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Sample records for liquid fuel droplets

  1. Combustion of liquid fuel droplets in supercritical conditions

    NASA Technical Reports Server (NTRS)

    Shuen, J. S.; Yang, Vigor

    1991-01-01

    A comprehensive analysis of liquid-fuel droplet combustion in both sub- and super-critical environments has been conducted. The formulation is based on the complete conservation equations for both gas and liquid phases, and accommodates finite-rate chemical kinetics and a full treatment of liquid-vapor phase equilibrium at the droplet surface. The governing equations and the associated interface boundary conditions are solved numerically using a fully coupled, implicit scheme with the dual time-stepping integration technique. The model is capable of treating the entire droplet history, including the transition from the subcritical to the supercritical state. As a specific example, the combustion of n-pentane fuel droplets in air is studied for pressures of 5-140 atm. Results indicate that the ambient gas pressure exerts significant control of droplet gasification and burning processes through its influences on the fluid transport, gas/liquid interface thermodynamics, and chemical reactions. The droplet gasification rate increases progressively with pressure. However, the data for the overall burnout time exhibits a significant variation near the critical burning pressure, mainly as a result of reduced mass-diffusion rate and latent heat of vaporization with increased pressure. The influence of droplet size on the burning characteristics is also noted.

  2. Combustion of liquid fuel droplets in supercritical conditions

    NASA Technical Reports Server (NTRS)

    Shuen, J. S.; Yang, Vigor

    1991-01-01

    A comprehensive analysis of liquid-fuel droplet combustion in both sub- and super-critical environments has been conducted. The formulation is based on the complete conservation equations for both gas and liquid phases, and accommodates finite-rate chemical kinetics and a full treatment of liquid-vapor phase equilibrium at the droplet surface. The governing equations and the associated interface boundary conditions are solved numerically using a fully coupled, implicit scheme with the dual time-stepping integration technique. The model is capable of treating the entire droplet history, including the transition from the subcritical to the supercritical state. As a specific example, the combustion of n-pentane fuel droplets in air is studied for pressures of 5-140 atm. Results indicate that the ambient gas pressure exerts significant control of droplet gasification and burning processes through its influences on the fluid transport, gas/liquid interface thermodynamics, and chemical reactions. The droplet gasification rate increases progressively with pressure. However, the data for the overall burnout time exhibits a significant variation near the critical burning pressure, mainly as a result of reduced mass-diffusion rate and latent heat of vaporization with increased pressure. The influence of droplet size on the burning characteristics is also noted.

  3. Combustion of liquid-fuel droplets in supercritical conditions

    NASA Technical Reports Server (NTRS)

    Shuen, J. S.; Yang, Vigor; Hsaio, C. C.

    1992-01-01

    A comprehensive analysis of liquid-fuel droplet combustion in both subcritical and supercritical environments has been conducted. The formulation is based on the complete conservation equations for both gas and liquid phases, and accommodates variable thermophysical properties, finite-rate chemical kinetics, and a full treatment of liquid-vapor phase equilibrium at the drop surface. The governing equations and associated interfacial boundary conditions are solved numerically using a fully coupled, implicit scheme with the dual time-stepping integration technique. The model is capable of treating the entire droplet history, including the transition from the subcritical to supercritical state. As a specific example, the combustion of n-pentane fuel droplets in air is studied for pressures in the range of 5-140 atm. Results indicate that the ambient gas pressure exerts significant control of droplet gasification and burning processes through its influence on fluid transport, gas-liquid interfacial thermodynamics, and chemical reactions. The droplet gasification rate increases progressively with pressure. However, the data for the overall burnout time exhibit a considerable change in the combustion mechanism at the critical pressure, mainly as a result of reduced mass diffusivity and latent heat of vaporization with increased pressure.

  4. Combustion of liquid-fuel droplets in supercritical conditions

    NASA Technical Reports Server (NTRS)

    Shuen, J. S.; Yang, Vigor; Hsaio, C. C.

    1992-01-01

    A comprehensive analysis of liquid-fuel droplet combustion in both subcritical and supercritical environments has been conducted. The formulation is based on the complete conservation equations for both gas and liquid phases, and accommodates variable thermophysical properties, finite-rate chemical kinetics, and a full treatment of liquid-vapor phase equilibrium at the drop surface. The governing equations and associated interfacial boundary conditions are solved numerically using a fully coupled, implicit scheme with the dual time-stepping integration technique. The model is capable of treating the entire droplet history, including the transition from the subcritical to supercritical state. As a specific example, the combustion of n-pentane fuel droplets in air is studied for pressures in the range of 5-140 atm. Results indicate that the ambient gas pressure exerts significant control of droplet gasification and burning processes through its influence on fluid transport, gas-liquid interfacial thermodynamics, and chemical reactions. The droplet gasification rate increases progressively with pressure. However, the data for the overall burnout time exhibit a considerable change in the combustion mechanism at the critical pressure, mainly as a result of reduced mass diffusivity and latent heat of vaporization with increased pressure.

  5. Acoustic excitation of liquid fuel droplets and coaxial jets

    NASA Astrophysics Data System (ADS)

    Rodriguez, Juan Ignacio

    This experimental study focuses on two important problems relevant to acoustic coupling with condensed phase transport processes, with special relevance to liquid rocket engine and airbreathing engine combustion instabilities. The first part of this dissertation describes droplet combustion characteristics of various fuels during exposure to external acoustical perturbations. Methanol, ethanol, a liquid synthetic fuel derived from coal gasification via the Fischer-Tropsch process, and a blend of aviation fuel and the synthetic fuel are used. During acoustic excitation, the droplet is situated at or near a pressure node condition, where the droplet experiences the largest velocity perturbations, and at or near a pressure antinode condition, where the droplet is exposed to minimal velocity fluctuations. For unforced conditions, the values of the droplet burning rate constant K of the different fuels are consistent with data in the literature. The location of the droplet with respect to a pressure node or antinode also has a measurable effect on droplet burning rates, which are different for different fuels and in some cases are as high as 28% above the unforced burning rate value. Estimates of flame extinction due to acoustic forcing for different fuels are also obtained. The second part of this work consists of an experimental study on coaxial jet behavior under non-reactive, cryogenic conditions, with direct applications to flow mixing and unstable behavior characterization in liquid rocket engines. These experiments, conducted with nitrogen, span a range of outer to inner jet momentum flux ratios from 0.013 to 23, and explore subcritical, nearcritical and supercritical pressure conditions, with and without acoustic excitation, for two injector geometries. Acoustic forcing at 3 kHz is utilized to maximize the pressure fluctuations within the chamber acting on the jet, reaching maximum values of 4% of the mean chamber pressure. The effect of the magnitude and phase

  6. Characterizing droplet combustion of pure and multi-component liquid fuels in a microgravity environment

    NASA Technical Reports Server (NTRS)

    Jackson, Gregory S.; Avedisian, C. Thomas

    1993-01-01

    The importance of understanding the effects of fuel composition, length scales, and other parameters on the combustion of liquid fuels has motivated the examination of simple flames which have easily characterized flow fields and hence, the potential of being modeled accurately. One such flame for liquid fuel combustion is the spherically symmetric droplet flame which can be achieved in an environment with sufficiently low gravity (i.e., low buoyancy). To examine fundamental characteristics of spherically symmetric droplet combustion, a drop tower facility has been employed to provide a microgravity environment to study droplet combustion. This paper gives a brief review of results obtained over the past three years under NASA sponsorship (grant NAG3-987).

  7. Investigation of Critical Burning of Fuel Droplets. [of liquid rocket propellant

    NASA Technical Reports Server (NTRS)

    Chanin, S. P.; Shearer, A. J.; Faeth, G. M.

    1976-01-01

    An earlier analysis for the combustion response of a liquid monopropellant strand (hydrazine) was extended to consider individual droplets and sprays. While small drops gave low or negative response, large droplets provided response near unity at low frequencies, with the response declining at frequencies greater than the characteristic liquid phase frequency. Temperature gradients in the liquid phase resulted in response peaks greater than unity. A second response peak was found for large drops which corresponded to gas phase transient effects. Spray response was generally reduced from the response of the largest injected droplet, however, even a small percentage of large droplets can yield appreciable response. An apparatus was designed and fabricated to allow observation of bipropellant fuel spray combustion at elevated pressures. A locally homogeneous model was developed to describe this combustion process which allows for high pressure phenomena associated with the thermodynamic critical point.

  8. Evolution of temperature of a droplet of liquid composite fuel interacting with heated airflow

    NASA Astrophysics Data System (ADS)

    Glushkov, D. O.; Zakharevich, A. V.; Strizhak, P. A.; Syrodoy, S. V.

    2016-11-01

    The macroscopic patterns of a temperature change at the center of a droplet of three-component (coal, water, petroleum) composite liquid fuel (CLF) were studied using a low-inertia thermoelectric converter and system of high-speed (up to 105 frames per second) video recording during the induction period at different heating intensity by the air flow with variable parameters: temperature of 670-870 K and motion velocity of 1-4 m/s. The studies were carried out for two groups of CLF compositions: fuel based on brown coal and coal cleaning rejects (filter cake). To assess the effect of liquid combustible component of CLF on characteristics of the ignition process, the corresponding composition of two-component coal-water fuel (CWF) was studied. The stages of inert heating of CLF and CWF droplets with characteristic size corresponding to radius of 0.75-1.5 mm, evaporation of moisture and liquid oil (for CLF), thermal decomposition of the organic part of coal, gas mixture ignition, and carbon burnout were identified. Regularities of changes in the temperature of CLF and CWF droplets at each of identified stages were identified for the cooccurrence of phase transitions and chemical reactions. Comparative analysis of the times of ignition delay and complete combustion of the droplets of examined fuel compositions was performed with varying droplet dimensions, temperatures, and oxidant flow velocity.

  9. Acoustic Excitation of Liquid Fuel Droplets and Coaxial Jets

    DTIC Science & Technology

    2009-01-01

    brakes apart from the liquid core (37). The shape of the core in a two dimensional plane intersecting the axis of symmetry of the coaxial flow...Mechanics Tool Kit, Torque Wrench, Caliper , Digital Thermometer and Multimeter. Ensure all tools associated with this experiment/test/operation are

  10. Pressure-coupled vaporization and combustion responses of liquid-fuel droplets in high-pressure environments

    NASA Technical Reports Server (NTRS)

    Yang, Vigor; Shuen, J. S.; Hsiao, C. C.

    1991-01-01

    The dynamic responses of liquid-fuel droplet vaporization and combustion to ambient pressure oscillations are examined. The analysis is based on the complete sets of conservation equations for both gas and liquid phases, and accommodates detailed treatments of finite-rate chemical kinetics and variable properties. With a full account of thermodynamic phase equilibrium at the droplet surface, the model enables a systematic examination of the effects of ambient flow conditions on the droplet behavior. The responses of hydrocarbon fuel droplets in both sub- and super-critical environments are investigated. Results indicate that the droplet gasification and burning mechanisms depend greatly on the ambient pressure. In particular, a rapid enlargement of the vaporization and combustion responses occurs when the droplet surface reaches its critical point, mainly due to the strong variations of latent heat of vaporization and thermophysical properties at the critical state.

  11. Liquid droplet behavior and instability in a polymer electrolyte fuel cell flow channel

    NASA Astrophysics Data System (ADS)

    Kumbur, E. C.; Sharp, K. V.; Mench, M. M.

    A combined theoretical and experimental study of the influence of controllable engineering parameters, including surface PTFE (Teflon™) coverage (ranging from 5 to 20 wt.%), channel geometry, droplet chord length and height, and operational air flow rate, on liquid droplet deformation at the interface of the diffusion media (DM) and the gas flow channel was performed. The theoretical model reasonably predicts the measured contact angle hysteresis and identifies conditions under which the droplet tends toward an unstable state. The results presented in this study indicate that operational conditions, droplet height, chord length, channel size and level of surface hydrophobicity of the DM directly affect the droplet instability. Based on the analytical force balance model, the critical Reynolds number at which a droplet of given dimensions tends towards instability (i.e. may be removed from the channel) is predicted. Experimental data in both the stable and unstable regions as defined by the critical Reynolds number curve generally corresponds to the stability predictions. Empirical correlations relating surface tension and DM PTFE content were developed. At high flow rates, the surface hydrophobicity of the DM surface enhances efficacy of droplet removal, and may help to prevent local channel flooding. However, at low flow rates, hydrophobicity of the DM surface has only a minimal impact on efficacy of droplet removal and therefore high PTFE content may not be necessary, or desirable, since it also increases the electrical resistance of the system. It is also suggested that for constant air velocity and droplet size and shape, reduced channel height is preferred for effective water droplet removal where practical.

  12. Liquid droplet generation

    NASA Technical Reports Server (NTRS)

    Muntz, E. P.; Orme, Melissa; Farnham, Tony; Vandiep, G. Pham; Huerre, P.

    1989-01-01

    A pre-prototype segment of a droplet sheet generator for a liquid droplet radiator was designed, constructed and tested. The ability to achieve a uniform, non-diverging droplet sheet is limited by manufacturing tolerances on nozzle parallelism. For an array of 100, 100 micrometer diameters nozzles spaced 5 stream diameters apart, typical standard deviations in stream alignment were plus or minus 10 mrad. The drop to drop fractional speed variations of the drops in typical streams were similar and independent of position in the array. The absolute value of the speed dispersion depended on the amplitude of the disturbance applied to the stream. A second generation preliminary design of a 5200 stream segment of a droplet sheet generator was completed. The design is based on information developed during testing of the pre-prototype segment, along with the results of an acoustical analysis for the stagnation cavity pressure fluctuations used to break-up the streams into droplets.

  13. Burning Fuel Droplet

    NASA Technical Reports Server (NTRS)

    2003-01-01

    Fuel ignites and burns in the Droplet Combustion Experiment (DCE) on STS-94 on July 4 1997, MET:2/05:40 (approximate). The DCE was designed to investigate the fundamental combustion aspects of single, isolated droplets under different pressures and ambient oxygen concentrations for a range of droplet sizes varying between 2 and 5 mm. DCE used various fuels -- in drops ranging from 1 mm (0.04 inches) to 5 mm (0.2 inches) -- and mixtures of oxidizers and inert gases to learn more about the physics of combustion in the simplest burning configuration, a sphere. The experiment elapsed time is shown at the bottom of the composite image. The DCE principal investigator was Forman Williams, University of California, San Diego. The experiment was part of the space research investigations conducted during the Microgravity Science Laboratory-1R mission (STS-94, July 1-17 1997). Advanced combustion experiments will be a part of investigations plarned for the International Space Station. (121KB JPEG, 654 x 977 pixels; downlinked video, higher quality not available) The MPG from which this composite was made is available at http://mix.msfc.nasa.gov/ABSTRACTS/MSFC-0300169.html.

  14. Burning Fuel Droplet

    NASA Technical Reports Server (NTRS)

    2003-01-01

    Fuel ignites and burns in the Droplet Combustion Experiment (DCE) on STS-94 on July 4 1997, MET:2/05:40 (approximate). The DCE was designed to investigate the fundamental combustion aspects of single, isolated droplets under different pressures and ambient oxygen concentrations for a range of droplet sizes varying between 2 and 5 mm. DCE used various fuels -- in drops ranging from 1 mm (0.04 inches) to 5 mm (0.2 inches) -- and mixtures of oxidizers and inert gases to learn more about the physics of combustion in the simplest burning configuration, a sphere. The experiment elapsed time is shown at the bottom of the composite image. The DCE principal investigator was Forman Williams, University of California, San Diego. The experiment was part of the space research investigations conducted during the Microgravity Science Laboratory-1R mission (STS-94, July 1-17 1997). Advanced combustion experiments will be a part of investigations plarned for the International Space Station. (121KB JPEG, 654 x 977 pixels; downlinked video, higher quality not available) The MPG from which this composite was made is available at http://mix.msfc.nasa.gov/ABSTRACTS/MSFC-0300169.html.

  15. Fuel Droplet Burning During Droplet Combustion Experiment

    NASA Technical Reports Server (NTRS)

    2003-01-01

    Fuel ignites and burns in the Droplet Combustion Experiment (DCE) on STS-94 on July 4 1997, MET:2/05:40 (approximate). The DCE was designed to investigate the fundamental combustion aspects of single, isolated droplets under different pressures and ambient oxygen concentrations for a range of droplet sizes varying between 2 and 5 mm. DCE used various fuels -- in drops ranging from 1 mm (0.04 inches) to 5 mm (0.2 inches) -- and mixtures of oxidizers and inert gases to learn more about the physics of combustion in the simplest burning configuration, a sphere. The experiment elapsed time is shown at the bottom of the composite image. The DCE principal investigator was Forman Williams, University of California, San Diego. The experiment was part of the space research investigations conducted during the Microgravity Science Laboratory-1R mission (STS-94, July 1-17 1997). Advanced combustion experiments will be a part of investigations plarned for the International Space Station. (1.4MB, 13-second MPEG, screen 320 x 240 pixels; downlinked video, higher quality not available)A still JPG composite of this movie is available at http://mix.msfc.nasa.gov/ABSTRACTS/MSFC-0300168.html.

  16. Fuel Droplet Burning During Droplet Combustion Experiment

    NASA Technical Reports Server (NTRS)

    2003-01-01

    Fuel ignites and burns in the Droplet Combustion Experiment (DCE) on STS-94 on July 4 1997, MET:2/05:40 (approximate). The DCE was designed to investigate the fundamental combustion aspects of single, isolated droplets under different pressures and ambient oxygen concentrations for a range of droplet sizes varying between 2 and 5 mm. DCE used various fuels -- in drops ranging from 1 mm (0.04 inches) to 5 mm (0.2 inches) -- and mixtures of oxidizers and inert gases to learn more about the physics of combustion in the simplest burning configuration, a sphere. The experiment elapsed time is shown at the bottom of the composite image. The DCE principal investigator was Forman Williams, University of California, San Diego. The experiment was part of the space research investigations conducted during the Microgravity Science Laboratory-1R mission (STS-94, July 1-17 1997). Advanced combustion experiments will be a part of investigations plarned for the International Space Station. (1.4MB, 13-second MPEG, screen 320 x 240 pixels; downlinked video, higher quality not available)A still JPG composite of this movie is available at http://mix.msfc.nasa.gov/ABSTRACTS/MSFC-0300168.html.

  17. Investigation of critical burning of fuel droplets

    NASA Technical Reports Server (NTRS)

    Allison, C. B.; Canada, G. S.; Faeth, G. M.

    1972-01-01

    Measurements were made on the burning of liquid hydrazine, MMH, and UDMH in a combustion gas environment. The experimental range of these tests involved gas temperatures of 1660-2530 K, oxygen concentrations of 0-42% by mass and droplet diameters (employing both droplets and porous spheres) of 0.11-1.91 cm. at atmospheric pressure. A simplified hybrid combustion theory was developed which was found to correlate the present results as well as the experimental measurements of other investigators. Measurements were also made of the monopropellant strand burning rates and liquid surface temperatures of a number of nitrate ester fuels and hydrazine at elevated pressures. The temperature measurements for the nitrate esters were found to be in good agreement with a theoretical model which allowed for gas solubility in the liquid phase at high pressures. Experimental results were also obtained on the burning rates and liquid surface temperatures of a number of paraffin and alcohol fuels burning in air pressures up to 72 atm. For these tests, the fuels were burned from porous spheres in a natural convection environment. Initial findings on a pressurized flat flame burner are also described as well as the design of an oscillatory combustion apparatus to test the response of burning liquid fuels.

  18. 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.

  19. Thermocapillary Convection in Liquid Droplets

    NASA Technical Reports Server (NTRS)

    1986-01-01

    The purpose of this video is to understand the effects of surface tension on fluid convection. The fluid system chosen is the liquid sessile droplet to show the importance in single crystal growth, the spray drying and cooling of metal, and the advance droplet radiators of the space stations radiators. A cross sectional representation of a hemispherical liquid droplet under ideal conditions is used to show internal fluid motion. A direct simulation of buoyancy-dominant convection and surface tension-dominant convection is graphically displayed. The clear differences between two mechanisms of fluid transport, thermocapillary convection, and bouncy dominant convection is illustrated.

  20. 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.

  1. Transient burning of a convective fuel droplet

    SciTech Connect

    Wu, Guang; Sirignano, William A.

    2010-05-15

    The transient burning of an n-octane fuel droplet in a hot gas stream at 20 atmosphere pressure is numerically studied, with considerations of droplet regression, deceleration due to the drag of the droplet, internal circulation inside the droplet, variable properties, non-uniform surface temperature, and the effect of surface tension. An initial envelope flame is found to remain envelope in time, and an initial wake flame is always transitioned into an envelope flame at a later time, with the normalized transition delay controlled by the initial Reynolds number and the initial Damkohler number. The initial flame shape is primarily determined by the initial Damkohler number, which has a critical value of Da{sub 0}=1.02. The burning rates are modified by the transition, and are influenced by the intensity of forced convection which is determined by initial Reynolds number. The influence of surface tension is also studied as the surface temperature is non-uniform. Surface tension affects the liquid motion at the droplet surface significantly and affects the change of surface temperature and burning rate modestly. The influence of surface tension generally increases with increasing initial Reynolds number within the range without droplet breakup. We also studied cases with constant relative velocity between the air stream and the droplet. The results show that in these cases the initial envelope flame still remains envelope, but the evolution from an initial wake flame to an envelope flame is inhibited. Validation of our analysis is made by comparing with a published porous-sphere experiment Raghavan et al. (2005) which used methanol fuel. (author)

  2. Liquid droplet radiator development status

    NASA Technical Reports Server (NTRS)

    White, K. Alan, III

    1987-01-01

    Development of the Liquid Droplet Radiator (LDR) is described. Significant published results of previous investigators are presented, and work currently in progress is discussed. Several proposed LDR configurations are described, and the rectangular and triangular configurations currently of most interest are examined. Development of the droplet generator, collector, and auxiliary components are discussed. Radiative performance of a droplet sheet is considered, and experimental results are seen to be in very good agreement with analytical predictions. The collision of droplets in the droplet sheet, the charging of droplets by the space plasma, and the effect of atmospheric drag on the droplet sheet are shown to be of little consequence, or can be minimized by proper design. The LDR is seen to be less susceptible than conventional technology to the effects of micrometeoroids or hostile threats. The identification of working fluids which are stable in the orbital environments of interest is also made. Methods for reducing spacecraft contamination from an LDR to an acceptable level are discussed. Preliminary results of microgravity testing of the droplet generator are presented. Possible future NASA and Air Force missions enhanced or enabled by a LDR are also discussed. System studies indicate that the LDR is potentially less massive than heat pipe radiators. Planned microgravity testing aboard the Shuttle or space station is seen to be a logical next step in LDR development.

  3. The liquid droplet heat exchanger

    NASA Astrophysics Data System (ADS)

    Bruckner, A. P.

    Direct contact heat exchange between a gas and a molten metal dispersed into droplets offers an attractive new approach to increasing the efficiency and decreasing the specific weight of thermal power cycles for space applications. The ability of a droplet heat exchanger to transfer heat directly from a liquid metal to a working gas over a wide temperature range circumvents many of the material limitations of conventional tube type heat exchangers and does away with complicated plumbing systems and their tendency toward simple point failure. Droplet heat exchangers offer large surface to volume ratios in a compact geometry, very low pressure drop and high effectiveness. In the simplest configuration the molten material is sprayed axially through a counterflowing, high pressure inert working gas in an insulated cylindrical chamber. The droplets transfer heat directly to the gas by convection as they traverse the heat exchanger and are subsequently collected for recycling through the heat source. A number of suitable liquid metals and eutectic alloys having negligibly low vapor pressures in the temperature range of 350-1300 K were identified. Experimental studies of droplet formation with mercury demonstrated that near perfect control of droplet size can be easily achieved.

  4. Effects of Particle Additives on Acoustically Coupled Fuel Droplet Combustion

    NASA Astrophysics Data System (ADS)

    Sim, Hyung Sub; Plascencia Quiroz, Miguel; Vargas, Andres; Bennewitz, John; Smith, Owen; Karagozian, Ann

    2016-11-01

    Addition of nanoscale particulates to liquid hydrocarbon fuels is suggested to have numerous benefits for combustion systems, although aggregation of metal nanoparticles can produce deleterious effects. The present experiments explore the effect of nano Aluminum (nAl) additives on the combustion of single liquid fuel droplets, with and without exposure of the droplets to standing acoustic waves. Building on prior studies, the present experiments quantify variations in the burning rate constant K for ethanol droplets with increasing concentrations of nAl in a quiescent environment. Burning fuel droplets that are continuously fed via a capillary as well as suspended (non-fed) droplets are examined. Nano Al is observed to create ejections of both particles and vapor toward the end of the burning period for non-fed droplets; this phenomenon is delayed when the droplet is replenished via continuous fuel delivery. Yet for the majority of conditions explored, increasing concentrations of nAl tend to reduce K. When ethanol droplets with nAl are exposed to standing waves, acoustic perturbations appear to delay particulate agglomeration, sustaining combustion for a longer period of time and increasing K. Supported by AFOSR Grant FA9550-15-1-0339.

  5. 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.

  6. Investigation of critical burning of fuel droplets. [monopropellants

    NASA Technical Reports Server (NTRS)

    Faeth, G. M.; Chanin, S.

    1974-01-01

    The steady combustion characteristics of droplets were considered in combustion chamber environments at various pressures, flow conditions, and ambient oxidizer concentrations for a number of hydrocarbon fuels. Using data obtained earlier, predicted gasification rates were within + or - 30% of measurements when the correction for convection was based upon average properties between the liquid surface and the flame around the droplet. Analysis was also completed for the open loop response of monopropellant droplets, based upon earlier strand combustion results. At the limit of large droplets, where the effect of flame curvature is small, the results suggest sufficient response to provide a viable mechanism for combustion instability in the frequency and droplet size range appropriate to practical combustors. Calculations are still in progress for a broader range of droplet sizes, including conditions where active combustion effects are small.

  7. Vaporization and combustion of fuel droplets at supercritical conditions

    NASA Technical Reports Server (NTRS)

    Yang, Vigor

    1991-01-01

    Vaporization and combustion liquid-fuel droplets in both sub- and super-critical environments have been examined. The formulation is based on the complete conservation equations for both gas and liquid phases, and accommodates finite-rate chemical kinetics and a full treatment of liquid-vapor phase equilibrium at the droplet surface. The governing equations and the associated interface boundary conditions are solved numerically using a fully coupled, implicit scheme with the dual time-stepping integration technique. The model is capable of treating the entire droplet history, including the transition from the subcritical to the supercritical state. As a specific example, the combustion of n-pentane fuel droplets in air is studied for pressures of 5-140 atm. In addition, the dynamic responses of droplet vaporization and combustion to ambient-pressure oscillations are investigated. Results indicate that the droplet gasification and burning mechanisms depend greatly on the ambient pressure. In particular, a rapid enlargement of the vaporization and combustion responses occurs when the droplet surface reaches its critical point, mainly due to the strong variations of latent heat of vaporization and thermophysical properties at the critical state.

  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. Oscillatory combustion of liquid monopropellant droplets

    NASA Technical Reports Server (NTRS)

    Chanin, S. P.; Faeth, G. M.

    1976-01-01

    A theoretical investigation was conducted on the open-loop combustion response of monopropellant droplets and sprays to imposed pressure oscillations. The theoretical model was solved as a perturbation analysis through first order, yielding linear response results. Unsteady gas phase effects were considered in some cases, but the bulk of the calculations assumed a quasi-steady gas phase. Calculations were conducted using properties corresponding to hydrazine decomposition. Zero-order results agreed with earlier measurements of hydrazine droplet burning in combustion gases. The droplet response was greatest (exceeding unity in some cases) for large droplets with liquid phase temperature gradients; at frequencies near the characteristic frequency of the liquid phase thermal wave. The response of a spray is less than that of its largest droplet, however, a relatively small percentage of large droplets provides a substantial response (exceeding unity in some cases).

  10. Liquid Droplets on a Highly Deformable Membrane

    NASA Astrophysics Data System (ADS)

    Schulman, Rafael; Dalnoki-Veress, Kari

    2015-11-01

    We present measurements of the deformation produced by micro-droplets atop thin elastomeric and glassy free-standing films. Due to the Laplace pressure, the droplets deform the elastic membrane thereby forming a bulge. Thus, there are two angles that define the droplet/membrane geometry: the angle the liquid surface makes with the film and the angle the deformed bulge makes with the film. The contact line geometry is well captured by a Neumann construction which includes contributions from interfacial and mechanical tensions. Finally, we show that a droplet atop a film with biaxial tension assumes an equilibrium shape which is elongated along the axis of high tension.

  11. Coffee Stain Effect with Liquid Droplets

    NASA Astrophysics Data System (ADS)

    Mitra, Sushanta; Das, Siddhartha

    2012-11-01

    We discuss the dynamics of immiscible bidispersed oil droplets that are suspended in an evaporating water sessile drop. Therefore, in contrast to classical coffee stain problem, the depositing ``particles'' are replaced by microscopic oil droplets - hence, we discuss a liquid-droplet coffee stain phenomenon. We show experimentally that unlike colloidal particles in a classical coffee stain problem, liquid oil droplets cannot reach the three phase contact line (TPCL) due to the aversion of the oil droplets to form finite oil-air interface in water medium. Therefore, the oil droplets get positioned at a finite distance from the TPCL. We call this distance the ``enclosure'' distance, which being a function of the droplet size, triggers a spontaneous size-based oil droplet separation. In addition, the ``enclosure'' effect is a function of the surface energies of the oil droplet and the rate of evaporation. We develop a theory to describe this effect, and the results show excellent agreement with the experimental findings. NSERC Banting Postdoctoral Fellowship for S. Das.

  12. Pressure Effects in Droplet Combustion of Miscible Binary Fuels

    NASA Technical Reports Server (NTRS)

    Mikami, Masato; Habara, Osamu; Kono, Michikata; Sato, Jun-Ichi; Dietrich, Daniel L.; Williams, Forman A.

    1997-01-01

    The objective of this research is to improve understanding of the combustion of binary fuel mixtures in the vicinity of the critical point. Fiber-supported droplets of mixtures of n-heptane and n-hexadecane, initially 1 mm in diameter, were burned in room-temperature air at pressures from 1 MPa to 6 MPa under free-fall microgravity conditions. For most mixtures the total burning time was observed to achieve a minimum value at pressures well above the critical pressure of either of the pure fuels. This behavior is explained in terms of critical mixing conditions of a ternary system consisting of the two fuels and nitrogen. The importance of inert-gas dissolution in the liquid fuel near the critical point is thereby re-emphasized, and nonmonotonic dependence of dissolution on initial fuel composition is demonstrated. The results provide information that can be used to estimate high-pressure burning rates of fuel mixtures.

  13. Kinetics of complex plasma with liquid droplets

    NASA Astrophysics Data System (ADS)

    Misra, Shikha; Mishra, S. K.; Sodha, M. S.

    2013-12-01

    This paper provides a theoretical basis for the reduction of electron density by spray of water (or other liquids) in hot plasma. This phenomenon has been observed in a hypersonic flight experiment for relief of radio black out, caused by high ionization in the plasma sheath of a hypersonic vehicle, re-entering the atmosphere. The analysis incorporates a rather little known phenomenon for de-charging of the droplets, viz., evaporation of ions from the surface and includes the charge balance on the droplets and number cum energy balance of electrons, ions, and neutral molecules; the energy balance of the evaporating droplets has also been taken into account. The analysis has been applied to a realistic situation and the transient variations of the charge and radius of water droplets, and other plasma parameters have been obtained and discussed. The analysis through made in the context of water droplets is applicable to all liquids.

  14. Kinetics of complex plasma with liquid droplets

    SciTech Connect

    Misra, Shikha; Sodha, M. S.; Mishra, S. K.

    2013-12-15

    This paper provides a theoretical basis for the reduction of electron density by spray of water (or other liquids) in hot plasma. This phenomenon has been observed in a hypersonic flight experiment for relief of radio black out, caused by high ionization in the plasma sheath of a hypersonic vehicle, re-entering the atmosphere. The analysis incorporates a rather little known phenomenon for de-charging of the droplets, viz., evaporation of ions from the surface and includes the charge balance on the droplets and number cum energy balance of electrons, ions, and neutral molecules; the energy balance of the evaporating droplets has also been taken into account. The analysis has been applied to a realistic situation and the transient variations of the charge and radius of water droplets, and other plasma parameters have been obtained and discussed. The analysis through made in the context of water droplets is applicable to all liquids.

  15. How faceted liquid droplets grow tails

    PubMed Central

    Guttman, Shani; Sapir, Zvi; Schultz, Moty; Butenko, Alexander V.; Ocko, Benjamin M.; Deutsch, Moshe; Sloutskin, Eli

    2016-01-01

    Liquid droplets, widely encountered in everyday life, have no flat facets. Here we show that water-dispersed oil droplets can be reversibly temperature-tuned to icosahedral and other faceted shapes, hitherto unreported for liquid droplets. These shape changes are shown to originate in the interplay between interfacial tension and the elasticity of the droplet’s 2-nm-thick interfacial monolayer, which crystallizes at some T = Ts above the oil’s melting point, with the droplet’s bulk remaining liquid. Strikingly, at still-lower temperatures, this interfacial freezing (IF) effect also causes droplets to deform, split, and grow tails. Our findings provide deep insights into molecular-scale elasticity and allow formation of emulsions of tunable stability for directed self-assembly of complex-shaped particles and other future technologies. PMID:26733673

  16. Mechanical vibrations of pendant liquid droplets.

    PubMed

    Temperton, Robert H; Smith, Michael I; Sharp, James S

    2015-07-01

    A simple optical deflection technique was used to monitor the vibrations of microlitre pendant droplets of deuterium oxide, formamide, and 1,1,2,2-tetrabromoethane. Droplets of different volumes of each liquid were suspended from the end of a microlitre pipette and vibrated using a small puff of nitrogen gas. A laser was passed through the droplets and the scattered light was collected using a photodiode. Vibration of the droplets resulted in the motion of the scattered beam and time-dependent intensity variations were recorded using the photodiode. These time-dependent variations were Fourier transformed and the frequencies and widths of the mechanical droplet resonances were extracted. A simple model of vibrations in pendant/sessile drops was used to relate these parameters to the surface tension, density and viscosity of the liquid droplets. The surface tension values obtained from this method were found to be in good agreement with results obtained using the standard pendant drop technique. Damping of capillary waves on pendant drops was shown to be similar to that observed for deep liquid baths and the kinematic viscosities obtained were in agreement with literature values for all three liquids studied.

  17. Combustion of emulsified fuel droplets under microgravity

    NASA Astrophysics Data System (ADS)

    Okajima, S.; Kanno, H.; Kumagai, S.

    Single-droplet experiments have been conducted under a zero-gravity condition in a freely falling chamber as a fundamental step of study on the spray combustion of hydrocarbon-water emulsified fuels. Such a behavior as the secondary micro-atomization was observed by taking schlieren photographs with a 35-mm movie camera installed on the falling assembly. Under zero gravity the emulsion droplet initiates steam discharge and puffing—that is, a mild atomization—at a time from ignition, but it does not lead to such a micro-explosion or disruption as is experienced under normal gravity. The apparent burning rate constant under zero gravity is about 30% smaller than that under normal gravity. These facts suggest that the internal convection in emulsion droplets plays an important role in causing the micro-explosion.

  18. Vibrational modes of elongated sessile liquid droplets.

    PubMed

    Temperton, Robert H; Sharp, James S

    2013-04-16

    Vibrations of small (microliter) sessile liquid droplets were studied using a simple optical deflection technique. The droplets were made to elongate in one direction by taking advantage of the anisotropic wetting of the liquids on structured diffraction grating surfaces. They were vibrated by applying a puff of nitrogen gas. Motion of the droplets was monitored by scattering laser light from their surfaces. The scattered light was collected using a photodiode, and the resulting time-dependent intensity signals were Fourier-transformed to obtain the vibrational response of the drops. The vibrational spectra of elongated sessile drops were observed to contain two closely spaced peaks. A simple model that considers the frequency of capillary wave fluctuations on the surfaces of the drops was used to show that the vibrational frequencies of these peaks correspond to standing wave states that exist along the major and minor profile lengths of the droplets.

  19. Numerical Simulations of Droplet Dynamics in PEM Fuel Cell Microchannels

    NASA Astrophysics Data System (ADS)

    Cauble, Eric; Owkes, Mark

    2015-11-01

    Proton exchange membrane (PEM) fuel cells are of beneficial interest due to their capability of producing clean energy with zero emissions. An important design challenge hindering the performance of fuel cells is controlling water removal to maintain a hydrated membrane while avoiding excess water that may lead to channel blockage. Fuel cell water management requires a detailed knowledge of multiphase flow dynamics within microchannels. Direct observation of gas-liquid flows is difficult due to the small scale and viewing obstructions of the channels within the fuel cell. Instead, this work uses a CFD approach to compute the formation and dynamics of droplets in fuel cell channels. The method leverages a conservative volume-of-fluid (VOF) formulation coupled with a novel methodology to track dynamic contact angles. We present details of the numerical approach and simulation results relevant to water management in PEM fuel cells. In particular, it is shown that variation of the contact hysteresis angle influences the wetting properties of the droplet and significantly impacts water transport throughout the a fuel cell channel.

  20. Multiplexed electrospray scaling for liquid fuel injection

    NASA Astrophysics Data System (ADS)

    Waits, C. Mike; Hanrahan, Brendan; Lee, Ivan

    2010-10-01

    Evaporation and space-charge requirements are evaluated to understand the effect of device scaling and fuel preheating for a liquid fuel injector using a multiplexed electrospray (MES) configuration in compact combustion applications. This work reveals the influence of the droplet diameter, droplet velocity and droplet surface temperature as well as the surrounding gas temperature on the size and performance of microfabricated MES. Measurements from MES devices are used in the model to accurately account for the droplet diameter versus flow rate relationship, the minimum droplet diameter and the relevant droplet velocities. A maximum extractor electrode to ground electrode distance of 3.1 mm required to overcome space-charge forces is found to be independent of voltage or droplet velocity for large levels of multiplexing. This maximum distance also becomes the required evaporation length scale which imposes minimum fuel pre-heating requirements for large flow densities. Required fuel preheating is therefore evaluated for both ethanol and 1-butanol with combustor parameters relevant to fuel reformation, thermoelectric conversion, thermophotovoltaic conversion and thermionic conversion.

  1. Vitrification and levitation of a liquid droplet on liquid nitrogen.

    PubMed

    Song, Young S; Adler, Douglas; Xu, Feng; Kayaalp, Emre; Nureddin, Aida; Anchan, Raymond M; Maas, Richard L; Demirci, Utkan

    2010-03-09

    The vitrification of a liquid occurs when ice crystal formation is prevented in the cryogenic environment through ultrarapid cooling. In general, vitrification entails a large temperature difference between the liquid and its surrounding medium. In our droplet vitrification experiments, we observed that such vitrification events are accompanied by a Leidenfrost phenomenon, which impedes the heat transfer to cool the liquid, when the liquid droplet comes into direct contact with liquid nitrogen. This is distinct from the more generally observed Leidenfrost phenomenon that occurs when a liquid droplet is self-vaporized on a hot plate. In the case of rapid cooling, the phase transition from liquid to vitrified solid (i.e., vitrification) and the levitation of droplets on liquid nitrogen (i.e., Leidenfrost phenomenon) take place simultaneously. Here, we investigate these two simultaneous physical events by using a theoretical model containing three dimensionless parameters (i.e., Stefan, Biot, and Fourier numbers). We explain theoretically and observe experimentally a threshold droplet radius during the vitrification of a cryoprotectant droplet in the presence of the Leidenfrost effect.

  2. Vitrification and levitation of a liquid droplet on liquid nitrogen

    PubMed Central

    Song, Young S.; Adler, Douglas; Xu, Feng; Kayaalp, Emre; Nureddin, Aida; Anchan, Raymond M.; Maas, Richard L.; Demirci, Utkan

    2010-01-01

    The vitrification of a liquid occurs when ice crystal formation is prevented in the cryogenic environment through ultrarapid cooling. In general, vitrification entails a large temperature difference between the liquid and its surrounding medium. In our droplet vitrification experiments, we observed that such vitrification events are accompanied by a Leidenfrost phenomenon, which impedes the heat transfer to cool the liquid, when the liquid droplet comes into direct contact with liquid nitrogen. This is distinct from the more generally observed Leidenfrost phenomenon that occurs when a liquid droplet is self-vaporized on a hot plate. In the case of rapid cooling, the phase transition from liquid to vitrified solid (i.e., vitrification) and the levitation of droplets on liquid nitrogen (i.e., Leidenfrost phenomenon) take place simultaneously. Here, we investigate these two simultaneous physical events by using a theoretical model containing three dimensionless parameters (i.e., Stefan, Biot, and Fourier numbers). We explain theoretically and observe experimentally a threshold droplet radius during the vitrification of a cryoprotectant droplet in the presence of the Leidenfrost effect. PMID:20176969

  3. Development of comprehensive numerical schemes for predicting evaporating gas-droplets flow processes of a liquid-fueled combustor

    NASA Technical Reports Server (NTRS)

    Chen, C. P.

    1990-01-01

    An existing Computational Fluid Dynamics code for simulating complex turbulent flows inside a liquid rocket combustion chamber was validated and further developed. The Advanced Rocket Injector/Combustor Code (ARICC) is simplified and validated against benchmark flow situations for laminar and turbulent flows. The numerical method used in ARICC Code is re-examined for incompressible flow calculations. For turbulent flows, both the subgrid and the two equation k-epsilon turbulence models are studied. Cases tested include idealized Burger's equation in complex geometries and boundaries, a laminar pipe flow, a high Reynolds number turbulent flow, and a confined coaxial jet with recirculations. The accuracy of the algorithm is examined by comparing the numerical results with the analytical solutions as well as experimented data with different grid sizes.

  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. Fabrication of Janus droplets by evaporation driven liquid-liquid phase separation.

    PubMed

    Zhang, Qingquan; Xu, Meng; Liu, Xiaojun; Zhao, Wenfeng; Zong, Chenghua; Yu, Yang; Wang, Qi; Gai, Hongwei

    2016-04-11

    We present a universal and scalable method to fabricate Janus droplets based on evaporation driven liquid-liquid phase separation. In this work, the morphologies and chemical properties of separate parts of the Janus droplets can be flexibly regulated, and more complex Janus droplets (such as core-shell Janus droplets, ternary Janus droplets, and multiple Janus droplets) can be constructed easily.

  6. Impact of liquid droplets on granular media.

    PubMed

    Delon, G; Terwagne, D; Dorbolo, S; Vandewalle, N; Caps, H

    2011-10-01

    The crater formation due to the impact of a water droplet onto a granular bed has been experimentally investigated. Three parameters were tuned: the impact velocity, the size of the droplet, and the size of the grains. The aim is to determine the influence of the kinetic energy on the droplet pattern. The shape of the crater depends on the kinetic energy at the moment the droplet starts to impact the bed. The spreading and recession of the liquid during the impact were carefully analyzed from the dynamical point of view, using image analysis of high-speed video recordings. The different observed regimes are characterized by the balance between the impregnation time of the water by the granular bed by the water and the capillary time responsible for the recession of the drop.

  7. High Velocity Droplet Rebound On Liquid Pools

    NASA Astrophysics Data System (ADS)

    Doak, William; Laiacona, Danielle; Chiarot, Paul; German, Guy

    2015-11-01

    Rebound of high velocity, periodic droplet streams off viscous liquid pools is studied experimentally. Droplets, approximately 60 micrometers in diameter, impact the oil surface at velocities up to 13 m/s and at angles between 2-25 degrees. The oil surface does not degrade or lose its ability to provide rebound even after millions of droplet impacts. The oil was varied to examine the effect that surface tension and viscosity had on droplet rebound. Stable rebound is achievable on oils varying in dynamic viscosity in the range 13-970 Pa.s and surface tensions in the range 19-28 mN/m. When rebound occurs, a consistent 29% loss of droplet kinetic energy is observed. This is a surprising relationship due to the fact that it holds true for all cases of stable rebound regardless of the oil used. We further observe an upper inertial limit where droplets no longer provide stable rebound and instead become fully entrained in the oil pool. This limit is governed by the Rayleigh-Plateau instability and can be characterized and predicted using a modified version of the Weber number. The droplet rebound presented in this study is unique due to the size, velocity, and frequency of the droplets used. Another unique feature is that the rebound manifests itself as an effectively static phenomenon. No motion of the interface - oscillations, waves, or otherwise - was observed during rebound. The quasi-static nature of rebound enabled distinctions to be made regarding energy dissipation and the transition from droplet rebound to entrainment.

  8. Pyroelectric manipulation of liquid crystal droplets

    NASA Astrophysics Data System (ADS)

    Merola, F.; Grilli, S.; Coppola, S.; Vespini, V.; De Nicola, S.; Maddalena, P.; Carfagna, C.; Ferraro, P.

    2013-04-01

    Very interesting effects can be observed in maneuvering nematic liquid crystal (NLC) droplets onto functionalized polar lithium niobate (LN) crystal surfaces, covered with thin films of Polydimethylsiloxane (PDMS). It has been discovered that pyroelectric effect is able to drive a reversible fragmentation process in liquid crystal drops, starting from nanoliter drops and obtaining pico/femtoliter droplets. These small droplets are patterned according to the geometry of the substrate and aligned along the electric field lines. This novel approach for manipulating different classes of liquids by exploiting the pyroelectric effect, where the strong electric fields generated allow to manipulate liquids in 2D on a substrate or even in 3D, has been recently discovered and exploited for different purposes. In particular, manipulation of liquid crystals by a thermal stimulus could be suitable for applications such as spatial modulation of the wettability (i.e. wettability patterning), or, in principle, a dynamical optical element able to switch from a diffuser (fragmentation) state to a microlens array. Moreover, the biocompatibility of some kinds of nematic or cholesteric liquid crystals makes them suitable as biomaterials for applications in biology and tissue engineering.

