied and several key areas of interest were identified for in-depth study. Optical diagnostic techniques, including microsecond -exposure schlieren and shadowgraph imaging, were used to visualize the hot supersonic jet produced during the spray process. Energetic turbulent mixing of the jet with the surrounding atmosphere was observed. Measurements of oxide levels in aluminum and mild steel coatings sprayed for a range of conditions indicated that the turbulent mixing influences coating oxidation. However, experiments conducted with a low-speed coaxial shroud of inert gas demonstrated that coating oxide formation can be effectively controlled during the spray process. A simple numerical model was developed to predict the behavior of a spray particle in the HVOF jet. The results of computations indicated that independent control of spray particle velocity and temperature was possible through systematic variations in combustion chamber pressure and particle injection location within the nozzle. This hypothesis was confirmed through a series of experiments in which stainless steel particle velocity and temperature were measured using trace velocimetry and two-color radiative pyrometry, respectively. Combustion chamber pressure had a strong effect on particle velocity. Injection location was used to control the residence time of a particle within the flow, thus allowing manipulation of particle temperature without a measurable effect on velocity. Thus, the results of these experiments revealed that the gas dynamics--the behavior of the compressible gas flow--of the HVOF spray process strongly influenced spray

  12. A model of the evaporation of binary-fuel clusters of drops

    NASA Technical Reports Server (NTRS)

    Harstad, K.; Bellan, J.

    1991-01-01

    A formulation has been developed to describe the evaporation of dense or dilute clusters of binary-fuel drops. The binary fuel is assumed to be made of a solute and a solvent whose volatility is much lower than that of the solute. Convective flow effects, inducing a circulatory motion inside the drops, are taken into account, as well as turbulence external to the cluster volume. Results obtained with this model show that, similar to the conclusions for single isolated drops, the evaporation of the volatile is controlled by liquid mass diffusion when the cluster is dilute. In contrast, when the cluster is dense, the evaporation of the volatile is controlled by surface layer stripping, that is, by the regression rate of the drop, which is in fact controlled by the evaporation rate of the solvent. These conclusions are in agreement with existing experimental observations. Parametric studies show that these conclusions remain valid with changes in ambient temperature, initial slip velocity between drops and gas, initial drop size, initial cluster size, initial liquid mass fraction of the solute, and various combinations of solvent and solute. The implications of these results for computationally intensive combustor calculations are discussed.

  13. A model of the evaporation of binary-fuel clusters of drops

    NASA Technical Reports Server (NTRS)

    Harstad, K.; Bellan, J.

    1991-01-01

    A formulation has been developed to describe the evaporation of dense or dilute clusters of binary-fuel drops. The binary fuel is assumed to be made of a solute and a solvent whose volatility is much lower than that of the solute. Convective flow effects, inducing a circulatory motion inside the drops, are taken into account, as well as turbulence external to the cluster volume. Results obtained with this model show that, similar to the conclusions for single isolated drops, the evaporation of the volatile is controlled by liquid mass diffusion when the cluster is dilute. In contrast, when the cluster is dense, the evaporation of the volatile is controlled by surface layer stripping, that is, by the regression rate of the drop, which is in fact controlled by the evaporation rate of the solvent. These conclusions are in agreement with existing experimental observations. Parametric studies show that these conclusions remain valid with changes in ambient temperature, initial slip velocity between drops and gas, initial drop size, initial cluster size, initial liquid mass fraction of the solute, and various combinations of solvent and solute. The implications of these results for computationally intensive combustor calculations are discussed.

  14. A study of the current group evaporation/combustion theories

    NASA Technical Reports Server (NTRS)

    Shen, Hayley H.

    1990-01-01

    Liquid fuel combustion can be greatly enhanced by disintegrating the liquid fuel into droplets, an effect achieved by various configurations. A number of experiments carried out in the seventies showed that combustion of droplet arrays and sprays do not form individual flames. Moreover, the rate of burning in spray combustion greatly deviates from that of the single combustion rate. Such observations naturally challenge its applicability to spray combustion. A number of mathematical models were developed to evaluate 'group combustion' and the related 'group evaporation' phenomena. This study investigates the similarity and difference of these models and their applicability to spray combustion. Future work that should be carried out in this area is indicated.

  15. Planar Laser-Induced Fluorescence fuel concentration measurements in isothermal Diesel sprays.

    PubMed

    Pastor, José; López, José; Juliá, J; Benajes, Jesús

    2002-04-08

    This paper presents a complete methodology to perform fuel concentration measurements of Diesel sprays in isothermal conditions using the Planar Laser-Induced Fluorescence (PLIF) technique. The natural fluorescence of a commercial Diesel fuel is used with an excitation wavelength of 355 nm. The correction and calibration procedures to perform accurate measurements are studied. These procedures include the study of the fluorescence characteristics of the fuel as well as the correction of the laser sheet non-homogeneities and the losses due to Mie scattering, absorption and autoabsorption. The results obtained are compared with theoretical models and other experimental techniques.

  16. Impingement of Liquid Fuel Sprays on Heated Walls.

    DTIC Science & Technology

    1986-02-12

    literature. Gottfried, Lee, and Bell (11) performed an extensive analysis of the Leidenfrost phenomenon. The Leidenfrost phenomenon occurs when a drop...temperature until the Leidenfrost point where the evaporation time suddenly increases. Wachters and Westerling (12) demonstrated that the behavior of a... Leidenfrost temperature of a particular liquid depends on the material properties and the surface roughness of the plate. A plate material with a low

  17. Impact of alternative fuel rheology on spraying process of small pressure-swirl atomizer

    SciTech Connect

    Malý, Milan Janáčková, Lada; Jedelský, Jan Jícha, Miroslav

    2016-06-30

    A systematic investigation was made to analyse the atomizing performance of a small pressure-swirl atomizer with different crude-oil based fuels and water. The atomizer performance is characterized in terms of discharge coefficient, droplet Sauter mean diameter and nozzle efficiency. Phase-Doppler anemometry was used to measure droplets sizes and velocities and to determine the mean structure of the developed spray. A strong dependence of liquid viscosity on the mass flow rate through the atomizer as well as on the spray quality was found and discussed in comparison with relevant literature.

  18. Penetration and Duration of Fuel Sprays from a Pump Injection System

    NASA Technical Reports Server (NTRS)

    Rothrock, A M; Marsh, E T

    1931-01-01

    High-speed motion pictures were taken of individual fuel sprays from a pump injection system. The changes in the spray-tip penetration with changes in the pump speed, injection-valve opening and closing pressures, discharge-orifice area, injection-tube length and diameter, and pump throttle setting were measured. In addition, the effects of the variables on the time lag and duration of injection can be controlled by the dimensions of the injection tube, the area of the discharge orifice, and the injection-valve opening and closing pressures.

  19. Production of Babbitt Coatings by High Velocity Oxygen Fuel (HVOF) Spraying

    NASA Astrophysics Data System (ADS)

    Nascimento, A. R. C.; Ettouil, F. B.; Moreau, C.; Savoie, S.; Schulz, R.

    2017-10-01

    This work presents HVOF as an alternative means to produce dense Babbitt coatings by thermal spray. A radial injection setup and low fuel flow rates were used to minimize heat transfer to the low melting point alloy. In-flight particle diagnostic systems were used to correlate spray parameters with the changes in particle velocity and thermal radiation intensity. The use of particles with larger diameters resulted in higher deposition efficiencies. It was shown that HVOF Babbitt coatings combine a dense structure and a fine distribution of intermetallic phases when compared to more traditional babbitting techniques.

  20. Production of Babbitt Coatings by High Velocity Oxygen Fuel (HVOF) Spraying

    NASA Astrophysics Data System (ADS)

    Nascimento, A. R. C.; Ettouil, F. B.; Moreau, C.; Savoie, S.; Schulz, R.

    2017-08-01

    This work presents HVOF as an alternative means to produce dense Babbitt coatings by thermal spray. A radial injection setup and low fuel flow rates were used to minimize heat transfer to the low melting point alloy. In-flight particle diagnostic systems were used to correlate spray parameters with the changes in particle velocity and thermal radiation intensity. The use of particles with larger diameters resulted in higher deposition efficiencies. It was shown that HVOF Babbitt coatings combine a dense structure and a fine distribution of intermetallic phases when compared to more traditional babbitting techniques.

  1. Impact of alternative fuel rheology on spraying process of small pressure-swirl atomizer

    NASA Astrophysics Data System (ADS)

    Malý, Milan; Janáčková, Lada; Jedelský, Jan; Jícha, Miroslav

    2016-06-01

    A systematic investigation was made to analyse the atomizing performance of a small pressure-swirl atomizer with different crude-oil based fuels and water. The atomizer performance is characterized in terms of discharge coefficient, droplet Sauter mean diameter and nozzle efficiency. Phase-Doppler anemometry was used to measure droplets sizes and velocities and to determine the mean structure of the developed spray. A strong dependence of liquid viscosity on the mass flow rate through the atomizer as well as on the spray quality was found and discussed in comparison with relevant literature.

  2. A compressible real gas eulerian model for LES of fuel sprays

    NASA Astrophysics Data System (ADS)

    Knudsen, Edward; Doran, Eric

    2015-11-01

    A compressible solver for eulerian multiphase spray simulations is presented. This large eddy simulation solver employs a Peng-Robinson (PR) equation of state to describe mixtures of two species such as liquid dodecane and gaseous nitrogen. Modeling challenges associated with the use of PR are discussed, as are the resource requirements associated with using a compressible formulation to describe liquids when full fuel injector applications are considered. The solver is analyzed using canonical cases and the Spray A experiment from the Engine Combustion Network.

  3. Numerical Simulations of Evaporating Sprays in High Pressure and Temperature Operating Conditions (Engine Combustion Network [ECN])

    DTIC Science & Technology

    2014-05-01

    Dynamics (CFD) solver and provide expertise in simulations of complex multiphase flows . Two benchmark cases were selected based on the Engine...density and fuel efficiency). In response to this, a multiphase flow solver CONVERGE, developed by Convergent Science, Inc. (CSI), has been adopted...increase the temperature of the flowing gas up to the selected temperature. A control system (closed loop proportional-integral-derivative [PID

  4. Assessing carbon and hydrogen isotopic fractionation of diesel fuel n-alkanes during progressive evaporation.

    PubMed

    Muhammad, Syahidah A; Hayman, Alan R; Van Hale, Robert; Frew, Russell D

    2015-01-01

    Compound-specific isotope analysis offers potential for fingerprinting of diesel fuels, however, possible confounding effects of isotopic fractionation due to evaporation need to be assessed. This study measured the fractionation of the stable carbon and hydrogen isotopes in n-alkane compounds in neat diesel fuel during evaporation. Isotope ratios were measured using a continuous flow gas chromatograph/isotope ratio mass spectrometer. Diesel samples were progressively evaporated at 24 ± 2°C for 21 days. Increasing depletion of deuterium in nC12-nC17 alkanes in the remaining liquid with increasing carbon chain length was observed. Negligible carbon isotope fractionation was observed. Preferential vaporization was measured for the shorter chain n-alkanes and the trend decreased with increasing chain length. The decrease in δ(2) H values indicates the preferential vaporization of the isotopically heavier species consistent with available quantitative data for hydrocarbons. These results are most important in the application of stable isotope technology to forensic analysis of diesel.

  5. Heat Transfer to Fuel Sprays Injected into Heated Gases

    NASA Technical Reports Server (NTRS)

    Selden, Robert F; Spencer, Robert C

    1938-01-01

    This report presents the results of a study made of the influence of several variables on the pressure decrease accompanying injection of a relatively cool liquid into a heated compressed gas. Indirectly, this pressure decrease and the time rate of change of it are indicative of the total heat transferred as well as the rate of heat transfer between the gas and the injected liquid. Air, nitrogen, and carbon dioxide were used as ambient gases; diesel fuel and benzene were the injected liquids. The gas densities and gas-fuel ratios covered approximately the range used in compression-ignition engines. The gas temperatures ranged from 150 degrees c. to 350 degrees c.

  6. Solid oxide fuel cell processing using plasma arc spray deposition techniques. Final report

    SciTech Connect

    Ray, E.R.; Spengler, C.J.; Herman, H.

    1991-07-01

    The Westinghouse Electric Corporation, in conjunction with the Thermal Spray Laboratory of the State University of New York, Stony Brook, investigated the fabrication of a gas-tight interconnect layer on a tubular solid oxide fuel cell with plasma arc spray deposition. The principal objective was to determine the process variables for the plasma spray deposition of an interconnect with adequate electrical conductivity and other desired properties. Plasma arc spray deposition is a process where the coating material in powder form is heated to or above its melting temperature, while being accelerated by a carrier gas stream through a high power electric arc. The molten powder particles are directed at the substrate, and on impact, form a coating consisting of many layers of overlapping, thin, lenticular particles or splats. The variables investigated were gun power, spray distance, powder feed rate, plasma gas flow rates, number of gun passes, powder size distribution, injection angle of powder into the plasma plume, vacuum or atmospheric plasma spraying, and substrate heating. Typically, coatings produced by both systems showed bands of lanthanum rich material and cracking with the coating. Preheating the substrate reduced but did not eliminate internal coating cracking. A uniformly thick, dense, adherent interconnect of the desired chemistry was finally achieved with sufficient gas- tightness to allow fabrication of cells and samples for measurement of physical and electrical properties. A cell was tested successfully at 1000{degree}C for over 1,000 hours demonstrating the mechanical, electrical, and chemical stability of a plasma-arc sprayed interconnect layer.

  7. Solid oxide fuel cell processing using plasma arc spray deposition techniques

    SciTech Connect

    Ray, E.R.; Spengler, C.J.; Herman, H.

    1991-07-01

    The Westinghouse Electric Corporation, in conjunction with the Thermal Spray Laboratory of the State University of New York, Stony Brook, investigated the fabrication of a gas-tight interconnect layer on a tubular solid oxide fuel cell with plasma arc spray deposition. The principal objective was to determine the process variables for the plasma spray deposition of an interconnect with adequate electrical conductivity and other desired properties. Plasma arc spray deposition is a process where the coating material in powder form is heated to or above its melting temperature, while being accelerated by a carrier gas stream through a high power electric arc. The molten powder particles are directed at the substrate, and on impact, form a coating consisting of many layers of overlapping, thin, lenticular particles or splats. The variables investigated were gun power, spray distance, powder feed rate, plasma gas flow rates, number of gun passes, powder size distribution, injection angle of powder into the plasma plume, vacuum or atmospheric plasma spraying, and substrate heating. Typically, coatings produced by both systems showed bands of lanthanum rich material and cracking with the coating. Preheating the substrate reduced but did not eliminate internal coating cracking. A uniformly thick, dense, adherent interconnect of the desired chemistry was finally achieved with sufficient gas- tightness to allow fabrication of cells and samples for measurement of physical and electrical properties. A cell was tested successfully at 1000{degree}C for over 1,000 hours demonstrating the mechanical, electrical, and chemical stability of a plasma-arc sprayed interconnect layer.

  8. Effect of Operating Parameters on a Dual-Stage High Velocity Oxygen Fuel Thermal Spray System

    NASA Astrophysics Data System (ADS)

    Khan, Mohammed N.; Shamim, Tariq

    2014-08-01

    High velocity oxygen fuel (HVOF) thermal spray systems are being used to apply coatings to prevent surface degradation. The coatings of temperature sensitive materials such as titanium and copper, which have very low melting points, cannot be applied using a single-stage HVOF system. Therefore, a dual-stage HVOF system has been introduced and modeled computationally. The dual-spray system provides an easy control of particle oxidation by introducing a mixing chamber. In addition to the materials being sprayed, the thermal spray coating quality depends to a large extent on flow behavior of reacting gases and the particle dynamics. The present study investigates the influence of various operating parameters on the performance of a dual-stage thermal spray gun. The objective is to develop a predictive understanding of various parameters. The gas flow field and the free jet are modeled by considering the conservation of mass, momentum, and energy with the turbulence and the equilibrium combustion sub models. The particle phase is decoupled from the gas phase due to very low particle volume fractions. The results demonstrate the advantage of a dual-stage system over a single-stage system especially for the deposition of temperature sensitive materials.

  9. Analysis of spray penetration and velocity dissipation for non-steady fuel injection

    SciTech Connect

    Harrington, D.L.

    1984-02-01

    The time histories of spray penetration and velocity for conditions corresponding to non-steady fuel injection in a piston-engine cylinder are described in detail. Regions of influence are established for numerous factors affecting the spray-tip velocity curve, including injection-system characteristics, aerodynamic drag, and in-cylinder air swirl. The necessity of excluding the initial region, which is dominated by injection-system characteristics, from a generalized correlation is shown. Based on extensive experimental data, a universal curve of velocity versus penetration is then developed for the time domain in which the spray-tip velocity is decreasing. For a power-law drag formulation, general relationships for velocity and penetration are developed for any velocity exponent, and current correlations from the literature are interpreted in terms of the resulting functions. The inadequacies of the mathematical forms of both current spray-penetration correlations and correlations based upon power-law drag are then illustrated, and guidelines for developing continuously-differentiable penetration relationships are presented. Utilizing multi-term functions to describe the universal curve, an internally consistent set of relationships for spray-tip penetration and velocity is derived.

  10. Duplex coating of electroless nickel and HVOF (high-velocity oxygen fuel) sprayed WC-Co

    NASA Astrophysics Data System (ADS)

    Jokinen, P.; Korpiola, K.; Mahiout, A.

    2000-06-01

    The porosity of thermal sprayed coatings is usually a problem when coatings are used in wet corrosion application. The porosity allows media to penetrate to the surface of the base material. Corrosion spreads rapidly and the coating loses contact with the substrate and delaminates. This problem can be initiated by impregnating different polymers into the pores. An alternative approach has been tested in the present work to prevent corrosion of cemented carbide coated carbon steel in wet corrosion environments. Carbon steel substrates were coated with a thin film of electroless nickel (electroless nickel plating) and then HVOF (High-Velocity Oxygen Fuel) sprayed with cemented carbide. Reference specimens without electroless nickel were sprayed at the same time. The microhardness of the specimens was measured and the coating structure examined using optical microscopy and X-ray diffractometry (XRD). The bond between the layers and the base material was examined by means of a bend test. A salt chamber test was also performed for the specimens. The structure of the electroless nickel layer was crystalline as a result of the HVOF spraying. There were no cracks in the nickel layer, if the layer was about 20 µm thick. According to the results of the bend test, the adhesion between coatings and substrate was good, and there was no difference between the duplex-coated specimen and the reference specimen. A sample with a thin nickel layer under an HVOF sprayed cemented carbide did not exhibit corrosion after 8 h in the salt chamber test.

  11. Use of Oriented Spray Nozzles to Set the Vapor-Air Flow in Rotary Motion in the Superspray Space of the Evaporative Chimney-Type Tower

    NASA Astrophysics Data System (ADS)

    Dobrego, K. V.; Davydenko, V. F.; Koznacheev, I. A.

    2016-01-01

    The present paper considers the problem of upgrading the thermal efficiency of chimney-type evaporative cooling towers due to the rotary motion of the vapor-air flow in the superspray space. To set the vapor-air flow in rotary motion, we propose to use the momentum of the sprayed water. It has been shown that the existing parameters of spray nozzles permit setting up to 30% of the water flow momentum in translatory motion, which is enough for changing considerably the aerodynamics of the vapor-air flow in the superspray space and improving the operation of the cooling tower. The optimal angle of axial inclination of the spray cone has been estimated. Recommendations are given and problems have been posed for engineering realization of the proposed technologies in a chimney-type cooling tower.

  12. Numerical Investigation of the Flow Dynamics and Evaporative Cooling of Water Droplets Impinging onto Heated Surfaces: An Effective Approach To Identify Spray Cooling Mechanisms.

    PubMed

    Chen, Jian-Nan; Zhang, Zhen; Xu, Rui-Na; Ouyang, Xiao-Long; Jiang, Pei-Xue

    2016-09-13

    Numerical investigations of the dynamics and evaporative cooling of water droplets impinging onto heated surfaces can be used to identify spray cooling mechanisms. Droplet impingement dynamics and evaporation are simulated using the presented numerical model. Volume-of-fluid method is used in the model to track the free surface. The contact line dynamics was predicted from a dynamic contact angle model with the evaporation rate predicted by a kinetic theory model. A species transport equation was solved in the gas phase to describe the vapor convection and diffusion. The numerical model was validated by experimental data. The physical effects including the contact angle hysteresis and the thermocapillary effect are analyzed to offer guidance for future numerical models of droplet impingement cooling. The effects of various parameters including surface wettability, surface temperature, droplet velocity, droplet size, and droplet temperature were numerically studied from the standpoint of spray cooling. The numerical simulations offer profound analysis and deep insight into the spray cooling heat transfer mechanisms.

  13. Effect of Moderate Air Flow on the Distribution of Fuel Sprays After Injection Cut-0ff

    NASA Technical Reports Server (NTRS)

    Rothrock, A M; Spencer, R C

    1935-01-01

    High-speed motion pictures were taken of fuel sprays with the NACA spray-photographic apparatus to study the distribution of the liquid fuel from the instant of injection cut-off until about 0.05 second later. The fuel was injected into a glass-walled chamber in which the air density was varied from 1 to 13 times atmospheric air density (0.0765 to 0.99 pound per cubic foot) and in which the air was at room temperature. The air in the chamber was set in motion by means of a fan, and was directed counter to the spray at velocities up to 27 feet per second. The injection pressure was varied from 2,000 to 6,000 pounds per square inch. A 0.20-inch single-orifice nozzle, an 0.008-inch single-orifice nozzle, a multiorifice nozzle, and an impinging-jets nozzle were used. The best distribution was obtained by the use of air and a high-dispersion nozzle.

  14. Analysis of a High Velocity Oxygen-Fuel (HVOF) thermal spray torch. Part 1, Numerical formulation

    SciTech Connect

    Oberkampf, W.L.; Talpallikar, M.

    1994-01-01

    The fluid and particle dynamics of a High Velocity Oxygen-Fuel (HVOF) torch are analyzed using computational fluid dynamic (CFD) techniques. The thermal spray device analyzed is similar to a Metco Diamond Jet torch with powder injection. The spray nozzle is axisymmetric with powder injection on the centerline, premixed fuel and oxygen fed from an annulus, and air cooling injected along the interior surface of the aircap. Choked flow conditions occur at the exit of the aircap and a supersonic, under-expanded jet develops externally. The CFD simulation assumes three injection streams (solid metal particles with argon as a carrier gas, premixed oxygen/fuel, and air) inside the aircap and solves the combusting two-phase flow until the external spray stream decays to sonic conditions. The numerical formulation solves the mass, momentum, and energy transfer for both the gas and particle phase and strongly couples each phase. The combustion process is modeled using approximate equilibrium chemistry with dissociation of the gas with a total of nine species. Melting and re-solidification of the metal panicles is modeled as a lumped-mass system. Turbulent flow is modeled by a two equation k-{epsilon} turbulence model, including compressibility effects on turbulent dissipation. A time iterative, implicit, finite volume numerical method is used to solve the partial differential equations. A companion paper [10] presents the results of the numerical simulation and gives a detailed discussion of the gas and panicle dynamics.

  15. Transition region ignition characteristics of n-heptane fuel sprays

    NASA Technical Reports Server (NTRS)

    Danis, A. M.; Cernansky, N. P.; Namer, I.

    1985-01-01

    Ignition studies were perferred on monodisperse n-heptane sprays at atmospheric pressure over a range of equivalence ratios and droplet diameters. A capacitive discharge spark ignition system was used as the ignition source, providing independent control of spark energy and duration. Preliminary measurements were made to optimize spark duration and spark gap, optimum conditions being those at which the maximum frequency or probability of ignition was observed. The effect of spark duration on ignition frequency for several spark energies was determined for equivalence ratios of 0.5 and 1.0 and initial droplet diameters of 28 and 68 microns. Spark duration had little effect on ignition frequency over the entire 15 to 170 mu s range examined. Spark durations of 70 to 80 mu s were used for all subsequent work. The spark gap was optimized at equivalence ratios of 0.6, 0.8 and 1.0 and initial droplet diameters of 30, 40, 50, 60 and 70 microns by varying the electrode spacing from 0.5 to 5.0 mm while maintaining a constant spark energy. The optimum gap was determined to be 3.0 mm for nearly all conditions.

  16. Investigation of the spray characteristics for a secondary fuel injection nozzle using a digital image processing method

    NASA Astrophysics Data System (ADS)

    Jeong, Haeyoung; Lee, Kihyung; Ikeda, Yuji

    2007-05-01

    There are many ways to reduce diesel engine exhaust emissions. However, NOx emission is difficult to reduce because the hydrocarbon (HC) concentration in a diesel engine is not sufficient for NOx conversion. Therefore, in order to create stoichiometric conditions in the De-NOx catalyst, a secondary injection system is designed to inject liquid HC into the exhaust pipe. The atomization and distribution characteristics of the HC injected from a secondary injector are key technologies to obtain a high NOx conversion because inhomogeneous droplets of injected HC cause not only high fuel consumption but also deterioration of NOx emission. This paper describes the spray characteristics of a secondary injector including the spray angle, penetration length and breakup behaviour of the spray to optimize the reduction rate of the NOx catalyst. In this study, various optical diagnostics were applied to investigate these spray characteristics, the atomization mechanism and spray developing process. The visualization and image processing method for the spray pulsation were developed by high speed photography. The influence of the fuel supply pressure on the spray behaviour and a more detailed spray developing process have been analysed experimentally using image processing. Finally, the experimental results were used to correlate the spray structure to the injection system performance and to provide a design guide for a secondary injector nozzle.

  17. Fuel retention in impurity seeded discharges in JET after Be evaporation

    NASA Astrophysics Data System (ADS)

    Brezinsek, S.; Loarer, T.; Krieger, K.; Jachmich, S.; Tsalas, M.; Coffey, I.; Esser, H. G.; Eich, T.; Fundamenski, W.; Giroud, C.; Grünhagen, S.; Huber, A.; Kruezi, U.; Knipe, S.; Maddison, G. P.; McCormick, K.; Meigs, A. G.; Morgan, Ph.; Philipps, V.; Sergienko, G.; Stagg, R.; Stamp, M. F.; Tabares, F. L.; EFDA Contributors, JET

    2011-07-01

    Preparatory experiments for the ITER-Like Wall in JET were carried out to simulate the massive Be first wall by a thin Be layer, induced by evaporation of about 2.0 g Be, and to study its impact on fuel retention and divertor radiation with reduced C content and N seeding. Residual gas analysis reveals a reduction of hydrocarbons by one order of magnitude and of O by a factor of 5 in the partial pressure owing to the evaporation. The evolution of wall conditions, impurity fluxes and divertor radiation have been studied in ELMy H-mode plasmas (Bt = 2.7 T, Ip = 2.5 MA, Paux = 16 MW) whereas a non-seeded reference discharge was executed prior to the evaporation. The in situ measured Be flux at the midplane increased by about a factor of 40 whereas the C flux decreased by ~50% in the limiter phase of the first discharge with respect to the reference, but erosion of the Be layer and partial coverage with C takes place quickly. To make best use of the protective Be layer, only the first four discharges were employed for a gas balance analysis providing a D retention rate of 1.94 × 1021 D s-1 which is comparable to rates with C walls. But the Be evaporation provides a non-saturated surface with respect to D and short term retention is not negligible in the balance; the measured retention is overestimated with respect to steady-state conditions like that of the ILW. Moreover, C was only moderately reduced and co-deposition of fuel with eroded Be and C occurs. The lower C content leads to a minor reduction in divertor radiation as the reference phase prior to seeding indicates. N adds to the radiation of D and the remaining C, and the N content rises due to the legacy effect which has been quantified by gas balance to be 30% of the injected N. C radiation increases with exposure time, and both contributors cause an increase in the radiated fraction in the divertor from 50% to 70%. The radiation pattern suggests that N dominates the increase in the first discharges though C

  18. Ultrafast high-repetition imaging of fuel sprays using picosecond fiber laser.

    PubMed

    Purwar, Harsh; Wang, Hongjie; Tang, Mincheng; Idlahcen, Saïd; Rozé, Claude; Blaisot, Jean-Bernard; Godin, Thomas; Hideur, Ammar

    2015-12-28

    Modern diesel injectors operate at very high injection pressures of about 2000 bar resulting in injection velocities as high as 700 m/s near the nozzle outlet. In order to better predict the behavior of the atomization process at such high pressures, high-resolution spray images at high repetition rates must be recorded. However, due to extremely high velocity in the near-nozzle region, high-speed cameras fail to avoid blurring of the structures in the spray images due to their exposure time. Ultrafast imaging featuring ultra-short laser pulses to freeze the motion of the spray appears as an well suited solution to overcome this limitation. However, most commercial high-energy ultrafast sources are limited to a few kHz repetition rates. In the present work, we report the development of a custom-designed picosecond fiber laser generating ∼ 20 ps pulses with an average power of 2.5 W at a repetition rate of 8.2 MHz, suitable for high-speed imaging of high-pressure fuel jets. This fiber source has been proof tested by obtaining backlight images of diesel sprays issued from a single-orifice injector at an injection pressure of 300 bar. We observed a consequent improvement in terms of image resolution compared to standard white-light illumination. In addition, the compactness and stability against perturbations of our fiber laser system makes it particularly suitable for harsh experimental conditions.

  19. Evaluation of phase doppler particle analyzer for measuring dense sprays from a gas turbine fuel injector

    SciTech Connect

    Kraemer, G.; Bachalo, W.D.

    1986-01-01

    An experimental investigation was conducted to evaluate the suitability of the Phase Doppler Particle Analyzer (PDPA) for measuring sprays produced by fuel injectors. The instrument was subjected to several tests at simulated spray and combustion chamber operating conditions. Light beam attenuations produced by contaminated windows and optical-path length through the spray were insignificant sources of error. Off-axis forward and off-axis back scatter measurements were made and demonstrated good agreement. As expected, increased laser power was required for the back scatter measurements. Line averaged measurements of the Sauter Mean Diameter (SMD) were determined and compared to Fraunhofer diffraction measurements. The results were in agreement to within 5 percent. Although the instrument has a relatively large dynamic range of 35, size distributions at different ranges needed to be combined to cover the very large size ranges produced by the injector operating at off design conditions. Simultaneous drop size, velocity, and number density measurements produced by the instrument provide the information needed for combustor development and modeling of the air-fuel mixing processes.

  20. Monitoring of fuel consumption and aromatics formation in a kerosene spray flame as characterized by fluorescence spectroscopy.

    PubMed

    Allouis, C; Apicella, B; Barbella, R; Beretta, F; Ciajolo, A; Tregrossi, A

    2003-06-01

    The large presence of aromatic compounds in distillate fossil fuels should allow, in line of principle, to follow the fuel consumption and/or the presence of unburned fuel in a high temperature environment like a burner or the exhaust of combustion systems by exploiting the high fluorescence emission of aromatic fuel components. To this aim an UV-excited fluorescence source has to be used since the aromatic fuel components are strongly fluorescing in the UV region of the emission spectrum. In this work UV-excited laser induced fluorescence (LIF) diagnostics was applied to spray flames of kerosene in order to follow the fuel consumption and the formation of aromatic species. A strong UV signal was detected in the spray region of the flame that presented a shape similar to that found in the LIF spectra preliminary measured on the cold spray and in the room-temperature fluorescence of fuel solutions. The decrease of UV signal along the spray flame region was associated to the consumption of the fuel, but more difficult seems to be the attribution of a broad visible emission, that is present downstream of the flame. The visible emission feature could be assigned to flame-formed PAH species contained in the high molecular weight species, hypothesizing that their fluorescence spectra are shifted toward the visible for effect of the high temperature flame environment.

  1. 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.

  2. Imaging of Droplets and Vapor Distributions in a Diesel Fuel Spray by Means of a Laser Absorption Scattering Technique

    NASA Astrophysics Data System (ADS)

    Zhang, Yu-Yin; Yoshizaki, Takuo; Nishida, Keiya

    2000-11-01

    The droplets and vapor distributions in a fuel spray were imaged by a dual-wavelength laser absorption scattering technique. 1,3-dimethylnaphthalene, which has physical properties similar to those of Diesel fuel, strongly absorbs the ultraviolet light near the fourth harmonic (266 nm) of a Nd:YAG laser but is nearly transparent to the visible light near the second harmonic (532 nm) of a Nd:YAG laser. Therefore, droplets and vapor distributions in a Diesel spray can be visualized by an imaging system that uses a Nd:YAG laser as the incident light and 1,3-dimethylnaphthalene as the test fuel. For a quantitative application consideration, the absorption coefficients of dimethylnapthalene vapor at different temperatures and pressures were examined with an optical spectrometer. The findings of this study suggest that this imaging technique has great promise for simultaneously obtaining quantitative information of droplet density and vapor concentration in Diesel fuel spray.

  3. Imaging of droplets and vapor distributions in a diesel fuel spray by means of a laser absorption-scattering technique.

    PubMed

    Zhang, Y Y; Yoshizaki, T; Nishida, K

    2000-11-20

    The droplets and vapor distributions in a fuel spray were imaged by a dual-wavelength laser absorption-scattering technique. 1,3-dimethylnaphthalene, which has physical properties similar to those of Diesel fuel, strongly absorbs the ultraviolet light near the fourth harmonic (266 nm) of a Nd:YAG laser but is nearly transparent to the visible light near the second harmonic (532 nm) of a Nd:YAG laser. Therefore, droplets and vapor distributions in a Diesel spray can be visualized by an imaging system that uses a Nd:YAG laser as the incident light and 1,3-dimethylnaphthalene as the test fuel. For a quantitative application consideration, the absorption coefficients of dimethylnapthalene vapor at different temperatures and pressures were examined with an optical spectrometer. The findings of this study suggest that this imaging technique has great promise for simultaneously obtaining quantitative information of droplet density and vapor concentration in Diesel fuel spray.

  4. A comparative study of high velocity oxygen fuel, vacuum plasma spray, and axial plasma spray for the deposition of CoNiCrAlY bond coat alloy

    NASA Astrophysics Data System (ADS)

    Scrivani, A.; Bardi, U.; Carrafiello, L.; Lavacchi, A.; Niccolai, F.; Rizzi, G.

    2003-12-01

    In the aerospace field as well as in the stationary gas turbine field, thermally sprayed coatings are used to improve the surface properties of nickel-super-alloys materials. Coatings are commonly used as bond coat and antioxidation materials (mainly MCrAlY alloys) and as thermal barrier coatings (mainly yttria partially stabilized zirconia). The purpose of the current study was to assess the properties of thermally sprayed bond coat CoNiCrAlY alloys comparing the performance of three different techniques: vacuum plasma spray (VPS), high velocity oxygen fuel (HVOF), and axial plasma spray (AxPS). The quality of the deposited films has been assessed and compared from the point of view of microstructural (porosity, oxide concentration, unmelted particles presence) and mechanical (hardness) characteristics. The surface composition and morphology of the coatings were also determined. Specific efficiency tests were performed for the three examined technologies. The highest quality coatings are obtained by VPS, but also high velocity oxygen fuel and AxPS sprayed films have interesting properties, which can make their use interesting for some applications.

  5. A Numerical Study on Gas Phase Dynamics of High-Velocity Oxygen Fuel Thermal Spray

    NASA Astrophysics Data System (ADS)

    Baik, Jae-Sang; Park, Sun-Kyu; Kim, Youn-Jea

    2008-08-01

    The high-velocity oxygen fuel (HVOF) thermal spray is used for a particulate deposition process in which micro-sized particles are propelled and heated in a supersonic combusting gas stream. It is characterized by high gas velocity and high density and is being used in an increasing variety of coating applications, such as ceramic and composite coatings, to improve wear and abrasion resistance. The particle temperature and velocity are two of the most important parameters in HVOF thermal spraying, which affect the quality of the coatings. To understand the particle dynamics, it is necessary to study, first, the thermal flow characteristics in the HVOF system. In this study, a numerical analysis is performed to predict the gas dynamic behaviors, and the effect of the geometrical parameter is studied to optimize the nozzle design.

  6. Flame structure of wall-impinging diesel fuel sprays injected by group-hole nozzles

    SciTech Connect

    Gao, Jian; Moon, Seoksu; Nishida, Keiya; Matsumoto, Yuhei; Zhang, Yuyin

    2009-06-15

    This paper describes an investigation of the flame structure of wall-impinging diesel sprays injected by group-hole nozzles in a constant-volume combustion vessel at experimental conditions typical of a diesel engine. The particular emphasis was on the effect of the included angle between two orifices (0-15 deg. in current study) on the flame structure and combustion characteristics under various simulated engine load conditions. The laser absorption scattering (LAS) technique was applied to analyze the spray and mixture properties. Direct flame imaging and OH chemiluminescence imaging were utilized to quantify the ignition delay, flame geometrical parameters, and OH chemiluminescence intensity. The images show that the asymmetric flame structure emerges in wall-impinging group-hole nozzle sprays as larger included angle and higher engine load conditions are applied, which is consistent with the spray shape observed by LAS. Compared to the base nozzle, group-hole nozzles with large included angles yield higher overall OH chemiluminescence intensity, wider flame area, and greater proportion of high OH intensity, implying the better fuel/air mixing and improved combustion characteristics. The advantages of group-hole nozzle are more pronounced under high load conditions. Based on the results, the feasibility of group-hole nozzle for practical direct injection diesel engines is also discussed. It is concluded that the asymmetric flame structure of a group-hole nozzle spray is favorable to reduce soot formation over wide engine loads. However, the hole configuration of the group-hole nozzle should be carefully considered so as to achieve proper air utilization in the combustion chamber. Stoichiometric diesel combustion is another promising application of group-hole nozzle. (author)

  7. Computational fluid dynamic analysis of a High-Velocity Oxygen-Fuel (HVOF) thermal spray torch

    SciTech Connect

    Hassan, B.; Oberkampf, W.L.; Neiser, R.A.; Roemer, T.J.

    1995-09-01

    The gas dynamics of a High-Velocity Oxygen-Fuel (HVOF) torch are analyzed using computational fluid dynamics (CFD) techniques. The thermal spray device analyzed is similar to a Metco Diamond Jet torch with powder feed. The injection nozzle is assumed to be axisymmetric with premixed fuel and oxygen fed from an annulus, and air cooling injected along the interior surface of the aircap. The aircap, a cronically converging nozzle, achieves choked flow conditions at the exit and a supersonic, under-expanded jet develops externally. Finite difference equations for mass, momentum, and energy conservation are solved for the gas dynamics. The combustion process is modeled using a single-step and a 12-step quasi-global finite-rate chemistry model with dissociation of the gas and a total of nine species. Turbulent flow inside the aircap and in the free-jet decay is modeled using a two-equation k-{epsilon} model. An iterative, implicit, finite volume numerical method is used to solve the gas dynamic equations inside and outside the torch . The CFD results are compared with recent experimental measurements of pressure inside the HVOF aircap. Comparisons are made for two flow rates of premixed fuel and oxygen and air cooling. This paper presents the first published comparisons of CFD predictions and experimental measurements for HVOF tbermal spraying.

  8. Synchronized droplet size measurements for Coal-Water-Slurry (CWS) diesel sprays of an electronically-controlled fuel injection system

    NASA Astrophysics Data System (ADS)

    Kihm, K. D.; Terracina, D. P.; Payne, S. E.; Caton, J. A.

    Experiments were completed to study intermittent coal-water slurry (CWS) fuel sprays injected from an electronically-controlled accumulator injector system. A laser diffraction particle analyzing (LDPA) technique was used to measure the spray diameters (Sauter mean diameter, SMD) assuming the Rosin-Rammler two parameter model. In order to ensure an accurate synchronization of the measurement with the intermittent sprays, a new synchronization technique was developed using the light extinction signal as a triggering source for the data taking initiation. This technique allowed measurement of SMD's near the spray tip where the light extinction was low and the data were free from the multiscattering bias. Coal-water slurry fuel with 50% coal loading in mass containing 5 (mu)m mass median diameter coal particulates was considered. Injection pressures ranging from 28 to 110 MPa, two different nozzle orifice diameters, 0.2 ad 0.4 mm, and four axial measurement locations from 60 to 120 mm from the nozzle orifice were studied. Measurements were made for pressurized (2.0 MPa in gauge) and for ambient chamber conditions. The spray SMD showed an increase with the distance of the axial measurement location and with the ambient gas density, and showed a decrease with increasing injection pressure. A correlation of the Sauter mean diameter with the injection conditions was determined. The results were also compared with previous SMD correlations that were available only for diesel fuel sprays.

  9. Synchronized droplet size measurements for coal-water-slurry (CWS) diesel sprays of an electronically-controlled fuel injection system

    SciTech Connect

    Kihm, K.D.; Terracina, D.P.; Payne, S.E.; Caton, J.A.

    1993-12-31

    Experiments were completed to study intermittent coal-water slurry (CWS) fuel sprays injected from an electronically-controlled accumulator injector system. A laser diffraction particle analyzing (LDPA) technique was used to measure the spray diameters (Sauter mean diameter, SMD) assuming the Rosin-Rammler two parameter model. In order to ensure an accurate synchronization of the measurement with the intermittent sprays, a new synchronization technique was developed using the light extinction signal as a triggering source for the data taking initiation. This technique allowed measurement of SMDs near the spray tip where the light extinction was low and the data were free from the multiscattering bias. Coal-water slurry fuel with 50% coal loading in mass containing 5 {mu}m mass median diameter coal particulates was considered. Injection pressures ranging from 28 to 110 MPa, two different nozzle orifice diameters, 0.2 ad 0.4 mm, and four axial measurement locations from 60 to 120 mm from the nozzle orifice were studied. Measurements were made for pressurized (2.0 MPa in gauge) and for ambient chamber conditions. The spray SMD showed an increase with the distance of the axial measurement location and with the ambient gas density, and showed a decrease with increasing injection pressure. A correlation of the Sauter mean diameter with the injection conditions was determined. The results were also compared with previous SMD correlations that were available only for diesel fuel sprays.

  10. Physical properties, evaporation and combustion characteristics of nanofluid-type fuels

    NASA Astrophysics Data System (ADS)

    Tanvir, Saad

    existing literature. Additionally, a droplet collision experiment was developed to understand the collision characteristics of nanofluids fuels, especially the effect of particle addition on collision regimes. It was found that as particle concentration increases, coalescence was seen over a wider the range of Webber numbers and collision parameters as compared to pure liquids. Enhancement in surface tension at room temperature conditions is hypothesized to be the main factor causing this shift. A primary goal of this study is to understand how particle addition impacts the combustion behavior of liquid fuels. A droplet stream flame was used to measure the burning rate of ethanol droplets with the addition of aluminum (80nm) and graphite nanoparticles (50nm and 100nm). Results indicate that as particle concentration is increased, the burning rate of the resulting nanofluid droplet also increases. The maximum enhancement of 140 % was observed with the addition of 3 wt.% 80nm aluminum nanoparticles. The burning rate enhancement is mainly attributed to the strong radiation absorption by the nanofluid fuels from the flame. Computational models were developed to determine the ratio of radiation retention by the entire depth of the fluid (volumetric absorptivity) using optical properties of both the particles and the fluid. Furthermore, the penetration of radiation within the nanofluid was quantified using the well-known Monte Carlo algorithm. Results indicate that radiation absorption by the hybrid droplet does play a role in the enhancement of burning rate. More importantly, the absorption is not uniform within the hybrid droplet. It is localized in the region near the droplet surface, promoting localized boiling. This mechanism is believed to be responsible for the observed increase in burning rate. An experimental as well as numerical investigation on the evaporation characteristics of nanofluid fuels was conducted. The present study aims to determine the contribution of

  11. Oxides of Nitrogen Emissions from the Combustion of Monodisperse Liquid Fuel Sprays. Ph.D. Thesis

    NASA Technical Reports Server (NTRS)

    Sarv, H.

    1985-01-01

    A study of NO sub x formation in a one dimensional monodisperse spray combustion system, which allowed independent droplet size variation, was conducted. Temperature, NO and NO sub x concentrations were measured in the transition region, encompassing a 26 to 74 micron droplet size range. Emission measurements of hydrocarbons, carbon monoxide, carbon dioxide and oxygen were also made. The equivalence ratio was varied between 0.8 and 1.2 for the fuels used, including methanol, isopropanaol, n-heptane and n-octane. Pyridine and pyrrole were added to n-heptane as nitrogen-containing additives in order to simulate synthetic fuels. Results obtained from the postflame regions using the pure fuels indicate an optimum droplet size in the range of 43 to 58 microns for minimizing NO sub x production. For the fuels examined, the maximum NO sub x reductions relative to the small droplet size limit were about 10 to 20% for lean and 20 to 30% for stoichiometric and rich mixtures. This behavior is attributed to droplet interactions and the transition from diffusive to premixed type of burning. Preflame vaporization controls the gas phase stoichiometry which has a significant effect on the volume of the hot gases surrounding a fuel droplet, where NO sub x is formed.

  12. Electrostatic fuel atomization and spray-dispersal demonstration. Final report, September 1989-January 1990

    SciTech Connect

    Kelly, A.J.

    1990-07-01

    The purpose of this work is to characterize charged spray plumes, test the validity of existing spray/plume models, provide a basis for evaluating these plumes for gas turbine fuel and ignitor systems service. Plumes generated by a charge injection atomizer in nitrogen (< or = bar, absolute) have been analyzed using an Aerometrics Phase Doppler Particle Analyzer (PDPA). A 10 bar the outer, small droplet sheath is characterized by a Sauter mean diameter (D32) of about 55 microns, a span of about 0.7 and a number median of about 20 microns. The inner, large droplet core is characterized by D32 about = 110 microns and the same span. These data conform to a predicted overall droplet size distribution exhibiting a polydispersed profile: primary peak at about 105 microns, and secondary peaks at about 85 and 135 microns. The peaks are associated with the core region; the near constant profile below about 85 microns is characteristic of the sheath. Contrary to prediction, D32 increased modestly with pressure in these tests due to two factors: output charge density levels remained fixed with increasing pressure due to shortening of the sprayer caused by droplets stagnating in the test chamber; and, the predictable, lateral plume core expansion to the probe sampling position. A modest air flow over the spray unit corrects these problems.

  13. Prediction of the structure of fuel sprays in gas turbine combustors

    NASA Technical Reports Server (NTRS)

    Shuen, J.-S.

    1986-01-01

    The structure of fuel sprays in a combustion chamber is theoretically investigated using computer models of current interest. Three representative spray models are considered: (1) a locally homogeneous flow (LHF) model, which assumes infinitely fast interphase transport rates; (2) a deterministic separated flow (DSF) model, which considers finite rates of interphase transport but ignores effects of droplet/turbulence interactions; and (3) a stochastic separated flow (SSF) model, which considers droplet/turbulence interactions using random sampling for turbulence properties in conjunction with random-walk computations for droplet motion and transport. Two flow conditions are studied to investigate the influence of swirl on droplet life histories and the effects of droplet/turbulence interactions on flow properties. Comparison of computed results with the experimental data show that general features of the flow structure can be predicted with reasonable accuracy using the two separated flow models. In contrast, the LHF model overpredicts the rate of development of the flow. While the SSF model provides better agreement with measurements than the DSF model, definitive evaluation of the significance of droplet/turbulence interaction is not achieved due to uncertainties in the spray initial conditions.

  14. Prediction of the structure of fuel sprays in gas turbine combustors

    NASA Technical Reports Server (NTRS)

    Shuen, J. S.