  9. Detachment of Liquid-Water Droplets from Gas-Diffusion Layers

    SciTech Connect

    Das, Prodip K.; Grippin, Adam; Weber, Adam Z.

    2011-07-01

    A critical issue for optimal water management in proton-exchange-membrane fuel cells at lower temperatures is the removal of liquid water from the cell. This pathway is intimately linked with the phenomena of liquid-water droplet removal from surface of the gas-diffusion layer and into the flow channel. Thus, a good understanding of liquid-water transport and droplet growth and detachment from the gas-diffusion layer is critical. In this study, liquid-water droplet growth and detachment on the gas-diffusion layer surfaces are investigated experimentally to improve the understating of water transport through and removal from gas-diffusion layers. An experiment using a sliding-angle measurement is designed and used to quantify and directly measure the adhesion force for liquid-water droplets, and to understand the droplets? growth and detachment from the gas-diffusion layers.

  10. Nonspherical liquid droplet falling in air

    NASA Astrophysics Data System (ADS)

    Agrawal, Meenu; Premlata, A. R.; Tripathi, Manoj Kumar; Karri, Badarinath; Sahu, Kirti Chandra

    2017-03-01

    The dynamics of an initially nonspherical liquid droplet falling in air under the action of gravity is investigated via three-dimensional numerical simulations of the Navier-Stokes and continuity equations in the inertial regime. The surface tension is considered to be high enough so that a droplet does not undergo breakup. Vertically symmetric oscillations which decay with time are observed for low inertia. The amplitude of these oscillations increases for high Gallilei numbers and the shape asymmetry in the vertical direction becomes prominent. The reason for this asymmetry has been attributed to the higher aerodynamic inertia. Moreover, even for large inertia, no path deviations or oscillations are observed.

  11. Optical vortices from liquid crystal droplets.

    PubMed

    Brasselet, Etienne; Murazawa, Naoki; Misawa, Hiroaki; Juodkazis, Saulius

    2009-09-04

    We report on the generation of mono- and polychromatic optical phase singularities from micron-sized birefringent droplets. This is done experimentally by using liquid crystal droplets whose three dimensional architecture of the optical axis is controlled within the bulk by surfactant agents. Because of its microscopic size these optical vortex generators are optically trapped and manipulated at will, thus realizing a robust self-aligned micro-optical device for orbital angular momentum conversion. Experimental observations are supported by a simple model of optical spin-orbit coupling in uniaxial dielectrics that emphasizes the prominent role of the transverse optical anisotropy with respect to the beam propagation direction.

  12. Gold metal liquid-like droplets.

    PubMed

    Smirnov, Evgeny; Scanlon, Micheál D; Momotenko, Dmitry; Vrubel, Heron; Méndez, Manuel A; Brevet, Pierre-Francois; Girault, Hubert H

    2014-09-23

    Simple methods to self-assemble coatings and films encompassing nanoparticles are highly desirable in many practical scenarios, yet scarcely any examples of simple, robust approaches to coat macroscopic droplets with continuous, thick (multilayer), reflective and stable liquid nanoparticle films exist. Here, we introduce a facile and rapid one-step route to form films of reflective liquid-like gold that encase macroscopic droplets, and we denote these as gold metal liquid-like droplets (MeLLDs). The present approach takes advantage of the inherent self-assembly of gold nanoparticles at liquid-liquid interfaces and the increase in rates of nanoparticle aggregate trapping at the interface during emulsification. The ease of displacement of the stabilizing citrate ligands by appropriate redox active molecules that act as a lubricating molecular glue is key. Specifically, the heterogeneous interaction of citrate stabilized aqueous gold nanoparticles with the lipophilic electron donor tetrathiafulvalene under emulsified conditions produces gold MeLLDs. This methodology relies exclusively on electrochemical reactions, i.e., the oxidation of tetrathiafulvalene to its radical cation by the gold nanoparticle, and electrostatic interactions between the radical cation and nanoparticles. The gold MeLLDs are reversibly deformable upon compression and decompression and kinetically stable for extended periods of time in excess of a year.

  13. Structural Transitions in Cholesteric Liquid Crystal Droplets

    SciTech Connect

    Zhou, Ye; Bukusoglu, Emre; Martínez-González, José A.; Rahimi, Mohammad; Roberts, Tyler F.; Zhang, Rui; Wang, Xiaoguang; Abbott, Nicholas L.; de Pablo, Juan J.

    2016-07-26

    Confinement of cholesteric liquid crystals (ChLC) into droplets leads to a delicate interplay between elasticity, chirality, and surface energy. In this work, we rely on a combination of theory and experiments to understand the rich morphological behavior that arises from that balance. More specifically, a systematic study of micrometer-sized ChLC droplets is presented as a function of chirality and surface energy (or anchoring). With increasing chirality, a continuous transition is observed from a twisted bipolar structure to a radial spherical structure, all within a narrow range of chirality. During such a transition, a bent structure is predicted by simulations and confirmed by experimental observations. Simulations are also able to capture the dynamics of the quenching process observed in experiments. Consistent with published work, it is found that nanoparticles are attracted to defect regions on the surface of the droplets. For weak anchoring conditions at the nanoparticle surface, ChLC droplets adopt a morphology similar to that of the equilibrium helical phase observed for ChLCs in the bulk. As the anchoring strength increases, a planar bipolar structure arises, followed by a morphological transition to a bent structure. The influence of chirality and surface interactions are discussed in the context of the potential use of ChLC droplets as stimuli-responsive materials for reporting molecular adsorbates.

  14. Simulation of sliding of liquid droplets

    NASA Astrophysics Data System (ADS)

    Alen, Saif Khan; Farhat, Nazia; Rahman, Md. Ashiqur

    2016-07-01

    Numerical simulations of sliding behavior of liquid droplets on flat and periodic microgrooved surfaces with a range of groove geometry are conducted. A numerical model is developed which is capable of predicting the critical sliding angle of the drop by comparing the advancing and the receding angles obtained from numerical and experimental findings. The effect of microgroove topography, droplet size and inclination angle on the droplet sliding characteristics is analysed. Using an open-source platform (Surface Evolver), a 3D drop-shape model is developed to numerically determine the drop stability and contact angle hysteresis on tilted surfaces. In this numerical model, the three phase contact line of the drop is obtained by numerically calculating the vertex force and local contact angle at each vertex of the base contour. Several numerical models are developed based on various assumptions of base contour shape (circular or elliptical) and implementation of gravitational force to the droplet. Droplet shapes and critical sliding angles, obtained from these numerical models, are compared with those of experimental results and are found to be in very good agreement.

  15. The measurement of droplet temperature using thermochromic liquid crystals

    SciTech Connect

    Peterson, D.; Hu, S.H.; Richards, C.D.; Richards, R.F.

    1995-12-31

    A noninvasive technique to determine the temperature of droplets in flight is under development. The technique involves atomizing droplets of neat thermochromic liquid crystals and then inferring the droplet temperatures form the liquid crystals` color-play. Previous work has shown the feasibility of atomizing the neat liquid crystal. The present work reports results of a calibration of the temperature response of 200 to 300 micron droplets of neat liquid crystal. The calibration is accomplished by suspending droplets of the neat liquid crystal on a microthermocouple within a controlled temperature environment. The droplet is imaged using a long-distance microscope, an RGB video camera, and a frame grabber. Images of the droplet are acquired and digitized to quantify changes in RGB values (color) with temperature. The RGB information is transformed into hue, saturation, intensity (HSI) space to relate hue, H, to temperature. The temperature of the droplet is measured directly with the micro-thermocouple.

  16. Physics of puffing and microexplosion of emulsion fuel droplets

    NASA Astrophysics Data System (ADS)

    Shinjo, J.; Xia, J.; Ganippa, L. C.; Megaritis, A.

    2014-10-01

    The physics of water-in-oil emulsion droplet microexplosion/puffing has been investigated using high-fidelity interface-capturing simulation. Varying the dispersed-phase (water) sub-droplet size/location and the initiation location of explosive boiling (bubble formation), the droplet breakup processes have been well revealed. The bubble growth leads to local and partial breakup of the parent oil droplet, i.e., puffing. The water sub-droplet size and location determine the after-puffing dynamics. The boiling surface of the water sub-droplet is unstable and evolves further. Finally, the sub-droplet is wrapped by boiled water vapor and detaches itself from the parent oil droplet. When the water sub-droplet is small, the detachment is quick, and the oil droplet breakup is limited. When it is large and initially located toward the parent droplet center, the droplet breakup is more extensive. For microexplosion triggered by the simultaneous growth of multiple separate bubbles, each explosion is local and independent initially, but their mutual interactions occur at a later stage. The degree of breakup can be larger due to interactions among multiple explosions. These findings suggest that controlling microexplosion/puffing is possible in a fuel spray, if the emulsion-fuel blend and the ambient flow conditions such as heating are properly designed. The current study also gives us an insight into modeling the puffing and microexplosion of emulsion droplets and sprays.

  17. A frictional sliding algorithm for liquid droplets

    NASA Astrophysics Data System (ADS)

    Sauer, Roger A.

    2016-12-01

    This work presents a new frictional sliding algorithm for liquid menisci in contact with solid substrates. In contrast to solid-solid contact, the liquid-solid contact behavior is governed by the contact line, where a contact angle forms and undergoes hysteresis. The new algorithm admits arbitrary meniscus shapes and arbitrary substrate roughness, heterogeneity and compliance. It is discussed and analyzed in the context of droplet contact, but it also applies to liquid films and solids with surface tension. The droplet is modeled as a stabilized membrane enclosing an incompressible medium. The contact formulation is considered rate-independent such that hydrostatic conditions apply. Three distinct contact algorithms are needed to describe the cases of frictionless surface contact, frictionless line contact and frictional line contact. For the latter, a predictor-corrector algorithm is proposed in order to enforce the contact conditions at the contact line and thus distinguish between the cases of advancing, pinning and receding. The algorithms are discretized within a monolithic finite element formulation. Several numerical examples are presented to illustrate the numerical and physical behavior of sliding droplets.

  18. Liquid fuel cells.

    PubMed

    Soloveichik, Grigorii L

    2014-01-01

    The advantages of liquid fuel cells (LFCs) over conventional hydrogen-oxygen fuel cells include a higher theoretical energy density and efficiency, a more convenient handling of the streams, and enhanced safety. This review focuses on the use of different types of organic fuels as an anode material for LFCs. An overview of the current state of the art and recent trends in the development of LFC and the challenges of their practical implementation are presented.

  19. Liquid fuel cells

    PubMed Central

    2014-01-01

    Summary The advantages of liquid fuel cells (LFCs) over conventional hydrogen–oxygen fuel cells include a higher theoretical energy density and efficiency, a more convenient handling of the streams, and enhanced safety. This review focuses on the use of different types of organic fuels as an anode material for LFCs. An overview of the current state of the art and recent trends in the development of LFC and the challenges of their practical implementation are presented. PMID:25247123

  20. Relaxation of liquid bridge after droplets coalescence

    NASA Astrophysics Data System (ADS)

    Zheng, Jiangen; Shi, Haiyang; Chen, Guo; Huang, Yingzhou; Wei, Hua; Wang, Shuxia; Wen, Weijia

    2016-11-01

    We investigate the relaxation of liquid bridge after the coalescence of two sessile droplets resting on an organic glass substrate both experimentally and theoretically. The liquid bridge is found to relax to its equilibrium shape via two distinct approaches: damped oscillation relaxation and underdamped relaxation. When the viscosity is low, damped oscillation shows up, in this approach, the liquid bridge undergoes a damped oscillation process until it reaches its stable shape. However, if the viscous effects become significant, underdamped relaxation occurs. In this case, the liquid bridge relaxes to its equilibrium state in a non-periodic decay mode. In depth analysis indicates that the damping rate and oscillation period of damped oscillation are related to an inertial-capillary time scale τc. These experimental results are also testified by our numerical simulations with COMSOL Multiphysics.

  1. 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.

  2. The liquid droplet radiator in space: A parametric approach

    NASA Astrophysics Data System (ADS)

    Buckner, Gerald L.; Tuttle, Ronald F.

    The Liquid Droplet Radiator (LDR) consists of a column or sheet of liquid droplets moving through space from a droplet generator to a collector. The droplets carry the waste heat generated by a space power system and radiate this waste heat directly to space during their flight. The liquid droplets are collected at a lower temperature, reheated and pumped to the generator and reused to remove waste heat from the thermodynamic power cycle. A parametric analysis is given of a cylindrical LDR to estimate its performance and operating characteristics using a new pump specific mass term.

  3. 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

  4. Lipid-induced structural turnover of water droplets to liquid crystal droplets

    NASA Astrophysics Data System (ADS)

    Sidiq, Sumyra; Pal, Santanu Kumar

    2014-04-01

    For the first time direct observation of structural turnover of water droplets to liquid crystal (LC) droplets with radial LC ordering was observed in presence of surfactants and lipids. Study of interactions between enzymes with the topological defects in the LC mediate the response of these droplets suggesting new principles for the design of chemical and biological sensors.

  5. Dynamic interactions of Leidenfrost droplets on liquid metal surface

    NASA Astrophysics Data System (ADS)

    Ding, Yujie; Liu, Jing

    2016-09-01

    Leidenfrost dynamic interaction effects of the isopentane droplets on the surface of heated liquid metal were disclosed. Unlike conventional rigid metal, such conductive and deformable liquid metal surface enables the levitating droplets to demonstrate rather abundant and complex dynamics. The Leidenfrost droplets at different diameters present diverse morphologies and behaviors like rotation and oscillation. Depending on the distance between the evaporating droplets, they attract and repulse each other through the curved surfaces beneath them and their vapor flows. With high boiling point up to 2000 °C, liquid metal offers a unique platform for testing the evaporating properties of a wide variety of liquid even solid.

  6. Fuel droplet burning rates at high pressures.

    NASA Technical Reports Server (NTRS)

    Canada, G. S.; Faeth, G. M.

    1973-01-01

    Combustion of methanol, ethanol, propanol-1, n-pentane, n-heptane, and n-decane was observed in air under natural convection conditions, at pressures up to 100 atm. The droplets were simulated by porous spheres, with diameters in the range from 0.63 to 1.90 cm. The pressure levels of the tests were high enough so that near-critical combustion was observed for methanol and ethanol. Due to the high pressures, the phase-equilibrium models of the analysis included both the conventional low-pressure approach as well as high-pressure versions, allowing for real gas effects and the solubility of combustion-product gases in the liquid phase. The burning-rate predictions of the various theories were similar, and in fair agreement with the data. The high-pressure theory gave the best prediction for the liquid-surface temperatures of ethanol and propanol-1 at high pressure. The experiments indicated the approach of critical burning conditions for methanol and ethanol at pressures on the order of 80 to 100 atm, which was in good agreement with the predictions of both the low- and high-pressure analysis.

  7. 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.

  8. Dynamic behaviors of liquid droplets on a gas diffusion layer surface: Hybrid lattice Boltzmann investigation

    NASA Astrophysics Data System (ADS)

    Wu, Jie; Huang, Jun-Jie

    2015-07-01

    Water management is one of the key issues in proton exchange membrane fuel cells. Fundamentally, it is related to dynamic behaviors of droplets on a gas diffusion layer (GDL) surface, and consequently they are investigated in this work. A two-dimensional hybrid method is employed to implement numerical simulations, in which the flow field is solved by using the lattice Boltzmann method and the interface between droplet and gas is captured by solving the Cahn-Hilliard equation directly. One or two liquid droplets are initially placed on the GDL surface of a gas channel, which is driven by the fully developed Poiseuille flow. At a fixed channel size, the effects of viscosity ratio of droplet to gas ( μ ∗ ), Capillary number (Ca, ratio of gas viscosity to surface tension), and droplet interaction on the dynamic behaviors of droplets are systematically studied. By decreasing viscosity ratio or increasing Capillary number, the single droplet can detach from the GDL surface easily. On the other hand, when two identical droplets stay close to each other or a larger droplet is placed in front of a smaller droplet, the removal of two droplets is promoted.

  9. Superhydrophobic-like tunable droplet bouncing on slippery liquid interfaces.

    PubMed

    Hao, Chonglei; Li, Jing; Liu, Yuan; Zhou, Xiaofeng; Liu, Yahua; Liu, Rong; Che, Lufeng; Zhou, Wenzhong; Sun, Dong; Li, Lawrence; Xu, Lei; Wang, Zuankai

    2015-08-07

    Droplet impacting on solid or liquid interfaces is a ubiquitous phenomenon in nature. Although complete rebound of droplets is widely observed on superhydrophobic surfaces, the bouncing of droplets on liquid is usually vulnerable due to easy collapse of entrapped air pocket underneath the impinging droplet. Here, we report a superhydrophobic-like bouncing regime on thin liquid film, characterized by the contact time, the spreading dynamics, and the restitution coefficient independent of underlying liquid film. Through experimental exploration and theoretical analysis, we demonstrate that the manifestation of such a superhydrophobic-like bouncing necessitates an intricate interplay between the Weber number, the thickness and viscosity of liquid film. Such insights allow us to tune the droplet behaviours in a well-controlled fashion. We anticipate that the combination of superhydrophobic-like bouncing with inherent advantages of emerging slippery liquid interfaces will find a wide range of applications.

  10. Superhydrophobic-like tunable droplet bouncing on slippery liquid interfaces

    PubMed Central

    Hao, Chonglei; Li, Jing; Liu, Yuan; Zhou, Xiaofeng; Liu, Yahua; Liu, Rong; Che, Lufeng; Zhou, Wenzhong; Sun, Dong; Li, Lawrence; Xu, Lei; Wang, Zuankai

    2015-01-01

    Droplet impacting on solid or liquid interfaces is a ubiquitous phenomenon in nature. Although complete rebound of droplets is widely observed on superhydrophobic surfaces, the bouncing of droplets on liquid is usually vulnerable due to easy collapse of entrapped air pocket underneath the impinging droplet. Here, we report a superhydrophobic-like bouncing regime on thin liquid film, characterized by the contact time, the spreading dynamics, and the restitution coefficient independent of underlying liquid film. Through experimental exploration and theoretical analysis, we demonstrate that the manifestation of such a superhydrophobic-like bouncing necessitates an intricate interplay between the Weber number, the thickness and viscosity of liquid film. Such insights allow us to tune the droplet behaviours in a well-controlled fashion. We anticipate that the combination of superhydrophobic-like bouncing with inherent advantages of emerging slippery liquid interfaces will find a wide range of applications. PMID:26250403

  11. Superhydrophobic-like tunable droplet bouncing on slippery liquid interfaces

    NASA Astrophysics Data System (ADS)

    Hao, Chonglei; Wang, Zuankai

    2015-11-01

    Droplet impacting on solid or liquid interfaces is a ubiquitous phenomenon in nature. Although complete rebound of droplets is widely observed on superhydrophobic surfaces, the bouncing of droplets on liquid is usually vulnerable due to easy collapse of entrapped air pocket underneath the impinging droplet. Here, we report a superhydrophobic-like bouncing regime on thin liquid film, characterized by the contact time, the spreading dynamics, and the restitution coefficient independent of underlying liquid film. Through experimental exploration and theoretical analysis, we demonstrate that the manifestation of such a superhydrophobic-like bouncing necessitates an intricate interplay between the Weber number, the thickness and viscosity of liquid film. Such insights allow us to tune the droplet behaviors in a well-controlled fashion. We anticipate that the combination of superhydrophobic-like bouncing with inherent advantages of emerging slippery liquid interfaces will find a wide range of applications.

  12. Superhydrophobic-like tunable droplet bouncing on slippery liquid interfaces

    NASA Astrophysics Data System (ADS)

    Hao, Chonglei; Li, Jing; Liu, Yuan; Zhou, Xiaofeng; Liu, Yahua; Liu, Rong; Che, Lufeng; Zhou, Wenzhong; Sun, Dong; Li, Lawrence; Xu, Lei; Wang, Zuankai

    2015-08-01

    Droplet impacting on solid or liquid interfaces is a ubiquitous phenomenon in nature. Although complete rebound of droplets is widely observed on superhydrophobic surfaces, the bouncing of droplets on liquid is usually vulnerable due to easy collapse of entrapped air pocket underneath the impinging droplet. Here, we report a superhydrophobic-like bouncing regime on thin liquid film, characterized by the contact time, the spreading dynamics, and the restitution coefficient independent of underlying liquid film. Through experimental exploration and theoretical analysis, we demonstrate that the manifestation of such a superhydrophobic-like bouncing necessitates an intricate interplay between the Weber number, the thickness and viscosity of liquid film. Such insights allow us to tune the droplet behaviours in a well-controlled fashion. We anticipate that the combination of superhydrophobic-like bouncing with inherent advantages of emerging slippery liquid interfaces will find a wide range of applications.

  13. Experimental Study of Unsupported Nonane fuel Droplet Combustion in Microgravity

    NASA Technical Reports Server (NTRS)

    Callahan, B. J.; Avedisian, C. T.; Hertzog, D. E.; Berkery, J. W.

    1999-01-01

    Soot formation in droplet flames is the basic component of the particulate emission process that occurs in spray combustion. The complexity of soot formation motivates a one-dimensional transport condition which has obvious advantages in modeling. Recent models of spherically symmetric droplet combustion have made this assumption when incorporating such aspects as detailed chemistry and radiation. Interestingly, spherical symmetry does not necessarily restrict the results because it has been observed that the properties of carbon formed in flames are not strongly affected by the nature of the fuel or flaming configuration. What is affected, however, are the forces acting on the soot aggregates and where they are trapped by a balance of drag and thermophoretic forces. The distribution of these forces depends on the transport conditions of the flame. Prior studies of spherical droplet flames have examined the droplet burning history of alkanes, alcohols and aromatics. Data are typically the evolution of droplet, flame, extinction, and soot shell diameters. These data are only now just beginning to find their way into comprehensive numerical models of droplet combustion to test proposed oxidation schemes for fuels such as methanol and heptane. In the present study, we report new measurements on the burning history of unsupported nonane droplets in a convection-free environment to promote spherical symmetry. The far-field gas is atmospheric pressure air at room temperature. The evolution of droplet diameter was measured using high speed cine photography of a spark-ignited, droplet within a confined volume in a drop tower. The initial droplet diameters varied between 0.5 mm and 0.6 mm. The challenge of unsupported droplets is to form, deploy and ignite them with minimal disturbance, and then to keep them in the camera field of view. Because of the difficulty of this undertaking, more sophisticated diagnostics for studying soot than photographic were not used. Supporting

  14. Nontoxic Ionic Liquid Fuels for Exploration Applications

    NASA Technical Reports Server (NTRS)

    Coil, Millicent

    2015-01-01

    The toxicity of propellants used in conventional propulsion systems increases not only safety risks to personnel but also costs, due to special handling required during the entire lifetime of the propellants. Orbital Technologies Corporation (ORBITEC) has developed and tested novel nontoxic ionic liquid fuels for propulsion applications. In Phase I of the project, the company demonstrated the feasibility of several ionic liquid formulations that equaled the performance of conventional rocket propellant monomethylhydrazine (MMH) and also provided low volatility and low toxicity. In Phase II, ORBITEC refined the formulations, conducted material property tests, and investigated combustion behavior in droplet and microreactor experiments. The company also explored the effect of injector design on performance and demonstrated the fuels in a small-scale thruster. The ultimate goal is to replace propellants such as MMH with fuels that are simultaneously high-performance and nontoxic. The fuels will have uses in NASA's propulsion applications and also in a range of military and commercial functions.

  15. Soot formation in synthetic-fuel droplets. First quarterly technical progress report

    SciTech Connect

    England, G.; Kramlich, J.; Payne, R.

    1981-01-01

    The objective of this project is to provide detailed information on methods of minimizing soot formation during synthetic liquid fuel combustion under conditions which minimize fuel nitrogen conversion to nitric oxide. The program consists of two tasks. The purpose of the first task, Fuel Screening Studies, is to investigate the impact of fuel properties on particulate production, to establish the importance of droplet size and examine atomizer effects, and to develop techniques for surrogate fuels productions. In the second task, Flame Studies, the fundamental details of soot formation from synfuel droplet combustion will be investigated in variable slip velocity configurations. This present report describes technical progress during the first three months of the program effort (October-December 1980). During this initial period, attention has focused on the definition of the different experimental efforts and on the design and construction of the required hardware. Aspects of this work are discussed.

  16. Helical motion of chiral liquid crystal droplets

    NASA Astrophysics Data System (ADS)

    Yamamoto, Takaki; Sano, Masaki

    Artificial swimmers have been intensively studied to understand the mechanism of the locomotion and collective behaviors of cells and microorganisms. Among them, most of the artificial swimmers are designed to move along the straight path. However, in biological systems, chiral dynamics such as circular and helical motion are quite common because of the chirality of their bodies, which are made of chiral biomolecules. To understand the role of the chirality in the physics of microswimmers, we designed chiral artificial swimmers and the theoretical model for the chiral motion. We found that chiral liquid crystal droplets, when dispersed in surfactant solutions, swim in the helical path induced by the Marangoni effect. We will discuss the mechanism of the helical motion with our phenomenological model. This work is supported by Grant-in-Aid for JSPS Fellows (Grant No. 26.9814), and MEXT KAKENHI Grant No. 25103004.

  17. Liquid Fuels Systems Maintenance

    DTIC Science & Technology

    1992-10-01

    DEFENSE INFO SCHOOL 1 1 DEFENSE TECHNICAL INFORMATION CENTER 2 DET 1, HQ AFMWRA/MWHBR 1 HSD/DPI 1 1 HQ AFCESA/DMG 1 1 HQ ACC/DPATD 3 3 HQ AFSPACECOM...ENGINEERING 0 WATTS MUESCO 11 FUEL METERS MAINTAINED IST ENL A.O. SMITH 81 BENNET 6 BOWSER 13 BRODIE 50 GRANCO 19 LIQUID CONTROL 38 NEPTUNE 19 CAL

  18. Segregation of immiscible liquids: From droplet size to plutonic scale

    NASA Astrophysics Data System (ADS)

    Zhang, Z.; Wu, B.; Wang, T.; Hui, H.

    2016-12-01

    Silicate liquid immiscibility has been evidenced as discrete glassy droplets in volcanic rocks microscopically. Furthermore, this process has been proposed to have resulted in mafic and felsic fractions on outcrop scale in plutons. However, it is unclear how tiny discrete immiscible liquid droplets could be segregated from a continuous melt (medium) and lead to magmatic differentiation on a chamber scale. The settling of immiscible liquid droplets depends on their sinking (or floating) velocities, which could be described using the Stokes' law. The discrete liquid droplets during settling could collide and coalesce with each other, resulting in larger droplets, which is different from the collision of crystals in the magma. The coalescence can significantly increase the droplet velocities, which are proportional to the square of the droplet radii according to the Stokes' law. In a slow-cooling magma chamber, the exsolution and settling of the discrete liquid droplets may reach "equilibrium", which here we call the steady state. Numerical analyses using population dynamics equations have been carried out to study how physical properties of melts affect the segregation of immiscible liquids at the steady state. Our preliminary results indicate that the residence time (average time it takes for discrete droplets to settle) of discrete melt with viscosity higher than that of the medium could be longer than that of discrete melt with viscosity lower than that of the medium, by even more than one order of magnitude. Furthermore, the residence time is approximately proportional to the square root of the medium viscosity, inversely proportional to the square root of the density difference and inversely proportional to the exsolution rate if the discrete melt is exsolved as initially small droplets ( 10 µm in radius). This study could shed light on understanding the feasibility of formation of plutons through liquid immiscibility in dynamics.

  19. Stimulated Heterogeneous Nucleation of Supercooled Liquid H2 Droplets

    NASA Astrophysics Data System (ADS)

    Knuth, E. L.; Schaper, S.; Toennies, J. P.

    2000-07-01

    The properties of H(2) droplets formed by condensation in a supersonic freejet were probed by the capture and coagulation of CO molecules for the purpose of determining whether the droplets are liquid or solid. The CO was introduced into the H(2) droplets by passing the droplet beam through a scattering chamber containing CO at room temperature and various pressures. Reduction of droplet size as a result of droplet collisions with CO molecules was determined by measuring the droplet size downstream from the scattering region for several different values of the CO pressure. The size of the embedded clusters formed by coagulation of the captured CO molecules was determined from the mass spectra measured for several values of CO pressure in the scattering chamber. A comparison of (a) the observed dramatic loss of about 7% of the H(2) molecules from a droplet after between 2 and 8 collisions with (b) the loss predicted due to evaporation/sublimation in the event of solidification is taken to be compelling evidence that the H(2) droplets were liquid prior to their collisions with the CO scattering gas. The observed dependence of the maximum CO cluster size on the collision frequency appears to indicate that a sufficiently high collision frequency will liquify a droplet which otherwise would be solid. This observation supports the conclusion that the H(2) droplets are solidified as a consequence of heterogeneous nucleation induced by the captured CO molecules. The evidence in favor of a liquid state. coupled with the estimated 4K droplet temperature, suggest strongly that the supercooled H(2) droplets are superfluid.

  20. Stimulated heterogeneous nucleation of supercooled liquid H2 droplets

    NASA Astrophysics Data System (ADS)

    Knuth, E. L.; Schaper, S.; Toennies, J. P.

    2001-08-01

    The properties of H2 droplets formed by condensation in a supersonic freejet were probed by the capture and coagulation of CO molecules for the purpose of determining whether the droplets are liquid or solid. The CO was introduced into the H2 droplets by passing the droplet beam through a scattering chamber containing CO at room temperature and various pressures. Reduction of droplet size as a result of droplet collisions with CO molecules was determined by measuring the droplet size downstream from the scattering region for several different values of the CO pressure. The size of the embedded clusters formed by coagulation of the captured CO molecules was determined from the mass spectra measured for several values of CO pressure in the scattering chamber. A comparison of (a) the observed dramatic loss of about 7% of the H2 molecules from a droplet after between 2 and 8 collisions with (b) the loss predicted due to evaporation/sublimation in the event of solidification is taken to be compelling evidence that the H2 droplets were liquid prior to their collisions with the CO scattering gas. The observed dependence of the maximum CO cluster size on the collision frequency appears to indicate that a sufficiently high collision frequency will liquify a droplet which otherwise would be solid. This observation supports the conclusion that the H2 droplets are solidified as a consequence of heterogeneous nucleation induced by the captured CO molecules. The evidence in favor of a liquid state, coupled with the estimated 4K droplet temperature, suggest strongly that the supercooled H2 droplets are superfluid.

  1. Periodic Partial Extinction Regime in Acoustically Coupled Fuel Droplet Combustion

    NASA Astrophysics Data System (ADS)

    Plascencia Quiroz, Miguel; Bennewitz, John; Vargas, Andres; Sim, Hyung Sub; Smith, Owen; Karagozian, Ann

    2016-11-01

    This experimental study investigates the response of burning liquid fuel droplets exposed to standing acoustic waves, extending prior studies quantifying mean and temporal flame response to moderate acoustic excitation. This investigation explores alternative fuels exposed to a range of acoustic forcing conditions (frequencies and amplitudes), with a focus on ethanol and JP-8. Three fundamental flame regimes are observed: sustained oscillatory combustion, periodic partial extinction and reignition (PPER), and full extinction. Phase-locked OH* chemiluminescence imaging and local temporal pressure measurements allow quantification of the combustion-acoustic coupling through the local Rayleigh index G. As expected, PPER produces negative G values, despite having clear flame oscillations. PPER is observed to occur at low-frequency, high amplitude excitation, where the acoustic time scales are large compared with kinetic/reaction times scales for diffusion-limited combustion processes. These quantitative differences in behavior are determined to depend on localized fluid mechanical strain created by the acoustic excitation as well as reaction kinetics. Supported by AFOSR Grant FA9550-15-1-0339.

  2. Precursors to splashing of liquid droplets on a solid surface.

    PubMed

    Mandre, Shreyas; Mani, Madhav; Brenner, Michael P

    2009-04-03

    A high velocity impact between a liquid droplet and a solid surface produces a splash. Classical work traced the origin of the splash to a thin sheet of fluid ejected near the impact point. Mechanisms of sheet formation have heretofore relied on initial contact of the droplet and the surface. We demonstrate that, neglecting intermolecular forces between the liquid and the solid, the liquid does not contact the solid, and instead spreads on a very thin air film. The interface of the droplet develops a high curvature and emits capillary waves.

  3. Levitation-free vibrated droplets: resonant oscillations of liquid marbles.

    PubMed

    McHale, G; Elliott, S J; Newton, M I; Herbertson, D L; Esmer, K

    2009-01-06

    A spherical conducting droplet in an alternating electric field is known to undergo shape oscillations. When the droplet is supported by a substrate, the shape is no longer a complete sphere, but shape resonances are still observed. To obtain a completely spherical droplet, some kind of levitation is needed, unless the droplet is in microgravity, and this has previously been provided by gas films or magnetic or other external forces. In this work, we report observations of shape oscillations of a hydrophobic-powder-coated droplet of water. A droplet of water rolled on a hydrophobic powder self-coats such that the water becomes encapsulated as a liquid marble. When the powder is a spherical hydrophobic grain with a contact angle greater than 90 degrees , it adheres to the solid-water interface with more than half of its diameter projecting from the liquid, thus ensuring the encapsulated water does not come into contact with any substrate. These liquid marbles are highly mobile and can be regarded as completely nonwetting droplets possessing contact angles of 180 degrees . In this work, we show that they also provide a new mechanism equivalent to levitating droplets and provide droplets with small contact areas and completely mobile contact lines for studies of shape oscillations. Liquid marbles were created using hydrophobic lycopodium and droplets of water containing potassium chloride and were excited into motion using an electrowetting-on-dielectric configuration with applied frequency swept from 1 to 250 Hz. Both an up-and-down motion and an oscillation involving multiple nodes were observed and recorded using a high-speed camera. The resonant oscillation modes of small liquid marbles were fitted to the theory for vibrations of a free spherical volume of fluid. This work demonstrates the principle that oscillation modes of completely nonwetting droplets can be studied using a simple powder coating approach without the need for an active mechanism for levitation.

  4. The Role of Liquid Properties on Lifetime of Levitated Droplets.

    PubMed

    Davanlou, Ashkan

    2016-09-27

    It is known that the temperature difference between a droplet and a liquid surface can extend the levitation time of that droplet by providing a thin air film between the surface and the droplet. However, the effect of fluid properties, liquid surface velocity, and air film thickness on the lifetime of droplets is still not well understood. Also, there is inconsistency in the literature about the role of vapor pressure in noncoalescence. Here we test a variety of liquids including silicone oil, Fluorinert, and water to understand the effect of surface tension, density ratio, viscosity, and heat capacity on the lifetime of a droplet. Droplets with larger heat capacity and vapor pressure like water remain floating for a longer time compared to oils. Similarly, higher surface velocity, which is seen in low viscous liquids, helps the air to replenish into the interstices beneath droplet and delay the drainage process. We also discuss the air film variation with temperature manipulation, and propose a correlation for the minimum thickness required to balance the droplet weight.

  5. Liquid droplet radiator program at the NASA Lewis Research Center

    NASA Technical Reports Server (NTRS)

    Presler, A. F.; Coles, C. E.; Diem-Kirsop, P. S.; White, K. A., III

    1985-01-01

    The NASA Lewis Research Center and the Air Force Rocket Propulsion Laboratory (AFRPL) are jointly engaged in a program for technical assessment of the Liquid Droplet Radiator (LDR) concept as an advanced high performance heat ejection component for future space missions. NASA Lewis has responsibility for the technology needed for the droplet generator, for working fluid qualification, and for investigating the physics of droplets in space; NASA Lewis is also conducting systems/mission analyses for potential LDR applications with candidate space power systems. For the droplet generator technology task, both micro-orifice fabrication techniques and droplet stream formation processes have been experimentally investigated. High quality micro-orifices (to 50 micron diameter) are routinely fabricated with automated equipment. Droplet formation studies have established operating boundaries for the generation of controlled and uniform droplet streams. A test rig is currently being installed for the experimental verification, under simulated space conditions, of droplet radiation heat transfer performance analyses and the determination of the effect radiative emissivity of multiple droplet streams. Initial testing has begun in the NASA Lewis Zero-Gravity Facility for investigating droplet stream behavior in microgravity conditions. This includes the effect of orifice wetting on jet dynamics and droplet formation. Results for both Brayton and Stirling power cycles have identified favorable mass and size comparisons of the LDR with conventional radiator concepts.

  6. LIQUID HYDROCARBON FUEL CELL DEVELOPMENT.

    DTIC Science & Technology

    A compound anode consists of a reforming catalyst bed in direct contact with a palladium-silver fuel cell anode. The objective of this study was to...prove the feasibility of operating a compound anode fuel cell on a liquid hydrocarbon and to define the important parameters that influence cell...performance. Both reformer and fuel cell tests were conducted with various liquid hydrocarbon fuels. Included in this report is a description of the

  7. Liquid droplet radiators for heat rejection in space

    NASA Technical Reports Server (NTRS)

    Mattick, A. T.; Hertzberg, A.

    1980-01-01

    A radiator for heat rejection in space is described which utilizes a stream of liquid droplets to radiate waste heat. The large surface area per mass makes the liquid droplet radiator at least an order of magnitude lighter than tube and fin radiators. Generation and collection of the droplets, as well as heat transfer to the liquid, can be achieved with modest extensions of conventional technology. Low vapor pressure liquids are available which cover a radiating temperature range 250-1000 K with negligible evaporation losses. The droplet radiator may be employed for a wide range of heat rejection applications in space. Three applications - heat rejection for a high temperature Rankine cycle, cooling of photovoltaic cells, and low temperature heat rejection for refrigeration in space illustrate the versatility of the radiator.

  8. Droplet impact on liquid films in the presence of surfactants

    NASA Astrophysics Data System (ADS)

    Jais, Khadijah; Yip, Natalie; Che, Zhizhao; Matar, Omar

    2016-11-01

    In this study of droplet impact on liquid films, surfactants are added to the droplet, the liquid film or both, and the effects of different surfactant concentrations are investigated using high-speed imaging. The results show that surfactants suppress partial coalescence, due to damping of the capillary waves. Rebounding occurs more frequently when surfactants are added, as the surfactant molecules resist the drainage of the intervening air layer. When the droplet deforms the surfactant film, there is an uneven distribution of surfactant molecules along the interface, resulting in a surface tension gradient and a Marangoni stress. The Marangoni stress acts to even out the surface tension gradient and to aid rebounding. Surfactant droplet ruptures the film with a much lower surfactant concentration, leaving an apparent dry region on the substrate at the impact point. This is likely due to Marangoni stresses where the film pulls the droplet apart. As the film thickness is increased, a Worthington jet is formed, with secondary droplet(s) ejected from the jet only when surfactants are present. This study reveals that the presence of surfactants can significantly alter the impact process of droplets on liquid films. EPSRC UK Programme Grant MEMPHIS (EP/K003976/1).

  9. Droplets on liquids and their journey into equilibrium.

    PubMed

    Bommer, Stefan; Cartellier, Florian; Jachalski, Sebastian; Peschka, Dirk; Seemann, Ralf; Wagner, Barbara

    2013-08-01

    The morphological path of droplets on a liquid substrate towards equilibrium is investigated experimentally and theoretically. The droplets emerge in the late stage of a dewetting process of short chained polystyrene (PS) dewetting from liquid polymethyl-methacrylate (PMMA). The three-dimensional droplet profiles are obtained experimentally by combining the in situ imaged PS/air interface during equilibration and the ex situ imaged PS/PMMA interface after removal of the PS by a selective solvent. Numerically the transient drop shapes are calculated by solving the thin-film equation in lubrication approximation using the experimentally determined input parameter like viscosity, film thickness and surface tensions. The numerically obtained droplet morphologies and time scales agree very well with the experimental drop shapes. An unexpected observation is that droplets with identical volumes synchronise their motion and become independent of the initial geometry long time before equilibrium is reached.

  10. Secondary atomization of single coal-water fuel droplets

    SciTech Connect

    Hassel, G.R.; Scaroni, A.W.

    1989-03-01

    The evaporative behavior of single, well characterized droplets of a lignite coal-water slurry fuel (CWSF) and a carbon black in water slurry was studied as a function of heating rate and droplet composition. Induced droplet heating rates were varied from 0 to 10{sup 5} K/s. Droplets studied were between 97 and 170 {mu}m in diameter, with compositions ranging from 25 to 60% solids by weight. The effect of a commercially available surfactant additive package on droplet evaporation rate, explosive boiling energy requirements, and agglomerate formation was assessed. Surfactant concentrations were varied from none to 2 and 4% by weight solution (1.7 and 3.6% by weight of active species on a dry coal basis). The experimental system incorporated an electrodynamic balance to hold single, free droplets, a counterpropagating pulsed laser heating arrangement, and both video and high speed cinematographic recording systems. Data were obtained for ambient droplet evaporation by monitoring the temporal size, weight, and solids concentration changes. 49 refs., 31 figs.

  11. Low-voltage droplet manipulation using liquid dielectrophoresis on electret

    NASA Astrophysics Data System (ADS)

    Wu, Tianzhun; Suzuki, Yuji; Kasagi, Nobuhide

    2010-08-01

    In order to make droplet-based digital microfluidics really 'digital' and compatible with standard integrated chips (ICs), a novel low-voltage droplet manipulation method named 'liquid dielectrophoresis on electret (L-DEPOE)' is proposed for dielectric liquids, which initializes the possibility of digital microfluidics for IC control and broad consumer electronic applications. By employing electret as a virtual voltage source embedded into microfluidics for the first time, a dielectric droplet between two electrodes can be transported by liquid dielectrophoresis (L-DEP) force when switching an external capacitor between electrodes using a manual switch or low-voltage-driven relays. A circuit model and force analysis for L-DEPOE are established to clarify its working principle and quantitatively depict the droplet motion. Nanoliter dielectric droplets have been transported reversibly between the two electrodes with a manual switch or five DCV-driven relays in microfabricated proof-of-concept prototypes. The surface voltage stability of electret in liquid is examined with different polymer materials and coatings. Furthermore, the droplet motion traces in a L-DEPOE device are compared with numerical simulation results, indicating the important role of contact angle hysteresis for nanoliter droplets.

  12. Fabrication of hemispherical liquid encapsulated structures based on droplet molding

    NASA Astrophysics Data System (ADS)

    Ishizuka, Hiroki; Miki, Norihisa

    2015-12-01

    We have developed and demonstrated a method for forming spherical structures of a thin polydimethylsiloxane (PDMS) membrane encapsulating a liquid. Liquid encapsulation can enhance the performance of microelectromechanical systems (MEMS) devices by providing deformability and improved dielectric properties. Parylene deposition and wafer bonding are applied to encapsulate liquid into a MEMS device. In parylene deposition, a parylene membrane is directly formed onto a liquid droplet. However, since the parylene membrane is stiff, the membrane is fragile. Although wafer bonding can encapsulate liquid between two substrates, the surface of the fabricated structure is normally flat. We propose a new liquid encapsulation method by dispensing liquid droplets. At first, a 20 μl PDMS droplet is dispensed on ethylene glycol. A 70 μl glycerin droplet is dispensed into a PDMS casting solution layer. The droplet forms a layer on heated ethylene glycol. Glycerin and ethylene glycol are chosen for their high boiling points. Additionally, a glycerin droplet is dispensed on the layer and surrounded by a thin PDMS casting solution film. The film is baked for 1 h at 75 °C. As the result, a structure encapsulating a liquid in a flexible PDMS membrane is obtained. We investigate the effects of the volume, surface tension, and guide thickness on the shape of the formed structures. We also evaluated the effect of the structure diameter on miniaturization. The structure can be adapted for various functions by changing the encapsulated liquid. We fabricated a stiffness-tunable structure by dispensing a magnetorheoligical fluid droplet with a stiffness that can be changed by an external magnetic field. We also confirmed that the proposed structure can produce stiffness differences that are distinguishable by humans.

  13. Liquid Droplet Dynamics in Gravity Compensating High Magnetic Field

    NASA Technical Reports Server (NTRS)

    Bojarevics, V.; Easter, S.; Pericleous, K.

    2012-01-01

    Numerical models are used to investigate behavior of liquid droplets suspended in high DC magnetic fields of various configurations providing microgravity-like conditions. Using a DC field it is possible to create conditions with laminar viscosity and heat transfer to measure viscosity, surface tension, electrical and thermal conductivities, and heat capacity of a liquid sample. The oscillations in a high DC magnetic field are quite different for an electrically conducting droplet, like liquid silicon or metal. The droplet behavior in a high magnetic field is the subject of investigation in this paper. At the high values of magnetic field some oscillation modes are damped quickly, while others are modified with a considerable shift of the oscillating droplet frequencies and the damping constants from the non-magnetic case.

  14. Mechanical vibration of viscoelastic liquid droplets

    NASA Astrophysics Data System (ADS)

    Sharp, James; Harrold, Victoria

    2014-03-01

    The resonant vibrations of viscoelastic sessile droplets supported on different substrates were monitored using a simple laser light scattering technique. In these experiments, laser light was reflected from the surfaces of droplets of high Mw poly acrylamide-co-acrylic acid (PAA) dissolved in water. The scattered light was allowed to fall on the surface of a photodiode detector and a mechanical impulse was applied to the drops using a vibration motor mounted beneath the substrates. The mechanical impulse caused the droplets to vibrate and the scattered light moved across the surface of the photodiode. The resulting time dependent photodiode signal was then Fourier transformed to obtain the mechanical vibrational spectra of the droplets. The frequencies and widths of the resonant peaks were extracted for droplets containing different concentrations of PAA and with a range of sizes. This was repeated for PAA loaded water drops on surfaces which displayed different values of the three phase contact angle. The results were compared to a simple model of droplet vibration which considers the formation of standing wave states on the surface of a viscoelastic droplet. We gratefully acknowledge the support of the Leverhulme trust under grant number RPG-2012-702.