    1985-01-01

    The structure of fuel sprays in a combustion chamber is theoretically investigated using computer models of current interest. Three representative spray models are considered: (1) a locally homogeneous flow (LHF) model, which assumes infinitely fast interphase transport rates; (2) a deterministic separated flow (DSF) model, which considers finite rates of interphase transport but ignores effects of droplet/turbulence interactions; and (3) a stochastic separated flow (SSF) model, which considers droplet/turbulence interactions using random sampling for turbulence properties in conjunction with random-walk computations for droplet motion and transport. Two flow conditions are studied to investigate the influence of swirl on droplet life histories and the effects of droplet/turbulence interactions on flow properties. Comparison of computed results with the experimental data show that general features of the flow structure can be predicted with reasonable accuracy using the two separated flow models. In contrast, the LHF model overpredicts the rate of development of the flow. While the SSF model provides better agreement with measurements than the DSF model, definitive evaluation of the significance of droplet/turbulence interaction is not achieved due to uncertainties in the spray initial conditions.

  15. Evaporation of Droplets in Plasma Spray-Physical Vapor Deposition Based on Energy Compensation Between Self-Cooling and Plasma Heat Transfer

    NASA Astrophysics Data System (ADS)

    Liu, Mei-Jun; Zhang, Meng; Zhang, Qiang; Yang, Guan-Jun; Li, Cheng-Xin; Li, Chang-Jiu

    2017-08-01

    In the plasma spray-physical vapor deposition process (PS-PVD), there is no obvious heating to the feedstock powders due to the free molecular flow condition of the open plasma jet. However, this is in contrast to recent experiments in which the molten droplets are transformed into vapor atoms in the open plasma jet. In this work, to better understand the heating process of feedstock powders in the open plasma jet of PS-PVD, an evaporation model of molten ZrO2 is established by examining the heat and mass transfer process of molten ZrO2. The results reveal that the heat flux in PS-PVD open plasma jet (about 106 W/m2) is smaller than that in the plasma torch nozzle (about 108 W/m2). However, the flying distance of molten ZrO2 in the open plasma jet is much longer than that in the plasma torch nozzle, so the heating in the open plasma jet cannot be ignored. The results of the evaporation model show that the molten ZrO2 can be partly evaporated by self-cooling, whereas the molten ZrO2 with a diameter <0.28 μm and an initial temperature of 3247 K can be completely evaporated within the axial distance of 450 mm by heat transfer.

  16. Application of digital image analysis techniques to antimisting fuel spray characterization

    NASA Technical Reports Server (NTRS)

    Fleeter, R.; Toaz, R.; Sarohia, V.

    1982-01-01

    Pulsed ruby laser sheet illumination of the spray is used for the initial recording of data on very-high-resolution photographic film. The digitization of mosaic elements is effected with a vidicon and video digitizer whose output is stored in computer RAM memory for processing. Highly nonspherical elements and a broad range of drop diameters (8-2000 microns) resulting from the unusual rheological properties of the fuel-additive system are accommodated by the device configuration and algorithms. It is found that the generation of two-dimensional images by means of scattered light also eliminates errors resulting from variations in the index of refraction and from the submicron scattering sites that are often present within the modified fuel. No a priori information on the drop size distribution or on the system response to various drop sizes is required.

  17. Effects of fuel cetane number on the structure of diesel spray combustion: An accelerated Eulerian stochastic fields method

    NASA Astrophysics Data System (ADS)

    Jangi, Mehdi; Lucchini, Tommaso; Gong, Cheng; Bai, Xue-Song

    2015-09-01

    An Eulerian stochastic fields (ESF) method accelerated with the chemistry coordinate mapping (CCM) approach for modelling spray combustion is formulated, and applied to model diesel combustion in a constant volume vessel. In ESF-CCM, the thermodynamic states of the discretised stochastic fields are mapped into a low-dimensional phase space. Integration of the chemical stiff ODEs is performed in the phase space and the results are mapped back to the physical domain. After validating the ESF-CCM, the method is used to investigate the effects of fuel cetane number on the structure of diesel spray combustion. It is shown that, depending of the fuel cetane number, liftoff length is varied, which can lead to a change in combustion mode from classical diesel spray combustion to fuel-lean premixed burned combustion. Spray combustion with a shorter liftoff length exhibits the characteristics of the classical conceptual diesel combustion model proposed by Dec in 1997 (http://dx.doi.org/10.4271/970873), whereas in a case with a lower cetane number the liftoff length is much larger and the spray combustion probably occurs in a fuel-lean-premixed mode of combustion. Nevertheless, the transport budget at the liftoff location shows that stabilisation at all cetane numbers is governed primarily by the auto-ignition process.

  18. Some Factors Affecting the Reproducibility of Penetration and the Cut-Off of Oil Sprays for Fuel-injection Engines

    NASA Technical Reports Server (NTRS)

    Beardsley, E G

    1928-01-01

    This investigation was undertaken at the Langley Memorial Aeronautical Laboratory in connection with a general research on fuel-injection for aircraft. The purpose of the investigation was to determine the factors controlling the reproducibility of spray penetration and secondary discharges after cut-off. The development of single sprays from automatic injection valves was recorded by means of special high-speed photographic apparatus capable of taking 25 consecutive pictures of the moving spray at a rate of 4,000 per second. The effect of two types of injection valves, injection-valve tube length, initial pressure in the injection-valve tube, speed of the injection control mechanism, and time of spray cut-off, on the reproducibility of spray penetration, and on secondary discharges were investigated. It was found that neither type of injection valve materially affected spray reproducibility. The initial pressure in the injection-valve tube controlled the reproducibility of spray penetrations. An increase in the initial pressure or in the length of the injection-valve tube slightly increased the spray penetration within the limits of this investigation. The speed of the injection-control mechanism did not affect the penetration. Analysis of the results indicates that secondary discharges were caused in this apparatus by pressure waves initiated by the rapid opening of the cut-off valve. The secondary discharges were eliminated in this investigation by increasing the length of the injection-valve tube. (author)

  19. Cold spray deposition of Ti2AlC coatings for improved nuclear fuel cladding

    NASA Astrophysics Data System (ADS)

    Maier, Benjamin R.; Garcia-Diaz, Brenda L.; Hauch, Benjamin; Olson, Luke C.; Sindelar, Robert L.; Sridharan, Kumar

    2015-11-01

    Coatings of Ti2AlC MAX phase compound have been successfully deposited on Zircaloy-4 (Zry-4) test flats, with the goal of enhancing the accident tolerance of LWR fuel cladding. Low temperature powder spray process, also known as cold spray, has been used to deposit coatings ∼90 μm in thickness using powder particles of <20 μm. X-ray diffraction analysis showed the phase-content of the deposited coatings to be identical to the powders indicating that no phase transformation or oxidation had occurred during the coating deposition process. The coating exhibited a high hardness of about 800 HK and pin-on-disk wear tests using abrasive ruby ball counter-surface showed the wear resistance of the coating to be significantly superior to the Zry-4 substrate. Scratch tests revealed the coatings to be well-adhered to the Zry-4 substrate. Such mechanical integrity is required for claddings from the standpoint of fretting wear resistance and resisting wear handling and insertion. Air oxidation tests at 700 °C and simulated LOCA tests at 1005 °C in steam environment showed the coatings to be significantly more oxidation resistant compared to Zry-4 suggesting that such coatings can potentially provide accident tolerance to nuclear fuel cladding.

  20. Interior flow and near-nozzle spray development in a marine-engine diesel fuel injector

    NASA Astrophysics Data System (ADS)

    Hult, J.; Simmank, P.; Matlok, S.; Mayer, S.; Falgout, Z.; Linne, M.

    2016-04-01

    A consolidated effort at optically characterising flow patterns, in-nozzle cavitation, and near-nozzle jet structure of a marine diesel fuel injector is presented. A combination of several optical techniques was employed to fully transparent injector models, compound metal-glass and full metal injectors. They were all based on a common real-scale dual nozzle hole geometry for a marine two-stroke diesel engine. In a stationary flow rig, flow velocities in the sac-volume and nozzle holes were measured using PIV, and in-nozzle cavitation visualized using high-resolution shadowgraphs. The effect of varying cavitation number was studied and results compared to CFD predictions. In-nozzle cavitation and near-nozzle jet structure during transient operation were visualized simultaneously, using high-speed imaging in an atmospheric pressure spray rig. Near-nozzle spray formation was investigated using ballistic imaging. Finally, the injector geometry was tested on a full-scale marine diesel engine, where the dynamics of near-nozzle jet development was visualized using high-speed shadowgraphy. The range of studies focused on a single common geometry allows a comprehensive survey of phenomena ranging from first inception of cavitation under well-controlled flow conditions to fuel jet structure at real engine conditions.

  1. Coal-water slurry sprays from an electronically controlled accumulator fuel injection system: Break-up distances and times

    SciTech Connect

    Caton, J.A.; Payne, S.E.; Terracina, D.P.; Kihm, K.D.

    1993-12-31

    Experiments have been completed to characterize coal-water slurry sprays from an electronically-controlled accumulator fuel injection system of a diesel engine. The sprays were injected into a pressurized chamber equipped with windows. High speed movies, fuel pressures and needle lifts were obtained as a function of time, orifice diameter, coal loading, gas density in the chamber, and accumulator fuel pressure. For the base conditions (50% (by man) coal loading, 0.4 mm diameter nozzle hole, coal-water slurry pressure of 82 MPa (12,000 psi), and a chamber density of 25 kg/m{sup 3}), the break-up time was 0.30 ms. An empirical correlation for spray tip penetration, break-up time and initial jet velocity was developed. For the conditions of this study, the spray tip penetration and initial jet velocity were 15% greater for coal-water slurry than for diesel fuel or water. Results of this study and the correlation are specific to the tested coal-water slurry and are not general for other coal-water slurry fuels.

  2. 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.

  3. Solid oxide fuel cell electrolytes produced via very low pressure suspension plasma spray and electrophoretic deposition

    NASA Astrophysics Data System (ADS)

    Fleetwood, James D.

    Solid oxide fuel cells (SOFCs) are a promising element of comprehensive energy policies due to their direct mechanism for converting the oxidization of fuel, such as hydrogen, into electrical energy. Both very low pressure plasma spray and electrophoretic deposition allow working with high melting temperature SOFC suspension based feedstock on complex surfaces, such as in non-planar SOFC designs. Dense, thin electrolytes of ideal composition for SOFCs can be fabricated with each of these processes, while compositional control is achieved with dissolved dopant compounds that are incorporated into the coating during deposition. In the work reported, sub-micron 8 mole % Y2O3-ZrO2 (YSZ) and gadolinia-doped ceria (GDC), powders, including those in suspension with scandium-nitrate dopants, were deposited on NiO-YSZ anodes, via very low pressure suspension plasma spray (VLPSPS) at Sandia National Laboratories' Thermal Spray Research Laboratory and electrophoretic deposition (EPD) at Purdue University. Plasma spray was carried out in a chamber held at 320 - 1300 Pa, with the plasma composed of argon, hydrogen, and helium. EPD was characterized utilizing constant current deposition at 10 mm electrode separation, with deposits sintered from 1300 -- 1500 °C for 2 hours. The role of suspension constituents in EPD was analyzed based on a parametric study of powder loading, powder specific surface area, polyvinyl butyral (PVB) content, polyethyleneimine (PEI) content, and acetic acid content. Increasing PVB content and reduction of particle specific surface area were found to eliminate the formation of cracks when drying. PEI and acetic acid content were used to control suspension stability and the adhesion of deposits. Additionally, EPD was used to fabricate YSZ/GDC bilayer electrolyte systems. The resultant YSZ electrolytes were 2-27 microns thick and up to 97% dense. Electrolyte performance as part of a SOFC system with screen printed LSCF cathodes was evaluated with peak

  4. Properly synchronized measurements of droplet sizes for high-pressure intermittent coal-water slurry fuel sprays

    NASA Astrophysics Data System (ADS)

    Kihm, K. D.; Terracina, D. P.; Payne, S. E.; Caton, J. A.

    1993-11-01

    Experiments were completed to study intermittent coal-water slurry (CWS) fuel sprays injected from an electronically-controlled accumulator injector system. A new synchronization technique was developed using the light extinction signal as a triggering source for the data taking initiation with a laser diffraction particle analyzing (LDPA) technique. This technique allowed measurement of Sauter mean diameters (SMD's) near the spray tip where the light extinction was low and the data were free from the multiscattering bias. Coal-water slurry fuel with 50% coal loading in mass containing 5 micron mass median diameter coal particulates was considered. A correlation of the SMD with the injection conditions was determined which show a satisfactory agreement with the measured SMD data. The spray SMD showed an increase with the distance of the axial measurement location and with the ambient gas density and showed a decrease with increasing injection pressure.

  5. Energy and environmental research emphasizing low-rank coal: Task 5.7, Coal char fuel evaporation canister sorbent

    SciTech Connect

    Aulich, T.R.; Grisanti, A.A.; Knudson, C.L.

    1995-08-01

    Atomobile evaporative emission canisters contain activated carbon sorbents that trap and store fuel vapors emitted from automobile fuel tanks during periods of hot ambient temperatures and after engine operation. When a vehicle is started, combustion air is pulled through the canister, and adsorbed vapors are removed from the sorbent and routed to the intake manifold for combustion along with fuel from the tank. The two primary requirements of an effective canister sorbent are that (1) it must be a strong enough adsorbent to hold on to the fuel vapors that contact it and (2) it must be a weak enough adsorbent to release the captured vapors in the presence of the airflow required by the engine for fuel combustion. Most currently available commercial canister sorbents are made from wood, which is reacted with phosphoric acid and heat to yield an activated carbon with optimum pore size for gasoline vapor adsorption. The objectives of Task 5.7 were to (1) design and construct a test system for evaluating the performance of different sorbents in trapping and releasing butane, gasoline, and other organic vapors; (2) investigate the use of lignite char as an automobile fuel evaporation canister sorbent; (3) compare the adsorbing and desorbing characteristics of lignite chars with those of several commercial sorbents; and (4) investigate whether the presence of ethanol in fuel vapors affects sorbent performance in any way. Tests with two different sorbents (a wood-derived activated carbon and a lignite char) showed that with both sorbents, ethanol vapor breakthrough took about twice as long as hydrocarbon vapor breakthrough. Possible reasons for this, including an increased sorbent affinity for ethanol vapors, will be investigated. If this effect is real (i.e., reproducible over an extensive series of tests under varying conditions), it may help explain why ethanol vapor concentrations in SHED test evaporative emissions are often lower than would be expected.

  6. Gas-phase saturation and evaporative cooling effects during wet compression of a fuel aerosol under RCM conditions

    SciTech Connect

    Goldsborough, S.S.; Johnson, M.V.; Zhu, G.S.; Aggarwal, S.K.

    2011-01-15

    Wet compression of a fuel aerosol has been proposed as a means of creating gas-phase mixtures of involatile diesel-representative fuels and oxidizer + diluent gases for rapid compression machine (RCM) experiments. The use of high concentration aerosols (e.g., {proportional_to}0.1 mL{sub fuel}/L{sub gas}, {proportional_to}1 x 10{sup 9} droplets/L{sub gas} for stoichiometric fuel loading at ambient conditions) can result in droplet-droplet interactions which lead to significant gas-phase fuel saturation and evaporative cooling during the volumetric compression process. In addition, localized stratification (i.e., on the droplet scale) of the fuel vapor and of temperature can lead to non-homogeneous reaction and heat release processes - features which could prevent adequate segregation of the underlying chemical kinetic rates from rates of physical transport. These characteristics are dependent on many factors including physical parameters such as overall fuel loading and initial droplet size relative to the compression rate, as well as fuel and diluent properties such as the boiling curve, vaporization enthalpy, heat capacity, and mass and thermal diffusivities. This study investigates the physical issues, especially fuel saturation and evaporative cooling effects, using a spherically-symmetric, single-droplet wet compression model. n-Dodecane is used as the fuel with the gas containing 21% O{sub 2} and 79% N{sub 2}. An overall compression time and compression ratio of 15.3 ms and 13.4 are used, respectively. It is found that smaller droplets (d{sub 0}{proportional_to} 2-3 {mu}m) are more affected by 'far-field' saturation and cooling effects, while larger droplets (d{sub 0}{proportional_to} 14 {mu}m) result in greater localized stratification of the gas-phase due to the larger diffusion distances for heat and mass transport. Vaporization of larger droplets is more affected by the volumetric compression process since evaporation requires more time to be completed

  7. Thermally Sprayed Large Tubular Solid Oxide Fuel Cells and Its Stack: Geometry Optimization, Preparation, and Performance

    NASA Astrophysics Data System (ADS)

    Zhang, Shan-Lin; Li, Cheng-Xin; Liu, Shuai; Li, Chang-Jiu; Yang, Guan-Jun; He, Peng-Jiang; Yun, Liang-Liang; Song, Bo; Xie, Ying-Xin

    2017-02-01

    In this study, we develop a large tubular solid oxide fuel cells design with several cells in series on a porous cermet support, which has many characteristics such as self-sealing, low Ohmic loss, high strength, and good thermal expansion coefficient matching. Here, we investigate aspects of the cell design, manufacture, performance, and application. Firstly, the cell length and number of cells in series are optimized by theoretical analysis. Then, thermal spraying is applied as a cost-effective method to prepare all the cell components. Finally, the performance of different types of cells and two types of stacks is characterized. The maximum output power of one tube, which had 20 cells in series, reaches 31 and 40.5 W at 800 and 900 °C, respectively. Moreover, the output power of a stack assembled with 56 tubes, each with ten cells in series, reaches 800 W at 830 °C. The excellent single tube and cell stack performance suggest that thermally sprayed tubular SOFCs have significant potential for commercialized application.

  8. Fabrication of solid oxide fuel cell anode electrode by spray pyrolysis

    NASA Astrophysics Data System (ADS)

    Liu, Lin; Kim, Gap-Yong; Chandra, Abhijit

    Large triple phase boundaries (TPBs) and high gas diffusion capability are critical in enhancing the performance of a solid oxide fuel cell (SOFC). In this study, ultrasonic spray pyrolysis has been investigated to assess its capability in controlling the anode microstructure. Deposition of porous anode film of nickel and Ce 0.9Gd 0.1O 1.95 on a dense 8 mol.% yttria stabilized zirconia (YSZ) substrate was carried out. First, an ultrasonic atomization model was utilized to predict the deposited particle size. The model accurately estimated the deposited particle size based on the feed solution condition. Second, effects of various process parameters, which included the precursor solution feed rate, precursor solution concentration and deposition temperature, on the TPB formation and porosity were investigated. The deposition temperature and precursor solution concentration were the most critical parameters that influenced the morphology, porosity and particle size of the anode electrode. Ultrasonic spray pyrolysis achieved homogeneous distribution of constitutive elements within the deposited particles and demonstrated capability to control the particle size and porosity in the range of 2-17 μm and 21-52%, respectively.

  9. Suspension High Velocity Oxy-Fuel (SHVOF)-Sprayed Alumina Coatings: Microstructure, Nanoindentation and Wear

    NASA Astrophysics Data System (ADS)

    Murray, J. W.; Ang, A. S. M.; Pala, Z.; Shaw, E. C.; Hussain, T.

    2016-12-01

    Suspension high velocity oxy-fuel spraying can be used to produce thermally sprayed coatings from powdered feedstocks too small to be processed by mechanical feeders, allowing formation of nanostructured coatings with improved density and mechanical properties. Here, alumina coatings were produced from submicron-sized feedstock in aqueous suspension, using two flame combustion parameters yielding contrasting microstructures. Both coatings were tested in dry sliding wear conditions with an alumina counterbody. The coating processed with high combustion power of 101 kW contained 74 wt.% amorphous phase and 26 wt.% crystalline phase (95 wt.% gamma and 3 wt.% alpha alumina), while the 72-kW coating contained lower 58 wt.% amorphous phase and 42 wt.% crystalline phases (73 wt.% was alpha and 26 wt.% gamma). The 101-kW coating had a dry sliding specific wear rate between 4 and 4.5 × 10-5 mm3/Nm, 2 orders of magnitude higher than the 72-kW coating wear rate of 2-4.2 × 10-7 mm3/Nm. A severe wear regime dominated by brittle fracture and grain pullout of the coating was responsible for the wear of the 101-kW coating, explained by mean fracture toughness three times lower than the 72-kW coating, owing to the almost complete absence of alpha alumina.

  10. Two-phase SLIPI for instantaneous LIF and Mie imaging of transient fuel sprays.

    PubMed

    Storch, Michael; Mishra, Yogeshwar Nath; Koegl, Matthias; Kristensson, Elias; Will, Stefan; Zigan, Lars; Berrocal, Edouard

    2016-12-01

    We report in this Letter a two-phase structured laser illumination planar imaging [two-pulse SLIPI (2p-SLIPI)] optical setup where the "lines structure" is spatially shifted by exploiting the birefringence property of a calcite crystal. By using this optical component and two cross-polarized laser pulses, the shift of the modulated pattern is not "time-limited" anymore. Consequently, two sub-images with spatially mismatched phases can be recorded within a few hundred of nanoseconds only, freezing the motion of the illuminated transient flow. In comparison with previous setups for instantaneous imaging based on structured illumination, the current optical design presents the advantage of having a single optical path, greatly simplifying its complexity. Due to its virtue of suppressing the effects from multiple light scattering, the 2p-SLIPI technique is applied here in an optically dense multi-jet direct-injection spark-ignition (DISI) ethanol spray. The fast formation of polydispersed droplets and appearance of voids after fuel injection are investigated by simultaneous detection of Mie scattering and liquid laser-induced fluorescence. The results allow for significantly improved analysis of the spray structure.

  11. Thermally Sprayed Large Tubular Solid Oxide Fuel Cells and Its Stack: Geometry Optimization, Preparation, and Performance

    NASA Astrophysics Data System (ADS)

    Zhang, Shan-Lin; Li, Cheng-Xin; Liu, Shuai; Li, Chang-Jiu; Yang, Guan-Jun; He, Peng-Jiang; Yun, Liang-Liang; Song, Bo; Xie, Ying-Xin

    2017-01-01

    In this study, we develop a large tubular solid oxide fuel cells design with several cells in series on a porous cermet support, which has many characteristics such as self-sealing, low Ohmic loss, high strength, and good thermal expansion coefficient matching. Here, we investigate aspects of the cell design, manufacture, performance, and application. Firstly, the cell length and number of cells in series are optimized by theoretical analysis. Then, thermal spraying is applied as a cost-effective method to prepare all the cell components. Finally, the performance of different types of cells and two types of stacks is characterized. The maximum output power of one tube, which had 20 cells in series, reaches 31 and 40.5 W at 800 and 900 °C, respectively. Moreover, the output power of a stack assembled with 56 tubes, each with ten cells in series, reaches 800 W at 830 °C. The excellent single tube and cell stack performance suggest that thermally sprayed tubular SOFCs have significant potential for commercialized application.

  12. Evaporation and burning of a spherical fuel droplet in a uniform convective flowfield

    SciTech Connect

    Madooglu, K.

    1992-01-01

    An analytical/numerical model is developed for the evaporation and burning of a spherical fuel droplet in a subsonic crossflow. The external gaseous flowfield is represented using an approximate compressible potential-flow solution, while the internal flowfield of the droplet is represented by the classical Hill's spherical vortex. This allows a numerical solution for the external boundary layer, from which the droplet's effective drag coefficent, rate of mass loss, size, and the shape of the diffusion flame with infinitely fast chemical reaction kinetics are determined. Subsequently, the quasi-steady model with uniform liquid temperature is extended to examine the effects of the transient heating of the droplet interior. Time-dependent calculations are performed with updated droplet Reynolds numbers and updated surface temperatures. Comparisons of model predictions with experimental data are made. To examine the effects of finite-rate chemical reaction kinetics, a one-step formulation of the combustion mechanism is integrated into the gaseous boundary layer equations. Simplifying assumptions for the variation of gas properties commonly used in combustion calculations, are subjected to an examination as to their degree of accuracy. For this purpose, the droplet model is extended to account for the variation of gas properties with temperature and gas composition within the boundary layer. Comparisons are made between the predictions obtained from the different models developed in this study, as well as with existing experimental data.

  13. Estimation of equivalence ratio distribution in diesel spray using a computational fluid dynamics

    NASA Astrophysics Data System (ADS)

    Suzuki, Yasumasa; Tsujimura, Taku; Kusaka, Jin

    2014-08-01

    It is important to understand the mechanism of mixing and atomization of the diesel spray. In addition, the computational prediction of mixing behavior and internal structure of a diesel spray is expected to promote the further understanding about a diesel spray and development of the diesel engine including devices for fuel injection. In this study, we predicted the formation of diesel fuel spray with 3D-CFD code and validated the application by comparing experimental results of the fuel spray behavior and the equivalence ratio visualized by Layleigh-scatter imaging under some ambient, injection and fuel conditions. Using the applicable constants of KH-RT model, we can predict the liquid length spray on a quantitative level. under various fuel injection, ambient and fuel conditions. On the other hand, the change of the vapor penetration and the fuel mass fraction and equivalence ratio distribution with change of fuel injection and ambient conditions quantitatively. The 3D-CFD code used in this study predicts the spray cone angle and entrainment of ambient gas are predicted excessively, therefore there is the possibility of the improvement in the prediction accuracy by the refinement of fuel droplets breakup and evaporation model and the quantitative prediction of spray cone angle.

  14. Spray atomization and combustion

    NASA Technical Reports Server (NTRS)

    Faeth, G. M.

    1986-01-01

    New theoretical and experimental methods for studying sprays are reviewed. Common methods to analyze dilute sprays are described and used to interpret recent measurements of the structure of dilute sprays and related dispersed turbulent jets. Particle-laden jets, nonevaporating, evaporating, and combusting sprays, and noncondensing and condensing bubbly jets are examined and used to initially evaluate current analytical methods for a wide range of conditions. Dense sprays are briefly discussed.

  15. Pulse Mitigation and Heat Transfer Enhancement Techniques. Volume 2. Effect of Surface Wettability and Roughness in Evaporative Spray Cooling

    DTIC Science & Technology

    1992-08-01

    below the Leidenfrost point. In this region, heat is removed predominantly due to liquid/vapor phase change where the liquid is supplied to the heated... Leidenfrost point resulting in a nonwetting condition. This research effort is directed towards developing an understanding of the basic phenomena... Leidenfrost point and was nonwetting. The rest of the surface was still in the wetting range because the spray characteristics were good. This caused the

  16. The N.A.C.A. Apparatus for Studying the Formation and Combustion of Fuel Sprays and the Results from Preliminary Tests

    NASA Technical Reports Server (NTRS)

    Rothrock, A M

    1931-01-01

    Described here is an apparatus for studying the formation and combustion of fuel sprays under conditions closely simulating those in a high speed compression-ignition engine. The apparatus consists of a single-cylinder modified test engine, a fuel injection system so designed that a single charge of fuel can be injected into the combustion chamber, an electric driving motor, and a high-speed photographic apparatus. The cylinder head of the engine has a vertical disk form of combustion chamber whose sides are glass windows. When the fuel is injected into the combustion chamber, motion pictures at the rate of 2000 per second are taken of the spray formation by means of spark discharges. When combustion takes place, the light of combustion is recorded on the same photographic film as the spray photographs. Included here are the results of some tests to determine the effect of air temperature, air flow, and nozzle design on the spray formation. The results show that the compression temperature has little effect on the penetration of the fuel spray, but does not affect the dispersion, that air velocities of about 300 feet per second are necessary to destroy the core of the spray, and that the effect of air flow on the spray is controlled to a certain extent by the design of the injection nozzle. The results on the combustion of the spray show that when ignition does not take place until after spray cut-off, the ignition may start almost simultaneously throughout the combustion chamber or at different points throughout the chamber. When ignition takes place before spray cut-off, the combustion starts around the edge of the spray and then spreads throughout the chamber.

  17. Deposition and properties of high-velocity-oxygen-fuel and plasma-sprayed Mo-Mo2C composite coatings

    NASA Astrophysics Data System (ADS)

    Prchlik, L.; Gutleber, J.; Sampath, S.

    2001-12-01

    Molybdenum thermal-spray coatings, dispersion strengthened by molybdenum oxides and molybdenum carbides, play an important role in industrial tribological applications. Traditionally, they have been prepared by plasma and wire flame spraying. High porosity and lower cohesion strength limit their application in situations where both galling and abrasion wear is involved. In this study, high-velocity-oxygen-fuel (HVOF) deposition of molybdenum and molybdenum carbide coatings was attempted. Deposition was achieved for all powders used. Composition, microstructure, mechanical, and wear properties of the HVOF synthesized coatings were evaluated and compared with plasma-sprayed counterparts. The HVOF coatings possessed a very good abrasion resistance, whereas plasma deposits performed better in dry sliding tests. Measurements showed a close relationship between the coating surface hardness and its abrasion resistance. Results also suggested correlation between molybdenum carbide distribution in the molybdenum matrix and the sliding friction response of Mo-Mo2C coatings.

  18. Investigation of evaporation and biodegradation of fuel spills in Antarctica. I. A chemical approach using GC-FID.

    PubMed

    Snape, Ian; Harvey, Paul McA; Ferguson, Susan H; Rayner, John L; Revill, Andrew T

    2005-12-01

    Little effort has been devoted to differentiating between hydrocarbon losses through evaporation and biodegradation in treatability studies of fuel-contaminated Antarctic soils. When natural attenuation is being considered as a treatment option, it is important to be able to identify the mechanism of hydrocarbon loss and demonstrate that rates of degradation are sufficient to prevent off-site migration. Similarly, where complex thermally enhanced bioremediation schemes involve nutrient addition, water management, air stripping and active heating, it is important to appreciate the relative roles of these mechanisms for cost minimisation. Following the loss of hydrocarbons by documenting changes in total petroleum hydrocarbons offers little insight into the relative contribution of evaporation and biodegradation. We present a methodology here that allows identification and quantification of evaporative losses of diesel range organics at a range of temperatures using successively less volatile compounds as fractionation markers. We also present data that supports the general utility of so-called biodegradation indices for tracking biodegradation progress. We are also able to show that at 4 degrees C indigenous Antarctic soil bacteria degrade Special Antarctic Blend fuel components in the following order: naphthalene and methyl-napthalenes, light n-alkanes, then progressively heavier n-alkanes; whereas isoprenoids and the unresolved complex mixture are relatively recalcitrant.

  19. Effect of pervaporation plate thickness on the rate of methanol evaporation in a passive vapor-feed direct methanol fuel cell

    NASA Astrophysics Data System (ADS)

    Fauzi, N. F. I.; Hasran, U. A.; Kamarudin, S. K.

    2015-09-01

    In a passive vapor-feed direct methanol fuel cell (DMFC), methanol vapor is typically obtained using a pervaporation plate in a process by which liquid methanol contained in the fuel reservoir undergoes a phase change to vapor in the anodic vapor chamber. This work investigates the effect of pervaporation plate thickness on the rate of methanol evaporation using a three-dimensional simulation model developed by varying the plate thickness. A. The rate of methanol evaporation was measured using Darcy's law. The rate of methanol evaporation was found to be inversely proportional to the plate thickness, where the decrease in thickness inevitably lowers the resistance along the plate and consequently increases the methanol transport through the plate. This shows that the plate thickness has a significant influence on the rate of methanol evaporation and thereby plays an important role in improving the performance of the passive vapor-feed direct methanol fuel cell.

  20. Numerical Investigation of Combustion and Flow Dynamics in a High Velocity Oxygen-Fuel Thermal Spray Gun

    NASA Astrophysics Data System (ADS)

    Wang, Xiaoguang; Song, Qiuzhi; Yu, Zhiyi

    2016-02-01

    The combustion and flow behavior within a high velocity oxygen-fuel (HVOF) thermal spray gun is very complex and involves multiphase flow, heat transfer, chemical reactions, and supersonic/subsonic transitions. Additionally, this behavior has a significant effect on the formation of a coating. Non-premixed combustion models have been developed and are able to provide insight into the underlying physics of the process. Therefore, this investigation employs a non-premixed combustion model and the SST k - ω turbulence model to simulate the flow field of the JP5000 (Praxair-TAFA, US) HVOF thermal spray gun. The predicted temperature and velocity have a high level of agreement with experimental data when using the non-premixed combustion model. The results are focused on the fuel combustion, the subsequent gas dynamics within the HVOF gun, and the development of a supersonic free jet outside the gun. Furthermore, the oxygen/fuel inlet turbulence intensity, the fuel droplet size, and the oxygen/fuel ratio are investigated to determine their effect on the supersonic flow characteristics of the combustion gas.

  1. Supersaturation produces high bioavailability of amorphous danazol particles formed by evaporative precipitation into aqueous solution and spray freezing into liquid technologies.

    PubMed

    Vaughn, Jason M; McConville, Jason T; Crisp, Matthew T; Johnston, Keith P; Williams, Robert O

    2006-06-01

    The bioavailability of high surface area danazol formulations was evaluated in a mouse model to determine what effect high supersaturation, as measured in vitro, has on the absorption of a poorly water soluble drug. Danazol, a biopharmaceutics classification system II (BCS II) compound, was used as the model drug. Evaporative precipitation into aqueous solution (EPAS) and spray freezing into liquid (SFL) technologies were used to prepare powders of danazol/PVP K-15 in a 1:1 ratio. The evaporative precipitation into aqueous solution (EPAS) and SFL compositions, physical mixture and commercial product were dosed by oral gavage to 28 male Swiss/ICR mice for each arm of the study. Samples were taken at time points ranging from 0.5 to 24 h. Pooled mouse serum was analyzed for danazol by high performance liquid chromatography (HPLC). Powders were analyzed for their ability to form supersaturated solutions through dissolution at concentrations of 1 mg/mL which was the dose delivered to the mouse models. Spray freezing into liquid (SFL) and EPAS compositions displayed higher C(max) at 392.5 ng/mL and 430.1 ng/mL, respectively, compared to the physical mixture (204.4 ng/mL) and commercially available danazol (199.3 ng/mL). The T(max) for all compositions studied was near the 1 h time point. The area under the curve (AUC) for the SFL composition was 2558 ng.h/mL compared to EPAS composition at 1534 ng.h/mL. The area under the curve (AUC) for the physical mixture and commercially available danazol were 672 ng.h/mL and 1519 ng.h/mL, respectively. The elimination rate constants for the EPAS composition, SFL composition, and physical mixture were similar at approximately 0.15 h(-1) where as the commercially available danazol capsules displayed an elimination rate constant of 0.103 h(-1). The extent of danazol absorption in the mouse model was higher for SFL composition compared to the less amorphous EPAS composition, physical mixture, and commercially available danazol powders

  2. Study of Electrostatic Modulation of Fuel Sprays to Enhance Combustion Performance in an Aviation Gas Turbine

    DTIC Science & Technology

    1987-06-01

    Electrostatic spraying has found practical application in such diverse areas as high- speed ink- jet printing , pesticide, paint and liquid metal... Electrohydrodynamically Sprayed Liquid Droplets," The Physics of Fluids, V. 10, pp. 2149-2154, October 1967. 8. Rayleigh, J. W. S., "On the Instability of Jets ...biock number) I ELD OGROUP SUB. GR. Electrohydrodynamic Spraying, Electrostatic f I Atomization, Gas Turbine Combustor, Combustion UTRACT (Continue

  3. Matching refractive indices of two fluids and finding interfacial tension for the purpose of fuel spray imaging

    NASA Astrophysics Data System (ADS)

    Liang, Y. H.

    2017-06-01

    This study attempts to prepare a fluid pair for use in spray dynamics investigations. Better understanding the behavior of fuel sprays is one of the things that can help improve the efficiency of internal combustion engines. To address the scattering issue in current imaging methods, the refractive index difference between the injected fluid and the medium that it is injected into is eliminated. Two immiscible fluids (sucrose solution and silicone oil) with the same refractive index was identified, their surface tension to build a model fluid engine system injection was also studied. At the same time, Weber number is found to help correct the difference. Results show that 63.7% mass sucrose solution has the same refractive index as silicone oil, and the sucrose solution/silicone oil interface has a surface tension of 0.08941 N/m, which is roughly four times larger than that of ethanol/air. This means using the sucrose/silicone oil fluid pair to model fuel spray will involve some adjustments to be accurate.

  4. Furnace endoscope—measuring fuel spray properties in hot and corrosive environments

    NASA Astrophysics Data System (ADS)

    Miikkulainen, P.; Kankkunen, A.; Järvinen, M. P.

    2004-12-01

    A furnace endoscope was developed to carry out in-furnace measurements of black liquor sprays in order to discover the initial velocity, opening angle and trajectory of the spray, and compare spray disintegration mechanisms and spray appearance with the ones measured in a spray chamber. An error analysis of the velocity measurement method was carried out, and the meaning of the optimum measurement distance from the optics to the observed object is discussed. Some details of the development process of the probe are also presented, especially the definition of the scale of the image and the cooling system of the protection tubes. The furnace endoscope can be used in difficult conditions, such as those found inside a chemical recovery boiler (~1,200°C and corrosive chemicals) with promising and accurate measurement results. The equipment has been tested in several furnaces.

  5. Macroscopic and microscopic characteristics of a fuel spray impinged on the wall

    NASA Astrophysics Data System (ADS)

    Park, Sung Wook; Lee, Chang Sik

    2004-11-01

    An experimental study was performed to investigate the macroscopic behavior and atomization characteristics of a high-speed diesel spray impinged on the wall at various injection and impinging conditions. The development processes of sprays impinged on the wall were visualized using the spray visualization system composed of a Nd:YAG laser and an intensified charge-coupled device (ICCD) camera. The atomization characteristics of the impinged spray on the wall were also explored in terms of mean droplet diameter and velocity distributions by using a phase Doppler particle analyzer (PDPA) system. The results provide the effects of injection parameters, wall conditions, and the other various experimental conditions on the macroscopic behavior and atomization characteristics of the impinged sprays on the wall.

  6. Experimental and numerical evaluation of the performance of supersonic two-stage high-velocity oxy-fuel thermal spray (Warm Spray) gun

    NASA Astrophysics Data System (ADS)

    Katanoda, H.; Morita, H.; Komatsu, M.; Kuroda, S.

    2011-03-01

    The water-cooled supersonic two-stage high-velocity oxy-fuel (HVOF) thermal spray gun was developed to make a coating of temperature-sensitive material, such as titanium, on a substrate. The gun has a combustion chamber (CC) followed by a mixing chamber (MC), in which the combustion gas is mixed with the nitrogen gas at room temperature. The mixed gas is accelerated to supersonic speed through a converging-diverging (C-D) nozzle followed by a straight passage called the barrel. This paper proposes an experimental procedure to estimate the cooling rate of CC, MC and barrel separately. Then, the mathematical model is presented to predict the pressure and temperature in the MC for the specific mass flow rates of fuel, oxygen and nitrogen by assuming chemical equilibrium with water-cooling in the CC and MC, and frozen flow with constant specific heat from stagnant condition to the throat in the CC and MC. Finally, the present mathematical model was validated by comparing the calculated and measured stagnant pressures of the CC of the two-stage HVOF gun.

  7. Fuel Retention Improvement at High Temperatures in Tungsten-Uranium Dioxide Dispersion Fuel Elements by Plasma-Spray Cladding

    NASA Technical Reports Server (NTRS)

    Grisaffe, Salvatore J.; Caves, Robert M.

    1964-01-01

    An investigation was undertaken to determine the feasibility of depositing integrally bonded plasma-sprayed tungsten coatings onto 80-volume-percent tungsten - 20-volume-percent uranium dioxide composites. These composites were face clad with thin tungsten foil to inhibit uranium dioxide loss at elevated temperatures, but loss at the unclad edges was still significant. By preheating the composite substrates to approximately 3700 degrees F in a nitrogen environment, metallurgically bonded tungsten coatings could be obtained directly by plasma spraying. Furthermore, even though these coatings were thin and somewhat porous, they greatly inhibited the loss of uranium dioxide. For example, a specimen that was face clad but had no edge cladding lost 5.8 percent uranium dioxide after 2 hours at 4750 dgrees F in flowing hydrogen. A similar specimen with plasma-spray-coated edges, however, lost only 0.75 percent uranium dioxide under the same testing conditions.

  8. Effect of plastic viscosity and yield value on spray characteristics of magnesium-slurry fuel

    NASA Technical Reports Server (NTRS)

    Prok, George M

    1957-01-01

    Magnesium slurries were sprayed onto a sheet of paper from an air-atomizing injector. Drop sizes and distributions were then determined from photomicrographs. Four different surface-active additives were used in preparing the slurries to give plastic viscosities between 0.22 and 0.51 poise and yield values between 150 and 810 dynes-cm(exp 2). It was found that there was no significant variation in the spray characteristics of these slurries when tested under the same conditions.

  9. Characterization of sprays

    NASA Technical Reports Server (NTRS)

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

    1984-01-01

    It is pointed out that most practical power generation and propulsion systems involve the burning of different types of fuel sprays, taking into account aircraft propulsion, industrial furnaces, boilers, gas turbines, and diesel engines. There has been a lack of data which can serve as a basis for spray model development and validation. A major aim of the present investigation is to fill this gap. Experimental apparatus and techniques for studying the characteristics of fuel sprays are discussed, taking into account two-dimensional still photography, cinematography, holography, a laser diffraction particle sizer, and a laser anemometer. The considered instruments were used in a number of experiments, taking into account three different types of fuel spray. Attention is given to liquid fuel sprays, high pressure pulsed diesel sprays, and coal-water slurry sprays.

  10. Liquid spray cooling of a heated surface

    NASA Technical Reports Server (NTRS)

    Grissom, W. M.; Wierum, F. A.

    1981-01-01

    The lowest surface temperature possible for the existance of spray evaporative cooling is determined experimentally to be a linear function of the impinging spray mass flux. A conduction-controlled analytical model of droplet evaporation gives fairly good agreement with experimental measurements at atmospheric pressure. At reduced pressures droplet evaporation rates are decreased significantly such that an optimum operating pressure exists for each desired surface heat flux. The initiation of the 'Leidenfrost state' provides the upper surface temperature bound for spray evaporative cooling.

  11. Liquid spray cooling of a heated surface

    NASA Technical Reports Server (NTRS)

    Grissom, W. M.; Wierum, F. A.

    1981-01-01

    The lowest surface temperature possible for the existance of spray evaporative cooling is determined experimentally to be a linear function of the impinging spray mass flux. A conduction-controlled analytical model of droplet evaporation gives fairly good agreement with experimental measurements at atmospheric pressure. At reduced pressures droplet evaporation rates are decreased significantly such that an optimum operating pressure exists for each desired surface heat flux. The initiation of the 'Leidenfrost state' provides the upper surface temperature bound for spray evaporative cooling.

  12. Mechanistic modeling of evaporating thin liquid film instability on a BWR fuel rod with parallel and cross vapor flow

    NASA Astrophysics Data System (ADS)

    Hu, Chih-Chieh

    This work has been aimed at developing a mechanistic, transient, 3-D numerical model to predict the behavior of an evaporating thin liquid film on a non-uniformly heated cylindrical rod with simultaneous parallel and cross flow of vapor. Interest in this problem has been motivated by the fact that the liquid film on a full-length boiling water reactor fuel rod may experience significant axial and azimuthal heat flux gradients and cross flow due to variations in the thermal-hydraulic conditions in surrounding subchannels caused by proximity to inserted control blade tip and/or the top of part-length fuel rods. Such heat flux gradients coupled with localized cross flow may cause the liquid film on the fuel rod surface to rupture, thereby forming a dry hot spot. These localized dryout phenomena can not be accurately predicted by traditional subchannel analysis methods in conjunction with empirical dryout correlations. To this end, a numerical model based on the Level Contour Reconstruction Method was developed. The Standard k-ε turbulence model is included. A cylindrical coordinate system has been used to enhance the resolution of the Level Contour Reconstruction Model. Satisfactory agreement has been achieved between the model predictions and experimental data. A model of this type is necessary to supplement current state-of-the-art BWR core thermal-hydraulic design methods based on subchannel analysis techniques coupled with empirical dry out correlations. In essence, such a model would provide the core designer with a "magnifying glass" by which the behavior of the liquid film at specific locations within the core (specific axial node on specific location within a specific bundle in the subchannel analysis model) can be closely examined. A tool of this type would allow the designer to examine the effectiveness of possible design changes and/or modified control strategies to prevent conditions leading to localized film instability and possible fuel failure.

  13. The N.A.C.A. Photographic Apparatus for Studying Fuel Sprays from Oil Engine Injection Valves and Test Results from Several Researches

    NASA Technical Reports Server (NTRS)

    Beardsley, Edward G

    1928-01-01

    Apparatus for recording photographically the start, growth, and cut-off of oil sprays from injection valves has been developed at the Langley Memorial Aeronautical Laboratory. The apparatus consists of a high-tension transformer by means of which a bank of condensers is charged to a high voltage. The controlled discharge of these condensers in sequence, at a rate of several thousand per second, produces electric sparks of sufficient intensity to illuminate the moving spray for photographing. The sprays are injected from various types of valves into a chamber containing gases at pressures up to 600 pounds per square inch. Several series of pictures are shown. The results give the effects of injection pressure, chamber pressure, specific gravity of the fuel oil used, and injection-valve design, upon spray characteristics.

  14. Spray Evaporation in Recirculating Flow

    DTIC Science & Technology

    1978-04-01

    obtained from measurements. An extremely rapid and simple method which can be used for determin’ing the size distribution in terms of the Rosin - Rammler ...parameters is the laser diffraction technique of Swithenbank et. al. 1 7 . Owing to its simplicity the Rosin - Rammler equation has been employed in this...an initial velocity of 21 m/sec. The calculations were performed for two different size constants of the Rosin - Rammler distribution, 50 { and 100

  15. Hot air drum evaporator

    DOEpatents

    Black, Roger L.

    1981-01-01

    An evaporation system for aqueous radioactive waste uses standard 30 and 55 gallon drums. Waste solutions form cascading water sprays as they pass over a number of trays arranged in a vertical stack within a drum. Hot dry air is circulated radially of the drum through the water sprays thereby removing water vapor. The system is encased in concrete to prevent exposure to radioactivity. The use of standard 30 and 55 gallon drums permits an inexpensive compact modular design that is readily disposable, thus eliminating maintenance and radiation build-up problems encountered with conventional evaporation systems.

  16. Prediction of soot and thermal radiation in a model gas turbine combustor burning kerosene fuel spray at different swirl levels

    NASA Astrophysics Data System (ADS)

    Ghose, Prakash; Patra, Jitendra; Datta, Amitava; Mukhopadhyay, Achintya

    2016-05-01

    Combustion of kerosene fuel spray has been numerically simulated in a laboratory scale combustor geometry to predict soot and the effects of thermal radiation at different swirl levels of primary air flow. The two-phase motion in the combustor is simulated using an Eulerian-Lagragian formulation considering the stochastic separated flow model. The Favre-averaged governing equations are solved for the gas phase with the turbulent quantities simulated by realisable k-ɛ model. The injection of the fuel is considered through a pressure swirl atomiser and the combustion is simulated by a laminar flamelet model with detailed kinetics of kerosene combustion. Soot formation in the flame is predicted using an empirical model with the model parameters adjusted for kerosene fuel. Contributions of gas phase and soot towards thermal radiation have been considered to predict the incident heat flux on the combustor wall and fuel injector. Swirl in the primary flow significantly influences the flow and flame structures in the combustor. The stronger recirculation at high swirl draws more air into the flame region, reduces the flame length and peak flame temperature and also brings the soot laden zone closer to the inlet plane. As a result, the radiative heat flux on the peripheral wall decreases at high swirl and also shifts closer to the inlet plane. However, increased swirl increases the combustor wall temperature due to radial spreading of the flame. The high incident radiative heat flux and the high surface temperature make the fuel injector a critical item in the combustor. The injector peak temperature increases with the increase in swirl flow mainly because the flame is located closer to the inlet plane. On the other hand, a more uniform temperature distribution in the exhaust gas can be attained at the combustor exit at high swirl condition.

  17. The production of porous layers for the solid oxide fuel cell by vacuum plasma spraying

    SciTech Connect

    Fendler, E.; Henne, R.; Lang, M.

    1995-12-31

    The vacuum plasma spraying (VPS) method was used to produce porous perovskite and Ni/YSZ (Yttria Stabilized Zirconia) cermet layers as cathode and anode for a SOFC, respectively. The perovskite powder was deposited without decomposition of the perovskite phase due to the use of Laval-nozzles and the adaption of spray parameters. The deposition of porous Ni/YSZ cermets demanded a modification of the Laval-nozzle. With this modification high deposition rates compared to conventional nozzles could be attained. The deposition of NiAl-YSZ and subsequently etching of Al is a successful method to produce anode layers with very fine porosity. Up to now the feasibility of producing porous deposits was examined. The next step of investigation will be the electrochemical testing of the electrodes. The results of those tests will influence the further development of anode`s and cathode`s microstructure.

  18. Enhancement and Prediction of Adhesion Strength of Copper Cold Spray Coatings on Steel Substrates for Nuclear Fuel Repository

    NASA Astrophysics Data System (ADS)

    Fernández, R.; MacDonald, D.; Nastić, A.; Jodoin, B.; Tieu, A.; Vijay, M.

    2016-12-01

    Thick copper coatings have been envisioned as corrosion protection barriers for steel containers used in repositories for nuclear waste fuel bundles. Due to its high deposition rate and low oxidation levels, cold spray is considered as an option to produce these coatings as an alternative to traditional machining processes to create corrosion protective sleeves. Previous investigations on the deposition of thick cold spray copper coatings using only nitrogen as process gas on carbon steel substrates have continuously resulted in coating delamination. The current work demonstrates the possibility of using an innovative surface preparation process, forced pulsed waterjet, to induce a complex substrate surface morphology that serves as anchoring points for the copper particles to mechanically adhere to the substrate. The results of this work show that, through the use of this surface preparation method, adhesion strength can be drastically increased, and thick copper coatings can be deposited using nitrogen. Through finite element analysis, it was shown that it is likely that the bonding created is purely mechanical, explaining the lack of adhesion when conventional substrate preparation methods are used and why helium is usually required as process gas.

  19. Crumpled rGO-supported Pt-Ir bifunctional catalyst prepared by spray pyrolysis for unitized regenerative fuel cells

    NASA Astrophysics Data System (ADS)

    Kim, In Gyeom; Nah, In Wook; Oh, In-Hwan; Park, Sehkyu

    2017-10-01

    Three-dimensional (3D) crumpled reduced graphene oxide supported Pt-Ir alloys that served as bifunctional oxygen catalysts for use in untized regenerative fuel cells were synthesized by a facile spray pyrolysis method. Pt-Ir catalysts supported on rGO (Pt-Ir/rGOs) were physically characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and thermogravimetric analysis (TGA) to observe change in composition by heat treatment, alloying, and morphological transition of the catalysts. Their catalytic activities and stabilities for the oxygen reduction reaction (ORR) and the oxygen evolution reaction (OER) conditions were electrochemically investigated using cyclic voltammetry (CV), linear sweep voltammetry (LSV), potential cycling and hold tests on the rotating disk electrode (RDE). Pt-Ir/rGO with no post heat-treatment (Pt-Ir/rGO_NP) showed a lower activity for ORR and OER although metal nanoparticles decorated on the support are relatively small. However, Pt-Ir/rGO showed remarkably enhanced activity following heat treatment, depending on temperature. Pt-Ir/rGO heat-treated at 600 °C after spray pyrolysis (Pt-Ir/rGO_P600) exhibited a higher activity and stability than a commercially available Pt/C catalyst kept under the ORR condition, and it also revealed a comparable OER activity and durability versus the commercial unsupported Ir catalyst.

  20. Computational analysis of a three-dimensional High-Velocity Oxygen-Fuel (HVOF) Thermal Spray torch

    SciTech Connect

    Hassan, B.; Lopez, A.R.; Oberkampf, W.L.

    1995-07-01

    An analysis of a High-Velocity Oxygen-Fuel Thermal Spray torch is presented using computational fluid dynamics (CFD). Three-dimensional CFD results are presented for a curved aircap used for coating interior surfaces such as engine cylinder bores. The device analyzed is similar to the Metco Diamond Jet Rotating Wire torch, but wire feed is not simulated. To the authors` knowledge, these are the first published 3-D results of a thermal spray device. The feed gases are injected through an axisymmetric nozzle into the curved aircap. Argon is injected through the center of the nozzle. Pre-mixed propylene and oxygen are introduced from an annulus in the nozzle, while cooling air is injected between the nozzle and the interior wall of the aircap. The combustion process is modeled assuming instantaneous chemistry. A standard, two-equation, K-{var_epsilon} turbulence model is employed for the turbulent flow field. An implicit, iterative, finite volume numerical technique is used to solve the coupled conservation of mass, momentum, and energy equations for the gas in a sequential manner. Flow fields inside and outside the aircap are presented and discussed.

  1. High-Velocity Oxygen Fuel Thermal Spray of Fe-Based Amorphous Alloy: a Numerical and Experimental Study

    NASA Astrophysics Data System (ADS)

    Ajdelsztajn, L.; Dannenberg, J.; Lopez, J.; Yang, N.; Farmer, J.; Lavernia, E. J.

    2009-09-01

    The fabrication of dense coatings with appropriate properties using a high velocity oxygen fuel (HVOF) spray process requires an in-depth understanding of the complete gas flow field and particle behavior during the process. A computational fluid dynamics (CFD) model is implemented to investigate the gas flow behavior that occurs during the HVOF process and a simplified one-dimensional decoupled model of the in-flight thermal behavior of the amorphous Fe-based powder particles was developed and applied for three different spray conditions. The numerical results were used to rationalize the different coating microstructures described in the experimental results. Low porosity and amorphous coatings were produced using two different particle size distributions (16 to 25 μm and 25 to 53 μm). The amorphous characteristics of the powder were retained in the coating due to melting and rapid solidification in the case of very fine powder or ligaments (<16 μm) and to the fact that the crystallization temperature was not reached in the case of the large particles (16 to 53 μm).

  2. Manufacturing and Properties of High-Velocity Oxygen Fuel (HVOF)-Sprayed FeVCrC Coatings

    NASA Astrophysics Data System (ADS)

    Sassatelli, Paolo; Bolelli, Giovanni; Lusvarghi, Luca; Manfredini, Tiziano; Rigon, Rinaldo

    2016-10-01

    This paper studies the microstructure, sliding wear behavior and corrosion resistance of high-velocity oxygen fuel (HVOF)-sprayed FeVCrC-based coatings. Various process parameters were tested to evaluate their effects on the coating properties, which were also compared to those of HVOF-sprayed NiCrBSi and Stellite-6 coatings. The Fe alloy coatings are composed of flattened splats, originating from molten droplets and consisting of a super-saturated solid solution, together with rounded particles, coming from partially unmolten material and containing V- and Fe-based carbide precipitates. All process parameters, apart from "extreme" settings with excess comburent in the flame, produce dense coatings, indicating that the feedstock powder is quite easily processable by HVOF. These coatings, with a microhardness of 650-750 HV0.3, exhibit wear rates of ≈2 × 10-6 mm3/(Nm) in ball-on-disk tests against sintered Al2O3 spheres. They perform far better than the reference coatings, and better than other Fe- and Ni-based alloy coatings tested in previous research. On the other hand, the corrosion resistance of the coating material (tested by electrochemical polarization in 0.1 M HCl solution) is quite low. Even in the absence of interconnected porosity, this results in extensive, selective damage to the Fe-based matrix. This coating material is therefore unadvisable for severely corrosive environments.

  3. Characterization of Copper Coatings Deposited by High-Velocity Oxy-Fuel Spray for Thermal and Electrical Conductivity Applications

    NASA Astrophysics Data System (ADS)

    Salimijazi, H. R.; Aghaee, M.; Salehi, M.; Garcia, E.

    2017-08-01

    Copper coatings were deposited on steel substrates by high-velocity oxy-fuel spraying. The microstructure of the feedstock copper powders and free-standing coatings were evaluated by optical and scanning electron microscopy. The x-ray diffraction pattern was utilized to determine phase compositions of powders and coatings. Oxygen content was determined by a LECO-T300 oxygen determiner. The thermal conductivity of the coatings was measured in two directions, through-thickness and in-plane by laser flash apparatus. The electrical resistivity of the coatings was measured by the four-point probe method. Oxygen content of the coatings was two times higher than that of the initial powders (0.35-0.37%). The thermal and electrical conductivities of the coatings were different depending on the direction of the measurement. The thermal and electrical conductivity of the coatings improved after annealing for 6 h at a temperature of 600°C.

  4. Morphologically architectured spray pyrolyzed lanthanum ferrite-based cathodes-A phenomenal enhancement in solid oxide fuel cell performance

    NASA Astrophysics Data System (ADS)

    Mukhopadhyay, Jayanta; Basu, Rajendra Nath

    2014-04-01

    Nanocrystalline single phase La1-xSrxCo1-yFeyO3-δ [LSCF] (0 < x ≤ 0.5, y = 0.2, 0.8) based cathodes (crystallite size 30-50 nm) are synthesized by two fluid spray-pyrolysis (SP) for solid oxide fuel cell (SOFC) application. The particulate sizes of the synthesized cathodes are found to be in the range of 100-200 nm. Particulate morphology of highest conducting cathode (∼1500 S cm-1) is tailored using homomolecular seeding agent of precalcined pyrolyzed ashes. Interfacial polarizations of the such SP synthesized screen printed cathodes onto gadolinium doped ceria (CGO) based electrolyte are found to be much lower (0.032-0.16 Ω cm2 at 800 °C-500 °C) with highest exchange current density (∼722 mA cm-2 at 800 °C) for oxygen reduction reaction. Enhanced current density of 4.0 A cm-2 (0.7 V, 800 °C) is obtained for SOFC button cells using optimized LSCF cathode with hydrogen as fuel and air as oxidant. LSCF cathodes synthesized by spray pyrolysis using homomolecular seeding exhibit interconnected mesoporosity having primary nano-particulates embedded within. Endurance test of button cells till 500 h results low degradation viz. 3.8% and 8.9% 1000 h-1 with electronic loads of 0.5 A cm-2 and 1.0 A cm-2 respectively. High performances of such cells are clinically correlated with SP processing conditions and particulate morphology of cathode powders.

  5. Application of TiC reinforced Fe-based coatings by means of High Velocity Air Fuel Spraying

    NASA Astrophysics Data System (ADS)

    Bobzin, K.; Öte, M.; Knoch, M. A.; Liao, X.; Sommer, J.

    2017-03-01

    In the field of hydraulic applications, different development trends can cause problems for coatings currently used as wear and corrosion protection for piston rods. Aqueous hydraulic fluids and rising raw material prices necessitate the search for alternatives to conventional coatings like galvanic hard chrome or High Velocity Oxygen Fuel (HVOF)-sprayed WC/Co coatings. In a previous study, Fe/TiC coatings sprayed by a HVOF-process, were identified to be promising coating systems for wear and corrosion protection in hydraulic systems. In this feasibility study, the novel High Velocity Air Fuel (HVAF)-process, a modification of the HVOF-process, is investigated using the same feedstock material, which means the powder is not optimized for the HVAF-process. The asserted benefits of the HVAF-process are higher particle velocities and lower process temperatures, which can result in a lower porosity and oxidation of the coating. Further benefits of the HVAF process are claimed to be lower process costs and higher deposition rates. In this study, the focus is set on to the applicability of Fe/TiC coatings by HVAF in general. The Fe/TiC HVAF coating could be produced, successfully. The HVAF- and HVOF-coatings, produced with the same powder, were investigated using micro-hardness, porosity, wear and corrosion tests. A similar wear coefficient and micro-hardness for both processes could be achieved. Furthermore the propane/hydrogen proportion of the HVAF process and its influence on the coating thickness and the porosity was investigated.

  6. On the combustion of a laminar spray

    NASA Technical Reports Server (NTRS)

    Levy, Yeshayahou; Bulzan, Daniel L.

    1993-01-01

    A spray combustor, with flow velocities in the laminar range, exhibits a unique operating mode where large amplitude, self-induced oscillations of the flame shape occur. The phenomenon, not previously encountered, only occurs when fuel is supplied in the form of fine liquid droplets and does not occur when fuel is supplied in gaseous form. Several flow mechanisms are coupled in such a fashion as to trigger and maintain the oscillatory motion of the flame. These mechanisms include heat transfer and evaporation processes, dynamics of two-phase flows, and effects of gravity (buoyancy forces). An interface volume, lying above the fuel nozzle and below the flame was found to be the most susceptible to gravity effects and postulated to be responsible for inducing the oscillatory motion. Heptane fuel was used in the majority of the tests. Tests performed with iso-octane also showed similar results.

  7. Role of Oxides and Porosity on High-Temperature Oxidation of Liquid-Fueled HVOF Thermal-Sprayed Ni50Cr Coatings

    NASA Astrophysics Data System (ADS)

    Song, B.; Bai, M.; Voisey, K. T.; Hussain, T.

    2017-02-01

    High chromium content in Ni50Cr thermally sprayed coatings can generate a dense and protective scale at the surface of coating. Thus, the Ni50Cr coating is widely used in high-temperature oxidation and corrosion applications. A commercially available gas atomized Ni50Cr powder was sprayed onto a power plant steel (ASME P92) using a liquid-fueled high velocity oxy-fuel thermal spray with three processing parameters in this study. Microstructure of as-sprayed coatings was examined using oxygen content analysis, mercury intrusion porosimetry, scanning electron microscope (SEM), energy-dispersive x-ray spectroscopy (EDX) and x-ray diffraction (XRD). Short-term air oxidation tests (4 h) of freestanding coatings (without boiler steel substrate) in a thermogravimetric analyzer at 700 °C were performed to obtain the kinetics of oxidation of the as-sprayed coating. Long-term air oxidation tests (100 h) of the coated substrates were performed at same temperature to obtain the oxidation products for further characterization in detail using SEM/EDX and XRD. In all samples, oxides of various morphologies developed on top of the Ni50Cr coatings. Cr2O3 was the main oxidation product on the surface of all three coatings. The coating with medium porosity and medium oxygen content has the best high-temperature oxidation performance in this study.

  8. Simultaneous imaging of fuel vapor mass fraction and gas-phase temperature inside gasoline sprays using two-line excitation tracer planar laser-induced fluorescence.

    PubMed

    Zigan, Lars; Trost, Johannes; Leipertz, Alfred

    2016-02-20

    This paper reports for the first time, to the best of our knowledge, on the simultaneous imaging of the gas-phase temperature and fuel vapor mass fraction distribution in a direct-injection spark-ignition (DISI) spray under engine-relevant conditions using tracer planar laser-induced fluorescence (TPLIF). For measurements in the spray, the fluorescence tracer 3-pentanone is added to the nonfluorescent surrogate fuel iso-octane, which is excited quasi-simultaneously by two different excimer lasers for two-line excitation LIF. The gas-phase temperature of the mixture of fuel vapor and surrounding gas and the fuel vapor mass fraction can be calculated from the two LIF signals. The measurements are conducted in a high-temperature, high-pressure injection chamber. The fluorescence calibration of the tracer was executed in a flow cell and extended significantly compared to the existing database. A detailed error analysis for both calibration and measurement is provided. Simultaneous single-shot gas-phase temperature and fuel vapor mass fraction fields are processed for the assessment of cyclic spray fluctuations.

  9. The development and application of an automatic boundary segmentation methodology to evaluate the vaporizing characteristics of diesel spray under engine-like conditions

    NASA Astrophysics Data System (ADS)

    Ma, Y. J.; Huang, R. H.; Deng, P.; Huang, S.

    2015-04-01

    Studying the vaporizing characteristics of diesel spray could greatly help to reduce engine emission and improve performance. The high-speed schlieren imaging method is an important optical technique for investigating the macroscopic vaporizing morphological evolution of liquid fuel, and pre-combustion constant volume combustion bombs are often used to simulate the high pressure and high temperature conditions occurring in diesel engines. Complicated background schlieren noises make it difficult to segment the spray region in schlieren spray images. To tackle this problem, this paper develops a vaporizing spray boundary segmentation methodology based on an automatic threshold determination algorithm. The methodology was also used to quantify the macroscopic characteristics of vaporizing sprays including tip penetration, near-field and far-field angles, and projected spray area and spray volume. The spray boundary segmentation methodology was realized in a MATLAB-based program. Comparisons were made between the spray characteristics obtained using the program method and those acquired using a manual method and the Hiroyasu prediction model. It is demonstrated that the methodology can segment and measure vaporizing sprays precisely and efficiently. Furthermore, the experimental results show that the spray angles were slightly affected by the injection pressure at high temperature and high pressure and under inert conditions. A higher injection pressure leads to longer spray tip penetration and a larger projected area and volume, while elevating the temperature of the environment can significantly promote the evaporation of cold fuel.

  10. Comparison of the Mechanical and Electrochemical Properties of WC-25Co Coatings Obtained by High Velocity Oxy-Fuel and Cold Gas Spraying

    NASA Astrophysics Data System (ADS)

    Couto, M.; Dosta, S.; Fernández, J.; Guilemany, J. M.

    2014-12-01

    Cold gas spray (CGS) coatings were previously produced by spraying WC-25Co cermet powders onto Al7075-T6 and low-carbon steel substrates. Unlike conventional flame spray techniques (e.g., high-velocity oxy-fuel; HVOF), no melting of the powder occurs; the particles are deformed and bond together after being sprayed by a supersonic jet of compressed gas, thereby building up several layers and forming a coating. WC-Co cermets are used in wear-resistant parts, because of their combination of mechanical, physical, and chemical properties. XRD tests were previously run on the initial powder and the coatings to determine possible phase changes during spraying. The bonding strength of the coatings was measured by adhesion tests. Here, WC-25Co coatings were also deposited on the same substrates by HVOF spraying. The wear resistance and fracture toughness of the coatings obtained previously by CGS and the HVOF coatings obtained here were studied. Their corrosion resistance was determined by electrochemical measurements. It was possible to achieve thick, dense, and hard CGS coatings on Al7075-T6 and low-carbon steel substrates, with better or the same mechanical and electrochemical properties as those of the HVOF coatings; making the former a highly competitive method for producing WC-25Co coatings.

  11. Improved Orifice Plate for Spray Gun

    NASA Technical Reports Server (NTRS)

    Cunningham, W.

    1986-01-01

    Erratic spray pattern of commercial spray gun changed to repeatable one by simple redesign of two parts. In modified spray gun orifice plate and polytetrafluoroethylene bushing redesigned to assure centering and alignment with nozzle. Such improvement useful in many industrial applications requiring repeatable spray patterns. Might include spraying of foam insulation, paint, other protective coatings, detergents, abrasives, adhesives, process chemicals, or fuels. Unmodified spray gun produces erratic spray because lateral misalignment between orifice plate and nozzle.

  12. Improved Orifice Plate for Spray Gun

    NASA Technical Reports Server (NTRS)

    Cunningham, W.

    1986-01-01

    Erratic spray pattern of commercial spray gun changed to repeatable one by simple redesign of two parts. In modified spray gun orifice plate and polytetrafluoroethylene bushing redesigned to assure centering and alignment with nozzle. Such improvement useful in many industrial applications requiring repeatable spray patterns. Might include spraying of foam insulation, paint, other protective coatings, detergents, abrasives, adhesives, process chemicals, or fuels. Unmodified spray gun produces erratic spray because lateral misalignment between orifice plate and nozzle.

  13. Low platinum loading for high temperature proton exchange membrane fuel cell developed by ultrasonic spray coating technique

    NASA Astrophysics Data System (ADS)

    Su, Huaneng; Jao, Ting-Chu; Barron, Olivia; Pollet, Bruno G.; Pasupathi, Sivakumar

    2014-12-01

    This paper reports use of an ultrasonic-spray for producing low Pt loadings membrane electrode assemblies (MEAs) with the catalyst coated substrate (CCS) fabrication technique. The main MEA sub-components (catalyst, membrane and gas diffusion layer (GDL)) are supplied from commercial manufacturers. In this study, high temperature (HT) MEAs with phosphoric acid (PA)-doped poly(2,5-benzimidazole) (AB-PBI) membrane are fabricated and tested under 160 °C, hydrogen and air feed 100 and 250 cc min-1 and ambient pressure conditions. Four different Pt loadings (from 0.138 to 1.208 mg cm-2) are investigated in this study. The experiment data are determined by in-situ electrochemical methods such as polarization curve, electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). The high Pt loading MEA exhibits higher performance at high voltage operating conditions but lower performances at peak power due to the poor mass transfer. The Pt loading 0.350 mg cm-2 GDE performs the peak power density and peak cathode mass power to 0.339 W cm-2 and 0.967 W mgPt-1, respectively. This work presents impressive cathode mass power and high fuel cell performance for high temperature proton exchange membrane fuel cells (HT-PEMFCs) with low Pt loadings.

  14. Laser-induced plasma generation and evolution in a transient spray.

    PubMed

    Kawahara, Nobuyuki; Tsuboi, Kazuya; Tomita, Eiji

    2014-01-13

    The behaviors of laser-induced plasma and fuel spray were investigated by visualizing images with an ultra-high-speed camera. Time-series images of laser-induced plasma in a transient spray were visualized using a high-speed color camera. The effects of a shockwave generated from the laser-induced plasma on the evaporated spray behavior were investigated. The interaction between a single droplet and the laser-induced plasma was investigated using a single droplet levitated by an ultrasonic levitator. Two main conclusions were drawn from these experiments: (1) the fuel droplets in the spray were dispersed by the shockwave generated from the laser-induced plasma; and (2) the plasma position may have shifted due to breakdown of the droplet surface and the lens effect of droplets.

  15. A fully spray-coated fuel cell membrane electrode assembly using Aquivion ionomer with a graphene oxide/cerium oxide interlayer

    NASA Astrophysics Data System (ADS)

    Breitwieser, Matthias; Bayer, Thomas; Büchler, Andreas; Zengerle, Roland; Lyth, Stephen M.; Thiele, Simon

    2017-05-01

    A novel multilayer membrane electrode assembly (MEA) for polymer electrolyte membrane fuel cells (PEMFCs) is fabricated in this work, within a single spray-coating device. For the first time, direct membrane deposition is used to fabricate a PEMFC by spraying the short-side-chain ionomer Aquivion directly onto the gas diffusion electrodes. The fully sprayed MEA, with an Aquivion membrane 10 μm in thickness, achieved a high power density of 1.6 W/cm2 for H2/air operation at 300 kPaabs. This is one of the highest reported values for thin composite membranes operated in H2/air atmosphere. By the means of confocal laser scanning microscopy, individual carbon fibers from the gas diffusion layer are identified to penetrate through the micro porous layer (MPL), likely causing a low electrical cell resistance in the range of 150 Ω cm2 through the thin sprayed membranes. By spraying a 200 nm graphene oxide/cerium oxide (GO/CeO2) interlayer between two layers of Aquivion ionomer, the impact of the electrical short is eliminated and the hydrogen crossover current density is reduced to about 1 mA/cm2. The peak power density of the interlayer-containing MEA drops only by 10% compared to a pure Aquivion membrane of similar thickness.

  16. Microstructural Characterization and Wear Behavior of Nano-Boride Dispersed Coating on AISI 304 Stainless Steel by Hybrid High Velocity Oxy-Fuel Spraying Laser Surface Melting

    NASA Astrophysics Data System (ADS)

    Sharma, Prashant; Majumdar, Jyotsna Dutta

    2015-07-01

    The current study concerns the detailed microstructural characterization and investigation of wear behavior of nano-boride dispersed coating developed on AISI 304 stainless steel by high velocity oxy-fuel spray deposition of nickel-based alloy and subsequent laser melting. There is a significant refinement and homogenization of microstructure with improvement in microhardness due to laser surface melting (1200 VHN as compared to 945 VHN of as-sprayed and 250 VHN of as-received substrate). The high temperature phase stability of the as-coated and laser melted surface has been studied by differential scanning calorimeter followed by detailed phase analysis at room and elevated temperature. There is a significant improvement in wear resistance of laser melted surface as compared to as-sprayed and the as-received one due to increased hardness and reduced coefficient of friction. The mechanism of wear has been investigated in details. Corrosion resistance of the coating in a 3.56 wt pct NaCl solution is significantly improved (4.43 E-2 mm/year as compared to 5 E-1 mm/year of as-sprayed and 1.66 mm/year of as-received substrate) due to laser surface melting as compared to as-sprayed surface.

  17. Effect of the increase in the entrance convergent section length of the gun nozzle on the high-velocity oxygen fuel and cold spray process

    NASA Astrophysics Data System (ADS)

    Sakaki, K.; Shimizu, Y.

    2001-09-01

    Nozzle geometry, which influences combustion gas dynamics and, therefore, sprayed particle behavior, is one of the most important parameters in the high-velocity oxygen-fuel (HVOF) thermal spray process. The nozzle geometry is also important in the cold spray method. The gas flows in the entrance convergent section of the nozzle exhibit a relatively higher temperature and are subsonic; thus, this region is most suitable for heating spray particles. In this study, numerical simulation and experiments investigated the effect of the entrance geometry of the gun nozzle on the HVOF process. The process changes inside the nozzle, as obtained by numerical simulation studies, were related to the coating properties. An Al2O3-40 mass% TiO2 powder was used for the experimental studies. The change in entrance convergent section length (rather than barrel part length or total length) of the gun nozzle had a significant effect on the deposition efficiency, microstructure, and hardness. The deposition efficiency and hardness increased as this geometry increased. On the other hand, the calculated and measured particle velocity showed a slight decrease. This effect on the HVOF process will also be applied to the nozzle design for the cold spray method.

  18. Effects of Fuel Spray Modeling on Combustion Instability Predictions in a Single-Element Lean Direct Injection (LDI) Gas Turbine Combustor

    DTIC Science & Technology

    2014-09-01

    Modeling on Combustion Instability Predictions in a Single- Element Lean Direct Injection (LDI) Gas Turbine Combustor 5b. GRANT NUMBER 5c. PROGRAM...injection (LDI) gas turbine combustor were performed to assess the effects of fuel spray modeling in predicting combustion instability. Concurrently...Research Laboratory (AFRL), Edwards AFB, CA, 93524 Simulations of a model configuration of a lean direct injection (LDI) gas turbine combustor were

  19. Comparative study of the flame structure of the burning sprays of the emulsions of jet a fuel water water and methanol

    SciTech Connect

    Gollahalli, S.R.; Javadi, S.H.

    1981-01-01

    Data are presented on the relative effects of emulsifying Jet A fuel with water and methanol on the flame properties of its sprays. Flame length, composition profiles, temperature profiles, flame radiation, emission of nitrogen oxides, and particulate concentration are studied. Results indicate that reductions of flame radiation, particulate concentration and nitrogen oxide emission can be achieved in both cases and water is more effective than methanol for causing those changes. 38 refs.

  20. High-pressure flame visualization of autoignition and flashback phenomena with liquid-fuel spray

    NASA Technical Reports Server (NTRS)

    Marek, C. J.; Baker, C. E.

    1983-01-01

    A study was undertaken to determine the effect of boundary layers on autoignition and flashback for premixed Jet-A fuel in a unique high-pressure windowed test facility. A plate was placed in the center of the fuel-air stream to establish a boundary layer. Four experimental configurations were tested: a 24.5-cm-long plate with either a pointed leading edge, a rounded edge or an edge with a 0.317-cm step, or the duct without the plate. Experiments at an equivalence ratio ranging from 0.4 to 0.9 were performed at pressures to 2500 kPa (25 atm.) at temperatures of 600, 645, and 700 K and velocities to 115 meters per second. Flame shapes were observed during flashback and autoignition using high speed cinematography. Flashback and autoignition limits were determined.

  1. The corrosion behavior and microstructure of high-velocity oxy-fuel sprayed nickel-base amorphous/nanocrystalline coatings

    NASA Astrophysics Data System (ADS)

    Dent, A. H.; Horlock, A. J.; McCartney, D. G.; Harris, S. J.

    1999-09-01

    The corrosion characteristics of two Ni-Cr-Mo-B alloy powders sprayed by the high-velocity oxy-fuel (HVOF) process have been studied using potentiodynamic and potentiostatic corrosion analysis in 0.5 M H2SO4. The deposits were also microstructurally characterized using x-ray diffraction (XRD), scanning electron microscopy (SEM) (utilizing both secondary electron and backscattered electron modes), and transmission electron microscopy (TEM). Results from the microstructural examination of the two alloys have revealed a predominantly amorphous/nanocrystalline face centered cubic (fcc) matrix containing submicron boride precipitates as well as regions of martensitically transformed laths. Apparent recrystallization of the amorphous matrix has also been observed in the form of cellular crystals with a fcc structure. The oxide stringers observed at splat boundaries were found to be columnar grained α-Cr2O3, though regions of the spinel oxide NiCr2O4 with a globular morphology were also observed. The coatings of the two alloys exhibited comparable resistance to corrosion in 0.5 M H2SO4, as revealed by potentiodynamic tests. They both had rest potentials approximately equal to -300 mV saturated calomel electrode (SCE) and passive region current densities of ˜1 mA/cm2. Microstructural examination of samples tested potentiostatically revealed the prevalence of degradation at splat boundaries, especially those where significant oxidation of the deposit occurred.

  2. A modified suspension spray combined with particle gradation method for preparation of protonic ceramic membrane fuel cells

    NASA Astrophysics Data System (ADS)

    Xie, Kui; Yan, Ruiqiang; Dong, Dehua; Wang, Songlin; Chen, Xiaorui; Jiang, Tao; Lin, Bin; Wei, Ming; Liu, Xingqin; Meng, Guangyao

    2008-05-01

    In order to prepare a dense proton-conductive Ba(Zr0.1Ce0.7)Y0.2O3-δ (BZCY7) electrolyte membrane, a proper anode composition with 65% Ni2O3 in weight ratio was determined after investigating the effects of anode compositions on anode shrinkages for co-sintering. The thermal expansion margins between sintered anodes and electrolytes, which were less than 1% below 750 °C, also showed good thermal expansion compatibility. A suspension spray combined with particle gradation method had been introduced to prepare dense electrolyte membrane on porous anode support. After a heat treatment at 1400 °C for 5 h, a cell with La0.5Sr0.5CoO3-δ (LSCO) cathode was assembled and tested with hydrogen and ammonia as fuels. The outputs reached as high as 330 mW cm-2 in hydrogen and 300 mW cm-2 in ammonia at 700 °C, respectively. Comparing with the interface of another cell prepared by dry-pressing method, this one also showed a good interface contact between electrodes and electrolyte. To sum up, this combined technique can be considered as commercial fabrication technology candidate.

  3. Computational fluid dynamics analysis of a wire-feed, high-velocity oxygen-fuel (HVOF) thermal spray torch

    SciTech Connect

    Lopez, A.R.; Hassan, B.; Oberkampf, W.L.; Neiser, R.A.; Roemer, T.J.

    1996-09-01

    The fluid and particle dynamics of a High-Velocity Oxygen-Fuel Thermal Spray torch are analyzed using computational and experimental techniques. Three-dimensional Computational Fluid Dynamics (CFD) results are presented for a curved aircap used for coating interior surfaces such as engine cylinder bores. The device analyzed is similar to the Metco Diamond Jet Rotating Wire (DJRW) torch. The feed gases are injected through an axisymmetric nozzle into the curved aircap. Premixed propylene and oxygen are introduced from an annulus in the nozzle, while cooling air is injected between the nozzle and the interior wall of the aircap. The combustion process is modeled using a single-step finite-rate chemistry model with a total of 9 gas species which includes dissociation of combustion products. A continually-fed steel wire passes through the center of the nozzle and melting occurs at a conical tip near the exit of the aircap. Wire melting is simulated computationally by injecting liquid steel particles into the flow field near the tip of the wire. Experimental particle velocity measurements during wire feed were also taken using a Laser Two-Focus (L2F) velocimeter system. Flow fields inside and outside the aircap are presented and particle velocity predictions are compared with experimental measurements outside of the aircap.

  4. Vacuum Plasma Spray of CuCrNb Alloy for Advanced Liquid - Fuel Combustion Chambers

    NASA Technical Reports Server (NTRS)

    Zimmerman, Frank

    2000-01-01

    The copper-8 atomic percent chromium-4 atomic percent niobium (CuCrNb) alloy was developed by Glenn Research Center (formally Lewis Research Center) as an improved alloy for combustion chamber liners. In comparison to NARloy-Z, the baseline (as in Space Shuttle Main Engine) alloy for such liners, CuCrNb demonstrates mechanical and thermophysical properties equivalent to NARloy-Z, but at temperatures 100 C to 150 C (180 F to 270 F) higher. Anticipated materials related benefits include decreasing the thrust cell liner weight 5% to 20%, increasing the service life at least two fold over current combustion chamber design, and increasing the safety margins available to designers. By adding an oxidation and thermal barrier coating to the liner, the combustion chamber can operate at even higher temperatures. For all these benefits, however, this alloy cannot be formed using conventional casting and forging methods because of the levels of chromium and niobium, which exceed their solubility limit in copper. Until recently, the only forming process that maintains the required microstructure of CrNb intermetallics is powder metallurgy formation of a billet from powder stock, followed by extrusion. This severely limits its usefulness in structural applications, particularly the complex shapes required for combustion chamber liners. Vacuum plasma spray (VPS) has been demonstrated as a method to form structural articles including small combustion chambers from the CuCrNb alloy. In addition, an oxidation and thermal barrier layer can be formed integrally on the hot wall of the liner that improve performance and extend service life. This paper discusses the metallurgy and thermomechanical properties of VPS formed CuCrNb versus the baseline powder metallurgy process, and the manufacturing of small combustion chamber liners at Marshall Space Flight Center using the VPS process. The benefits to advanced propulsion initiatives of using VPS to fabricate combustion chamber liners

  5. Vacuum Plasma Spray of CuCrNb Alloy for Advanced Liquid - Fuel Combustion Chambers

    NASA Technical Reports Server (NTRS)

    Zimmerman, Frank

    2000-01-01

    The copper-8 atomic percent chromium-4 atomic percent niobium (CuCrNb) alloy was developed by Glenn Research Center (formally Lewis Research Center) as an improved alloy for combustion chamber liners. In comparison to NARloy-Z, the baseline (as in Space Shuttle Main Engine) alloy for such liners, CuCrNb demonstrates mechanical and thermophysical properties equivalent to NARloy-Z, but at temperatures 100 C to 150 C (180 F to 270 F) higher. Anticipated materials related benefits include decreasing the thrust cell liner weight 5% to 20%, increasing the service life at least two fold over current combustion chamber design, and increasing the safety margins available to designers. By adding an oxidation and thermal barrier coating to the liner, the combustion chamber can operate at even higher temperatures. For all these benefits, however, this alloy cannot be formed using conventional casting and forging methods because of the levels of chromium and niobium, which exceed their solubility limit in copper. Until recently, the only forming process that maintains the required microstructure of CrNb intermetallics is powder metallurgy formation of a billet from powder stock, followed by extrusion. This severely limits its usefulness in structural applications, particularly the complex shapes required for combustion chamber liners. Vacuum plasma spray (VPS) has been demonstrated as a method to form structural articles including small combustion chambers from the CuCrNb alloy. In addition, an oxidation and thermal barrier layer can be formed integrally on the hot wall of the liner that improve performance and extend service life. This paper discusses the metallurgy and thermomechanical properties of VPS formed CuCrNb versus the baseline powder metallurgy process, and the manufacturing of small combustion chamber liners at Marshall Space Flight Center using the VPS process. The benefits to advanced propulsion initiatives of using VPS to fabricate combustion chamber liners

  6. Modeling of the Evaporative Cooling of Running-Down Liquid Films in the Slit Channel of the Spraying Device of a Cooling Tower

    NASA Astrophysics Data System (ADS)

    Dashkov, G. V.; Malenko, G. L.; Solodukhin, A. D.; Tyutyuma, V. D.

    2014-11-01

    This paper presents the results of computational modeling of the nonstationary evaporative cooling of a liquid film running down a vertical surface cooled by a turbulent vapor-air counterflow. The heat and mass transfer problem has been formulated in conjugate form. The calculation data on the total heat flow density at the interface for various instants of time are given.

  7. Transient heat transfer behavior of water spray evaporative cooling on a stainless steel cylinder with structured surface for safety design application in high temperature scenario

    NASA Astrophysics Data System (ADS)

    Aamir, Muhammad; Liao, Qiang; Hong, Wang; Xun, Zhu; Song, Sihong; Sajid, Muhammad

    2017-02-01

    High heat transfer performance of spray cooling on structured surface might be an additional measure to increase the safety of an installation against any threat caused by rapid increase in the temperature. The purpose of present experimental study is to explore heat transfer performance of structured surface under different spray conditions and surface temperatures. Two cylindrical stainless steel samples were used, one with pyramid pins structured surface and other with smooth surface. Surface heat flux of 3.60, 3.46, 3.93 and 4.91 MW/m2 are estimated for sample initial average temperature of 600, 700, 800 and 900 °C, respectively for an inlet pressure of 1.0 MPa. A maximum cooling rate of 507 °C/s was estimated for an inlet pressure of 0.7 MPa at 900 °C for structured surface while for smooth surface maximum cooling rate of 356 °C/s was attained at 1.0 MPa for 700 °C. Structured surface performed better to exchange heat during spray cooling at initial sample temperature of 900 °C with a relative increase in surface heat flux by factor of 1.9, 1.56, 1.66 and 1.74 relative to smooth surface, for inlet pressure of 0.4, 0.7, 1.0 and 1.3 MPa, respectively. For smooth surface, a decreasing trend in estimated heat flux is observed, when initial sample temperature was increased from 600 to 900 °C. Temperature-based function specification method was utilized to estimate surface heat flux and surface temperature. Limited published work is available about the application of structured surface spray cooling techniques for safety of stainless steel structures at very high temperature scenario such as nuclear safety vessel and liquid natural gas storage tanks.

  8. Spray combustion at normal and reduced gravity in counterflow and co-flow configurations

    NASA Technical Reports Server (NTRS)

    Gomez, Alessandro; Chen, Gung

    1995-01-01

    Liquid fuel dispersion in practical systems is typically achieved by spraying the fuel into a polydisperse distribution of droplets evaporating and burning in a turbulent gaseous environment In view of the nearly insurmountable difficulties of this two-phase flow, a systematic study of spray evaporation and burning in configurations of gradually increasing levels of complexity, starting from laminar sprays to fully turbulent ones, would be useful. A few years ago we proposed to use an electrostatic spray of charged droplets for this type of combustion experiments under well-defined conditions. In the simplest configuration, a liquid is fed into a small metal tube maintained at several kilovolts relative to a ground electrode few centimeters away. Under the action of the electric field, the liquid meniscus at the outlet of the capillary takes a conical shape, with a thin jet emerging from the cone tip (cone-jet mode). This jet breaks up farther downstream into a spray of charged droplets - the so-called ElectroSpray (ES). Several advantages distinguish the electrospray from alternative atomization techniques: (1) it can produce quasi-monodisperse droplets over a phenomenal size range; (2) the atomization, that is strictly electrostatic, is decoupled from gas flow processes, which provides some flexibility in the selection and control of the experimental conditions; (3) the Coulombic repulsion of homopolarly charged droplets induces spray self-dispersion and prevents droplet coalescence; (4) the ES provides the opportunity of studying regimes of slip between droplets and host gas without compromising the control of the spray properties; and (5) the compactness and potential controllability of this spray generation system makes it appealing for studies in reduced-gravity environments aimed at isolating the spray behavior from natural convection complications. With these premises, in March 1991 we initiated a series of experiments under NASA sponsorship (NAG3-1259 and

  9. Diesel spray interaction with highly porous structures for supporting of liquid distribution in space and its vaporization

    NASA Astrophysics Data System (ADS)

    Weclas, M.; Cypris, J.; Maksoud, T. M. A.

    2012-05-01

    If a free high velocity jet (Diesel spray) propagating in space outwards of the nozzle exit collides (impinges onto) with highly porous structure (PM) the results of such an interaction is characterized by significant radial spreading of the spray, reduced axial penetration length, significantly increase spray surface area, reduced propagating velocity after interaction with PM and enhanced vaporization if the porous structure is hot. Due to those effects a very quick spray distribution in space is observed. This effect can, for example, be used for mixture homogenization for a clean combustion process. The rapid radial spreading of the spray by interaction with a porous structure is a result of multi-jet splitting. To some extent, Diesel jet interaction with a three-dimensional porous structure could be simulated by jet interaction with small cylindrical obstacles simulating wall junctions of a real porous medium. Based on the principles of spray interaction with porous structure there are two different cases to be considered: 1-porous medium in the form of thin ring positioned around the fuel nozzle (called distribution nozzle); 2-porous medium in the form of three-dimensional volumetric reactor. In the case of the distribution nozzle the target is to distribute fuel in space outside the porous ring and to enhance the vaporization process. In the case of combustion reactor the spray interacts with a number of wall junctions inside the porous structure and the main target is to homogeneously distribute the spray in PM volume, to evaporate the fuel and to mix with combustion air. The jets leaving diesel nozzle very early interact with porous ring resulting in a shining-like fuel distribution in space: for a cold ring a multi-jet splitting is responsible for observed fuel distribution in space; for a hot porous ring a superposition of fuel distribution and fuel vaporization must be considered.

  10. Probing the Evaporation Dynamics of Ethanol/Gasoline Biofuel Blends Using Single Droplet Manipulation Techniques.

    PubMed

    Corsetti, Stella; Miles, Rachael E H; McDonald, Craig; Belotti, Yuri; Reid, Jonathan P; Kiefer, Johannes; McGloin, David

    2015-12-24

    Using blends of bioethanol and gasoline as automotive fuel leads to a net decrease in the production of harmful emission compared to the use of pure fossil fuel. However, fuel droplet evaporation dynamics change depending on the mixing ratio. Here we use single particle manipulation techniques to study the evaporation dynamics of ethanol/gasoline blend microdroplets. The use of an electrodynamic balance enables measurements of the evaporation of individual droplets in a controlled environment, while optical tweezers facilitate studies of the behavior of droplets inside a spray. Hence, the combination of both methods is perfectly suited to obtain a complete picture of the evaporation process. The influence of adding varied amounts of ethanol to gasoline is investigated, and we observe that droplets with a greater fraction of ethanol take longer to evaporate. Furthermore, we find that our methods are sensitive enough to observe the presence of trace amounts of water in the droplets. A theoretical model, predicting the evaporation of ethanol and gasoline droplets in dry nitrogen gas, is used to explain the experimental results. Also a theoretical estimation of the saturation of the environment, with other aerosols, in the tweezers is carried out.

  11. Friction and wear properties of high-velocity oxygen fuel sprayed WC-17Co coating under rotational fretting conditions

    NASA Astrophysics Data System (ADS)

    Luo, Jun; Cai, Zhenbing; Mo, Jiliang; Peng, Jinfang; Zhu, Minhao

    2016-05-01

    Rotational fretting which exist in many engineering applications has incurred enormous economic loss. Thus, accessible methods are urgently needed to alleviate or eliminate damage by rotational fretting. Surface engineering is an effective approach that is successfully adopted to enhance the ability of components to resist the fretting damage. In this paper, using a high-velocity oxygen fuel sprayed (HVOF) technique WC-17Co coating is deposited on an LZ50 steel surface to study its properties through Vickers hardness testing, scanning electric microscope (SEM), energy dispersive X-ray spectroscopy (EDX), and X-ray diffractrometry (XRD). Rotational fretting wear tests are conducted under normal load varied from 10 N to 50 N, and angular displacement amplitudes vary from 0.125° to 1°. Wear scars are examined using SEM, EDX, optical microscopy (OM), and surface topography. The experimental results reveal that the WC-17Co coating adjusted the boundary between the partial slip regime (PSR) and the slip regime (SR) to the direction of smaller amplitude displacement. As a result, the coefficients of friction are consistently lower than the substrate's coefficients of friction both in the PSR and SR. The damage to the coating in the PSR is very slight. In the SR, the coating exhibits higher debris removal efficiency and load-carrying capacity. The bulge is not found for the coating due to the coating's higher hardness to restrain plastic flow. This research could provide experimental bases for promoting industrial application of WC-17Co coating in prevention of rotational fretting wear.

  12. Experimental Investigation of Droplet Evaporation of Water with Ground Admixtures while Motion in a Flame of Liquid Fuel

    NASA Astrophysics Data System (ADS)

    Dmitriyenko, Margarita A.; Nyashina, Galina S.; Zhdanova, Alena O.; Vysokomornaya, Olga V.

    2016-02-01

    The evaporation features for the atomized flow of suspension on the base of water with ground admixtures in an area of high-temperature combustion products of liquid flammable substance (acetone) were investigated experimentally by the optical methods of gas flow diagnostic and the high-speed video recording. The scales of influence of clay and silt concentration in droplets of atomized flow on the intensity of its evaporation were determined. The approximation dependences describing a decrease in typical size of suspension droplets at various values of ground admixtures were obtained.

  13. Mechanisms of Smoke Reduction in the High-Pressure Combustion of Emulsified Fuels. Volume II. Experimental and Theoretical Study of Evaporating Emulsified and Neat Fuel Sprays.

    DTIC Science & Technology

    1982-12-01

    drop systems. The drop-size data are available as either a set of two parameters defining a Rosin - Rammler , log-normal, or normal distribution, or as...the Rosin - Rammler has generally provided the best fit and was used throughout this program. A 300 mm focal length f/7.3 lens was used to collect the...temperataire of 311 K. The computed drop size data assuming a Rosin - Rammler distribution are shown on the top line and include the two Rosin

  14. Evaporation and ignition of droplets in combustion chambers modeling and simulation

    NASA Astrophysics Data System (ADS)

    Betelin, V. B.; Smirnov, N. N.; Nikitin, V. F.; Dushin, V. R.; Kushnirenko, A. G.; Nerchenko, V. A.