  15. Dynamics of Non-Newtonian Liquid Droplet Collision

    NASA Astrophysics Data System (ADS)

    Chen, Xiaodong; Yang, Vigor

    2012-11-01

    Collision of Newtonian liquid droplets has been extensively investigated both experimentally and numerically for decades. Limited information, however, is available about non-Newtonian droplet collision dynamics. In the present work, high-fidelity numerical simulations were performed to study the situation associated with shear-thinning non-Newtonian liquids. The formulation is based on a complete set of conservation equations for the liquid and the surrounding gas phases. An improved volume-of-fluid (VOF) method, combined with an innovative topology-oriented adaptive mesh refinement (TOAMR) technique, was developed and implemented to track the interfacial dynamics. The complex evolution of the droplet surface over a broad range of length scales was treated accurately and efficiently. In particular, the thin gas film between two approaching droplets and subsequent breakup of liquid threads were well-resolved. Various types of droplet collision were obtained, including coalescence, bouncing, and reflexive and stretching separations. A regime diagram was developed and compared with that for Newtonian liquids. Fundamental mechanisms and key parameters that dictate droplet behaviors were identified. In addition, collision-induced atomization was addressed. This work was sponsored by the U.S. Army Research Office under the Multi-University Research Initiative under contract No. W911NF-08-1-0124. The support and encouragement provided by Dr. Ralph Anthenien are gratefully acknowledged.

  16. Retreating behavior of a charged ionic liquid droplet in a dielectric liquid under electric field

    NASA Astrophysics Data System (ADS)

    Ahn, Myung Mo; Im, Do Jin; Kang, In Seok

    2013-11-01

    Ionic liquids show great promise as excellent solvents or catalysts in energy and biological fields due to their unique chemical and physical properties. The ionic liquid droplets in microfluidic systems can also be used as a potential platform for chemical biological reactions. In order to control electrically the ionic liquid droplets in a microfluidic device, the charging characteristics of ionic liquid droplets need to be understood. In this work, the charging characteristics of various ionic liquids are investigated by using the parallel plate electrodes system. Under normal situation, a charged droplet shows bouncing motion between electrodes continuously. However, for some special ionic liquids, interesting retreating behavior of charged ionic liquid droplet has been observed. This retreating behavior of ionic liquid droplet has been analyzed experimentally by the image analysis and the electrometer signal analysis. Based on the hypothesis of charge leakage of the retreating ionic liquid droplets, FT-IR spectroscopy analysis has also been performed. The retreating behavior of ionic liquid droplet is discussed from the intermolecular point of view according to the species of ionic liquids. This research was supported by grant No. 2013R1A1A2011956 funded by the Ministry of Science, ICT and Future Planning (MSIP) and by grant No. 2013R1A1A2010483 funded by the Ministry of Education, Science and Technology (MEST) through the NRF.

  17. Automatic Circulation Control of Working Fluid in Liquid Droplet Radiator

    NASA Astrophysics Data System (ADS)

    Totani, Tsuyoshi; Takekoshi, Takuhiro; Wakita, Masashi; Nagata, Harunori

    Liquid Droplet Radiator (LDR) is an important candidate for disposing large quantities of waste heat more than 1 MW which will be handled by large space structures such as Space Power Satellite. The working fluid is heated through a heat exchanger by the waste heat generated in a large structure in space. Then, the working fluid is emitted in space through nozzles of the droplet generator toward a droplet collector as multiple streams of droplets. During the flight in space, the droplets lose thermal energy via radiative heat transfer. After the cooled droplets are captured by the droplet collector, the working fluid is recycled to the heat exchanger by a circulating pump. The automatic control system on the circulation of working fluid in a liquid droplet radiator has been built using a programmable logic controller. The proportional control of flow rate with the term of the variation of the counter flow in the gear pump and the relaxation of the change of an target flow rate has succeeded within 5 percent at the automatic circulation control of the working fluid from 100 ml/min to 200 ml/min and from 200 ml/min to 100 ml/min.

  18. Liquid DEP actuation and precision dispensing of variable volume droplets.

    PubMed

    Prakash, Ravi; Paul, Reginald; Kaler, Karan V I S

    2010-11-21

    Droplet based microfluidic systems, in recent years, have demonstrated numerous advantages and exciting potential for Lab-On-a Chip applications. In order to fully realize the potential benefits of this technology, one requires precision dispensing and manipulation of droplets of known volume and sample concentration, in a rapid and controlled manner. In this article, we demonstrate the rapid and controlled microactuation of aqueous samples and subsequent dispensing of variable volume droplets in nanolitre to picolitre regime by using a coplanar tapered electrode structure that leverages the phenomena of liquid dielectrophoresis (L-DEP). The transient behavior of the tapered liquid jet departs significantly from that of a uniform liquid jet case and is not adequately explained in terms of a simplified lumped capacitance model as in the case of the uniform jet, during the L-DEP actuation. A more generalized numerical model is developed for the tapered actuation scheme to account for the experimental observations. We furthermore demonstrate that the density of the dispensed droplets can be proactively controlled by the judicious placement of electrode bumps and pinches in the electrode structure thus overcoming the limitations imposed by Rayleigh's instability criterion. The proposed droplet dispensing schemes are superior to existing L-DEP based dispensing schemes which are restricted in size and spacing of the dispensed droplets by Rayleigh's instability criteria and furthermore mostly restricted to equi-volume droplets.

  19. Investigation of water droplet dynamics in PEM fuel cell gas channels

    NASA Astrophysics Data System (ADS)

    Gopalan, Preethi

    Water management in Proton Exchange Membrane Fuel Cell (PEMFC) has remained one of the most important issues that need to be addressed before its commercialization in automotive applications. Accumulation of water on the gas diffusion layer (GDL) surface in a PEMFC introduces a barrier for transport of reactant gases through the GDL to the catalyst layer. Despite the fact that the channel geometry is one of the key design parameters of a fluidic system, very limited research is available to study the effect of microchannel geometry on the two-phase flow structure. In this study, the droplet-wall dynamics and two-phase pressure drop across the water droplet present in a typical PEMFC channel, were examined in auto-competitive gas channel designs (0.4 x 0.7 mm channel cross section). The liquid water flow pattern inside the gas channel was analyzed for different air velocities. Experimental data was analyzed using the Concus-Finn condition to determine the wettability characteristics in the corner region. It was confirmed that the channel angle along with the air velocity and the channel material influences the water distribution and holdup within the channel. Dynamic contact angle emerged as an important parameter in controlling the droplet-wall interaction. Experiments were also performed to understand how the inlet location of the liquid droplet on the GDL surface affects the droplet dynamic behavior in the system. It was found that droplets emerging near the channel wall or under the land lead to corner filling of the channel. Improvements in the channel design has been proposed based on the artificial channel roughness created to act as capillary grooves to transport the liquid water away from the land area. For droplets emerging near the center of the channel, beside the filling and no-filling behavior reported in the literature, a new droplet jumping behavior was observed. As droplets grew and touched the sidewalls, they jumped off to the sidewall leaving the

  20. Marangoni instability induced convection in an evaporating liquid droplet

    NASA Technical Reports Server (NTRS)

    Chai, An-Ti; Rashidnia, N.; Arpaci, V. S.

    1992-01-01

    The processes occurring when a liquid drop undergoes evaporation are described. When a liquid drop undergoes evaporation, its surface temperature decreases. If the droplet is free floating in a microgravity environment, the heat transfer process inside the droplet is initially condition controlled. As the process continues, a radial temperature gradient builds up at the free surface until the critical Marangoni number is exceeded. Then the onset of instability induces thermocapillary convective flows, which in turn speed up the evaporation. The convective flows will subside when the interior of the droplet reaches a certain equilibrium temperature, and the process will return to the diffusion controlled mode. Both preliminary modeling and recent laboratory data have confirmed that Marangoni instability induced convection can and does occur in the droplet evaporation process. Mathematical models representing Marangoni instability in an evaporating liquid drop are presented. An ideal space experiment to study and characterize the onset of Marangoni instability in an evaporating liquid droplet and to establish the effect of Marangoni instability induced convection on the droplet evaporation rate is outlined and the need for conducting such experiments in space is highlighted. However, before an opportunity to conduct experiments in space arises, ground based experiments have to be conducted to study feasibility issues and proof of concept. A ground based experiment of this type is outlined.

  1. Active Mesogenic Droplets: Impact of Liquid Crystallinity and Collective Behavior

    NASA Astrophysics Data System (ADS)

    Bahr, Christian

    Droplets of common mesogenic compounds show a self-propelled motion when immersed in aqueous solutions containing ionic surfactants at concentrations well above the critical micelle concentration. After introducing some general properties of this type of artificial microswimmer, we focus on two topics: the influence of liquid crystallinity on the swimming behavior and the collective behavior of ensembles of a larger number of droplets. The mesogenic properties are not essential for the basic mechanism of self-propulsion, nevertheless they considerably influence the swimming behavior of the droplets. For instance, the shape of the trajectories strongly depends on whether the droplets are in the nematic or isotropic state. The droplet swimmers are also ideally suited for the study of collective behavior: Microfluidics enables the generation of large numbers of identical swimmers and we can tune their buoyancy. We report on the collective behavior in three-dimensional environments. Supported by the Deutsche Forschungsgemeinschaft (SPP 1726 ``Microswimmers'').

  2. Thermophoretic transport of ionic liquid droplets in carbon nanotubes.

    PubMed

    Rajegowda, Rakesh; Kannam, Sridhar Kumar; Hartkamp, Remco; Sathian, Sarith P

    2017-04-18

    Thermal-gradient induced transport of ionic liquid (IL) and water droplets through a carbon nanotube (CNT) is investigated in this study using molecular dynamics simulations. Energetic analysis indicates that IL transport through a CNT is driven primarily by the fluid-solid interaction, while fluid-fluid interactions dominate in water-CNT systems. Droplet diffusion analysis via the moment scaling spectrum reveals sub-diffusive motion of the IL droplet, in contrast to the self-diffusive motion of the water droplet. The Soret coefficient and energetic analysis of the systems suggest that the CNT shows more affinity for interaction with IL than with the water droplet. Thermophoretic transport of IL is shown to be feasible, which can create new opportunities in nanofluidic applications.

  3. Thermophoretic transport of ionic liquid droplets in carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Rajegowda, Rakesh; Kannam, Sridhar Kumar; Hartkamp, Remco; Sathian, Sarith P.

    2017-04-01

    Thermal-gradient induced transport of ionic liquid (IL) and water droplets through a carbon nanotube (CNT) is investigated in this study using molecular dynamics simulations. Energetic analysis indicates that IL transport through a CNT is driven primarily by the fluid-solid interaction, while fluid-fluid interactions dominate in water-CNT systems. Droplet diffusion analysis via the moment scaling spectrum reveals sub-diffusive motion of the IL droplet, in contrast to the self-diffusive motion of the water droplet. The Soret coefficient and energetic analysis of the systems suggest that the CNT shows more affinity for interaction with IL than with the water droplet. Thermophoretic transport of IL is shown to be feasible, which can create new opportunities in nanofluidic applications.

  4. Movement of liquid droplets containing polymers on substrate

    NASA Astrophysics Data System (ADS)

    Hu, Guohui; Wang, Heng

    2016-11-01

    It is of both fundamental and practical interests to study the flow physics in the manipulation of droplets. As a microreactor, the macromolecules or particles inside the droplets might have significant influences on their movement. In the present study, the many-body dissipative particle dynamics (MDPD) is utilized to investigate the translocation of droplets containing polymer on a substrate driven by the wettability gradient, where the polymer is modelled as worm-like chain (WLC). The internal flows of the droplets are analyzed, as well as the comparison to the polymer-free moving droplets. The effects of physical parameters, such as the interaction potential between liquid particle and polymer beads, the mass of the beads, on the translocation speed are also addressed in the present study. These results might be helpful to the optimization in design of the microfluidic systems.

  5. Soot formation in synthetic-fuel droplets. Second quarterly technical progress report

    SciTech Connect

    England, G.; Kramlich, J.; Payne, R.

    1981-04-01

    The main objective of this program is to provide detailed information on methods of minimizing soot formation during synthetic liquid fuel combustion under conditions which minimize the formation of nitric oxides. The program comprises two main tasks, Fuel Screening Studies, and Flame Studies. The purpose of the first task is to investigate the impact of fuel properties on particulate production, to establish the importance of droplet size and examine atomizer effects, and to develop techniques for surrogate fuels production. In the second task, fundamental details of soot formation from synfuel droplet combustion will be investigated in variable slip velocity configurations. This report describes technical progress during the second three-month period of program effort (January-March 1981). During this period attention has continued to be focussed on the design, construction and commissioning of experimental systems. The Task 1 tunnel furnace modification was completed and made operational, and some preliminary fuel screening studies were carried out. Similarly, construction of the controlled flow droplet reactor was completed and efforts directed towards the design and testing of diagnostic systems. Details of this work are discussed.

  6. Nano Liquid Crystal Droplet Impact on Solid Surfaces

    NASA Astrophysics Data System (ADS)

    Zhang, Rui; de Pablo, Juan; dePablo Team

    2015-03-01

    Liquid droplet impaction on solid surfaces is an important problem with a wide range of applications in everyday life. Liquid crystals (LCs) are anisotropic liquids whose internal structure gives rise to rich optical and morphological phenomena. In this work we study the liquid crystal droplet impaction on solid surfaces by molecular dynamics simulations. We employ a widely used Gay-Berne model to describe the elongated liquid crystal molecules and their interactions. Our work shows that, in contrast to isotropic liquids, drop deformation is symmetric unless an instability kicks in, in which case a nano scale liquid crystal droplet exhibits distinct anisotropic spreading modes that do not occur in simple liquids. The drop prefers spreading along the low viscosity direction, but inertia can in some cases overcome that bias. The effects of the director field of the droplet, preferred anchoring direction and the anchoring strength of the wall are investigated. Large scale (0.1 micron) simulations are performed to connect our nano scale results to the experiments. Our studies indicate that LCs could provide an interesting alternative for development of next-generation printing inks.

  7. 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.

  8. A realistic model of evaporation for a liquid droplet

    NASA Technical Reports Server (NTRS)

    Chai, An-Ti; Arpaci, V. S.

    1994-01-01

    An intuitive delineation along with dimensional considerations and experimental evidences are presented to show that in a general case, the evaporation of a liquid droplet undergoes three regimes through the process. Initially, the heat transfer inside the evaporating droplets is conduction controlled; then, in the second stage, convective heat transfer may take over; finally, the convections subside, and the process returns to conduction controlled mode.

  9. Mechano-regulated surface for manipulating liquid droplets

    NASA Astrophysics Data System (ADS)

    Tang, Xin; Zhu, Pingan; Tian, Ye; Zhou, Xuechang; Kong, Tiantian; Wang, Liqiu

    2017-04-01

    The effective transfer of tiny liquid droplets is vital for a number of processes such as chemical and biological microassays. Inspired by the tarsi of meniscus-climbing insects, which can climb menisci by deforming the water/air interface, we developed a mechano-regulated surface consisting of a background mesh and a movable microfibre array with contrastive wettability. The adhesion of this mechano-regulated surface to liquid droplets can be reversibly switched through mechanical reconfiguration of the microfibre array. The adhesive force can be tuned by varying the number and surface chemistry of the microfibres. The in situ adhesion of the mechano-regulated surface can be used to manoeuvre micro-/nanolitre liquid droplets in a nearly loss-free manner. The mechano-regulated surface can be scaled up to handle multiple droplets in parallel. Our approach offers a miniaturized mechano-device with switchable adhesion for handling micro-/nanolitre droplets, either in air or in a fluid that is immiscible with the droplets.

  10. Ecodesign of Liquid Fuel Tanks

    NASA Astrophysics Data System (ADS)

    Gicevska, Jana; Bazbauers, Gatis; Repele, Mara

    2011-01-01

    The subject of the study is a 10 litre liquid fuel tank made of metal and used for fuel storage and transportation. The study dealt with separate life cycle stages of this product, compared environmental impacts of similar fuel tanks made of metal and plastic, as well as analysed the product's end-of-life cycle stage, studying the waste treatment and disposal scenarios. The aim of this study was to find opportunities for improvement and to develop proposals for the ecodesign of 10 litre liquid fuel tank.

  11. MEASUREMENTS AND COMPUTATIONS OF FUEL DROPLET TRANSPORT IN TURBULENT FLOWS

    SciTech Connect

    Joseph Katz and Omar Knio

    2007-01-10

    The objective of this project is to study the dynamics of fuel droplets in turbulent water flows. The results are essential for development of models capable of predicting the dispersion of slightly light/heavy droplets in isotropic turbulence. Since we presently do not have any experimental data on turbulent diffusion of droplets, existing mixing models have no physical foundations. Such fundamental knowledge is essential for understanding/modeling the environmental problems associated with water-fuel mixing, and/or industrial processes involving mixing of immiscible fluids. The project has had experimental and numerical components: 1. The experimental part of the project has had two components. The first involves measurements of the lift and drag forces acting on a droplet being entrained by a vortex. The experiments and data analysis associated with this phase are still in progress, and the facility, constructed specifically for this project is described in Section 3. In the second and main part, measurements of fuel droplet dispersion rates have been performed in a special facility with controlled isotropic turbulence. As discussed in detail in Section 2, quantifying and modeling the of droplet dispersion rate requires measurements of their three dimensional trajectories in turbulent flows. To obtain the required data, we have introduced a new technique - high-speed, digital Holographic Particle Image Velocimetry (HPIV). The technique, experimental setup and results are presented in Section 2. Further information is available in Gopalan et al. (2005, 2006). 2. The objectives of the numerical part are: (1) to develop a computational code that combines DNS of isotropic turbulence with Lagrangian tracking of particles based on integration of a dynamical equation of motion that accounts for pressure, added mass, lift and drag forces, (2) to perform extensive computations of both buoyant (bubbles) and slightly buoyant (droplets) particles in turbulence conditions

  12. Switchable Thermal Interfaces Based on Discrete Liquid Droplets

    SciTech Connect

    Jia, YB; Cha, G; Ju, YS

    2012-01-06

    We present a switchable thermal interface based on an array of discrete liquid droplets initially confined on hydrophilic islands on a substrate. The droplets undergo reversible morphological transition into a continuous liquid film when they are mechanically compressed by an opposing substrate to create low-thermal resistance heat conduction path. We investigate a criterion for reversible switching in terms of hydrophilic pattern size and liquid volume. The dependence of the liquid morphology and rupture distance on the diameter and areal fraction of hydrophilic islands, liquid volumes, as well as loading pressure is also characterized both theoretically and experimentally. The thermal resistance in the on-state is experimentally characterized for ionic liquids, which are promising for practical applications due to their negligible vapor pressure. A life testing setup is constructed to evaluate the reliability of the interface under continued switching conditions at relatively high switching frequencies.

  13. Patterned surface anchoring of nematic droplets at miscible liquid-liquid interfaces.

    PubMed

    Wang, Xiaoguang; Zhou, Ye; Kim, Young-Ki; Miller, Daniel S; Zhang, Rui; Martinez-Gonzalez, Jose A; Bukusoglu, Emre; Zhang, Bo; Brown, Thaddeus M; de Pablo, Juan J; Abbott, Nicholas L

    2017-08-30

    We report on the internal configurations of droplets of nematic liquid crystals (LCs; 10-50 μm-in-diameter; comprised of 4-cyano-4'-pentylbiphenyl and 4-(3-acryloyloxypropyloxy)benzoic acid 2-methyl-1,4-phenylene ester) sedimented from aqueous solutions of sodium dodecyl sulfate (SDS) onto interfaces formed with pure glycerol. We observed a family of internal LC droplet configurations and topological defects consistent with a remarkably abrupt transition from homeotropic (perpendicular) to tangential anchoring on the surface of the LC droplets in the interfacial environment. Calculations of the interdiffusion of water and glycerol at the aqueous-glycerol interface revealed the thickness of the diffuse interfacial region of the two miscible liquids to be small (0.2-0.5 μm) compared to the diameters of the LC droplets on the experimental time-scale (15-120 minutes), leading us to hypothesize that the patterned surface anchoring was induced by gradients in concentration of SDS and glycerol across the diameter of the LC droplets in the interfacial region. This hypothesis received additional support from experiments in which the time of sedimentation of the LC droplets onto the interface was systematically increased and the droplets were photo-polymerized to preserve their configurations: the configurations of the LC droplets were consistent with a time-dependent decrease in the fraction of the surface area of each droplet exhibiting homeotropic anchoring. Specifically, LC droplets with <10% surface area with tangential anchoring exhibited a bulk point defect within the LC droplet, whereas droplets with >10% surface area with tangential anchoring exhibited a boojum defect within the tangential region and a disclination loop separated the regions with tangential and homeotropic anchoring. The topological charge of these LC droplet configurations was found to be consistent with the geometrical theorems of Poincaré and Gauss and also well-described by computer

  14. High-Genus nematic liquid crystal droplets

    NASA Astrophysics Data System (ADS)

    Jayalakshmi, V.; Ekapop, P.; Fernandez-Nieves, Alberto

    2017-05-01

    We will discuss the defect structures that originate in nematic droplets with two or more handles. In these cases, the topology of the bounding surface requires the presence of defects. Our experiments elucidate where do these defects locate and how many of them populated the ground state of the system.

  15. a Theoretical Model of a Superheated Liquid Droplet Neutron Detector.

    NASA Astrophysics Data System (ADS)

    Harper, Mark Joseph

    Neutrons can interact with the atoms in superheated liquid droplets which are suspended in a viscous matrix material, resulting in the formation of charged recoil ions. These ions transfer energy to the liquid, sometimes resulting in the droplets vaporizing and producing observable bubbles. Devices employing this mechanism are known as superheated liquid droplet detectors, or bubble detectors. The basis of bubble detector operation is identical to that of bubble chambers, which have been well characterized by researchers such as Wilson, Glaser, Seitz, and others since the 1950's. Each of the microscopic superheated liquid droplets behaves like an independent bubble chamber. This dissertation presents a theoretical model which considers the three principal aspects of detector operation: nuclear reactions, charged particle energy deposition, and thermodynamic bubble formation. All possible nuclear reactions were examined and those which could reasonably result in recoil ions sufficiently energetic to vaporize a droplet were analyzed in detail. Feasible interactions having adequate cross sections include elastic and inelastic scattering, n-proton, and n-alpha reactions. Ziegler's TRansport of Ions in Matter (TRIM) code was used to calculate the ions' stopping powers in various compounds based on the ionic energies predicted by standard scattering distributions. If the ions deposit enough energy in a small enough volume then the entire droplet will vaporize without further energy input. Various theories as to the vaporization of droplets by ionizing radiation were studied and a novel method of predicting the critical (minimum) energy was developed. This method can be used to calculate the minimum required stopping power for the ion, from which the threshold neutron energy is obtainable. Experimental verification of the model was accomplished by measuring the response of two different types of bubble detectors to monoenergetic thermal neutrons, as well as to neutrons

  16. The interfacial structure of water droplets in a hydrophobic liquid

    PubMed Central

    Smolentsev, Nikolay; Smit, Wilbert J.; Bakker, Huib J.; Roke, Sylvie

    2017-01-01

    Nanoscopic and microscopic water droplets and ice crystals embedded in liquid hydrophobic surroundings are key components of aerosols, rocks, oil fields and the human body. The chemical properties of such droplets critically depend on the interfacial structure of the water droplet. Here we report the surface structure of 200 nm-sized water droplets in mixtures of hydrophobic oils and surfactants as obtained from vibrational sum frequency scattering measurements. The interface of a water droplet shows significantly stronger hydrogen bonds than the air/water or hexane/water interface and previously reported planar liquid hydrophobic/water interfaces at room temperature. The observed spectral difference is similar to that of a planar air/water surface at a temperature that is ∼50 K lower. Supercooling the droplets to 263 K does not change the surface structure. Below the homogeneous ice nucleation temperature, a single vibrational mode is present with a similar mean hydrogen-bond strength as for a planar ice/air interface. PMID:28537259

  17. The interfacial structure of water droplets in a hydrophobic liquid

    NASA Astrophysics Data System (ADS)

    Smolentsev, Nikolay; Smit, Wilbert J.; Bakker, Huib J.; Roke, Sylvie

    2017-05-01

    Nanoscopic and microscopic water droplets and ice crystals embedded in liquid hydrophobic surroundings are key components of aerosols, rocks, oil fields and the human body. The chemical properties of such droplets critically depend on the interfacial structure of the water droplet. Here we report the surface structure of 200 nm-sized water droplets in mixtures of hydrophobic oils and surfactants as obtained from vibrational sum frequency scattering measurements. The interface of a water droplet shows significantly stronger hydrogen bonds than the air/water or hexane/water interface and previously reported planar liquid hydrophobic/water interfaces at room temperature. The observed spectral difference is similar to that of a planar air/water surface at a temperature that is ~50 K lower. Supercooling the droplets to 263 K does not change the surface structure. Below the homogeneous ice nucleation temperature, a single vibrational mode is present with a similar mean hydrogen-bond strength as for a planar ice/air interface.

  18. Equilibrium contact angles of liquid droplets on ideal rough solids.

    PubMed

    Kang, Hie Chan; Jacobi, Anthony M

    2011-12-20

    This work proposes a theoretical model for predicting the apparent equilibrium contact angle of a liquid on an ideal rough surface that is homogeneous and has a negligible body force, line tension, or contact angle hysteresis between solid and liquid. The model is derived from the conservation equations and the free-energy minimization theory for the changes of state of liquid droplets. The work of adhesion is expressed as the contact angles in the wetting process of the liquid droplets. Equilibrium contact angles of liquid droplets for rough surfaces are expressed as functions of the area ratios for the solid, liquid, and surrounding gas and the roughness ratio and wetting ratio of the liquid on the solid for the partially and fully wet states. It is found that the ideal critical angle for accentuating the contact angles by the surface roughness is 48°. The present model is compared with existing experimental data and the classical Wenzel and Cassie-Baxter models and agrees with most of the experimental data for various surfaces and liquids better than does the Wenzel model and accounts for trends that the Wenzel model cannot explain.

  19. Generation and Stability of Toroidal Droplets in a Viscous Liquid

    NASA Astrophysics Data System (ADS)

    Pairam, E.; Fernández-Nieves, A.

    2009-06-01

    We use a simple method to generate toroidal droplets and study how they transform into spherical droplets. The method relies on the viscous forces exerted by a rotating continuous phase over a liquid which is extruded from an injection needle; the resultant jet is forced to close into a torus due to the imposed rotation. Once formed, the torus transforms into single or multiple spheres. Interestingly, we find there are two routes for this process depending on the aspect ratio of the torus. For thin tori, classical hydrodynamic instabilities induce its breakup into a precise number of droplets. By contrast, for sufficiently fat tori, unstable modes are unable to grow, and the torus evolves through a different route; it shrinks towards its center to coalesce onto itself, to finally form a single spherical droplet.

  20. Self-bound droplets of a dilute magnetic quantum liquid.

    PubMed

    Schmitt, Matthias; Wenzel, Matthias; Böttcher, Fabian; Ferrier-Barbut, Igor; Pfau, Tilman

    2016-11-10

    Self-bound many-body systems are formed through a balance of attractive and repulsive forces and occur in many physical scenarios. Liquid droplets are an example of a self-bound system, formed by a balance of the mutual attractive and repulsive forces that derive from different components of the inter-particle potential. It has been suggested that self-bound ensembles of ultracold atoms should exist for atom number densities that are 10(8) times lower than in a helium droplet, which is formed from a dense quantum liquid. However, such ensembles have been elusive up to now because they require forces other than the usual zero-range contact interaction, which is either attractive or repulsive but never both. On the basis of the recent finding that an unstable bosonic dipolar gas can be stabilized by a repulsive many-body term, it was predicted that three-dimensional self-bound quantum droplets of magnetic atoms should exist. Here we report the observation of such droplets in a trap-free levitation field. We find that this dilute magnetic quantum liquid requires a minimum, critical number of atoms, below which the liquid evaporates into an expanding gas as a result of the quantum pressure of the individual constituents. Consequently, around this critical atom number we observe an interaction-driven phase transition between a gas and a self-bound liquid in the quantum degenerate regime with ultracold atoms. These droplets are the dilute counterpart of strongly correlated self-bound systems such as atomic nuclei and helium droplets.

  1. Self-bound droplets of a dilute magnetic quantum liquid

    NASA Astrophysics Data System (ADS)

    Schmitt, Matthias; Wenzel, Matthias; Böttcher, Fabian; Ferrier-Barbut, Igor; Pfau, Tilman

    2016-11-01

    Self-bound many-body systems are formed through a balance of attractive and repulsive forces and occur in many physical scenarios. Liquid droplets are an example of a self-bound system, formed by a balance of the mutual attractive and repulsive forces that derive from different components of the inter-particle potential. It has been suggested that self-bound ensembles of ultracold atoms should exist for atom number densities that are 108 times lower than in a helium droplet, which is formed from a dense quantum liquid. However, such ensembles have been elusive up to now because they require forces other than the usual zero-range contact interaction, which is either attractive or repulsive but never both. On the basis of the recent finding that an unstable bosonic dipolar gas can be stabilized by a repulsive many-body term, it was predicted that three-dimensional self-bound quantum droplets of magnetic atoms should exist. Here we report the observation of such droplets in a trap-free levitation field. We find that this dilute magnetic quantum liquid requires a minimum, critical number of atoms, below which the liquid evaporates into an expanding gas as a result of the quantum pressure of the individual constituents. Consequently, around this critical atom number we observe an interaction-driven phase transition between a gas and a self-bound liquid in the quantum degenerate regime with ultracold atoms. These droplets are the dilute counterpart of strongly correlated self-bound systems such as atomic nuclei and helium droplets.

  2. Experimental investigation of the gasification mechanism and sooting characteristics of pure and multicomponent fuel droplets

    SciTech Connect

    Randolph, A.L.

    1986-01-01

    The fuels considered include aromatic and straight chain hydrocarbons, diesel, organic azides, hydrocarbons blended with alcohols and emulsions with water. A mono-disperse stream produced using the ink-jet printing technique is projected downward through a flat-flame burner into a burning/vaporization chamber. Specially designed probes are then used to quench and collect liquid and soot samples throughout the droplet life. Microphotography is utilized to provide a history of the droplet gasification rate and velocity profile. Results show that for most fuels soot is confined inside the envelope flame. Oxidation efficiently destroys all soot as it passes through the flame-front. The extremely sooty 1-methylnaphthalene is an exception to this. The reduction in sooting achieved by blending sooty fuels with non-sooty fuels is generally limited to a specific portion of the droplet life depending on the relative volatilities of the constituents. Neither alcohol nor water blending reduce sooting via a predominate kinetic oxidation of soot precursors, but the high Lewis number of water/oil macroemulsions does cause micro-explosion. The virtually immobile water cells get trapped in the droplet interior and are subsequently heated to their limit of superheat. This explosion does not enhance sooting because the heat required for instant gasification causes the flame to collapse, thus consuming much of the associated soot. Micro-explosion can also be caused by the thermal decomposition of unstable fuels. The burning times of organic diazides can be reduced by as much as 90% versus comparable paraffins by this mechanism.

  3. The effect of pressure oscillations on fuel droplet ignition

    NASA Astrophysics Data System (ADS)

    Eigenbrod, Christian; Klinkov, Konstantin; Fachini, Fernando F.

    Combustion-driven instabilities have an important influence on the performance and noise char-acteristics of gas turbines. Thermo-acoustic oscillations can increase not only emissions of noise or pollutants such as unburnt hydrocarbons or nitric oxides, but can also lead to very high levels of pressure pulsations, resulting in structural damage of the machine. Identified mechanisms capable of driving combustion instabilities include complex flow and flame interactions: fuel feed line -acoustic coupling, equivalence-ratio oscillations, oscillatory vaporization and mix-ing, oscillatory flame-area variation, vortex shedding. In order to clarify different aspects of acoustics -combustion interference it is necessary to study the simplified models. At ZARM, Bremen the effect of acoustic oscillation on single droplet ignition was studied experimentally and numerically. The experimental facility allows to investigate the ignition of a single droplet under spherical conditions (absence of natural convection) and variable pressure and temperature of the ambient gas. The suspended fuel droplet with initial diameter of 0.7 mm is placed in a furnace, two opposite walls of which are motor-driven pistons. The scale of the oscillation of gas parameters in the furnace corresponds to that in real gas-turbines under condition of a thermo-acoustic resonance. In the present work parameters of the ignition of a single n-heptane droplet under mean pressure (p0) up to 5 bar and temperature 700 K was examined. The computational model is 1-dimensional and includes processes of vaporization, multi-component diffusion and extended chemical reactions including the low-temperature branch. The model was firstly validated through the single droplet experiments achieving good agreement. Then the physical parameters were varied in order to match conditions of real gas-turbines. In this case droplet diameter was about 0.04-0.1 mm, initial pressure of the gas up to 20 bar and temperature up to 700 K

  4. Evaporation of Sessile Droplets of Liquid on Solid Substrates

    NASA Astrophysics Data System (ADS)

    Semenov, S.; Starov, V. M.; Velarde, M. G.; Rubio, R. G.

    Evaporation of sessile droplets of liquid on solid substrates is considered here. Different parameters and processes influencing the evaporation rate are discussed. Cases of complete wetting and partial wetting with contact angle hysteresis are described mathematically. The influence of Kelvin's and kinetic effects and subsequent deviation from diffusion-limited evaporation is shown by means of computer simulations.

  5. Focusing of cylindrical liquid jets into droplets

    NASA Astrophysics Data System (ADS)

    Edwards, Kristen; McCleney, Amy; Bardet, Philippe

    2013-11-01

    Upward angled water jets discharging in quiescent air are studied experimentally with time varying forcing. The jets issue from a 2 mm diameter tube, while highly controllable forcing is accomplished with a magnetic linear motor coupled with an arbitrary waveform generator. In particular, regimes of jet focusing are generated at various injection rates. The jets result in large droplets that can be created at various elevations. This type of flow mimics the spray generated by an Archer fish. Actual forcing functions were monitored using LDT.

  6. Liquid quantum droplets of ultracold magnetic atoms

    NASA Astrophysics Data System (ADS)

    Ferrier-Barbut, Igor; Schmitt, Matthias; Wenzel, Matthias; Kadau, Holger; Pfau, Tilman

    2016-11-01

    The simultaneous presence of two competing inter-particle interactions can lead to the emergence of new phenomena in a many-body system. Among others, such effects are expected in dipolar Bose-Einstein condensates, subject to dipole-dipole interaction and short-range repulsion. Magnetic quantum gases and in particular Dysprosium gases, offering a comparable short-range contact and a long-range dipolar interaction energy, remarkably exhibit such emergent phenomena. In addition an effective cancellation of mean-field effects of the two interactions results in a pronounced importance of quantum-mechanical beyond mean-field effects. For a weakly dominant dipolar interaction the striking consequence is the existence of a new state of matter equilibrated by the balance between weak mean-field attraction and beyond mean-field repulsion. Though exemplified here in the case of dipolar Bose gases, this state of matter should appear also with other microscopic interactions types, provided a competition results in an effective cancellation of the total mean-field. The macroscopic state takes the form of so-called quantum droplets. We present the effects of a long-range dipolar interaction between these droplets.

  7. The direct injection of liquid droplets into low pressure plasmas

    SciTech Connect

    Ogawa, D.; Saraf, I.; Sra, A.; Timmons, R.; Goeckner, M.; Overzet, L.

    2009-03-15

    A much greater number of useful precursors for plasma-enhanced chemical vapor deposition (PECVD) can be dispersed in high vapor pressure solvents than can be put into the vapor phase directly. In order to enable the use of such precursors, the authors investigated a method by which one can directly inject these liquids as microdroplets into low pressure PECVD environments. The solvent evaporates first leaving behind the desired precursor in the gas/plasma. The plasma dissociates the vapor and causes the deposition of a composite film (from precursor, solvent, and plasma gas). The authors made preliminary tests using Fe nanoparticles in hexane and were able to incorporate over 4% Fe in the resulting thin films. In addition, the authors simulated the process. The time required for a droplet to fully evaporate is a function of the background pressure, initial liquid temperature, droplet-vapor interactions, and initial droplet size. A typical evaporation time for a 50 {mu}m diameter droplet of hexane is {approx}3 s without plasma at 100 mTorr. The presence of plasma can decrease the evaporation time by more than an order of magnitude. In addition, the model predicts that the temperature of the injected droplet first decreases by evaporative cooling (to {approx}180 K for hexane); however, once the solvent has fully evaporated/sublimated, the plasma heats any remaining solute. As a result the solute temperature can first fall to 180 K, then rise to nearly 750 K in less than 1 s.

  8. Multiscale Simulation of Gas Film Lubrication During Liquid Droplet Collision

    NASA Astrophysics Data System (ADS)

    Chen, Xiaodong; Khare, Prashant; Ma, Dongjun; Yang, Vigor

    2012-02-01

    Droplet collision plays an elementary role in dense spray combustion process. When two droplets approach each other, a gas film forms in between. The pressure generated within the film prevents motion of approaching droplets. This fluid mechanics is fluid film lubrication that occurs when opposing bearing surfaces are completely separated by fluid film. The lubrication flow in gas film decides the collision outcome, coalescence or bouncing. Present study focuses on gas film drainage process over a wide range of Weber numbers during equal- and unequal-sized droplet collision. The formulation is based on complete set of conservation equations for both liquid and surrounding gas phases. An improved volume-of-fluid technique, augmented by an adaptive mesh refinement algorithm, is used to track liquid/gas interfaces. A unique thickness-based refinement algorithm based on topology of interfacial flow is developed and implemented to efficiently resolve the multiscale problem. The grid size on interface is up O(10-4) of droplet size with a max resolution of 0.015 μm. An advanced visualization technique using the Ray-tracing methodology is used to gain direct insights to detailed physics. Theories are established by analyzing the characteristics of shape changing and flow evolution.

  9. Numerical simulation of droplet splashing over varying thin liquid film

    NASA Astrophysics Data System (ADS)

    Dalal, Amaresh; Manik, Jai; Natarajan, Ganesh

    2016-11-01

    Droplet impact on wet surfaces is observed in various industrial processes and natural phenomenon. Behavior of droplet impact over thin liquid film is a complex phenomenon involving strong interface deformations. In the past, various studies have been performed to investigate the dynamic behavior of droplets using different geometries and physical conditions. But all the studies were primarily with constant film thickness. The present work is focused on the deformation of single and multiple droplets falling over thin liquid film with variable film thickness. The varying thicknesses of the film may be achieved by considering a sinusoidal varying bottom wall of two different amplitudes. It has been observed that the velocity with which the crown is spreading actually get decreased with the increase in the amplitude of the sinusoidally varying film. Similar behavior has been observed irrespective of the location of drop fall i.e. either falling over crest or over the trough. Also it has been noted that, in the case when droplet is falling over crest, the thickness of the lower portion of the crown rim also gets increased with the increase in amplitude of the film. This Study is funded by a Grant from BRNS, DAE, Government of India.

  10. Deposition and drying dynamics of liquid crystal droplets

    PubMed Central

    Davidson, Zoey S.; Huang, Yongyang; Gross, Adam; Martinez, Angel; Still, Tim; Zhou, Chao; Collings, Peter J.; Kamien, Randall D.; Yodh, A. G.

    2017-01-01

    Drop drying and deposition phenomena reveal a rich interplay of fundamental science and engineering, give rise to fascinating everyday effects (coffee rings), and influence technologies ranging from printing to genotyping. Here we investigate evaporation dynamics, morphology, and deposition patterns of drying lyotropic chromonic liquid crystal droplets. These drops differ from typical evaporating colloidal drops primarily due to their concentration-dependent isotropic, nematic, and columnar phases. Phase separation occurs during evaporation, and in the process creates surface tension gradients and significant density and viscosity variation within the droplet. As a result, the drying multiphase drops exhibit different convective currents, drop morphologies, and deposition patterns (coffee-rings). PMID:28555621

  11. Deposition and drying dynamics of liquid crystal droplets

    NASA Astrophysics Data System (ADS)

    Davidson, Zoey S.; Huang, Yongyang; Gross, Adam; Martinez, Angel; Still, Tim; Zhou, Chao; Collings, Peter J.; Kamien, Randall D.; Yodh, A. G.

    2017-05-01

    Drop drying and deposition phenomena reveal a rich interplay of fundamental science and engineering, give rise to fascinating everyday effects (coffee rings), and influence technologies ranging from printing to genotyping. Here we investigate evaporation dynamics, morphology, and deposition patterns of drying lyotropic chromonic liquid crystal droplets. These drops differ from typical evaporating colloidal drops primarily due to their concentration-dependent isotropic, nematic, and columnar phases. Phase separation occurs during evaporation, and in the process creates surface tension gradients and significant density and viscosity variation within the droplet. As a result, the drying multiphase drops exhibit different convective currents, drop morphologies, and deposition patterns (coffee-rings).

  12. Atomization of liquid droplets in a convective gas stream.

    NASA Technical Reports Server (NTRS)

    Ranger, A. A.; Nicholls, J. A.

    1972-01-01

    New experimental results are reported for the atomization of liquid droplets by a high-speed air stream. A series of experiments are described in which water droplets, ranging in diameter from 1000 to 2700 microns, were introduced into the test section of a shock tube and allowed to interact with the convective flow established by the passage of a propagating shock front. A rotating drum camera system was employed to obtain a collection of streak photographs of the atomization process from which the breakup time, the breakup distance, and the ultimate atomized particle size were determined.

  13. Isolated Liquid Droplet Combustion: Inhibition and Extinction Studies

    NASA Technical Reports Server (NTRS)

    Dryer, F. L.; Kroenlein, K. G.; Kazakov, A.; Williams, F. A.; Nayagam, V.

    2004-01-01

    Introduction of fire suppressants to the ambient environment surrounding a heterogeneous diffusion flame may be an inefficient technique for fire safety in systems without buoyant flows. Carbon dioxide substitution for nitrogen diluent leads to significant modifications of the sphero-symmetric burning behavior of isolated n-heptane droplets, partly through increased heat capacity within the gaseous diffusion flame, but mostly because of modifications in spectral radiative coupling in the gas phase. Effects of longer time scale phenomena such as sooting and slow gas-phase/droplet convection remain to be determined. Similar methodologies can be applied to evaluate the effects and efficacy of chemical inhibitors in the liquid and gas phases.

  14. EXPERIMENTAL LIQUID METAL FUEL REACTOR

    DOEpatents

    Happell, J.J.; Thomas, G.R.; Denise, R.P.; Bunts, J.L. Jr.

    1962-01-23

    A liquid metal fuel nuclear fission reactor is designed in which the fissionable material is dissolved or suspended in a liquid metal moderator and coolant. The liquid suspension flows into a chamber in which a critical amount of fissionable material is obtained. The fluid leaves the chamber and the heat of fission is extracted for power or other utilization. The improvement is in the support arrangement for a segrnented graphite core to permit dif ferential thermal expansion, effective sealing between main and blanket liquid metal flows, and avoidance of excessive stress development in the graphite segments. (AEC)

  15. Measurement Sensitivity Of Liquid Droplet Parameters Using Optical Fibers

    NASA Astrophysics Data System (ADS)

    Das, Alok K.; Mandal, Anup K.

    1990-02-01

    A new clad probing technique is used to measure the size, number, refractive index and viscosity of liquid droplets sprayed from a pressure nozzle on an uncoated core-clad fiber. The probe monitors the clad mode power loss within the leaky ray zone represented as a three region fiber. Liquid droplets measured are Glycerine, commercial grade Turpentine, Linseed oil and some oil mixtures. The measurement sensitivity depends on probing conditions and clad diameter which is observed experimentally and verified analytically. A maximum sensitivity is obtained for the tapered probe-fiber diameter made equal to the clad thickness. A slowly tapered probe-fiber and a small end angle as well as separation of the sensor-fiber and the probe-fiber further improve the sensitivity. Under the best probing condition for 90-percent Glycerine droplets of - 50 micron diameter and a 50/125 micron sensor fiber with clad refractive index of 1.465 and 0.2 NA, the measured sensitivity per drop is 0.015 and 0.006 dB, respectively, for (10-20) and (100-200) droplets. Sensitivities for different systems are shown. The sensitivity is optimized by choosing proper fiber for known liquids.

  16. Droplet and slug formation in polymer electrolyte membrane fuel cell flow channels: The role of interfacial forces

    NASA Astrophysics Data System (ADS)

    Colosqui, Carlos E.; Cheah, May J.; Kevrekidis, Ioannis G.; Benziger, Jay B.

    A microfluidic device is employed to emulate water droplet emergence from a porous electrode and slug formation in the gas flow channel of a PEM fuel cell. Liquid water emerges from a 50 μm pore forming a droplet; the droplet grows to span the entire cross-section of a microchannel and transitions into a slug which detaches and is swept downstream. Droplet growth, slug formation, detachment, and motion are analyzed using high-speed video images and pressure-time traces. Slug volume is controlled primarily by channel geometry, interfacial forces, and gravity. As water slugs move downstream, they leave residual micro-droplets that act as nucleation sites for the next droplet-to-slug transition. Residual liquid in the form of micro-droplets results in a significant decrease in slug volume between the very first slug formed in an initially dry channel and the ultimate "steady-state" slug. A physics-based model is presented to predict slug volumes and pressure drops for slug detachment and motion.