    2012-01-01

    Computer simulation of liquid fuel jet injection into heated atmosphere of combustion chamber, mixture formation, ignition and combustion need adequate modeling of evaporation, which is extremely important for the curved surfaces in the presence of strong heat and mass diffusion fluxes. Combustion of most widely spread hydrocarbon fuels takes place in a gas-phase regime. Thus, evaporation of fuel from the surface of droplets turns to be one of the limiting factors of the process as well. The problems of fuel droplets atomization, evaporation being the key factors for heterogeneous reacting mixtures, the non-equilibrium effects in droplets atomization and phase transitions will be taken into account in describing thermal and mechanical interaction of droplets with streaming flows. In the present paper processes of non-equilibrium evaporation of small droplets will be discussed. As it was shown before, accounting for non-equilibrium effects in evaporation for many types of widely used liquids is crucial for droplet diameters less than 100 μm, while the surface tension effects essentially manifest only for droplets below 0.1 μm. Investigating the behavior of individual droplets in a heated air flow allowed to distinguish two scenarios for droplet heating and evaporation. Small droplets undergo successively heating, then cooling due to heat losses for evaporation, and then rapid heating till the end of their lifetime. Larger droplets could directly be heated up to a critical temperature and then evaporate rapidly. Droplet atomization interferes the heating, evaporation and combustion scenario. The scenario of fuel spray injection and self-ignition in a heated air inside combustion chamber has three characteristic stages. At first stage of jet injection droplets evaporate very rapidly thus cooling the gas at injection point, the liquid jet is very short and changes for a vapor jet. At second stage liquid jet is becoming longer, because evaporation rate decreases due

  15. Electrostatic Dispersion and Evaporation of Dense and Dilute Clusters of Drops of High-Energy Fuel For Soot Control

    NASA Technical Reports Server (NTRS)

    Bellan, J.; Harstad, K.

    1997-01-01

    The high-energy-density (HED) fuels developed under U.S. Navy sponsorship as a replacement for conventional liquid fuels, in its missile propulsion systems have the drawback of high soot propensity: this makes misiles visible and thus strategically unacceptabel.

  16. Electrostatic Dispersion and Evaporation of Dense and Dilute Clusters of Drops of High-Energy Fuel For Soot Control

    NASA Technical Reports Server (NTRS)

    Bellan, J.; Harstad, K.

    1997-01-01

    The high-energy-density (HED) fuels developed under U.S. Navy sponsorship as a replacement for conventional liquid fuels, in its missile propulsion systems have the drawback of high soot propensity: this makes misiles visible and thus strategically unacceptabel.

  17. Characterization of microstructure and surface properties of hybrid coatings of WC-CoCr prepared by laser heat treatment and high velocity oxygen fuel spraying

    SciTech Connect

    Zhang Shihong Cho, Tong-Yul; Yoon, Jae-Hong; Fang, Wei; Song, Ki-O; Li Mingxi; Joo, Yun-Kon; Lee, Chan Gyu

    2008-10-15

    The microstructure and microhardness of high velocity oxygen fuel-sprayed WC-CoCr coatings were comparatively studied both before and after laser heat treatment of the coatings. Optical microscopy, scanning electron microscopy, X-ray diffraction and microhardness testing were applied to investigate the microstructure, phase composition, porosity and microhardness. The results indicate that WC is still present, and W{sub 2}C has appeared, while neither cobalt nor {sigma}-CrCo is detectable. Co{sub 4}W{sub 2}C has appeared in the high velocity oxygen fuel-sprayed coating after laser heat treatment as compared to the coating before laser treatment. The relative content of the W{sub 2}C has not increased with laser treatment, but the laser treatment has essentially eliminated the porosity almost entirely, providing a more homogeneous and densified microstructure. The laser heat treatment has effected the formation of a denser compact coating on the substrate. After laser heat treatment, the thickness of the coating has decreased from 300 {mu}m to 225 {mu}m. This corresponds to an average porosity in the high velocity oxygen fuel-sprayed coating that is approximately five times greater than that in the subsequently laser heat-treated coating. The laser treatment has also resulted in an increased hardness of the coating near the surface, where the average value increased from Hv{sub 0.2} = 1262.4 in the coating before laser heat treatment to Hv{sub 0.2} = 1818.7 after laser heat treatment.

  18. Effect of fuel rate and annealing process of LiFePO{sub 4} cathode material for Li-ion batteries synthesized by flame spray pyrolysis method

    SciTech Connect

    Halim, Abdul; Setyawan, Heru; Machmudah, Siti; Nurtono, Tantular; Winardi, Sugeng

    2014-02-24

    In this study the effect of fuel rate and annealing on particle formation of LiFePO{sub 4} as battery cathode using flame spray pyrolysis method was investigated numerically and experimentally. Numerical study was done using ANSYS FLUENT program. In experimentally, LiFePO{sub 4} was synthesized from inorganic aqueous solution followed by annealing. LPG was used as fuel and air was used as oxidizer and carrier gas. Annealing process attempted in inert atmosphere at 700°C for 240 min. Numerical result showed that the increase of fuel rate caused the increase of flame temperature. Microscopic observation using Scanning Electron Microscopy (SEM) revealed that all particles have sphere and polydisperse. Increasing fuel rate caused decreasing particle size and increasing particles crystallinity. This phenomenon attributed to the flame temperature. However, all produced particles still have more amorphous phase. Therefore, annealing needed to increase particles crystallinity. Fourier Transform Infrared (FTIR) analysis showed that all particles have PO4 function group. Increasing fuel rate led to the increase of infrared spectrum absorption corresponding to the increase of particles crystallinity. This result indicated that phosphate group vibrated easily in crystalline phase. From Electrochemical Impedance Spectroscopy (EIS) analysis, annealing can cause the increase of Li{sup +} diffusivity. The diffusivity coefficient of without and with annealing particles were 6.84399×10{sup −10} and 8.59888×10{sup −10} cm{sup 2} s{sup −1}, respectively.

  19. The Structure and Properties of Plasma Sprayed Iron Oxide Doped Manganese Cobalt Oxide Spinel Coatings for SOFC Metallic Interconnectors

    NASA Astrophysics Data System (ADS)

    Puranen, Jouni; Lagerbom, Juha; Hyvärinen, Leo; Kylmälahti, Mikko; Himanen, Olli; Pihlatie, Mikko; Kiviaho, Jari; Vuoristo, Petri

    2011-01-01

    Manganese cobalt oxide spinel doped with Fe2O3 was studied as a protective coating on ferritic stainless steel interconnects. Chromium alloying causes problems at high operation temperatures in such oxidizing conditions where chromium compounds evaporate and poison the cathode active area, causing the degradation of the solid oxide fuel cell. In order to prevent chromium evaporation, these interconnectors need a protective coating to block the chromium evaporation and to maintain an adequate electrical conductivity. Thermal spraying is regarded as a promising way to produce dense and protective layers. In the present work, the ceramic Mn-Co-Fe oxide spinel coatings were produced by using the atmospheric plasma spray process. Coatings with low thickness and low amount of porosity were produced by optimizing deposition conditions. The original spinel structure decomposed because of the fast transformation of solid-liquid-solid states but was partially restored by using post-annealing treatment.

  20. Application of sol gel spin coated yttria-stabilized zirconia layers for the improvement of solid oxide fuel cell electrolytes produced by atmospheric plasma spraying

    NASA Astrophysics Data System (ADS)

    Rose, Lars; Kesler, Olivera; Tang, Zhaolin; Burgess, Alan

    Due to its high thermal stability and purely oxide ionic conductivity, yttria-stabilized zirconia (YSZ) is the most commonly used electrolyte material for solid oxide fuel cells (SOFCs). Standard electrolyte fabrication techniques for planar SOFCs involve wet ceramic techniques such as tape-casting or screen printing, requiring sintering steps at temperatures above 1300 °C. Plasma spraying (PS) may provide a more rapid and cost efficient method to produce SOFCs without sintering. High-temperature sintering requires long processing times and can lead to oxidation of metal alloys used as mechanical supports, or to detrimental interreactions between the electrolyte and adjacent electrode layers. This study investigates the use of spin coated sol gel derived YSZ precursor solutions to fill the pores present in plasma sprayed YSZ layers, and to enhance the surface area for reaction at the electrolyte-cathode interface, without the use of high-temperature firing steps. The effects of different plasma conditions and sol concentrations and solid loadings on the gas permeability and fuel cell performance have been investigated.

  1. Fe-Al Weld Overlay and High Velocity Oxy-Fuel Thermal Spray Coatings for Corrosion Protection of Waterwalls in Fossil Fired Plants with Low NOx Burners

    SciTech Connect

    Regina, J.R.

    2002-02-08

    Iron-aluminum-chromium coatings were investigated to determine the best candidates for coatings of boiler tubes in Low NOx fossil fueled power plants. Ten iron-aluminum-chromium weld claddings with aluminum concentrations up to 10wt% were tested in a variety of environments to evaluate their high temperature corrosion resistance. The weld overlay claddings also contained titanium additions to investigate any beneficial effects from these ternary and quaternary alloying additions. Several High-Velocity Oxy-Fuel (HVOF) thermal spray coatings with higher aluminum concentrations were investigated as well. Gaseous corrosion testing revealed that at least 10wt%Al is required for protection in the range of environments examined. Chromium additions were beneficial in all of the environments, but additions of titanium were beneficial only in sulfur rich atmospheres. Similar results were observed when weld claddings were in contact with corrosive slag while simultaneously, exposed to the corrosive environments. An aluminum concentration of 10wt% was required to prevent large amounts of corrosion to take place. Again chromium additions were beneficial with the greatest corrosion protection occurring for welds containing both 10wt%Al and 5wt%Cr. The exposed thermal spray coatings showed either significant cracking within the coating, considerable thickness loss, or corrosion products at the coating substrate interface. Therefore, the thermal spray coatings provided the substrate very little protection. Overall, it was concluded that of the coatings studied weld overlay coatings provide superior protection in these Low NOx environments; specifically, the ternary weld composition of 10wt%Al and 5wt%Cr provided the best corrosion protection in all of the environments tested.

  2. Experimental evaluation of a breadboard heat and product-water removal system for a space-power fuel cell designed with static water removal and evaporative cooling

    NASA Technical Reports Server (NTRS)

    Hagedorn, N. H.; Prokipius, P. R.

    1977-01-01

    A test program was conducted to evaluate the design of a heat and product-water removal system to be used with fuel cell having static water removal and evaporative cooling. The program, which was conducted on a breadboard version of the system, provided a general assessment of the design in terms of operational integrity and transient stability. This assessment showed that, on the whole, the concept appears to be inherently sound but that in refining this design, several facets will require additional study. These involve interactions between pressure regulators in the pumping loop that occur when they are not correctly matched and the question of whether an ejector is necessary in the system.

  3. Spray Diagnostics in Rocket Engines Using Phase Doppler Analyzer

    NASA Technical Reports Server (NTRS)

    Isaac, Kakkattukuzhy M.

    1996-01-01

    Characteristics such as drop velocity, drop size, number density, volume flow rate, volume flux, and evaporation rate of the fuel spray in a rocket engine are directly related to engine performance. Several studies of shear coaxial atomization have been done in the past. However, additional work related to sprays at supercritical and transcritical conditions would be useful. The author undertook a study of the feasibility of using a phase Doppler particle analyzer (PDPA) for spray measurements in rocket engines as a part of the Summer Faculty Fellowship Program at the NASA Marshall Space Flight Center. The PDPA is a single particle counter (SPC) system based on light scattering from spherical particles. The PDPA instrument is based on refractive and reflective scattering as opposed to other instruments based on diffractive scattering. The main advantage of the PDPA instrument is its ability to provide point-wise information. The following sections describe the principle of operation of the PDPA system and the data obtained using a PDPA instrument in a spray formed by a commercially available fuel injection nozzle.

  4. Model of Mixing Layer With Multicomponent Evaporating Drops

    NASA Technical Reports Server (NTRS)

    Bellan, Josette; Le Clercq, Patrick

    2004-01-01

    A mathematical model of a three-dimensional mixing layer laden with evaporating fuel drops composed of many chemical species has been derived. The study is motivated by the fact that typical real petroleum fuels contain hundreds of chemical species. Previously, for the sake of computational efficiency, spray studies were performed using either models based on a single representative species or models based on surrogate fuels of at most 15 species. The present multicomponent model makes it possible to perform more realistic simulations by accounting for hundreds of chemical species in a computationally efficient manner. The model is used to perform Direct Numerical Simulations in continuing studies directed toward understanding the behavior of liquid petroleum fuel sprays. The model includes governing equations formulated in an Eulerian and a Lagrangian reference frame for the gas and the drops, respectively. This representation is consistent with the expected volumetrically small loading of the drops in gas (of the order of 10 3), although the mass loading can be substantial because of the high ratio (of the order of 103) between the densities of liquid and gas. The drops are treated as point sources of mass, momentum, and energy; this representation is consistent with the drop size being smaller than the Kolmogorov scale. Unsteady drag, added-mass effects, Basset history forces, and collisions between the drops are neglected, and the gas is assumed calorically perfect. The model incorporates the concept of continuous thermodynamics, according to which the chemical composition of a fuel is described probabilistically, by use of a distribution function. Distribution functions generally depend on many parameters. However, for mixtures of homologous species, the distribution can be approximated with acceptable accuracy as a sole function of the molecular weight. The mixing layer is initially laden with drops in its lower stream, and the drops are colder than the gas

  5. Portable Spray Booth

    NASA Technical Reports Server (NTRS)

    Hansen, Timothy D.; Bardwell, Micheal J.

    1996-01-01

    Portable spray booth provides for controlled application of coating materials with high solvent contents. Includes contoured shroud and carbon filter bed limiting concentration of fumes in vicinity. Designed to substitute spraying for brush application of solvent-based adhesive prior to installing rubber waterproof seals over joints between segments of solid-fuel rocket motor. With minor adjustments and modifications, used to apply other solvent-based adhesives, paints, and like.

  6. Portable Spray Booth

    NASA Technical Reports Server (NTRS)

    Hansen, Timothy D.; Bardwell, Micheal J.

    1996-01-01

    Portable spray booth provides for controlled application of coating materials with high solvent contents. Includes contoured shroud and carbon filter bed limiting concentration of fumes in vicinity. Designed to substitute spraying for brush application of solvent-based adhesive prior to installing rubber waterproof seals over joints between segments of solid-fuel rocket motor. With minor adjustments and modifications, used to apply other solvent-based adhesives, paints, and like.

  7. 40 CFR 1045.25 - How do the requirements related to evaporative emissions apply to engines and their fuel systems?

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR POLLUTION CONTROLS CONTROL OF EMISSIONS FROM SPARK-IGNITION PROPULSION MARINE ENGINES AND VESSELS Overview and Applicability § 1045.25 How do the requirements... new portable marine fuel tanks must be certified to the applicable requirements of 40 CFR part...

  8. Plasma sprayed ceria-containing interlayer

    DOEpatents

    Schmidt, Douglas S.; Folser, George R.

    2006-01-10

    A plasma sprayed ceria-containing interlayer is provided. The interlayer has particular application in connection with a solid oxide fuel cell used within a power generation system. The fuel cell advantageously comprises an air electrode, a plasma sprayed interlayer disposed on at least a portion of the air electrode, a plasma sprayed electrolyte disposed on at least a portion of the interlayer, and a fuel electrode applied on at least a portion of the electrolyte.

  9. Acoustic effects of sprays

    NASA Technical Reports Server (NTRS)

    Pindera, Maciej Z.; Przekwas, Andrzej J.

    1994-01-01

    Since the early 1960's, it has been known that realistic combustion models for liquid fuel rocket engines should contain at least a rudimentary treatment of atomization and spray physics. This is of particular importance in transient operations. It has long been recognized that spray characteristics and droplet vaporization physics play a fundamental role in determining the stability behavior of liquid fuel rocket motors. This paper gives an overview of work in progress on design of a numerical algorithm for practical studies of combustion instabilities in liquid rocket motors. For flexibility, the algorithm is composed of semi-independent solution modules, accounting for different physical processes. Current findings are report and future work is indicated. The main emphasis of this research is the development of an efficient treatment to interactions between acoustic fields and liquid fuel/oxidizer sprays.

  10. High Power Diode Laser-Treated HP-HVOF and Twin Wire Arc-Sprayed Coatings for Fossil Fuel Power Plants

    NASA Astrophysics Data System (ADS)

    Mann, B. S.

    2013-08-01

    This article deals with high power diode laser (HPDL) surface modification of twin wire arc-sprayed (TWAS) and high pressure high velocity oxy-fuel (HP-HVOF) coatings to combat solid particle erosion occurring in fossil fuel power plants. To overcome solid particle impact wear above 673 K, Cr3C2-NiCr-, Cr3C2-CoNiCrAlY-, and WC-CrC-Ni-based HVOF coatings are used. WC-CoCr-based HVOF coatings are generally used below 673 K. Twin wire arc (TWA) spraying of Tafa 140 MXC and SHS 7170 cored wires is used for a wide range of applications for a temperature up to 1073 K. Laser surface modification of high chromium stainless steels for steam valve components and LPST blades is carried out regularly. TWA spraying using SHS 7170 cored wire, HP-HVOF coating using WC-CoCr powder, Ti6Al4V alloy, and high chromium stainless steels (X20Cr13, AISI 410, X10CrNiMoV1222, 13Cr4Ni, 17Cr4Ni) were selected in the present study. Using robotically controlled parameters, HPDL surface treatments of TWAS-coated high strength X10CrNiMoV1222 stainless steel and HP-HVOF-coated AISI 410 stainless steel samples were carried out and these were compared with HPDL-treated high chromium stainless steels and titanium alloy for high energy particle impact wear (HEPIW) resistance. The HPDL surface treatment of the coatings has improved the HEPIW resistance manifold. The improvement in HPDL-treated stainless steels and titanium alloys is marginal and it is not comparable with that of HPDL-treated coatings. These coatings were also compared with "as-sprayed" coatings for fracture toughness, microhardness, microstructure, and phase analyses. The HEPIW resistance has a strong relationship with the product of fracture toughness and microhardness of the HPDL-treated HP-HVOF and TWAS SHS 7170 coatings. This development opens up a possibility of using HPDL surface treatments in specialized areas where the problem of HEPIW is very severe. The HEPIW resistance of HPDL-treated high chromium stainless steels and

  11. High-speed visualization of fuel spray impingement in the near-wall region using a DISI injector

    NASA Astrophysics Data System (ADS)

    Kawahara, N.; Kintaka, K.; Tomita, E.

    2017-02-01

    We used a multi-hole injector to spray isooctane under atmospheric conditions and observed droplet impingement behaviors. It is generally known that droplet impact regimes such as splashing, deposition, or bouncing are governed by the Weber number. However, owing to its complexity, little has been reported on microscopic visualization of poly-dispersed spray. During the spray impingement process, a large number of droplets approach, hit, then interact with the wall. It is therefore difficult to focus on a single droplet and observe the impingement process. We solved this difficulty using high-speed microscopic visualization. The spray/wall interaction processes were recorded by a high-speed camera (Shimadzu HPV-X2) with a long-distance microscope. We captured several impinging microscopic droplets. After optimizing the magnification and frame rate, the atomization behaviors, splashing and deposition, were recorded. Then, we processed the images obtained to determine droplet parameters such as the diameter, velocity, and impingement angle. Based on this information, the critical threshold between splashing and deposition was investigated in terms of the normal and parallel components of the Weber number with respect to the wall. The results suggested that, on a dry wall, we should set the normal critical Weber number to 300.

  12. Fundamental studies of spray combustion

    SciTech Connect

    Li, S.C.; Libby, P.A.; Williams, F.A.

    1997-12-31

    Our research on spray combustion involves both experiment and theory and addresses the characteristics of individual droplets and of sprays in a variety of flows: laminar and turbulent, opposed and impinging. Currently our focus concerns water and fuel sprays in two stage laminar flames, i.e., flames arising, for example from a stream of fuel and oxidizer flowing opposite to an air stream carrying a water spray. Our interest in these flames is motivated by the goals of reducing pollutant emissions and extending the range of stable spray combustion. There remains considerable research to be carried out in order to achieve these goals. Thus far our research on the characteristics of sprays in turbulent flows has been limited to nonreacting jets impinging on a plate but this work will be extended to opposed flows with and without a flame. In the following we discuss details of these studies and our plans for future work.

  13. The droplet group microexplosions in water-in-oil emulsion sprays and their effects on diesel engine combustion

    SciTech Connect

    Sheng, H.Z.; Chen, L.; Zhang, Z.P.; Wu, C.K.; An, C.; Cheng, C.Q.

    1994-12-31

    To clarify the combustion mechanism of water-in-diesel fuel emulsion sprays and to evaluate the possible benefit of emulsions in practical usage, combustion bomb experiments, dynamic engine tests, and computer simulation were carried out, and some useful conclusions have been reached. The droplet group (lump-fashioned) microexplosions in water-in-diesel fuel emulsion sprays on an eddy-size scale during the atomization, evaporation, and combustion processes in a high-pressure, high-temperature bomb were observed with a multipulsed, off-axis, image-plane, ruby laser holocamera and a high-speed camera. The explosions eject droplet fragments from the spray region to several millimeters away, improving the fuel-air mixing process and speeding up the flame propagation. A no-water layer formed by a Hill vortex was also observed in emulsion droplets. The ambient temperature has the most important influence on the occurrence and violence of the microexplosion. Road-load-simulation engine tests were carried out on a dynamic engine test bed. The experimental results show that emulsion fuels have no significant influence on fuel consumption and reduce engine torque if no adjustment is made for the injection system, but that smoke emission is much improved when emulsion fuel is used. The combustion characteristics and the rate of heat release are also analyzed to reveal the difference between emulsion and diesel fuel. The relationships between the optimum water percentages and fuel consumption under various operating conditions were analyzed by numerical combustion modeling.

  14. Chemical compatibility and properties of suspension plasma-sprayed SrTiO3-based anodes for intermediate-temperature solid oxide fuel cells

    NASA Astrophysics Data System (ADS)

    Zhang, Shan-Lin; Li, Cheng-Xin; Li, Chang-Jiu

    2014-10-01

    La-doped strontium titanate (LST) is a promising, redox-stable perovskite material for direct hydrocarbon oxidation anodes in intermediate-temperature solid oxide fuel cells (IT-SOFCs). In this study, nano-sized LST and Sm-doped ceria (SDC) powders are produced by the sol-gel and glycine-nitrate processes, respectively. The chemical compatibility between LST and electrolyte materials is studied. A LST-SDC composite anode is prepared by suspension plasma spraying (SPS). The effects of annealing conditions on the phase structure, microstructure, and chemical stability of the LST-SDC composite anode are investigated. The results indicate that the suspension plasma-sprayed LST-SDC anode has the same phase structure as the original powders. LST exhibits a good chemical compatibility with SDC and Mg/Sr-doped lanthanum gallate (LSGM). The anode has a porosity of ∼40% with a finely porous structure that provides high gas permeability and a long three-phase boundary for the anode reaction. Single cells assembled with the LST-SDC anode, La0.8Sr0.2Ga0.8Mg0.2O3 electrolyte, and La0.8Sr0.2CoO3-SDC cathode show a good performance at 650-800 °C. The annealing reduces the impedances due to the enhancement in the bonding between the particles in the anode and interface of anode and LSGM electrolyte, thus improving the output performance of the cell.

  15. Surface characteristic of chemically converted graphene coated low carbon steel by electro spray coating method for polymer electrolyte membrane fuel cell bipolar plate.

    PubMed

    Kim, Jungsoo; Kim, Yang Do; Nam, Dae Geun

    2013-05-01

    Graphene was coated on low carbon steel (SS400) by electro spray coating method to improve its properties of corrosion resistance and contact resistance. Exfoliated graphite was made of the graphite by chemical treatment (Chemically Converted Graphene, CCG). CCG is distributed using dispersing agent, and low carbon steel was coated with diffuse graphene solution by electro spray coating method. The structure of the CCG was analyzed using XRD and the coating layer of surface was analyzed using SEM. Analysis showed that multi-layered graphite structure was destroyed and it was transformed in to fine layers graphene structure. And the result of SEM analysis on the surface and the cross section, graphene layer was uniformly formed with 3-5 microm thickness on the surface of substrate. Corrosion resistance test was applied in the corrosive solution which is similar to the polymer electrolyte membrane fuel cell (PEMFC) stack inside. And interfacial contact resistance (ICR) test was measured to simulate the internal operating conditions of PEMFC stack. As a result of measuring corrosion resistance and contact resistance, it could be confirmed that low carbon steel coated with CCG was revealed to be more effective in terms of its applicability as PEMFC bipolar plate.

  16. Investigation into the diffusion and oxidation behavior of the interface between a plasma-sprayed anode and a porous steel support for solid oxide fuel cells

    NASA Astrophysics Data System (ADS)

    Zhang, Shan-Lin; Li, Cheng-Xin; Li, Chang-Jiu; Liu, Meilin; Yang, Guan-Jun

    2016-08-01

    Porous metal-supported solid oxide fuel cells (SOFCs) have attracted much attention because their potential to dramatically reduce the cost while enhancing the robustness and manufacturability. In particular, 430 ferritic steel (430L) is one of the popular choice for SOFC support because of its superior performance and low cost. In this study, we investigate the oxidation and diffusion behavior of the interface between a Ni-based anode and porous 430L support exposed to a humidified (3% H2O) hydrogen atmosphere at 700 °C. The Ni-GDC (Ce0.8Gd0.2O2-δ) cermet anodes are deposited on the porous 430L support by atmospheric plasma spraying (APS). The effect of exposure time on the microstructure and phase structure of the anode and the supports is studied and the element diffusion across the support/anode interface is characterized. Results indicate that the main oxidation product of the 430L support is Cr2O3, and that Cr and Fe will diffuse to the anode and the diffusion thickness increases with the exposure time. The diffusion thickness of Cr and Fe reach about 5 and 2 μm, respectively, after 1000 h exposure. However, the element diffusion and oxidation has little influence on the area-specific resistance, indicating that the porous 430L steel and plasma sprayed Ni-GDC anode are promising for durable SOFCs.

  17. Development of Apparatus for Microgravity Experiments on Evaporation and Combustion of Palm Methyl Ester Droplet in High-Pressure Environments

    NASA Astrophysics Data System (ADS)

    Suzuki, Masato; Nomura, Hiroshi; Hashimoto, Nozomu

    New apparatus for microgravity experiments was developed in order to obtain fundamental data of single droplet evaporation and combustion of palm methyl ester (PME) for understanding PME spray combustion in internal combustion engines. n-hexadecane droplet combustion and evaporation experiments were also performed to obtain single-component fuel data. Combustion experiments were performed at atmospheric pressure and room temperature. For droplet evaporation experiments, ambient temperature and pressure were varied from 473 to 873 K and 0.10 to 4.0 MPa, respectively. Microgravity conditions were employed for evaporation experiments to prevent natural convection. Droplet diameter history of a burning PME droplet is similar to that of n-hexadecane. Droplet diameter history of an evaporating PME droplet is different from that of n-hexadecane at low ambient temperatures. In the latest stage of PME droplet evaporation, temporal evaporation constant decreases remarkably. At ambient temperatures sufficiently above the boiling temperature of PME components, droplet diameter history of PME and n-hexadecane are similar to each other. Corrected evaporation lifetime τ of PME at 873 K as a function of ambient pressure was obtained at normal and microgravity. At normal gravity, τ monotonically decreases with ambient pressure. On the other hand, at microgravity, τ increases with ambient pressure, and then decreases.

  18. Effect of ultrasonic cavitation erosion on corrosion behavior of high-velocity oxygen-fuel (HVOF) sprayed near-nanostructured WC-10Co-4Cr coating.

    PubMed

    Hong, Sheng; Wu, Yuping; Zhang, Jianfeng; Zheng, Yugui; Qin, Yujiao; Lin, Jinran

    2015-11-01

    The effect of ultrasonic cavitation erosion on electrochemical corrosion behavior of high-velocity oxygen-fuel (HVOF) sprayed near-nanostructured WC-10Co-4Cr coating in 3.5 wt.% NaCl solution, was investigated using free corrosion potential, potentiodynamic polarization curves and electrochemical impedance spectroscopy (EIS) in comparison with stainless steel 1Cr18Ni9Ti. The results showed that cavitation erosion strongly enhanced the cathodic current density, shifted the free corrosion potential in the anodic direction, and reduced the magnitude of impedance of the coating. The impedance of the coating decreased more slowly under cavitation conditions than that of the stainless steel 1Cr18Ni9Ti, suggesting that corrosion behavior of the coating was less affected by cavitation erosion than that of the stainless steel.

  19. Slurry Erosion Behavior of F6NM Stainless Steel and High-Velocity Oxygen Fuel-Sprayed WC-10Co-4Cr Coating

    NASA Astrophysics Data System (ADS)

    Cui, S. Y.; Miao, Q.; Liang, W. P.; Huang, B. Z.; Ding, Z.; Chen, B. W.

    2016-12-01

    WC-10Co-4Cr coating was applied to the surface of F6NM stainless steel by high-velocity oxygen-fuel spraying. The slurry erosion behavior of the matrix and coating was examined at different rotational speeds using a self-made machine. This experiment effectively simulates real slurry erosion in an environment with high silt load. At low velocity (<6 m/s), the main failure mechanism was cavitation. Small bubbles acted as an air cushion, obstructing direct contact between sand and the matrix surface. However, at velocity above 9 m/s, abrasive wear was the dominant failure mechanism. The results indicate that WC-10Co-4Cr coating significantly improved the slurry resistance at higher velocity, because it created a thin and dense WC coating on the surface.

  20. Slurry Erosion Behavior of F6NM Stainless Steel and High-Velocity Oxygen Fuel-Sprayed WC-10Co-4Cr Coating

    NASA Astrophysics Data System (ADS)

    Cui, S. Y.; Miao, Q.; Liang, W. P.; Huang, B. Z.; Ding, Z.; Chen, B. W.

    2017-02-01

    WC-10Co-4Cr coating was applied to the surface of F6NM stainless steel by high-velocity oxygen-fuel spraying. The slurry erosion behavior of the matrix and coating was examined at different rotational speeds using a self-made machine. This experiment effectively simulates real slurry erosion in an environment with high silt load. At low velocity (<6 m/s), the main failure mechanism was cavitation. Small bubbles acted as an air cushion, obstructing direct contact between sand and the matrix surface. However, at velocity above 9 m/s, abrasive wear was the dominant failure mechanism. The results indicate that WC-10Co-4Cr coating significantly improved the slurry resistance at higher velocity, because it created a thin and dense WC coating on the surface.

  1. Effects of turbulence mixing, variable properties, and vaporization on spray droplet combustion

    NASA Technical Reports Server (NTRS)

    Kim, Y. M.; Chung, T. J.

    1990-01-01

    Combustion of liquid fuels in the form of spray droplets is simulated numerically. Various vaporization models are examined as to their performance in finite element calculations involving a turbulent flow field. The Eulerian coordinate for the gas and Lagrangian coordinate for the liquid spray droplets are coupled through source terms being updated in the equations of continuity, momentum, and energy. The k-epsilon and modified eddy breakup models are used for simulating turbulent spray combustion flow field. Numerical results for the droplet trajectories, droplet heating, recirculation characteristics, and effects of evaporation models are evaluated. It is also shown that the finite element method is advantageous in dealing with complex geometries, complex boundary conditions, adaptive unstructured grids.

  2. Prontonic ceramic membrane fuel cells with layered GdBaCo 2O 5+ x cathode prepared by gel-casting and suspension spray

    NASA Astrophysics Data System (ADS)

    Lin, Bin; Zhang, Shangquan; Zhang, Linchao; Bi, Lei; Ding, Hanping; Liu, Xingqin; Gao, Jianfeng; Meng, Guangyao

    In order to develop a simple and cost-effective route to fabricate protonic ceramic membrane fuel cells (PCMFCs) with layered GdBaCo 2O 5+ x (GBCO) cathode, a dense BaZr 0.1Ce 0.7Y 0.2O 3- δ (BZCY7) electrolyte was fabricated on a porous anode by gel-casting and suspension spray. The porous NiO-BaZr 0.1Ce 0.7Y 0.2O 3- δ (NiO-BZCY7) anode was directly prepared from metal oxide (NiO, BaCO 3, ZrO 2, CeO 2 and Y 2O 3) by a simple gel-casting process. A suspension of BaZr 0.1Ce 0.7Y 0.2O 3- δ powders synthesized by gel-casting was then employed to deposit BaZr 0.1Ce 0.7Y 0.2O 3- δ (BZCY7) thin layer by pressurized spray process on NiO-BZCY7 anode. The bi-layer with 10 μm dense BZCY7 electrolyte was obtained by co-sintering at 1400 °C for 5 h. With layered GBCO cathode synthesized by gel-casting on the bi-layer, single cells were assembled and tested with H 2 as fuel and the static air as oxidant. An open-circuit potential of 0.98 V, a maximum power density of 266 mW cm -2, and a low polarization resistance of the electrodes of 0.16 Ω cm 2 was achieved at 700 °C.

  3. Spray combustion model improvement study, 1

    NASA Technical Reports Server (NTRS)

    Chen, C. P.; Kim, Y. M.; Shang, H. M.

    1993-01-01

    This study involves the development of numerical and physical modeling in spray combustion. These modeling efforts are mainly motivated to improve the physical submodels of turbulence, combustion, atomization, dense spray effects, and group vaporization. The present mathematical formulation can be easily implemented in any time-marching multiple pressure correction methodologies such as MAST code. A sequence of validation cases includes the nonevaporating, evaporating and_burnin dense_sprays.

  4. Large eddy simulations of partially premixed ethanol dilute spray flames using the flamelet generated manifold model

    NASA Astrophysics Data System (ADS)

    El-Asrag, Hossam A.; Braun, Markus; Masri, Assaad R.

    2016-07-01

    The paper presents Large Eddy Simulations (LESs) for the Sydney ethanol piloted turbulent dilute spray flames ETF2, ETF6, and ETF7. The Flamelet Generated Manifold (FGM) approach is employed to predict mixing and burning of the evaporating fuel droplets. A methodology to match the experimental inflow spray profiles is presented. The spray statistical time-averaged results show reasonable agreement with mean and RMS data. The Particle Size Distribution (PSD) shows a good match downstream of the nozzle exit and up to x/D = 10. At x/D = 20 and 30 the PSD is under-predicted for droplets with mean diameter D10 > 20μm and over-predicted for the smaller size droplets. The simulations reasonably predict the reported mean flame structure and length. The effect of increasing the carrier velocity (ETF2-ETF7) or decreasing the liquid fuel injection mass flow rate (ETF2-ETF6) is found to result in a leaner, shorter flame and stronger spray-flow interactions. Higher tendency to local extinction is observed for ETF7 which is closer to blow-off compared to ETF2 and has higher scalar dissipation rates, higher range of Stokes number, and faster droplet response. The possible sources of LES-FGM deviations from the measurements are discussed and highlighted. In particular, the spray time-averaged statistical error contribution is quantified and the impact of the inflow uncertainty is studied. Sensitivity analysis to the pre-vaporized nozzle fuel mass fraction show that such small inflow perturbations (by ± 2% for the ETF2 flame) have a strong impact on the flame structure, and the droplets' dynamics. Conditional scatter plots show that the flame exhibits wide range of mixing conditions and bimodal mixing lines particularly at upstream locations (x/D < 20), where the injected droplets are still penetrating the centerline. This is relaxed further downstream as droplets gradually evaporate and burn in a diffusion like mode.

  5. Enhanced performance of polybenzimidazole-based high temperature proton exchange membrane fuel cell with gas diffusion electrodes prepared by automatic catalyst spraying under irradiation technique

    NASA Astrophysics Data System (ADS)

    Su, Huaneng; Pasupathi, Sivakumar; Bladergroen, Bernard Jan; Linkov, Vladimir; Pollet, Bruno G.

    2013-11-01

    Gas diffusion electrodes (GDEs) prepared by a novel automatic catalyst spraying under irradiation (ACSUI) technique are investigated for improving the performance of phosphoric acid (PA)-doped polybenzimidazole (PBI) high temperature proton exchange membrane fuel cell (PEMFC). The physical properties of the GDEs are characterized by pore size distribution and scanning electron microscopy (SEM). The electrochemical properties of the membrane electrode assembly (MEA) with the GDEs are evaluated and analyzed by polarization curve, cyclic voltammetry (CV) and electrochemistry impedance spectroscopy (EIS). Effects of PTFE binder content, PA impregnation and heat treatment on the GDEs are investigated to determine the optimum performance of the single cell. At ambient pressure and 160 °C, the maximum power density can reach 0.61 W cm-2, and the current density at 0.6 V is up to 0.38 A cm-2, with H2/air and a platinum loading of 0.5 mg cm-2 on both electrodes. The MEA with the GDEs shows good stability for fuel cell operating in a short term durability test.

  6. Sensors in Spray Processes

    NASA Astrophysics Data System (ADS)

    Fauchais, P.; Vardelle, M.

    2010-06-01

    This paper presents what is our actual knowledge about sensors, used in the harsh environment of spray booths, to improve the reproducibility and reliability of coatings sprayed with hot or cold gases. First are described, with their limitations and precisions, the different sensors following the in-flight hot particle parameters (trajectories, temperatures, velocities, sizes, and shapes). A few comments are also made about techniques, still under developments in laboratories, to improve our understanding of coating formation such as plasma jet temperature measurements in non-symmetrical conditions, hot gases heat flux, particles flattening and splats formation, particles evaporation. Then are described the illumination techniques by laser flash of either cold particles (those injected in hot gases, or in cold spray gun) or liquid injected into hot gases (suspensions or solutions). The possibilities they open to determine the flux and velocities of cold particles or visualize liquid penetration in the core of hot gases are discussed. Afterwards are presented sensors to follow, when spraying hot particles, substrate and coating temperature evolution, and the stress development within coatings during the spray process as well as the coating thickness. The different uses of these sensors are then described with successively: (i) Measurements limited to particle trajectories, velocities, temperatures, and sizes in different spray conditions: plasma (including transient conditions due to arc root fluctuations in d.c. plasma jets), HVOF, wire arc, cold spray. Afterwards are discussed how such sensor data can be used to achieve a better understanding of the different spray processes, compare experiments to calculations and improve the reproducibility and reliability of the spray conditions. (ii) Coatings monitoring through in-flight measurements coupled with those devoted to coatings formation. This is achieved by either maintaining at their set point both in-flight and

  7. Mechanisms of spray formation and combustion from a multi-hole injector with E85 and gasoline

    SciTech Connect

    Aleiferis, P.G.; Serras-Pereira, J.; van Romunde, Z.; Caine, J.; Wirth, M.

    2010-04-15

    The spray formation and combustion characteristics of gasoline and E85 (85% ethanol, 15% gasoline) have been investigated using a multi-hole injector with asymmetric nozzle-hole arrangement. Experiments were carried out in a quiescent optical chamber using high-speed shadowgraphy (9 kHz) to characterise the spray sensitivity to both injector temperature and ambient pressure in the range of 20-120 C and 0.5, 1.0 bar. Spray-tip penetrations and 'umbrella' spray cone angles were calculated for all conditions. Phase Doppler Anemometry was also used to measure droplet sizes in the core of one of the spray plumes, 25 mm below the injector tip. To study the effect of fuel properties on vaporisation and mixture preparation under realistic operating conditions, a separate set of experiments was carried out in a direct-injection spark-ignition optical engine. The engine was run at 1500 RPM under cold and fully warmed-up conditions (20 C and 90 C) at part load and full load (0.5 and 1.0 bar intake pressure). Floodlit laser Mie-scattering images of the sprays on two orthogonal planes corresponding to the swirl and tumble planes of in-cylinder flow motion were acquired to study the full injection event and post-injection mixing stage. These were used to make comparisons with the static chamber sprays and to quantify the liquid-to-vapour phase evaporation process for both fuels by calculating the projected 'footprint' of the sprays at different conditions. Analysis of the macroscopic structure and turbulent primary break-up properties of the sprays was undertaken in light of jet exit conditions described in terms of non-dimensional numbers. The effects on stoichiometric combustion were investigated by imaging the natural flame chemiluminescence through the engine's piston crown (swirl plane) and by post-processing to derive flame growth rates and trajectories of flame motion. (author)

  8. Laser diagnostics of an evaporating electrospray

    NASA Astrophysics Data System (ADS)

    Yi, Tongxun

    2014-01-01

    An electrospray atomizer generates monodisperse, dilute sprays when working in the cone-jet mode. Evolution of an electrospray with droplet diameter below 10 μm is studied with phase Doppler particle analyzer (PDPA) and the exciplex-PLIF technique. The evaporation rate constant is determined from droplet velocity and diameter measured with a PDPA and is found to sharply increase with the velocity slip and the coflow temperature. Fluorescence around 400 nm, usually referred to as TMPD fluorescence, is calibrated with a heated, laminar, coflow vapor jet diluted with nitrogen. The TMPD fluorescence yield nonlinearly increases with temperature up to 538 K and then declines. Single-shot images show that fluorescence around 400 nm is mainly generated from TMPD vapor and that from droplets can be neglected as a first analysis; however, fluorescence around 490 nm, usually referred to as exciplex fluorescence, is generated from both droplets and fuel vapor immediately around droplets. Exciplex fluorescence is correlated with PDPA measurements and TMPD fluorescence. Effects of temperature, fuel composition, overlap of fluorescent spectra, and chemical equilibrium for exciplex formation are discussed. Technical challenges for quantitative exciplex-PLIF measurements are highlighted.

  9. Effects of turbulence and carrier fluid on simple, turbulent spray jet flames

    SciTech Connect

    Staarner, Sten H.; Gounder, James; Masri, Assaad R.

    2005-12-01

    This paper presents simultaneous LIF images of OH and the two-phase acetone fuel concentration as well as detailed single-point phase-Doppler measurements of velocity and droplet flux in three turbulent spray flames of acetone. This work forms part of a larger program to study spray jets and flames in a simple, well-defined geometry, aimed at providing a platform for developing and validating predictive tools for such flows. Spray flames that use nitrogen or air as droplet carrier are investigated and issues of flow field, droplet dispersion, size distribution, and evaporation are addressed. The joint OH/acetone concentration images reveal a substantial similarity to premixed flame behavior when the carrier stream is air. When the carrier is nitrogen, the reaction zone has a diffusion flame structure. There is no indication of individual droplet burning. The results show that evaporation occurs close to the jet centerline rather than in the outer shear layer. Turbulence does not have a significant impact on the evaporation rates. A small fraction of the droplets escapes the reaction zone unburned along the centerline and persists far downstream of the flame tip. The proportion of this droplet residue increases with shorter residence times as observed for the higher velocity flame.

  10. Hot air drum evaporator. [Patent application

    DOEpatents

    Black, R.L.

    1980-11-12

    An evaporation system for aqueous radioactive waste uses standard 30 and 55 gallon drums. Waste solutions form cascading water sprays as they pass over a number of trays arranged in a vertical stack within a drum. Hot dry air is circulated radially of the drum through the water sprays thereby removing water vapor. The system is encased in concrete to prevent exposure to radioactivity. The use of standard 30 and 55 gallon drums permits an inexpensive compact modular design that is readily disposable, thus eliminating maintenance and radiation build-up problems encountered with conventional evaporation systems.

  11. Development and validation of spray models for investigating diesel engine combustion and emissions

    NASA Astrophysics Data System (ADS)

    Som, Sibendu

    Diesel engines intrinsically generate NOx and particulate matter which need to be reduced significantly in order to comply with the increasingly stringent regulations worldwide. This motivates the diesel engine manufacturers to gain fundamental understanding of the spray and combustion processes so as to optimize these processes and reduce engine emissions. Strategies being investigated to reduce engine's raw emissions include advancements in fuel injection systems, efficient nozzle orifice design, injection and combustion control strategies, exhaust gas recirculation, use of alternative fuels such as biodiesel etc. This thesis explores several of these approaches (such as nozzle orifice design, injection control strategy, and biodiesel use) by performing computer modeling of diesel engine processes. Fuel atomization characteristics are known to have a significant effect on the combustion and emission processes in diesel engines. Primary fuel atomization is induced by aerodynamics in the near nozzle region as well as cavitation and turbulence from the injector nozzle. The breakup models that are currently used in diesel engine simulations generally consider aerodynamically induced breakup using the Kelvin-Helmholtz (KH) instability model, but do not account for inner nozzle flow effects. An improved primary breakup (KH-ACT) model incorporating cavitation and turbulence effects along with aerodynamically induced breakup is developed and incorporated in the computational fluid dynamics code CONVERGE. The spray simulations using KH-ACT model are "quasi-dynamically" coupled with inner nozzle flow (using FLUENT) computations. This presents a novel tool to capture the influence of inner nozzle flow effects such as cavitation and turbulence on spray, combustion, and emission processes. Extensive validation is performed against the non-evaporating spray data from Argonne National Laboratory. Performance of the KH and KH-ACT models is compared against the evaporating and

  12. Numerical Modeling of Suspension HVOF Spray

    NASA Astrophysics Data System (ADS)

    Jadidi, M.; Moghtadernejad, S.; Dolatabadi, A.

    2016-02-01

    A three-dimensional two-way coupled Eulerian-Lagrangian scheme is used to simulate suspension high-velocity oxy-fuel spraying process. The mass, momentum, energy, and species equations are solved together with the realizable k-ɛ turbulence model to simulate the gas phase. Suspension is assumed to be a mixture of solid particles [mullite powder (3Al2O3·2SiO2)], ethanol, and ethylene glycol. The process involves premixed combustion of oxygen-propylene, and non-premixed combustion of oxygen-ethanol and oxygen-ethylene glycol. One-step global reaction is used for each mentioned reaction together with eddy dissipation model to compute the reaction rate. To simulate the droplet breakup, Taylor Analogy Breakup model is applied. After the completion of droplet breakup, and solvent evaporation/combustion, the solid suspended particles are tracked through the domain to determine the characteristics of the coating particles. Numerical simulations are validated against the experimental results in the literature for the same operating conditions. Seven or possibly eight shock diamonds are captured outside the nozzle. In addition, a good agreement between the predicted particle temperature, velocity, and diameter, and the experiment is obtained. It is shown that as the standoff distance increases, the particle temperature and velocity reduce. Furthermore, a correlation is proposed to determine the spray cross-sectional diameter and estimate the particle trajectories as a function of standoff distance.

  13. The characteristics of alumina scales formed on HVOF-sprayed MCrAlY coatings[High Velocity Oxygen Fuel

    SciTech Connect

    Toma, D.; Brandl, W.; Koester, U.

    2000-02-01

    HVOF MCrAlY (M = Ni, Co) coatings were isothermally oxidized in synthetic air between 850 and 1050 C for times up to 167 hr. During thermal spraying, aluminum and yttrium oxidized to form a fine oxide dispersion. The HVOF MCrAlY coatings exhibited a microstructure similar to ODS alloys. The fine dispersion consisted of Al{sub 2}O{sub 3} and aluminum-yttrium oxides. The oxidation experiments showed that the oxidation rate of HVOF coatings was two times slower than the oxidation rate of VPS MCrAlY coatings. The oxidation mechanism changed mainly in the transient-stage (no metastable modification of Al{sub 2}O{sub 3} formed) and it was assumed that the oxide dispersion hindered diffusion of various elements from the bulk material during oxidation. The formation of the fine oxide dispersion also influenced the adherence of the oxide scale. The microstructures of the transient oxide scales were examined by X-ray diffraction (XRD) scanning electron microscopy (SEM), and transmission electron microscopy (TEM).

  14. Processing-Microstructure-Property Relationships for Cold Spray Powder Deposition of Al-Cu Alloys

    DTIC Science & Technology

    2015-06-01

    Characteristics Cold spray is one many types of thermal spray processes, such as plasma spray, flame spray, and high velocity oxygen fuel spraying...MICROSTRUCTURE-PROPERTY RELATIONSHIPS FOR COLD SPRAY POWDER DEPOSITION OF Al-Cu ALLOYS by Jeremy D. Leazer June 2015 Thesis Advisor: Sarath K...3. REPORT TYPE AND DATES COVERED Master’s Thesis 4. TITLE AND SUBTITLE PROCESSING-MICROSTRUCTURE-PROPERTY RELATIONSHIPS FOR COLD SPRAY POWDER

  15. LSPRAY: Lagrangian Spray Solver for Applications With Parallel Computing and Unstructured Gas-Phase Flow Solvers

    NASA Technical Reports Server (NTRS)

    Raju, Manthena S.

    1998-01-01

    Sprays occur in a wide variety of industrial and power applications and in the processing of materials. A liquid spray is a phase flow with a gas as the continuous phase and a liquid as the dispersed phase (in the form of droplets or ligaments). Interactions between the two phases, which are coupled through exchanges of mass, momentum, and energy, can occur in different ways at different times and locations involving various thermal, mass, and fluid dynamic factors. An understanding of the flow, combustion, and thermal properties of a rapidly vaporizing spray requires careful modeling of the rate-controlling processes associated with the spray's turbulent transport, mixing, chemical kinetics, evaporation, and spreading rates, as well as other phenomena. In an attempt to advance the state-of-the-art in multidimensional numerical methods, we at the NASA Lewis Research Center extended our previous work on sprays to unstructured grids and parallel computing. LSPRAY, which was developed by M.S. Raju of Nyma, Inc., is designed to be massively parallel and could easily be coupled with any existing gas-phase flow and/or Monte Carlo probability density function (PDF) solver. The LSPRAY solver accommodates the use of an unstructured mesh with mixed triangular, quadrilateral, and/or tetrahedral elements in the gas-phase solvers. It is used specifically for fuel sprays within gas turbine combustors, but it has many other uses. The spray model used in LSPRAY provided favorable results when applied to stratified-charge rotary combustion (Wankel) engines and several other confined and unconfined spray flames. The source code will be available with the National Combustion Code (NCC) as a complete package.

  16. Suspension Plasma Sprayed Sr2Fe1.4Mo0.6O6- δ Electrodes for Solid Oxide Fuel Cells

    NASA Astrophysics Data System (ADS)

    Zhang, Shan-Lin; Zhang, Ai-Ping; Li, Cheng-Xin; Yang, Guan-Jun; Li, Chang-Jiu

    2017-02-01

    In this study, suspension plasma spraying (SPS) was applied to deposit double perovskite Sr2Fe1.4Mo0.6O6- δ (SFM) which can be used as both cathode and anode for solid oxide fuel cells. The effects of SFM concentration on the electrode phase composition, microstructure, and catalytic performance were investigated. The electrodes showed a dense structure when it was deposited at a concentration of 0.05 mol/L. The cathode performance was limited by the limited three-phase boundaries and poor gas diffusion. At 750 °C, cathode polarization ( R pc) was 0.19 Ω cm2. When the SFM concentration increased to 0.075 mol/L, the deposits revealed a porous microstructure with well-bonded fine particles. As a result, the Rpc decreased significantly to 0.078 Ω cm2 at 750 °C. However, when the SFM concentration was further increased to 0.1 mol/L, the R pc increased owing to the limited interface bonding between the non-molten particles. As a result, it was found that the SFM suspension concentration should be optimized to achieve a highly active SFM by SPS process. Moreover, when the optimized deposit was employed as an anode and tested in a hydrogen atmosphere, it showed anode polarization resistance (Rpa) of 1.5 Ω cm2 at 750 °C.

  17. An easy and innovative method based on spray-pyrolysis deposition to obtain high efficiency cathodes for Solid Oxide Fuel Cells

    NASA Astrophysics Data System (ADS)

    dos Santos-Gómez, L.; Porras-Vázquez, J. M.; Martín, F.; Ramos-Barrado, J. R.; Losilla, E. R.; Marrero-López, D.

    2016-07-01

    A novel electrode preparation method based on the spray-pyrolysis deposition of metal nitrate solutions onto a porous electrolyte scaffold is proposed. This method has been proved with different cathode materials, usually used in Solid Oxide Fuel Cells, such as La0.8Sr0.2MnO3-δ and La0.6Sr0.4Co1-xFexO3-δ (x = 0, 0.2, 0.8 and 1). The electrode microstructure is composed by two layers; the inner layer is a porous electrolyte scaffold homogeneously coated by cathode nanoparticles, providing an increased number of triple phase boundary sites for oxygen reduction, whereas, the top layer is formed by only cathode nanoparticles and acts mainly as a current collector. Polarization resistance values as low as 0.07 and 1.0 Ω cm2 at 600 and 450 °C, respectively, are obtained at open circuit voltage. This alternative approach has several advantages with respect to the traditional wet infiltration method for large area electrode fabrication, such as higher reproducibility, shorter preparation time in a single thermal deposition step, and easy implementation at industrial scale as a continuous process.

  18. Suspension Plasma Sprayed Sr2Fe1.4Mo0.6O6-δ Electrodes for Solid Oxide Fuel Cells

    NASA Astrophysics Data System (ADS)

    Zhang, Shan-Lin; Zhang, Ai-Ping; Li, Cheng-Xin; Yang, Guan-Jun; Li, Chang-Jiu

    2017-01-01

    In this study, suspension plasma spraying (SPS) was applied to deposit double perovskite Sr2Fe1.4Mo0.6O6-δ (SFM) which can be used as both cathode and anode for solid oxide fuel cells. The effects of SFM concentration on the electrode phase composition, microstructure, and catalytic performance were investigated. The electrodes showed a dense structure when it was deposited at a concentration of 0.05 mol/L. The cathode performance was limited by the limited three-phase boundaries and poor gas diffusion. At 750 °C, cathode polarization (R pc) was 0.19 Ω cm2. When the SFM concentration increased to 0.075 mol/L, the deposits revealed a porous microstructure with well-bonded fine particles. As a result, the Rpc decreased significantly to 0.078 Ω cm2 at 750 °C. However, when the SFM concentration was further increased to 0.1 mol/L, the R pc increased owing to the limited interface bonding between the non-molten particles. As a result, it was found that the SFM suspension concentration should be optimized to achieve a highly active SFM by SPS process. Moreover, when the optimized deposit was employed as an anode and tested in a hydrogen atmosphere, it showed anode polarization resistance (Rpa) of 1.5 Ω cm2 at 750 °C.

  19. Evaporating firewalls

    NASA Astrophysics Data System (ADS)

    Van Raamsdonk, Mark

    2014-11-01

    In this note, we begin by presenting an argument suggesting that large AdS black holes dual to typical high-energy pure states of a single holographic CFT must have some structure at the horizon, i.e. a fuzzball/firewall, unless the procedure to probe physics behind the horizon is state-dependent. By weakly coupling the CFT to an auxiliary system, such a black hole can be made to evaporate. In a case where the auxiliary system is a second identical CFT, it is possible (for specific initial states) that the system evolves to precisely the thermofield double state as the original black hole evaporates. In this case, the dual geometry should include the "late-time" part of the eternal AdS black hole spacetime which includes smooth spacetime behind the horizon of the original black hole. Thus, if a firewall is present initially, it evaporates. This provides a specific realization of the recent ideas of Maldacena and Susskind that the existence of smooth spacetime behind the horizon of an evaporating black hole can be enabled by maximal entanglement with a Hawking radiation system (in our case the second CFT) rather than prevented by it. For initial states which are not finely-tuned to produce the thermofield double state, the question of whether a late-time infalling observer experiences a firewall translates to a question about the gravity dual of a typical high-energy state of a two-CFT system.

  20. Droplet evaporation with complexity of evaporation modes

    NASA Astrophysics Data System (ADS)

    Hwang, In Gyu; Kim, Jin Young; Weon, Byung Mook

    2017-01-01

    Evaporation of a sessile droplet often exhibits a mixed evaporation mode, where the contact radius and the contact angle simultaneously vary with time. For sessile water droplets containing polymers with different initial polymer concentrations, we experimentally study their evaporation dynamics by measuring mass and volume changes. We show how diffusion-limited evaporation governs droplet evaporation, regardless of the complexity of evaporation behavior, and how the evaporation rate depends on the polymer concentration. Finally, we suggest a unified expression for a diffusion-limited evaporation rate for a sessile droplet with complexity in evaporation dynamics.

  1. Dispersion and evaporation of droplets amended with adjuvants on soybeans

    USDA-ARS?s Scientific Manuscript database

    Increased use of adjuvants to improve pesticide spray application efficiency is hindered by a lack of knowledge to enhance droplet adhesion. Dispersion and evaporation of single 300 µm droplets amended with four different spray adjuvants deposited at four different soybean plant locations were inves...

  2. Spray combustion modeling

    NASA Technical Reports Server (NTRS)

    Bellan, J.

    1997-01-01

    Concern over the future availability of high quality liquid fuels or use in furnaces and boilers prompted the U. S. Department of Energy (DOE) to consider alternate fuels as replacements for the high grade liquid fuels used in the 1970's and 1980's. Alternate fuels were defined to be combinations of a large percentage of viscous, low volatility fuels resulting from the low end of distillation mixed with a small percentage of relatively low viscosity, high volatility fuels yielded by the high end of distillation. The addition of high volatility fuels was meant to promote desirable characteristics to a fuel that would otherwise be difficult to atomize and burn and whose combustion would yield a high amount of pollutants. Several questions thus needed to be answered before alternate fuels became commercially viable. These questions were related to fuel atomization, evaporation, ignition, combustion and pollutant formation. This final report describes the results of the most significant studies on ignition and combustion of alternative fuels.

  3. Aerothermal modeling program, phase 2. Element C: Fuel injector-air swirl characterization

    NASA Technical Reports Server (NTRS)

    Mostafa, A. A.; Mongia, H. C.; Mcdonnell, V. G.; Samuelsen, G. S.

    1986-01-01

    The main objectives of the NASA-sponsored Aerothermal Modeling Program, Phase 2--Element C, are experimental evaluation of the air swirler interaction with a fuel injector in a simulated combustor chamber, assessment of the current two-phase models, and verification of the improved spray evaporation/dispersion models. This experimental and numerical program consists of five major tasks. Brief descriptions of the five tasks are given.

  4. Digital Image Processing application to spray and flammability studies

    NASA Technical Reports Server (NTRS)

    Hernan, M. A.; Parikh, P.; Sarohia, V.

    1985-01-01

    Digital Image Processing has been integrated into a new technique for measurements of fuel spray characteristics. The advantages of this technique are: a wide dynamic range of droplet sizes, accounting for nonspherical droplet shapes not possible with other spray assessment techniques. Finally, the technique has been applied to the study of turbojet engine fuel nozzle atomization performance with Jet A and antimisting fuel.

  5. Brief Communication: A Simplified Approach to Transient Convective Droplet Evaporation and Burning

    NASA Technical Reports Server (NTRS)

    Madooglu, K.; Karagozian, A. R.

    1994-01-01

    Empirical correlations for evaporation rates from single fuel droplets have existed since the 1930s. These correlations, which will be referred to in this article as Froessling/Ranz-Marshall types of correlations, are appropriate to the special cases of steady-state evaporation in the absence of chemical reaction. In a previous article by the authors, the quasi-steady evaporation and burning processes associated with a fuel drop in a convective environment are examined through a droplet model based on the boundary layer approach. For droplet Reynolds numbers of practical interest, this model produces very reasonable steady state as well as quasi-time-dependent droplet simulations, requiring relatively short computational times and yielding good agreement with the above-mentioned empirical correlations. The steady-state case, however, is usually relevant to practical combustor situations only when the drop has reached a nearly uniform temperature since the heating process of the drop cannot be considered to be quasi-steady. In the present study, the transient heating process of the droplet interior during evaporation and/or burning is taken into account, and thus calculations pertaining to the entire life-time of the droplet are carried out. It is of particular interest here to obtain simplified correlations to describe the transient behavior of evaporating and burning droplets; these may be incorporated with greater ease into spray calculations. Accordingly, we have chosen to use stagnation conditions in the present model in a modification of the Froessling/Ranz-Marshall correlations. These modified correlations, incorporating an effective transfer number, produce a fairly accurate representation of droplet evaporation and burning, while requiring only one tenth the computational effort used in a full boundary layer solution.

  6. Brief Communication: A Simplified Approach to Transient Convective Droplet Evaporation and Burning

    NASA Technical Reports Server (NTRS)

    Madooglu, K.; Karagozian, A. R.

    1994-01-01

    Empirical correlations for evaporation rates from single fuel droplets have existed since the 1930s. These correlations, which will be referred to in this article as Froessling/Ranz-Marshall types of correlations, are appropriate to the special cases of steady-state evaporation in the absence of chemical reaction. In a previous article by the authors, the quasi-steady evaporation and burning processes associated with a fuel drop in a convective environment are examined through a droplet model based on the boundary layer approach. For droplet Reynolds numbers of practical interest, this model produces very reasonable steady state as well as quasi-time-dependent droplet simulations, requiring relatively short computational times and yielding good agreement with the above-mentioned empirical correlations. The steady-state case, however, is usually relevant to practical combustor situations only when the drop has reached a nearly uniform temperature since the heating process of the drop cannot be considered to be quasi-steady. In the present study, the transient heating process of the droplet interior during evaporation and/or burning is taken into account, and thus calculations pertaining to the entire life-time of the droplet are carried out. It is of particular interest here to obtain simplified correlations to describe the transient behavior of evaporating and burning droplets; these may be incorporated with greater ease into spray calculations. Accordingly, we have chosen to use stagnation conditions in the present model in a modification of the Froessling/Ranz-Marshall correlations. These modified correlations, incorporating an effective transfer number, produce a fairly accurate representation of droplet evaporation and burning, while requiring only one tenth the computational effort used in a full boundary layer solution.

  7. Streamer Evaporation

    NASA Technical Reports Server (NTRS)

    Suess, S. T.; Wang, A.-H.; Wu, S. T.; Nerney, S. F.

    1998-01-01

    Evaporation is the consequence of heating near the top of streamers in ideal Magnetohydrodynamics (MHD) models, where the plasma is weakly contained by the magnetic field. Heating causes slow opening of field lines and release of new solar wind. It was discovered in simulations and, due to the absence of loss mechanisms, the ultimate end point is the complete evaporation of the streamer. Of course streamers do not behave in this way because there are losses by thermal conduction and radiation. Physically, heating is also expected to depend on ambient conditions. We use our global MHD model with thermal conduction to examine the effect of changing the heating scale height. We also apply and extend an analytic model of streamers developed by Pneuman (1968) to show that steady streamers are unable to contain plasma for temperatures near the cusp greater than approximately 2 x 10(exp 6) K.

  8. Flame propagation in heterogeneous mixtures of fuel drops and air

    NASA Technical Reports Server (NTRS)

    Myers, G. D.; Lefebvre, A. H.

    1984-01-01

    Photographic methods are used to measure flame speeds in flowing mixtures of fuel props and air at atmospheric pressure. The fuels employed include a conventional fuel oil plus various blends JP 7 with stocks containing single-ring and mullti-ring aromatics. The results for stoichiometric mixtures show that flame propagation cannot occur in mixtures containing mean drop sizes larger than 300 to 400 microns, depending on the fuel type. For smaller drop sizes, down to around 60 microns, flame speed is inversely proportional to drop size, indicating that evaporation rates are limiting to flame speed. Below around 60 microns, the curves of flame speed versus mean drop size flatten out, thereby demonstrating that for finely atomized sprays flame speeds are much less dependent on evaporation rates, and are governed primarily by mixing and/or chemical reaction rates. The fuels exhibiting the highest flame speeds are those containing multi-ring aromatics. This is attributed to the higher radiative heat flux emanating from their soot-bearing flames which enhances the rate of evaporation of the fuel drops approaching the flame front.

  9. Plasma Spray-CVD: A New Thermal Spray Process to Produce Thin Films from Liquid or Gaseous Precursors

    NASA Astrophysics Data System (ADS)

    Gindrat, M.; Höhle, H.-M.; von Niessen, K.; Guittienne, Ph.; Grange, D.; Hollenstein, Ch.

    2011-06-01

    New dedicated coating processes which are based on the well-known LPPS™ technology but operating at lower work pressure (100 Pa) are being actively developed. These hybrid technologies contribute to improve the efficiencies in the turbine industry such as aero-engines and land-based gas turbines. They also have a great potential in the domain of new energy concepts in applications like Solid Oxide Fuel Cells, membranes, and photovoltaic with the adoption of new ways of producing coatings by thermal spray. Such processes include Plasma Spray-Thin Film (PS-TF) which gives the possibility to coat thin and dense layers from splats through a classical thermal spray approach but at high velocities (400-800 m/s) and enthalpy (8000-15000 kJ/kg). Plasma Spray-PVD (PS-PVD) which allows producing thick columnar-structured Thermal Barrier Coatings (100-300 μm) from the vapor phase with the employment of the high enthalpy gun and specific powder feedstock material. On the other hand, the Plasma Spray-CVD (PS-CVD) process uses modified conventional thermal spray components operated below 100 Pa which allows producing CVD-like coatings (<1-10 μm) at higher deposition rates using liquid or gaseous precursors as feedstock material. The advantages of such thermal spray-enhanced CVD processes are the high ionization degree and high throughput for the deposition of thin layers. In this article, we present an overview of the possibilities and limitations encountered while producing thin film coatings using liquid and gaseous precursors with this new type of low pressure plasma spray equipment and point out the challenges faced to obtain efficient injection and mixing of the precursors in the plasma jet. In particular, SiO x thin films from Hexamethyldisiloxane (HMDSO or C6H18OSi2) can be deposited on wafers at deposition rates of up to 35 nm/s at an efficiency of about 50%. The process was also used for producing metal oxide coatings (Al2O3, ZnO, and SnO2) by evaporating different

  10. Leachate evaporation using landfill gas

    SciTech Connect

    White, T.M.; Grace, V.M.; Freivald, W.

    1996-05-01

    This paper describes a century-old technology with a new twist of using landfill gas as a fuel in an evaporation system. The system is designed to help landfills reduce the cost of leachate disposal while also destroying VOC emissions in an enclosed flare.

  11. Some Effects of Air Flow on the Penetration and Distribution of Oil Sprays

    NASA Technical Reports Server (NTRS)

    Rothrock, A M; Beardsley, E G

    1929-01-01

    Tests were made to determine the effects of air flow on the characteristics of fuel sprays from fuel injection valves. Curves and photographs are presented showing the airflow throughout the chamber and the effects of the air flow on the fuel spray characteristics. It was found that the moving air had little effect on the spray penetration except with the 0.006 inch orifice. The moving air did, however, affect the oil particles on the outside of the spray cone. After spray cut-off, the air flow rapidly distributed the atomized fuel throughout the spray chamber.

  12. An Overview of Spray Modeling With OpenNCC and its Application to Emissions Predictions of a LDI Combustor at High Pressure

    NASA Technical Reports Server (NTRS)

    Raju, M. S.

    2016-01-01

    The open national combustion code (Open- NCC) is developed with the aim of advancing the current multi-dimensional computational tools used in the design of advanced technology combustors. In this paper we provide an overview of the spray module, LSPRAY-V, developed as a part of this effort. The spray solver is mainly designed to predict the flow, thermal, and transport properties of a rapidly evaporating multi-component liquid spray. The modeling approach is applicable over a wide-range of evaporating conditions (normal, superheat, and supercritical). The modeling approach is based on several well-established atomization, vaporization, and wall/droplet impingement models. It facilitates large-scale combustor computations through the use of massively parallel computers with the ability to perform the computations on either structured & unstructured grids. The spray module has a multi-liquid and multi-injector capability, and can be used in the calculation of both steady and unsteady computations. We conclude the paper by providing the results for a reacting spray generated by a single injector element with 600 axially swept swirler vanes. It is a configuration based on the next-generation lean-direct injection (LDI) combustor concept. The results include comparisons for both combustor exit temperature and EINOX at three different fuel/air ratios.

  13. Comparision on dynamic behavior of diesel spray and rapeseed oil spray in diesel engine

    NASA Astrophysics Data System (ADS)

    Sapit, Azwan; Azahari Razali, Mohd; Faisal Hushim, Mohd; Jaat, Norrizam; Nizam Mohammad, Akmal; Khalid, Amir

    2017-04-01

    Fuel-air mixing is important process in diesel combustion. It significantly affects the combustion and emission of diesel engine. Biomass fuel has high viscosity and high distillation temperature and may negatively affect the fuel-air mixing process. Thus, study on the spray development and atomization of this type of fuel is important. This study investigates the atomization characteristics and droplet dynamic behaviors of diesel engine spray fuelled by rapeseed oil (RO) and comparison to diesel fuel (GO). Optical observation of RO spray was carried out using shadowgraph photography technique. Single nano-spark photography technique was used to study the characteristics of the spray while dual nano-spark shadowgraph technique was used to study the spray droplet behavior. Using in-house image processing algorithm, the images were processed and the boundary condition of each spray was also studied. The results show that RO has very poor atomization due to the high viscosity nature of the fuel when compared to GO. This is in agreement with the results from spray droplet dynamic behavior studies that shows due to the high viscosity, the RO spray droplets are large in size and travel downward, with very little influence of entrainment effect due to its large kinematic energy.

  14. Two-Dimensional Direct Numerical Simulations of Jet Spray under High Pressure

    SciTech Connect

    Nakamura, Mariko

    2008-09-01

    Two-dimensional direct numerical simulations are applied to a planar jet spray flow in order to investigate the effects of pressure on droplet behavior. For the gaseous phase, Eulerian mass, momentum, energy, and species conservation equations are solved. For the disperse phase, the fuel droplets are tracked individually in a Lagrangian manner. Concerning the vaporization of droplets, a nonequilibrium Langmuir-Knudsen evaporation model is adopted. The results show that the droplet mean diameter increases as the distance from the nozzle increases; however, because evaporation does not progress rapidly at normal temperature, the change in the droplet mean diameter with the increase in the distance from the nozzle is small for each pressure condition. The droplet mean velocity decreases as the droplets move downstream for each pressure condition, and the gradient of the droplet mean velocity toward the axial direction differs with each pressure condition.

  15. Development and application of a high-speed planar laser-induced fluorescence imaging system to evaluate liquid and vapor phases of sprays from a multi-hole diesel fuel injector

    NASA Astrophysics Data System (ADS)

    Parrish, S. E.; Zink, R. J.

    2013-02-01

    A high-speed imaging system capable of acquiring elastic scattering images and planar laser-induced fluorescence (PLIF) images in a near-simultaneous fashion has been developed. Acquiring both elastic scattering and PLIF images enables the liquid phase to be discriminated from the vapor phase. High-speed imaging allows the temporal evolution of flow structures to be evaluated. Images of sprays from a multi-hole diesel fuel injector operating under engine-like conditions were acquired. The vapor phase images reveal intricate fluid dynamic structures that exhibit a high degree of variability, indicative of a turbulent gas jet.

  16. Numerical Investigation of High Velocity Suspension Flame Spraying

    NASA Astrophysics Data System (ADS)

    Taleby, M.; Hossainpour, S.

    2012-12-01

    High-velocity suspension flame spraying (HVSFS) has recently developed as a possible alternative to conventional HVOF-spraying employing liquid suspensions instead of dry powder feedstock enables the use of nanoparticles. From the fluid dynamics point of view, the HVSFS system is complex and involves three-phase (gas, liquid and solid particles) turbulent flow, heat transfer, evaporation of the suspension solvent, chemical reactions of main fuel (propane) and suspension solvent (ethanol) and supersonic/subsonic flow transitions. Computational fluid dynamic techniques were carried out to solve the mass, momentum, and energy conservation equations. The realizable k-ɛ turbulence model was used to account for the effect of turbulence. The HVSFS process involves two combustion reactions. A primary combustion process is the premixed oxygen-propane reaction and secondary process is the non-premixed oxygen-gaseous ethanol reaction. For each reaction, one step global reaction, which takes dissociations and intermediate reactions into account, was derived from the equilibrium chemistry code developed by Gordon and McBride and eddy dissipation model was used to calculate the rate of reactions based on the transport equations for all species (10 species) mass fractions. Droplets were tracked in the continuum in a Lagrangian approach. In this paper, flow field inside and outside the gun simulated to provide clear and complete insight about the HVSFS processes. Moreover, the effect of some operative parameters (oxy-fuel flow rate, ethanol flow rate, droplets injection velocity and droplets size) on the gas flow field along the centerline and droplets evaporation behavior was discussed.

  17. Evaporation dehydrator

    SciTech Connect

    Bland, L.

    1985-08-06

    A method and apparatus for the treatment of oilfield heavy oil emulsions is provided. The method utilizes, in combination, the steps of evaporation, vapor/liquid separation, and solids settling to dehydrate, degassify and remove solids from the heavy oil emulsion and produce oil having less than 0.5% by volume basic solids and water. The apparatus comprises an insulated, horizontal, cylindrical vessel. Mounted in the upper end of the vessel chamber is an inclined, tubular member having a closed upper end and an open lower end. At its closed end, the member forms a receiving chamber. A mechanical foam breaker extends transversely across the interior of the tubular member, downstream of the chamber. A stack of angularly inclined, heated trays, arranged in zigzag fashion, are positioned beneath the tubular member, to provide an elongate flowpath. The lower end of the tubular member is positioned to feed onto the upper end of the first tray. The flowpath formed by the stack of trays terminates at a level above the bottom of the vessel, so that a quiescent settling sump is provided by the base of the vessel. The vessel includes a feed inlet opening into the receiving chamber, a vapor outlet leading from the top of said vessel, and liquid and solids outlets leading from the sump. A stream of pre-heated heavy oil emulsion is fed to the receiving chamber, wherein part of the contained water in the vapor form breaks out. The foaming stream is contained by the tubular member and is substantially disintegrated by the foam breaker. The stream then issues onto the upper end of the stack of trays and is heated as it passes as a shallow, broad layer over the trays, to gradually evaporate the remaining water from the emulsion and solids. The dehydrated solids are settled out in the sump, leaving oil containing less than 0.5% basic solids and water.

  18. Streamer Evaporation

    NASA Technical Reports Server (NTRS)

    Suess, Steven T.; Wang, A. H.; Wu, Shi T.; Nerney, S.

    1998-01-01

    Evaporation is the consequence of slow plasma heating near the tops of streamers where the plasma is only weakly contained by the magnetic field. The form it takes is the slow opening of field lines at the top of the streamer and transient formation of new solar wind. It was discovered in polytropic model calculations, where due to the absence of other energy loss mechanisms in magnetostatic streamers, its ultimate endpoint is the complete evaporation of the streamer. This takes, for plausible heating rates, weeks to months in these models. Of course streamers do not behave this way, for more than one reason. One is that there are losses due to thermal conduction to the base of the streamer and radiation from the transition region. Another is that streamer heating must have a characteristic time constant and depend on the ambient physical conditions. We use our global Magnetohydrodynamics (MHD) model with thermal conduction to examine a few examples of the effect of changing the heating scale height and of making ad hoc choices for how the heating depends on ambient conditions. At the same time, we apply and extend the analytic model of streamers, which showed that streamers will be unable to contain plasma for temperatures near the cusp greater than about 2xl0(exp 6) K. Slow solar wind is observed to come from streamers through transient releases. A scenario for this that is consistent with the above physical process is that heating increases the near-cusp temperature until field lines there are forced open. The subsequent evacuation of the flux tubes by the newly forming slow wind decreases the temperature and heating until the flux tubes are able to reclose. Then, over a longer time scale, heating begins to again refill the flux tubes with plasma and increase the temperature until the cycle repeats itself. The calculations we report here are first steps towards quantitative evaluation of this scenario.

  19. Physical mechanisms for atomization of a jet spray

    SciTech Connect

    Bower, G.; Chang, S.K.; Corradini, M.L.; El-Beshbeeshy, M.; Martin, J.K.; Krueger, J.

    1988-01-01

    Because combustion in direct injection engines is strongly influenced by the details of the fuel spray in thes engines, the authors have begun a broad research effort of jet breakup experiments and modelling of these high pressure sprays. The main objective of this effort is to better understand fuel injection from the study of the spray-jet breakup process and the associated fuel-oxidant mixing. The focus of this paper is the development of specific models for atomization of the spray-jet. These models are then compared to each other and to preliminary data from the spray-jet breakup experiments. Initial results indicate that KIVA with this proposed spray model shows good agreement with low pressure data (69 MPa) but underestimates spray penetration for higher pressures (104 MPa).

  20. Measurement of biodiesel blend and conventional diesel spray structure using x-ray radiography.

    SciTech Connect

    Kastengren, A. L.; Powell, C. F.; Wang, Y. J.; IM, K. S.; Wang, J.

    2009-11-01

    The near-nozzle structure of several nonevaporating biodiesel-blend sprays has been studied using X-ray radiography. Radiography allows quantitative measurements of the fuel distribution in sprays to be made with high temporal and spatial resolution. Measurements have been made at different values of injection pressure, ambient density, and with two different nozzle geometries to understand the influences of these parameters on the spray structure of the biodiesel blend. These measurements have been compared with corresponding measurements of Viscor, a diesel calibration fluid, to demonstrate the fuel effects on the spray structure. Generally, the biodiesel-blend spray has a similar structure to the spray of Viscor. For the nonhydroground nozzle used in this study, the biodiesel-blend spray has a slightly slower penetration into the ambient gas than the Viscor spray. The cone angle of the biodiesel-blend spray is generally smaller than that of the Viscor spray, indicating that the biodiesel-blend spray is denser than the Viscor spray. For the hydroground nozzle, both fuels produce sprays with initially wide cone angles that transition to narrow sprays during the steady-state portion of the injection event. These variations in cone angle with time occur later for the biodiesel-blend spray than for the Viscor spray, indicating that the dynamics of the injector needle as it opens are somewhat different for the two fuels.

  1. 40 CFR 86.1243-96 - Calculations; evaporative emissions.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ...) AIR PROGRAMS (CONTINUED) CONTROL OF EMISSIONS FROM NEW AND IN-USE HIGHWAY VEHICLES AND ENGINES (CONTINUED) Evaporative Emission Test Procedures for New Gasoline-Fueled, Natural Gas-Fueled, Liquefied Petroleum Gas-Fueled and Methanol-Fueled Heavy-Duty Vehicles § 86.1243-96 Calculations;...

  2. A Numerical Study of Spray Injected in a Gas Turbine Lean Pre-Mixed Pre-Vaporized Combustor

    NASA Astrophysics Data System (ADS)

    Amoresano, Amedeo; Cameretti, Maria Cristina; Tuccillo, Raffaele

    2015-04-01

    The authors have performed a numerical study to investigate the spray evolution in a modern gas turbine combustor of the Lean Pre-Mixed Pre-vaporized type. The CFD tool is able to simulate the injection conditions, by isolating and studying some specific phenomena. The calculations have been performed by using a 3-D fluid dynamic code, the FLUENT flow solver, by choosing the injection models on the basis of a comparative analysis with some experimental data, in terms of droplet diameters, obtained by PDA technique. In a first phase of the investigation, the numerical simulation refers to non-evaporating flow conditions, in order to validate the estimation of the fundamental spray parameters. Next, the calculations employ boundary conditions close to those occurring in the actual combustor operation, in order to predict the fuel vapour distribution throughout the premixing chamber. The results obtained allow the authors to perform combustion simulation in the whole domain.

  3. Vacuum plasma spray coating

    NASA Technical Reports Server (NTRS)

    Holmes, Richard R.; Mckechnie, Timothy N.

    1989-01-01

    Currently, protective plasma spray coatings are applied to space shuttle main engine turbine blades of high-performance nickel alloys by an air plasma spray process. Originally, a ceramic coating of yttria-stabilized zirconia (ZrO2.12Y2O3) was applied for thermal protection, but was removed because of severe spalling. In vacuum plasma spray coating, plasma coatings of nickel-chromium-aluminum-yttrium (NiCrAlY) are applied in a reduced atmosphere of argon/helium. These enhanced coatings showed no spalling after 40 MSFC burner rig thermal shock cycles between 927 C (1700 F) and -253 C (-423 F), while current coatings spalled during 5 to 25 test cycles. Subsequently, a process was developed for applying a durable thermal barrier coating of ZrO2.8Y2O3 to the turbine blades of first-stage high-pressure fuel turbopumps utilizing the enhanced NiCrAlY bond-coating process. NiCrAlY bond coating is applied first, with ZrO2.8Y2O3 added sequentially in increasing amounts until a thermal barrier coating is obtained. The enchanced thermal barrier coating has successfully passed 40 burner rig thermal shock cycles.

  4. LES/FMDF of High Speed Spray Combustion

    NASA Astrophysics Data System (ADS)

    Irannejad, Abolfazl; Jaberi, Farhad

    2013-11-01

    High speed evaporating and combusting sprays are computed with the hybrid two-phase large eddy simulation (LES)/filtered mass density function (FMDF) methodology. In this methodology, the resolved fluid velocity is obtained by solving the filtered form of the compressible Navier-Stokes equations with high-order finite difference schemes. The scalar (temperature and species mass fractions) field is obtained by solving the FMDF transport equation with a Lagrangian stochastic method. The spray is simulated with the Lagrangian droplets together with stochastic breakup and finite rate heat and mass transfer models. The liquid volume fraction is included in the LES/FMDF for denser spray regions. Simulations of high speed evaporating sprays with and without combustion for a range of gas and spray conditions indicate that the two-phase LES/FMDF results are consistent and compare well with the experimental results for global spray variables such as the spray penetration and flame lift-off lengths. The gas velocity and turbulence generated by the spray are found to be very significant in all simulated cases. A broad spectrum of droplet sizes is also found to be generated by the complex and coupled effects of the gas flow turbulence, droplet breakup, evaporation and combustion.

  5. Colloidal spray method for low cost thin coating deposition

    DOEpatents

    Pham, Ai-Quoc; Glass, Robert S.; Lee, Tae H.

    2002-01-01

    A dense or porous coating of material is deposited onto a substrate by forcing a colloidal suspension through an ultrasonic nebulizer and spraying a fine mist of particles in a carrier medium onto a sufficiently heated substrate. The spraying rate is essentially matched to the evaporation rate of the carrier liquid from the substrate to produce a coating that is uniformly distributed over the surface of the substrate. Following deposition to a sufficient coating thickness, a single sintering step may be used to produce a dense ceramic coating. Using this method, coatings ranging in thickness from about one to several hundred microns can be obtained. By using a plurality of compounds in the colloidal suspension, coatings of mixed composition can be obtained. By using a plurality of solutions and separate pumps and a single or multiple ultrasonic nebulizer(s), and varying the individual pumping rates and/or the concentrations of the solutions, a coating of mixed and discontinuously graded (e.g., stepped) or continuously graded layers may be obtained. This method is particularly useful for depositing ceramic coatings. Dense ceramic coating materials on porous substrates are useful in providing improved electrode performance in devices such as high power density solid oxide fuel cells. Dense ceramic coatings obtained by the invention are also useful for gas turbine blade coatings, sensors, steam electrolyzers, etc. The invention has general use in preparation of systems requiring durable and chemically resistant coatings, or coatings having other specific chemical or physical properties.

  6. Colloidal spray method for low cost thin coating deposition

    DOEpatents

    Pham, Ai-Quoc; Glass, Robert S.; Lee, Tae H.

    2005-01-25

    A dense or porous coating of material is deposited onto a substrate by forcing a colloidal suspension through an ultrasonic nebulizer and spraying a fine mist of particles in a carrier medium onto a sufficiently heated substrate. The spraying rate is essentially matched to the evaporation rate of the carrier liquid from the substrate to produce a coating that is uniformly distributed over the surface of the substrate. Following deposition to a sufficient coating thickness, a single sintering step may be used to produce a dense ceramic coating. Using this method, coatings ranging in thickness from about one to several hundred microns can be obtained. By using a plurality of compounds in the colloidal suspension, coatings of mixed composition can be obtained. By using a plurality of solutions and separate pumps and a single or multiple ultrasonic nebulizer(s), and varying the individual pumping rates and/or the concentrations of the solutions, a coating of mixed and discontinuously graded (e.g., stepped) or continuously graded layers may be obtained. This method is particularly useful for depositing ceramic coatings. Dense ceramic coating materials on porous substrates are useful in providing improved electrode performance in devices such as high power density solid oxide fuel cells. Dense ceramic coatings obtained by the invention are also useful for gas turbine blade coatings, sensors, steam electrolyzers, etc. The invention has general use in preparation of systems requiring durable and chemically resistant coatings, or coatings having other specific chemical or physical properties.

  7. Modeling Evaporation of Drops of Different Kerosenes

    NASA Technical Reports Server (NTRS)

    Bellan, Josette; Harstad, Kenneth

    2007-01-01

    A mathematical model describes the evaporation of drops of a hydrocarbon liquid composed of as many as hundreds of chemical species. The model is intended especially for application to any of several types of kerosenes commonly used as fuels. The concept of continuous thermodynamics, according to which the chemical composition of the evaporating multicomponent liquid is described by use of a probability distribution function (PDF). However, the present model is more generally applicable than is its immediate predecessor.

  8. Investigation of critical burning of fuel droplets

    NASA Technical Reports Server (NTRS)

    Faeth, G. M.

    1979-01-01

    The general problem of spray combustion was investigated. The combustion of bipropellent droplets; combustion of hydrozine fuels; and combustion of sprays were studied. A model was developed to predict mean velocities and temperatures in a combusting gas jet.

  9. Evaporator Development for an Evaporative Heat Pipe System

    NASA Technical Reports Server (NTRS)

    Peters, Leigh C.

    2004-01-01

    As fossil fuel resources continue to deplete, research for alternate power sources continues to develop. One of these alternate technologies is fuel cells. They are a practical fuel source able to provide significant amounts of power for applications from laptops to automobiles and their only byproduct is water. However, although this technology is over a century old and NASA has been working with it since the early 1960 s there is still room for improvement. The research I am involved in at NASA's Glenn Research Center is focusing on what is called a regenerative fuel cell system. The unique characteristic of this type of system is that it used an outside power source to create electrolysis of the water it produces and it then reuses the hydrogen and oxygen to continue producing power. The advantage of this type of system is that, for example, on space missions it can use solar power to recharge its gas supplies between periods when the object being orbited blocks out the sun. This particular system however is far from completion. This is because of the many components that are required to make up a fuel cell that need to be tested individually. The specific part of the system that is being worked on this summer of 2004 is the cooling system. The fuel cell stack, that is the part that actually creates the power, also produces a lot of heat. When not properly cooled, it has been known to cause fires which, needless to say are not conducive to the type of power that is trying to be created. In order to cool the fuel cell stack in this system we are developing a heat pipe cooling system. One of the main components of a heat pipe cooling system is what is known as the evaporator, and that is what happens to be the part of the system we are developing this summer. In most heat pipe systems the evaporator is a tube in which the working fluid is cooled and then re-circulated through the system to absorb more heat energy from the fuel cell stack. For this system, instead

  10. Evaporator Development for an Evaporative Heat Pipe System

    NASA Technical Reports Server (NTRS)

    Peters, Leigh C.

    2004-01-01

    As fossil fuel resources continue to deplete, research for alternate power sources continues to develop. One of these alternate technologies is fuel cells. They are a practical fuel source able to provide significant amounts of power for applications from laptops to automobiles and their only byproduct is water. However, although this technology is over a century old and NASA has been working with it since the early 1960 s there is still room for improvement. The research I am involved in at NASA's Glenn Research Center is focusing on what is called a regenerative fuel cell system. The unique characteristic of this type of system is that it used an outside power source to create electrolysis of the water it produces and it then reuses the hydrogen and oxygen to continue producing power. The advantage of this type of system is that, for example, on space missions it can use solar power to recharge its gas supplies between periods when the object being orbited blocks out the sun. This particular system however is far from completion. This is because of the many components that are required to make up a fuel cell that need to be tested individually. The specific part of the system that is being worked on this summer of 2004 is the cooling system. The fuel cell stack, that is the part that actually creates the power, also produces a lot of heat. When not properly cooled, it has been known to cause fires which, needless to say are not conducive to the type of power that is trying to be created. In order to cool the fuel cell stack in this system we are developing a heat pipe cooling system. One of the main components of a heat pipe cooling system is what is known as the evaporator, and that is what happens to be the part of the system we are developing this summer. In most heat pipe systems the evaporator is a tube in which the working fluid is cooled and then re-circulated through the system to absorb more heat energy from the fuel cell stack. For this system, instead

  11. Agricultural Spraying

    NASA Technical Reports Server (NTRS)

    1986-01-01

    AGDISP, a computer code written for Langley by Continuum Dynamics, Inc., aids crop dusting airplanes in targeting pesticides. The code is commercially available and can be run on a personal computer by an inexperienced operator. Called SWA+H, it is used by the Forest Service, FAA, DuPont, etc. DuPont uses the code to "test" equipment on the computer using a laser system to measure particle characteristics of various spray compounds.

  12. Fluoride-based, low temperature solid electrolyte fuel cell

    NASA Astrophysics Data System (ADS)

    Oh, Seajin; Otagawa, T.; Madou, M.

    Lanthanum fluoride electrolytes were tested to determine whether fluoride electrolytes can be used as fuel cell electrolytes at low temperatures. The planar-type fuel cell were operated in oxygen/hydrogen gases with nickel oxide/nickel as the anode and a perovskite structure oxide (La(0.6)Sr(0.4)CoO3) as the cathode. In order to reduce the fuel cell operating temperature while maintaining the highest possible current, various thin and thick film techniques were assessed. They include e-beam evaporation and dc plasma spray methods. Fuel cells incorporating plasma-sprayed LaF3 films yielded a short-circuit current density on the order of 0.4 mA/sq cm at 450 C, and the current density under an overpotential of 0.2V showed no sign of decay over 17 hours. In the co-ionic (fluoride and oxide ion) conduction mode, the lanthanum fluoride electrolyte based fuel cells could sustain current in oxygen/hydrogen gases.

  13. On the lifetimes of evaporating droplets

    NASA Astrophysics Data System (ADS)

    Wilson, Stephen; Stauber, Jutta; Duffy, Brian; Sefiane, Khellil

    2013-11-01

    The evaporation of a fluid droplet on a solid substrate is a practically important problem which has been the subject of considerable research in recent years, much of it motivated by a range of technological applications, such as the application of pesticides to plants, DNA microarray analysis, inkjet printing, micro-fabrication, and spray cooling. In particular, the lifetime of a fluid droplet is not only of fundamental scientific interest, but is also important in a number of technological applications, such as inkjet printing and spray cooling applications (in which shorter droplet lifetimes are often needed) and the application of pesticides to plants (in which longer droplet lifetimes are often needed). In this talk we will analyse the lifetimes of fluid droplets evaporating in a variety of modes and, in particular, show that the widely believed folklore that the lifetime of a droplet is always longer than that of an identical droplet evaporating in the constant radius (i.e. pinned contact line) mode and shorter than that of an identical droplet evaporating in the constant angle mode is not, in general, true.

  14. Spray chilling of lamb carcasses.

    PubMed

    Brown, T; Chourouzidis, K N; Gigiel, A J

    1993-01-01

    Two spray-chilling treatments were developed to improve appearance and reduce weight loss during lamb chilling. Rates of cooling and weight loss and meat quality were compared to conventionally chilled carcasses. The first treatment was an intermittent spray during the first 3 h of chilling. The second consisted of only two sprays at 2 h and 10 h post mortem. The conventional control was a two-stage process, with air at 10°C and 1 m/s up to 10 h post mortem, followed by air at 0°C and 1 m/s for a further 14 h. Both treatments significantly reduced weight loss at 24 h post mortem compared to conventional, from 2·20% to 0·86% and 1·20%, respectively. During a further 4 days storage, the savings were maintained, with weight losses being 3·97%, 2·97% and 3·19%, respectively. There were small (<1 h) but significantly reductions in the cooling times of spray-chilled loins and legs, attributed to sustained evaporative cooling of the continually wetted surfaces. No effects on texture or drip loss and only slight effects on surface lean and fat colour were found. Variation in texture between animals within treatments was far greater than between treatments and could not be accounted for by variations in cooling rates. Copyright © 1993. Published by Elsevier Ltd.

  15. No Heat Spray Drying Technology

    SciTech Connect

    Beetz, Charles

    2016-06-15

    No Heat Spray Drying Technology. ZoomEssence has developed our Zooming™ spray drying technology that atomizes liquids to powders at ambient temperature. The process of drying a liquid into a powder form has been traditionally achieved by mixing a heated gas with an atomized (sprayed) fluid within a vessel (drying chamber) causing the solvent to evaporate. The predominant spray drying process in use today employs air heated up to 400° Fahrenheit to dry an atomized liquid into a powder. Exposing sensitive, volatile liquid ingredients to high temperature causes molecular degradation that negatively impacts solubility, stability and profile of the powder. In short, heat is detrimental to many liquid ingredients. The completed award focused on several areas in order to advance the prototype dryer to a commercial scale integrated pilot system. Prior to the award, ZoomEssence had developed a prototype ‘no-heat’ dryer that firmly established the feasibility of the Zooming™ process. The award focused on three primary areas to improve the technology: (1) improved ability to formulate emulsions for specific flavor groups and improved understanding of the relationship of emulsion properties to final dry particle properties, (2) a new production atomizer, and (3) a dryer controls system.

  16. Predictions of spray combustion interactions

    NASA Technical Reports Server (NTRS)

    Shuen, J. S.; Solomon, A. S. P.; Faeth, G. M.

    1984-01-01

    Mean and fluctuating phase velocities; mean particle mass flux; particle size; and mean gas-phase Reynolds stress, composition and temperature were measured in stationary, turbulent, axisymmetric, and flows which conform to the boundary layer approximations while having well-defined initial and boundary conditions in dilute particle-laden jets, nonevaporating sprays, and evaporating sprays injected into a still air environment. Three models of the processes, typical of current practice, were evaluated. The local homogeneous flow and deterministic separated flow models did not provide very satisfactory predictions over the present data base. In contrast, the stochastic separated flow model generally provided good predictions and appears to be an attractive approach for treating nonlinear interphase transport processes in turbulent flows containing particles (drops).

  17. Self-healing atmospheric plasma sprayed Mn1.0Co1.9Fe0.1O4 protective interconnector coatings for solid oxide fuel cells

    NASA Astrophysics Data System (ADS)

    Grünwald, Nikolas; Sebold, Doris; Sohn, Yoo Jung; Menzler, Norbert Heribert; Vaßen, Robert

    2017-09-01

    Dense coatings on metallic interconnectors are necessary to suppress chromium poisoning of SOFC cathodes. Atmospherically plasma sprayed (APS) Mn1.0Co1.9Fe0.1O4 (MCF) protective layers demonstrated reduced chromium related degradation in laboratory and stack tests. Previous analyses revealed strong microstructural changes comparing the coating's as-sprayed and operated condition. This work concentrates on the layer-densification and crack-healing observed by annealing APS-MCF in air, which simulates the cathode operation conditions. The effect is described by a volume expansion induced by a phase transformation. Reducing conditions during the spray process lead to a deposition of the MCF in a metastable rock salt configuration. Annealing in air activates diffusion processes for a phase transformation to the low temperature stable spinel phase (T < 1050 °C). This transformation is connected to an oxygen incorporation which occurs at regions facing high oxygen partial pressures, as there are the sample surface, cracks and pore surfaces. Calculations reveal a volume expansion induced by the oxygen uptake which seals the cracks and densifies the coating. The process decelerates when the cracks are closed, as the gas route is blocked and further oxidation continues over solid state diffusion. The self-healing abilities of metastable APS coatings could be interesting for other applications.

  18. 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.