  17. Producing liquid fuels from biomass

    NASA Astrophysics Data System (ADS)

    Solantausta, Yrjo; Gust, Steven

    The aim of this survey was to compare, on techno-economic criteria, alternatives of producing liquid fuels from indigenous raw materials in Finland. Another aim was to compare methods under development and prepare a proposal for steering research related to this field. Process concepts were prepared for a number of alternatives, as well as analogous balances and production and investment cost assessments for these balances. Carbon dioxide emissions of the alternatives and the price of CO2 reduction were also studied. All the alternatives for producing liquid fuels from indigenous raw materials are utmost unprofitable. There are great differences between the alternatives. While the production cost of ethanol is 6 to 9 times higher than the market value of the product, the equivalent ratio for substitute fuel oil produced from peat by pyrolysis is 3 to 4. However, it should be borne in mind that the technical uncertainties related to the alternatives are of different magnitude. Production of ethanol from barley is of commercial technology, while biomass pyrolysis is still under development. If the aim is to reach smaller carbon dioxide emissions by using liquid biofuels, the most favorable alternative is pyrolysis oil produced from wood. Fuels produced from cultivated biomass are more expensive ways of reducing CO2 emissions. Their potential of reducing CO2 emissions in Finland is insignificant. Integration of liquid fuel production to some other production line is more profitable.

  18. Endotoxin-Induced Structural Transformations in Liquid Crystalline Droplets

    NASA Astrophysics Data System (ADS)

    Lin, I.-Hsin; Miller, Daniel S.; Bertics, Paul J.; Murphy, Christopher J.; de Pablo, Juan J.; Abbott, Nicholas L.

    2011-06-01

    The ordering of liquid crystals (LCs) is known to be influenced by surfaces and contaminants. Here, we report that picogram per milliliter concentrations of endotoxin in water trigger ordering transitions in micrometer-size LC droplets. The ordering transitions, which occur at surface concentrations of endotoxin that are less than 10-5 Langmuir, are not due to adsorbate-induced changes in the interfacial energy of the LC. The sensitivity of the LC to endotoxin was measured to change by six orders of magnitude with the geometry of the LC (droplet versus slab), supporting the hypothesis that interactions of endotoxin with topological defects in the LC mediate the response of the droplets. The LC ordering transitions depend strongly on glycophospholipid structure and provide new designs for responsive soft matter.

  19. Micromachined ultrasonic droplet generator based on a liquid horn structure

    NASA Astrophysics Data System (ADS)

    Meacham, J. M.; Ejimofor, C.; Kumar, S.; Degertekin, F. L.; Fedorov, A. G.

    2004-05-01

    A micromachined ultrasonic droplet generator is developed and demonstrated for drop-on-demand fluid atomization. The droplet generator comprises a bulk ceramic piezoelectric transducer for ultrasound generation, a reservoir for the ejection fluid, and a silicon micromachined liquid horn structure as the nozzle. The nozzles are formed using a simple batch microfabrication process that involves wet etching of (100) silicon in potassium hydroxide solution. Device operation is demonstrated by droplet ejection of water through 30 μm orifices at 1.49 and 2.30 MHz. The finite-element simulations of the acoustic fields in the cavity and electrical impedance of the device are in agreement with the measurements and indicate that the device utilizes cavity resonances in the 1-5 MHz range in conjunction with acoustic wave focusing by the pyramidally shaped nozzles to achieve low power operation.

  20. Stability of thin liquid films and sessile droplets under confinement.

    PubMed

    Dörfler, Fabian; Rauscher, Markus; Dietrich, S

    2013-07-01

    The stability of nonvolatile thin liquid films and of sessile droplets is strongly affected by finite size effects. We analyze their stability within the framework of density functional theory using the sharp kink approximation, i.e., on the basis of an effective interface Hamiltonian. We show that finite size effects suppress spinodal dewetting of films because it is driven by a long-wavelength instability. Therefore nonvolatile films are stable if the substrate area is too small. Similarly, nonvolatile droplets connected to a wetting film become unstable if the substrate area is too large. This instability of a nonvolatile sessile droplet turns out to be equivalent to the instability of a volatile drop which can attain chemical equilibrium with its vapor.

  1. Behavior of liquid metal droplets in an aspirating nozzle. Revision

    SciTech Connect

    Swank, W.D.; Fincke, J.R.; Mason, T.A.

    1990-12-31

    Measurements of particle size, velocity, and relative mass flux were made on spray field produced by aspirating liquid tin into 350{degrees}C argon flowing through a venturi nozzle via a small orifice in the throat of the nozzle. Details of the aspiration and droplet formation process were observed through windows in the nozzle. The spatial distribution of droplet size, velocity, and relative number density were measured at a location 10 mm from the nozzle exit. Due to the presence of separated flow in the nozzle, changes in nozzle inlet pressure did not significantly effect resulting droplet size and velocity. This suggests that good aerodynamic nozzle design is required if spray characteristics are to be controlled by nozzle flow. 5 refs.

  2. Behavior of liquid metal droplets in an aspirating nozzle

    SciTech Connect

    Swank, W.D.; Fincke, J.R.; Mason, T.A.

    1990-01-01

    Measurements of particle size, velocity, and relative mass flux were made on spray field produced by aspirating liquid tin into 350{degrees}C argon flowing through a venturi nozzle via a small orifice in the throat of the nozzle. Details of the aspiration and droplet formation process were observed through windows in the nozzle. The spatial distribution of droplet size, velocity, and relative number density were measured at a location 10 mm from the nozzle exit. Due to the presence of separated flow in the nozzle, changes in nozzle inlet pressure did not significantly effect resulting droplet size and velocity. This suggests that good aerodynamic nozzle design is required if spray characteristics are to be controlled by nozzle flow. 5 refs.

  3. Glucose sensor using liquid-crystal droplets made by microfluidics.

    PubMed

    Kim, Jiyeon; Khan, Mashooq; Park, Soo-Young

    2013-12-26

    Micrometer-sized, 4-cyno-4-pentylbiphenyl (5CB) droplets were developed for glucose detection in an aqueous medium by coating with poly(acrylicacid-b-4-cynobiphenyl-4-oxyundecylacrylate) (PAA-b-LCP) at the 5CB/water interface and covalently immobilizing glucose oxidase (GOx) to the PAA chains. This functionalized liquid-crystal (LC) droplet detected glucose from a radial to bipolar configurational change by polarized optical microscopy under crossed polarizers at concentrations as low as 0.03 mM and response times of ~3 min and showed the selective detection of glucose against galactose. This new and sensitive LC-droplet-based glucose biosensor has the merits of low production cost and easy detection by the naked eye and might be useful for prescreening the glucose level in the human body.

  4. Liquid Fuels from Microalgae

    SciTech Connect

    Johnson, D. A.; Sprague, S.

    1987-08-01

    The goal of the DOE/SERI Aquatic Species Program is to develop the technology to produce gasoline and diesel fuels from microalgae. Microalgae can accumulate large quantities of lipids and can thrive in high salinity water, which currently has no other use.

  5. 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.

  6. Surface oscillation of levitated liquid droplets under microgravity

    NASA Astrophysics Data System (ADS)

    Watanabe, Masahito; Hibiya, Taketoshi; Ozawa, Shumpei; Mizuno, Akitoshi

    2012-07-01

    Microgravity conditions have advantages of measurement of surface tension and viscosity of metallic liquids by the oscillating drop method with an electromagnetic levitation (EML) device. Thus, we are now planning the thermophysical properties, the surface tension, viscosity, density and etc., measurements of liquid alloys using the electromagnetic levitator named MSL-EML (Materials Science Laboratory Electromagnetic Levitator), which ahs been developed by the European Space Agency (ESA), installed in the International Space Station (ISS). The surface tension and the viscosity of liquid samples by the oscillating drop method are obtained from the surface oscillation frequency and damping time of surface oscillation respectively. However, analysis of oscillating drop method in EML must be improved even in the microgravity conditions, because on the EML conditions the electromagnetic force (EMF) cannot generate the surface oscillation with discretely oscillation mode. Since under microgravity the levitated droplet shape is completely spherical, the surface oscillation frequency with different oscillation modes degenerates into the single frequency. Therefore, surface tension will be not affected the EML condition under microgravity, but viscosity will be affected on the different oscillation mode of surface oscillations. Because dumping time of surface oscillation of liquid droplets depends on the oscillation modes, the case of surface oscillation including multi oscillation modes the viscosity values obtained from dumping time will be modified from the correct viscosity. Therefore, we investigate the dumping time of surface oscillation of levitated droplets with different oscillation modes and also with including multi oscillation modes using the electrostatic levitation (ESL) on ground and EML under microgravity conditions by the parabolic flight of airplane. The ESL can discretely generate the surface oscillation with different oscillation modes by the change of

  7. Liquid Droplet Detachment and Entrainment in Microscale Flows

    NASA Astrophysics Data System (ADS)

    Hidrovo, Carlos

    2005-11-01

    In this talk we will present a first order study of liquid water detachment and entrainment into air flows in hydrophobic microchannels. Silicon based microstructures consisting of 23 mm long U-shaped channels of different geometry were used for this purpose. The structures are treated with a Molecular Vapor Deposition (MVD) process that renders them hydrophobic. Liquid water is injected through a side slot located 2/3 of the way downstream from the air channel inlet. The water entering the air channel beads up into slugs or droplets that grow in size at this injection location until they fill and flood the channel or are carried away by the air flow. The slugs/droplets dimensions at detachment are correlated against superficial gas velocity and proper dimensionless parameters are postulated and examined to compare hydrodynamic forces against surface tension. It is found that slug/droplet detachment is dominated by two main forces: pressure gradient drag, arising from confinement of a viscous flow in the channel, and inertial drag, arising from the stagnation of the air due to obstruction by the slugs/droplets. A detachment regime map is postulated based on the relative importance of these forces under different flow conditions.

  8. The effect of initial diameter in sperically symmetric droplet combustion of sooting fuels

    NASA Technical Reports Server (NTRS)

    Jackson, G. S.; Avedisian, C. T.

    1994-01-01

    The effect of initial droplet diameter on the burning rate of sooting fuels - n-heptane and 1-chloro-octane - was examined experimentally at low gravity. A 1.2s drop tower provided a low gravity environment to minimize buoyancy and achieve spherically symmetric flames for stationary droplets. Free-floating and fiber-supported droplets were burned, and both techniques gave matching results for droplets of similar initial diameter. Burning rate constants for both fuels were measured for a large number of droplets ranging from 0.4 to 1.1mm in initial diameter.

  9. The effect of initial diameter in sperically symmetric droplet combustion of sooting fuels

    NASA Technical Reports Server (NTRS)

    Jackson, G. S.; Avedisian, C. T.

    1994-01-01

    The effect of initial droplet diameter on the burning rate of sooting fuels - n-heptane and 1-chloro-octane - was examined experimentally at low gravity. A 1.2s drop tower provided a low gravity environment to minimize buoyancy and achieve spherically symmetric flames for stationary droplets. Free-floating and fiber-supported droplets were burned, and both techniques gave matching results for droplets of similar initial diameter. Burning rate constants for both fuels were measured for a large number of droplets ranging from 0.4 to 1.1mm in initial diameter.

  10. Effects of fuel properties on the burning characteristics of collision-merged alkane/water droplets

    SciTech Connect

    Wang, C.H.; Pan, K.L.; Huang, W.C.; Wen, H.C.; Yang, J.Y.; Law, C.K.

    2008-04-15

    The combustion characteristics of freely falling droplets, individually generated by the merging of colliding alkane and water droplets, were experimentally investigated. The outcome of the collision droplets was first studied and then the subsequent burning processes such as the flame appearance, ignition and burning behaviors were recorded, through either visual observation or microphotography with the aid of stroboscopic lighting. If the merged droplets were exhibited in an insertive manner, while the water droplet inserted into the alkane droplet, these yield the burning behaviors prior to the end of flame were very much similar to that of pure alkane. The burning was ended with droplet extinction for lower-C alkane, and with either droplet ''flash vaporization'' or extinction for hexadecane. And if the merged droplets were in adhesive manner, for hexadecane with large water content, they either could not be ignited for the large merged droplets, or be ignited with a much prolonged ignition delay, followed by a soot-reducing flame and an ending of droplet extinction for the small merged droplets. ''Homogeneous'' explosion was not observed in any of the tests, and ''heterogeneous'' explosion, induced by trapped air bubbles, occasionally occurred for merged droplets with C-atom in alkane is higher than dodecane. And the sudden disappearance of droplet definitely decreased the burning time and thus enhanced the burning intensity. Besides, the fuel mass consumption rates were increased, even in the cases that having droplet extinction, because of the enlargement of the surface area due to the stuffing of water droplet. (author)

  11. Aerosol feed direct methanol fuel cell

    NASA Technical Reports Server (NTRS)

    Kindler, Andrew (Inventor); Narayanan, Sekharipuram R. (Inventor); Valdez, Thomas I. (Inventor)

    2002-01-01

    Improvements to fuel cells include introduction of the fuel as an aerosol of liquid fuel droplets suspended in a gas. The particle size of the liquid fuel droplets may be controlled for optimal fuel cell performance by selection of different aerosol generators or by separating droplets based upon size using a particle size conditioner.

  12. How do liquid fuel physical properties affect liquid jet development in atomisers?

    NASA Astrophysics Data System (ADS)

    Charalampous, Georgios; Hardalupas, Yannis

    2016-10-01

    The influence of liquid fuel properties on atomisation remains an open question. The droplet sizes in sprays from atomisers operated with different fuels may be modified despite the small changes of the liquid properties. This paper examines experimentally the development of a liquid jet injected from a plain orifice in order to evaluate changes in its behaviour due to modifications of the liquid properties, which may influence the final atomisation characteristics. Two aviation kerosenes with similar, but not identical physical properties are considered, namely, standard JP8 kerosene as the reference fuel and bio-derived hydro-processed renewable jet fuel as an alternative biofuel. The corresponding density, dynamic viscosity, kinematic viscosity, and surface tension change by about +5%, -5%, -10%, and +5%, respectively, which are typical for "drop-in" fuel substitution. Three aspects of the liquid jet behaviour are experimentally considered. The pressure losses of the liquid jet through the nozzle are examined in terms of the discharge coefficient for different flowrates. The morphology of the liquid jet is visualised using high magnification Laser Induced Fluorescence (LIF) imaging. Finally, the temporal development of the liquid jet interfacial velocity as a function of distance from the nozzle exit is measured from time-dependent motion analysis of dual-frame LIF imaging measurements of the jet. The results show that for the small changes in the physical properties between the considered liquid fuels, the direct substitution of fuel did not result in a drastic change of the external morphology of the fuel jets. However, the small changes in the physical properties modify the interfacial velocities of the liquid and consequently the internal jet velocity profile. These changes can modify the interaction of the liquid jet with the surroundings, including air flows in coaxial or cross flow atomisation, and influence the atomisation characteristics during the

  13. Nanoparticle interfacial assembly in liquid crystal droplets

    NASA Astrophysics Data System (ADS)

    Rahimi, Mohammad; Roberts, Tyler; Armas-Perez, Julio; Wang, Xiaoguang; Bukusoglu, Emre; Abbott, Nicholas L.; de Pablo, Juan J.

    2015-03-01

    Controlled assembly of nanoparticles at liquid crystal interfaces could lead to easily manufacturable building blocks for assembly of materials with tunable mechanical, optical, and electronic properties. Past work has examined nanoparticle assembly at planar liquid crystal interfaces. In this work we show that nanoparticle assembly on curved interfaces is drastically different, and arises for conditions under which assembly is too weak to occur on planar interfaces. We also demonstrate that LC-mediated nanoparticle interactions are strong, are remarkably sensitive to surface anchoring, and lead to hexagonal arrangements that do not arise in bulk systems. All these elements form the basis for a highly tunable, predictable, and versatile platform for hierarchical materials assembly. National Science Foundation through the UW MRSEC.

  14. Modeling texture transitions in cholesteric liquid crystal droplets

    NASA Astrophysics Data System (ADS)

    Selinger, Robin; Gimenez-Pinto, Vianney; Lu, Shin-Ying; Selinger, Jonathan; Konya, Andrew

    2012-02-01

    Cholesteric liquid crystals can be switched reversibly between planar and focal-conic textures, a property enabling their application in bistable displays, liquid crystal writing tablets, e-books, and color switching ``e-skins.'' To explore voltage-pulse induced switching in cholesteric droplets, we perform simulation studies of director dynamics in three dimensions. Electrostatics calculations are solved at each time step using an iterative relaxation method. We demonstrate that as expected, a low amplitude pulse drives the transition from planar to focal conic, while a high amplitude pulse drives the transition from focal conic back to the planar state. We use the model to explore the effects of droplet shape, aspect ratio, and anchoring conditions, with the goal of minimizing both response time and energy consumption.

  15. Study of orifice fabrication technologies for the liquid droplet radiator

    NASA Technical Reports Server (NTRS)

    Wallace, David B.; Hayes, Donald J.; Bush, J. Michael

    1991-01-01

    Eleven orifice fabrication technologies potentially applicable for a liquid droplet radiator are discussed. The evaluation is focused on technologies capable of yielding 25-150 microns diameter orifices with trajectory accuracies below 5 milliradians, ultimately in arrays of up to 4000 orifices. An initial analytical screening considering factors such as trajectory accuracy, manufacturability, and hydrodynamics of orifice flow is presented. Based on this screening, four technologies were selected for experimental evaluation. A jet straightness system used to test 50-orifice arrays made by electro-discharge machining (EDM), Fotoceram, and mechanical drilling is discussed. Measurements on orifice diameter control and jet trajectory accuracy are presented and discussed. Trajectory standard deviations are in the 4.6-10.0 milliradian range. Electroforming and EDM appear to have the greatest potential for Liquid Droplet Radiator applications. The direction of a future development effort is discussed.

  16. Oscillating Droplets and Incompressible Liquids: Slow-Motion Visualization of Experiments with Fluids

    ERIC Educational Resources Information Center

    Vollmer, Michael; Mollmann, Klaus-Peter

    2012-01-01

    We present fascinating simple demonstration experiments recorded with high-speed cameras in the field of fluid dynamics. Examples include oscillations of falling droplets, effects happening upon impact of a liquid droplet into a liquid, the disintegration of extremely large droplets in free fall and the consequences of incompressibility. (Contains…

  17. Oscillating Droplets and Incompressible Liquids: Slow-Motion Visualization of Experiments with Fluids

    ERIC Educational Resources Information Center

    Vollmer, Michael; Mollmann, Klaus-Peter

    2012-01-01

    We present fascinating simple demonstration experiments recorded with high-speed cameras in the field of fluid dynamics. Examples include oscillations of falling droplets, effects happening upon impact of a liquid droplet into a liquid, the disintegration of extremely large droplets in free fall and the consequences of incompressibility. (Contains…

  18. Experiments on the effect of initial diameter in spherically symmetric droplet combustion of sooting fuels

    NASA Technical Reports Server (NTRS)

    Jackson, G. S.; Avedisian, C. T.

    1993-01-01

    The effect of initial droplet diameter on the burning rate of sooting fuels (n-heptane and 1-chloro-octane) is studied experimentally at low gravity. A 1.2 s drop tower provided a low gravity environment to minimize buoyancy and achieve spherically symmetric flames for stationary droplets. Free-floating and fiber supported droplets were burned, and both methods gave matching results for droplets of similar initial diameter.

  19. Fuel Injector With Shear Atomizer

    NASA Technical Reports Server (NTRS)

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

    1995-01-01

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

  20. Atomization characteristics and instabilities in the combustion of multi-component fuel droplets with high volatility differential.

    PubMed

    Rao, D Chaitanya Kumar; Karmakar, Srinibas; Basu, Saptarshi

    2017-08-21

    We delineate and examine the successive stages of ligament-mediated atomization of burning multi-component fuel droplets. Time-resolved high-speed imaging experiments are performed with fuel blends (butanol/Jet A-1 and ethanol/Jet A-1) comprising wide volatility differential, which undergo distinct modes of secondary atomization. Upon the breakup of vapor bubble, depending on the aspect ratio, ligaments grow and break into well-defined (size) droplets for each mode of atomization. The breakup modes either induce mild/intense oscillations on the droplet or completely disintegrate the droplet (micro-explosion). For the blends with a relatively low volatility difference between the components, only bubble expansion contributes to the micro-explosion. In contrast, for blends with high volatility differential, both bubble growth as well as the instability at the interface contribute towards droplet breakup. The wrinkling pattern at the vapor-liquid interface suggests that a Rayleigh-Taylor type of instability triggered at the interface further expedites the droplet breakup.

  1. The Study of a Liquid Droplet Falling Through Two Immiscible Layers of Liquids

    NASA Astrophysics Data System (ADS)

    Mesa, Bianca

    2013-11-01

    In an exploratory experiment, we noticed the unusual behaviors of liquid droplets falling through layers of oil and water. A rectangular container was filled with an aqueous solution and a layer of oil. A dropper was used to control the size of the droplet. Water was mixed with Bromothymol Blue dye, a chemical indicator, to visualize the flow processes. Surface tension and the buoyancy of the oil layer between the liquid droplet and the water below caused the liquid droplet to be stopped at the interface. Over time, the support weakened and the droplet would fall quickly through the water. The first of two cases was a salt water solution with NaOH, and the second consisted of balsamic vinegar and NaOH. Once the salt water droplet touched the aqueous solution, it collapsed, sank and spread rapidly at the interface. The sinking motion dragged the spreading fluid back to its center and then down. For the second case, a trace amount of the droplet spread rapidly at the interface while the main portion of the droplet sank and then spontaneously exploded. The difference in behavior is mainly due to the surface tension of the droplet in water. The underlying mechanisms of the droplet's flow instability are from the effects of diffusion weakening the surface tension. Bianca Mesa is an undergraduate student in the Ocean and Mechanical Engineering Department at Florida Atlantic University. She is pursuing a B.S. degree in Ocean Engineering. In addition to her academic interests, she is also an avid sailor.

  2. Droplet impact on deep liquid pools: Rayleigh jet to formation of secondary droplets

    NASA Astrophysics Data System (ADS)

    Castillo-Orozco, Eduardo; Davanlou, Ashkan; Choudhury, Pretam K.; Kumar, Ranganathan

    2015-11-01

    The impact of droplets on a deep pool has applications in cleaning up oil spills, spray cooling, painting, inkjet printing, and forensic analysis, relying on the changes in properties such as viscosity, interfacial tension, and density. Despite the exhaustive research on different aspects of droplet impact, it is not clear how liquid properties can affect the instabilities leading to Rayleigh jet breakup and number of daughter drops formed after its pinch-off. In this article, through systematic experiments we investigate the droplet impact phenomena by varying viscosity and surface tension of liquids as well as impact speeds. Further, using numerical simulations, we show that Rayleigh-Plateau instability is influenced by these parameters, and capillary time scale is the appropriate scale to normalize the breakup time. Based on Ohnesorge number (Oh) and impact Weber number (We), a regime map for no breakup, Rayleigh jet breakup, and crown splash is suggested. Interestingly, crown splash is observed to occur at all Ohnesorge numbers; however, at high Oh, a large portion of kinetic energy is dissipated, and thus the Rayleigh jet is suppressed regardless of high impact velocity. The normalized required time for the Rayleigh jet to reach its peak varies linearly with the critical height of the jet.

  3. Imaging and manipulation of nanometer-size liquid droplets by scanning polarization force microscopy

    SciTech Connect

    Hu, J.; Carpick, R.W.; Salmeron, M.; Xiao, X.

    1996-03-01

    Using atomic force microscopy in noncontact mode, we have imaged nanometer-size liquid droplets of KOH water solutions on the surfaces of highly oriented pyrolitic graphite and mica. On graphite the droplets prefer to be adsorbed on atomic step edges. Droplets on the same step tend to be evenly spaced and of similar size. The droplets can be manipulated by the atomic force microscopy tip allowing the controllable formation of droplet patterns on the surface. {copyright} {ital 1996 American Vacuum Society}

  4. Laser-induced actuation of individual microsize liquid metal droplets on an open solid surface

    NASA Astrophysics Data System (ADS)

    Liu, Wei; Wang, Chunqing; Dou, Guangbin; Tian, Yanhong; Yang, Lei

    2017-01-01

    The actuation of microsize liquid metal droplets on an open solid surface with laser offset heating is reported in this work. The process allows the droplets to move towards the laser beam center. The analysis of the actuations showed that the droplets were predominantly driven by the thermally induced wettability alteration on the solid; in contrast, Marangoni flow and vapor recoil weakened the motion of the droplets. This indicates that a localized thermal gradient was the driving force for droplet motion and suggests that it may be an alternative actuation technique in manipulating liquid metal droplets for microsystems.

  5. Measurement of surface tension of liquid microdroplets through observation of droplet collision

    NASA Astrophysics Data System (ADS)

    Hayakawa, Daichi; Hirano, Taichi; Mitani, Shujiro; Sakai, Keiji

    2017-07-01

    We investigate the applicability of measuring surface tension of liquid microdroplets by analyzing their oscillatory behavior induced by droplet collision. The eigenfrequency of droplet oscillation reflects surface tension for small-amplitude oscillation. In this study, the oscillation frequencies of ethanol-ethanol and water-water droplet collisions are measured by direct observation. We experimentally verify that surface tension can be measured for deformation smaller than 10% of the droplet radius. The collision between ethanol-water droplets is also analyzed. The eigenfrequency induced by unlike-droplet collision exhibits a peculiar behavior, which may be attributed to the temporal hybrid structure of a combined droplet.

  6. Formation of liquid sheets by deposition of droplets on a surface.

    PubMed

    Dalili, Alireza; Chandra, Sanjeev; Mostaghimi, Javad; Fan, H T Charles; Simmer, Joseph C

    2014-03-15

    Experiments were done to observe the coalescence of highly viscous liquid droplets (87 wt% glycerin-in-water solutions) deposited onto a flat, solid steel plate. Droplets were deposited sequentially in straight lines or square droplet arrays. Droplet center-to-center distance was varied and the final dimensions of lines and sheets measured from photographs. When overlapping droplets were deposited surface tension forces pulled impacting droplets towards those already on the surface, a phenomena known as drawback. A dimensionless drawback index, quantifying the extent of droplet displacement, was calculated from experimental measurements for different values of droplet overlap. At large overlaps droplets deposited in a line or square array coalesced to form a circular film. When the droplet center-to-center distance increased, leading to less interaction, long, thin lines and square sheets were formed. As overlap was further decreased lines and sheets became discontinuous. A simple model was developed to predict the conditions under which rupture occurred. The lowest droplet overlap ratio (defined as droplet overlap distance divided by droplet spread diameter) at which a continuous liquid film could be formed was λ=0.293. At large overlap ratios (λ>0.6) droplets deposited in a square array formed a circular film. The minimum thickness of a continuous film formed by coalescence of droplets was shown to vary from 5% to 70% of the initial droplet diameter while increasing impact Weber and Reynolds number reduced the film thickness. Copyright © 2013 Elsevier Inc. All rights reserved.

  7. Pulsating-gliding transition in the dynamics of levitating liquid nitorgen droplets.

    SciTech Connect

    Snezhko, A.; Jacob, E. B.; Aranson, I. S.; Materials Science Division; Tel-Aviv Univ.

    2008-04-21

    Hot surfaces can cause levitation of small liquid droplets if the temperature is kept above the Leidenfrost point (220 C for water) due to the pressure formed because of rapid evaporation. Here, we demonstrate a new class of pulsating-gliding dynamic transitions in a special setting of the Leidenfrost effect at room temperatures and above a viscous fluid for droplets of liquid nitrogen. A whole range of highly dynamic patterns unfolds when droplets of liquid nitrogen are poured on the surface of another, more viscous liquid at room temperature. We also discovered that the levitating droplets induce vortex motion in the supporting viscous liquid. Depending on the viscosity of the supporting liquid, the nitrogen droplets either adopt an oscillating (pulsating) star-like shape with different azimuthal symmetries (from 2-9 petals) or glide on the surface with random trajectories. Thus, by varying the viscosity of the supporting liquid, we achieve controlled morphology and dynamics of Leidenfrost droplets.

  8. Kinetics of diffusional droplet growth in a liquid/liquid two-phase system

    NASA Technical Reports Server (NTRS)

    Glickman, M. E.; Fradkov, V. E.

    1995-01-01

    A new powerful experimental technique based on holographic observations, developed at the NASA Marshall Space Flight Center, now permits observation of small liquid droplets coarsening. This technique was developed and used for mixed-dimensional coarsening studies. Experiments were conducted on an isopycnic two-phase alloy of succinonitrile and water, annealed isothermally over a four-month period. The succinonitrile-rich droplets precipitate from a water-rich liquid matrix having a density very close to that of the droplets. The matrix and droplets, however, have different optical indices. The results of these experiments, along with the results of computer simulation based on the quasi-static diffusion approximation developed at Rensselaer are reported. These results were published recently. Copies of these papers are attached to this report.

  9. On the application of the PFEM to droplet dynamics modeling in fuel cells

    NASA Astrophysics Data System (ADS)

    Ryzhakov, Pavel B.; Jarauta, Alex; Secanell, Marc; Pons-Prats, Jordi

    2017-07-01

    The Particle Finite Element Method (PFEM) is used to develop a model to study two-phase flow in fuel cell gas channels. First, the PFEM is used to develop the model of free and sessile droplets. The droplet model is then coupled to an Eulerian, fixed-grid, model for the airflow. The resulting coupled PFEM-Eulerian algorithm is used to study droplet oscillations in an air flow and droplet growth in a low-temperature fuel cell gas channel. Numerical results show good agreement with predicted frequencies of oscillation, contact angle, and deformation of injected droplets in gas channels. The PFEM-based approach provides a novel strategy to study droplet dynamics in fuel cells.

  10. Liquid crystalline pattern formation in drying droplets of biopolymers

    NASA Astrophysics Data System (ADS)

    Smalyukh, Ivan; Zribi, Olena; Butler, John; Lavrentovich, Oleg; Wong, Gerard

    2006-03-01

    When a droplet of DNA in water dries out, a ring-like deposit is observed along the perimeter, similar to the stains in spilled drops of coffee. However, the dried ring of DNA is a self-similar birefringent pattern composed of extended molecules. We examine dynamics of the pattern formation at the droplet's rim. This gives us an insight into the underlining physics. During the major part of drying process the contact line is pinned so that DNA molecules are brought to the perimeter and extended by the radial capillary flow. Lyotropic nematic phase is formed in which highly concentrated DNA aligns along the triple line to minimize elastic energy. When the contact angle becomes small, the contact line starts to retract and the radial dilative stress causes buckling distortions at the rim which then propagate deep into the elastic liquid- crystalline medium and give rise to the pattern.

  11. High pressure combustion of liquid fuels. [alcohol and n-paraffin fuels

    NASA Technical Reports Server (NTRS)

    Canada, G. S.

    1974-01-01

    Measurements were made of the burning rates and liquid surface temperatures for a number of alcohol and n-paraffin fuels under natural and forced convection conditions. Porous spheres ranging in size from 0.64-1.9 cm O.D. were emloyed to simulate the fuel droplets. The natural convection cold gas tests considered the combustion in air of methanol, ethanol, propanol-1, n-pentane, n-heptane, and n-decane droplets at pressures up to 78 atmospheres. The pressure levels of the natural convection tests were high enough so that near critical combustion was observed for methanol and ethanol vaporization rates and liquid surface temperature measurements were made of droplets burning in a simulated combustion chamber environment. Ambient oxygen molar concentrations included 13%, 9.5% and pure evaporation. Fuels used in the forced convection atmospheric tests included those listed above for the natural convection tests. The ambient gas temperature ranged from 600 to 1500 K and the Reynolds number varied from 30 to 300. The high pressure forced convection tests employed ethanol and n-heptane as fuels over a pressure range of one to 40 atmospheres. The ambient gas temperature was 1145 K for the two combustion cases and 1255 K for the evaporation case.

  12. Holographic studies of the vapor explosion of vaporizing water-in-fuel emulsion droplets

    NASA Technical Reports Server (NTRS)

    Sheffield, S. A.; Hess, C. F.; Trolinger, J. D.

    1982-01-01

    Holographic studies were performed which examined the fragmentation process during vapor explosion of a water-in-fuel (hexadecane/water) emulsion droplet. Holograms were taken at 700 to 1000 microseconds after the vapor explosion. Photographs of the reconstructed holograms reveal a wide range of fragment droplet sizes created during the explosion process. Fragment droplet diameters range from below 10 microns to over 100 microns. It is estimated that between ten thousand and a million fragment droplets can result from this extremely violent vapor explosion process. This enhanced atomization is thus expected to have a pronounced effect on vaporization processes which are present during combustion of emulsified fuels.

  13. Light scattering by radially inhomogeneous fuel droplets in a high-temperature environment

    NASA Astrophysics Data System (ADS)

    Schneider, Michael; Hirleman, E. Dan; Saleheen, Hasan I.; Chowdhury, Dipakbin Q.; Hill, Steven C.

    1993-05-01

    Light scattering by radially inhomogeneous fuel droplets has been calculated using both geometrical optics (GO) and the exact separation of variables (SV) solutions. The refractive index profiles of the fuel droplets were those calculated by Kneer et al. The GO and SV solutions agree very well in the forward direction (for scattering angles between 30 and 60 degrees), and less well in the backward direction (for scattering angles between 140 and 170 degrees). Both amplitudes and phases of the scattered light are compared. The agreement in the backward direction is much better for 40 micrometers diameter droplets than for 20 micrometers diameter droplets.

  14. Simulation of water vapor condensation on LOX droplet surface using liquid nitrogen

    NASA Technical Reports Server (NTRS)

    Powell, Eugene A.

    1988-01-01

    The formation of ice or water layers on liquid oxygen (LOX) droplets in the Space Shuttle Main Engine (SSME) environment was investigated. Formulation of such ice/water layers is indicated by phase-equilibrium considerations under conditions of high partial pressure of water vapor (steam) and low LOX droplet temperature prevailing in the SSME preburner or main chamber. An experimental investigation was begun using liquid nitrogen as a LOX simulant. A monodisperse liquid nitrogen droplet generator was developed which uses an acoustic driver to force the stream of liquid emerging from a capillary tube to break up into a stream of regularly space uniformly sized spherical droplets. The atmospheric pressure liquid nitrogen in the droplet generator reservoir was cooled below its boiling point to prevent two phase flow from occurring in the capillary tube. An existing steam chamber was modified for injection of liquid nitrogen droplets into atmospheric pressure superheated steam. The droplets were imaged using a stroboscopic video system and a laser shadowgraphy system. Several tests were conducted in which liquid nitrogen droplets were injected into the steam chamber. Under conditions of periodic droplet formation, images of 600 micron diameter liquid nitrogen droplets were obtained with the stroboscopic video systems.

  15. Stationary Liquid Fuel Fast Reactor

    SciTech Connect

    Yang, Won Sik; Grandy, Andrew; Boroski, Andrew; Krajtl, Lubomir; Johnson, Terry

    2015-09-30

    For effective burning of hazardous transuranic (TRU) elements of used nuclear fuel, a transformational advanced reactor concept named SLFFR (Stationary Liquid Fuel Fast Reactor) was proposed based on stationary molten metallic fuel. The fuel enters the reactor vessel in a solid form, and then it is heated to molten temperature in a small melting heater. The fuel is contained within a closed, thick container with penetrating coolant channels, and thus it is not mixed with coolant nor flow through the primary heat transfer circuit. The makeup fuel is semi- continuously added to the system, and thus a very small excess reactivity is required. Gaseous fission products are also removed continuously, and a fraction of the fuel is periodically drawn off from the fuel container to a processing facility where non-gaseous mixed fission products and other impurities are removed and then the cleaned fuel is recycled into the fuel container. A reference core design and a preliminary plant system design of a 1000 MWt TRU- burning SLFFR concept were developed using TRU-Ce-Co fuel, Ta-10W fuel container, and sodium coolant. Conservative design approaches were adopted to stay within the current material performance database. Detailed neutronics and thermal-fluidic analyses were performed to develop a reference core design. Region-dependent 33-group cross sections were generated based on the ENDF/B-VII.0 data using the MC2-3 code. Core and fuel cycle analyses were performed in theta-r-z geometries using the DIF3D and REBUS-3 codes. Reactivity coefficients and kinetics parameters were calculated using the VARI3D perturbation theory code. Thermo-fluidic analyses were performed using the ANSYS FLUENT computational fluid dynamics (CFD) code. Figure 0.1 shows a schematic radial layout of the reference 1000 MWt SLFFR core, and Table 0.1 summarizes the main design parameters of SLFFR-1000 loop plant. The fuel container is a 2.5 cm thick cylinder with an inner radius of 87.5 cm. The fuel

  16. Evaporation of thin liquid droplets on heated surfaces: theory versus experiment

    NASA Astrophysics Data System (ADS)

    Sodtke, Christof; Ajaev, Vladimir; Stephan, Peter

    2005-11-01

    We carry out combined experimental and theoretical studies of liquid droplets on heated surfaces in a closed container filled with saturated vapor. The droplets are deposited on an electrically heated stainless steel foil. Evolution of droplet shapes is studied by optical methods simultaneously with high resolution temperature measurements using thermochromic liquid crystals (TLCs). A mathematical model is developed based on the assumption of liquid droplet thickness being much smaller than its radius. Both the dynamics of liquid-vapor interface and the temperature profiles in the foil are shown to be in good agreement with the experimental data.

  17. Droplet turbulence interactions under subcritical and supercritical conditions

    NASA Astrophysics Data System (ADS)

    Coy, E. B.; Greenfield, S. C.; Ondas, M. S.; Song, Y.-H.; Spegar, T. D.; Santavicca, D. A.

    1993-11-01

    The goal of this research is to experimentally characterize the behavior of droplets in vaporizing liquid sprays under conditions typical of those encountered in high pressure combustion systems such as liquid fueled rocket engines. Of particular interest are measurements of droplet drag, droplet heating, droplet vaporization, droplet distortion, and secondary droplet breakup, under both subcritical and supercritical conditions. The paper presents a brief description of the specific accomplishments which have been made over the past year.

  18. Droplet turbulence interactions under subcritical and supercritical conditions

    NASA Technical Reports Server (NTRS)

    Coy, E. B.; Greenfield, S. C.; Ondas, M. S.; Song, Y.-H.; Spegar, T. D.; Santavicca, D. A.

    1993-01-01

    The goal of this research is to experimentally characterize the behavior of droplets in vaporizing liquid sprays under conditions typical of those encountered in high pressure combustion systems such as liquid fueled rocket engines. Of particular interest are measurements of droplet drag, droplet heating, droplet vaporization, droplet distortion, and secondary droplet breakup, under both subcritical and supercritical conditions. The paper presents a brief description of the specific accomplishments which have been made over the past year.

  19. Liquid crystals in micron-scale droplets, shells and fibers.

    PubMed

    Urbanski, Martin; Reyes, Catherine G; Noh, JungHyun; Sharma, Anshul; Geng, Yong; Subba Rao Jampani, Venkata; Lagerwall, Jan P F

    2017-04-05

    The extraordinary responsiveness and large diversity of self-assembled structures of liquid crystals are well documented and they have been extensively used in devices like displays. For long, this application route strongly influenced academic research, which frequently focused on the performance of liquid crystals in display-like geometries, typically between flat, rigid substrates of glass or similar solids. Today a new trend is clearly visible, where liquid crystals confined within curved, often soft and flexible, interfaces are in focus. Innovation in microfluidic technology has opened for high-throughput production of liquid crystal droplets or shells with exquisite monodispersity, and modern characterization methods allow detailed analysis of complex director arrangements. The introduction of electrospinning in liquid crystal research has enabled encapsulation in optically transparent polymeric cylinders with very small radius, allowing studies of confinement effects that were not easily accessible before. It also opened the prospect of functionalizing textile fibers with liquid crystals in the core, triggering activities that target wearable devices with true textile form factor for seamless integration in clothing. Together, these developments have brought issues center stage that might previously have been considered esoteric, like the interaction of topological defects on spherical surfaces, saddle-splay curvature-induced spontaneous chiral symmetry breaking, or the non-trivial shape changes of curved liquid crystal elastomers with non-uniform director fields that undergo a phase transition to an isotropic state. The new research thrusts are motivated equally by the intriguing soft matter physics showcased by liquid crystals in these unconventional geometries, and by the many novel application opportunities that arise when we can reproducibly manufacture these systems on a commercial scale. This review attempts to summarize the current understanding of

  20. Liquid crystals in micron-scale droplets, shells and fibers

    NASA Astrophysics Data System (ADS)

    Urbanski, Martin; Reyes, Catherine G.; Noh, JungHyun; Sharma, Anshul; Geng, Yong; Subba Rao Jampani, Venkata; Lagerwall, Jan P. F.

    2017-04-01

    The extraordinary responsiveness and large diversity of self-assembled structures of liquid crystals are well documented and they have been extensively used in devices like displays. For long, this application route strongly influenced academic research, which frequently focused on the performance of liquid crystals in display-like geometries, typically between flat, rigid substrates of glass or similar solids. Today a new trend is clearly visible, where liquid crystals confined within curved, often soft and flexible, interfaces are in focus. Innovation in microfluidic technology has opened for high-throughput production of liquid crystal droplets or shells with exquisite monodispersity, and modern characterization methods allow detailed analysis of complex director arrangements. The introduction of electrospinning in liquid crystal research has enabled encapsulation in optically transparent polymeric cylinders with very small radius, allowing studies of confinement effects that were not easily accessible before. It also opened the prospect of functionalizing textile fibers with liquid crystals in the core, triggering activities that target wearable devices with true textile form factor for seamless integration in clothing. Together, these developments have brought issues center stage that might previously have been considered esoteric, like the interaction of topological defects on spherical surfaces, saddle-splay curvature-induced spontaneous chiral symmetry breaking, or the non-trivial shape changes of curved liquid crystal elastomers with non-uniform director fields that undergo a phase transition to an isotropic state. The new research thrusts are motivated equally by the intriguing soft matter physics showcased by liquid crystals in these unconventional geometries, and by the many novel application opportunities that arise when we can reproducibly manufacture these systems on a commercial scale. This review attempts to summarize the current understanding of

  1. Effect of droplet shape on ring stains from dried liquid

    NASA Astrophysics Data System (ADS)

    Santiago, Melvin; Brown, Katherine; Mathur, Harsh

    A landmark experimental paper on coffee stains by Deegan et al included a simple theoretical analysis of circular droplets. The analysis was based on a model informally called the Maxwell House equations. It describes the evolving height profile of the droplet, the evaporation of the solvent and the outflow of solute to the rim of the droplet. Since typical droplets are not circles, here we extend the analysis to more general shapes. We find that for thin droplets the height profile may be determined by solving Poisson's equation in a domain corresponding to the footprint of the droplet. Evaporation is treated in a simple approximation via an electrostatic analogy and is dominated by the sharp edges of the droplet. Assuming zero vorticity allows us to analyze the solvent flow in droplets of arbitrary shape. We compare circular droplets to other shapes including long linear droplets, ring shaped droplets and droplets with an elliptical footprint

  2. Reduced Gravity Studies of Soret Transport Effects in Liquid Fuel Combustion

    NASA Technical Reports Server (NTRS)

    Shaw, Benjamin D.

    2004-01-01

    Soret transport, which is mass transport driven by thermal gradients, can be important in practical flames as well as laboratory flames by influencing transport of low molecular weight species (e.g., monatomic and diatomic hydrogen). In addition, gas-phase Soret transport of high molecular weight fuel species that are present in practical liquid fuels (e.g., octane or methanol) can be significant in practical flames (Rosner et al., 2000; Dakhlia et al., 2002) and in high pressure droplet evaporation (Curtis and Farrell, 1992), and it has also been shown that Soret transport effects can be important in determining oxygen diffusion rates in certain classes of microgravity droplet combustion experiments (Aharon and Shaw, 1998). It is thus useful to obtain information on flames under conditions where Soret effects can be clearly observed. This research is concerned with investigating effects of Soret transport on combustion of liquid fuels, in particular liquid fuel droplets. Reduced-gravity is employed to provide an ideal (spherically-symmetrical) experimental model with which to investigate effects of Soret transport on combustion. The research will involve performing reduced-gravity experiments on combustion of liquid fuel droplets in environments where Soret effects significantly influence transport of fuel and oxygen to flame zones. Experiments will also be performed where Soret effects are not expected to be important. Droplets initially in the 0.5 to 1 mm size range will be burned. Data will be obtained on influences of Soret transport on combustion characteristics (e.g., droplet burning rates, droplet lifetimes, gas-phase extinction, and transient flame behaviors) under simplified geometrical conditions that are most amenable to theoretical modeling (i.e., spherical symmetry). The experiments will be compared with existing theoretical models as well as new models that will be developed. Normal gravity experiments will also be performed.

  3. Fiber optic probe for primary zone fuel distribution measurements in actual liquid-fueled gas turbine combustors

    NASA Astrophysics Data System (ADS)

    Lee, Jong-Guen; Santavicca, Domenic A.

    1999-01-01

    A laser induced fluorescence (LIF)-based optical fiber probe has been developed for spatially and temporally resolved measurements of the equivalence ratio in actual gas turbine combustors. By using the probe to simultaneously detect laser induced fluorescence and Mie-scattering, its applicability has been extended to liquid-fueled combustors. The probe has been tested in a simple flow system consisting of a four-inch diameter flow tube with a spray nozzle at the center and Jet-A as the fuel. PDPA measurements are made to correlate the Mie-scattering signal with the number density of liquid droplets. The results indicate that the probe can be used for qualitative characterization of liquid fuel vaporization, and that quantitative measurement of fuel vapor concentration in liquid-fueled gas turbine combustion is possible with calibration of the temperature dependence of the fluorescence.

  4. Evaporation of thin liquid droplets on heated surfaces

    NASA Astrophysics Data System (ADS)

    Sodtke, C.; Ajaev, V. S.; Stephan, P.

    2007-05-01

    We carry out combined experimental and theoretical studies of liquid droplet evaporation on heated surfaces in a closed container filled with saturated vapor. The droplets are deposited on an electrically heated thin stainless steel foil. The evolution of droplet shapes is studied by optical methods simultaneously with high-resolution foil temperature measurements using thermochromic liquid crystals. A mathematical model is developed based on the assumptions that the droplet surface has uniform mean curvature and the contact line is pinned during evaporation. Both the dynamics of liquid vapor interface and the temperature profiles at the foil are shown to be in good agreement with the experimental data. Droplet Evaporation Contact line Pinning List of symbols c heat capacity, J/kg K d thickness of the foil, μm h nondimensional droplet height h d droplet height, m K kinetic parameter k thermal conductivity, W/m K Δh lv latent heat, J/kg n nondimensional coordinate

  5. Theory of Influence of a Low-Volatility, Soluble Impurity on Spherically-Symmetric Combustion of Fuel Droplets

    NASA Technical Reports Server (NTRS)

    Shaw, B. D.; Williams, F. A.

    1990-01-01

    Analyses are given for the evolution of liquid-phase mass fraction profiles and temperature during combustion of fuel droplets composed of binary miscible mixtures of low-volatility and high-volatility constituents, with small initial mass fractions of the low-volatility material, or slow introduction of low-volatility material into the liquid phase by absorption from the gas phase. The gas phase is assumed to remain quasi-steady and the liquid temperature spatially uniform. The ratio of the liquid-phase diffusion coefficient to the initial burning-rate constant is treated as a small parameter. Asymptotic analyses in this parameter are developed, and the conservation equations are integrated numerically in obtaining descriptions of the combustion history. It is shown that at the surface of the droplet a boundary layer arises in which the mass fraction of the low-volatility component increases with time. The results are used to explain qualitatively some observed conditions of flame contraction and liquid disruption in droplet combustion.

  6. The dynamics of human sperm droplets on a liquid crystal and polymer composite film

    NASA Astrophysics Data System (ADS)

    Lu, Farn; Lin, Yi-Hsin; Tsai, Wan-Chen; Li, Jiong-Juan; Chu, Ting-Yu; Hsu, Hsu-Kuan; Li, Wang-Yang

    2010-02-01

    A switchable surface using a liquid crystal and polymer composite film (LCPCF) based on phase separation between liquid crystals (LC) and polymers after photopolymerization is developed recently. The wettability of LCPCF is electrically tunable because of the orientation of liquid crystal directors anchored among the polymer grains under an in-planed electric field. A water droplet on the top of LCPCF can be manipulated under an inhomogeneous electric field on the LCPCF owning to the wettability gradient. The dynamics of a droplet of human sperms on the LCPCF is demonstrated as well. Three motions of sperm droplets are observed: the droplet collapse and the droplet stretch,. We found that the dynamics, concentrations, and activities of spermatozoa, affect the motions of a sperm droplet. The potential applications of LCPCF are polarizer-free displays, liquid lenses, and the microfluidic device in assisted reproductive technology (ART)

  7. Effect of droplet size distribution on reaction heat in a liquid-liquid heterogeneous reaction process.

    PubMed

    Yasuhiro, Fujimoto

    2004-11-11

    In heterogeneous liquid-liquid reaction processes, explosions have been reported. An aim of this study is to simulate the accident stories, which might be caused by inappropriate mixing conditions in the heterogeneous reaction process. The reaction of water-insoluble anhydride and water was selected as a model process. The experimental trend data of droplet size with agitation in a batch reactor were fitted to an empirical equation. The good fittings show the applicability of the equation in our reaction conditions.

  8. Optical biosensor based on liquid crystal droplets for detection of cholic acid

    NASA Astrophysics Data System (ADS)

    Niu, Xiaofang; Luo, Dan; Chen, Rui; Wang, Fei; Sun, Xiaowei; Dai, Haitao

    2016-12-01

    A highly sensitive cholic acid biosensor based on 4-cyano-4‧-penthlbiphenyl (5CB) Liquid crystal droplets in phosphate buffer saline solution was reported. A radial-to-bipolar transition of 5CB droplet would be triggered during competitive reaction of CA at the sodium dodecyl sulfate surfactant-laden 5CB droplet surface. Our liquid crystal droplet sensor is a low-cost, simple and fast method for CA detection. The detection limit (5 μM) of our method is 2.4 times lower than previously report by using liquid crystal film to detection of CA.

  9. 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.

  10. Ignition of an organic water-coal fuel droplet floating in a heated-air flow

    NASA Astrophysics Data System (ADS)

    Valiullin, T. R.; Strizhak, P. A.; Shevyrev, S. A.; Bogomolov, A. R.

    2017-01-01

    Ignition of an organic water-coal fuel (CWSP) droplet floating in a heated-air flow has been studied experimentally. Rank B2 brown-coal particles with a size of 100 μm, used crankcase Total oil, water, and a plasticizer were used as the main CWSP components. A dedicated quartz-glass chamber has been designed with inlet and outlet elements made as truncated cones connected via a cylindrical ring. The cones were used to shape an oxidizer flow with a temperature of 500-830 K and a flow velocity of 0.5-5.0 m/s. A technique that uses a coordinate-positioning gear, a nichrome thread, and a cutter element has been developed for discharging CWSP droplets into the working zone of the chamber. Droplets with an initial size of 0.4 to 2.0 mm were used. Conditions have been determined for a droplet to float in the oxidizer flow long enough for the sustainable droplet burning to be initiated. Typical stages and integral ignition characteristics have been established. The integral parameters (ignition-delay times) of the examined processes have been compared to the results of experiments with CWSP droplets suspended on the junction of a quick-response thermocouple. It has been shown that floating fuel droplets ignite much quicker than the ones that sit still on the thermocouple due to rotation of an CWSP droplet in the oxidizer flow, more uniform heating of the droplet, and lack of heat drainage towards the droplet center. High-speed video recording of the peculiarities of floatation of a burning fuel droplet makes it possible to complement the existing models of water-coal fuel burning. The results can be used for a more substantiated modeling of furnace CWSP burning with the ANSYS, Fluent, and Sigma-Flow software packages.

  11. Method and system for low-NO.sub.x dual-fuel combustion of liquid and/or gaseous fuels

    SciTech Connect

    Gard, Vincent; Chojnacki, Dennis A; Rabovitser, Ioseph K

    2014-12-02

    A method and apparatus for combustion in which a pressurized preheated liquid fuel is atomized and a portion thereof flash vaporized, creating a mixture of fuel vapor and liquid droplets. The mixture is mixed with primary combustion oxidant, producing a fuel/primary oxidant mixture which is then injected into a primary combustion chamber in which the fuel/primary oxidant mixture is partially combusted, producing a secondary gaseous fuel containing hydrogen and carbon oxides. The secondary gaseous fuel is mixed with a secondary combustion oxidant and injected into the second combustion chamber wherein complete combustion of the secondary gaseous fuel is carried out. The resulting second stage flue gas containing very low amounts of NO.sub.x is then vented from the second combustion chamber.

  12. Low contaminant formic acid fuel for direct liquid fuel cell

    DOEpatents

    Masel, Richard I.; Zhu, Yimin; Kahn, Zakia; Man, Malcolm

    2009-11-17

    A low contaminant formic acid fuel is especially suited toward use in a direct organic liquid fuel cell. A fuel of the invention provides high power output that is maintained for a substantial time and the fuel is substantially non-flammable. Specific contaminants and contaminant levels have been identified as being deleterious to the performance of a formic acid fuel in a fuel cell, and embodiments of the invention provide low contaminant fuels that have improved performance compared to known commercial bulk grade and commercial purified grade formic acid fuels. Preferred embodiment fuels (and fuel cells containing such fuels) including low levels of a combination of key contaminants, including acetic acid, methyl formate, and methanol.

  13. Process for vaporizing a liquid hydrocarbon fuel

    DOEpatents

    Szydlowski, Donald F.; Kuzminskas, Vaidotas; Bittner, Joseph E.

    1981-01-01

    The object of the invention is to provide a process for vaporizing liquid hydrocarbon fuels efficiently and without the formation of carbon residue on the apparatus used. The process includes simultaneously passing the liquid fuel and an inert hot gas downwardly through a plurality of vertically spaed apart regions of high surface area packing material. The liquid thinly coats the packing surface, and the sensible heat of the hot gas vaporizes this coating of liquid. Unvaporized liquid passing through one region of packing is uniformly redistributed over the top surface of the next region until all fuel has been vaporized using only the sensible heat of the hot gas stream.

  14. Trace Material Capture by Controlled Liquid Droplets on a Superhydrophobic/Hydrophilic Surface.

    PubMed

    Fukada, Kenta; Kawamura, Naoya; Shiratori, Seimei

    2017-09-15

    A liquid droplet in contact with a superhydrophobic surface can be used to collect dissolved trace materials after evaporating the solvent. This process effect enhances detection limits, but a liquid droplet easily rolls off a superhydrophobic surface. Keeping it at a specific collecting spot area is challenging. Here the means for controlling and capturing a liquid droplet on a superhydrophobic surface is demonstrated. To induce a liquid droplet to a collecting spot, its rolling direction was controlled by two superhydrophobic fabric guides. The liquid droplet was then captured by hydrophilic polymer and hydrophilic nanoparticles at the measuring spot. After removing the solvent, the trace compounds were evaluated with a colorimetric analysis visible to the naked eye.

  15. Single fiber optical trapping of a liquid droplet and its application in microresonator

    NASA Astrophysics Data System (ADS)

    Liu, Zhihai; Chen, Yunhao; Zhao, Li; Zhang, Yu; Wei, Yong; Zhu, Zongda; Yang, Jun; Yuan, Libo

    2016-12-01

    We propose and demonstrate an optical trapping of a liquid droplet and its application based on an annular core microstructured optical fiber. We grind and polish the annular core fiber tip to be a special frustum cone shape to make sure the optical force large enough to trap the liquid droplet non-intrusively. The axial and transverse optical trapping forces are simulated. In addition, we investigate the whispering gallery modes resonance characteristic of the trapped liquid droplet as the example of applications. The whispering gallery modes spectrum is sensitive to the size of the micro liquid droplet. Due to the simple construction and flexible manipulation, the fiber-based optical trapping technology for micro liquid droplets trapping, manipulating, and controlling has great application penitential in many fields, such as physics, biology, and interdisciplinary studies.

  16. Slippery Liquid-Infused Porous Surfaces and Droplet Transportation by Surface Acoustic Waves

    NASA Astrophysics Data System (ADS)

    Luo, J. T.; Geraldi, N. R.; Guan, J. H.; McHale, G.; Wells, G. G.; Fu, Y. Q.

    2017-01-01

    On a solid surface, a droplet of liquid will stick due to the capillary adhesion, and this causes low droplet mobility. To reduce contact line pinning, surface chemistry can be coupled to micro- and/or nanostructures to create superhydrophobic surfaces on which a droplet balls up into an almost spherical shape, thus, minimizing the contact area. Recent progress in soft matter has now led to alternative lubricant-impregnated surfaces capable of almost zero contact line pinning and high droplet mobility without causing droplets to ball up and minimize the contact area. Here we report an approach to surface-acoustic-wave- (SAW) actuated droplet transportation enabled using such a surface. These surfaces maintain the contact area required for efficient energy and momentum transfer of the wave energy into the droplet while achieving high droplet mobility and a large footprint, therefore, reducing the threshold power required to induce droplet motion. In our approach, we use a slippery layer of lubricating oil infused into a self-assembled porous hydrophobic layer, which is significantly thinner than the SAW wavelength, and avoid damping of the wave. We find a significant reduction (up to 85%) in the threshold power for droplet transportation compared to that using a conventional surface-treatment method. Moreover, unlike droplets on superhydrophobic surfaces, where interaction with the SAW induces a transition from a Cassie-Baxter state to a Wenzel state, the droplets on our liquid-impregnated surfaces remain in a mobile state after interaction with the SAW.

  17. 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.

  18. Droplet Combustion Experiment (DCE)

    NASA Technical Reports Server (NTRS)

    Haggard, John B., Jr.; Nayagan, Vedha; Dryer, Frederick L.; Williams, Forman A.

    1998-01-01

    The first space-based experiments were performed on the combustion of free, individual liquid fuel droplets in oxidizing atmospheres. The fuel was heptane, with initial droplet diameters ranging about from 1 mm to 4 mm. The atmospheres were mixtures of helium and oxygen, at pressures of 1.00, 0.50 and 0.25 bar, with oxygen mole fractions between 20% and 40%, as well as normal Spacelab cabin air. The temperatures of the atmospheres and of the initial liquid fuel were nominally 300 K. A total of 44 droplets were burned successfully on the two flights, 8 on the shortened STS-83 mission and 36 on STS-94. The results spanned the full range of heptane droplet combustion behavior, from radiative flame extinction at larger droplet diameters in the more dilute atmospheres to diffusive extinction in the less dilute atmospheres, with the droplet disappearing prior to flame extinction at the highest oxygen concentrations. Quasisteady histories of droplet diameters were observed along with unsteady histories of flame diameters. New and detailed information was obtained on burning rates, flame characteristics and soot behavior. The results have motivated new computational and theoretical investigations of droplet combustion, improving knowledge of the chemical kinetics, fluid mechanics and heat and mass transfer processes involved in burning liquid fuels.

  19. Optimal wrapping of liquid droplets with ultrathin sheets.

    PubMed

    Paulsen, Joseph D; Démery, Vincent; Santangelo, Christian D; Russell, Thomas P; Davidovitch, Benny; Menon, Narayanan

    2015-12-01

    Elastic sheets offer a path to encapsulating a droplet of one fluid in another that is different from that of traditional molecular or particulate surfactants. In wrappings of fluids by sheets of moderate thickness with petals designed to curl into closed shapes, capillarity balances bending forces. Here, we show that, by using much thinner sheets, the constraints of this balance can be lifted to access a regime of high sheet bendability that brings three major advantages: ultrathin sheets automatically achieve optimally efficient shapes that maximize the enclosed volume of liquid for a fixed area of sheet; interfacial energies and mechanical properties of the sheet are irrelevant within this regime, thus allowing for further functionality; and complete coverage of the fluid can be achieved without special sheet designs. We propose and validate a general geometric model that captures the entire range of this new class of wrapped and partially wrapped shapes.

  20. Liquid trampolines: droplets and spheres bouncing off soap films

    NASA Astrophysics Data System (ADS)

    Courbin, Laurent; Dubail, Jerome; Crotiere, Suzie; Quere, David

    2005-11-01

    We report on the impact of rigid spheres and liquid droplets on soap films. These systems exhibit a rich variety of dynamics including bouncing and adhesion. In the case of drop impact, at low speeds the drops bounce, while for intermediate speeds the drops can pass through the film without the film breaking. The bouncing can be analyzed using mechanical models. In the case of the impact of rigid spheres, by tuning the physical property of the surface of the impacting sphere, which may or may not be surrounded by a skin of oil, we experimentally observe two distinct regimes: the solid sphere can bounce off of the fluid film or get entrapped. In all cases the film can be considered an absorber of kinetic energy. Finally, the possibility of tuning the bounce of an object will be presented.

  1. Liquid-propellant droplet vaporization and combustion in high pressure environments

    NASA Technical Reports Server (NTRS)

    Yang, Vigor

    1991-01-01

    In order to correct the deficiencies of existing models for high-pressure droplet vaporization and combustion, a fundamental investigation into this matter is essential. The objective of this research are: (1) to acquire basic understanding of physical and chemical mechanisms involved in the vaporization and combustion of isolated liquid-propellant droplets in both stagnant and forced-convective environments; (2) to establish droplet vaporization and combustion correlations for the study of liquid-propellant spray combustion and two-phase flowfields in rocket motors; and (3) to investigate the dynamic responses of multicomponent droplet vaporization and combustion to ambient flow oscillations.

  2. Rebound of continuous droplet streams from an immiscible liquid pool

    NASA Astrophysics Data System (ADS)

    Doak, William J.; Laiacona, Danielle M.; German, Guy K.; Chiarot, Paul R.

    2016-05-01

    We report on the rebound of high velocity continuous water droplet streams from the surface of an immiscible oil pool. The droplets have diameters and velocities of less than 90 μm and 15 m/s, respectively, and were created at frequencies up to 60 kHz. The impact and rebound of continuous droplet streams at this scale and velocity have been largely unexplored. This regime bridges the gap between single drop and jet impacts. The impinging droplets create a divot at the surface of the oil pool that had a common characteristic shape across a wide-range of droplet and oil properties. After impact, the reflected droplets maintain the same uniformity and periodicity of the incoming droplets but have significantly lower velocity and kinetic energy. This was solely attributed to the generation of a flow induced in the viscous oil pool by the impacting droplets. Unlike normally directed impact of millimeter-scale droplets with a solid surface, our results show that an air film does not appear to be maintained beneath the droplets during impact. This suggests direct contact between the droplets and the surface of the oil pool. A ballistic failure limit, correlated with the Weber number, was identified where the rebound was suppressed and the droplets were driven through the oil surface. A secondary failure mode was identified for aperiodic incoming streams. Startup effects and early time dynamics of the rebounding droplet stream were also investigated.

  3. 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%.

  4. Experimental Study of Nonane and Nonane/Hexanol Fuel Droplet Combustion in Microgravity

    NASA Technical Reports Server (NTRS)

    Avedisian, C. T.; Callahan, B. J.

    1999-01-01

    In this presentation we review experiments carried out on nonane droplets, and a nonane/hexanol droplet, burning in microgravity to promote spherical symmetry. The nonane/hexanol combination was selected for the following reasons: 1) the spherically symmetric burning history of nonane and nonane/hexanol mixtures has not been previously studied; 2) measurements of the burning history of pure nonane droplets in air extend the existing data base of spherical droplet flames of soot-producing fuels which are useful for testing detailed chemical kinetic models of the spherically symmetric droplet burning process; 3) nonane and hexanol have almost identical boiling points so heterogeneous nucleation on a support fiber is unlikely; 4) hexanol does not have a strong propensity for water vapor absorption; 5) hexanol produces less soot than nonane so that mixtures of nonane and hexanol should show an effect of composition on soot formation. The far-field gas was atmospheric pressure air at room temperature. The evolution of droplet diameter was measured using high speed cine photography of spark-ignited droplets within a confined volume in a drop tower. The importance of soot formation during droplet combustion is derived from the fact that soot is the basic component of the particulate emission process that occurs in spray combustion. The complexity of soot formation motivates a one-dimensional transport condition which is advantageous for modeling. Recent numerical studies of droplet combustion have assumed spherical symmetry when incorporating such aspects as detailed chemistry and radiation, though soot formation itself has not yet been included in any droplet combustion modeling effort. If radiation is not important as would be the case for'small' droplets (i.e., droplets with initial diameters less than about ]mm), soot formation can lead to a nonlinear burning process and a time-varying burning rate, (non-linear burning of a non-sooting fuel like methanol is due to

  5. Experimental Study of Nonane and Nonane/Hexanol Fuel Droplet Combustion in Microgravity

    NASA Technical Reports Server (NTRS)

    Avedisian, C. T.; Callahan, B. J.

    1999-01-01

    In this presentation we review experiments carried out on nonane droplets, and a nonane/hexanol droplet, burning in microgravity to promote spherical symmetry. The nonane/hexanol combination was selected for the following reasons: 1) the spherically symmetric burning history of nonane and nonane/hexanol mixtures has not been previously studied; 2) measurements of the burning history of pure nonane droplets in air extend the existing data base of spherical droplet flames of soot-producing fuels which are useful for testing detailed chemical kinetic models of the spherically symmetric droplet burning process; 3) nonane and hexanol have almost identical boiling points so heterogeneous nucleation on a support fiber is unlikely; 4) hexanol does not have a strong propensity for water vapor absorption; 5) hexanol produces less soot than nonane so that mixtures of nonane and hexanol should show an effect of composition on soot formation. The far-field gas was atmospheric pressure air at room temperature. The evolution of droplet diameter was measured using high speed cine photography of spark-ignited droplets within a confined volume in a drop tower. The importance of soot formation during droplet combustion is derived from the fact that soot is the basic component of the particulate emission process that occurs in spray combustion. The complexity of soot formation motivates a one-dimensional transport condition which is advantageous for modeling. Recent numerical studies of droplet combustion have assumed spherical symmetry when incorporating such aspects as detailed chemistry and radiation, though soot formation itself has not yet been included in any droplet combustion modeling effort. If radiation is not important as would be the case for'small' droplets (i.e., droplets with initial diameters less than about ]mm), soot formation can lead to a nonlinear burning process and a time-varying burning rate, (non-linear burning of a non-sooting fuel like methanol is due to

  6. Phenomenology of break-up modes in contact free externally heated nanoparticle laden fuel droplets

    NASA Astrophysics Data System (ADS)

    Pathak, Binita; Basu, Saptarshi

    2016-12-01

    We study thermally induced atomization modes in contact free (acoustically levitated) nanoparticle laden fuel droplets. The initial droplet size, external heat supplied, and suspended particle concentration (wt. %) in droplets govern the stability criterion which ultimately determines the dominant mode of atomization. Pure fuel droplets exhibit two dominant modes of breakup namely primary and secondary. Primary modes are rather sporadic and normally do not involve shape oscillations. Secondary atomization however leads to severe shape deformations and catastrophic intense breakup of the droplets. The dominance of these modes has been quantified based on the external heat flux, dynamic variation of surface tension, acoustic pressure, and droplet size. Addition of particles alters the regimes of the primary and secondary atomization and introduces bubble induced boiling and bursting. We analyze this new mode of atomization and estimate the time scale of bubble growth up to the point of bursting using energy balance to determine the criterion suitable for parent droplet rupture. All the three different modes of breakup have been well identified in a regime map determined in terms of Weber number and the heat utilization rate which is defined as the energy utilized for transient heating, vaporization, and boiling in droplets.

  7. Generation of Monodisperse Liquid Droplets in a Microfluidic Chip Using a High-Speed Gaseous Microflow

    NASA Astrophysics Data System (ADS)

    Tirandazi, Pooyan; Hidrovo, Carlos

    2015-11-01

    Over the last few years, microfluidic systems known as Lab-on-a-Chip (LOC) and micro total analysis systems (μTAS) have been increasingly developed as essential components for numerous biochemical applications. Droplet microfluidics, however, provides a distinctive attribute for delivering and processing discrete as well as ultrasmall volumes of fluid, which make droplet-based systems more beneficial over their continuous-phase counterparts. Droplet generation in its conventional scheme usually incorporates the injection of a liquid (water) into a continuous immiscible liquid (oil) medium. In this study we demonstrate a novel scheme for controlled generation of monodisperse droplets in confined gas-liquid microflows. We experimentally investigate the manipulation of water droplets in flow-focusing configurations using a high inertial air stream. Different flow regimes are observed by varying the gas and liquid flow rates, among which, the ``dripping regime'' where monodisperse droplets are generated is of great importance. The controlled size and generation rate of droplets in this region provide the capability for precise and contaminant-free delivery of microliter to nanoliter volumes of fluid. Furthermore, the high speed droplets generated in this method represent the basis for a new approach based on droplet pair collisions for fast efficient micromixing which provides a significant development in modern LOC and μTAS devices. This project is currently being supported by an NSF CAREER Award grant CBET-1151091.

  8. Modeling of movement of liquid metal droplets driven by an electric field.

    PubMed

    Wang, M F; Jin, M J; Jin, X J; Zuo, S G

    2017-07-19

    The motion of liquid metal has potential applications ranging from micro-pumps and self-fueled motors to rapid cooling and drug delivery. In this study, we systematically investigate the effects of the radius of LMDs (liquid metal droplets), the concentration of electrolyte solution and the applied electric field on the movement behavior of LMDs experimentally. The research also explains the experimental phenomenon with an innovative modeling analysis, which combines pertinent forces (i.e., the driving force induced by the gradient of surface tension, the viscous friction between the droplet and its surrounding electrolyte, and the friction between the droplet and the substrate). The model is highly consistent with the rule that LMDs with a larger radius need smaller actuation voltage, and we can predict the critical voltages of LMDs with r = 2-4 mm through Velectrode = 30.62/r(2) - 0.998, which is obtained by fitting the parameters. We also obtain the model V = [-66.2Vr(2)/(259.7-17.7) + 1.253]r(2), which can predict the average velocity-voltage lines of LMDs with r = 3, 3.5 mm and V = 1-13 V. In addition, the velocity increases upon increasing the concentration of the electrolyte solution from 0.1 mol L(-1) to 0.3 mol L(-1), and tends to be stable at more than 0.3 mol L(-1) owing to the saturation of the EDL (electrical double layer) charge density. Additionally, we discuss the phenomenon of elongation during movement that occurs upon increasing the size of the LMDs. If the size of the LMDs continues to increase, the reverse movement from the anode to the cathode can occur, and the phenomenon can also be explained by the model.

  9. Validated Numerical Models for the Convective Extinction of Fuel Droplets (CEFD)

    NASA Technical Reports Server (NTRS)

    Gogos, George; Bowen, Brent; Nickerson, Jocelyn S.

    2002-01-01

    The NASA Nebraska Space Grant (NSGC) & EPSCoR programs have continued their effort to support outstanding research endeavors by funding the Numerical Simulation of the Combustion of Fuel Droplets study at the University of Nebraska at Lincoln (UNL). This team of researchers has developed a transient numerical model to study the combustion of suspended and moving droplets. The engines that propel missiles, jets, and many other devices are dependent upon combustion. Therefore, data concerning the combustion of fuel droplets is of immediate relevance to aviation and aeronautical personnel, especially those involved in flight operations. The experiments being conducted by Dr. Gogos and Dr. Nayagam s research teams, allow investigators to gather data for comparison with theoretical predictions of burning rates, flame structures, and extinction conditions. The consequent improved fundamental understanding of droplet combustion may contribute to the clean and safe utilization of fossil fuels (Williams, Dryer, Haggard & Nayagam, 1997, f 2). The present state of knowledge on convective extinction of fuel droplets derives from experiments conducted under normal gravity conditions. However, any data obtained with suspended droplets under normal gravity are grossly affected by gravity. The need to obtain experimental data under microgravity conditions is therefore well justified and addresses one of the goals of NASA's Human Exploration and Development of Space (HEDS) microgravity combustion experiment.

  10. Investigation of Sooting in Microgravity Droplet Combustion: Fuel-Dependent Effects

    NASA Technical Reports Server (NTRS)

    Manzello, Samuel L.; Hua, Ming; Choi, Mun Young

    1999-01-01

    Kumagai and coworkers first performed microgravity droplet combustion experiments [Kumagai, 1957]. The primary goal of these early experiments were to validate simple 'd(sup 2)-law models [Spalding, 1954, Godsave, 1954] Inherent in the 'd(sup 2) -law' formulation and in the scope of the experimental observation is the neglect of sooting behavior. In fact, the influence of sooting has not received much attention until more recent works [Choi et al., 1990; Jackson et al., 1991; Jackson and Avedisian, 1994; Choi and Lee, 1996; Jackson and Avedisian, 1996; Lee et al., 1998]:. Choi and Lee measured soot volume fraction for microgravity droplet flames using full-field light extinction and subsequent tomographic inversion [Choi and Lee, 1996]. In this investigation, soot concentrations were measured for heptane droplets and it was reported that soot concentrations were considerably higher in microgravity compared to the normal gravity flame. It was reasoned that the absence of buoyancy and the effects of thermophoresis resulted in the higher soot concentrations. Lee et al. [1998] performed soot measurement experiments by varying the initial droplet diameter and found marked influence of sooting on the droplet burning behavior. There is growing sentiment that sooting in droplet combustion must no longer be neglected and that "perhaps one of the most important outstanding contributions of (micro)g droplet combustion is the observation that in the absence of asymmetrical forced and natural convection, a soot shell is formed between the droplet surface and the flame, exerting an influence on the droplet combustion response far greater than previously recognized." [Law and Faeth, 1994]. One of the methods that we are exploring to control the degree of sooting in microgravity is to use different fuels. The effect of fuel structure on sooting propensity has been investigated for over-ventilated concentric coflowing buoyant diffusion flames. (Glassman, 1996]. In these

  11. Surfing liquid metal droplet on the same metal bath via electrolyte interface

    NASA Astrophysics Data System (ADS)

    Zhao, Xi; Tang, Jianbo; Liu, Jing

    2017-09-01

    We report a phenomenon that when exerting an electric field gradient across a liquid metal/electrolyte interface, a droplet of the same liquid metal can persistently surf on the interface without coalescence. A thin layer of the intermediate solution, which separates the droplet from direct metallic contacting and provides levitating force, is responsible for such surfing effect. The electric resistance of this solution film is measured, and the film thickness is further theoretically calculated. The fact that the levitating state can be switched on and off via a controlled manner paves the way for reliably manipulating liquid metal droplets or devices.

  12. Dynamics of volatile liquid droplets on heated surfaces: theory versus experiment

    NASA Astrophysics Data System (ADS)

    Sodtke, Christof; Ajaev, Vladimir S.; Stephan, Peter

    We consider the evaporation of volatile liquid droplets deposited on a heated substrate in a pure saturated vapour environment. A mathematical model is developed that incorporates the effects of surface tension, evaporation, thermocapillarity, gravity, disjoining pressure, as well as unsteady heat conduction in the solid substrate. The apparent contact line is treated mathematically as a transition region between the macroscopic droplet shape and the adsorbed film of liquid on the heated substrate. Theoretical parametric studies are conducted to clarify the effects of thermocapillarity and wetting properties on the droplet dynamics. An experimental study is conducted in a closed container with de-ionized water droplets on a stainless steel foil heated by an electric current. The interface shapes are recorded together with the temperature profiles under the droplets, measured using thermochromic liquid crystals. Experiment and theory are in very good agreement as long as the conditions of applicability of our lubrication-type mathematical model are satisfied.

  13. Numerical study of droplet dynamics in a polymer electrolyte fuel cell gas channel using an embedded Eulerian-Lagrangian approach

    NASA Astrophysics Data System (ADS)

    Jarauta, Alex; Ryzhakov, Pavel; Secanell, Marc; Waghmare, Prashant R.; Pons-Prats, Jordi

    2016-08-01

    An embedded Eulerian-Lagrangian formulation for the simulation of droplet dynamics within a polymer electrolyte fuel cell (PEFC) channel is presented. Air is modeled using an Eulerian formulation, whereas water is described with a Lagrangian framework. Using this framework, the gas-liquid interface can be accurately identified. The surface tension force is computed using the curvature defined by the boundary of the Lagrangian mesh. The method naturally accounts for material property changes across the interface and accurately represents the pressure discontinuity. A sessile drop in a horizontal surface, a sessile drop in an inclined plane and droplets in a PEFC channel are solved for as numerical examples and compared to experimental data. Numerical results are in excellent agreement with experimental data. Numerical results are also compared to results obtained with the semi-analytical model previously developed by the authors in order to discuss the limitations of the semi-analytical approach.

  14. Enhanced water removal in a fuel cell stack by droplet atomization using structural and acoustic excitation

    NASA Astrophysics Data System (ADS)

    Palan, Vikrant; Shepard, W. Steve

    This work examines new methods for enhancing product water removal in fuel cell stacks. Vibration and acoustic based methods are proposed to atomize condensed water droplets in the channels of a bipolar plate or on a membrane electrode assembly (MEA). The vibration levels required to atomize water droplets of different sizes are first examined using two different approaches: (1) exciting the droplet at the same energy level required to form that droplet; and (2) by using a method called 'vibration induced droplet atomization', or VIDA. It is shown analytically that a 2 mm radius droplet resting on a bipolar-like plate can be atomized by inducing acceleration levels as low as 250 g at a certain frequency. By modeling the direct structural excitation of a simplified bipolar plate using a realistic source, the response levels that can be achieved are then compared with those required levels. Furthermore, a two-cell fuel cell finite element model and a boundary element model of the MEA were developed to demonstrate that the acceleration levels required for droplet atomization may be achieved in both the bipolar plate as well as the MEA through proper choice of excitation frequency and source strength.

  15. Combustion of liquid fuels in a flowing combustion gas environment at high pressures

    NASA Technical Reports Server (NTRS)

    Canada, G. S.; Faeth, G. M.

    1975-01-01

    The combustion of fuel droplets in gases which simulate combustion chamber conditions was considered both experimentally and theoretically. The fuel droplets were simulated by porous spheres and allowed to gasify in combustion gases produced by a burner. Tests were conducted for pressures of 1-40 atm, temperatures of 600-1500 K, oxygen concentrations of 0-13% (molar) and approach Reynolds numbers of 40-680. The fuels considered in the tests included methanol, ethanol, propanol-1, n-pentane, n-heptane and n-decane. Measurements were made of both the rate of gasification of the droplet and the liquid surface temperature. Measurements were compared with theory, involving various models of gas phase transport properties with a multiplicative correction for the effect of forced convection.

  16. Diazido alkanes and diazido alkanols as combustion modifiers for liquid hydrocarbon ramjet fuels

    SciTech Connect

    Miller, R.S.

    1986-07-03

    This invention relates to liquid-hydrocarbon jet fuels and more particularly to azido additives to liquid-hydrocarbon ramjet fuels. In most liquid-fueled combustors such as the ramjet, the fuel is directly introduced into the upstream flow section of the combustion chamber in the form of sprays of droplets. These droplets subsequently mix with the external gas, heat up, gasify, combust, and thereby release heat to provide the propulsion energy. It is therefore obvious that the rates of gasification and mixing would closely affect the chemical heat release rate and, consequently, such important performance parameters as combustion efficiency and the tendency to exhibit combustion instability. Accordingly, and object of this invention is to provide a new, improved jet fuel and provide new additives for jet fuels. A further object of this invention is to provide a more-efficient jet fuel and reduce the ignition time for jet fuels. Still, a further object of this invention is to improve the mixing characteristics of the jet-fuel spray.

  17. Direct droplet production from a liquid film: a new gas-assisted atomization mechanism

    NASA Astrophysics Data System (ADS)

    Snyder, Herman E.; Reitz, Rolf D.

    1998-11-01

    X-ray lithography and micro-machining have been used to study gas-assisted liquid atomization in which a liquid film was impinged by a large number of sonic micro-gas jets. Three distinct breakup regimes were demonstrated. Two of these regimes share characteristics with previously observed atomization processes: a bubble bursting at a free surface (Newitt et al. 1954; Boulton-Stone & Blake 1993) and liquid sheet disintegration in a high gas/liquid relative velocity environment (Dombrowski & Johns 1963). The present work shows that suitable control of the gas/liquid interface creates a third regime, a new primary atomization mechanism, in which single liquid droplets are ejected directly from the liquid film without experiencing an intermediate ligament formation stage. The interaction produces a stretched liquid sheet directly above each gas orifice. This effectively pre-films the liquid prior to its breakup. Following this, surface tension contracts the stretched film of liquid into a sphere which subsequently detaches from the liquid sheet and is entrained by the gas jet that momentarily pierces the film. After droplet ejection, the stretched liquid film collapses, covering the gas orifice, and the process repeats. This new mechanism is capable of the efficient creation of finely atomized sprays at low droplet ejection velocities (e.g. 20 [mu]m Sauter mean diameter methanol sprays using air at 239 kPa, with air-to-liquid mass ratios below 1.0, and droplet velocities lower than 2.0 m s[minus sign]1). Independent control of the gas and the liquid flows allows the droplet creation process to be effectively de-coupled from the initial droplet momentum, a characteristic not observed with standard gas-assisted atomization mechanisms.

  18. Liquid Fuels Market Module - NEMS Documentation

    EIA Publications

    2014-01-01

    Defines the objectives of the Liquid Fuels Market Model (LFMM), describes its basic approach, and provides detail on how it works. This report is intended as a reference document for model analysts, users, and the public.

  19. Interactions Between Gaseous Electrical Discharges and Single Liquid Droplets

    NASA Technical Reports Server (NTRS)

    Shaw, B. D.; Dryer, F. L.; Williams, F. A.; Gat, N.

    1988-01-01

    Theoretical estimates and experimental measurements of the effects of sparks on ordered droplet motion are reported for 1-mm-diameter water and hydrocarbon droplets positioned 0.5 mm from the axis of electrodes are reported. The discussion focuses primarily on two-electrode, surge-type spark breakdowns with quasi-steady electric fields applied. Multiple electrode pairs and alternating electric fields and their effects on ordered droplet motion are also briefly discussed.

  20. Microfluidic droplet-based liquid-liquid extraction: online model validation.

    PubMed

    Lubej, Martin; Novak, Uroš; Liu, Mingqiang; Martelanc, Mitja; Franko, Mladen; Plazl, Igor

    2015-05-21

    Droplet-based liquid-liquid extraction in a microchannel was studied, both theoretically and experimentally. A full 3D mathematical model, incorporating convection and diffusion in all spatial directions along with the velocity profile, was developed to depict the governing transport characteristics of droplet-based microfluidics. The finite elements method, as the most common macroscale simulation technique, was used to solve the set of differential equations regarding conservation of moment, mass and solute concentration in a two-domain system coupled by interfacial surface of droplet-based flow pattern. The model was numerically verified and validated online by following the concentrations of a solute in two phases within the microchannel. The relative azobenzene concentration profiles in a methanol/n-octane two-phase system at different positions along the channel length were retrieved by means of a thermal lens microscopic (TLM) technique coupled to a microfluidic system, which gave results of high spatial and temporal resolution. Very good agreement between model calculations and online experimental data was achieved without applying any fitting procedure to the model parameters.

  1. Communication: Orientational structure manipulation in nematic liquid crystal droplets induced by light excitation of azodendrimer dopant

    PubMed Central

    Emelyanenko, Alexander V.; Boiko, Natalia I.; Liu, Jui-Hsiang; Khokhlov, Alexei R.

    2017-01-01

    Reversible orientational transitions in the droplets of a nematic liquid crystal (NLC) caused by the change of boundary conditions under the low intensity diode illumination are investigated. Photosensitivity of NLC is achieved by the addition of the dendrimer compound with azobenzene terminal groups. Two types of NLC droplets in glycerol are considered: the spherical droplets in the bulk of glycerol and the droplets laid-down onto the solid substrate. In the second case, the first order phase transition is revealed. The effects described can be useful for the development of highly sensitive chemical detectors and microsized photo-tunable optical devices. PMID:28595414

  2. Communication: Orientational structure manipulation in nematic liquid crystal droplets induced by light excitation of azodendrimer dopant

    NASA Astrophysics Data System (ADS)

    Shvetsov, Sergey A.; Emelyanenko, Alexander V.; Boiko, Natalia I.; Liu, Jui-Hsiang; Khokhlov, Alexei R.

    2017-06-01

    Reversible orientational transitions in the droplets of a nematic liquid crystal (NLC) caused by the change of boundary conditions under the low intensity diode illumination are investigated. Photosensitivity of NLC is achieved by the addition of the dendrimer compound with azobenzene terminal groups. Two types of NLC droplets in glycerol are considered: the spherical droplets in the bulk of glycerol and the droplets laid-down onto the solid substrate. In the second case, the first order phase transition is revealed. The effects described can be useful for the development of highly sensitive chemical detectors and microsized photo-tunable optical devices.

  3. Finite-difference time-domain analysis of light propagation in cholesteric liquid crystalline droplet array

    NASA Astrophysics Data System (ADS)

    Yamamoto, Kaho; Iwai, Yosuke; Uchida, Yoshiaki; Nishiyama, Norikazu

    2016-08-01

    We numerically analyzed the light propagation in cholesteric liquid crystalline (CLC) droplet array by the finite-difference time-domain (FDTD) method. The FDTD method successfully reproduced the experimental light path observed in the complicated photonic structure of the CLC droplet array more accurately than the analysis of CLC droplets by geometric optics with Bragg condition, and this method help us understand the polarization of the propagating light waves. The FDTD method holds great promise for the design of various photonic devices composed of curved photonic materials like CLC droplets and microcapsules.

  4. Simple and robust resistive dual-axis accelerometer using a liquid metal droplet

    NASA Astrophysics Data System (ADS)

    Huh, Myoung; Won, Dong-Joon; Kim, Joong Gil; Kim, Joonwon

    2017-12-01

    This paper presents a novel dual-axis accelerometer that consists of a liquid metal droplet in a cone-shaped channel and an electrode layer with four Nichrome electrodes. The sensor uses the advantages of the liquid metal droplet (i.e., high surface tension, electrical conductivity, high density, and deformability). The cone-shaped channel imposes a restoring force on the liquid metal droplet. We conducted simulation tests to determine the appropriate design specifications of the cone-shaped channel. Surface modifications to the channel enhanced the nonwetting performance of the liquid metal droplet. The performances of the sensor were analyzed by a tilting test. When the acceleration was applied along the axial direction, the device showed 6 kΩ/g of sensitivity and negligible crosstalk between the X- and Y-axes. In a diagonal direction test, the device showed 4 kΩ/g of sensitivity.

  5. Design of Functional Materials based on Liquid Crystalline Droplets.

    PubMed

    Miller, Daniel S; Wang, Xiaoguang; Abbott, Nicholas L

    2014-01-14

    This brief perspective focuses on recent advances in the design of functional soft materials that are based on confinement of low molecular weight liquid crystals (LCs) within micrometer-sized droplets. While the ordering of LCs within micrometer-sized domains has been explored extensively in polymer-dispersed LC materials, recent studies performed with LC domains with precisely defined size and interfacial chemistry have unmasked observations of confinement-induced ordering of LCs that do not follow previously reported theoretical predictions. These new findings, which are enabled in part by advances in the preparation of LCs encapsulated in polymeric shells, are opening up new opportunities for the design of soft responsive materials based on surface-induced ordering transitions. These materials are also providing new insights into the self-assembly of biomolecular and colloidal species at defects formed by LCs confined to micrometer-sized domains. The studies presented in this perspective serve additionally to highlight gaps in knowledge regarding the ordering of LCs in confined systems.

  6. Design of Functional Materials based on Liquid Crystalline Droplets

    PubMed Central

    Miller, Daniel S.; Wang, Xiaoguang; Abbott, Nicholas L.

    2014-01-01

    This brief perspective focuses on recent advances in the design of functional soft materials that are based on confinement of low molecular weight liquid crystals (LCs) within micrometer-sized droplets. While the ordering of LCs within micrometer-sized domains has been explored extensively in polymer-dispersed LC materials, recent studies performed with LC domains with precisely defined size and interfacial chemistry have unmasked observations of confinement-induced ordering of LCs that do not follow previously reported theoretical predictions. These new findings, which are enabled in part by advances in the preparation of LCs encapsulated in polymeric shells, are opening up new opportunities for the design of soft responsive materials based on surface-induced ordering transitions. These materials are also providing new insights into the self-assembly of biomolecular and colloidal species at defects formed by LCs confined to micrometer-sized domains. The studies presented in this perspective serve additionally to highlight gaps in knowledge regarding the ordering of LCs in confined systems. PMID:24882944

  7. Catalytic Ignition of Ionic Liquid Fuels by Ionic Liquids

    DTIC Science & Technology

    2014-07-01

    Francisco, CA, 10-14 Aug 2014. PA#14360 14. ABSTRACT The majority of current hypergolic ionic liquids (ILs) are hypergolic (spontaneous ignition upon...Ignites ( Hypergolic )  Ignites Fast (᝺ms)  Ignites Fast & Green(er) Objectives for Ionic Liquids as Bipropellant Fuels Image: NASA Distribution...oxidizers Established storable fuel/catalyst IL mixtures First demonstration of ignition of non - hypergolic ILs utilizing IL catalysts in H2O2

  8. Changes in combustion behavior of liquid fuels due to the addition of small amounts of ammonia borane or nano aluminum

    NASA Astrophysics Data System (ADS)

    Pfeil, Mark A.

    Both ammonia borane and nano aluminum as additives to liquid fuels are investigated. Both fundamental droplet combustion experiments and experiments using an unstable liquid rocket combustor are used to study the effects these additives on the combustion behavior. The liquid fuels consist of ethanol and JP-8. The droplet experiments consist of both visual and OH high speed planar laser-induced fluorescence measurements. Simple combustion models are incorporated as well to provide further understanding. It is found that ammonia borane increases the regression rate of a single ethanol droplet. Evidence indicates that hydrogen gas is released throughout the combustion process of the droplet and influences the combustion behavior notably. Laser diagnostics indicate that changes in flame structure occur. The other components of ammonia borane affect the combustion behavior of the droplet, especially near the end of the droplet lifetime, causing the droplet to shatter. Nano aluminum has very little impact on the combustion behavior of single fuel droplets of JP-8 and ethanol. Nano aluminum is observed to combust only when a surfactant, Neodol, is present which produces gas generation and bubble formation within the droplet. Combustor experiments show similar trends as the droplet combustion experiments. Ammonia borane has a notable impact on the combustion stability of the system allowing it to be unstable for more combustor geometries. It is shown that ammonia borane addition produces a bimodal unsteady energy release within the combustor while the neat fuel does not. This combustion behavior allows for the increased amount of unstable combustor geometries. Nano aluminum has a small impact on the combustion stability of the system causing pressure oscillations to increase.

  9. Combustion of liquid fuels in diesel engine

    NASA Technical Reports Server (NTRS)

    Alt, Otto

    1924-01-01

    Hitherto, definite specifications have always been made for fuel oils and they have been classified as more or less good or non-utilizable. The present aim, however, is to build Diesel engines capable of using even the poorest liquid fuels and especially the waste products of the oil industry, without special chemical or physical preparation.

  10. THE LIQUID AND GASEOUS FUEL DISTRIBUTION SYSTEM

    EPA Science Inventory

    The report describes the national liquid and gaseous fuel distribution system. he study leading to the report was performed as part of an effort to better understand emissions of volatile organic compounds from the fuel distribution system. he primary, secondary, and tertiary seg...