  19. Agrochemical spray drift; assessment and mitigation--a review.

    PubMed

    Felsot, Allan S; Unsworth, John B; Linders, Jan B H J; Roberts, Graham; Rautman, Dirk; Harris, Caroline; Carazo, Elizabeth

    2011-01-01

    During application of agrochemicals spray droplets can drift beyond the intended target to non-target receptors, including water, plants and animals. Factors affecting this spray drift include mode of application, droplet size, which can be modified by the nozzle types, formulation adjuvants, wind direction, wind speed, air stability, relative humidity, temperature and height of released spray relative to the crop canopy. The rate of fall of spray droplets depends upon the size of the droplets but is modified by entrainment in a mobile air mass and is also influenced by the rate of evaporation of the liquid constituting the aerosol. The longer the aerosol remains in the air before falling to the ground (or alternatively striking an object above ground) the greater the opportunity for it to be carried away from its intended target. In general, all size classes of droplets are capable of movement off target, but the smallest are likely to move the farthest before depositing on the ground or a non-target receptor. It is not possible to avoid spray drift completely but it can be minimized by using best-management practices. These include using appropriate nozzle types, shields, spray pressure, volumes per area sprayed, tractor speed and only spraying when climatic conditions are suitable. Field layout can also influence spray drift, whilst crop-free and spray-free buffer zones and windbreak crops can also have a mitigating effect. Various models are available to estimate the environmental exposure from spray drift at the time of application.

  20. Interaction of a polydisperse spray with vortices

    NASA Astrophysics Data System (ADS)

    Lacour, C.; Durox, D.; Ducruix, S.; Massot, M.

    2011-08-01

    The objective of the present work is to provide, through the association of optical diagnostics on a well-chosen experimental configuration, new insights into the coupling of a vortical gaseous flow with a polydisperse evaporating spray representative of practical injections. A cloud of droplets is injected in an inert laminar round jet, axisymmetric and pulsated, enabling the study of the interaction of strong-vorticity structures with a polydisperse spray. The experiment is a laboratory-scale representation of realistic injection configurations such as in engine combustion chambers or industrial burners. The chosen set-up leads to a well-controlled configuration and allows the coupling of two optical diagnostics, particle imaging velocimetry (PIV) and interferometric particle imaging (IPI), which leads to the study of both the flow dynamic and the droplet size distribution. The behaviour of droplets is analysed regarding their relaxing and evaporating properties. Size-conditioned preferential concentration of both weakly evaporating and strongly evaporating sprays is investigated. Droplet trajectories are also analysed by means of high-rate tomographic visualizations. The time history between their ejection from the nozzle and their interaction with the vortex is strongly related to the droplet preferential concentration and the observed heterogeneous repartition in the gas flow.

  1. Adjuvant Effects on Evaporation Time and Wetted Area of Droplets

    USDA-ARS?s Scientific Manuscript database

    Appropriate adjuvant selection for pesticide applications is central to improve spray performances on waxy leaves and to reduce off-target losses. Evaporation and deposition patterns of 500 µm sessile droplets with five classes of adjuvants on five different waxy plants were investigated. Droplets g...

  2. Extremely fine structured cathode for solid oxide fuel cells using Sr-doped LaMnO3 and Y2O3-stabilized ZrO2 nano-composite powder synthesized by spray pyrolysis

    NASA Astrophysics Data System (ADS)

    Shimada, Hiroyuki; Yamaguchi, Toshiaki; Sumi, Hirofumi; Nomura, Katsuhiro; Yamaguchi, Yuki; Fujishiro, Yoshinobu

    2017-02-01

    A solid oxide fuel cell (SOFC) for high power density operation was developed with a microstructure-controlled cathode using a nano-composite powder of Sr-doped LaMnO3 (LSM) and Y2O3-stabilized ZrO2 (YSZ) synthesized by spray pyrolysis. The individual LSM-YSZ nano-composite particles, formed by crystalline and amorphous nano-size LSM and YSZ particles, showed spherical morphology with uniform particle size. The use of this powder for cathode material led to an extremely fine microstructure, in which all the LSM and YSZ grains (approximately 100-200 nm) were highly dispersed and formed their own network structures. This microstructure was due to the two phase electrode structure control using the powder, namely, nano-order level in each particle and micro-order level between particles. An anode-supported SOFC with the LSM-YSZ cathode using humidified H2 as fuel and ambient air as oxidant exhibited high power densities, such as 1.29 W cm-2 under a voltage of 0.75 V and a maximum power density of 2.65 W cm-2 at 800 °C. Also, the SOFC could be stably operated for 250 h with no degradation, even at a high temperature of 800 °C.

  3. Evaporation in space manufacturing

    NASA Technical Reports Server (NTRS)

    Li, C. H.

    1974-01-01

    'Normal evaporation' equations for predicting the compositional changes with time and temperature have been developed and correlated with actual experimental data. An evaporative congruent temperature is defined and used to explain, predict, or plan space experiments on anomalous constitutional melting (on cooling) or solidification (on heating). Uneven evaporation causes reactive jetting forces capable of initiating new convection currents, nongravitational accelerations, surface vibrations, or other disturbances. Applications of evaporation to space manufacturing are described concerning evaporative purification, surface cooling, specimen selection, particles splitting, freezing data interpretation, material loss and dimensional control, and surface contamination or compositional changes.

  4. 40 CFR 86.1217-96 - Evaporative emission enclosure calibrations.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... measurements may be omitted if methanol-fueled vehicles will not be tested in the evaporative enclosure... well as hydrocarbons are present in the evaporative enclosure, the HFID hydrocarbon concentration measurement includes the partial response of the HFID to methanol plus the hydrocarbons. Determination of...

  5. 40 CFR 86.1207-96 - Sampling and analytical systems; evaporative emissions.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... (CONTINUED) Evaporative Emission Test Procedures for New Gasoline-Fueled, Natural Gas-Fueled, Liquefied Petroleum Gas-Fueled and Methanol-Fueled Heavy-Duty Vehicles § 86.1207-96 Sampling and analytical systems... analyzers. (1) For gasoline-, liquefied petroleum gas-, natural gas- and methanol-fueled vehicles a...

  6. Arc spraying in China

    NASA Astrophysics Data System (ADS)

    Liu, Xianjun

    2001-03-01

    Although are spraying is not a new technique, recent development of arc spraying device systems, spray wires, research on the coating mechanism, and the dynamic behavior of spraying make it a most active thermal spray process. In China, the arc spraying technique is the most efficient way for long life corrosion protection of steel structures. In addition, the arc spraying process is widely used for renovation and surface modification of machine components, mold making for plastic products, high-temperature corrosion resistance for waterwalls of boilers, antisliding coatings, self-lubricating coatings, etc.

  7. Decreasing luminescence lifetime of evaporating phosphorescent droplets

    NASA Astrophysics Data System (ADS)

    van der Voort, D. D.; Dam, N. J.; Sweep, A. M.; Kunnen, R. P. J.; van Heijst, G. J. F.; Clercx, H. J. H.; van de Water, W.

    2016-12-01

    Laser-induced phosphorescence has been used extensively to study spray dynamics. It is important to understand the influence of droplet evaporation in the interpretation of such measurements, as it increases luminescence quenching. By suspending a single evaporating n-heptane droplet in an acoustic levitator, the properties of lanthanide-complex europium-thenoyltrifluoroacetone-trioctylphosphine oxide (Eu-TTA-TOPO) phosphorescence are determined through high-speed imaging. A decrease was found in the measured phosphorescence decay coefficient (780 → 200 μs) with decreasing droplet volumes (10-9 → 10-11 m3) corresponding to increasing concentrations (10-4 → 10-2 M). This decrease continues up to the point of shell-formation at supersaturated concentrations. The diminished luminescence is shown not to be attributable to triplet-triplet annihilation, quenching between excited triplet-state molecules. Instead, the pure exponential decays found in the measurements show that a non-phosphorescent quencher, such as free TTA/TOPO, can be attributable to this decay. The concentration dependence of the phosphorescence lifetime can therefore be used as a diagnostic of evaporation in sprays.

  8. Foliar spray banding characteristics

    Treesearch

    A.R. Womac; C.W. Smith; Joseph E. Mulrooney

    2004-01-01

    Foliar spray banding was explored as a means of reducing peticide use compared to broadcast applications. Barious geometric spray patterns and delivery angles of foliar spray bands were investigated to increase spray deposits in a crop row at a constant spray rate of 94 L/ha. Wind-free laboratory results indicated that a banded application using three 65° hollow-cone...

  9. Microwave and Millimeter Wave Imaging of the Space Shuttle External Fuel Tank Spray on Foam Insulation (SOFI) using Synthetic Aperture Focusing Techniques (SAFT}

    NASA Technical Reports Server (NTRS)

    Case, J. T.; Robbins, J.; Kharkivskiy, S.; Hepburn, F.; Zoughi, R.

    2005-01-01

    The Space Shuttle Columbia s catastrophic failure is thought to have been caused by a dislodged piece of external tank spray on foam insulation (SOFI) striking the left wing of the orbiter causing significant damage to some of the reinforced carbodcarbon leading edge wing panels. Microwave and millimeter wave nondestructive evaluation methods have shown great potential for inspecting SOFI for the purpose of detecting anomalies such as small air voids that may cause separation of the SOFI from the external tank during a launch. These methods are capable of producing relatively high-resolution images of the interior of SOFI particularly when advanced imaging algorithms are incorporated into the overall system. To this end, synthetic aperture focusing techniques (SAFT) are being developed. This paper presents some of the preliminary results of this investigation using SAFT-based methods and microwave holography at relatively low frequencies illustrating their potential capabilities for operation at millimeter wave frequencies.

  10. Microwave and Millimeter Wave Imaging of the Space Shuttle External Fuel Tank Spray on Foam Insulation (SOFI) Using Synthetic Aperture Focusing Techniques (SAFT)

    NASA Astrophysics Data System (ADS)

    Case, J. T.; Robbins, J.; Kharkovsky, S.; Hepburn, F.; Zoughi, R.

    2006-03-01

    The Space Shuttle Columbia's catastrophic failure is thought to have been caused by a dislodged piece of external tank spray on foam insulation (SOFI) striking the left wing of the orbiter causing significant damage to some of the reinforced carbon/carbon leading edge wing panels. Microwave and millimeter wave nondestructive evaluation methods have shown great potential for inspecting SOFI for the purpose of detecting anomalies such as small air voids that may cause separation of the SOFI from the external tank during a launch. These methods are capable of producing relatively high-resolution images of the interior of SOFI particularly when advanced imaging algorithms are incorporated into the overall system. To this end, synthetic aperture focusing techniques (SAFT) are being developed. This paper presents some of the preliminary results of this investigation using SAFT-based methods and microwave holography at relatively low frequencies illustrating their potential capabilities for operation at millimeter wave frequencies.

  11. Determination of liquid-fuel prevaporization and premixing in gas-turbine combustion chambers

    NASA Astrophysics Data System (ADS)

    Mrugalla, J.

    A semiempirical mathematical model of the evaporation and distribution of liquid fuel in the prevaporization-premixing zone of a stationary gas turbine is developed, and the predictions obtained are compared with published experimental data and with the results of photographic, suction-probe, two-focus-laser-velocimeter, and light-scattering measurements on water sprays from 65-deg hollow-cone nozzles in a wind tunnel operating at 64 m/s. Good agreement is obtained, and the applicability of the model to the design of turbine combustion chambers giving lower NO(x) and CO emissions is indicated.

  12. Investigation of particulate formation during diesel spray combustion: CARS for diesel spray combustion. Final technical report

    SciTech Connect

    Boedeker, L.R.

    1991-09-01

    An experimental and analytical research program has been carried out whose objectives were to investigate strategies for using coherent anti-Stokes Raman spectroscopy (CARS) laser diagnostic techniques for detecting the vapor phase of liquid fuel sprays, determining fuel-air ratio and the degree of fuel pyrolysis. The extent to which CARS can provide valid vapor phase fuel measurements in the presence of droplets within the CARS resolution volume will determine its ultimate utility for engine measurements. Hence, the priority in this program was maintained toward investigating possible adverse droplet effects on CARS measurements. Droplets in a relevant size range (25-- 50 microns) were generated for convenience with a spray nozzle. Tests were conducted in a spray chamber at 1 atm pressure under near- saturated fuel vapor pressure conditions, with and without a toluene fuel spray turned on. For reasons of safety an inert gas, CO{sub 2}, was used to simulate O{sub 2}. It was necessary to provide reliable vapor phase CARS reference spectra for these spray studies in order to insure that spurious liquid effects were not present and known vapor phase spectra were attained. To provide these reference spectra the capability was developed of isolating, in a CARS test cell, the vapor phase of fuels that are normally liquids at room temperature and pressure. The cell could be evacuated with a vacuum pump and heated uniformly up to about 100 C. Hence, a capability was established to measure nonresonant and resonant vapor phase CARS features of normally liquid fuels over wide pressure and temperature range, needed for evaluating CARS fuel-air analysis strategies.

  13. Evaporation From Lake Superior

    NASA Astrophysics Data System (ADS)

    Spence, C.; Blanken, P.; Hedstrom, N.; Leshkevich, G.; Fortin, V.; Charpentier, D.; Haywood, H.

    2009-05-01

    Evaporation is a critical component of the water balance of each of the Laurentian Great Lakes, and understanding the magnitude and physical controls of evaporative water losses are important for several reasons. Recently, low water levels in Lakes Superior and Michigan/Huron have had socioeconomic, ecological, and even meteorological impacts (e.g. water quality and quantity, transportation, invasive species, recreation, etc.). The recent low water levels may be due to increased evaporation, but this is not known as operational evaporation estimates are currently calculated as the residual of water or heat budgets. Perhaps surprisingly, almost nothing is known about evaporation dynamics from Lake Superior and few direct measurements of evaporation have been made from any of the Laurentian Great Lakes. This research is the first to attempt to directly measure evaporation from Lake Superior by deploying eddy covariance instrumentation. Results of evaporation rates, their patterns and controlling mechanisms will be presented. The direct measurements of evaporation are used with concurrent satellite and climate model data to extrapolate evaporation measurements across the entire lake. This knowledge could improve predictions of how climate change may impact the lake's water budget and subsequently how the water in the lake is managed.

  14. Fullerene monolayer formation by spray coating.

    PubMed

    Cervenka, J; Flipse, C F J

    2010-02-10

    Many large molecular complexes are limited in thin film applications by their insufficient thermal stability, which excludes deposition via commonly used vapour phase deposition methods. Here we demonstrate an alternative way of monolayer formation of large molecules by a simple spray coating method under ambient conditions. This technique has been successfully applied on C(60) dissolved in toluene and carbon disulfide. Monolayer thick C(60) films have been formed on graphite and gold surfaces at particular deposition parameters, as confirmed by atomic force and scanning tunnelling microscopies. Structural and electronic properties of spray coated C(60) films on Au(111) have been found comparable to thermally evaporated C(60). We attribute the monolayer formation in spray coating to a crystallization process mediated by an ultrathin solution film on a sample surface.

  15. Evaporation and wetted area of single droplets on waxy and hairy leaf surfaces.

    PubMed

    Zhu, H; Yu, Y; Ozkan, H E; Derksen, R C; Krause, C R

    2008-01-01

    Understanding the evaporation of pesticide droplets and wetting of Leaf surfaces can increase foliar application efficiency and reduce pesticide use. Evaporation time and wetted area of single pesticide droplets on hairy and waxy geranium leaf surfaces were measured under the controlled conditions for five droplet sizes and three relative humidities. The sprays used to form droplets included water, a nonionic colloidal polymer drift retardant, an alkyl polyoxyethylene surfactant, and an insecticide. Adding the surfactant into spray mixtures greatly increased droplet wetted area on the surfaces while droplet evaporation time was greatly reduced. Adding the drift retardant into spray mixture slightly increased the droplet evaporation time and the wetted area. Also, droplets had Longer evaporation times on waxy leaves than on hairy leaves for all droplet diameters and all relative humidity conditions. Increasing relative humidity could increase the droplet evaporation time greatly but did not change the the wetted area. The droplet evaporation time and wetted area increased exponentially as the droplet size increased. Therefore, droplet size, surface characteristics of the target, relative humidity, and chemical composition of the spray mixtures (water alone, pesticide, additives) should be included as important factors that affect the efficacy and efficiency of pesticide applications.

  16. Optimal feature extraction for segmentation of Diesel spray images.

    PubMed

    Payri, Francisco; Pastor, José V; Palomares, Alberto; Juliá, J Enrique

    2004-04-01

    A one-dimensional simplification, based on optimal feature extraction, of the algorithm based on the likelihood-ratio test method (LRT) for segmentation in colored Diesel spray images is presented. If the pixel values of the Diesel spray and the combustion images are represented in RGB space, in most cases they are distributed in an area with a given so-called privileged direction. It is demonstrated that this direction permits optimal feature extraction for one-dimensional segmentation in the Diesel spray images, and some of its advantages compared with more-conventional one-dimensional simplification methods, including considerably reduced computational cost while accuracy is maintained within more than reasonable limits, are presented. The method has been successfully applied to images of Diesel sprays injected at room temperature as well as to images of sprays with evaporation and combustion. It has proved to be valid for several cameras and experimental arrangements.

  17. 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.

  18. Numerical Modeling of Spray Combustion with an Unstructured-Grid Method

    NASA Technical Reports Server (NTRS)

    Shang, H. M.; Chen, Y. S.; Liaw, P.; Shih, M. H.; Wang, T. S.

    1996-01-01

    The present unstructured-grid method follows strictly the basic finite volume forms of the conservation laws of the governing equations for the entire flow domain. High-order spatially accurate formulation has been employed for the numerical solutions of the Navier-Stokes equations. A two-equation k-epsilon turbulence model is also incorporated in the unstructured-grid solver. The convergence of the resulted linear algebraic equation is accelerated with preconditioned Conjugate Gradient method. A statistical spray combustion model has been incorporated into the present unstructured-grid solver. In this model, spray is represented by discrete particles, rather than by continuous distributions. A finite number of computational particles are used to predict a sample of total population of particles. Particle trajectories are integrated using their momentum and motion equations and particles exchange mass, momentum and energy with the gas within the computational cell in which they are located. The interaction calculations are performed simultaneously and eliminate global iteration for the two-phase momentum exchange. A transient spray flame in a high pressure combustion chamber is predicted and then the solution of liquid-fuel combusting flow with a rotating cup atomizer is presented and compared with the experimental data. The major conclusion of this investigation is that the unstructured-grid method can be employed to study very complicated flow fields of turbulent spray combustion. Grid adaptation can be easily achieved in any flow domain such as droplet evaporation and combustion zone. Future applications of the present model can be found in the full three-dimensional study of flow fields of gas turbine and liquid propulsion engine combustion chambers with multi-injectors.

  19. External characteristics of unsteady spray atomization from a nasal spray device.

    PubMed

    Fung, Man Chiu; Inthavong, Kiao; Yang, William; Lappas, Petros; Tu, Jiyuan

    2013-03-01

    The nasal route presents an enormous opportunity to exploit the highly vascularized respiratory airway for systemic drug delivery to provide more rapid onset of therapy and reduced drug degradation compared with conventional oral routes. The dynamics of atomization at low injection pressure is less known as typical spray atomization studies have focused on industrial applications such as fuel injection that are performed at much higher pressure. An experimental test station was designed in house and an alternative method to characterize the external spray is presented. This involved the use of high-speed camera to capture the temporal development of the spray as it is atomized through actuation of the spray device. An image-processing technique based on edge detection was developed to automate processing through the large number of images captured. The results showed that there are three main phases of spray development (prestable, stable, and poststable) that can be correlated by examining the spray width. A comparison with a human nasal cavity is made to put into perspective the dimensions and geometry that the spray atomization produces. This study aimed to extend the current existing set of data to contribute toward a better understanding in nasal spray drug delivery. Copyright © 2013 Wiley Periodicals, Inc.

  20. Microwave and Millimeter Wave Imaging of the Space Shuttle External Fuel Tank Spray on Foam Insulation (SOFI) Using Synthetic Aperture Focusing Techniques (SAFT)

    NASA Technical Reports Server (NTRS)

    Case, J. T.; Robbins, J.; Kharkovshy, S.; Hepburn, F. L.; Zoughi, R.

    2005-01-01

    The Space Shuttle Columbia's catastrophic failure is thought to have been caused by a dislodged piece of external tank SOFI (Spray On Foam Insulation) striking the left wing of the orbiter causing significant damage to some of the reinforced carbodcarbon leading edge wing panels. Microwave and millimeter wave nondestructive evaluation methods, have shown great potential for inspecting the SOFI for the purpose of detecting anomalies such as small voids that may cause separation of the foam from the external tank during the launch. These methods are capable of producing relatively high-resolution images of the interior of SOH particularly when advanced imaging algorithms are incorporated into the overall system. To this end, synthetic aperture focusing techniques are being deveioped for this purpose. These iechniqiies pradiice high-resolution images that are independent of the distance of the imaging probe to the SOFI with spatial resolution in the order of the half size of imaging probe aperture. At microwave and millimeter wave frequencies these apertures are inherently small resulting in high-resolution images. This paper provides the results of this investigation using 2D and 3D SAF based methods and holography. The attributes of these methods and a full discussion of the results will also be provided.

  1. Post-heat treatment pressure effect on performances of metal-supported solid oxide fuel cells fabricated by atmospheric plasma spraying

    NASA Astrophysics Data System (ADS)

    Tsai, Chun-Huang; Hwang, Chang-sing; Chang, Chun-Liang; Yu, Jen-Feng; Nien, Sheng-Hui

    2012-01-01

    The nickel metal-supported cells fabricated by atmospheric plasma spraying are post-heat treated in air at 960 °C for 2 h with different pressures. The current-voltage-power and AC impedance measurements show the prepared cell with an applied pressure of 450 g cm-2 in the post-heat treatment has a better electrochemical performance at test temperatures ≥ 650 °C. For test temperatures < 650 °C, the maximum power densities at 450 g cm-2 pressure are about the same as the maximum power densities at 1250 g cm-2 pressure. The SEM micrograph indicates that the cathode including the cathode interlayer and the cathode collector is the most porous region in the cell. AC impedance results show this cathode is the most sensitive part to the applied pressure in the post-heat treatment and the cell with 450 g cm-2 pressure has the smallest low frequency intercept R2 and the polarization resistance Rp at temperatures from 600 to 800 °C. The performance durability test of the cell post-heat treated at 450 g cm-2 pressure shows a degradation rate of 0.0087 mV h-1 or 0.0026 mW h-1 at 300 mA cm-2 constant current density and 750 °C test temperature.

  2. Microwave and Millimeter Wave Imaging of the Space Shuttle External Fuel Tank Spray on Foam Insulation (SOFI) Using Synthetic Aperture Focusing Techniques (SAFT)

    NASA Technical Reports Server (NTRS)

    Case, J. T.; Robbins, J.; Kharkovshy, S.; Hepburn, F. L.; Zoughi, R.

    2005-01-01

    The Space Shuttle Columbia's catastrophic failure is thought to have been caused by a dislodged piece of external tank SOFI (Spray On Foam Insulation) striking the left wing of the orbiter causing significant damage to some of the reinforced carbodcarbon leading edge wing panels. Microwave and millimeter wave nondestructive evaluation methods, have shown great potential for inspecting the SOFI for the purpose of detecting anomalies such as small voids that may cause separation of the foam from the external tank during the launch. These methods are capable of producing relatively high-resolution images of the interior of SOH particularly when advanced imaging algorithms are incorporated into the overall system. To this end, synthetic aperture focusing techniques are being deveioped for this purpose. These iechniqiies pradiice high-resolution images that are independent of the distance of the imaging probe to the SOFI with spatial resolution in the order of the half size of imaging probe aperture. At microwave and millimeter wave frequencies these apertures are inherently small resulting in high-resolution images. This paper provides the results of this investigation using 2D and 3D SAF based methods and holography. The attributes of these methods and a full discussion of the results will also be provided.

  3. Intermittent multijet sprays for improving mixture preparation with low-pressure injection systems

    NASA Astrophysics Data System (ADS)

    Panão, Miguel R. Oliveira; Moreira, António Luis N.; Durão, Diamantino F. G.

    2013-06-01

    In this work, the characteristics of droplets produced by a multijet impingement atomization process are measured with a Phase-Doppler Interferometer and statistically described using finite mixtures of weighted probability density functions. Through this statistical tool, drop size and axial velocity distributions are involved in the physical interpretation of the flow, instead of limiting it to first- and second-order distribution moments. Each group of droplets with similar size characteristics has been modeled by lognormal distributions and normal distributions relatively to drop axial velocity. The analysis based on finite mixtures identified three groups of droplets with similar size characteristics, although the group with smaller sizes is negligibly represented in the statistical finite mixture. Also, the lognormal standard deviation in all groups is well correlated with the corresponding geometric mean diameter allowing to simplify the description of the spray. In terms of axial velocity, mainly one distribution has been identified with a relatively constant standard deviation, and a characteristic velocity slightly dependent on the duty cycle associated with the spray intermittent condition. Furthermore, droplets characteristics are correlated with the heat transfer rate obtained for several operating conditions that maintain the surface temperature in steady-state at 125 °C. The effect of the time between consecutive injections is analyzed. Concerning the potential use of multijet impingement sprays for fuel injection systems, results evidence the importance of an interaction between thin liquid film heat transfer and droplets axial velocity for enhancing heat transfer and promote evaporation. This would decrease the amount of fuel deposited on interposed surfaces, thus, improving mixture preparation in low-pressure injection systems for internal combustion engines.

  4. An Interactive Microsoft(registered tm) Excel Program for Tracking a Single Evaporating Droplet in Crossflow

    NASA Technical Reports Server (NTRS)

    Liew, K. H.; Urip, E.; Yang, S. L.; Marek, C. J.

    2004-01-01

    Droplet interaction with a high temperature gaseous crossflow is important because of its wide application in systems involving two phase mixing such as in combustion requiring quick mixing of fuel and air with the reduction of pollutants and for jet mixing in the dilution zone of combustors. Therefore, the focus of this work is to investigate dispersion of a two-dimensional atomized and evaporating spray jet into a two-dimensional crossflow. An interactive Microsoft Excel program for tracking a single droplet in crossflow that has previously been developed will be modified to include droplet evaporation computation. In addition to the high velocity airflow, the injected droplets are also subjected to combustor temperature and pressure that affect their motion in the flow field. Six ordinary differential equations are then solved by 4th-order Runge-Kutta method using Microsoft Excel software. Microsoft Visual Basic programming and Microsoft Excel macrocode are used to produce the data and plot graphs describing the droplet's motion in the flow field. This program computes and plots the data sequentially without forcing the user to open other types of plotting programs. A user's manual on how to use the program is included.

  5. The Corrosion and Wear Performance of Microcrystalline WC-10Co-4Cr and Near-Nanocrystalline WC-17Co High Velocity Oxy-Fuel Sprayed Coatings on Steel Substrate

    NASA Astrophysics Data System (ADS)

    Saha, Gobinda C.; Khan, Tahir I.

    2010-11-01

    The study of near-nanocrystalline cermet composite coating was performed by depositing near-nanocrystalline WC-17Co powder using the high velocity oxy-fuel spraying technique. The WC-17Co powder consists of a core with an engineered near-nano-scale WC dispersion with a mean grain size 427 nm. The powder particle contains 6 wt pct of the ductile phase Co matrix mixed into the core to ensure that the reinforcing ceramic phase WC material is discontinuous to limit debridement during wear, while the remainder of the binding phase (11 wt pct) is applied as a coating on the powder particle to improve the ductility. The tribological properties of the coating, in terms of corrosion resistance, microhardness, and sliding abrasive wear, were studied and compared with those of an industrially standard microcrystalline WC-10Co-4Cr coating with a WC mean grain size 3 μm. Results indicated that the WC-17Co coating had superior wear and corrosion resistance compared to the WC-10Co-4Cr coating. The engineered WC-17Co powder with a duplex Co layer had prevented significant decarburization of the WC dispersion in the coating, thereby reducing the intersplat microporosity necessary for initiating microgalvanic cells. The improved wear resistance was attributed to the higher hardness value of the near-nanocrystalline WC-17Co coating.

  6. A parametric study on the effect of an acoustic field on a spray-fired, Rijke-tube, pulse combustor

    NASA Astrophysics Data System (ADS)

    Dubey, Raj Kumar

    A parametric experimental and theoretical study was performed to investigate the effects of an acoustic field on spray combustion characteristics. A Rijke-tube pulse combustor was constructed with variable length and a fixed diameter. A burner was designed for use with both gaseous and liquid fuel. An active control mechanism was implemented to externally control the acoustic field inside the combustor, as it was not possible to sustain natural oscillations with the long spray flame. Active control of the combustor was characterized for gaseous and spray flames applying both indirect control (in-line actuators) as well as direct control using external speakers. The size and velocity distribution of a nonreacting and reacting spray in an actively controlled acoustic field were measured using a two-component phase-Doppler particle analyzer (PDPA). The effects of burner location, frequency, and sound pressure level on the spray size and velocity distribution were studied. Based on the measured trends in the Dsb{32}, velocity, and data rate, mechanisms governing the interactions of the acoustic field with the spray were identified. These include atomization, evaporation and reaction, dispersion, droplet lifetime and flame lift. Also, the faster burning of the droplets was more prominent when the spray was placed at locations corresponding to the acoustic velocity antinode. A significant decrease in CO and NO emissions were found in the presence of an acoustic field as compared to the steady operation of the combustor. A mathematical model was developed to study the effects of frequency, sound pressure level, phase lag of droplet injection with respect to the acoustic velocity field, droplet injection velocity, and surrounding gas velocity on the Sauter-mean diameter of a reacting ethanol spray. The enhanced burning of the droplets are indicated by model results with higher initial slopes in the Dsb{32} profiles along the axial direction. For burner locations

  7. Evaporation, Boiling and Bubbles

    ERIC Educational Resources Information Center

    Goodwin, Alan

    2012-01-01

    Evaporation and boiling are both terms applied to the change of a liquid to the vapour/gaseous state. This article argues that it is the formation of bubbles of vapour within the liquid that most clearly differentiates boiling from evaporation although only a minority of chemistry textbooks seems to mention bubble formation in this context. The…

  8. Measure Guideline: Evaporative Condensers

    SciTech Connect

    German, A; Dakin, B.; Hoeschele, M.

    2012-03-01

    This measure guideline on evaporative condensers provides information on properly designing, installing, and maintaining evaporative condenser systems as well as understanding the benefits, costs, and tradeoffs. This is a prescriptive approach that outlines selection criteria, design and installation procedures, and operation and maintenance best practices.

  9. Evaporation, Boiling and Bubbles

    ERIC Educational Resources Information Center

    Goodwin, Alan

    2012-01-01

    Evaporation and boiling are both terms applied to the change of a liquid to the vapour/gaseous state. This article argues that it is the formation of bubbles of vapour within the liquid that most clearly differentiates boiling from evaporation although only a minority of chemistry textbooks seems to mention bubble formation in this context. The…

  10. Hair spray poisoning

    MedlinePlus

    ... this page: //medlineplus.gov/ency/article/002705.htm Hair spray poisoning To use the sharing features on this page, please enable JavaScript. Hair spray poisoning occurs when someone breathes in (inhales) ...

  11. Triamcinolone Nasal Spray

    MedlinePlus

    ... itchy nose and itchy, watery eyes caused by hay fever or other allergies. Triamcinolone nasal spray should not ... germs.Triamcinolone nasal spray controls the symptoms of hay fever and allergies but does not cure these conditions. ...

  12. Evaporative Cooling Membrane Device

    NASA Technical Reports Server (NTRS)

    Lomax, Curtis (Inventor); Moskito, John (Inventor)

    1999-01-01

    An evaporative cooling membrane device is disclosed having a flat or pleated plate housing with an enclosed bottom and an exposed top that is covered with at least one sheet of hydrophobic porous material having a thin thickness so as to serve as a membrane. The hydrophobic porous material has pores with predetermined dimensions so as to resist any fluid in its liquid state from passing therethrough but to allow passage of the fluid in its vapor state, thereby, causing the evaporation of the fluid and the cooling of the remaining fluid. The fluid has a predetermined flow rate. The evaporative cooling membrane device has a channel which is sized in cooperation with the predetermined flow rate of the fluid so as to produce laminar flow therein. The evaporative cooling membrane device provides for the convenient control of the evaporation rates of the circulating fluid by adjusting the flow rates of the laminar flowing fluid.

  13. Thermodynamic performance testing of the orbiter flash evaporator system

    NASA Technical Reports Server (NTRS)

    Jaax, J. R.; Melgares, M. A.; Frahm, J. P.

    1980-01-01

    System level testing of the space shuttle orbiter's development flash evaporator system (FES) was performed in a thermal vacuum chamber capable of simulating ambient ascent, orbital, and entry temperature and pressure profiles. The test article included the evaporator assembly, high load and topping exhaust duct and nozzle assemblies, and feedwater supply assembly. Steady state and transient heat load, water pressure/temperature and ambient pressure/temperature profiles were imposed by especially designed supporting test hardware. Testing in 1978 verified evaporator and duct heater thermal design, determined FES performance boundaries, and assessed topping evaporator plume characteristics. Testing in 1979 combined the FES with the other systems in the orbiter active thermal control subsystem (ATCS). The FES met or exceeded all nominal and contingency performance requirements during operation with the integrated ATCS. During both tests stability problems were encountered during steady state operations which resulted in subsequent design changes to the water spray nozzle and valve plate assemblies.

  14. 40 CFR 86.1243-96 - Calculations; evaporative emissions.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 19 2010-07-01 2010-07-01 false Calculations; evaporative emissions. 86.1243-96 Section 86.1243-96 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED... Petroleum Gas-Fueled and Methanol-Fueled Heavy-Duty Vehicles § 86.1243-96 Calculations;...

  15. Azelastine Nasal Spray

    MedlinePlus

    ... and replace with the pump unit. Prime the delivery system (pump unit) with four sprays or until a fine mist appears. If 3 days or more have elapsed since your last use of the nasal spray, reprime the pump with two sprays or until a fine mist appears.

  16. Remotely controlled spray gun

    NASA Technical Reports Server (NTRS)

    Cunningham, William C. (Inventor)

    1987-01-01

    A remotely controlled spray gun is described in which a nozzle and orifice plate are held in precise axial alignment by an alignment member, which in turn is held in alignment with the general outlet of the spray gun by insert. By this arrangement, the precise repeatability of spray patterns is insured.

  17. Development of thermally-sprayed Al-Cu-Fe-Cr quasicrystal coating

    NASA Astrophysics Data System (ADS)

    Setiamarga, Budi Hartono

    A class of quasicrystal alloys that has drawn a lot of attention is aluminum based quasicrystal alloys because they are hard, light weight, wear resistant, and have a non-stick property. Quasicrystalline materials in the form of coatings produced by thermal spray techniques have been developed to utilize their properties. The goal of this research has been to develop the knowledge necessary to produce good thermally sprayed Al-Cu-Fe-Cr quasicrystal coatings. Boron has been found to improve ductility, reduce porosity and increase hardness when added to other thermally sprayed powders, therefore, as part of this research, quasicrystal coatings containing boron will also be produced and evaluated. The first phase of this research utilized a fine QC-1 quasicrystal powder of Alsb{70.5}Cusb{10.1}Fesb{8.8}Crsb{10.6}. The addition of boron was done using mechanical mixing. The addition of boron in fused QC-1 powders shows that boron can reduce porosity and increase hardness. Due to difficulties with thermal spraying the fine QC-1 powder and evaporation of aluminum, a coarser QC-2 powder with similar composition to QC-1 powder was produced. QC-2 and boron modified QC-2 coatings have similar hardness and levels of porosity, around 11%, although boron modified QC-2 coatings proved to be more wear resistant than plain QC-2 coatings. Both coatings demonstrated a weak coating-substrate interface bonding. Laser heat treatment was used to reduce the porosity and strengthen the coating-substrate interface bonding. Laser treatment of QC-2 quasicrystal coatings resulted in harder and lower porosity coatings with better coating-substrate interface bonding. Unfortunately, hot-cracks in the coatings were also produced. Hot-cracks are undesireable because they decrease the coating's corrosion resistance. Thermal spraying using High Velocity Oxygen Fuel (HVOF) technique was done. It was used on QC-2 powder and QC-3 powder of composition Alsb{68.6}Cusb{10.8}Fesb{8.9}Crsb{9.7}Bsb{2.0}. This

  18. Flash evaporator systems test

    NASA Technical Reports Server (NTRS)

    Dietz, J. B.

    1976-01-01

    A flash evaporator heat rejection system representative of that proposed for the space shuttle orbiter underwent extensive system testing at the NASA Johnson Space Center (JSC) to determine its operational suitability and to establish system performance/operational characteristics for use in the shuttle system. During the tests the evaporator system demonstrated its suitability to meet the shuttle requirements by: (1) efficient operation with 90 to 95% water evaporation efficiency, (2) control of outlet temperature to 40 + or - 2 F for partial heat load operation, (3) stability of control system for rapid changes in Freon inlet temperature, and (4) repeated dormant-to-active device operation without any startup procedures.

  19. Spray combustion experiments and numerical predictions

    SciTech Connect

    Mularz, E.J.; Bulzan, D.L.; Chen, K.

    1993-01-01

    The next generation of commercial aircraft will include turbofan engines with performance significantly better than those in the current fleet. Control of particulate and gaseous emissions will also be an integral part of the engine design criteria. These performance and emission requirements present a technical challenge for the combustor: control of the fuel and air mixing and control of the local stoichiometry will have to be maintained much more rigorously than with combustors in current production. A better understanding of the flow physics of liquid fuel spray combustion is necessary. This paper describes recent experiments on spray combustion where detailed measurements of the spray characteristics were made, including local drop-size distributions and velocities. Also, an advanced combustor CFD code has been under development and predictions from this code are compared with experimental results. Studies such as these will provide information to the advanced combustor designer on fuel spray quality and mixing effectiveness. Validation of new fast, robust, and efficient CFD codes will also enable the combustor designer to use them as additional design tools for optimization of combustor concepts for the next generation of aircraft engines.

  20. Spray combustion experiments and numerical predictions

    NASA Technical Reports Server (NTRS)

    Mularz, Edward J.; Bulzan, Daniel L.; Chen, Kuo-Huey

    1993-01-01

    The next generation of commercial aircraft will include turbofan engines with performance significantly better than those in the current fleet. Control of particulate and gaseous emissions will also be an integral part of the engine design criteria. These performance and emission requirements present a technical challenge for the combustor: control of the fuel and air mixing and control of the local stoichiometry will have to be maintained much more rigorously than with combustors in current production. A better understanding of the flow physics of liquid fuel spray combustion is necessary. This paper describes recent experiments on spray combustion where detailed measurements of the spray characteristics were made, including local drop-size distributions and velocities. Also, an advanced combustor CFD code has been under development and predictions from this code are compared with experimental results. Studies such as these will provide information to the advanced combustor designer on fuel spray quality and mixing effectiveness. Validation of new fast, robust, and efficient CFD codes will also enable the combustor designer to use them as additional design tools for optimization of combustor concepts for the next generation of aircraft engines.

  1. Propellant vaporization as a criterion for rocket-engine design : experimental effect of fuel temperature on liquid-oxygen - heptane performance

    NASA Technical Reports Server (NTRS)

    Heidmann, M F

    1957-01-01

    Characteristic exhaust velocity of a 200-pound-thrust rocket engine was evaluated for fuel temperatures of -90 degrees, and 200 degrees f with a spray formed by two impinging heptane jets reacting in a highly atomized oxygen atmosphere. Tests covered a range of mixture ratios and chamber lengths. The characteristic exhaust-velocity efficiency increased 2 percent for a 290 degree f increase in fuel temperature. This increase in performance can be compared with that obtained by increasing chamber length by about 1/2 inch. The result agrees with the fuel-temperature effect predicted from an analysis based on droplet evaporation theory. Mixture ratio markedly affected characteristic exhaust velocity efficiency, but total flow rate and fuel temperature did not.

  2. A Novel Metered Dose Transdermal Spray Formulation for Oxybutynin

    PubMed Central

    Bakshi, A.; Bajaj, A.; Malhotra, G.; Madan, M.; Amrutiya, N.

    2008-01-01

    The objective of the present work was to develop a metered dose spray formulation for transdermal delivery of oxybutynin and to carry out the in vitro characterization of the optimized formulation. Oxybutynin release from a series of ethanol/acetone/methylal based formulations was assessed in vitro and the developed formulation was used for delivery from a metered dose spray. Various qualitative and quantitative parameters like spray pattern, particle size distribution, pH, evaporation time, pump seal efficiency test, average weight per metered dose, content per spray and content uniformity were evaluated. The different film forming agents were assessed and carbopol (0.5%) and lutrol (0.1%) were found to give good clarity of solution, evaporation rate, spray pattern and tackiness of the film. Diffusion studies of the optimized formulations through the semipermeable membrane showed the release of drug to the extent of almost 50% over a period of 24 h. Stability studies were conducted as per ICH guidelines and indicated that formulations were stable. Skin irritation studies were performed using rabbit as an animal model. The results obtained show that the metered dose transdermal spray formulation can be a promising and innovative therapeutic system for the transdermal administration of oxybutynin. PMID:21369433

  3. CAPSULE REPORT: EVAPORATION PROCESS

    EPA Science Inventory

    Evaporation has been an established technology in the metal finishing industry for many years. In this process, wastewaters containing reusable materials, such as copper, nickel, or chromium compounds are heated, producing a water vapor that is continuously removed and condensed....

  4. CAPSULE REPORT: EVAPORATION PROCESS

    EPA Science Inventory

    Evaporation has been an established technology in the metal finishing industry for many years. In this process, wastewaters containing reusable materials, such as copper, nickel, or chromium compounds are heated, producing a water vapor that is continuously removed and condensed....

  5. Research on electrostatic electrification during jet kerosene spraying

    NASA Astrophysics Data System (ADS)

    Liu, Quanzhen; Zhang, Wentian; Li, Yipeng; Sun, Keping

    2013-03-01

    Multiple electrostatic electrifications during aircraft fuelling process may cause a fire disaster or explosion, so study on the protection measure for electrostatic electrification is very important for the security of aircraft fuelling. This paper investigated the electrostatic voltage and charge of the fuel nozzle and metal parts during the fuel spraying by self-designed jet kerosene spraying electrostatic electrification test system. The experimental results indicate that the voltage on the fuel nozzle and metal parts is very dangerous for electrostatic safety if they are not reliably grounded.

  6. Plasma sprayed manganese-cobalt spinel coatings: Process sensitivity on phase, electrical and protective performance

    NASA Astrophysics Data System (ADS)

    Han, Su Jung; Pala, Zdenek; Sampath, Sanjay

    2016-02-01

    Manganese cobalt spinel (Mn1.5Co1.5O4, MCO) coatings are prepared by the air plasma spray (APS) process to examine their efficacy in serving as protective coatings from Cr-poisoning of the cathode side in intermediate temperature-solid oxide fuel cells (IT-SOFCs). These complex oxides are susceptible to process induced stoichiometric and phase changes which affect their functional performance. To critically examine these effects, MCO coatings are produced with deliberate modifications to the spray process parameters to explore relationship among process conditions, microstructure and functional properties. The resultant interplay among particle thermal and kinetic energies are captured through process maps, which serve to characterize the parametric effects on properties. The results show significant changes to the chemistry and phase composition of the deposited material resulting from preferential evaporation of oxygen. Post deposition annealing recovers oxygen in the coatings and allows partial recovery of the spinel phase, which is confirmed through thermo-gravimetric analysis (TGA)/differential scanning calorimetry (DSC), X-ray Diffraction (XRD), and magnetic hysteresis measurements. In addition, coatings with high density after sintering show excellent electrical conductivity of 40 S cm-1 at 800 °C while simultaneously providing requisite protection characteristics against Cr-poisoning. This study provides a framework for optimal evaluation of MCO coatings in intermediate temperature SOFCs.

  7. Spray formation of biodiesel-water in air-assisted atomizer using Schlieren photography

    NASA Astrophysics Data System (ADS)

    Amirnordin, S. H.; Khalid, A.; Sapit, A.; Salleh, H.; Razali, A.; Fawzi, M.

    2016-11-01

    Biodiesels are attractive renewable energy sources, particularly for industrial boiler and burner operators. However, biodiesels produce higher nitrogen oxide (NOx) emissions compared with diesel. Although water-emulsified fuels can lower NOx emissions by reducing flame temperature, its influence on atomization needs to be investigated further. This study investigates the effects of water on spray formation in air-assisted atomizers. The Schlieren method was used to capture the spray images in terms of tip penetration, spray angle, and spray area. The experiment used palm oil biodiesel at different blending ratios (B5, B10, and B15) and water contents (0vol%-15vol%). Results show that water content in the fuel increases the spray penetration and area but reduces the spray angle because of the changes in fuel properties. Therefore, biodiesel-water application is applicable to burner systems.

  8. Measure Guideline: Evaporative Condensers

    SciTech Connect

    German, A.; Dakin, B.; Hoeschele, M.

    2012-03-01

    The purpose of this measure guideline on evaporative condensers is to provide information on a cost-effective solution for energy and demand savings in homes with cooling loads. This is a prescriptive approach that outlines selection criteria, design and installation procedures, and operation and maintenance best practices. This document has been prepared to provide a process for properly designing, installing, and maintaining evaporative condenser systems as well as understanding the benefits, costs, and tradeoffs.

  9. Evaporation from microreservoirs.

    PubMed

    Lynn, N Scott; Henry, Charles S; Dandy, David S

    2009-06-21

    As a result of very large surface area to volume ratios, evaporation is of significant importance when dealing with lab-on-a-chip devices that possess open air/liquid interfaces. For devices utilizing a reservoir as a fluid delivery method to a microfluidic network, excessive evaporation can quickly lead to reservoir dry out and overall device failure. Predicting the rates of evaporation from these reservoirs is difficult because the position of the air/liquid interface changes with time as the volume of liquid in the reservoir decreases. Here we present a two-step method to accurately predict the rates of evaporation of such an interface over time. First, a simple method is proposed to determine the shape of an air/liquid meniscus in a reservoir given a specific liquid volume. Second, computational fluid dynamics simulations are used to calculate the instantaneous rate of evaporation for that meniscus shape. It is shown that the rate of evaporation is strongly dependent on the overall geometry of the system, enhanced in expanding reservoirs while suppressed in contracting reservoirs, where the geometry can be easily controlled with simple experimental methods. Using no adjustable parameters, the model accurately predicts the position of the inner moving contact line as a function of time following meniscus rupture in poly(dimethylsiloxane) reservoirs, and predicts the overall time for the persistence of liquid in those reservoirs to within 0.5 minutes. The methods in this study can be used to design holding reservoirs for lab-on-a-chip devices that involve no external control of evaporation, such that evaporation rates can be adjusted as necessary by modification of the reservoir geometry.

  10. Mixed feed evaporator

    DOEpatents

    Vakil, Himanshu B.; Kosky, Philip G.

    1982-01-01

    In the preparation of the gaseous reactant feed to undergo a chemical reaction requiring the presence of steam, the efficiency of overall power utilization is improved by premixing the gaseous reactant feed with water and then heating to evaporate the water in the presence of the gaseous reactant feed, the heating fluid utilized being at a temperature below the boiling point of water at the pressure in the volume where the evaporation occurs.

  11. Evaporation from microreservoirs†

    PubMed Central

    Lynn, N. Scott; Henry, Charles S.