  11. THE LIQUID AND GASEOUS FUEL DISTRIBUTION SYSTEM

    EPA Science Inventory

    The report describes the national liquid and gaseous fuel distribution system. he study leading to the report was performed as part of an effort to better understand emissions of volatile organic compounds from the fuel distribution system. he primary, secondary, and tertiary seg...

  12. Marangoni Convection in Evaporating Organic Liquid Droplets on a Nonwetting Substrate.

    PubMed

    Chandramohan, Aditya; Dash, Susmita; Weibel, Justin A; Chen, Xuemei; Garimella, Suresh V

    2016-05-17

    We quantitatively characterize the flow field inside organic liquid droplets evaporating on a nonwetting substrate. A mushroom-structured surface yields the desired nonwetting behavior with methanol droplets, while use of a cooled substrate (5-15 °C) slows the rate of evaporation to allow quasi-static particle image velocimetry. Visualization reveals a toroidal vortex within the droplet that is characteristic of surface tension-driven flow; we demonstrate by means of a scaling analysis that this recirculating flow is Marangoni convection. The velocities in the droplet are on the order of 10-45 mm/s. Thus, unlike in the case of evaporation on wetting substrates where Marangoni convection can be ignored for the purpose of estimating the evaporation rate, advection due to the surface tension-driven flow plays a dominant role in the heat transfer within an evaporating droplet on a nonwetting substrate because of the large height-to-radius aspect ratio of the droplet. We formulate a reduced-order model that includes advective transport within the droplet for prediction of organic liquid droplet evaporation on a nonwetting substrate and confirm that the predicted temperature differential across the height of the droplet matches experiments.

  13. Solidification of floating organic droplet in dispersive liquid-liquid microextraction as a green analytical tool.

    PubMed

    Mansour, Fotouh R; Danielson, Neil D

    2017-08-01

    Dispersive liquid-liquid microextraction (DLLME) is a special type of microextraction in which a mixture of two solvents (an extracting solvent and a disperser) is injected into the sample. The extraction solvent is then dispersed as fine droplets in the cloudy sample through manual or mechanical agitation. Hence, the sample is centrifuged to break the formed emulsion and the extracting solvent is manually separated. The organic solvents commonly used in DLLME are halogenated hydrocarbons that are highly toxic. These solvents are heavier than water, so they sink to the bottom of the centrifugation tube which makes the separation step difficult. By using solvents of low density, the organic extractant floats on the sample surface. If the selected solvent such as undecanol has a freezing point in the range 10-25°C, the floating droplet can be solidified using a simple ice-bath, and then transferred out of the sample matrix; this step is known as solidification of floating organic droplet (SFOD). Coupling DLLME to SFOD combines the advantages of both approaches together. The DLLME-SFOD process is controlled by the same variables of conventional liquid-liquid extraction. The organic solvents used as extractants in DLLME-SFOD must be immiscible with water, of lower density, low volatility, high partition coefficient and low melting and freezing points. The extraction efficiency of DLLME-SFOD is affected by types and volumes of organic extractant and disperser, salt addition, pH, temperature, stirring rate and extraction time. This review discusses the principle, optimization variables, advantages and disadvantages and some selected applications of DLLME-SFOD in water, food and biomedical analysis. Copyright © 2017 Elsevier B.V. All rights reserved.

  14. Liquid-Liquid Phase Equilibria and Interactions between Droplets in Water-in-Oil Microemulsions.

    PubMed

    Yin, Tianxiang; Wang, Mingjie; Tao, Xiaoyi; Shen, Weiguo

    2016-12-20

    The liquid-liquid phase equilibria of [water/sodium bis(2-ethylhexyl)sulfosuccinate (AOT)/n-decane] with the molar ratio w0 of water to AOT being 37.9 and [water/AOT/ethoxylated-2,5,8,11-tetramethyl-6-dodecyne-5,8-diol(Dynol-604)/n-decane] with w0 = 37.9 and the mole fraction α of Dynol-604 in the total surfactants being 0.158 were measured in this study. From the data collected in the critical region, the critical exponent β corresponding to the width of the coexistence curve was determined, which showed good agreement with the 3D-Ising value. A thermodynamic approach based on the Carnahan-Starling-van der Waals type equation was proposed to describe the coexistence curves and to deduce the interaction properties between droplets in the microemulsions. The interaction enthalpies were found to be positive for the studied systems, which evidenced that the entropy effect dominated the phase separations as the temperature increased. The addition of Dynol-604 into the (water/AOT/n-decane) microemulsion resulted in the decrease in the critical temperature and the interaction enthalpy. Combining the liquid-liquid equilibrium data for (water/AOT/n-decane) microemulsions with various w0 values determined previously, it was shown that the interaction enthalpy decreased with w0 and tended to change its sign at low w0, which coincided with the results from the isothermal titration calorimetry investigation. All of these behaviors were interpreted by the effects of entropy and enthalpy and their competition, which resulted from the release of solvent molecules entrapped in the interface of microemulsion droplets and were dependent on the rigidity of the surfactant layers and the size of the droplet.

  15. The Explosive Ejection of Small Droplets From a Liquid-Gas Interface.

    NASA Astrophysics Data System (ADS)

    James, Ashley; Smith, Marc K.; Glezer, Ari

    1996-11-01

    Vibration-induced liquid atomization is a process that occurs when a liquid droplet is placed on a vibrating membrane. When the proper operating conditions are attained, the droplet resonates with the motion of the membrane and explosively bursts into a spray of very small droplets. The process occurs through an instability of the surface wave motion on the free surface of the large droplet set up by the vibration of the underlying surface. We present experimental data on this process that shows how the droplet ejection event depends on the frequency and amplitude of the vibrating surface and on the initial volume of the large liquid droplet. Video images are also presented that show the basic process and some interesting transient behaviors leading to the ejection event. Our current and future experimental and analytical work on this process is directed towards an understanding of the mechanism behind the atomization process, a full characterization of the free surface instability leading to the droplet ejection event, and a knowledge of the size and velocity distributions in the resulting spray. In addition, vibration-induced droplet atomization is the basis of a new design for an evaporative heat transfer cell that is currently under development for micro-gravity applications. Supported by NASA and Georgia Tech.

  16. Cloud Liquid Water, Mean Droplet Radius and Number Density Measurements Using a Raman Lidar

    NASA Technical Reports Server (NTRS)

    Whiteman, David N.; Melfi, S. Harvey

    1999-01-01

    A new technique for measuring cloud liquid water, mean droplet radius and droplet number density is outlined. The technique is based on simultaneously measuring Raman and Mie scattering from cloud liquid droplets using a Raman lidar. Laboratory experiments on liquid micro-spheres have shown that the intensity of Raman scattering is proportional to the amount of liquid present in the spheres. This fact is used as a constraint on calculated Mie intensity assuming a gamma function particle size distribution. The resulting retrieval technique is shown to give stable solutions with no false minima. It is tested using Raman lidar data where the liquid water signal was seen as an enhancement to the water vapor signal. The general relationship of retrieved average radius and number density is consistent with traditional cloud physics models. Sensitivity to the assumed maximum cloud liquid water amount and the water vapor mixing ratio calibration are tested. Improvements to the technique are suggested.

  17. Cloud Liquid Water, Mean Droplet Radius and Number Density Measurements Using a Raman Lidar

    NASA Technical Reports Server (NTRS)

    Whiteman, David N.; Melfi, S. Harvey

    1999-01-01

    A new technique for measuring cloud liquid water, mean droplet radius and droplet number density is outlined. The technique is based on simultaneously measuring Raman and Mie scattering from cloud liquid droplets using a Raman lidar. Laboratory experiments on liquid micro-spheres have shown that the intensity of Raman scattering is proportional to the amount of liquid present in the spheres. This fact is used as a constraint on calculated Mie intensity assuming a gamma function particle size distribution. The resulting retrieval technique is shown to give stable solutions with no false minima. It is tested using Raman lidar data where the liquid water signal was seen as an enhancement to the water vapor signal. The general relationship of retrieved average radius and number density is consistent with traditional cloud physics models. Sensitivity to the assumed maximum cloud liquid water amount and the water vapor mixing ratio calibration are tested. Improvements to the technique are suggested.

  18. Microfluidic droplet trapping array as nanoliter reactors for gas-liquid chemical reaction.

    PubMed

    Zhang, Qingquan; Zeng, Shaojiang; Qin, Jianhua; Lin, Bingcheng

    2009-09-01

    This article presents a simple method for trapping arrays of droplets relying on the designed microstructures of the microfluidic device, and this has been successfully used for parallel gas-liquid chemical reaction. In this approach, the trapping structure is composed of main channel, lateral channel and trapping region. Under a negative pressure, array droplets can be generated and trapped in the microstructure simultaneously, without the use of surfactant and the precise control of the flow velocity. By using a multi-layer microdevice containing the microstructures, single (pH gradient) and multiple gas-liquid reactions (metal ion-NH3 complex reaction) can be performed in array droplets through the transmembrane diffusion of the gas. The droplets with quantitative concentration gradient can be formed by only replacing the specific membrane. The established method is simple, robust and easy to operate, demonstrating the potential of this device for droplet-based high-throughput screening.

  19. Light-directing omnidirectional circularly polarized reflection from liquid-crystal droplets.

    PubMed

    Fan, Jing; Li, Yannian; Bisoyi, Hari Krishna; Zola, Rafael S; Yang, Deng-Ke; Bunning, Timothy J; Weitz, David A; Li, Quan

    2015-02-09

    Constructing and tuning self-organized three-dimensional (3D) superstructures with tailored functionality is crucial in the nanofabrication of smart molecular devices. Herein we fabricate a self-organized, phototunable 3D photonic superstructure from monodisperse droplets of one-dimensional cholesteric liquid crystal (CLC) containing a photosensitive chiral molecular switch with high helical twisting power. The droplets are obtained by a glass capillary microfluidic technique by dispersing into PVA solution that facilitates planar anchoring of the liquid-crystal molecules at the droplet surface, as confirmed by the observation of normal incidence selective circular polarized reflection in all directions from the core of individual droplet. Photoirradiation of the droplets furnishes dynamic reflection colors without thermal relaxation, whose wavelength can be tuned reversibly by variation of the irradiation time. The results provided clear evidence on the phototunable reflection in all directions.

  20. High-resolution liquid patterns via three-dimensional droplet shape control

    NASA Astrophysics Data System (ADS)

    Raj, Rishi; Adera, Solomon; Enright, Ryan; Wang, Evelyn N.

    2014-09-01

    Understanding liquid dynamics on surfaces can provide insight into nature’s design and enable fine manipulation capability in biological, manufacturing, microfluidic and thermal management applications. Of particular interest is the ability to control the shape of the droplet contact area on the surface, which is typically circular on a smooth homogeneous surface. Here, we show the ability to tailor various droplet contact area shapes ranging from squares, rectangles, hexagons, octagons, to dodecagons via the design of the structure or chemical heterogeneity on the surface. We simultaneously obtain the necessary physical insights to develop a universal model for the three-dimensional droplet shape by characterizing the droplet side and top profiles. Furthermore, arrays of droplets with controlled shapes and high spatial resolution can be achieved using this approach. This liquid-based patterning strategy promises low-cost fabrication of integrated circuits, conductive patterns and bio-microarrays for high-density information storage and miniaturized biochips and biosensors, among others.

  1. On the effects of isotropic turbulence on the evaporation rate of a liquid droplet

    NASA Astrophysics Data System (ADS)

    Dodd, Michael; Ferrante, Antonino

    2016-11-01

    Our objective is to explain the effects of isotropic turbulence on the vaporization rate of a liquid droplet in conditions that are relevant to spray combustion applications. To this end, we have performed direct numerical simulation (DNS) of a single droplet in homogeneous isotropic turbulence using the volume-of-fluid method for resolving fully the process of momentum, heat, and mass transfer between the liquid droplet and the gas. The simulations were performed using 10243 grid points. The effect of turbulence on the droplet vaporization rate is investigated by varying the gas-phase Reynolds number based on the Taylor microscale, Reλ. Reλ is increased from 0 to 75 by increasing the r.m.s. velocity of the gas phase while keeping all other physical properties constant. We will present the droplet evaporation rate as a function of turbulence Reynolds number and investigate the physical mechanisms.

  2. A numerical study of thermocapillary migration of a small liquid droplet on a horizontal solid surface

    NASA Astrophysics Data System (ADS)

    Nguyen, Huy-Bich; Chen, Jyh-Chen

    2010-06-01

    In the present study, the transient thermocapillary migration of a small liquid droplet on a horizontal solid surface is numerically investigated. The droplet has a large static contact angle and a high aspect ratio of the maximum height of the droplet to its footprint. The Navier-Stokes and energy equations for both the droplet and surrounding air are solved through the finite element method. The evolution of the isotherms, the flow fields and the contact angle hysteresis are presented. Two asymmetric thermocapillary vortices appear inside the droplet. The variation of the size of the thermocapillary vortex during the migration process causes the speed of the droplet to first increase significantly, and then decrease gradually to approach a constant value. The higher imposed temperature gradient causes the droplet velocity to reach its maximal value earlier and have a higher final speed. If the static contact angle of the droplet is less than (or higher) than 90°, the droplet speed is lower (or higher) since the net thermocapillary momentum in the horizontal direction is diminished (or enhanced) by the presence of capillary force. The present results for the migration velocity and the contact angle hysteresis for a squalane droplet are also in good agreement with the previous experimental results.

  3. Transient Numerical Modeling of the Combustion of Bi-Component Liquid Droplets: Methanol/Water Mixture

    NASA Technical Reports Server (NTRS)

    Marchese, A. J.; Dryer, F. L.

    1994-01-01

    This study shows that liquid mixtures of methanol and water are attractive candidates for microgravity droplet combustion experiments and associated numerical modeling. The gas phase chemistry for these droplet mixtures is conceptually simple, well understood and substantially validated. In addition, the thermodynamic and transport properties of the liquid mixture have also been well characterized. Furthermore, the results obtained in this study predict that the extinction of these droplets may be observable in ground-based drop to tower experiments. Such experiments will be conducted shortly followed by space-based experiments utilizing the NASA FSDC and DCE experiments.

  4. Studies concerning the effect of large droplets creation during fuel atomization

    NASA Astrophysics Data System (ADS)

    Beniuga, Marius; Mihai, Ioan

    2016-12-01

    This paper presents how to form and evolve atomized fuel droplets obtained experimentally for a high wear injector if the injection pressure is below nominal. The emergence and development of large droplet atomization phenomenon in spark-ignition engines are considered an undesirable phenomenon. The presence of large droplets of the atomized fuel leads to the deposition of substances on the surface of the injector nozzle of the spray in the areas of the intake valve and its seat aspects of oxides which give rise to these areas. In addition, there is the possibility of harm in larger quantities than the normal atomization, in which case the operation of the engine and becomes defective. For proper engine operating at the same time ensuring economy, injection equipment must provide a fuel pressure to the maximum prescribed. The article studied how faulty air mixture formation petrol deviations from uniformity is a due injectors waste can generate large drops of fuel. To conduct this study was conducted an experimental stand [1] which allows modification of the duration of injection and its cyclicality. To highlight the injector nozzle wear scans were performed by laser profilometry. Highlighting the large droplets of fuel was performed using rapid shootings.

  5. Behavior of self-propelled acetone droplets in a Leidenfrost state on liquid substrates

    NASA Astrophysics Data System (ADS)

    Janssens, Stoffel D.; Koizumi, Satoshi; Fried, Eliot

    2017-03-01

    It is demonstrated that non-coalescent droplets of acetone can be formed on liquid substrates. The fluid flows around and in an acetone droplet hovering on water are recorded to shed light on the mechanisms which might lead to non-coalescence. For sufficiently low impact velocities, droplets undergo a damped oscillation on the surface of the liquid substrate but at higher velocities clean bounce-off occurs. Comparisons of experimentally observed static configurations of floating droplets to predictions from a theoretical model for a small non-wetting rigid sphere resting on a liquid substrate are made and a tentative strategy for determining the thickness of the vapor layer under a small droplet on a liquid is proposed. This strategy is based on the notion of effective surface tension. The droplets show self-propulsion in straight line trajectories in a manner which can be ascribed to a Marangoni effect. Surprisingly, self-propelled droplets can become immersed beneath the undisturbed water surface. This phenomenon is reasoned to be drag-inducing and might provide a basis for refining observations in previous work.

  6. 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.

  7. Retrieval of order parameters of a monolayer of liquid-crystal droplets with weak anchoring

    SciTech Connect

    Loiko, V. A. Konkolovich, A. V.; Miskevich, A. A.

    2007-10-15

    An optical method is proposed for extracting the order parameters of single-layer polymer-dispersed liquid-crystal film (monolayer) containing bipolar liquid-crystal droplets under weak anchoring conditions. The method is based on an analysis of the coherent transmittance of a monolayer irradiated with a normally incident linearly polarized plane wave. The method is used to retrieve the order parameter of a spherical liquid-crystal droplet and the order parameter of a monolayer consisting of such droplets as functions of the applied electric field. The effect of inaccuracy of the input values of monolayer parameters on the error of retrieval of the order parameters is examined. The method can be used to determine the refractive index of the polymer binder, as well as other parameters of the film. It provides a tool for solving the inverse scattering problem with field-dependent or field-independent droplet order parameter.

  8. Electromechanical model for actuating liquids in a two-plate droplet microfluidic device.

    PubMed

    Chatterjee, Debalina; Shepherd, Heather; Garrell, Robin L

    2009-05-07

    Both conducting and insulating liquids can be actuated in two-plate droplet ("digital") microfluidic devices. Droplet movement is accomplished by applying a voltage across electrodes patterned beneath the dielectric-coated top and bottom plates. This report presents a general electromechanical model for calculating the forces on insulating and conducting liquids in two-plate devices. The devices are modeled as an equivalent circuit in which the dielectric layers and ambient medium (air or oil) are described as capacitors, while the liquid being actuated is described as a resistor and capacitor in parallel. The experimental variables are the thickness and dielectric constant of each layer in the device, the gap between plates, the applied voltage and frequency, and the conductivity of the liquid. The model has been used to calculate the total force acting on droplets of liquids that have been studied experimentally, and to explain the relative ease with which liquids of different conductivities can be actuated. The contributions of the electrowetting (EW) and dielectrophoretic (DEP) forces to droplet actuation have also been calculated. While for conductive liquids the EW force dominates, for dielectric liquids, both DEP and EW contribute, and the DEP force may dominate. The general utility of the model is that it can be used to predict the operating conditions needed to actuate particular liquids in devices of known geometry, and to optimize the design and operating conditions to enable movement of virtually any liquid.

  9. Morphological transitions of liquid droplets on circular surface domains.

    PubMed

    Blecua, Pedro; Brinkmann, Martin; Lipowsky, Reinhard; Kierfeld, Jan

    2009-12-01

    We study morphological transitions of droplets on a structured substrate containing two circular lyophilic domains for arbitrary domain and substrate wettabilities. We derive the stability criterion that at least one of the droplets must be pinned at the domain boundary with a contact angle smaller than (pi)/(2). This determines seven classes of stable or metastable droplet morphologies of the system. We present a complete classification of stability and metastability of these morphologies as a function of three control parameters as provided by the total droplet volume, substrate wettability, and domain wettability. We find different types of morphological transitions at the stability boundaries: (i) depinning transitions of the contact lines, (ii) symmetry-breaking transitions, where the two droplets acquire different volumes, and (iii) dewetting transitions, where one domain dewets and one of the droplets disappears. We find that depinning transitions of two droplets become discontinuous between two universal values of substrate wettability. Furthermore, below a critical domain wettability, one domain always dewets irrespective of the total volume. We discuss experimental realizations and applications of our results for controlled switching between observed wetting morphologies.

  10. Excitation and dynamics of liquid tin micrometer droplet generation

    NASA Astrophysics Data System (ADS)

    Rollinger, B.; Abhari, R. S.

    2016-07-01

    The dynamics of capillary breakup-based droplet generation are studied for an excitation system based on a tunable piezoelectrically actuated oscillating piston, which generates acoustic pressure waves at the dispenser nozzle. First, the non-ideal pressure boundary conditions of droplet breakup are measured using a fast response pressure probe. A structural analysis shows that the axial modes of the excitation system are the main reasons for the resonance peaks in the pressure response. Second, a correlation between the nozzle inlet pressure and the droplet timing jitter is established with the help of experiments and a droplet formation model. With decreasing wave number, the growth rate of the main excitation decreases, while noise contributions with wave numbers with higher growth rates lead to a non-deterministic structure of the droplet train. A highly coherent and monodisperse droplet stream is obtained when the excitation system is tuned to generate high acoustic pressures at the desired operation frequency and when the noise level on the jet is limited. The jet velocity, hence droplet spacing for a set frequency is then adjusted by varying the reservoir pressure, according to the trade-off between lowest wave number and acceptable timing jitter.

  11. Evaporation of Liquid Droplet in Nano and Micro Scales from Statistical Rate Theory.

    PubMed

    Duan, Fei; He, Bin; Wei, Tao

    2015-04-01

    The statistical rate theory (SRT) is applied to predict the average evaporation flux of liquid droplet after the approach is validated in the sessile droplet experiments of the water and heavy water. The steady-state experiments show a temperature discontinuity at the evaporating interface. The average evaporation flux is evaluated by individually changing the measurement at a liquid-vapor interface, including the interfacial liquid temperature, the interfacial vapor temperature, the vapor-phase pressure, and the droplet size. The parameter study shows that a higher temperature jump would reduce the average evaporation flux. The average evaporation flux can significantly be influenced by the interfacial liquid temperature and the vapor-phase pressure. The variation can switch the evaporation into condensation. The evaporation flux is found to remain relative constant if the droplet is larger than a micro scale, while the smaller diameters in nano scale can produce a much higher evaporation flux. In addition, a smaller diameter of droplets with the same liquid volume has a larger surface area. It is suggested that the evaporation rate increases dramatically as the droplet shrinks into nano size.

  12. Application of maximum entropy method for droplet size distribution prediction using instability analysis of liquid sheet

    NASA Astrophysics Data System (ADS)

    Movahednejad, E.; Ommi, F.; Hosseinalipour, S. M.; Chen, C. P.; Mahdavi, S. A.

    2011-12-01

    This paper describes the implementation of the instability analysis of wave growth on liquid jet surface, and maximum entropy principle (MEP) for prediction of droplet diameter distribution in primary breakup region. The early stage of the primary breakup, which contains the growth of wave on liquid-gas interface, is deterministic; whereas the droplet formation stage at the end of primary breakup is random and stochastic. The stage of droplet formation after the liquid bulk breakup can be modeled by statistical means based on the maximum entropy principle. The MEP provides a formulation that predicts the atomization process while satisfying constraint equations based on conservations of mass, momentum and energy. The deterministic aspect considers the instability of wave motion on jet surface before the liquid bulk breakup using the linear instability analysis, which provides information of the maximum growth rate and corresponding wavelength of instabilities in breakup zone. The two sub-models are coupled together using momentum source term and mean diameter of droplets. This model is also capable of considering drag force on droplets through gas-liquid interaction. The predicted results compared favorably with the experimentally measured droplet size distributions for hollow-cone sprays.

  13. Fuel compositions comprising coal-liquid fuel mixture

    SciTech Connect

    Kobayashi, T.; Niimi, H.; Nobe, T.; Wada, T.

    1981-01-20

    The invention provides: a fuel composition comprising 100 parts by weight of a coal-liquid fuel mixture and 0.02 to 1.0 part by weight of at least one additive selected from the group consisting of dibenzylidene sorbitol, ditoluylidene sorbitol, tribenzylidene sorbitol, tritoluylidene sorbitol and hydrogenated castor oil; and a fuel composition comprising 100 parts by weight of a coal-liquid fuel mixture, 0.02 to 1.0 part by weight of at least one additive selected from the group consisting of dibenzylidene sorbitol, ditoluylidene sorbitol, tribenzylidene sorbitol, tritoluylidene sorbitol and hydrogenated castor oil, and 1 to 10 parts by weight of water. The composition shows high stability over a prolonged period of time, preventing the separation into layers of the components.

  14. Combustion characteristics of fuel droplets with addition of nano and micron-sized aluminum particles

    SciTech Connect

    Gan, Yanan; Qiao, Li

    2011-02-15

    The burning characteristics of fuel droplets containing nano and micron-sized aluminum particles were investigated. Particle size, surfactant concentration, and the type of base fluid were varied. In general, nanosuspensions can last much longer than micron suspensions, and ethanol-based fuels were found to achieve much better suspension than n-decane-based fuels. Five distinctive stages (preheating and ignition, classical combustion, microexplosion, surfactant flame, and aluminum droplet flame) were identified for an n-decane/nano-Al droplet, while only the first three stages occurred for an n-decane/micron-Al droplet. For the same solid loading rate and surfactant concentration, the disruption and microexplosion behavior of the micron suspension occurred later with much stronger intensity. The intense droplet fragmentation was accompanied by shell rupture, which caused a massive explosion of particles, and most of them were burned during this event. On the contrary, for the nanosuspension, combustion of the large agglomerate at the later stage requires a longer time and is less complete because of formation of an oxide shell on the surface. This difference is mainly due to the different structure and characteristics of particle agglomerates formed during the early stage, which is a spherical, porous, and more-uniformly distributed aggregate for the nanosuspension, but it is a densely packed and impermeable shell for the micron suspension. A theoretical analysis was then conducted to understand the effect of particle size on particle collision mechanism and aggregation rate. The results show that for nanosuspensions, particle collision and aggregation are dominated by the random Brownian motion. For micron suspensions, however, they are dominated by fluid motion such as droplet surface regression, droplet expansion resulting from bubble formation, and internal circulation. And the Brownian motion is the least important. This theoretical analysis explains the

  15. Estimates of Liquid Species Diffusivities in N-Propanol/Glycerol Mixture Droplets Burning in Reduced Gravity

    NASA Astrophysics Data System (ADS)

    Vang, C. L.; Shaw, B. D.

    2015-07-01

    Results from International Space Station experiments on combustion of n-propanol/glycerol droplets are reported. The initial n-propanol mass fraction was 0.95 and droplets had initial diameters in the 2 - 5 mm range. Some droplets were fiber supported while others were free floating, and the environment was either an oxygen/nitrogen mixture at 1 atm or an oxygen/helium mixture at pressures of 1 and 3 atm. The droplets burned in a multi-stage manner where n-propanol was preferentially evaporated during the early stages of combustion. The resulting buildup of glycerol in the liquid at the droplet surface led to sudden droplet heating and flame contraction. The experimental data are evaluated to provide burning rates, radiometer outputs, and droplet diameters as functions of time. These data are used to calculate effective liquid species diffusivities, D, using asymptotic theory. The D values can be substantially larger than molecular diffusivities in some cases, indicative of the presence of strong convective mixing. It was found that support fibers can decrease D values and that high burning rates can substantially increase D. These variations are attributed to changes in droplet internal flow patterns.

  16. Effect of a Surrounding Liquid Environment on the Electrical Disruption of Pendant Droplets.

    PubMed

    Mohamed, A Said; Lopez-Herrera, Jose M; Herrada, Miguel A; Modesto-Lopez, Luis B; Gañán-Calvo, Alfonso M

    2016-07-12

    The effect of a surrounding, dielectric, liquid environment on the dynamics of a suddenly electrified liquid drop is investigated both numerically and experimentally. The onset of stability of the droplet is naturally dictated by a threshold value of the applied electric field. While below that threshold the droplet retains its integrity, reaching to a new equilibrium state through damped oscillations (subcritical regime), above it electrical disruption takes place (supercritical regime). In contrast to the oscillation regime, the dynamics of the electric droplet disruption in the supercritical regime reveals a variety of modes. Depending on the operating parameters and fluid properties, a drop in the supercritical regime may result in the well-known tip streaming mode (with and without whipping instability), in droplet splitting (splitting mode), or in the development of a steep shoulder at the elongating front of the droplet that expands radially in a sort of "splashing" (splashing mode). In both splitting and splashing modes, the sizes of the progeny droplets, generated after the breakup of the mother droplet, are comparable to that of the mother droplet. Furthermore, the development in the emission process of the shoulder leading to the splashing mode is described as a parametrical bifurcation, and the parameter governing that bifurcation has been identified. Physical analysis confirms the unexpected experimental finding that the viscosity of the dynamically active environment is absent in the governing parameter. However, the appearance of the splitting mode is determined by the viscosity of the outer environment, when that viscosity overcomes a certain large value. These facts point to the highly nonlinear character of the drop fission process as a function of the droplet volume, inner and outer liquid viscosities, and applied electric field. These observations may have direct implications in systems where precise control of the droplet size is critical, such

  17. The liquid droplet radiator - An ultralightweight heat rejection system for efficient energy conversion in space

    NASA Technical Reports Server (NTRS)

    Mattick, A. T.; Hertzberg, A.

    1981-01-01

    A heat rejection system for space is described which uses a recirculating free stream of liquid droplets in place of a solid surface to radiate waste heat. By using sufficiently small droplets (less than about 100 micron diameter) of low vapor pressure liquids (tin, tin-lead-bismuth eutectics, vacuum oils) the radiating droplet sheet can be made many times lighter than the lightest solid surface radiators (heat pipes). The liquid droplet radiator (LDR) is less vulnerable to damage by micrometeoroids than solid surface radiators, and may be transported into space far more efficiently. Analyses are presented of LDR applications in thermal and photovoltaic energy conversion which indicate that fluid handling components (droplet generator, droplet collector, heat exchanger, and pump) may comprise most of the radiator system mass. Even the unoptimized models employed yield LDR system masses less than heat pipe radiator system masses, and significant improvement is expected using design approaches that incorporate fluid handling components more efficiently. Technical problems (e.g., spacecraft contamination and electrostatic deflection of droplets) unique to this method of heat rejection are discussed and solutions are suggested.

  18. The Liquid Droplet Radiator - an Ultralightweight Heat Rejection System for Efficient Energy Conversion in Space

    NASA Technical Reports Server (NTRS)

    Mattick, A. T.; Hertzberg, A.

    1984-01-01

    A heat rejection system for space is described which uses a recirculating free stream of liquid droplets in place of a solid surface to radiate waste heat. By using sufficiently small droplets ( 100 micron diameter) of low vapor pressure liquids the radiating droplet sheet can be made many times lighter than the lightest solid surface radiators (heat pipes). The liquid droplet radiator (LDR) is less vulnerable to damage by micrometeoroids than solid surface radiators, and may be transported into space far more efficiently. Analyses are presented of LDR applications in thermal and photovoltaic energy conversion which indicate that fluid handling components (droplet generator, droplet collector, heat exchanger, and pump) may comprise most of the radiator system mass. Even the unoptimized models employed yield LDR system masses less than heat pipe radiator system masses, and significant improvement is expected using design approaches that incorporate fluid handling components more efficiently. Technical problems (e.g., spacecraft contamination and electrostatic deflection of droplets) unique to this method of heat rejectioon are discussed and solutions are suggested.

  19. The liquid droplet radiator - An ultralightweight heat rejection system for efficient energy conversion in space

    NASA Technical Reports Server (NTRS)

    Mattick, A. T.; Hertzberg, A.

    1981-01-01

    A heat rejection system for space is described which uses a recirculating free stream of liquid droplets in place of a solid surface to radiate waste heat. By using sufficiently small droplets (less than about 100 micron diameter) of low vapor pressure liquids (tin, tin-lead-bismuth eutectics, vacuum oils) the radiating droplet sheet can be made many times lighter than the lightest solid surface radiators (heat pipes). The liquid droplet radiator (LDR) is less vulnerable to damage by micrometeoroids than solid surface radiators, and may be transported into space far more efficiently. Analyses are presented of LDR applications in thermal and photovoltaic energy conversion which indicate that fluid handling components (droplet generator, droplet collector, heat exchanger, and pump) may comprise most of the radiator system mass. Even the unoptimized models employed yield LDR system masses less than heat pipe radiator system masses, and significant improvement is expected using design approaches that incorporate fluid handling components more efficiently. Technical problems (e.g., spacecraft contamination and electrostatic deflection of droplets) unique to this method of heat rejection are discussed and solutions are suggested.

  20. The Liquid Droplet Radiator - an Ultralightweight Heat Rejection System for Efficient Energy Conversion in Space

    NASA Technical Reports Server (NTRS)

    Mattick, A. T.; Hertzberg, A.

    1984-01-01

    A heat rejection system for space is described which uses a recirculating free stream of liquid droplets in place of a solid surface to radiate waste heat. By using sufficiently small droplets ( 100 micron diameter) of low vapor pressure liquids the radiating droplet sheet can be made many times lighter than the lightest solid surface radiators (heat pipes). The liquid droplet radiator (LDR) is less vulnerable to damage by micrometeoroids than solid surface radiators, and may be transported into space far more efficiently. Analyses are presented of LDR applications in thermal and photovoltaic energy conversion which indicate that fluid handling components (droplet generator, droplet collector, heat exchanger, and pump) may comprise most of the radiator system mass. Even the unoptimized models employed yield LDR system masses less than heat pipe radiator system masses, and significant improvement is expected using design approaches that incorporate fluid handling components more efficiently. Technical problems (e.g., spacecraft contamination and electrostatic deflection of droplets) unique to this method of heat rejectioon are discussed and solutions are suggested.

  1. Superheated fuel injection for combustion of liquid-solid slurries

    DOEpatents

    Robben, Franklin A.

    1985-01-01

    A method and device for obtaining, upon injection, flash evaporation of a liquid in a slurry fuel to aid in ignition and combustion. The device is particularly beneficial for use of coal-water slurry fuels in internal combustion engines such as diesel engines and gas turbines, and in external combustion devices such as boilers and furnaces. The slurry fuel is heated under pressure to near critical temperature in an injector accumulator, where the pressure is sufficiently high to prevent boiling. After injection into a combustion chamber, the water temperature will be well above boiling point at a reduced pressure in the combustion chamber, and flash boiling will preferentially take place at solid-liquid surfaces, resulting in the shattering of water droplets and the subsequent separation of the water from coal particles. This prevents the agglomeration of the coal particles during the subsequent ignition and combustion process, and reduces the energy required to evaporate the water and to heat the coal particles to ignition temperature. The overall effect will be to accelerate the ignition and combustion rates, and to reduce the size of the ash particles formed from the coal.

  2. Superheated fuel injection for combustion of liquid-solid slurries

    DOEpatents

    Robben, F.A.

    1984-10-19

    A method and device are claimed for obtaining, upon injection, flash evaporation of a liquid in a slurry fuel to aid in ignition and combustion. The device is particularly beneficial for use of coal-water slurry fuels in internal combustion engines such as diesel engines and gas turbines, and in external combustion devices such as boilers and furnaces. The slurry fuel is heated under pressure to near critical temperature in an injector accumulator, where the pressure is sufficiently high to prevent boiling. After injection into a combustion chamber, the water temperature will be well above boiling point at a reduced pressure in the combustion chamber, and flash boiling will preferentially take place at solid-liquid surfaces, resulting in the shattering of water droplets and the subsequent separation of the water from coal particles. This prevents the agglomeration of the coal particles during the subsequent ignition and combustion process, and reduces the energy required to evaporate the water and to heat the coal particles to ignition temperature. The overall effect will be to accelerate the ignition and combustion rates, and to reduce the size of the ash particles formed from the coal. 2 figs., 2 tabs.

  3. Immobilization of Polymer-Decorated Liquid Crystal Droplets on Chemically Tailored Surfaces

    PubMed Central

    Kinsinger, Michael I.; Buck, Maren E.; Abbott, Nicholas L.; Lynn, David M.

    2010-01-01

    We demonstrate that the assembly of an amphiphilic polyamine on the interfaces of micrometer-sized droplets of a thermotropic liquid crystal (LC) dispersed in aqueous solutions can be used to facilitate the immobilization of LC droplets on chemically functionalized surfaces. Polymer 1 was designed to contain both hydrophobic (alkyl-functionalized) and hydrophilic (primary and tertiary amine-functionalized) side chain functionality. The assembly of this polymer at the interfaces of aqueous dispersions of LC droplets was achieved by spontaneous adsorption of polymer from aqueous solution. Polymer adsorption triggered transitions in the orientational ordering of the LCs, as observed by polarized light and bright-field microscopy. We demonstrate that the presence of polymer 1 on the interfaces of these droplets can be exploited to immobilize LC droplets on planar solid surfaces through covalent bond formation (e.g., for surfaces coated with polymer multilayers containing reactive azlactone functionality) or through electrostatic interactions (e.g., for surfaces coated with multilayers containing hydrolyzed azlactone functionality). Characterization of immobilized LC droplets by polarized, fluorescence, and laser scanning confocal microscopy revealed the general spherical shape of the polymer-coated LC droplets to be maintained after immobilization, and that immobilization led to additional ordering transitions within the droplets that was dependent on the nature of the surfaces with which they were in contact. Polymer 1-functionalized LC droplets were not immobilized on polymer multilayers treated with poly(ethylene imine) (PEI). We demonstrate that the ability to design surfaces that promote or prevent the immobilization of polymer-functionalized LC droplets can exploited to pattern the immobilization of LC droplets on surfaces. The results of this investigation provide the basis of an approach that could be used to tailor the properties of dispersed LC emulsions and

  4. Injector for liquid fueled rocket engine

    NASA Technical Reports Server (NTRS)

    Cornelius, Charles S. (Inventor); Myers, W. Neill (Inventor); Shadoan, Michael David (Inventor); Sparks, David L. (Inventor)

    2000-01-01

    An injector for liquid fueled rocket engines wherein a generally flat core having a frustoconical dome attached to one side of the core to serve as a manifold for a first liquid, with the core having a generally circular configuration having an axis. The other side of the core has a plurality of concentric annular first slots and a plurality of annular concentric second slots alternating with the first slots, the second slots having a greater depth than said first slots. A bore extends through the core for inletting a second liquid into said core, the bore intersecting the second slots to feed the second liquid into the second slots. The core also has a plurality of first passageways leading from the manifold to the first annular slots for feeding the first liquid into said first slots. A faceplate brazed to said other side of the core is provided with apertures extending from the first and second slots through said face plate, these apertures being positioned to direct fuel and liquid oxygen into contact with each other in the combustion chamber. The first liquid may be liquid oxygen and the second liquid may be kerosene or liquid hydrogen.

  5. 49 CFR 393.67 - Liquid fuel tanks.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 49 Transportation 5 2014-10-01 2014-10-01 false Liquid fuel tanks. 393.67 Section 393.67... NECESSARY FOR SAFE OPERATION Fuel Systems § 393.67 Liquid fuel tanks. (a) Application of the rules in this... with commercial motor vehicles. (1) A liquid fuel tank manufactured on or after January 1, 1973, and a...

  6. On the Shape of Liquid Metal Droplets in Electromagnetic Levitation Experiments

    NASA Technical Reports Server (NTRS)

    Schwartz, E.; Sauerland, S.; Szekely, J.; Egry, I.

    1993-01-01

    We present calculations and measurements on the shape of liquid metal droplets in electromagnetic levitation experiments. A normal stress balance model was developed to predict the shapes of liquid metal droplets that will be obtained in a microgravity experiment to measure the viscosity and surface tension of undercooled metals. This model was tested by calculating the droplet shapes in containerless experiments conducted to determine the surface tension of liquid metals. Inconsistencies associated with the results of a previous paper are elucidated. The computational results of the mathematical model are compared with the results of ground-based experiments for two different metals. The importance of the ratio of electromagnetic skin depth-to-droplet radius to the accuracy of the mathematical model is discussed. A planned alternate approach to modeling the shape by consideration of the entire droplet rather than only the surface is presented. As an example of an application. the influence of the shape on the splitting of the surface oscillation modes of levitated liquid metal droplets is discussed.

  7. Combustion performance of bipropellant liquid rocket engine combustors with fuel-impingement cooling

    NASA Astrophysics Data System (ADS)

    Jiang, Tsung Leo; Chiang, Wei-Tang; Jang, Shyh-Dihng

    1995-05-01

    In order to obtain an accurate combustion analyses which are important in the thruster design of modern advanced liquid rocket engine, flow analysis should be conducted from the injector phase down to the propulsive nozzle throat. Thus, in the present study, flow analysis for the axisymmetric thrust chamber of an OMV(exp 3) installed with a pintle-type ring-shaped injector and a conical convergent nozzle is conducted. Liquid monomethyl hydrazine (MMH) and nitrogen tetroxide (NTO) storable bipropellants are used as fuel and oxidizer sources. An optimum injected fuel and oxidizer droplet-size combination is proposed. Finally, the results obtained are presented.

  8. Combustion performance of bipropellant liquid rocket engine combustors with fuel-impingement cooling

    SciTech Connect

    Jiang, T.L.; Chiang, W.; Jang, S.

    1995-05-01

    In order to obtain an accurate combustion analyses which are important in the thruster design of modern advanced liquid rocket engine, flow analysis should be conducted from the injector phase down to the propulsive nozzle throat. Thus, in the present study, flow analysis for the axisymmetric thrust chamber of an OMV(exp 3) installed with a pintle-type ring-shaped injector and a conical convergent nozzle is conducted. Liquid monomethyl hydrazine (MMH) and nitrogen tetroxide (NTO) storable bipropellants are used as fuel and oxidizer sources. An optimum injected fuel and oxidizer droplet-size combination is proposed. Finally, the results obtained are presented. 4 refs.

  9. Hydrodynamic directional control of liquid metal droplets within a microfluidic flow focusing system

    NASA Astrophysics Data System (ADS)

    Gol, Berrak; Kurdzinski, Michael E.; Tovar-Lopez, Francisco J.; Petersen, Phred; Mitchell, Arnan; Khoshmanesh, Khashayar

    2016-04-01

    Here, we investigate the directional control of Galinstan liquid metal droplets when transferring from the high-viscosity glycerol core into the parallel low-viscosity NaOH sheath streams within a flow focusing microfluidic system. In the presence of sufficient flow mismatch between the sheath streams, the droplets are driven toward the higher velocity interface and cross the interface under the influence of surface tension gradient. A minimum flow mismatch of 125 μl/min is required to enable the continuous transfer of droplets toward the desired sheath stream. The response time of droplets, the time required to change the direction of droplet transfer, is governed by the response time of the syringe pump driven microfluidic system and is found to be 3.3 and 8.8 s when increasing and decreasing the flow rate of sheath stream, respectively.

  10. Light scattering by a nematic liquid crystal droplet: Wentzel–Kramers–Brillouin approximation

    SciTech Connect

    Loiko, V. A. Konkolovich, A. V.; Miskevich, A. A.

    2016-01-15

    Light scattering by an optically anisotropic liquid crystal (LC) droplet of a nematic in an isotropic polymer matrix is considered in the Wentzel–Kramers–Brillouin (WKB) approximation. General relations are obtained for elements of the amplitude matrix of light scattering by a droplet of arbitrary shape and for the structure of the director field. Analytic expressions for the amplitude matrices are derived for spherical LC droplets with a uniformly oriented structure of local optical axes for strictly forward and strictly backward scattering. The efficiency factors of extinction and backward scattering for a spherical nonabsorbing LC droplet depending on the LC optical anisotropy, refractive index of the polymer, illumination conditions, and orientation of the optical axis of the droplet are analyzed. Verification of the obtained solutions has been performed.

  11. Fragmentation dynamics of liquid-metal droplets under ultra-short laser pulses

    NASA Astrophysics Data System (ADS)

    Basko, M. M.; Krivokorytov, M. S.; Vinokhodov, A. Yu; Sidelnikov, Yu V.; Krivtsun, V. M.; Medvedev, V. V.; Kim, D. A.; Kompanets, V. O.; Lash, A. A.; Koshelev, K. N.

    2017-03-01

    We present the measurements and theoretical analysis of the deformation and fragmentation of spherical liquid-metal drops by picosecond and subpicosecond laser pulses. In the experiments, 60 μm droplets of Sn-In alloy were irradiated by Ti:Sa laser pulses with a peak energy fluence of  ˜100 J cm-2. The observed evolution of the droplet shape dramatically differs from that previously reported for nanosecond pulses. Invoking 2D hydrodynamic simulations, we explain how, due to the specifics of matter dynamics in the liquid-vapor phase coexistence region, a liquid droplet is transformed into a characteristic acorn-like expanding shell with two inner cavities. High sensitivity of the measured shell parameters to the details of the equation of state and metastable dynamics suggests that such experiments offer new possibilities in exploration of thermophysical properties of metals in the region of liquid-vapor phase transition.

  12. POWER GENERATION FROM LIQUID METAL NUCLEAR FUEL

    DOEpatents

    Dwyer, O.E.

    1958-12-23

    A nuclear reactor system is described wherein the reactor is the type using a liquid metal fuel, such as a dispersion of fissile material in bismuth. The reactor is designed ln the form of a closed loop having a core sectlon and heat exchanger sections. The liquid fuel is clrculated through the loop undergoing flssion in the core section to produce heat energy and transferrlng this heat energy to secondary fluids in the heat exchanger sections. The fission in the core may be produced by a separate neutron source or by a selfsustained chain reaction of the liquid fuel present in the core section. Additional auxiliary heat exchangers are used in the system to convert water into steam which drives a turbine.

  13. Estimation of liquid fuel yields from biomass.

    PubMed

    Singh, Navneet R; Delgass, W Nicholas; Ribeiro, Fabio H; Agrawal, Rakesh

    2010-07-01

    We have estimated sun-to-fuel yields for the cases when dedicated fuel crops are grown and harvested to produce liquid fuel. The stand-alone biomass to liquid fuel processes, that use biomass as the main source of energy, are estimated to produce one-and-one-half to three times less sun-to-fuel yield than the augmented processes. In an augmented process, solar energy from a fraction of the available land area is used to produce other forms of energy such as H(2), heat etc., which are then used to increase biomass carbon recovery in the conversion process. However, even at the highest biomass growth rate of 6.25 kg/m(2).y considered in this study, the much improved augmented processes are estimated to have sun-to-fuel yield of about 2%. We also propose a novel stand-alone H(2)Bioil-B process, where a portion of the biomass is gasified to provide H(2) for the fast-hydropyrolysis/hydrodeoxygenation of the remaining biomass. This process is estimated to be able to produce 125-146 ethanol gallon equivalents (ege)/ton of biomass of high energy density oil but needs experimental development. The augmented version of fast-hydropyrolysis/hydrodeoxygenation, where H(2) is generated from a nonbiomass energy source, is estimated to provide liquid fuel yields as high as 215 ege/ton of biomass. These estimated yields provide reasonable targets for the development of efficient biomass conversion processes to provide liquid fuel for a sustainable transport sector.

  14. High effectiveness liquid droplet/gas heat exchanger for space power applications

    NASA Astrophysics Data System (ADS)

    Bruckner, A. P.; Mattick, A. T.

    1983-09-01

    A high-effectiveness liquid droplet/gas heat exchanger (LDHX) concept for thermal management in space is described. Heat is transferred by direct contact between fine droplets (approx. 100 to 300 micron diameter) of a suitable low vapor pressure liquid and an inert working gas. Complete separation of the droplet and gas media in the zero-g environment is accomplished by configuring the LDHX as a vortex chamber. The large heat transfer area presented by the small droplets permits heat exchanger effectiveness of 0.9 to 0.95 in a compact, lightweight geometry which avoids many of the limitations of conventional plate and fin or tube and shell heat exchangers, such as their tendency toward single point failure. The application of the LDHX in a high temperature Bryaton cycle is discussed to illustrate the performance and operational characteristics of this heat exchanger concept.

  15. High effectiveness liquid droplet/gas heat exchanger for space power applications

    NASA Technical Reports Server (NTRS)

    Bruckner, A. P.; Mattick, A. T.

    1983-01-01

    A high-effectiveness liquid droplet/gas heat exchanger (LDHX) concept for thermal management in space is described. Heat is transferred by direct contact between fine droplets (approx. 100 to 300 micron diameter) of a suitable low vapor pressure liquid and an inert working gas. Complete separation of the droplet and gas media in the zero-g environment is accomplished by configuring the LDHX as a vortex chamber. The large heat transfer area presented by the small droplets permits heat exchanger effectiveness of 0.9 to 0.95 in a compact, lightweight geometry which avoids many of the limitations of conventional plate and fin or tube and shell heat exchangers, such as their tendency toward single point failure. The application of the LDHX in a high temperature Bryaton cycle is discussed to illustrate the performance and operational characteristics of this heat exchanger concept.

  16. High effectiveness liquid droplet/gas heat exchanger for space power applications

    NASA Technical Reports Server (NTRS)

    Bruckner, A. P.; Mattick, A. T.

    1983-01-01

    A high-effectiveness liquid droplet/gas heat exchanger (LDHX) concept for thermal management in space is described. Heat is transferred by direct contact between fine droplets (approximately 100-300 microns in diameter) of a suitable low vapor pressure liquid and an inert working gas. Complete separation of the droplet and gas media in the zero-g environment is accomplished by configuring the LDHX as a vortex chamber.The large heat transfer area presented by the small droplets permits heat exchanger effectiveness of 0.9-0.95 in a compact, lightweight geometry which avoids many of the limitations of conventional plate and fin or tube and shell heat exchangers, such as their tendency toward single point failure. The application of the LDHX in a high temperature Brayton cycle is discussed to illustrate the performance and operational characteristics of this new heat exchanger concept.

  17. Numerical Investigation on Sensitivity of Liquid Jet Breakup to Physical Fuel Properties with Experimental Comparison

    NASA Astrophysics Data System (ADS)

    Kim, Dokyun; Bravo, Luis; Matusik, Katarzyna; Duke, Daniel; Kastengren, Alan; Swantek, Andy; Powell, Christopher; Ham, Frank

    2016-11-01

    One of the major concerns in modern direct injection engines is the sensitivity of engine performance to fuel characteristics. Recent works have shown that even slight differences in fuel properties can cause significant changes in efficiency and emission of an engine. Since the combustion process is very sensitive to the fuel/air mixture formation resulting from disintegration of liquid jet, the precise assessment of fuel sensitivity on liquid jet atomization process is required first to study the impact of different fuels on the combustion. In the present study, the breaking process of a liquid jet from a diesel injector injecting into a quiescent gas chamber is investigated numerically and experimentally for different liquid fuels (n-dodecane, iso-octane, CAT A2 and C3). The unsplit geometric Volume-of-Fluid method is employed to capture the phase interface in Large-eddy simulations and results are compared against the radiography measurement from Argonne National Lab including jet penetration, liquid mass distribution and volume fraction. The breakup characteristics will be shown for different fuels as well as droplet PDF statistics to demonstrate the influences of the physical properties on the primary atomization of liquid jet. Supported by HPCMP FRONTIER award, US DOD, Office of the Army.

  18. Nuclear Energy and Synthetic Liquid Transportation Fuels

    NASA Astrophysics Data System (ADS)

    McDonald, Richard

    2012-10-01

    This talk will propose a plan to combine nuclear reactors with the Fischer-Tropsch (F-T) process to produce synthetic carbon-neutral liquid transportation fuels from sea water. These fuels can be formed from the hydrogen and carbon dioxide in sea water and will burn to water and carbon dioxide in a cycle powered by nuclear reactors. The F-T process was developed nearly 100 years ago as a method of synthesizing liquid fuels from coal. This process presently provides commercial liquid fuels in South Africa, Malaysia, and Qatar, mainly using natural gas as a feedstock. Nuclear energy can be used to separate water into hydrogen and oxygen as well as to extract carbon dioxide from sea water using ion exchange technology. The carbon dioxide and hydrogen react to form synthesis gas, the mixture needed at the beginning of the F-T process. Following further refining, the products, typically diesel and Jet-A, can use existing infrastructure and can power conventional engines with little or no modification. We can then use these carbon-neutral liquid fuels conveniently long into the future with few adverse environmental impacts.

  19. Ignition of a floating droplet of organic coal-water fuel

    NASA Astrophysics Data System (ADS)

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

    2016-06-01

    The results of experimental investigations are presented for the ignition of droplets (particles) of organic coal-water fuels (OCWFs) floating in a flow of an oxidizer using a special combustion chamber from high-temperature quartz glass. The temperature and the velocity of motion of the oxidizer vary in the ranges of 500-900 K and 0.5-3 m/s. The initial sizes (radii) of fuel droplets amounted to 0.3-1.5 mm. As the basic OCWF components, particles (of 80-100 µm in size) of brown coal "B2," water, mazut, and waste castor and compressor oils are used. With use of the system of high-velocity video registration, the conditions providing for floating of OCWF particles without initiation of burning and with the subsequent steady ignition are established. Four modes of OCWF-droplet ignition with different trajectories of their motion in the combustion chamber are singled out. The times of the OCWF-ignition delay in dependence on the size of fuel particles and oxidizer temperatures are determined. The deviations of the OCWF-ignition-delay times obtained under conditions of suspension of a droplet on the thermocouple junction and while floating in the oxidizer flow are established.

  20. Continuously rotating chiral liquid crystal droplets in a linearly polarized laser trap.

    PubMed

    Yang, Y; Brimicombe, P D; Roberts, N W; Dickinson, M R; Osipov, M; Gleeson, H F

    2008-05-12

    The transfer of optical angular momentum to birefringent particles via circularly polarized light is common. We report here on the unexpected, continuous rotation of chiral nematic liquid crystal droplets in a linearly polarized optical trap. The rotation is non-uniform, occurs over a timescale of seconds, and is observed only for very specific droplet sizes. Synchronized vertical motion of the droplet occurs during the rotation. The motion is the result of photo-induced molecular reorganization, providing a micron sized opto-mechanical transducer that twists and translates.

  1. Liquid droplet radiator development status. [waste heat rejection devices for future space vehicles

    NASA Technical Reports Server (NTRS)

    White, K. Alan, III

    1987-01-01

    Development of the Liquid Droplet Radiator (LDR) is described. Significant published results of previous investigators are presented, and work currently in progress is discussed. Several proposed LDR configurations are described, and the rectangular and triangular configurations currently of most interest are examined. Development of the droplet generator, collector, and auxiliary components are discussed. Radiative performance of a droplet sheet is considered, and experimental results are seen to be in very good agreement with analytical predictions. The collision of droplets in the droplet sheet, the charging of droplets by the space plasma, and the effect of atmospheric drag on the droplet sheet are shown to be of little consequence, or can be minimized by proper design. The LDR is seen to be less susceptible than conventional technology to the effects of micrometeoroids or hostile threats. The identification of working fluids which are stable in the orbital environments of interest is also made. Methods for reducing spacecraft contamination from an LDR to an acceptable level are discussed. Preliminary results of microgravity testing of the droplet generator are presented. Possible future NASA and Air Force missions enhanced or enabled by a LDR are also discussed. System studies indicate that the LDR is potentially less massive than heat pipe radiators. Planned microgravity testing aboard the Shuttle or space station is seen to be a logical next step in LDR development.

  2. Liquid crystal droplets as a hosting and sensing platform for developing immunoassays.

    PubMed

    Aliño, Vera Joanne; Pang, Jasmine; Yang, Kun-Lin

    2011-10-04

    In this paper, we report an immunoassay in which probe proteins are immobilized on the surface of liquid crystal (LC) droplets rather than on solid surfaces. The advantage of this immunoassay is that the binding of antibodies to the probe proteins can be transduced by the LC droplets directly without the need for additional steps. For example, when we incubate the LC droplets decorated with immunoglobulin G (IgG) in a solution containing anti-IgG (AIgG), these droplets change their orientations from radial to bipolar configuration. In contrast, when we incubate the IgG-LC droplets in a solution containing anti-human serum albumin (AHSA), no changes are observed. The change of orientational configuration indicates the formation of the antigen-antibody immunocomplex on the surface of the LC droplets. Using LC droplet immunoassays, we successfully detect antibody concentrations as low as 0.01 μg/mL for AIgG and 0.02 μg/mL for AHSA. Because the immunoassay using LC droplets is label-free and gives a unique optical response, it has the potential to be further developed as a portable and low-cost immunoassay. © 2011 American Chemical Society

  3. Liquid droplet radiator development status. [waste heat rejection devices for future space vehicles

    NASA Technical Reports Server (NTRS)

    White, K. Alan, III

    1987-01-01

    Development of the Liquid Droplet Radiator (LDR) is described. Significant published results of previous investigators are presented, and work currently in progress is discussed. Several proposed LDR configurations are described, and the rectangular and triangular configurations currently of most interest are examined. Development of the droplet generator, collector, and auxiliary components are discussed. Radiative performance of a droplet sheet is considered, and experimental results are seen to be in very good agreement with analytical predictions. The collision of droplets in the droplet sheet, the charging of droplets by the space plasma, and the effect of atmospheric drag on the droplet sheet are shown to be of little consequence, or can be minimized by proper design. The LDR is seen to be less susceptible than conventional technology to the effects of micrometeoroids or hostile threats. The identification of working fluids which are stable in the orbital environments of interest is also made. Methods for reducing spacecraft contamination from an LDR to an acceptable level are discussed. Preliminary results of microgravity testing of the droplet generator are presented. Possible future NASA and Air Force missions enhanced or enabled by a LDR are also discussed. System studies indicate that the LDR is potentially less massive than heat pipe radiators. Planned microgravity testing aboard the Shuttle or space station is seen to be a logical next step in LDR development.

  4. Oscillation of satellite droplets in an Oldroyd-B viscoelastic liquid jet

    NASA Astrophysics Data System (ADS)

    Li, Fang; Yin, Xie-Yuan; Yin, Xie-Zhen

    2017-01-01

    A one-dimensional numerical simulation is carried out to study the oscillation characteristics of satellite droplets in the beads-on-a-string structure of an Oldroyd-B viscoelastic liquid jet. The oscillation of satellite droplets is compared with the linear oscillation of a single viscoelastic droplet. It is found that, contrary to the predictions of linear theory, the period of oscillation of satellite droplets decreases with time, despite the increase in droplet volume. The mechanism may lie in the existence of the filament, which exerts an extra resistance on droplets. On the other hand, the oscillation of droplets does not influence very much the thinning of the filament. The influence of the axial wave number, viscosity, and elasticity on the oscillation of satellite droplets is examined. Increasing the wave number may result in the decrease in the period and the increase in the decay rate of oscillation, while increasing viscosity may lead to the increase in both the period and the decay rate of oscillation. Elasticity is shown to suppress the oscillation at large wave numbers, but its influence is limited at small wave numbers.

  5. Marangoni Effect on the Shape of Freely Receding Evaporating Sessile Droplets of Perfectly Wetting Liquids

    NASA Astrophysics Data System (ADS)

    Tsoumpas, Yannis; Dehaeck, Sam; Rednikov, Alexey; Colinet, Pierre

    2014-11-01

    Freely receding evaporating sessile droplets of perfectly wetting liquids (HFE-7100, 7200 and 7500), with small finite contact angles induced by evaporation, are studied with a Mach-Zehnder interferometer. Surprisingly, the experimentally obtained profiles turn out to deviate from the classical macroscopic static shape of a sessile droplet (as determined by gravity and capillarity), often used when modeling evaporating droplets. These deviations can be seen in two ways. Namely, either the droplet appears to be inflated as compared to the classical static shape assuming the same contact angle and contact radius, or the apparent contact angle appears lower than the classical static one assuming the same volume and contact radius. In reality, the experimental profiles exhibit a local decrease of the slope near the contact line, which we attribute to the Marangoni effect in an evaporating sessile droplet. In this case, the radially inward (along the liquid-air interface) direction of the flow delivers more liquid to the center of the droplet making it appear inflated. When the Marangoni effect is weak, as in the case of the poorly volatile HFE-7500, no significant influence is noticed on the drop shape. The experimental results are compared with the predictions of a lubrication-type theoretical model that incorporates the evaporation-induced Marangoni flow. Financial support of FP7 Marie Curie MULTIFLOW Network (PITN-GA-2008-214919), ESA/BELSPO-PRODEX, BELSPO- μMAST (IAP 7/38) & FRS-FNRS is gratefully acknowledged.

  6. Light-induced rotation of dye-doped liquid crystal droplets.

    PubMed

    Manzo, C; Paparo, D; Marrucci, L; Jánossy, I

    2006-05-01

    We investigate both theoretically and experimentally the rotational dynamics of micrometric droplets of dye-doped and pure liquid crystal induced by circularly and elliptically polarized laser light. The droplets are dispersed in water and trapped in the focus of the laser beam. Since the optical torque acting on the molecular director is known to be strongly enhanced in light-absorbing dye-doped materials, the question arises whether a similar enhancement takes place also for the overall optical torque acting on the whole droplets. We searched for such enhancement by measuring and comparing the rotation speed of dye-doped droplets induced by a laser beam having a wavelength either inside or outside the dye absorption band, and also comparing it with the rotation of pure liquid crystal droplets. No enhancement was found, confirming that photoinduced dye effects are only associated with an internal exchange of angular momentum between orientational and translational degrees of freedom of matter. Our result provides also direct experimental proof of the existence of a photoinduced stress tensor in the illuminated dye-doped liquid crystal. Finally, peculiar photoinduced dynamical effects are predicted to occur in droplets in which the molecular director is not rigidly locked to the flow, but so far they could not be observed.

  7. Emissions Prediction and Measurement for Liquid-Fueled TVC Combustor with and without Water Injection

    NASA Technical Reports Server (NTRS)

    Brankovic, A.; Ryder, R. C., Jr.; Hendricks, R. C.; Liu, N.-S.; Shouse, D. T.; Roquemore, W. M.

    2005-01-01

    An investigation is performed to evaluate the performance of a computational fluid dynamics (CFD) tool for the prediction of the reacting flow in a liquid-fueled combustor that uses water injection for control of pollutant emissions. The experiment consists of a multisector, liquid-fueled combustor rig operated at different inlet pressures and temperatures, and over a range of fuel/air and water/fuel ratios. Fuel can be injected directly into the main combustion airstream and into the cavities. Test rig performance is characterized by combustor exit quantities such as temperature and emissions measurements using rakes and overall pressure drop from upstream plenum to combustor exit. Visualization of the flame is performed using gray scale and color still photographs and high-frame-rate videos. CFD simulations are performed utilizing a methodology that includes computer-aided design (CAD) solid modeling of the geometry, parallel processing over networked computers, and graphical and quantitative post-processing. Physical models include liquid fuel droplet dynamics and evaporation, with combustion modeled using a hybrid finite-rate chemistry model developed for Jet-A fuel. CFD and experimental results are compared for cases with cavity-only fueling, while numerical studies of cavity and main fueling was also performed. Predicted and measured trends in combustor exit temperature, CO and NOx are in general agreement at the different water/fuel loading rates, although quantitative differences exist between the predictions and measurements.

  8. Liquid fuels production from biomass. Final report

    SciTech Connect

    Levy, P. F.; Sanderson, J. E.; Ashare, E.; Wise, D. L.; Molyneaux, M. S.

    1980-06-30

    The current program to convert biomass into liquid hydrocarbon fuels is an extension of a previous program to ferment marine algae to acetic acid. In that study it was found that marine algae could be converted to higher aliphatic organic acids and that these acids could be readily removed from the fermentation broth by membrane or liquid-liquid extraction. It was then proposed to convert these higher organic acids via Kolbe electrolysis to aliphatic hydrocarbons, which may be used as a diesel fuel. The specific goals for the current porgram are: (1) establish conditions under which substrates other than marine algae may be converted in good yield to organic acids, here the primary task is methane suppression; (2) modify the current 300-liter fixed packed bed batch fermenter to operate in a continuous mode; (3) change from membrane extraction of organic acids to liquid-liquid extraction; (4) optimize the energy balance of the electrolytic oxidation process, the primary task is to reduce the working potential required for the electrolysis while maintaining an adequate current density; (5) scale the entire process up to match the output of the 300 liter fermenter; and (6) design pilot plant and commercial size plant (1000 tons/day) processes for converting biomass to liquid hydrocarbon fuels and perform an economic analysis for the 1000 ton/day design.

  9. Study on Droplet Entrainment of High-Viscosity Falling Liquid Film

    NASA Astrophysics Data System (ADS)

    Inumaru, Jun; Ohtaka, Maromu; Watanabe, Hiroaki

    An experimental study of counter-current annular two-phase flow of high-viscosity liquid and air in a large diameter pipe was carried out to investigate the inception criterion for entrainment of molten slag droplet in an entrained flow coal gasifier. Liquid film thickness was measured using a high-speed camera for 4 types of liquid with various viscosities and surface tensions. It was clearly shown that the measured average wave amplitude had a good correlation with the gas Reynolds number, and that the predicted critical gas velocity for droplet inception using new formula of wave amplitude had a good agreement with the experimental results under the condition of very low fluid Reynolds number( Ref ≤10). The critical Weber number Wec =1.73 was obtained as inception criterion of droplet entrainment.

  10. On droplet combustion of biodiesel fuel mixed with diesel/alkanes in microgravity condition

    SciTech Connect

    Pan, Kuo-Long; Li, Je-Wei; Chen, Chien-Pei; Wang, Ching-Hua

    2009-10-15

    The burning characteristics of a biodiesel droplet mixed with diesel or alkanes such as dodecane and hexadecane were experimentally studied in a reduced-gravity environment so as to create a spherically symmetrical flame without the influence of natural convection due to buoyancy. Small droplets on the order of 500 {mu}m in diameter were initially injected via a piezoelectric technique onto the cross point intersected by two thin carbon fibers; these were prepared inside a combustion chamber that was housed in a drag shield, which was freely dropped onto a foam cushion. It was found that, for single component droplets, the tendency to form a rigid soot shell was relatively small for biodiesel fuel as compared to that exhibited by the other tested fuels. The soot created drifted away readily, showing a puffing phenomenon; this could be related to the distinct molecular structure of biodiesel leading to unique soot layers that were more vulnerable to oxidative reactivity as compared to the soot generated by diesel or alkanes. The addition of biodiesel to these more traditional fuels also presented better performance with respect to annihilating the soot shell, particularly for diesel. The burning rate generally follows that of multi-component fuels, by some means in terms of a lever rule, whereas the mixture of biodiesel and dodecane exhibits a somewhat nonlinear relation with the added fraction of dodecane. This might be related to the formation of a soot shell. (author)

  11. Initiation of organic coal-water fuel droplet burning in a vortex combustion chamber

    NASA Astrophysics Data System (ADS)

    Nakoryakov, V. E.; Glushkov, D. O.; Strizhak, P. A.; Syrodoy, S. V.

    2017-04-01

    Using a test bench the main part of which is a vortex combustion chamber, characteristics describing the initiation of burning of solitary droplets of a typical organic coal-water fuel (OCWF) are established. The oxidizer temperature varied in the range of 600-850 K. The linear motion velocity of the oxidizer in the vortex chamber was about 3 m/s. The configuration of the chamber and parameters of the air flow provided a stable regime of floating for droplets with a size (radius) of about 0.5 mm. The analysis results show that the intensity of initiation of OCWF combustion under conditions of processes occurring in boiler furnaces is significantly (by a factor of 2-4) higher than for droplets that are immovably fixed or freely float in the heated air flow.

  12. Skylab near-infrared observations of clouds indicating supercooled liquid water droplets

    NASA Technical Reports Server (NTRS)

    Curran, R. J.; Wu, M.-L. C.

    1982-01-01

    Orographically-induced lee-wave clouds were observed over New Mexico by a multichannel scanning radiometer on Skylab during December 1973. Channels centered at 0.83, 1.61 and 2.125 microns were used to determine the cloud optical thickness, thermodynamic phase and effective particle size. An additional channel centered at 11.4 microns was used to determine cloud-top temperature, which was corroborated through comparison with the stereographically determined cloud top altitudes and conventional temperature soundings. Analysis of the measured near-infrared reflection functions at 1.61 and 2.125 microns are most easily interpreted as indicating the presence of liquid-phase water droplets. This interpretation is not conclusive even after considerable effort to understand possible sources for misinterpretation. However, if accepted the resulting phase determination is considered anomalous due to the inferred cloud-top temperatures being in the -32 to -47 C range. Theory for the homogeneous nucleation of pure supercooled liquid water droplets predicts very short lifetimes for the liquid phase at these cold temperatures. A possible explanation for the observations is that the wave-clouds are composed of solution droplets. Impurities in the cloud droplets could decrease the homogeneous freezing rate for these droplets, permitting them to exist for a longer time in the liquid phase, at the cold temperatures found.

  13. Skylab near-infrared observations of clouds indicating supercooled liquid water droplets

    NASA Technical Reports Server (NTRS)

    Curran, R. J.; Wu, M.-L. C.

    1982-01-01

    Orographically-induced lee-wave clouds were observed over New Mexico by a multichannel scanning radiometer on Skylab during December 1973. Channels centered at 0.83, 1.61 and 2.125 microns were used to determine the cloud optical thickness, thermodynamic phase and effective particle size. An additional channel centered at 11.4 microns was used to determine cloud-top temperature, which was corroborated through comparison with the stereographically determined cloud top altitudes and conventional temperature soundings. Analysis of the measured near-infrared reflection functions at 1.61 and 2.125 microns are most easily interpreted as indicating the presence of liquid-phase water droplets. This interpretation is not conclusive even after considerable effort to understand possible sources for misinterpretation. However, if accepted the resulting phase determination is considered anomalous due to the inferred cloud-top temperatures being in the -32 to -47 C range. Theory for the homogeneous nucleation of pure supercooled liquid water droplets predicts very short lifetimes for the liquid phase at these cold temperatures. A possible explanation for the observations is that the wave-clouds are composed of solution droplets. Impurities in the cloud droplets could decrease the homogeneous freezing rate for these droplets, permitting them to exist for a longer time in the liquid phase, at the cold temperatures found.

  14. Liquid Metal Fuel Combustion Mechanics

    DTIC Science & Technology

    1990-12-01

    Mechanics. No such analysis seem to have been done todate . The other way is to calculate the fluid Finally the location of the liquid particles within the...3601, July about 10 axial locations before peaking up . At about y=25, the 1987. 5 3. L.P.Cook and E.R.Plante: Survey of alternate Stored Chemical

  15. Spreading of Thin Droplets of Perfect and Leaky Dielectric Liquids on Inclined Surfaces.

    PubMed

    Corbett, Andrew; Kumar, Satish

    2016-07-05

    The spreading of droplets may be influenced by electric fields, a situation that is relevant to applications such as coating, printing, and microfluidics. In this work we study the effects of an electric field on the gravity-driven spreading of two-dimensional droplets down an inclined plane. We consider both perfect and leaky dielectric liquids, as well as perfectly and partially wetting systems. In addition to the effects of electric fields, we examine the use of thermocapillary forces to suppress the growth of the capillary ridge near the droplet front. Lubrication theory is applied to generate a set of coupled partial differential equations for interfacial height and charge, which are then solved numerically with a finite-difference method. Electric fields increase the height of the capillary ridge in both perfect and leaky dielectric droplets due to electrostatic pressure gradients that drive liquid into the ridge. In leaky dielectrics, large interfacial charge gradients in the contact-line region create shear stresses that also enhance ridge growth and the formation of trailing minor ridges. The coalescence of these ridges can significantly affect the long-time thinning rate of leaky dielectric droplets. In partially wetting liquids, electric fields promote the splitting of smaller droplets from the primary droplet near the receding contact line due to the interplay between electrostatic forces and disjoining pressure. Cooling from below and heating from above generates thermocapillary forces that counteract the effects of electric fields and suppress the growth of the capillary ridge. The results of this work have important implications for manipulating the spreading of droplets down inclined surfaces.

  16. Revisiting kinetic boundary conditions at the surface of fuel droplet hydrocarbons: An atomistic computational fluid dynamics simulation.

    PubMed

    Nasiri, Rasoul

    2016-05-24

    The role of boundary conditions at the interface for both Boltzmann equation and the set of Navier-Stokes equations have been suggested to be important for studying of multiphase flows such as evaporation/condensation process which doesn't always obey the equilibrium conditions. Here we present aspects of transition-state theory (TST) alongside with kinetic gas theory (KGT) relevant to the study of quasi-equilibrium interfacial phenomena and the equilibrium gas phase processes, respectively. A two-state mathematical model for long-chain hydrocarbons which have multi-structural specifications is introduced to clarify how kinetics and thermodynamics affect evaporation/condensation process at the surface of fuel droplet, liquid and gas phases and then show how experimental observations for a number of n-alkane may be reproduced using a hybrid framework TST and KGT with physically reasonable parameters controlling the interface, gas and liquid phases. The importance of internal activation dynamics at the surface of n-alkane droplets is established during the evaporation/condensation process.

  17. Revisiting kinetic boundary conditions at the surface of fuel droplet hydrocarbons: An atomistic computational fluid dynamics simulation

    PubMed Central

    Nasiri, Rasoul

    2016-01-01

    The role of boundary conditions at the interface for both Boltzmann equation and the set of Navier-Stokes equations have been suggested to be important for studying of multiphase flows such as evaporation/condensation process which doesn’t always obey the equilibrium conditions. Here we present aspects of transition-state theory (TST) alongside with kinetic gas theory (KGT) relevant to the study of quasi-equilibrium interfacial phenomena and the equilibrium gas phase processes, respectively. A two-state mathematical model for long-chain hydrocarbons which have multi-structural specifications is introduced to clarify how kinetics and thermodynamics affect evaporation/condensation process at the surface of fuel droplet, liquid and gas phases and then show how experimental observations for a number of n-alkane may be reproduced using a hybrid framework TST and KGT with physically reasonable parameters controlling the interface, gas and liquid phases. The importance of internal activation dynamics at the surface of n-alkane droplets is established during the evaporation/condensation process. PMID:27215897

  18. Revisiting kinetic boundary conditions at the surface of fuel droplet hydrocarbons: An atomistic computational fluid dynamics simulation

    NASA Astrophysics Data System (ADS)

    Nasiri, Rasoul

    2016-05-01

    The role of boundary conditions at the interface for both Boltzmann equation and the set of Navier-Stokes equations have been suggested to be important for studying of multiphase flows such as evaporation/condensation process which doesn’t always obey the equilibrium conditions. Here we present aspects of transition-state theory (TST) alongside with kinetic gas theory (KGT) relevant to the study of quasi-equilibrium interfacial phenomena and the equilibrium gas phase processes, respectively. A two-state mathematical model for long-chain hydrocarbons which have multi-structural specifications is introduced to clarify how kinetics and thermodynamics affect evaporation/condensation process at the surface of fuel droplet, liquid and gas phases and then show how experimental observations for a number of n-alkane may be reproduced using a hybrid framework TST and KGT with physically reasonable parameters controlling the interface, gas and liquid phases. The importance of internal activation dynamics at the surface of n-alkane droplets is established during the evaporation/condensation process.

  19. Liquid Fuels from Lignins: Annual Report

    SciTech Connect

    Chum, H. L.; Johnson, D. K.

    1986-01-01

    This task was initiated to assess the conversion of lignins into liquid fuels, primarily of lignins relevant to biomass-to-ethanol conversion processes. The task was composed of a literature review of this area and an experimental part to obtain pertinent data on the conversion of lignins germane to biomass-to-ethanol conversion processes.

  20. Coal and Biomass to Liquid Fuels

    EPA Science Inventory

    For Frank Princiotta’s book, Global Climate Change—The Technology Challenge Demand for liquid transportation fuels has been increasing by over 2%/yr over the last two decades and is accelerating in the emerging economies which are moving to automobile ownership. Almost all liq...

  1. Liquid Fuels Market Module - NEMS Documentation

    EIA Publications

    2017-01-01

    Defines the objectives of the Liquid Fuels Market Model (LFMM), describes its basic approach, and provides detail on how it works. This report is intended as a reference document for model analysts, users, and the public. This edition of the LFMM reflects changes made to the module over the past two years for the Annual Energy Outlook 2016.

  2. Coal and Biomass to Liquid Fuels

    EPA Science Inventory

    For Frank Princiotta’s book, Global Climate Change—The Technology Challenge Demand for liquid transportation fuels has been increasing by over 2%/yr over the last two decades and is accelerating in the emerging economies which are moving to automobile ownership. Almost all liq...

  3. Conversion of cellulosic wastes to liquid fuels

    SciTech Connect

    Kuester, J.L.

    1980-09-01

    The current status and future plans for a project to convert waste cellulosic (biomass) materials to quality liquid hydrocarbon fuels is described. The basic approach is indirect liquefaction, i.e., thermal gasification followed by catalytic liquefaction. The indirect approach results in separation of the oxygen in the biomass feedstock, i.e., oxygenated compounds do not appear in the liquid hydrocarbon fuel product. The process is capable of accepting a wide variety of feedstocks. Potential products include medium quality gas, normal propanol, diesel fuel and/or high octane gasoline. A fluidized bed pyrolysis system is used for gasification. The pyrolyzer can be fluidized with recycle pyrolysis gas, steam or recycle liquefaction system off gas or some combination thereof. Tars are removed in a wet scrubber. Unseparated pyrolysis gases are utilized as feed to a modified Fischer-Tropsch reactor. The liquid condensate from the reactor consists of a normal propanol-water phase and a paraffinic hydrocarbon phase. The reactor can be operated to optimize for either product. The following tasks were specified in the statement of work for the contract period: (1) feedstock studies; (2) gasification system optimization; (3) waste stream characterization; and (4) liquid fuels synthesis. In addition, several equipment improvements were implemented.

  4. Liquid-in-gas droplet microfluidics; experimental characterization of droplet morphology, generation frequency, and monodispersity in a flow-focusing microfluidic device

    NASA Astrophysics Data System (ADS)

    Tirandazi, Pooyan; Hidrovo, Carlos H.

    2017-07-01

    Microfluidic techniques for production of uniform droplets usually rely on the use of two immiscible liquids (e.g. water-in-oil emulsions). It has been shown recently that a continuous gas flow instead of a second liquid carrier can be used as an alternative approach in droplet microfluidics. In this work we experimentally investigate the generation of liquid water droplets within air in flow-focusing configurations. Over a wide range of flow conditions we identify six distinct flow regimes inside the microchannel: Co-flowing, Threading, Plugging, Dripping, Multi-Satellite Formation, and Jetting. Flow regimes and their transitions are plotted and characterized based on the Weber number (We) of the system. We further investigate the impact of liquid microchannel size on the flow maps. Generation frequency, morphology, and monodispersity of the droplets are characterized in more detail in the Dripping regime. Generation frequency can be related to the product of the liquid and gas flow rates. However, droplet morphology (length and width) is more dependent on the gas flow rate. We demonstrate the production of monodisperse droplets (d < 100 µm and σ/d < 5 %) up to kHz formation rates in liquid-gas microfluidic systems for the first time. The results of this work provide practical and useful guidelines for precise, oil-free delivery of ultra-small volumes of fluid which can be integrated in lab-on-a-chip systems for a variety of applications in biochemical research and material synthesis.

  5. Sample Preparation for Repeated Measurements on a Single Liquid Droplet Using Laser-Induced Breakdown Spectroscopy.

    PubMed

    Lazic, Violeta; Fantoni, Roberta; Palucci, Antonio; Ciaffi, Massimiliano

    2017-01-01

    We studied changes in laser-induced breakdown spectroscopy (LIBS) signal intensity with the thickness of a liquid layer placed on a solid substrate, where an easily evaporating methanol sample was used. For a certain optimal liquid film thickness we obtained a manifold increase of the LIBS signal from methanol. Progressive liquid film thinning leads to a reduction and a successive disappearance of laser-induced splashes; the latter condition drastically reduces the sample consumption and allows measurements to be repeated many times on a single liquid droplet. In following, we developed two methods for actively controlled deformation, i.e., thinning of a liquid droplet (volume ∼10 µl) prior to its sampling by LIBS. Control of the droplet's height was achieved on a Si-SiO2 wafer substrate by electro-wetting in the case of water solutions or by target rotation in the case of viscous liquids. The chosen substrate also has the advantages of low cost, easy manipulation, and very high purity, thus minimizing interference with analytes. Through the droplet deformation, in a single-pulse excitation at moderate laser energy (70 mJ), we clearly detected Fe and Mn in peanut oil, which represent trace elements in edible oils (∼ 1 part per billion), according to results published in the literature.

  6. Droplet crystallisation in large scale direct molecular dynamics simulations of homogeneous vapor-to-liquid nucleation

    NASA Astrophysics Data System (ADS)

    Diemand, J.; Tanaka, K. K.; Tanaka, H.; Angelil, R.

    2014-12-01

    We use large scale direct (NVE and NVT) molecular dynamics simulations to study phase transitions. Typical runs contain one billion atoms and run for up to 100 million time-steps. This corresponds to scales of micrometers and microseconds and allows us to resolve similar nucleation rates as probed in some laboratory experiments. In homogeneous vapor-to-liquid nucleation simulations using Lennard-Jones atoms (Diemand et al. JCP 2013) and various water models (ongoing work) we observe a second phase transition form liquid-to-solid in some of the lower temperature runs (see Tanaka et al. JCP 2011 for one such case). Here we will describe the crystallisation of these supercooled liquid-like nano-clusters in detail. We will present crystal structure, nucleation and growth rates for a range of temperatures, droplet sizes and interaction potentials and compare with model predictions. Since our liquid nano-droplets are condensing naturally out of the vapour phase, as in clouds and some experiments and industrial processes, we can address some specific questions relevant in these contexts: How does the droplet size, structure and especially its surface affect the freezing process? To what extend does the latent heat from the ongoing condensation onto the droplets surface delay and alter crystallisation? Can frozen nano-clusters grow by direct de-sublimation from the vapour, or is there always a liquid-like surface? And can they form directly without going through a liquid-like proto-cluster stage?

  7. Droplet charging regimes for ultrasonic atomization of a liquid electrolyte in an external electric field

    NASA Astrophysics Data System (ADS)

    Forbes, Thomas P.; Degertekin, F. Levent; Fedorov, Andrei G.

    2011-01-01

    Distinct regimes of droplet charging, determined by the dominant charge transport process, are identified for an ultrasonic droplet ejector using electrohydrodynamic computational simulations, a fundamental scale analysis, and experimental measurements. The regimes of droplet charging are determined by the relative magnitudes of the dimensionless Strouhal and electric Reynolds numbers, which are a function of the process (pressure forcing), advection, and charge relaxation time scales for charge transport. Optimal (net maximum) droplet charging has been identified to exist for conditions in which the electric Reynolds number is of the order of the inverse Strouhal number, i.e., the charge relaxation time is on the order of the pressure forcing (droplet formation) time scale. The conditions necessary for optimal droplet charging have been identified as a function of the dimensionless Debye number (i.e., liquid conductivity), external electric field (magnitude and duration), and atomization drive signal (frequency and amplitude). The specific regime of droplet charging also determines the functional relationship between droplet charge and charging electric field strength. The commonly expected linear relationship between droplet charge and external electric field strength is only found when either the inverse of the Strouhal number is less than the electric Reynolds number, i.e., the charge relaxation is slower than both the advection and external pressure forcing, or in the electrostatic limit, i.e., when charge relaxation is much faster than all other processes. The analysis provides a basic understanding of the dominant physics of droplet charging with implications to many important applications, such as electrospray mass spectrometry, ink jet printing, and drop-on-demand manufacturing.

  8. Droplet charging regimes for ultrasonic atomization of a liquid electrolyte in an external electric field

    PubMed Central

    Forbes, Thomas P.; Degertekin, F. Levent; Fedorov, Andrei G.

    2011-01-01

    Distinct regimes of droplet charging, determined by the dominant charge transport process, are identified for an ultrasonic droplet ejector using electrohydrodynamic computational simulations, a fundamental scale analysis, and experimental measurements. The regimes of droplet charging are determined by the relative magnitudes of the dimensionless Strouhal and electric Reynolds numbers, which are a function of the process (pressure forcing), advection, and charge relaxation time scales for charge transport. Optimal (net maximum) droplet charging has been identified to exist for conditions in which the electric Reynolds number is of the order of the inverse Strouhal number, i.e., the charge relaxation time is on the order of the pressure forcing (droplet formation) time scale. The conditions necessary for optimal droplet charging have been identified as a function of the dimensionless Debye number (i.e., liquid conductivity), external electric field (magnitude and duration), and atomization drive signal (frequency and amplitude). The specific regime of droplet charging also determines the functional relationship between droplet charge and charging electric field strength. The commonly expected linear relationship between droplet charge and external electric field strength is only found when either the inverse of the Strouhal number is less than the electric Reynolds number, i.e., the charge relaxation is slower than both the advection and external pressure forcing, or in the electrostatic limit, i.e., when charge relaxation is much faster than all other processes. The analysis provides a basic understanding of the dominant physics of droplet charging with implications to many important applications, such as electrospray mass spectrometry, ink jet printing, and drop-on-demand manufacturing. PMID:21301636

  9. Droplet charging regimes for ultrasonic atomization of a liquid electrolyte in an external electric field.

    PubMed

    Forbes, Thomas P; Degertekin, F Levent; Fedorov, Andrei G

    2011-01-01

    Distinct regimes of droplet charging, determined by the dominant charge transport process, are identified for an ultrasonic droplet ejector using electrohydrodynamic computational simulations, a fundamental scale analysis, and experimental measurements. The regimes of droplet charging are determined by the relative magnitudes of the dimensionless Strouhal and electric Reynolds numbers, which are a function of the process (pressure forcing), advection, and charge relaxation time scales for charge transport. Optimal (net maximum) droplet charging has been identified to exist for conditions in which the electric Reynolds number is of the order of the inverse Strouhal number, i.e., the charge relaxation time is on the order of the pressure forcing (droplet formation) time scale. The conditions necessary for optimal droplet charging have been identified as a function of the dimensionless Debye number (i.e., liquid conductivity), external electric field (magnitude and duration), and atomization drive signal (frequency and amplitude). The specific regime of droplet charging also determines the functional relationship between droplet charge and charging electric field strength. The commonly expected linear relationship between droplet charge and external electric field strength is only found when either the inverse of the Strouhal number is less than the electric Reynolds number, i.e., the charge relaxation is slower than both the advection and external pressure forcing, or in the electrostatic limit, i.e., when charge relaxation is much faster than all other processes. The analysis provides a basic understanding of the dominant physics of droplet charging with implications to many important applications, such as electrospray mass spectrometry, ink jet printing, and drop-on-demand manufacturing.

  10. Evaporation of Sessile Droplets on Slippery Liquid-Infused Porous Surfaces (SLIPS).

    PubMed

    Guan, Jian H; Wells, Gary G; Xu, Ben; McHale, Glen; Wood, David; Martin, James; Stuart-Cole, Simone

    2015-11-03

    Over the past decade, the most common approach to creating liquid shedding surfaces has been to amplify the effects of nonwetting surface chemistry, using micro/nanotexturing to create superhydrophobic and superoleophobic surfaces. Recently, an alternative approach using impregnation of micro/nanotextured surfaces with immiscible lubricating liquids to create slippery liquid-infused porous surfaces (SLIPS) has been developed. These types of surfaces open up new opportunities to study the mechanism of evaporation of sessile droplets in zero contact angle hysteresis situations where the contact line is completely mobile. In this study, we fabricated surfaces consisting of square pillars (10-90 μm) of SU-8 photoresist arranged in square lattice patterns with the center-to-center separation between pillars of 100 μm, on which a hydrophobic coating was deposited and the textures impregnated by a lubricating silicone oil. These surfaces showed generally low sliding angles of 1° or less for small droplets of water. Droplet profiles were more complicated than on nonimpregnated surfaces and displayed a spherical cap shape modified by a wetting ridge close to the contact line due to balancing the interfacial forces at the line of contact between the droplet, the lubricant liquid and air (represented by a Neumann triangle). The wetting ridge leads to the concept of a wetting "skirt" of lubricant around the base of the droplet. For the SLIP surfaces, we found that the evaporation of small sessile droplets (∼2 mm in diameter) followed an ideal constant contact angle mode where the apparent contact angle was defined from the intersection of the substrate profile with the droplet spherical cap profile. A theoretical model based on diffusion controlled evaporation was able to predict a linear dependence in time for the square of the apparent contact radius. The experimental data was in excellent quantitative agreement with the theory and enabled estimates of the diffusion

  11. An Integrated microfluidic platform for liquid droplet in gas flow generation with in liquid flow collection and manipulation

    NASA Astrophysics Data System (ADS)

    Tirandazi, Pooyan; Hidrovo, Carlos H.

    2016-11-01

    Discretization of biological samples and chemical reactions within digital droplets is a powerful technique which has rapidly emerged in many biochemical syntheses. The ability to generate, manipulate, and monitor millions of microdroplets in a short time provides great potential for high throughput screening and detection in microbiology. Here we report a microfluidic device for the formation of uniform microdroplets (50 μm-100 μm) using a high speed gas as the continuous phase. Gas-borne droplets are generated in a chip-based flow-focusing device fabricated in PDMS, and travel along the gaseous microchannel and are subsequently captured within a second liquid phase. The droplets are then transferred and collected in a minichamber and move into the manipulation section for further processing operations on the drops. All these steps are performed automatically in a single multilayer chip. This integrated microfluidic platform for generation, collection, and manipulation of the droplets provides great opportunities for monitoring and detection of gas-analytes. Utilizing the generated picoliter airborne droplets feature lower reaction times and higher transfer rates as compared to conventional air sampling techniques. Thus, it can greatly facilitate the investigation of airborne analytes by interrogation of the digital droplets using different analytical techniques. Furthermore, the presented liquid-in-gas generation method can be utilized for production of oil-free microparticles and microcapsules used in the food industry and for drug delivery.

  12. Adiabatic Compression Sensitivity of Liquid Fuels and Monopropellants

    DTIC Science & Technology

    2007-11-02

    Sensitivity of Liquid Fuels and Monopropellants " 46’b Internat’I Instrumentation Syrup (Bellevue, WA, 30 Apr- 04 May 00) (Statement A) (Deadline: 30 Dec...99) Adiabatic Compression Sensitivity of Liquid Fuels and Monopropellants Ismail M. K. Ismail Tom W. Hawkins Senior Engineer/Scientist Group Leader...hazard sensitivity, propellants, fuels, oxidizers ABSTRACT Liquid rocket fuels and monopropellants can be sensitive to rapid compression. Such liquids

  13. Diffusion controlled evaporation of a multicomponent droplet - Theoretical studies on the importance of variable liquid properties

    NASA Astrophysics Data System (ADS)

    Kneer, R.; Schneider, M.; Noll, B.; Wittig, S.

    1993-06-01

    A well-known multicomponent droplet vaporization model, the Diffusion Limit Model, has been extended to account for property variations in the liquid phase. The model has been tested for typical conditions of modern gas turbine combustors. The results for a hexane/tetradecane droplet show that the temperature- and concentration-dependence of the liquid properties affect the vaporization process, especially with regard to a reduced diffusional resistance. Additionally, remarkable variations of the refractive index are observed yielding helpful information for the estimation of errors in optical particle sizing techniques. Regarding comprehensive spray calculations, the use of the constant property formulation is recommended with improved reference values based on variable property calculations.

  14. Plasmon resonance of gold nanorods for all-optical drawing of liquid droplets

    NASA Astrophysics Data System (ADS)

    de Angelis, M.; Matteini, P.; Ratto, F.; Pini, R.; Coppola, S.; Grilli, S.; Vespini, V.; Ferraro, P.

    2013-10-01

    We present a laser-assisted system for dispensing liquid micro-droplets by near infrared illumination of a pyroelectric crystal functionalized with gold nanorods embedded into polyvinyl alcohol. The non-invasive near infrared source resonates with the plasmon oscillations of the gold nanorods, providing a controlled thermal stimulus able to generate the pyroelectric effect. The resulting electric field interacts electro-hydrodynamically with a liquid reservoir leading to precise drawing of micro-litre droplets. This laser-assisted electro-hydrodynamic technique may open the way to the development of more compact and non-invasive nano-dispensing devices.