    2010-01-01

    As a result of very large surface area to volume ratios, evaporation is of significant importance when dealing with lab-on-a-chip devices that possess open air/liquid interfaces. For devices utilizing a reservoir as a fluid delivery method to a microfluidic network, excessive evaporation can quickly lead to reservoir dry out and overall device failure. Predicting the rates of evaporation from these reservoirs is difficult because the position of the air/liquid interface changes with time as the volume of liquid in the reservoir decreases. Here we present a two-step method to accurately predict the rates of evaporation of such an interface over time. First, a simple method is proposed to determine the shape of an air/liquid meniscus in a reservoir given a specific liquid volume. Second, computational fluid dynamics simulations are used to calculate the instantaneous rate of evaporation for that meniscus shape. It is shown that the rate of evaporation is strongly dependent on the overall geometry of the system, enhanced in expanding reservoirs while suppressed in contracting reservoirs, where the geometry can be easily controlled with simple experimental methods. Using no adjustable parameters, the model accurately predicts the position of the inner moving contact line as a function of time following meniscus rupture in poly(dimethylsiloxane) reservoirs, and predicts the overall time for the persistence of liquid in those reservoirs to within 0.5 minutes. The methods in this study can be used to design holding reservoirs for lab-on-a-chip devices that involve no external control of evaporation, such that evaporation rates can be adjusted as necessary by modification of the reservoir geometry. PMID:19495463

  12. Evaporative cooling on a grooved surface. M.S. Thesis

    NASA Technical Reports Server (NTRS)

    Yoder, D.

    1979-01-01

    The transition point where water begins to accumulate on the surface during spray evaporative cooling was investigated experimentally to determine the temperatures and corresponding heat flux at which this transition occurs. Several pressure ranges were considered including one below the triple point of water. Additionally, the results using a grooved surface were compared to those using a smooth surface. It was determined that a grooved surface has no effect on the heat transfer.

  13. An evaporation model of multicomponent solution drops

    NASA Astrophysics Data System (ADS)

    Sartori, Silvana; Liñán, Amable; Lasheras, Juan C.

    2010-11-01

    Solutions of polymers are widely used in the pharmaceutical industry as tablets coatings. These allow controlling the rate at which the drug is delivered, taste or appearance. The coating is performed by spraying and drying the tablets at moderate temperatures. The wetting of the coating solution on the pill's surface depends on the droplet Webber and Re numbers, angle of impact and on the rheological properties of the droplet. We present a model for the evaporation of multicomponent solutions droplets in a hot air environment with temperatures substantially lower than the boiling temperature of the solvent. As the liquid vaporizes from the surface the fluid in the drop increases in concentration, until reaching its saturation point. After saturation, precipitation occurs uniformly within the drop. As the surface regresses, a compacting front formed by the precipitate at its maximum packing density advances into the drop, while the solute continues precipitating uniformly. This porous shell grows fast due to the double effect of surface regression and precipitation. The evaporation rate is determined by the rates at which heat is transported to the droplet surface and at which liquid vapor diffuses away from it. When the drop is fully compacted, the evaporation is drastically reduced.

  14. Supersonic Particle Deposition (Cold Spray)

    DTIC Science & Technology

    2006-01-26

    SUPPLEMENTARY NOTES 26th Replacement of Hard Chrome and Cadmium Plating Program Review Meeting, January 24-26, 2006, San Diego, CA. Sponsored by SERDP...Spray Cu-W ( clad powder) 197 89-90 HRB Cold Spray Ta 256 21 HRC Cold Spray Ni 403 40-41 HRC Hardness of Various Cold Spray Coatings -Cold Spray

  15. Flooding criterion for evaporative cooling on horizontal semi infinite solids

    SciTech Connect

    Lederer, M.A.; Marzo, M. di; Tartarini, P.

    1996-12-31

    The evaporative cooling of a sparse spray impacting on a hot solid is investigated to determine the limiting condition associated with the liquid flooding of the solid surface. The flooding condition is identified when the evaporation rate is insufficient to remove the amount of water being deposited on the surface. The flooding criteria is derived as a function of the initial single droplet volume prior to deposition, the Evaporation-Recovery Cycle (ERC) and the area of influence, which describes the region of the solid surface associated with a single droplet cooling effect. These last two quantities, the ERC and the area of influence, are evaluated by integrating previously obtained theoretical and experimental information with selected experimental data obtained in this study. The flooding criteria, while semi-empirical in its derivation, can be generalized to all non-porous solids under a variety of conditions. The spray is sparse and the water droplets are considered of uniform size. Extension to a spray with non-uniform droplet distribution is not considered here.

  16. The Determination of Several Spray Characteristics of a High-Speed Oil Engine Injection System with an Oscilloscope

    NASA Technical Reports Server (NTRS)

    Hicks, Chester W; Moore, Charles S

    1928-01-01

    An investigation was conducted to determine the injection lag, duration of injection, and spray start and cut-off characteristics of a fuel injection system operated on an engine and injecting fuel into the atmosphere.

  17. Bear Spray Safety Program

    USGS Publications Warehouse

    Blome, C.D.; Kuzniar, R.L.

    2009-01-01

    A bear spray safety program for the U.S. Geological Survey (USGS) was officially initiated by the Firearms Safety Committee to address accident prevention and to promote personnel training in bear spray and its transportation, storage, and use for defense against wild animals. Used as part of a system including firearms, or used alone for those who choose not to carry a firearm, bear spray is recognized as an effective tool that can prevent injury in a wild animal attack.

  18. Uranium solubility studies during waste evaporation

    SciTech Connect

    Karraker, D.G.

    1993-08-16

    The liquid waste streams from chemical processing of reactor-irradiated targets and fuel are neutralized with excess NaOH and discharged to mild steel waste tanks for interim storage. To reduce the number of tanks required, and thus the cost of waste storage, the supernate is evaporated to about 70% solids, discharged while hot into clean waste tanks. As the solution cools, solids crystallize from the saturated solution and form a solid layer on the bottom of the tank. The supernate is re-evaporated to concentrate the volume further. Evaporation and crystallization are continued until, for tank 41, the tank is almost filled with crystallized salts. In the DWPF processing scheme, these salts will be redissolved in water and {sup 137}Cs precipitated with sodium tetraphenylborate in the in-tank precipitation facility. The decontaminated supernate is now mixed with cement and stored as a solid monolith; the precipitated Cs and the base-insoluble solids are encapsulated in glass for permanent storage. Questions have been raised about the nuclear safety of these operations, particularly for tank 41, where the waste source was waste from the H-Area fuel processing. One scenario for a potential nuclear accident considers that the salts in tank 41 would dissolve in water, but the enriched uranium solids would not dissolve. The uranium is hypothesized to settle to the bottom of the tank and become concentrated enough to reach a critical mass. A second scenario, promulgated by West Valley, is that uranium would precipitate in the evaporator and form a critical mass in the evaporator. To shed some light on the probable behavior of U in the waste system, the solubility of U in synthetic waste was studied. The results are reported here.

  19. Quantitative characterization of diesel sprays using digital imaging techniques

    NASA Astrophysics Data System (ADS)

    Shao, J.; Yan, Y.; Greeves, G.; Smith, S.

    2003-07-01

    This paper presents the application of digital imaging and image processing techniques for the quantitative characterization of diesel sprays. An optically accessible, constant volume chamber was configured to allow direct photographic imaging of diesel sprays, which were generated from a six-hole nozzle in a non-evaporating and pressurized environment. A high-resolution CCD camera and a flash light source were used to capture the images of the sprays. Dedicated image processing software has been developed to quantify a set of macroscopic, characteristic parameters of the sprays including tip penetration, near-and far-field angles. The spray parameters produced using this software are compared with those obtained using manual methods. The results obtained under typical spray conditions demonstrate that the software is capable of producing more accurate, consistent and efficient results than the manual methods. An application of the imaging processing software to the characterization of diesel sprays for a valve covered orifice nozzle is also presented and discussed.

  20. Evaporatively driven morphological instability

    NASA Astrophysics Data System (ADS)

    Style, Robert W.; Wettlaufer, J. S.

    2007-07-01

    Simple observations of evaporating solutions reveal a complex hierarchy of spatiotemporal instabilities. We analyze one such instability suggested by the qualitative observations of Du and Stone and find that it is driven by a variant of the classical morphological instability in alloy solidification. In the latter case a moving solid-liquid interface is accompanied by a solutally enriched boundary layer that is thermodynamically metastable due to constitutional supercooling. Here, we consider the evaporation of an impure film adjacent to a solid composed of the nonvolatile species. In this case, constitutional supercooling within the film is created by evaporation at the solution-vapor interface and this drives the corrugation of the solid-solution interface across the thickness of the film. The principal points of this simple theoretical study are to suggest an instability mechanism that is likely operative across a broad range of technological and natural systems and to focus future quantitative experimental searches.

  1. Method of producing thermally sprayed metallic coating

    DOEpatents

    Byrnes, Larry Edward; Kramer, Martin Stephen; Neiser, Richard A.

    2003-08-26

    The cylinder walls of light metal engine blocks are thermally spray coated with a ferrous-based coating using an HVOF device. A ferrous-based wire is fed to the HVOF device to locate a tip end of the wire in a high temperature zone of the device. Jet flows of oxygen and gaseous fuel are fed to the high temperature zone and are combusted to generate heat to melt the tip end. The oxygen is oversupplied in relation to the gaseous fuel. The excess oxygen reacts with and burns a fraction of the ferrous-based feed wire in an exothermic reaction to generate substantial supplemental heat to the HVOF device. The molten/combusted metal is sprayed by the device onto the walls of the cylinder by the jet flow of gases.

  2. Directional motion of evaporating droplets on gradient surfaces

    NASA Astrophysics Data System (ADS)

    Yao, Shuhuai; Xu, Li; Li, Zhigang

    2012-11-01

    Droplet evaporation on surfaces has various applications in drying problems such as ink-jet printing, pesticide spraying, chemical or biological detection, and DNA microarray spotting technology. Controlling evaporating droplets via substrate morphology and/or wetting properties allows for efficient deposition of sample molecules in these applications. In this work, evaporation of sessile water droplets on surfaces with wettability gradients was studied. The wettability gradient was generated by fabricating non-uniformly distributed cylindrical micropillars on silicon surfaces. During the evaporation, it was found, along the wettability gradient, that the contact line on one side was strongly pinned, while the contact line on the other side depinned and gradually receded, making the center of mass of the droplet move either in or against the direction the wettability gradient, depending on the configuration of the micropillars. The theoretical criterion predicting the moving direction was derived based on the excess free energy and the energy barrier during the evaporation. The theoretical predications agreed well with the experimental observations. The results provide a parametric design basis to control the contact line dynamics and directional transport of evaporating droplets. This work was supported by the Research Grants Council of Hong Kong under General Research Fund (Grant No. 621110).

  3. Program Models A Laser Beam Focused In An Aerosol Spray

    NASA Technical Reports Server (NTRS)

    Barton, J. P.

    1996-01-01

    Monte Carlo analysis performed on packets of light. Program for Analysis of Laser Beam Focused Within Aerosol Spray (FLSPRY) developed for theoretical analysis of propagation of laser pulse optically focused within aerosol spray. Applied for example, to analyze laser ignition arrangement in which focused laser pulse used to ignite liquid aerosol fuel spray. Scattering and absorption of laser light by individual aerosol droplets evaluated by use of electromagnetic Lorenz-Mie theory. Written in FORTRAN 77 for both UNIX-based computers and DEC VAX-series computers. VAX version of program (LEW-16051). UNIX version (LEW-16065).

  4. Investigation of particulate formation during diesel spray combustion: CARS for diesel spray combustion. [Coherent Anti-Stokes Raman Spectroscopy (CARS)

    SciTech Connect

    Boedeker, L.R.

    1991-09-01

    An experimental and analytical research program has been carried out whose objectives were to investigate strategies for using coherent anti-Stokes Raman spectroscopy (CARS) laser diagnostic techniques for detecting the vapor phase of liquid fuel sprays, determining fuel-air ratio and the degree of fuel pyrolysis. The extent to which CARS can provide valid vapor phase fuel measurements in the presence of droplets within the CARS resolution volume will determine its ultimate utility for engine measurements. Hence, the priority in this program was maintained toward investigating possible adverse droplet effects on CARS measurements. Droplets in a relevant size range (25-- 50 microns) were generated for convenience with a spray nozzle. Tests were conducted in a spray chamber at 1 atm pressure under near- saturated fuel vapor pressure conditions, with and without a toluene fuel spray turned on. For reasons of safety an inert gas, CO{sub 2}, was used to simulate O{sub 2}. It was necessary to provide reliable vapor phase CARS reference spectra for these spray studies in order to insure that spurious liquid effects were not present and known vapor phase spectra were attained. To provide these reference spectra the capability was developed of isolating, in a CARS test cell, the vapor phase of fuels that are normally liquids at room temperature and pressure. The cell could be evacuated with a vacuum pump and heated uniformly up to about 100 C. Hence, a capability was established to measure nonresonant and resonant vapor phase CARS features of normally liquid fuels over wide pressure and temperature range, needed for evaluating CARS fuel-air analysis strategies.

  5. Fabrication of copper-based anodes via atmosphoric plasma spraying techniques

    DOEpatents

    Lu, Chun [Monroeville, PA

    2012-04-24

    A fuel electrode anode (18) for a solid oxide fuel cell is made by presenting a solid oxide fuel cell having an electrolyte surface (15), mixing copper powder with solid oxide electrolyte in a mixing step (24, 44) to provide a spray feedstock (30,50) which is fed into a plasma jet (32, 52) of a plasma torch to melt the spray feed stock and propel it onto an electrolyte surface (34, 54) where the spray feed stock flattens into lamellae layer upon solidification, where the layer (38, 59) is an anode coating with greater than 35 vol. % based on solids volume.

  6. Cold spray nozzle design

    DOEpatents

    Haynes, Jeffrey D.; Sanders, Stuart A.

    2009-06-09

    A nozzle for use in a cold spray technique is described. The nozzle has a passageway for spraying a powder material, the passageway having a converging section and a diverging section, and at least the diverging section being formed from polybenzimidazole. In one embodiment of the nozzle, the converging section is also formed from polybenzimidazole.

  7. Geochemistry: Evaporating planetesimals

    NASA Astrophysics Data System (ADS)

    Young, Edward D.

    2017-09-01

    Two studies show that evaporation of molten rock was intrinsic to the formation of Earth and other rocky bodies in the Solar System, suggesting that violent collisions played a key part in the formation process. See Letters p.507 & p.511

  8. Evaporation into Couette Flow

    DTIC Science & Technology

    2008-01-01

    v Yi Statistical analysis dependent variable Greek Symbols 13 Contact angle of sessile drop a Concentration thickness A Evaporated vapor penetration...31 5 FIGURES 1. Configuration of Three Sessile Drops ............................................. 10 2. Sketch of...Droplet Geometry ............................................................. 11 3. Shape Factor as a Function of Contact Angle

  9. Laser Evaporation Studies.

    DTIC Science & Technology

    1987-10-01

    concentrated aqua regia and hydrochloric energy ions. The minimum pulsed evaporation rate which acid, respectively. The metallic films capped by cw laser...Force Office of Scientific Research or the U.S. Government. 17 COSATI CODES 18 SUBJECT TERMS (Continue on reverse if necessarl and identif by block

  10. Environmentally compatible spray cement

    SciTech Connect

    Loeschnig, P.

    1995-12-31

    Within the framework of a European research project, Heidelberger Zement developed a quickly setting and hardening binder for shotcrete, called Chronolith S, which avoids the application of setting accelerators. Density and strength of the shotcrete produced with this spray cement correspond to those of an unaccelerated shotcrete. An increased hazard for the heading team and for the environment, which may occur when applying setting accelerators, can be excluded here. Owing to the special setting properties of a spray cement, the process engineering for its manufacturing is of great importance. The treatment of a spray cement as a dry concrete with kiln-dried aggregates is possible without any problems. The use of a naturally damp pre-batched mixture is possible with Chronolith S but requires special process engineering; spray cement and damp aggregate are mixed with one another immediately before entering the spraying machinery.

  11. Potential for natural evaporation as a reliable renewable energy resource.

    PubMed

    Cavusoglu, Ahmet-Hamdi; Chen, Xi; Gentine, Pierre; Sahin, Ozgur

    2017-09-26

    About 50% of the solar energy absorbed at the Earth's surface drives evaporation, fueling the water cycle that affects various renewable energy resources, such as wind and hydropower. Recent advances demonstrate our nascent ability to convert evaporation energy into work, yet there is little understanding about the potential of this resource. Here we study the energy available from natural evaporation to predict the potential of this ubiquitous resource. We find that natural evaporation from open water surfaces could provide power densities comparable to current wind and solar technologies while cutting evaporative water losses by nearly half. We estimate up to 325 GW of power is potentially available in the United States. Strikingly, water's large heat capacity is sufficient to control power output by storing excess energy when demand is low, thus reducing intermittency and improving reliability. Our findings motivate the improvement of materials and devices that convert energy from evaporation.The evaporation of water represents an alternative source of renewable energy. Building on previous models of evaporation, Cavusoglu et al. show that the power available from this natural resource is comparable to wind and solar power, yet it does not suffer as much from varying weather conditions.

  12. Evaluating two different evaporative cooling management systems for dairy cows in a hot, dry climate.

    PubMed

    Ryan, D P; Boland, M P; Kopel, E; Armstrong, D; Munyakazi, L; Godke, R A; Ingraham, R H

    1992-04-01

    Milk production, rectal temperature, live weight gain, reproductive performance, and weather data were obtained on 150 Holstein cows managed under two cooling systems on a large dairy farm in Saudi Arabia during the summer months. Cows were paired at the onset of the trial according to days postpartum, lactation number, and current milk production. Females were then allocated either to a system that forced air, precooled by evaporative cooling, over the cows or to a system that alternately showered a fine mist onto the surface of the cows and then forced air at ambient temperature over them. The cows receiving evaporative cooling and those with spray and fan cooling were on sand and on slatted concrete floor, respectively, during the periods of cooling. The onset of estrus was observed during the night when the cows preferred the unshaded corral. For the 120-d trial period, 84% (62 of 75) of the cows receiving evaporative cooling and 60% (44 of 75) of the cows receiving spray and fan cooling became pregnant. In the evaporative cooling system, the pregnancy rate per insemination was 35.2% (179 inseminations) versus 23.2% (194 inseminations) for spray and fan cooling. The mean postpartum interval to pregnancy was 117.6 d for the evaporative cooling cows and 146.7 d for spray and fan cooling cows. The evaporative cooling system, with its open shades and sand bedding, enhanced reproductive performance and milk production compared with that of cows cooled with a spray and fan system with slatted flooring in this hot climate.

  13. Spray measurement technology: a review

    NASA Astrophysics Data System (ADS)

    Fansler, Todd D.; Parrish, Scott E.

    2015-01-01

    Sprays are among the most intellectually challenging and practically important topics in fluid mechanics. This paper reviews needs, milestones, challenges, and a broad array of techniques for spray measurement. In addition, tabular summaries provide cross-referenced entry points to the vast literature by organizing over 300 citations according to key spray phenomena, physical parameters and measurement techniques for each of the principal spray regions (nozzle internal flow, near-field spray-formation region, far-field developed spray, and spray-wall interaction). The article closes with perspectives on some current issues in spray research, including the cost and complexity of apparatus for spray physics and spray engineering, the need for simultaneous diagnostic measurements under application-relevant conditions, and the effective comparison of spray measurements and numerical simulations.

  14. Measuring forest floor evaporation from interception in prescribed burned forests in Southern Italy.

    NASA Astrophysics Data System (ADS)

    Giuditta, Elisabetta; Coenders-Gerrits, Miriam; Bogaard, Thom; Wenninger, Jochen; Greco, Roberto; Ialongo, Gianluca; Esposito, Assunta; Rutigliano, Flora Angela

    2016-04-01

    Wildfires are one of the major environmental issue in the Mediterranean area. Prescribed burning (PB) is increasingly used in Europe as a practice to reduce fire risk, through dead fine fuel reduction. Several studies have focused on fire effects on vegetation and soil microbial community, but very few on ecosystem processes involved in water cycle. This study aims to estimate interception by the litter and fermentation layer and the successive evaporation flux in laboratory conditions, using a water balance and 2H and 18O isotopes mass balance calculation, in order to assess PB effects on the hydrology and ecosystem in pine plantations. PB was carried out in spring 2014 in three pine plantations of Southern Italy, dominated by Pinus halepensis (Cilento, Vallo di Diano e Alburni National Park, CVDANP), P. pinaster (Vesuvio National Park, VNP) and P. pinea (Castel Volturno Nature Reserve, CVNR). A dataset concerning the effects of PB on vegetation structure, floristic composition, microbial biomass and activity in the fermentation layer and 5-cm of soil beneath is available for the same stands. In each plantation, two cores of litter and fermentation layer were sampled in a burned area and in a near unburned area (control), respectively, with a collector to extract an "undisturbed" core. Then, each core was transferred in a lysimeter installed in the Water Lab of Delft University of Technology. In total, three lysimeters were set up and each experiment was carried out in duplicate. The laboratory had constant temperature, and both temperature and relative humidity were recorded every 15 minutes. To simulate rainfall, ~1 litre of tap water was sprinkled uniformly on the lysimeter with a plant spray (equivalent to 32 mm of rain). The precipitation was sprinkled every 3 days for a period of two months. Soil moisture and temperature were measured during the experiment every 15 minutes in the top and bottom of the litter and fermentation layer. Interception water was

  15. Spray Rolling Aluminum Strip

    SciTech Connect

    Lavernia, E.J.; Delplanque, J-P; McHugh, K.M.

    2006-05-10

    Spray forming is a competitive low-cost alternative to ingot metallurgy for manufacturing ferrous and non-ferrous alloy shapes. It produces materials with a reduced number of processing steps, while maintaining materials properties, with the possibility of near-net-shape manufacturing. However, there are several hurdles to large-scale commercial adoption of spray forming: 1) ensuring strip is consistently flat, 2) eliminating porosity, particularly at the deposit/substrate interface, and 3) improving material yield. Through this program, a new strip/sheet casting process, termed spray rolling, has been developed, which is an innovative manufacturing technique to produce aluminum net-shape products. Spray rolling combines the benefits of twin-roll casting and conventional spray forming, showing a promising potential to overcome the above hurdles associated with spray forming. Spray rolling requires less energy and generates less scrap than conventional processes and, consequently, enables the development of materials with lower environmental impacts in both processing and final products. Spray Rolling was developed as a collaborative project between the University of California-Davis, the Colorado School of Mines, the Idaho National Engineering and Environmental Laboratory, and an industry team. The following objectives of this project were achieved: (1) Demonstration of the feasibility of the spray rolling process at the bench-scale level and evaluation of the materials properties of spray rolled aluminum strip alloys; and (2) Demonstration of 2X scalability of the process and documentation of technical hurdles to further scale up and initiate technology transfer to industry for eventual commercialization of the process.

  16. Development and Application of HVOF Sprayed Spinel Protective Coating for SOFC Interconnects

    NASA Astrophysics Data System (ADS)

    Thomann, O.; Pihlatie, M.; Rautanen, M.; Himanen, O.; Lagerbom, J.; Mäkinen, M.; Varis, T.; Suhonen, T.; Kiviaho, J.

    2013-06-01

    Protective coatings are needed for metallic interconnects used in solid oxide fuel cell (SOFC) stacks to prevent excessive high-temperature oxidation and evaporation of chromium species. These phenomena affect the lifetime of the stacks by increasing the area-specific resistance (ASR) and poisoning of the cathode. Protective MnCo2O4 and MnCo1.8Fe0.2O4 coatings were applied on ferritic steel interconnect material (Crofer 22 APU) by high velocity oxy fuel spraying. The substrate-coating systems were tested in long-term exposure tests to investigate their high-temperature oxidation behavior. Additionally, the ASRs were measured at 700 °C for 1000 h. Finally, a real coated interconnect was used in a SOFC single-cell stack for 6000 h. Post-mortem analysis was carried out with scanning electron microscopy. The deposited coatings reduced significantly the oxidation of the metal, exhibited low and stable ASR and reduced effectively the migration of chromium.

  17. Combustor with fuel preparation chambers

    NASA Technical Reports Server (NTRS)

    Zelina, Joseph (Inventor); Myers, Geoffrey D. (Inventor); Srinivasan, Ram (Inventor); Reynolds, Robert S. (Inventor)

    2001-01-01

    An annular combustor having fuel preparation chambers mounted in the dome of the combustor. The fuel preparation chamber comprises an annular wall extending axially from an inlet to an exit that defines a mixing chamber. Mounted to the inlet are an air swirler and a fuel atomizer. The air swirler provides swirled air to the mixing chamber while the atomizer provides a fuel spray. On the downstream side of the exit, the fuel preparation chamber has an inwardly extending conical wall that compresses the swirling mixture of fuel and air exiting the mixing chamber.

  18. An overview of spray drift reduction testing of spray nozzles

    USDA-ARS?s Scientific Manuscript database

    The importance of the development and testing of drift reduction technologies (DRTs) is increasing. Common spray drift reduction technologies include spray nozzles and spray adjuvants. Following draft procedures developed for a DRT program, three spray nozzles were tested under high air speed cond...

  19. Mesoporous-silica films, fibers, and powders by evaporation

    DOEpatents

    Bruinsma, Paul J.; Baskaran, Suresh; Bontha, Jagannadha R.; Liu, Jun

    2008-05-06

    This invention pertains to surfactant-templated nanometer-scale porosity of a silica precursor solution and forming a mesoporous material by first forming the silica precursor solution into a preform having a high surface area to volume ratio, then rapid drying or evaporating a solvent from the silica precursor solution. The mesoporous material may be in any geometric form, but is preferably in the form of a film, fiber, powder or combinations thereof. The rapid drying or evaporation of solvent from the solution is accomplished by layer thinning, for example spin casting, liquid drawing, and liquid spraying respectively. Production of a film is by layer thinning, wherein a layer of the silica precursor solution is formed on a surface followed by removal of an amount of the silica precursor solution and leaving a geometrically thinner layer of the silica precursor solution from which the solvent quickly escapes via evaporation. Layer thinning may be by any method including but not limited to squeegeeing and/or spin casting. In powder formation by spray drying, the same conditions of fast drying exists as in spin-casting (as well as in fiber spinning) because of the high surface-area to volume ratio of the product. When a powder is produced by liquid spraying, the particles or micro-bubbles within the powder are hollow spheres with walls composed of mesoporous silica. Mesoporous fiber formation starts with a similar silica precursor solution but with an added pre-polymer making a pituitous mixture that is drawn into a thin strand from which solvent is evaporated leaving the mesoporous fiber(s).

  20. Mesoporous-silica films, fibers, and powders by evaporation

    DOEpatents

    Bruinsma, Paul J.; Baskaran, Suresh; Bontha, Jagannadha R.; Liu, Jun

    1999-01-01

    This invention pertains to surfactant-templated nanometer-scale porosity of a silica precursor solution and forming a mesoporous material by first forming the silica precursor solution into a preform having a high surface area to volume ratio, then rapid drying or evaporating a solvent from the silica precursor solution. The mesoporous material may be in any geometric form, but is preferably in the form of a film, fiber, powder or combinations thereof. The rapid drying or evaporation of solvent from the solution is accomplished by layer thinning, for example spin casting, liquid drawing, and liquid spraying respectively. Production of a film is by layer thinning, wherein a layer of the silica precursor solution is formed on a surface followed by removal of an amount of the silica precursor solution and leaving a geometrically thinner layer of the silica precursor solution from which the solvent quickly escapes via evaporation. Layer thinning may be by any method including but not limited to squeegeeing and/or spin casting. In powder formation by spray drying, the same conditions of fast drying exists as in spin-casting (as well as in fiber spinning) because of the high surface-area to volume ratio of the product. When a powder is produced by liquid spraying, the particles or micro-bubbles within the powder are hollow spheres with walls composed of mesoporous silica. Mesoporous fiber formation starts with a similar silica precursor solution but with an added pre-polymer making a pituitous mixture that is drawn into a thin strand from which solvent is evaporated leaving the mesoporous fiber(s).

  1. Mesoporous-silica films, fibers, and powders by evaporation

    DOEpatents

    Bruinsma, P.J.; Baskaran, S.; Bontha, J.R.; Liu, J.

    1999-07-13

    This invention pertains to surfactant-templated nanometer-scale porosity of a silica precursor solution and forming a mesoporous material by first forming the silica precursor solution into a preform having a high surface area to volume ratio, then rapid drying or evaporating a solvent from the silica precursor solution. The mesoporous material may be in any geometric form, but is preferably in the form of a film, fiber, powder or combinations thereof. The rapid drying or evaporation of solvent from the solution is accomplished by layer thinning, for example spin casting, liquid drawing, and liquid spraying respectively. Production of a film is by layer thinning, wherein a layer of the silica precursor solution is formed on a surface followed by removal of an amount of the silica precursor solution and leaving a geometrically thinner layer of the silica precursor solution from which the solvent quickly escapes via evaporation. Layer thinning may be by any method including but not limited to squeegeeing and/or spin casting. In powder formation by spray drying, the same conditions of fast drying exists as in spin-casting (as well as in fiber spinning) because of the high surface-area to volume ratio of the product. When a powder is produced by liquid spraying, the particles or micro-bubbles within the powder are hollow spheres with walls composed of mesoporous silica. Mesoporous fiber formation starts with a similar silica precursor solution but with an added pre-polymer making a pituitous mixture that is drawn into a thin strand from which solvent is evaporated leaving the mesoporous fiber(s). 24 figs.

  2. Evaporation of pure liquid sessile and spherical suspended drops: a review.

    PubMed

    Erbil, H Yildirim

    2012-01-15

    A sessile drop is an isolated drop which has been deposited on a solid substrate where the wetted area is limited by a contact line and characterized by contact angle, contact radius and drop height. Diffusion-controlled evaporation of a sessile drop in an ambient gas is an important topic of interest because it plays a crucial role in many scientific applications such as controlling the deposition of particles on solid surfaces, in ink-jet printing, spraying of pesticides, micro/nano material fabrication, thin film coatings, biochemical assays, drop wise cooling, deposition of DNA/RNA micro-arrays, and manufacture of novel optical and electronic materials in the last decades. This paper presents a review of the published articles for a period of approximately 120 years related to the evaporation of both sessile drops and nearly spherical droplets suspended from thin fibers. After presenting a brief history of the subject, we discuss the basic theory comprising evaporation of micrometer and millimeter sized spherical drops, self cooling on the drop surface and evaporation rate of sessile drops on solids. The effects of drop cooling, resultant lateral evaporative flux and Marangoni flows on evaporation rate are also discussed. This review also has some special topics such as drop evaporation on superhydrophobic surfaces, determination of the receding contact angle from drop evaporation, substrate thermal conductivity effect on drop evaporation and the rate evaporation of water in liquid marbles. Copyright © 2011 Elsevier B.V. All rights reserved.

  3. MOVES2014: Evaporative Emissions Report

    EPA Science Inventory

    Vehicle evaporative emissions are now modeled in EPA’s MOVES according to physical processes, permeation, tank vapor venting, liquid leaks, and refueling emissions. With this update, the following improvements are being incorporated into MOVES evaporative emissions methodology, a...

  4. MOVES2014: Evaporative Emissions Report

    EPA Science Inventory

    Vehicle evaporative emissions are now modeled in EPA’s MOVES according to physical processes, permeation, tank vapor venting, liquid leaks, and refueling emissions. With this update, the following improvements are being incorporated into MOVES evaporative emissions methodology, a...

  5. Plasma sprayed and electrospark deposited zirconium metal diffusion barrier coatings

    SciTech Connect

    Hollis, Kendall J; Pena, Maria I

    2010-01-01

    Zirconium metal coatings applied by plasma spraying and electrospark deposition (ESD) have been investigated for use as diffusion barrier coatings on low enrichment uranium fuel for research nuclear reactors. The coatings have been applied to both stainless steel as a surrogate and to simulated nuclear fuel uranium-molybdenum alloy substrates. Deposition parameter development accompanied by coating characterization has been performed. The structure of the plasma sprayed coating was shown to vary with transferred arc current during deposition. The structure of ESD coatings was shown to vary with the capacitance of the deposition equipment.

  6. Guest Editorial Particle Sizing And Spray Analysis

    NASA Astrophysics Data System (ADS)

    Chigier, Norman; Stewart, Gerald

    1984-10-01

    The measurement of particle size and velocity in particle laden flows is a subject of interest in a variety of industrial applications. In combustion systems for electricity generation, industrial processes and heating, and transportation, where liquid and solid fuels are injected into air streams for burning in furnaces, boilers, and gas turbine and diesel engines, the initial size and velocity distributions of particles are determining factors in the overall combustion efficiency and the emission of pollutants and particulates. In the design of injectors and burners for the atomization of liquid fuels, a great deal of attention is being focused on developing instrumentation for the accurate measurement of size and velocity distributions in sprays as a function of space and time. Most recent advances in optical engineering techniques using lasers for particle measurement have focused on detailed spray characterization, where there is a major concern with spherical liquid droplets within the size range of 1 to 500 μm in diameter, with droplet velocities within the range of 1 to 100 m/s, and the requirement for making in situ measurements of moving particles by nonintrusive optical probes. The instruments being developed for spray analysis have much wider applications. These include measurement in particle laden flows encountered in a variety of industrial processes with solid particles in gas and liquid streams and liquid particles in gas streams. Sprays used in agriculture, drying, food processing, coating of materials, chemical processing, clean rooms, pharmaceuticals, plasma spraying, and icing wind tunnels are examples of systems for which information is being sought on particle and fluid dynamic interactions in which there is heat, mass, and momentum transfer in turbulent reacting flows.

  7. Thermal Arc Spray Overview

    NASA Astrophysics Data System (ADS)

    Hafiz Abd Malek, Muhamad; Hayati Saad, Nor; Kiyai Abas, Sunhaji; Mohd Shah, Noriyati

    2013-06-01

    Usage of protective coating for corrosion protection was on highly demand during the past decade; and thermal spray coating played a major part during that time. In recent years, the thermal arc spray coating becomes a popular coating. Many big players in oil and gas such as PETRONAS, EXXON MOBIL and SHELL in Malaysia tend to use the coating on steel structure as a corrosion protection. Further developments in coating processes, the devices, and raw materials have led to expansion of functional coatings and applications scope from conventional coating to specialized industries. It is widely used because of its ability to withstand high process temperature, offer advantages in efficiency, lower cost and acts as a corrosion protection. Previous research also indicated that the thermal arc spray offers better coating properties compared to other methods of spray. This paper reviews some critical area of thermal spray coating by discussing the process/parameter of thermal arc spray technology and quality control of coating. Coating performance against corrosion, wear and special characteristic of coating are also described. The field application of arc spray technology are demonstrated and reviewed.

  8. Electrostatic Fuel Atomization and Spray Dispersal Demonstration

    DTIC Science & Technology

    1990-07-01

    2.4 bar absolute influence the droplet formation process. A "best fit" continuous Rosin - Rammler distri- Increasing background pressure serves to bution...empirical pressure. This is an intrinsic feature of charge Rosin - Rammler curve the comparison is use- injection atomizers that serves both to sharpen ful...interval between 35 and 42 microns. The atomizer operating in a five atmosphere back- crudely approximate Rosin - Rammler distri- ground pressure, the

  9. Application of thermal spray coatings to aerospace structures

    SciTech Connect

    Novak, H.L.

    1994-12-31

    Reusable launch vehicles located by the ocean are subject to harsh seacoast environments before launch and immersion after splashdown at sea and tow back to the refurbishment facility. The use of various thermal spray processes for depositing corrosion and erosion protective materials to the alloy substrates has potential for enhancing the corrosion/erosion resistance and useful life of those expensive large reusable aerospace structures. Thermal spray processes such as high velocity oxygen fuel (HVOF), plasma, arc spray and conventional oxygen fuel spray and the IVD process (pure aluminum only) have been used to coat test panels and scrap flight hardware with various applied materials. Pure aluminum, aluminum/aluminum oxide matrix (DURALCAN), and pure zinc have been applied over 2219-T87 aluminum alloy, 4340 steel alloy substrates. Salt spray testing has been conducted in accordance with ASTM B-117 as well as beach exposure tests at Kennedy Space Center, Florida. Adhesion tests have been performed for all materials applied to the various substrates as well as monitoring of substrate temperatures during the spray process. The pure aluminum, zinc, and aluminum/aluminum oxide matrix material afforded excellent corrosion protection in both beach exposure and salt spray environments. in conclusion, tests and actual applications have shown that the various thermal spray processes and coating materials have significant potential for enhancing corrosion/erosion resistance and extending the useful service life of expensive aerospace structures exposed to marine environments. The ability to effectively repair damaged IVD aluminum coated substrates using arc sprayed material adds flexibility to the maintenance process. Due to the excellent adhesion and corrosion protection of the substrate, tests are underway to determine if chromate conversion coating can be eliminated prior to primer/topcoat application.

  10. Atomization of broad specification aircraft fuels

    NASA Technical Reports Server (NTRS)

    Skifstad, J. G.; Lefebvre, A. H.

    1980-01-01

    The atomization properties of liquid fuels for the potential use in aircraft gas turbine engines are discussed. The significance of these properties are addressed with respect to the ignition and subsequent combustion behavior of the fuel spray/air mixture. It is shown that the fuel properties which affect the atomization behavior (viscosity, surface tension, and density) are less favorable for the broad specification fuels as compared to with those for conventional fuels.

  11. Adjuvant Effects on Evaporation Rates and Wetted Area of Droplets on Waxy Leaves

    USDA-ARS?s Scientific Manuscript database

    The use of an appropriate adjuvant for pesticide applications is a critical process to improve spray deposit characteristics on waxy leaves and to reduce off-target losses. After deposition and evaporation, residue patterns of 500 µm sessile droplets that incorporated four classes of adjuvants on fi...

  12. Synthesis of functional oxides through plasma spraying

    NASA Astrophysics Data System (ADS)

    Guo, Xianzhong

    Thermal spray coatings have become an important part of modern industry, offering customized surface properties for a variety of industrial applications, e.g. thermal barrier coatings, wear resistant coatings, erosion resistant coatings and functional coatings. Although the usage of thermal spray coatings has increased dramatically, the scientific research of these coatings has lagged behind. Good understanding of thermal spray processes can provide the optimistic combination of operation parameters to obtain high quality of coating, improve service life of the product, and lower cost of the system. The research presented in this dissertation focuses on the synthesis of functional oxide coatings through plasma spraying techniques. The materials studied in this research are: yttrium aluminum garnet (YAG) which can be the thermal barrier coating and environmental barrier coating; doped YAG as phosphor; yttrium iron garnet (YIG) applied in telecommunication and data storage; aluminum substituted YIG for biomedical applications; and zirconium substituted yttrium titanate pyrochlore in developing solid oxide fuel cells (SOFCs). The synthesis processes, phase formation, microstructure, and physical properties of above materials have been investigated in a comprehensive and integrated way. The precursor powders or solutions were prepared via different chemical routes. The experiments suggest that formation of phase-pure oxides occurs through different phase evolution pathways and depending on the reaction conditions. Chemically derived precursors and/or powders were used as feedstock in plasma spray to form functional oxide coatings. Due to its rapid heating and cooling features, plasma spraying techniques provide a novel opportunity for functional oxides to transfer from amorphous into crystallized structure at a relatively low temperature in a single step. The properties of assprayed and post-heated coatings strongly depend on their microstructure and phase content.

  13. Analytical and numerical studies on a single-droplet evaporation and combustion under forced convection

    NASA Astrophysics Data System (ADS)

    Zhou, L. X.; Li, K.

    2015-08-01

    Existing droplet evaporation/combustion models in computational fluid dynamics (CFD) simulation of spray combustion are based on simplified 1-D models. Both these models and recently developed 3-D models of single-droplet combustion do not give the conditions for the different existing droplet combustion modes. In this paper, droplet evaporation and combustion are studied both analytically and numerically. In the analytical solution, a 2-D axisymmetric flow surrounding an evaporating and combusting droplet was considered. The governing equations were solved using an integral method, similar to the Karman-Pohlhausen method for solving boundary-layer flows with pressure gradient. The results give a local evaporation rate and flame radius in agreement with experimental results. In numerical simulation, 3-D combusting gas flows surrounding an ethanol droplet were studied. The prediction results show three modes of droplet combustion under different relative velocities, explaining the change in the evaporation constant with an increase in relative velocity observed in experiments. This implies that different droplet combustion models should be developed in simulating spray combustion. The predicted local evaporation rate and flame radius by numerical simulation are in agreement with the analytical solution in the range of azimuthal angles . The numerical results indicate that the drag force of an evaporating and combusting droplet is much smaller than that of a cold solid particle, and thus the currently used drag models should be modified.

  14. The study on injection parameters of selected alternative fuels used in diesel engines

    NASA Astrophysics Data System (ADS)

    Balawender, K.; Kuszewski, H.; Lejda, K.; Lew, K.

    2016-09-01

    The paper presents selected results concerning fuel charging and spraying process for selected alternative fuels, including regular diesel fuel, rape oil, FAME, blends of these fuels in various proportions, and blends of rape oil with diesel fuel. Examination of the process included the fuel charge measurements. To this end, a set-up for examination of Common Rail-type injection systems was used constructed on the basis of Bosch EPS-815 test bench, from which the high-pressure pump drive system was adopted. For tests concerning the spraying process, a visualisation chamber with constant volume was utilised. The fuel spray development was registered with the use of VisioScope (AVL).

  15. Falling film evaporator

    DOEpatents

    Bruns, Lester E.

    1976-01-01

    A falling film evaporator including a vertically oriented pipe heated exteriorly by a steam jacket and interiorly by a finned steam tube, all heating surfaces of the pipe and steam tube being formed of a material wet by water such as stainless steel, and packing within the pipe consisting of Raschig rings formed of a material that is not wet by water such as polyvinylidene fluoride.

  16. Vertical counterflow evaporative cooler

    DOEpatents

    Bourne, Richard C.; Lee, Brian Eric; Callaway, Duncan

    2005-01-25

    An evaporative heat exchanger having parallel plates that define alternating dry and wet passages. A water reservoir is located below the plates and is connected to a water distribution system. Water from the water distribution system flows through the wet passages and wets the surfaces of the plates that form the wet passages. Air flows through the dry passages, mixes with air below the plates, and flows into the wet passages before exiting through the top of the wet passages.

  17. A spray-suppression model for turbulent combustion

    SciTech Connect

    DESJARDIN,PAUL E.; TIESZEN,SHELDON R.; GRITZO,LOUIS A.

    2000-02-14

    A spray-suppression model that captures the effects of liquid suppressant on a turbulent combusting flow is developed and applied to a turbulent diffusion flame with water spray suppression. The spray submodel is based on a stochastic separated flow approach that accounts for the transport and evaporation of liquid droplets. Flame extinguishment is accounted for by using a perfectly stirred reactor (PSR) submodel of turbulent combustion. PSR pre-calculations of flame extinction times are determined using CHEMKIN and are compared to local turbulent time scales of the flow to determine if local flame extinguishment has occurred. The PSR flame extinguishment and spray submodels are incorporated into Sandia's flow fire simulation code, VULCAN, and cases are run for the water spray suppression studies of McCaffrey for turbulent hydrogen-air jet diffusion flames. Predictions of flame temperature decrease and suppression efficiency are compared to experimental data as a function of water mass loading using three assumed values of drop sizes. The results show that the suppression efficiency is highly dependent on the initial droplet size for a given mass loading. A predicted optimal suppression efficiency was observed for the smallest class of droplets while the larger drops show increasing suppression efficiency with increasing mass loading for the range of mass loadings considered. Qualitative agreement to the experiment of suppression efficiency is encouraging, however quantitative agreement is limited due to the uncertainties in the boundary conditions of the experimental data for the water spray.

  18. Water Membrane Evaporator

    NASA Technical Reports Server (NTRS)

    Ungar, Eugene K.; Almlie, Jay C.

    2010-01-01

    A water membrane evaporator (WME) has been conceived and tested as an alternative to the contamination-sensitive and corrosion-prone evaporators currently used for dissipating heat from space vehicles. The WME consists mainly of the following components: An outer stainless-steel screen that provides structural support for the components mentioned next; Inside and in contact with the stainless-steel screen, a hydrophobic membrane that is permeable to water vapor; Inside and in contact with the hydrophobic membrane, a hydrophilic membrane that transports the liquid feedwater to the inner surface of the hydrophobic membrane; Inside and in contact with the hydrophilic membrane, an annular array of tubes through which flows the spacecraft coolant carrying the heat to be dissipated; and An inner exclusion tube that limits the volume of feedwater in the WME. In operation, a pressurized feedwater reservoir is connected to the volume between the exclusion tube and the coolant tubes. Feedwater fills the volume, saturates the hydrophilic membrane, and is retained by the hydrophobic membrane. The outside of the WME is exposed to space vacuum. Heat from the spacecraft coolant is conducted through the tube walls and the water-saturated hydrophilic membrane to the liquid/vapor interface at the hydrophobic membrane, causing water to evaporate to space. Makeup water flows into the hydrophilic membrane through gaps between the coolant tubes.

  19. Evaporation of Extrasolar Planets

    NASA Astrophysics Data System (ADS)

    Lecavelier, Alain

    2011-09-01

    Among the five hundreds extrasolar planets known, almost 30% orbit closer than 0.1 AU from their parent star. We will review the observations and the corresponding models of the evaporation of these "Hot-exoplanets". The observations started with the discovery made with HST that the planet orbiting HD209458 has an extended atmosphere of escaping hydrogen. Subsequent observations obtained with STIS and ACS and most recently with COS confirm the escape of the gas. And, even more, atomic oxygen, ionized carbon and silicon have been shown to be present at very high altitude in the upper atmosphere. Observations of other targets like HD189733b and Wasp-12 show that evaporation is a general phenomenon which could contribute to the evolution of planets orbiting close to their parent stars. To interpret these observations, we developed models to quantify the escape rate from the measured occultation depths. Numerous models have also been published to investigate mechanisms which can lead to the estimated escape rate. In general, the high temperature of the upper atmosphere heated by the far and extreme UV combined with the tidal forces allow a very efficient evaporation of the upper atmosphere. We will review the different models and their implications, in particular in the light of the new Kepler results. Finally we will also present the latest observations of the gas escaping HD189833b. These observations have been obtained with the repaired HST/STIS.

  20. Exploration of Impinging Water Spray Heat Transfer at System Pressures Near the Triple Point

    NASA Technical Reports Server (NTRS)

    Golliher, Eric L.; Yao, Shi-Chune

    2013-01-01

    The heat transfer of a water spray impinging upon a surface in a very low pressure environment is of interest to cooling of space vehicles during launch and re-entry, and to industrial processes where flash evaporation occurs. At very low pressure, the process occurs near the triple point of water, and there exists a transient multiphase transport problem of ice, water and water vapor. At the impingement location, there are three heat transfer mechanisms: evaporation, freezing and sublimation. A preliminary heat transfer model was developed to explore the interaction of these mechanisms at the surface and within the spray.

  1. A numerical simulation of the dispersal of aerial sprays

    NASA Technical Reports Server (NTRS)

    Bragg, M. B.

    1981-01-01

    A computer program was developed to predict the trajectory, ground deposition, and drift of liquid sprays injected into the wake of an agricultural aircraft in ground effect. The program uses a horseshoe vortex wake model and includes the effects of liquid droplet evaporation, crosswind, the propeller slipstream, ground effect, and tunnel walls on small scale models. This user's guide includes several case examples demonstrating user options. A complete listing of the FORTRAN program is provided.

  2. SPRAY CALCINATION REACTOR

    DOEpatents

    Johnson, B.M.

    1963-08-20

    A spray calcination reactor for calcining reprocessin- g waste solutions is described. Coaxial within the outer shell of the reactor is a shorter inner shell having heated walls and with open regions above and below. When the solution is sprayed into the irner shell droplets are entrained by a current of gas that moves downwardly within the inner shell and upwardly between it and the outer shell, and while thus being circulated the droplets are calcined to solids, whlch drop to the bottom without being deposited on the walls. (AEC) H03 H0233412 The average molecular weights of four diallyl phthalate polymer samples extruded from the experimental rheometer were redetermined using the vapor phase osmometer. An amine curing agent is required for obtaining suitable silver- filled epoxy-bonded conductive adhesives. When the curing agent was modified with a 47% polyurethane resin, its effectiveness was hampered. Neither silver nor nickel filler impart a high electrical conductivity to Adiprenebased adhesives. Silver filler was found to perform well in Dow-Corning A-4000 adhesive. Two cascaded hot-wire columns are being used to remove heavy gaseous impurities from methane. This purified gas is being enriched in the concentric tube unit to approximately 20% carbon-13. Studies to count low-level krypton-85 in xenon are continuing. The parameters of the counting technique are being determined. The bismuth isotopes produced in bismuth irradiated for polonium production are being determined. Preliminary data indicate the presence of bismuth207 and bismuth-210m. The light bismuth isotopes are probably produced by (n,xn) reactions bismuth-209. The separation of uranium-234 from plutonium-238 solutions was demonstrated. The bulk of the plutonium is removed by anion exchange, and the remainder is extracted from the uranium by solvent extraction techniques. About 99% of the plutonium can be removed in each thenoyltrifluoroacetone extraction. The viscosity, liquid density, and

  3. 40 CFR 86.117-96 - Evaporative emission enclosure calibrations.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... calibration. Methanol measurements may be omitted if methanol-fueled vehicles will not be tested in the.... When methanol as well as hydrocarbons are present in the evaporative enclosure, the HFID hydrocarbon concentration measurement includes the partial response of the HFID to methanol plus the...

  4. 40 CFR 86.1824-08 - Durability demonstration procedures for evaporative emissions.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... permeability of evaporative and fuel system components. The manufacturer must also provide information... control systems. Manufacturers may base the bench procedure on an evaluation the following potential... manufacturer begins its mileage accumulation. The manufacturer must also provide information acceptable to...

  5. 40 CFR 86.1824-08 - Durability demonstration procedures for evaporative emissions.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... permeability of evaporative and fuel system components. The manufacturer must also provide information... control systems. Manufacturers may base the bench procedure on an evaluation the following potential... manufacturer begins its mileage accumulation. The manufacturer must also provide information acceptable to...

  6. 40 CFR 86.1824-08 - Durability demonstration procedures for evaporative emissions.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... permeability of evaporative and fuel system components. The manufacturer must also provide information... control systems. Manufacturers may base the bench procedure on an evaluation the following potential... manufacturer begins its mileage accumulation. The manufacturer must also provide information acceptable to...

  7. 40 CFR 86.1824-08 - Durability demonstration procedures for evaporative emissions.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... permeability of evaporative and fuel system components. The manufacturer must also provide information... control systems. Manufacturers may base the bench procedure on an evaluation the following potential... manufacturer begins its mileage accumulation. The manufacturer must also provide information acceptable to...

  8. Nasal corticosteroid sprays

    MedlinePlus

    ... best for decreasing symptoms during that season. Several brands of nasal corticosteroid sprays are available. They all ... urac.org). URAC's accreditation program is an independent audit to verify that A.D.A.M. follows ...

  9. Budesonide Nasal Spray

    MedlinePlus

    ... by an allergy to pollen, mold, dust, or pets). Budesonide nasal spray should not be used to ... disposed of in special ways to ensure that pets, children, and other people cannot consume them. However, ...

  10. Fluticasone Nasal Spray

    MedlinePlus

    ... the pump until you see a fine spray. Blow your nose until your nostrils are clear. Hold ... chills, cough, and other signs of infection whistling sound from the nose hives rash itching swelling of ...

  11. Supersonic-Spray Cleaner

    NASA Technical Reports Server (NTRS)

    Caimi, Raoul E. B.; Lin, Feng-Nan; Thaxton, Eric A.

    1995-01-01

    Spraying system for cleaning mechanical components uses less liquid and operates at pressures significantly lower. Liquid currently used is water. Designed to replace chlorofluorocarbon (CFC) solvent-based cleaning and cleanliness verification methods. Consists of spray head containing supersonic converging/diverging nozzles, source of gas at regulated pressure, pressurized liquid tank, and various hoses, fittings, valves, and gauges. Parameters of nozzles set so any of large variety of liquids and gases combined in desired ratio and rate of flow. Size and number of nozzles varied so system built in configurations ranging from small hand-held spray heads to large multinozzle cleaners. Also used to verify part adequately cleaned. Runoff liquid from spray directed at part collected. Liquid analyzed for presence of contaminants, and part recleaned if necessary.

  12. Beclomethasone Nasal Spray

    MedlinePlus

    ... the lining of the nose) after nasal polyp removal surgery. Beclomethasone nasal spray should not be used ... room temperature and away from excess heat and moisture (not in the bathroom).Unneeded medications should be ...

  13. Ciclesonide Nasal Spray

    MedlinePlus

    ... runny or itchy nose. Ciclesonide is in a class of medications called corticosteroids. It works by preventing ... hold the bottle firmly with your forefinger and middle finger on either side of the spray tip ...

  14. Flunisolide Nasal Spray

    MedlinePlus

    ... by the common cold. It is in a class of medications called corticosteroids. It works by blocking ... spray with the applicator between your forefinger and middle finger and the bottom of the bottle resting ...

  15. Nicotine Nasal Spray

    MedlinePlus

    ... the bottle in front of a tissue or paper towel. Pump the spray bottle six to eight times ... up the spill immediately with a cloth or paper towel. Avoid touching the liquid. Throw away the used ...

  16. Dropwise Evaporative Cooling of Heated Surfaces with Various Wettability Characteristics Obtained by Nanostructure Modifications

    NASA Astrophysics Data System (ADS)

    Chen, Jian-nan; Zhang, Zhen; Ouyang, Xiao-long; Jiang, Pei-xue

    2016-03-01

    A numerical and experimental investigation was conducted to analyze dropwise evaporative cooling of heated surfaces with various wettability characteristics. The surface wettability was tuned by nanostructure modifications. Spray-cooling experiments on these surfaces show that surfaces with better wettability have better heat transfer rate and higher critical heat flux (CHF). Single droplet impingement evaporative cooling of a heated surface was then investigated numerically with various wettability conditions to characterize the effect of contact angle on spray-cooling heat transfer. The volume of fluid (VOF) model with variable-time stepping was used to capture the time-dependent liquid-gas interface motion throughout the computational domain with the kinetic theory model used to predict the evaporation rate at the liquid-gas interface. The numerical results agree with the spray-cooling experiments that dropwise evaporative cooling is much better on surfaces with better wettability because of the better liquid spreading and convection, better liquid-solid contact, and stronger liquid evaporation.

  17. Dropwise Evaporative Cooling of Heated Surfaces with Various Wettability Characteristics Obtained by Nanostructure Modifications.

    PubMed

    Chen, Jian-Nan; Zhang, Zhen; Ouyang, Xiao-Long; Jiang, Pei-Xue

    2016-12-01

    A numerical and experimental investigation was conducted to analyze dropwise evaporative cooling of heated surfaces with various wettability characteristics. The surface wettability was tuned by nanostructure modifications. Spray-cooling experiments on these surfaces show that surfaces with better wettability have better heat transfer rate and higher critical heat flux (CHF). Single droplet impingement evaporative cooling of a heated surface was then investigated numerically with various wettability conditions to characterize the effect of contact angle on spray-cooling heat transfer. The volume of fluid (VOF) model with variable-time stepping was used to capture the time-dependent liquid-gas interface motion throughout the computational domain with the kinetic theory model used to predict the evaporation rate at the liquid-gas interface. The numerical results agree with the spray-cooling experiments that dropwise evaporative cooling is much better on surfaces with better wettability because of the better liquid spreading and convection, better liquid-solid contact, and stronger liquid evaporation.

  18. Simulation of spray development and turbulent combustion processes in low and high speed diesel engines by the CMC-ISR model

    NASA Astrophysics Data System (ADS)

    Lee, Young J.; Huh, Kang Y.

    2012-02-01

    Simulation is performed to analyse the characteristics of turbulent spray combustion in conventional low and high speed diesel engine conditions. Turbulence-chemistry interaction is resolved by the Conditional Moment Closure (CMC) model in the spatially integrated form of an Incompletely Stirred Reactor (ISR). After validation against measured pressure traces, characteristic length and time scales and dimensionless numbers are estimated at the locations of sequentially injected fuel groups. Conditional flame structures are calculated for sequentially evaporated fuel groups to consider different available periods for ignition chemistry. Injection overlaps the combustion period in the high rpm engine, while most combustion occurs after injection and evaporation are complete in the low rpm engine. Ignition occurs in rich premixture with the initial peak temperature at the equivalence ratio around 2-4 as observed in Dec [2]. It corresponds to the most reactive mixture fraction of the minimum ignition delay for the given mixture states. Combustion proceeds to lean and rich sides in the mixture fraction space as a diffusion process by turbulence. The mean scalar dissipation rates (SDRs) are lower than the extinction limit to show stability of diffusion flames throughout the combustion period.

  19. 40 CFR 86.1821-01 - Evaporative/refueling family determination.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 19 2010-07-01 2010-07-01 false Evaporative/refueling family... family determination. (a) The gasoline-, methanol-, liquefied petroleum gas-, and natural gas-fueled... emission characteristics shall be defined as a separate evaporative/refueling family. Manufacturers...

  20. 40 CFR 86.1821-01 - Evaporative/refueling family determination.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... evaporative/refueling family. Manufacturers shall use good engineering judgment to determine evaporative... storage device (e.g., canister, air cleaner, crankcase). (2) Basic canister design. (i) Working capacity... connection (i.e., series, parallel). (iii) Canister geometry, construction and materials. (3) Fuel system. (4...

  1. Analysis of Evaporative On-Board Diagnostic (OBD) Readiness and DTCs Using I/M Data

    EPA Science Inventory

    Gasoline vehicles are equipped with evaporative emissions control systems that control vapor from the fuel storage system while a vehicle is sitting or driving. When these systems or the vehicle’s gasoline delivery system malfunction, excessive evaporative emissions can be emitte...

  2. Analysis of Evaporative On-Board Diagnostic (OBD) Readiness and DTCs Using I/M Data

    EPA Science Inventory

    Gasoline vehicles are equipped with evaporative emissions control systems that control vapor from the fuel storage system while a vehicle is sitting or driving. When these systems or the vehicle’s gasoline delivery system malfunction, excessive evaporative emissions can be emitte...

  3. Spray applicator for spraying coatings and other fluids in space

    NASA Technical Reports Server (NTRS)

    Kuminecz, J. F.; Lausten, M. F. (Inventor)

    1985-01-01

    A self contained spray application is developed for one handed operation in a zero gravity vacuum environment by a free flying astronaut not attached to any spacecraft. This spray applicator eliminates contamination of the operator by back spray. This applicator includes a rigid accumulator containment of a fluid within a flexible bladder the fluid being urged out of the accumulator under pressure through a spray gun. The spray gun includes a spring loaded lockable trigger which controls a valve. When in an open position, the fluid passes through the valve into the ambient environment in the form of a spray. A spray shield is provided which directs the flow of the spray from the applicator by trapping errant particles of spray yet allowing the passage of escaping gases through its material.

  4. Directed spray mast

    DOEpatents

    Nance, Thomas A.; Siddall, Alvin A.; Cheng, William Y.; Counts, Kevin T.

    2005-05-10

    Disclosed is an elongated, tubular, compact high pressure sprayer apparatus for insertion into an access port of vessels having contaminated interior areas that require cleaning by high pressure water spray. The invention includes a spray nozzle and a camera adjacent thereto with means for rotating and raising and lowering the nozzle so that areas identified through the camera may be cleaned with a minimum production of waste water to be removed.

  5. Metal atomization spray nozzle

    DOEpatents

    Huxford, Theodore J.

    1993-01-01

    A spray nozzle for a magnetohydrodynamic atomization apparatus has a feed passage for molten metal and a pair of spray electrodes mounted in the feed passage. The electrodes, diverging surfaces which define a nozzle throat and diverge at an acute angle from the throat. Current passes through molten metal when fed through the throat which creates the Lorentz force necessary to provide atomization of the molten metal.

  6. Metal atomization spray nozzle

    DOEpatents

    Huxford, T.J.

    1993-11-16

    A spray nozzle for a magnetohydrodynamic atomization apparatus has a feed passage for molten metal and a pair of spray electrodes mounted in the feed passage. The electrodes, diverging surfaces which define a nozzle throat and diverge at an acute angle from the throat. Current passes through molten metal when fed through the throat which creates the Lorentz force necessary to provide atomization of the molten metal. 6 figures.

  7. 40 CFR 86.1246-96 - Fuel dispensing spitback procedure.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... PROGRAMS (CONTINUED) CONTROL OF EMISSIONS FROM NEW AND IN-USE HIGHWAY VEHICLES AND ENGINES (CONTINUED) Evaporative Emission Test Procedures for New Gasoline-Fueled, Natural Gas-Fueled, Liquefied Petroleum Gas-Fueled and Methanol-Fueled Heavy-Duty Vehicles § 86.1246-96 Fuel dispensing spitback procedure. (a)...

  8. Numerical simulation of internal and near-nozzle flow of a gasoline direct injection fuel injector

    NASA Astrophysics Data System (ADS)

    Saha, Kaushik; Som, Sibendu; Battistoni, Michele; Li, Yanheng; Quan, Shaoping; Senecal, Peter Kelly

    2015-12-01

    A numerical study of two-phase flow inside the nozzle holes and the issuing spray jets for a multi-hole direct injection gasoline injector has been presented in this work. The injector geometry is representative of the Spray G nozzle, an eight-hole counterbore injector, from, the Engine Combustion Network (ECN). Simulations have been carried out for the fixed needle lift. Effects of turbulence, compressibility and, non-condensable gases have been considered in this work. Standard k—ɛ turbulence model has been used to model the turbulence. Homogeneous Relaxation Model (HRM) coupled with Volume of Fluid (VOF) approach has been utilized to capture the phase change phenomena inside and outside the injector nozzle. Three different boundary conditions for the outlet domain have been imposed to examine non-flashing and evaporative, non-flashing and non-evaporative, and flashing conditions. Inside the nozzle holes mild cavitation-like and in the near-nozzle region flash boiling phenomena have been predicted in this study when liquid fuel is subjected to superheated ambiance. Noticeable hole to hole variation has been also observed in terms of mass flow rates for all the holes under both flashing and non-flashing conditions.

  9. Modeling of internal and near-nozzle flow for a GDI fuel injector

    SciTech Connect

    Saha, Kaushik; Som, Sibendu; Battistoni, Michele; Li, Yanheng; Quan, Shaoping; Senecal, Peter Kelly

    2015-11-08

    A numerical study of two-phase flow inside the nozzle holes and the issuing spray jets for a multi-hole direct injection gasoline injector has been presented in this work. The injector geometry is representative of the Spray G nozzle, an eight-hole counterbore injector, from the Engine Combustion Network (ECN). Simulations have been carried out for a fixed needle lift. Effects of turbulence, compressibility and non-condensable gases have been considered in this work. Standard k -ε turbulence model has been used to model the turbulence. Homogeneous Relaxation Model (HRM) coupled with Volume of Fluid (VOF) approach has been utilized to capture the phase change phenomena inside and outside the injector nozzle. Three different boundary conditions for the outlet domain have been imposed to examine non-flashing and evaporative, non-flashing and non-evaporative and flashing conditions. Noticeable hole-to-hole variations have been observed in terms of mass flow rates for all the holes under all the operating conditions considered in this study. Inside the nozzle holes mild cavitation-like and in the near-nozzle region flash boiling phenomena have been predicted when liquid fuel is subjected to superheated ambiance. Under favorable conditions considerable flashing has been observed in the near-nozzle regions. An enormous volume is occupied by the gasoline vapor, stantial computational cost. Volume-averaging instead of mass-averaging is observed to be more effective, especially for finer mesh resolutions.

  10. Effects of Turbulence Characteristics in the Spray Combustion

    NASA Astrophysics Data System (ADS)

    Takeuchi, Seiichi; Douhara, Noriyoshi

    The present study was conducted in order to clarify the effects of airflow turbulence on the spray combustion. Methanol was atomized with the two-fluid-type nozzle in order to generate the spray flame, and the turbulence characteristic of the flame was varied by inserting a mesh near the tip of the nozzle. Droplets in the spray flame were measured using a PDPA system in a reaction field, and changes in the turbulence characteristic were measured using a hot-wire anemometer in a no-reaction field in order to clarify the effects of turbulence on combustion behavior. Inserting a finer mesh promoted droplet evaporation and enhanced the dispersion characteristic. Regarding changes in the turbulence characteristic, the integral time scale increased and the energy spectrum decreased as the inserted mesh became finer. Based on the obtained results, we determined that a finer mesh causes vortexes to be more persistent and enhances the dispersion characteristic of the droplets.

  11. Plasma-sprayed coatings

    SciTech Connect

    Herman, H.

    1988-09-01

    Plasma spraying is one way to apply protective coatings. The hot, high-speed flame of a plasma gun can melt a powder of almost any ceramic or metal and spray it to form a coating for protection against corrosion, wear or high temperature. The technique carries much less risk of degrading the coating and substrate than many other high-temperature processes do, because the gas in the plasma flame is chemically inert and the target can be kept fairly cool. And yet a plasma gun can be only a little more cumbersome than a paint sprayer. Investigators are applying this technique to new materials. The General Electric Company is using vacuum plasma spraying to make freestanding components: intricate aircraft engine parts formed by plasma-spraying a superalloy on a removable substrate. Other workers spray ceramic particles or fibers and metal powder simulatious wrong, stiff composite materials: the ceramic particles dispersed in a matrix of metal. The author and colleagues at the U.S. Naval Research Laboratory have fabricated a thick film of high-temperature superconductor by plasma-spraying the compound in the form of a powder. 7 figs.

  12. Structure of confined laminar spray diffusion flames: Numerical investigation

    NASA Technical Reports Server (NTRS)

    Mawid, M. A.; Bulzan, D. L.; Aggarwal, S. K.

    1993-01-01

    The structure of confined laminar spray diffusion flames is investigated numerically by solving the gas-phase conservation equations for mass species, continuity, momentum, and energy and the liquid-phase equations for droplet position, velocity, size, and temperature. A one-step global reaction scheme along with six equilibrium reactions are employed to model the flame chemistry. Monodisperse as well as polydisperse sprays are considered. The numerical results demonstrate that liquid spray flames substantially differ from gaseous flames in their structure, i.e., temperature, concentration, and velocity fields, shape, and dimensions under the same conditions. Spray flames are predicted to be taller and narrower than their counterpart gaseous ones and their shapes are almost cylindrical. This is in agreement with experimental observations. The numerical computations also show that the use of the equilibrium reactions with the one-step reaction scheme decreases the flame temperature compared to the one-step reaction scheme without the equilibrium reactions and more importantly increases the surface area of the flame zone due to a phenomenon termed 'equilibrium broadening.' The spray flames also possess a finite thickness with minimal overlap of the fuel and oxygen species. A case for which a fuel-mixture consisting of 20 to 80 percent gas-liquid by mass is introduced into the combustor is also investigated and compared with predictions using only gaseous or liquid fuel.

  13. Optical Fuel Injector Patternation Measurements in Advanced Liquid-Fueled, High Pressure, Gas Turbine Combustors

    NASA Technical Reports Server (NTRS)

    Locke, R. J.; Hicks, Y. R.; Anderson, R. C.; Zaller, M. M.

    1998-01-01

    Planar laser-induced fluorescence (PLIF) imaging and planar Mie scattering are used to examine the fuel distribution pattern (patternation) for advanced fuel injector concepts in kerosene burning, high pressure gas turbine combustors. Three fuel injector concepts for aerospace applications were investigated under a broad range of operating conditions. Fuel PLIF patternation results are contrasted with those obtained by planar Mie scattering. For one injector, further comparison is also made with data obtained through phase Doppler measurements. Differences in spray patterns for diverse conditions and fuel injector configurations are readily discernible. An examination of the data has shown that a direct determination of the fuel spray angle at realistic conditions is also possible. The results obtained in this study demonstrate the applicability and usefulness of these nonintrusive optical techniques for investigating fuel spray patternation under actual combustor conditions.

  14. AE Monitoring and Analysis of HVOF Thermal Spraying Process

    NASA Astrophysics Data System (ADS)

    Faisal, N. H.; Ahmed, R.; Reuben, R. L.; Allcock, B.

    2011-09-01

    This work presents an in situ monitoring of HVOF thermal spraying process through an acoustic emission (AE) technique in an industrial coating chamber. Single layer thermal spraying on substrate was carried out through slits. Continuous multilayer thermal spraying onto the sample without slit was also conducted. The AE was measured using a broadband piezoelectric AE sensor positioned on the back of the substrate. A mathematical model has been developed to determine the total kinetic energy of particles impacting the substrate through slits. Results of this work demonstrate that AE associated with particle impacts can be used for in situ monitoring of coating process. Results also show that the amplitude and AE energy is related to the spray gun transverse speed and the oxy-fuel pressure. The measured AE energy was found to vary with the number of particles impacting the substrate, determined using the mathematical model.

  15. Gas Permeability of Porous Plasma-Sprayed Coatings

    NASA Astrophysics Data System (ADS)

    Wittmann-Ténèze, K.; Caron, N.; Alexandre, S.

    2008-12-01

    For different applications, such as solid oxide fuel cells, there is an interest in understanding the relationship between the microstructure and the gas permeability of plasma-sprayed coatings. Nevertheless, plasma spraying processes allow to elaborate coatings with singular microstructures, depending strongly on the initial material and plasma operating conditions. And so, the evolution of permeability is not directly linked to the porosity. In this work, coatings were manufactured using different initial feedstock and spray parameters to obtain various microporous structures. Measurements of their permeation with the pressure drop method and their open porosity just as the observation of the morphology and the structure by optical microscopy were achieved. The different data show that the evolution of the gas permeability with the open porosity follows the Kozeny-Carman equation. This result correlated with the microstructural observation highlights the relationship between the permeability and the physical properties of porous plasma-sprayed layers.

  16. Lanthanide-based laser-induced phosphorescence for spray diagnostics.

    PubMed

    van der Voort, D D; Maes, N C J; Lamberts, T; Sweep, A M; van de Water, W; Kunnen, R P J; Clercx, H J H; van Heijst, G J F; Dam, N J

    2016-03-01

    Laser-induced phosphorescence (LIP) is a relatively recent and versatile development for studying flow dynamics. This work investigates certain lanthanide-based molecular complexes for their use in LIP for high-speed sprays. Lanthanide complexes in solutions have been shown to possess long phosphorescence lifetimes (∼1-2 ms) and to emit light in the visible wavelength range. In particular, europium and terbium complexes are investigated using fluorescence/phosphorescence spectrometry, showing that europium-thenoyltrifluoracetone-trioctylphosphineoxide (Eu-TTA-TOPO) can be easily and efficiently excited using a standard frequency-tripled Nd:YAG laser. The emitted spectrum, with maximum intensity at a wavelength of 614 nm, is shown not to vary strongly with temperature (293-383 K). The decay constant of the phosphorescence, while independent of ambient pressure, decreases by approximately 12 μs/K between 323 and 373 K, with the base level of the decay constant dependent on the used solvent. The complex does not luminesce in the gas or solid state, meaning only the liquid phase is visualized, even in an evaporating spray. By using an internally excited spray containing the phosphorescent complex, the effect of vaporization is shown through the decrease in measured intensity over the length of the spray, together with droplet size measurements using interferometric particle imaging. This study shows that LIP, using the Eu-TTA-TOPO complex, can be used with different solvents, including diesel surrogates. Furthermore, it can be easily handled and used in sprays to investigate spray breakup and evaporation.

  17. Lanthanide-based laser-induced phosphorescence for spray diagnostics

    SciTech Connect

    Voort, D. D. van der Water, W. van de; Kunnen, R. P. J.; Clercx, H. J. H.; Heijst, G. J. F. van; Maes, N. C. J.; Sweep, A. M.; Dam, N. J.; Lamberts, T.

    2016-03-15

    Laser-induced phosphorescence (LIP) is a relatively recent and versatile development for studying flow dynamics. This work investigates certain lanthanide-based molecular complexes for their use in LIP for high-speed sprays. Lanthanide complexes in solutions have been shown to possess long phosphorescence lifetimes (∼1-2 ms) and to emit light in the visible wavelength range. In particular, europium and terbium complexes are investigated using fluorescence/phosphorescence spectrometry, showing that europium-thenoyltrifluoracetone-trioctylphosphineoxide (Eu-TTA-TOPO) can be easily and efficiently excited using a standard frequency-tripled Nd:YAG laser. The emitted spectrum, with maximum intensity at a wavelength of 614 nm, is shown not to vary strongly with temperature (293-383 K). The decay constant of the phosphorescence, while independent of ambient pressure, decreases by approximately 12 μs/K between 323 and 373 K, with the base level of the decay constant dependent on the used solvent. The complex does not luminesce in the gas or solid state, meaning only the liquid phase is visualized, even in an evaporating spray. By using an internally excited spray containing the phosphorescent complex, the effect of vaporization is shown through the decrease in measured intensity over the length of the spray, together with droplet size measurements using interferometric particle imaging. This study shows that LIP, using the Eu-TTA-TOPO complex, can be used with different solvents, including diesel surrogates. Furthermore, it can be easily handled and used in sprays to investigate spray breakup and evaporation.

  18. Lanthanide-based laser-induced phosphorescence for spray diagnostics

    NASA Astrophysics Data System (ADS)

    van der Voort, D. D.; Maes, N. C. J.; Lamberts, T.; Sweep, A. M.; van de Water, W.; Kunnen, R. P. J.; Clercx, H. J. H.; van Heijst, G. J. F.; Dam, N. J.

    2016-03-01

    Laser-induced phosphorescence (LIP) is a relatively recent and versatile development for studying flow dynamics. This work investigates certain lanthanide-based molecular complexes for their use in LIP for high-speed sprays. Lanthanide complexes in solutions have been shown to possess long phosphorescence lifetimes (˜1-2 ms) and to emit light in the visible wavelength range. In particular, europium and terbium complexes are investigated using fluorescence/phosphorescence spectrometry, showing that europium-thenoyltrifluoracetone-trioctylphosphineoxide (Eu-TTA-TOPO) can be easily and efficiently excited using a standard frequency-tripled Nd:YAG laser. The emitted spectrum, with maximum intensity at a wavelength of 614 nm, is shown not to vary strongly with temperature (293-383 K). The decay constant of the phosphorescence, while independent of ambient pressure, decreases by approximately 12 μs/K between 323 and 373 K, with the base level of the decay constant dependent on the used solvent. The complex does not luminesce in the gas or solid state, meaning only the liquid phase is visualized, even in an evaporating spray. By using an internally excited spray containing the phosphorescent complex, the effect of vaporization is shown through the decrease in measured intensity over the length of the spray, together with droplet size measurements using interferometric particle imaging. This study shows that LIP, using the Eu-TTA-TOPO complex, can be used with different solvents, including diesel surrogates. Furthermore, it can be easily handled and used in sprays to investigate spray breakup and evaporation.

  19. Method of evaporation

    NASA Technical Reports Server (NTRS)

    Dufresne, Eugene R.

    1987-01-01

    Liquids, such as juices, milk, molten metal and the like are concentrated by forming uniformly-sized, small droplets in a precision droplet forming assembly and deploying the droplets in free fall downwardly as a central column within an evacuated column with cool walls. A portion of the solvent evaporates. The vapor flows to the wall, condenses, and usually flows down the wall as a film to condensate collector and drain. The vertical column of freely falling droplets enters the splash guard. The condensate can be collected, sent to other towers or recycled.

  20. Effective micro-spray cooling for light-emitting diode with graphene nanoporous layers.

    PubMed

    Lay, Kok Keong; Cheong, Brian Mun Yew; Tong, Wei Li; Tan, Ming Kwang; Hung, Yew Mun

    2017-04-21

    A graphene nanoplatelet (GNP) coating is utilized as a functionalized surface in enhancing the evaporation rate of micro-spray cooling for light-emitting diodes (LEDs). In micro-spray cooling, water is atomized into micro-sized droplets to reduce the surface energy and to increase the surface area for evaporation. The GNP coating facilitates the effective filmwise evaporation through the attribute of fast water permeation. The oxygenated functional groups of GNPs provide the driving force that initiates the intercalation of water molecules through the carbon nanostructure. The water molecules slip through the frictionless passages between the hydrophobic carbon walls, resulting an effective filmwise evaporation. The enhancement of evaporation leads to an enormous temperature reduction of 61.3 °C. The performance of the LED is greatly enhanced: a maximum increase in illuminance of 25% and an extension of power rating from 9 W to 12 W can be achieved. With the application of GNP coating, the high-temperature region is eliminated while maintaining the LED surface temperature for optimal operation. This study paves the way for employing the effective hybrid spray-evaporation-nanostructure technique in the development of a compact, low-power-consumption cooling system.

  1. Effective micro-spray cooling for light-emitting diode with graphene nanoporous layers

    NASA Astrophysics Data System (ADS)

    Keong Lay, Kok; Yew Cheong, Brian Mun; Li Tong, Wei; Tan, Ming Kwang; Hung, Yew Mun

    2017-04-01

    A graphene nanoplatelet (GNP) coating is utilized as a functionalized surface in enhancing the evaporation rate of micro-spray cooling for light-emitting diodes (LEDs). In micro-spray cooling, water is atomized into micro-sized droplets to reduce the surface energy and to increase the surface area for evaporation. The GNP coating facilitates the effective filmwise evaporation through the attribute of fast water permeation. The oxygenated functional groups of GNPs provide the driving force that initiates the intercalation of water molecules through the carbon nanostructure. The water molecules slip through the frictionless passages between the hydrophobic carbon walls, resulting an effective filmwise evaporation. The enhancement of evaporation leads to an enormous temperature reduction of 61.3 °C. The performance of the LED is greatly enhanced: a maximum increase in illuminance of 25% and an extension of power rating from 9 W to 12 W can be achieved. With the application of GNP coating, the high-temperature region is eliminated while maintaining the LED surface temperature for optimal operation. This study paves the way for employing the effective hybrid spray-evaporation-nanostructure technique in the development of a compact, low-power-consumption cooling system.

  2. Spray and High-Pressure Flow Computations in the National Combustion Code (NCC) Improved

    NASA Technical Reports Server (NTRS)

    Raju, Manthena S.

    2002-01-01

    Sprays occur in a wide variety of industrial and power applications and in materials processing. A liquid spray is a two-phase flow with a gas as the continuous phase and a liquid as the dispersed phase in the form of droplets or ligaments. The interactions between the two phases--which are coupled through exchanges of mass, momentum, and energy--can occur in different ways at disparate time and length scales involving various thermal, mass, and fluid dynamic factors. An understanding of the flow, combustion, and thermal properties of a rapidly vaporizing spray requires careful modeling of the ratecontrolling processes associated with turbulent transport, mixing, chemical kinetics, evaporation, and spreading rates of the spray, among many other factors. With the aim of developing an efficient solution procedure for use in multidimensional combustor modeling, researchers at the NASA Glenn Research Center have advanced the state-of-the-art in spray computations in several important ways.

  3. Water injected fuel cell system compressor

    DOEpatents

    Siepierski, James S.; Moore, Barbara S.; Hoch, Martin Monroe

    2001-01-01

    A fuel cell system including a dry compressor for pressurizing air supplied to the cathode side of the fuel cell. An injector sprays a controlled amount of water on to the compressor's rotor(s) to improve the energy efficiency of the compressor. The amount of water sprayed out the rotor(s) is controlled relative to the mass flow rate of air inputted to the compressor.

  4. Modeling of Bulk Evaporation and Condensation

    NASA Technical Reports Server (NTRS)

    Anghaie, S.; Ding, Z.

    1996-01-01

    This report describes the modeling and mathematical formulation of the bulk evaporation and condensation involved in liquid-vapor phase change processes. An internal energy formulation, for these phase change processes that occur under the constraint of constant volume, was studied. Compared to the enthalpy formulation, the internal energy formulation has a more concise and compact form. The velocity and time scales of the interface movement were obtained through scaling analysis and verified by performing detailed numerical experiments. The convection effect induced by the density change was analyzed and found to be negligible compared to the conduction effect. Two iterative methods for updating the value of the vapor phase fraction, the energy based (E-based) and temperature based (T-based) methods, were investigated. Numerical experiments revealed that for the evaporation and condensation problems the E-based method is superior to the T-based method in terms of computational efficiency. The internal energy formulation and the E-based method were used to compute the bulk evaporation and condensation processes under different conditions. The evolution of the phase change processes was investigated. This work provided a basis for the modeling of thermal performance of multi-phase nuclear fuel elements under variable gravity conditions, in which the buoyancy convection due to gravity effects and internal heating are involved.

  5. 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.

  6. Evaporating metal nanocrystal arrays

    NASA Astrophysics Data System (ADS)

    Zhang, Xue; Joy, James C.; Zhao, Chenwei; Kim, Jin Ho; Fernandes, Gustavo; Xu, J. M.; Valles, James M., Jr.

    2017-03-01

    Anodic aluminum oxide (AAO) substrates with a self-ordered triangular array of nanopores provide the means to fabricate multiple forms of nano materials, such as nanowires and nanoparticles. This study focuses on nanostructures that emerge in thin films of metals thermally evaporated onto the surface of AAO. Previous work showed that films of different evaporated metals assume dramatically different structures, e.g. an ordered triangular array of nearly monodisperse nanoparticles forms for lead (Pb) while a polycrystalline nanohoneycomb structure forms for silver (Ag). Here, we present investigations of the effects of substrate temperature and deposition angle that reveal the processes controlling the nano particle array formation. Our findings indicate that arrays form provided the grain nucleation density exceeds the pore density and the atomic mobility is high enough to promote grain coalescence. They introduce a method for producing films with anisotropic grain array structure. The results provide insight into the influence of substrate nano-morphology on thin film growth energetics and kinetics that can be harnessed for creating films with other novel nano-structures.

  7. Evaporating metal nanocrystal arrays.

    PubMed

    Zhang, Xue; Joy, James C; Zhao, Chenwei; Kim, Jin Ho; Fernandes, Gustavo; Xu, J M; Valles, James M

    2017-03-10

    Anodic aluminum oxide (AAO) substrates with a self-ordered triangular array of nanopores provide the means to fabricate multiple forms of nano materials, such as nanowires and nanoparticles. This study focuses on nanostructures that emerge in thin films of metals thermally evaporated onto the surface of AAO. Previous work showed that films of different evaporated metals assume dramatically different structures, e.g. an ordered triangular array of nearly monodisperse nanoparticles forms for lead (Pb) while a polycrystalline nanohoneycomb structure forms for silver (Ag). Here, we present investigations of the effects of substrate temperature and deposition angle that reveal the processes controlling the nano particle array formation. Our findings indicate that arrays form provided the grain nucleation density exceeds the pore density and the atomic mobility is high enough to promote grain coalescence. They introduce a method for producing films with anisotropic grain array structure. The results provide insight into the influence of substrate nano-morphology on thin film growth energetics and kinetics that can be harnessed for creating films with other novel nano-structures.

  8. Calculation of a hollow-cone liquid spray in a uniform air stream

    NASA Astrophysics Data System (ADS)

    Sturgess, G. J.; Syed, S. A.; McManus, K. R.

    1984-06-01

    Fluid dynamic computer codes for the simulation of flows in gas turbine engine combustion systems are being developed. NASA is currently sponsoring a two-phase program for the evaluation of the performance of current codes, taking into account also an improvement of accuracy, if needed. The present investigation forms a part of this program. The numerical technique used includes a Lagrangian spray model for liquid fuels. The spray model, in conjunction with the turbulence model, determines the distribution of fuel in the burning zone of the combustor. The numerical technique was applied to a hollow-cone pressure atomizer spraying water into a coflowing confined airstream.

  9. Evaporation of inclined water droplets

    NASA Astrophysics Data System (ADS)

    Kim, Jin Young; Hwang, In Gyu; Weon, Byung Mook

    2017-02-01

    When a drop is placed on a flat substrate tilted at an inclined angle, it can be deformed by gravity and its initial contact angle divides into front and rear contact angles by inclination. Here we study on evaporation dynamics of a pure water droplet on a flat solid substrate by controlling substrate inclination and measuring mass and volume changes of an evaporating droplet with time. We find that complete evaporation time of an inclined droplet becomes longer as gravitational influence by inclination becomes stronger. The gravity itself does not change the evaporation dynamics directly, whereas the gravity-induced droplet deformation increases the difference between front and rear angles, which quickens the onset of depinning and consequently reduces the contact radius. This result makes the evaporation rate of an inclined droplet to be slow. This finding would be important to improve understanding on evaporation dynamics of inclined droplets.

  10. Reservoir evaporation in Texas, USA

    NASA Astrophysics Data System (ADS)

    Wurbs, Ralph A.; Ayala, Rolando A.

    2014-03-01

    The role of reservoir surface evaporation in river/reservoir water budgets and water management is explored using a modeling system that combines historical natural hydrology with current conditions of water resources development and management. The long-term mean evaporation from the 3415 reservoirs in the Texas water rights permit system is estimated to be 7.53 billion m3/year, which is equivalent to 61% of total agricultural or 126% of total municipal water use in the state during the year 2010. Evaporation varies with the hydrologic conditions governing reservoir surface areas and evaporation rates. Annual statewide total evaporation volumes associated with exceedance probabilities of 75%, 50%, and 25% are 7.07, 7.47, and 7.95 billion m3/year, respectively. Impacts of evaporation are greatest during extended severe droughts that govern water supply capabilities.

  11. Evaporation of inclined water droplets.

    PubMed

    Kim, Jin Young; Hwang, In Gyu; Weon, Byung Mook

    2017-02-16

    When a drop is placed on a flat substrate tilted at an inclined angle, it can be deformed by gravity and its initial contact angle divides into front and rear contact angles by inclination. Here we study on evaporation dynamics of a pure water droplet on a flat solid substrate by controlling substrate inclination and measuring mass and volume changes of an evaporating droplet with time. We find that complete evaporation time of an inclined droplet becomes longer as gravitational influence by inclination becomes stronger. The gravity itself does not change the evaporation dynamics directly, whereas the gravity-induced droplet deformation increases the difference between front and rear angles, which quickens the onset of depinning and consequently reduces the contact radius. This result makes the evaporation rate of an inclined droplet to be slow. This finding would be important to improve understanding on evaporation dynamics of inclined droplets.

  12. Evaporation of inclined water droplets

    PubMed Central

    Kim, Jin Young; Hwang, In Gyu; Weon, Byung Mook

    2017-01-01

    When a drop is placed on a flat substrate tilted at an inclined angle, it can be deformed by gravity and its initial contact angle divides into front and rear contact angles by inclination. Here we study on evaporation dynamics of a pure water droplet on a flat solid substrate by controlling substrate inclination and measuring mass and volume changes of an evaporating droplet with time. We find that complete evaporation time of an inclined droplet becomes longer as gravitational influence by inclination becomes stronger. The gravity itself does not change the evaporation dynamics directly, whereas the gravity-induced droplet deformation increases the difference between front and rear angles, which quickens the onset of depinning and consequently reduces the contact radius. This result makes the evaporation rate of an inclined droplet to be slow. This finding would be important to improve understanding on evaporation dynamics of inclined droplets. PMID:28205642

  13. Representative shuttle evaporative heat sink

    NASA Technical Reports Server (NTRS)

    Hixon, C. W.

    1978-01-01

    The design, fabrication, and testing of a representative shuttle evaporative heat sink (RSEHS) system which vaporizes an expendable fluid to provide cooling for the shuttle heat transport fluid loop is reported. The optimized RSEHS minimum weight design meets or exceeds the shuttle flash evaporator system requirements. A cold trap which cryo-pumps flash evaporator exhaust water from the CSD vacuum chamber test facility to prevent water contamination of the chamber pumping equipment is also described.

  14. Thermal spray processing

    NASA Technical Reports Server (NTRS)

    Herman, H.; Berndt, C. C.

    1995-01-01

    Thermal spray processing has been used for a number of years to cost-effecticely apply TBC's for a wide range of heat engine applications. In particular, bond coats are applied by plasma spray and HVOF techniques and partially-stabilized zirconia top coats are applied by plasma spray methods. Thermal spray involves melting and rapid transport of the molten particles to the substrate, where high-rate solidification and coating build-up occur. It is the very nature of this melt processing that leads to the unique layered microstructure, as well as the apparent imperfections, so readily identified with thermal spray. Modeling the process, process-induced residual stresses, and thermal conductivity will be discussed in light of a new understanding of porosity and its anisotropy. Microcracking can be understood using new approaches, allowing a fuller view of the processing-performance connection. Detailed electron microscopic, novel neutron diffraction and fracture analysis of the deposits can lead to a better understanding of how overall microstructure can be controlled to influence critical properties of the deposited TBC system.

  15. Liquid sprays and flow studies in the direct-injection diesel engine under motored conditions

    NASA Technical Reports Server (NTRS)

    Nguyen, Hung Lee; Carpenter, Mark H.; Ramos, Juan I.; Schock, Harold J.; Stegeman, James D.

    1988-01-01

    A two dimensional, implicit finite difference method of the control volume variety, a two equation model of turbulence, and a discrete droplet model were used to study the flow field, turbulence levels, fuel penetration, vaporization, and mixing in diesel engine environments. The model was also used to study the effects of engine speed, injection angle, spray cone angle, droplet distribution, and intake swirl angle on the flow field, spray penetration and vaporization, and turbulence in motored two-stroke diesel engines. It is shown that there are optimum conditions for injection, which depend on droplet distribution, swirl, spray cone angle, and injection angle. The optimum conditions result in good spray penetration and vaporization and in good fuel mixing. The calculation presented clearly indicates that internal combustion engine models can be used to assess, at least qualitatively, the effects of injection characteristics and engine operating conditions on the flow field and on the spray penetration and vaporization in diesel engines.

  16. Numerical simulation of evaporating liquid jet in crossflow

    NASA Astrophysics Data System (ADS)

    Soteriou, Marios; Li, Xiaoyi

    2014-11-01

    Atomization of liquid fuel jets by cross-flowing air is critical to combustor performance. Ability to experimentally probe the fundamentals of this multiscale two phase flows has been hampered by limitations in experimental techniques and the challenges posed by operating conditions. Direct numerical simulation has recently emerged as a promising alternative due to advances in computer hardware and numerical methods. Using this approach, we recently demonstrated the ability to reproduce the physics of atomization of a liquid jet in cross-flow (LJIC) under ambient conditions. In this work we consider this flow in a high temperature environment. The inclusion of evaporation is the major new element. The numerical approach employs the CLSVOF method to capture the liquid-gas interface. Interface evaporation is solved directly with proper treatment of interface conditions and reproduces the relevant species/temperature fields there. A Lagrangian droplet tracking approach is used for the small droplets which are transferred from the Eulerian phase and evaporate using a traditional d2 law model. Other key algorithms of the massively parallelized solver include a ghost fluid method, a multi-grid preconditioned conjugate gradient approach and an adaptive mesh refinement technique. The overall method is verified using canonical problems. Simulations of evaporating LJIC point to the significant effect that evaporation has on the evolution of this flow and elucidate the downstream fuel species patterns.

  17. Evaporation control research, 1959-60

    USGS Publications Warehouse

    ,

    1963-01-01

    Two hundred and forty-five dispersions of long-chain alkanols were formulated by using various emulsifiers and alkanols. The dispensing and spreading ability of each of these formulations was tested. The most promising emulsifier that could be used with any of the alkanols was glyceryl monostearate (self-emulsifying). However, the concentration of the alkanol in the dispersion form varied somewhat: with the length of the carbon chain. A maximum concentration of 16 percent was obtained using the longer chain alkanols in the dispersion form without losing any of the properties of a fluid. Nine field tests were undertaken on small stock tanks. The retardant materials used in these tests were dodecanol, hexadecanol, and octadecanol. These materials were applied in either liquid or dispersion form. Four types of dispensing equipment were tested. The first type used a pressure system which sprayed a liquid onto the surface of the water. An anemometer and wind-controlled vane, operated by an electrical system, determined the length End frequency of application. The second type was similar to the first except that gravity was utilized to force the liquid onto the surface. The third type. used a drip system with rates of about 10 drops per minute. The fourth type used a gravity feed and a wind-controlled valve which allowed the dispersion material to flow onto the surface of the water when the wind was in the proper direction. In the field tests, the best reduction in evaporation was obtained using octadecanol in dispersion form and dispensed with the wind-controlled valve and gravity feed system. The maximum reduction in evaporation for a 2-week period was 27 percent. However, the economics of suppressing evaporation from stock tanks is questionable because of the short travel time across the tank by the film. There are still many problems unsolved. Some of these can be resolved in the laboratory whereas others can be resolved only in the field. Some of the more serious

  18. Modeling nanofluid sessile drop evaporation

    NASA Astrophysics Data System (ADS)

    Gerken, William J.; Oehlschlaeger, Matthew A.

    2017-07-01

    Modeling predictions for the evaporation of nanofluid pinned sessile drops are reported. Drops of fluids containing suspended nanoparticles have reduced evaporation rates relative to their pure fluid counterparts due to the agglomeration of nanoparticles at the surface resulting in a reduction in available liquid at the drop surface for evaporation. The present model implements a mechanism for the reduction in the surface concentration of the evaporating liquid based on the fractal geometry of nanoparticle agglomerates. Nanoparticle packing near the drop pinned contact line results in regions where a maximum nanoparticle volume fraction is attained, leading to significant reductions in the evaporative mass flux. Model predictions for the evaporation rate of pure ethanol and ethanol containing suspended aluminum nanoparticles are compared to experiments from the literature with excellent agreement for the reduction in evaporation rate due to nanoparticle loading and in reasonable quantitative agreement for the evaporation rate. The maximum allowable nanoparticle volume fraction is shown to be an important parameter in governing the evaporation rate of nanofluid sessile drops.

  19. Miniature spray-painting booth

    NASA Technical Reports Server (NTRS)

    Fee, K. W.

    1970-01-01

    Transparent spray booth provides method for quality painting and repair of surfaces in clean room or other specialized environments. Overspray and virtually all contaminating vapor and odor can be eliminated. Touch-up painting is achieved with spray gun.

  20. Nasal spray flu vaccine (image)

    MedlinePlus

    The flu vaccine can also be administered as a nasal spray instead of the usual injection method. It can be ... the recombinant influenza vaccine (RIV). The nasal spray flu vaccine (live attenuated influenza vaccine or LAIV) should not ...