  15. Passive Dew Droplet Removal from Hydrogen Sensors for Fuel Cell Applications

    NASA Astrophysics Data System (ADS)

    Kano, Masataka; Ishii, Makoto; Yoshinaga, Haruo; Esashi, Masayoshi; Tanaka, Shuji

    This paper describes three structures to passively remove condensed water droplets from a gas heat conduction type hydrogen sensor for fuel cell applications. The three structures are A: water-repellent coating surrounded by water-absorbing porous ceramic coating, B: suspended porous membrane over a water-repellent sensor surface and C: wettability gradient for water droplet elimination. A real hydrogen sensor was used as a platform for the water-droplet-removal structures. Using helium instead of hydrogen, A and B type sensors and a reference sensor without water-droplet-removal structures were tested in a wet and hot atmosphere simulating a fuel cell environment. B type sensor showed normal output even after exposure to a dew-condensing atmosphere, while the reference and A type sensors showed abnormal output, suggesting dew condensation on the sensor surfaces. For C type sensor, a photochromic compound film on a super-water-repellent undercoat, which changes its wettability by ultraviolet exposure, was used. It was confirmed that the wettability could be controlled by ultraviolet exposure from 157.9° to 72.8° in water contact angle.

  16. Collision Dynamics and Internal Mixing of Droplets of Non-Newtonian Liquids

    NASA Astrophysics Data System (ADS)

    Sun, Kai; Zhang, Peng; Law, Chung K.; Wang, Tianyou

    2015-11-01

    The efficient internal mixing of colliding droplets upon coalescence is critical to various technological processes such as color manipulation in ink-jet printing and the initiation of the liquid-phase reaction of gelled hypergolic propellants in rocket engines. Recognizing that such processes can be optimized by varying the impact inertia as well as employing fluids of non-Newtonian rheology, the head-on collision, coalescence, and internal mixing pattern between two impacting equal-sized droplets of non-Newtonian fluids is computationally investigated by using the lattice Boltzmann method. Results show that, with increasing non-Newtonian effects, droplet deformation and separation following coalescence is promoted for shear-thinning fluids, while permanent coalescence allowing an extended duration for mixing is promoted for shear-thickening fluids. Furthermore, large-scale internal mixing is promoted for the colliding droplets with larger shear-thinning disparity, while coalescence and mixing is synergistically facilitated for the collision between a shear-thinning droplet and a shear-thickening droplet. The individual and coupled influences of viscosity on the droplet deformation and impact inertia, internal motion, viscous loss, and merging of the colliding interfaces leading to the observed outcomes are mechanistically identified and described.

  17. Regular self-motion of a liquid droplet powered by the chemical marangoni effect.

    PubMed

    Nagai, Ken; Sumino, Yutaka; Yoshikawa, Kenichi

    2007-04-15

    We describe here our recent work on spontaneous regular motion of liquid droplet powered by the chemical Marangoni effect under spatially symmetric conditions. It is shown that a spontaneously crawling oil droplet on a glass substrate with a nonequilibrium chemical condition of cationic surfactant exhibits regular rhythmic motion in a quasi-one-dimensional vessel, whereas irregular motion is induced in a two-dimensionally isotropic environment. Such behavior of a droplet demonstrates that spontaneous regular motion can be generated under fluctuating conditions by imposing an appropriate geometry. As another system, we introduce alcohol droplet moving spontaneously on water surface. The droplet spontaneously forms a specific morphology depending on its volume, causing specific mode of translational motion. An alcohol droplet with a smaller volume floating on water surface moves irregularly. On the other hand, a droplet with a larger volume undergoes vectorial motion accompanied by deformation into an asymmetric shape. This result suggests a scenario on the emergence of regular motion coupled with geometrical pattern formation under far-from-equilibrium conditions.

  18. Role of radius on prewetting behavior in nematic liquid-crystal droplets

    NASA Astrophysics Data System (ADS)

    Kadivar, Erfan

    2009-07-01

    The prewetting phenomena in a nematic liquid crystal confined to a droplet embedded in a spherical solid surface are discussed. This paper is based on Landau-de Gennes theory and Nobili-Durand surface energy. By using a Maxwell construction, we find that the first-order boundary-layer transition inside of droplet which vanishes completely below a critical radius Rc when bulk nematic isotropic transition temperature is approached from above. We obtain a narrow temperature interval above the bulk nematic-isotropic phase transition which corresponds to nematic boundary layer inside of droplet. The interval length depends on surface potential and droplet radius. We also find that there is no critical radius for boundary transition when the nematic-isotropic transition temperature is approached from below.

  19. Continuous rotation of a cholesteric liquid crystalline droplet by a circularly polarized optical tweezers

    NASA Astrophysics Data System (ADS)

    Tamura, Yuta; Kimura, Yasuyuki

    2017-04-01

    We studied the opto-mechanical response of droplets composed of cholesteric liquid crystal (ChLC) to a circularly polarized optical tweezers. Although the alignment of LC molecular within a droplet depends on the relative ratio of the droplet diameter d to the helical pitch p, the optically induced rotation was found to be asymmetric to the direction of circularly polarized light irrespective to the inner molecular alignment. We studied the rotation of the droplets with various sizes, helical pitch (strength of chirality) and different chirality. In the case of d/p 1, the direction of the rotation was simply determined by chirality of ChLC and the rotation was also observed for linearly polarized light, which has already been reported by Yang et al.

  20. The shrinking instability of toroidal liquid droplets in the Stokes flow regime.

    PubMed

    Yao, Zhenwei; Bowick, Mark J

    2011-03-01

    We analyze the stability and dynamics of toroidal liquid droplets. In addition to the Rayleigh instabilities akin to those of a cylindrical droplet there is a shrinking instability that is unique to the topology of the torus and dominates in the limit that the aspect ratio is near one (fat tori). We first find an analytic expression for the pressure distribution inside the droplet. We then determine the velocity field in the bulk fluid, in the Stokes flow regime, by solving the biharmonic equation for the stream function. The flow pattern in the external fluid is analyzed qualitatively by exploiting symmetries. This elucidates the detailed nature of the shrinking mode and the swelling of the cross-section following from incompressibility. Finally the shrinking rate of fat toroidal droplets is derived by energy conservation.

  1. Dispersion of sound in a combustion duct by fuel droplets and soot particles

    NASA Technical Reports Server (NTRS)

    Miles, J. H.; Raftopoulos, D. D.

    1979-01-01

    Dispersion and attenuation of acoustic plane wave disturbances propagating in a ducted combustion system are studied. The dispersion and attenuation are caused by fuel droplet and soot emissions from a jet engine combustor. The attenuation and dispersion are due to heat transfer and mass transfer and viscous drag forces between the emissions and the ambient gas. Theoretical calculations show sound propagation at speeds below the isentropic speed of sound at low frequencies. Experimental results are in good agreement with the theory.

  2. Dispersion of sound in a combustion duct by fuel droplets and soot particles

    NASA Technical Reports Server (NTRS)

    Miles, J. H.; Raftopoulos, D. D.

    1979-01-01

    Dispersion and attenuation of acoustic plane wave disturbances propagating in a ducted combustion system are studied. The dispersion and attenuation are caused by fuel droplet and soot emissions from a jet engine combustor. The attenuation and dispersion are due to heat transfer and mass transfer and viscous drag forces between the emissions and the ambient gas. Theoretical calculations show sound propagation at speeds below the isentropic speed of sound at low frequencies. Experimental results are in good agreement with the theory.

  3. Nanoparticle self-assembly at the interface of liquid crystal droplets.

    PubMed

    Rahimi, Mohammad; Roberts, Tyler F; Armas-Pérez, Julio C; Wang, Xiaoguang; Bukusoglu, Emre; Abbott, Nicholas L; de Pablo, Juan J

    2015-04-28

    Nanoparticles adsorbed at the interface of nematic liquid crystals are known to form ordered structures whose morphology depends on the orientation of the underlying nematic field. The origin of such structures is believed to result from an interplay between the liquid crystal orientation at the particles' surface, the orientation at the liquid crystal's air interface, and the bulk elasticity of the underlying liquid crystal. In this work, we consider nanoparticle assembly at the interface of nematic droplets. We present a systematic study of the free energy of nanoparticle-laden droplets in terms of experiments and a Landau-de Gennes formalism. The results of that study indicate that, even for conditions under which particles interact only weakly at flat interfaces, particles aggregate at the poles of bipolar droplets and assemble into robust, quantized arrangements that can be mapped onto hexagonal lattices. The contributions of elasticity and interfacial energy corresponding to different arrangements are used to explain the resulting morphologies, and the predictions of the model are shown to be consistent with experimental observations. The findings presented here suggest that particle-laden liquid crystal droplets could provide a unique and versatile route toward building blocks for hierarchical materials assembly.

  4. Nanoparticle self-assembly at the interface of liquid crystal droplets

    PubMed Central

    Rahimi, Mohammad; Roberts, Tyler F.; Armas-Pérez, Julio C.; Wang, Xiaoguang; Bukusoglu, Emre; Abbott, Nicholas L.; de Pablo, Juan J.

    2015-01-01

    Nanoparticles adsorbed at the interface of nematic liquid crystals are known to form ordered structures whose morphology depends on the orientation of the underlying nematic field. The origin of such structures is believed to result from an interplay between the liquid crystal orientation at the particles’ surface, the orientation at the liquid crystal’s air interface, and the bulk elasticity of the underlying liquid crystal. In this work, we consider nanoparticle assembly at the interface of nematic droplets. We present a systematic study of the free energy of nanoparticle-laden droplets in terms of experiments and a Landau–de Gennes formalism. The results of that study indicate that, even for conditions under which particles interact only weakly at flat interfaces, particles aggregate at the poles of bipolar droplets and assemble into robust, quantized arrangements that can be mapped onto hexagonal lattices. The contributions of elasticity and interfacial energy corresponding to different arrangements are used to explain the resulting morphologies, and the predictions of the model are shown to be consistent with experimental observations. The findings presented here suggest that particle-laden liquid crystal droplets could provide a unique and versatile route toward building blocks for hierarchical materials assembly. PMID:25870304

  5. Physical understanding of gas-liquid annular flow and its transition to dispersed droplets

    NASA Astrophysics Data System (ADS)

    Kumar, Parmod; Das, Arup Kumar; Mitra, Sushanta K.

    2016-07-01

    Transformation from annular to droplet flow is investigated for co-current, upward gas-liquid flow through a cylindrical tube using grid based volume of fluid framework. Three transitional routes, namely, orificing, rolling, and undercutting are observed for flow transformation at different range of relative velocities between the fluids. Physics behind these three exclusive phenomena is described using circulation patterns of gaseous phase in the vicinity of a liquid film which subsequently sheds drop leading towards transition. Orifice amplitude is found to grow exponentially towards the core whereas it propagates in axial direction in a parabolic path. Efforts have been made to fit the sinusoidal profile of wave structure with the numerical interface contour at early stages of orificing. Domination of gas inertia over liquid flow has been studied in detail at the later stages to understand the asymmetric shape of orifice, leading towards lamella formation and droplet generation. Away from comparative velocities, circulations in the dominant phase dislodge the drop by forming either a ligament (rolling) or a bag (undercut) like protrusion in liquid. Study of velocity patterns in the plane of droplet dislodge reveals the underlying physics behind the disintegration and its dynamics at the later stages. Using numerical phase distributions, rejoining of dislodged droplet with liquid film as post-rolling consequences has been also proposed. A flow pattern map showing the transitional boundaries based on the physical mechanism is constructed for air-water combination.

  6. Dynamics of liquid metal droplets and jets influenced by a strong axial magnetic field

    NASA Astrophysics Data System (ADS)

    Hernández, D.; Karcher, Ch

    2017-07-01

    Non-contact electromagnetic control and shaping of liquid metal free surfaces is crucial in a number of high-temperature metallurgical processes like levitation melting and electromagnetic sealing, among others. Other examples are the electromagnetic bending or stabilization of liquid metal jets that frequently occur in casting or fusion applications. Within this context, we experimentally study the influence of strong axial magnetic fields on the dynamics of falling metal droplets and liquid metal jets. GaInSn in eutectic composition is used as test melt being liquid at room temperature. In the experiments, we use a cryogen-free superconducting magnet (CFM) providing steady homogeneous fields of up to 5 T and allowing a tilt angle between the falling melt and the magnet axis. We vary the magnetic flux density, the tilt angle, the liquid metal flow rate, and the diameter and material of the nozzle (electrically conducting/insulating). Hence, the experiments cover a parameter range of Hartmann numbers Ha, Reynolds numbers Re, and Weber numbers We within 0 < Ha < 440, 340 < Re < 4500, and 0.09 < We < 12.1. As major results we find that under the influence of the strong magnetic field, droplet rotation ceases and the droplets are stretched in the field direction. Moreover, we observe that the jet breakup into droplets (spheroidization) is suppressed, and in the case of electrically conducting nozzles and tilt, the jets are bent towards the field axis.

  7. Gas phase microreaction: nanomaterials synthesis via plasma exposure of liquid droplets

    NASA Astrophysics Data System (ADS)

    Maguire, Paul; Mahony, Charles; Kelsey, Colin; Hamilton, Neil; Askari, Sadegh; Macias-Montero, Manuel; Diver, Declan; Mariotti, Davide

    2015-09-01

    Plasma-liquid interactions are complex but offer considerable scope for use in nanomaterials synthesis. The introduction of individual picolitre micro-droplets into a steady-state low temperature plasma at atmospheric pressure, offers opportunities for enhanced scope and control of plasma-liquid chemistry and material properties. The gas-phase micro-reactor is similar in concept to liquid bubble microfluidics currently under intense research but with enhanced opportunities for scale-up. For nanomaterials and quantum dot synthesis, the addition of a liquid phase within the plasma expands considerably the scope for core-shell and alloy formation. The synthesis and encapsulation within a liquid droplet allows continuous delivery of nanoparticles to remote sites for plasma medicine, device fabrication or surface coating. We have synthesized Au nanoparticles in flight using AuHCl4 droplets with plasma flight times <0.1 ms. Also, Ag nanoparticles have been synthesized downstream via the delivery of plasma exposed water droplets onto AgNO3 laden substrates. Funding from EPSRC acknowledged (Grants EP/K006088/1 and EP/K006142/1).

  8. Liquid Fuels and Natural Gas in the Americas Analysis Brief

    EIA Publications

    2014-01-01

    This report examines the major energy trends and developments of the past decade in the Americas, focusing on liquid fuels and natural gas—particularly, reserves and resources, production, consumption, trade, and investment. The Americas, which include North America, Central America, the Caribbean, and South America, account for a significant portion of global supply, demand, and trade of both liquid fuels and natural gas. Liquid fuels include all petroleum and petroleum products, natural gas liquids, biofuels, and liquids derived from other hydrocarbon sources.

  9. Response of two-phase droplets to intense electromagnetic radiation

    NASA Technical Reports Server (NTRS)

    Spann, James F.; Maloney, Daniel J.; Lawson, William F.; Casleton, Kent H.

    1993-01-01

    The behavior of two-phase droplets subjected to high intensity radiation pulses is studied. Droplets are highly absorbing solids in weakly absorbing liquid medium. The objective of the study was to define heating thresholds required for causing explosive boiling and secondary atomization of the fuel droplet. The results point to mechanisms for energy storage and transport in two-phase systems.

  10. Response of two-phase droplets to intense electromagnetic radiation

    NASA Astrophysics Data System (ADS)

    Spann, James F.; Maloney, Daniel J.; Lawson, William F.; Casleton, Kent H.

    1993-04-01

    The behavior of two-phase droplets subjected to high intensity radiation pulses is studied. Droplets are highly absorbing solids in weakly absorbing liquid medium. The objective of the study was to define heating thresholds required for causing explosive boiling and secondary atomization of the fuel droplet. The results point to mechanisms for energy storage and transport in two-phase systems.

  11. Continuous Rotation of Achiral Nematic Liquid Crystal Droplets Driven by Heat Flux

    NASA Astrophysics Data System (ADS)

    Ignés-Mullol, Jordi; Poy, Guilhem; Oswald, Patrick

    2016-07-01

    Suspended droplets of cholesteric (chiral nematic) liquid crystals spontaneously rotate in the presence of a heat flux due to a temperature gradient, a phenomenon known as the Lehmann effect. So far, it is not clear whether this effect is due to the chirality of the phase and the molecules or only to the chirality of the director field. Here, we report the continuous rotation in a temperature gradient of nematic droplets of a lyotropic chromonic liquid crystal featuring a twisted bipolar configuration. The achiral nature of the molecular components leads to a random handedness of the spontaneous twist, resulting in the coexistence of droplets rotating in the two senses, with speeds proportional to the temperature gradient and inversely proportional to the droplet radius. This result shows that a macroscopic twist of the director field is sufficient to induce a rotation of the droplets, and that the phase and the molecules do not need to be chiral. This suggests that one can also explain the Lehmann rotation in cholesteric liquid crystals without introducing the Leslie thermomechanical coupling—only present in chiral mesophases. An explanation based on the Akopyan and Zeldovich theory of thermomechanical effects in nematics is proposed and discussed.

  12. Wetted Foam Liquid Fuel ICF Target Experiments

    NASA Astrophysics Data System (ADS)

    Olson, R.; Leeper, R.; Yi, A.; Zylstra, A.; Kline, J.; Peterson, R.; Braun, T.; Biener, J.; Biener, M.; Kozioziemski, B.; Sater, J.; Hamza, A.; Nikroo, A.; Berzak Hopkins, L.; Lepape, S.; MacKinnon, A.; Meezan, N.

    2015-11-01

    We are developing a new NIF experimental platform that employs wetted foam liquid fuel layer ICF capsules. We plan to use the liquid fuel layer capsules in a NIF experimental campaign to explore the relationship between hot spot convergence ratio (CR) and the robustness of hot spot formation. DT or D2 Liquid Layer ICF capsules allow for flexibility in hot spot convergence ratio via the adjustment of the initial cryogenic capsule temperature and, hence, DT vapor density. Our hypothesis is that the predictive capability of hot spot formation is robust and 1D-like for a relatively low CR hot spot (CR =15), but will become less reliable as hot spot CR is increased to CR>20. Simulations indicate that backing off on hot spot CR is an excellent way to reduce capsule instability growth and to improve robustness to low-mode x-ray flux asymmetries. In these initial experiments, we are testing our hypothesis by measuring hot spot size, neutron yield, ion temperature, and burn width to infer hot spot pressure and compare to predictions for implosions with hot spot CR's in the range of 12 to 25. Larger scale experiments are also being designed, with the longer-term objective of developing a liquid fuel layer ICF capsule platform with robust thermonuclear burn, modest CR, and significant α-heating with burn propagation.

  13. Continuous transfer of liquid metal droplets across a fluid-fluid interface within an integrated microfluidic chip.

    PubMed

    Gol, Berrak; Tovar-Lopez, Francisco J; Kurdzinski, Michael E; Tang, Shi-Yang; Petersen, Phred; Mitchell, Arnan; Khoshmanesh, Khashayar

    2015-06-07

    Micro scale liquid metal droplets have been hailed as the potential key building blocks of future micro-electro-mechanical systems (MEMS). However, most of the current liquid metal enabled systems involve millimeter scale droplets, which are manually injected onto the desired locations of the microchip. Despite its simplicity, this method is impractical for patterning large arrays or complex systems based on micro scale droplets. Here, we present a microfluidic chip, which integrates continuous generation of micro scale galinstan droplets in glycerol, and the hydrodynamic transfer of these droplets into sodium hydroxide (NaOH) solution. Observation via high-speed imaging along with computational fluid dynamics (CFD) analysis are utilised to comprehend the lateral migration of droplets from the glycerol to NaOH fluid. This platform is simple, can be readily integrated into other microfluidic systems, and creates flexibility by separating the continuous phase for droplet generation from the eventual target carrier fluid within a monolithic chip.

  14. The vaporizing behavior of the fuel droplet of water-in-oil emulsions on the hot surface

    NASA Astrophysics Data System (ADS)

    Kimoto, Kyoji; Owashi, Yukio; Omae, Yoshihiro

    1986-12-01

    Experiments were carried out to investigate qualitatively the effects of the emulsion internal phase structure, such as the size distribution of water droplets, on the microexplosion phenomena of water-in-'A'-heavy-oil emulsified droplets vaporizing on a hot surface. The results confirm that the size distribution of water droplets in the emulsified fuels plays a very important role in the boilng phenomena, in spite of the same water content included in the fuels. That is, emulsified fuel 1 with fine- and uniform-size distribution of the internal water droplets has a longer life time than the neat fuel ('A' heavy oil) due to a distinctive feature such as 'two stage vaporization'. In contrast, emulsified fuel 2 with coarse droplets has a life time less than a half of the neat fuel in the film boiling region. High-speed motion analyses revealed that such a remarkable promotion effect of vaporization was caused by the destruction of the vapor film due to the 'violent microexplosion' of coarse-coalescent water droplets.

  15. Combustion engine for solid and liquid fuels

    NASA Technical Reports Server (NTRS)

    Pabst, W.

    1986-01-01

    A combustion engine having no piston, a single cylinder, and a dual-action, that is applicable for solid and liquid fuels and propellants, and that functions according to the principle of annealing point ignition is presented. The invention uses environmentally benign amounts of fuel and propellants to produce gas and steam pressure, and to use a simple assembly with the lowest possible consumption and constant readiness for mixing and burning. The advantage over conventional combustion engines lies in lower consumption of high quality igniting fluid in the most cost effective manner.

  16. Metal-deactivating additives for liquid fuels

    SciTech Connect

    Boneva, M.I.; Ivanov, S.K.; Kalitchin, Z.D.; Tanielyan, S.K.; Terebenina, A.; Todorova, O.I.

    1995-05-01

    The metal-deactivating and the antioxidant properties of 1-phenyl-3-methylpyrazolone-5 derivatives have been investigated both in the model reaction of low temperature oxidation of ethylbenzene and in gasoline oxidation. The study of the ability of these derivatives to reduce the catalytic effect of copper naphthenate demonstrates that they are promising as metal deactivating additives for light fuels. Some of the pyrazolone compounds appear to be of special interest for the long-term storage of liquid fuels due to their action as multifunctional inhibitors.

  17. Uranium droplet core nuclear rocket

    NASA Technical Reports Server (NTRS)

    Anghaie, Samim

    1991-01-01

    Uranium droplet nuclear rocket is conceptually designed to utilize the broad temperature range ofthe liquid phase of metallic uranium in droplet configuration which maximizes the energy transfer area per unit fuel volume. In a baseline system dissociated hydrogen at 100 bar is heated to 6000 K, providing 2000 second of Isp. Fission fragments and intense radian field enhance the dissociation of molecular hydrogen beyond the equilibrium thermodynamic level. Uranium droplets in the core are confined and separated by an axisymmetric vortex flow generated by high velocity tangential injection of hydrogen in the mid-core regions. Droplet uranium flow to the core is controlled and adjusted by a twin flow nozzle injection system.

  18. Uranium droplet core nuclear rocket

    NASA Technical Reports Server (NTRS)

    Anghaie, Samim

    1991-01-01

    Uranium droplet nuclear rocket is conceptually designed to utilize the broad temperature range ofthe liquid phase of metallic uranium in droplet configuration which maximizes the energy transfer area per unit fuel volume. In a baseline system dissociated hydrogen at 100 bar is heated to 6000 K, providing 2000 second of Isp. Fission fragments and intense radian field enhance the dissociation of molecular hydrogen beyond the equilibrium thermodynamic level. Uranium droplets in the core are confined and separated by an axisymmetric vortex flow generated by high velocity tangential injection of hydrogen in the mid-core regions. Droplet uranium flow to the core is controlled and adjusted by a twin flow nozzle injection system.

  19. Heat transfer and flow studies of the liquid droplet heat exchanger

    NASA Technical Reports Server (NTRS)

    Bruckner, A. P.; Shariatmadar, A.

    1987-01-01

    This paper describes a lightweight, highly effective liquid droplet heat exchanger (LDHX) concept for thermal management in space. Heat is transferred by direct contact between fine droplets (100 to 300 micron diameter) of a low vapor pressure liquid and an inert working gas. Complete separation of the droplet and gas media in the microgravity environment is accomplished by configuring the LDHX as a vortex chamber. A quasi-one-dimensional, two-phase heat transfer model of the LDHX is developed and used to investigate the potential use of the LDHX for both heating and cooling the working gas in a 100-k W(e) Braytoan cycle. Experimental studies on a small scale LDHX chamber, using air and water as the two media, show excellent agreement with the theoretical model.

  20. Liquid water content and droplet size calibration of the NASA Lewis Icing Research Tunnel

    NASA Technical Reports Server (NTRS)

    Ide, Robert F.

    1989-01-01

    The icing research tunnel at the NASA Lewis Research Center underwent a major rehabilitation in 1986 to 1987, necessitating recalibration of the icing cloud. The methods used in the recalibration, including the procedure used to establish a uniform icing cloud and the use of a standard icing blade technique for measurement of liquid water content are described. PMS Forward Scattering Spectrometer and Optical Array probes were used for measurement of droplet size. Examples of droplet size distributions are shown for several median volumetric diameters. Finally, the liquid water content/droplet size operating envelopes of the icing tunnel are shown for a range of airspeeds and are compared to the FAA icing certification criteria.

  1. Liquid water content and droplet size calibration of the NASA Lewis Icing Research Tunnel

    NASA Technical Reports Server (NTRS)

    Ide, Robert F.

    1990-01-01

    The icing research tunnel at the NASA Lewis Research Center underwent a major rehabilitation in 1986 to 1987, necessitating recalibration of the icing cloud. The methods used in the recalibration, including the procedure used to establish a uniform icing cloud and the use of a standard icing blade technique for measurement of liquid water content are described. PMS Forward Scattering Spectrometer and Optical Array probes were used for measurement of droplet size. Examples of droplet size distributions are shown for several median volumetric diameters. Finally, the liquid water content/droplet size operating envelopes of the icing tunnel are shown for a range of airspeeds and are compared to the FAA icing certification criteria.

  2. Big savings from small holes. [Liquid Droplet Radiator project for space vehicles

    NASA Technical Reports Server (NTRS)

    White, Alan

    1989-01-01

    The status and results to date of the NASA-Lewis/USAF Astronautics study of technology for large spacecraft heat-dissipation by means of liquid-droplet radiation (LDR) are discussed. The LDR concept uses a droplet generator to create billions of 200-micron droplets of a heatsink fluid which will cool through radiation into deep space as they fly toward a dropet collector. This exposure to the space environment entails the maintenance of vapor pressure as low as 10 to the -7th torr; the fluid must also be very stable chemically. While certain oils are good fluids for LDR use at low temperatures, higher-temperature heatsink fluids include Li, Sn, and Ga liquid metals.

  3. Rapid Vaporization and Heating of Two Parallel Fuel Droplet Streams

    DTIC Science & Technology

    1986-04-01

    injected in a hot gas. With the assumption of a constant relative ’velocity between the gas and liquid phases (inviscid approximation), a system of partial...Disftimotr - Mited.1912MATTHEw, •-•.- 094f~ Techr.1c,4, ’nforffgbI DWI=iI Presented at the 1986 Spring Technical Meeting Canadian and Western States Sections...The Combustion Institute Banff , Alberta, Canada April 27-3u, 1986 $ , I• 0 ~ ~ ~ !7 Abstract An analysis is presented of the mechanism ,• heat transfer

  4. Liquid-Water Uptake and Removal in PEM Fuel-Cell Components

    SciTech Connect

    Das, Prodip K.; Gunterman, Haluna P.; Kwong, Anthony; Weber, Adam Z.

    2011-09-23

    Management of liquid water is critical for optimal fuel-cell operation, especially at low temperatures. It is therefore important to understand the wetting properties and water holdup of the various fuel-cell layers. While the gas-diffusion layer is relatively hydrophobic and exhibits a strong intermediate wettability, the catalyst layer is predominantly hydrophilic. In addition, the water content of the ionomer in the catalyst layer is lower than that of the bulk membrane, and is affected by platinum surfaces. Liquid-water removal occurs through droplets on the surface of the gas-diffusion layer. In order to predict droplet instability and detachment, a force balance is used. While the pressure or drag force on the droplet can be derived, the adhesion or surface-tension force requires measurement using a sliding-angle approach. It is shown that droplets produced by forcing water through the gas-diffusion layer rather than placing them on top of it show much stronger adhesion forces owing to the contact to the subsurface water.

  5. Computational simulation of liquid fuel rocket injectors

    NASA Technical Reports Server (NTRS)

    Landrum, D. Brian

    1994-01-01

    A major component of any liquid propellant rocket is the propellant injection system. Issues of interest include the degree of liquid vaporization and its impact on the combustion process, the pressure and temperature fields in the combustion chamber, and the cooling of the injector face and chamber walls. The Finite Difference Navier-Stokes (FDNS) code is a primary computational tool used in the MSFC Computational Fluid Dynamics Branch. The branch has dedicated a significant amount of resources to development of this code for prediction of both liquid and solid fuel rocket performance. The FDNS code is currently being upgraded to include the capability to model liquid/gas multi-phase flows for fuel injection simulation. An important aspect of this effort is benchmarking the code capabilities to predict existing experimental injection data. The objective of this MSFC/ASEE Summer Faculty Fellowship term was to evaluate the capabilities of the modified FDNS code to predict flow fields with liquid injection. Comparisons were made between code predictions and existing experimental data. A significant portion of the effort included a search for appropriate validation data. Also, code simulation deficiencies were identified.

  6. Bi-Component Droplet Combustion Experiment Designed

    NASA Technical Reports Server (NTRS)

    Dietrich, Daniel L.

    2002-01-01

    The combustion of liquid fuels is a major source of energy in the world today, and the majority of these fuels are burned in the form of a spray. The research at the NASA Glenn Research Center in droplet combustion has the overall goal of providing a better understanding of spray combustion by studying the smallest element in a spray, the single droplet. The Bi-Component Droplet Combustion Experiment (BCDCE) extends the work at Glenn from pure, or single-component, fuels to an idealized liquid fuel composed of two completely miscible components. The project is a collaborative effort between Glenn and Prof. B.D. Shaw of the University of California, Davis. The BCDCE project is planned to fly onboard the International Space Station in the Multi-User Droplet Combustion Apparatus. The unique feature of this experiment is that it will be the first droplet combustion experiment to perform a detailed characterization of the flow inside a liquid fuel droplet. The experiment will use a relatively new technique called Digital Particle Imaging Velocimetry (DPIV) to characterize the liquid flow. In this technique, very small (approx. 5-mm diameter) particles are dispersed throughout a liquid droplet. These particles are illuminated by a thin laser sheet. Images of the particle motion are recorded on a computer, which then tracks the motion of the particles to determine the flow characteristics.

  7. Liquid fuels from the hydropyrolysis of biomass

    SciTech Connect

    Bodle, W.W.; Wright, K.A.

    1982-09-01

    A process designed to produce principally liquid fuel from Hawaiian biomass has been completed recently. This system consists of short residence-time pyrolysis of solids, entrained in a hydrogen atmosphere. This technique, which has been extensively developed at IGT for conversion of lignite, is termed HYFLEX. Following reaction at about 1100/sup 0/F (595/sup 0/C) and 200 psig (1.4 MPa), char and liquids are separated from the reactor outlet gas. Since fuel gas is not a desirable product at the location contemplated, the remaining gas is reformed with steam for production of a high-hydrogen-content gas which is recycled to the HYFLEX reactor. Bench-scale experiments were conducted with eucalyptus wood and leucaena wood feeds to establish data for process design. This paper describes the results of the wood tests and their comparison with similar data on peat. (JMT)

  8. Droplet vaporization in supercritical pressure environments

    NASA Astrophysics Data System (ADS)

    Farrell, Patrick V.; Peters, Bruce D.

    For most liquid-fueled combustion systems the behavior of the fuel as it is introduced to the combustion zone, often by spray injection, will have a significant impact on combustion. The subsequent combustion may be affected to a considerable degree by the initial spread of the liquid, break-up of larger fuel sheets and droplets into droplets of various sizes, droplet vaporization, and diffusion of gaseous fuel. Among the many factors which affect spray break-up and droplet vaporization are the environmental conditions into which the spray is introduced. For both diesel engines and rockets the environment pressure and temperature may be above the critical pressure and temperature of the injected fuel. In a compression-ignition internal combustion engine, the environment consists primarily of air, at pressures from 20 to 100 atmospheres and temperatures ranging from 900 to 1500 K. Even higher pressures are encountered in turbocharged diesels. A typical diesel reference fuel, dodecane, has a thermodynamic critical pressure of about 17 atmospheres, and a critical temperature of 600 K. Fuel is injected into a diesel engine environment in which ambient pressures exceed the critical pressure. While droplet temperatures are subcritical at first, they may rise to the critical temperature or higher. This paper will survey current understanding of supercritical pressure droplet vaporization. Specifically, the topics covered will include: liquid phase behavior; vapor phase behavior; thermodynamic and transport properties; droplet distribution and break-up; micro-explosions; and effects of microgravity.

  9. Self-fueled biomimetic liquid metal mollusk.

    PubMed

    Zhang, Jie; Yao, Youyou; Sheng, Lei; Liu, Jing

    2015-04-24

    A liquid metal motor that can "eat" aluminum food and then move spontaneously and swiftly in various solution configurations and structured channels for more than 1 h is discovered. Such a biomimetic mollusk is highly shape self-adaptive by closely conforming to the geometrical space it voyages in. The first ever self-fueled pump is illustrated as one of its typical practical utilizations.

  10. Terminal Liquid Mass Fractions and Terminal Mean Droplet Sizes in He Free-Jet Expansions

    SciTech Connect

    Knuth, E. L.; Kornilov, O.; Toennies, J. P.

    2011-05-20

    The terminal liquid mass fraction in He free-jet expansions is deduced from time-of-flight measurements using conservation of energy. Both the present results and results from prior measurements are correlated using a scaling parameter which was used previously for correlating droplet size as a function of source conditions. Deduced values of the mass fraction range from 0.047 to 0.42. The terminal mean droplet size is determined using a novel technique based on a size-dependent attenuation of the beam droplets when impacted by electrons. The determined sizes are in agreement with sizes obtained previously by crossing the droplet beam with an atomic beam, confirming the suitability of the present technique, which is relatively simple in comparison with crossing the droplet beam with an atomic beam. Measured values of the terminal velocity of the droplets are compared with values calculated for a model in which real-fluid properties are used for the enthalpy in the source but conversion of heat of condensation into energy of directed motion is neglected. The deviations from perfect-gas behavior in free-jet expansions are shown to be due to real-fluid properties and condensation.

  11. Specific detection of avidin-biotin binding using liquid crystal droplets.

    PubMed

    Khan, Mashooq; Park, Soo-Young

    2015-03-01

    Poly(acrylicacid-b-4-cynobiphenyl-4'-undecylacrylate) (PAA-b-LCP)-functionalized 4-cyano-4'-pentylbiphenyl (5CB) droplets were made by using microfluidic technique. The PAA chains on the 5CB droplets, were biotinylated, and used to specifically detect avidin-biotin binding at the 5CB/aqueous interface. The avidin-biotin binding was characterized by the configurational change (from radial to bipolar) of the 5CB droplets, as observed through a polarized optical microscope. The maximum biotinylation was obtained by injecting a >100 μg/mL biotin aqueous solution, which enabled a limit of detection of 0.5 μg/mL avidin. This droplet biosensor could specifically detect avidin against other proteins such as bovine serum albumin, lysozyme, hemoglobin, and chymotrypsinogen solutions. Avidin detection with 5CBPAA-biotin droplets having high sensitivity, specificity, and stability demonstrates new applications of the functionalized liquid crystal droplets that can detect specific proteins or other analytes through a ligand/receptor model.

  12. Terminal Liquid Mass Fractions and Terminal Mean Droplet Sizes in He Free-Jet Expansions

    NASA Astrophysics Data System (ADS)

    Knuth, E. L.; Kornilov, O.; Toennies, J. P.

    2011-05-01

    The terminal liquid mass fraction in He free-jet expansions is deduced from time-of-flight measurements using conservation of energy. Both the present results and results from prior measurements are correlated using a scaling parameter which was used previously for correlating droplet size as a function of source conditions. Deduced values of the mass fraction range from 0.047 to 0.42. The terminal mean droplet size is determined using a novel technique based on a size-dependent attenuation of the beam droplets when impacted by electrons. The determined sizes are in agreement with sizes obtained previously by crossing the droplet beam with an atomic beam, confirming the suitability of the present technique, which is relatively simple in comparison with crossing the droplet beam with an atomic beam. Measured values of the terminal velocity of the droplets are compared with values calculated for a model in which real-fluid properties are used for the enthalpy in the source but conversion of heat of condensation into energy of directed motion is neglected. The deviations from perfect-gas behavior in free-jet expansions are shown to be due to real-fluid properties and condensation.

  13. Near-global survey of effective droplet radii in liquid water clouds using ISCCP data

    NASA Technical Reports Server (NTRS)

    Han, Qingyan; Rossow, William B.; Lacis, Andrew B.

    1994-01-01

    A global survey of cloud particle size variations can provide crucial constraints on how cloud processes determine cloud liquid water contents and their variation with temperature, and further, may indicate the magnitude of aerosol effects on clouds. A method, based on a complete radiative transfer model for Advanced Very High Resolution Radiometer (AVHRR)-measured radiances, is described for retrieving cloud particle radii in liquid water clouds from satellite data currently available from the International Satellite Cloud Climatology Project. Results of sensitivity tests and validation studies provide error estimates. AVHRR data from NOAA-9 and NOAA-10 have been analyzed for January, April, July and October in 1987 and 1988. The results of this first survey reveal systematic continental and maritime differences and hemispheric contrasts that are indicative of the effects of associated aerosol concentration differences: cloud droplet radii in continental water clouds are about 2-3 micrometers smaller than in marine clouds, and droplet radii are about 1 micrometer smaller in marine clouds of the Northern Hemisphere than in the Southern Hemisphere. The height dependencies of cloud droplet radii in continental and marine clouds are also consistent with differences in the vertical profiles of aerosol concentration. Significant seasonal and diurnal variations of effective droplet radii are also observed, particularly at lower latitudes. Variations of the relationship between cloud optical thickness and droplet radii may indicate variations in cloud microphysical regimes.

  14. Reimagining liquid transportation fuels : sunshine to petrol.

    SciTech Connect

    Johnson, Terry Alan; Hogan, Roy E., Jr.; McDaniel, Anthony H.; Siegel, Nathan Phillip; Dedrick, Daniel E.; Stechel, Ellen Beth; Diver, Richard B., Jr.; Miller, James Edward; Allendorf, Mark D.; Ambrosini, Andrea; Coker, Eric Nicholas; Staiger, Chad Lynn; Chen, Ken Shuang; Ermanoski, Ivan; Kellog, Gary L.

    2012-01-01

    Two of the most daunting problems facing humankind in the twenty-first century are energy security and climate change. This report summarizes work accomplished towards addressing these problems through the execution of a Grand Challenge LDRD project (FY09-11). The vision of Sunshine to Petrol is captured in one deceptively simple chemical equation: Solar Energy + xCO{sub 2} + (x+1)H{sub 2}O {yields} C{sub x}H{sub 2x+2}(liquid fuel) + (1.5x+.5)O{sub 2} Practical implementation of this equation may seem far-fetched, since it effectively describes the use of solar energy to reverse combustion. However, it is also representative of the photosynthetic processes responsible for much of life on earth and, as such, summarizes the biomass approach to fuels production. It is our contention that an alternative approach, one that is not limited by efficiency of photosynthesis and more directly leads to a liquid fuel, is desirable. The development of a process that efficiently, cost effectively, and sustainably reenergizes thermodynamically spent feedstocks to create reactive fuel intermediates would be an unparalleled achievement and is the key challenge that must be surmounted to solve the intertwined problems of accelerating energy demand and climate change. We proposed that the direct thermochemical conversion of CO{sub 2} and H{sub 2}O to CO and H{sub 2}, which are the universal building blocks for synthetic fuels, serve as the basis for this revolutionary process. To realize this concept, we addressed complex chemical, materials science, and engineering problems associated with thermochemical heat engines and the crucial metal-oxide working-materials deployed therein. By project's end, we had demonstrated solar-driven conversion of CO{sub 2} to CO, a key energetic synthetic fuel intermediate, at 1.7% efficiency.

  15. Coupled Mechanisms of Precipitation and Atomization in Burning Nanofluid Fuel Droplets.

    PubMed

    Miglani, Ankur; Basu, Saptarshi

    2015-10-08

    Understanding the combustion characteristics of fuel droplets laden with energetic nanoparticles (NP) is pivotal for lowering ignition delay, reducing pollutant emissions and increasing the combustion efficiency in next generation combustors. In this study, first we elucidate the feedback coupling between two key interacting mechanisms, namely, secondary atomization and particle agglomeration; that govern the effective mass fraction of NPs within the droplet. Second, we show how the initial NP concentration modulates their relative dominance leading to a master-slave configuration. Secondary atomization of novel nanofuels is a crucial process since it enables an effective transport of dispersed NPs to the flame (a pre-requisite condition for NPs to burn). Contrarily, NP agglomeration at the droplet surface leads to shell formation thereby retaining NPs inside the droplet. In particular, we show that at dense concentrations shell formation (master process) dominates over secondary atomization (slave) while at dilute particle loading it is the high frequency bubble ejections (master) that disrupt shell formation (slave) through its rupture and continuous outflux of NPs. This results in distinct combustion residues at dilute and dense concentrations, thereby providing a method of manufacturing flame synthesized microstructures with distinct morphologies.

  16. Coupled Mechanisms of Precipitation and Atomization in Burning Nanofluid Fuel Droplets

    PubMed Central

    Miglani, Ankur; Basu, Saptarshi

    2015-01-01

    Understanding the combustion characteristics of fuel droplets laden with energetic nanoparticles (NP) is pivotal for lowering ignition delay, reducing pollutant emissions and increasing the combustion efficiency in next generation combustors. In this study, first we elucidate the feedback coupling between two key interacting mechanisms, namely, secondary atomization and particle agglomeration; that govern the effective mass fraction of NPs within the droplet. Second, we show how the initial NP concentration modulates their relative dominance leading to a master-slave configuration. Secondary atomization of novel nanofuels is a crucial process since it enables an effective transport of dispersed NPs to the flame (a pre-requisite condition for NPs to burn). Contrarily, NP agglomeration at the droplet surface leads to shell formation thereby retaining NPs inside the droplet. In particular, we show that at dense concentrations shell formation (master process) dominates over secondary atomization (slave) while at dilute particle loading it is the high frequency bubble ejections (master) that disrupt shell formation (slave) through its rupture and continuous outflux of NPs. This results in distinct combustion residues at dilute and dense concentrations, thereby providing a method of manufacturing flame synthesized microstructures with distinct morphologies. PMID:26446366

  17. Droplet impact dynamics for two liquids impinging on anisotropic superhydrophobic surfaces

    NASA Astrophysics Data System (ADS)

    Pearson, John T.; Maynes, Daniel; Webb, Brent W.

    2012-09-01

    Droplet impingement experiments were performed on grooved hydrophobic surfaces with cavity fractions of 0, 80, and 93 % using droplets of water and a 50 %/50 % water/glycerol mixture. The influence of liquid viscosity, cavity fraction, and spreading direction, relative to the surface grooves, is explored qualitatively and quantitatively. The maximum droplet spread diameter, velocity of the rebounding jet, and the time delay between droplet impact and jet emission were characterized for Weber numbers, We, based on droplet impact speed and diameter, up to 500. The unequal shear stresses and contact angles influence the maximum spread diameters in the two primary spread directions. At We > 100, the ratio of the spread diameter along the direction of the grooves to the spread diameter perpendicular to the grooves increases above unity with increasing We. The maximum droplet spread diameter is compared to recent predictive models, and the data reveal differing behavior for the two fluids considered. The results also reveal the existence of very high relative jet velocities in the range 5 ≤ We ≤ 15 for water droplets, while such jets were not observed for the more viscous mixture. Further, in the range 115 ≤ We ≤ 265, the water/glycerol jet formation dynamics are radically different from the water behavior. Most evident is the existence of two-pronged jets, which arise from the anisotropy of the surface and the unequal shear stresses and contact angles that prevail on the surfaces. It is these influences that give rise to differences in the maximum spread diameters in the two primary spread directions. Similar two-pronged jet emission was observed for water over the very narrow range of We from 91 to 96. The issuing jet velocities were also observed to increase with increasing cavity fraction for both fluids and over the entire range of We explored. Lastly, the elapsed time between droplet impact and jet emission decreased with increasing cavity fraction.

  18. Active suppression of vortex-driven combustion instability using controlled liquid-fuel injection

    NASA Astrophysics Data System (ADS)

    Pang, Bin

    Combustion instabilities remain one of the most challenging problems encountered in developing propulsion and power systems. Large amplitude pressure oscillations, driven by unsteady heat release, can produce numerous detrimental effects. Most previous active control studies utilized gaseous fuels to suppress combustion instabilities. However, using liquid fuel to suppress combustion instabilities is more realistic for propulsion applications. Active instability suppression in vortex-driven combustors using a direct liquid fuel injection strategy was theoretically established and experimentally demonstrated in this dissertation work. Droplet size measurements revealed that with pulsed fuel injection management, fuel droplet size could be modulated periodically. Consequently, desired heat release fluctuation could be created. If this oscillatory heat release is coupled with the natural pressure oscillation in an out of phase manner, combustion instabilities can be suppressed. To identify proper locations of supplying additional liquid fuel for the purpose of achieving control, the natural heat release pattern in a vortex-driven combustor was characterized in this study. It was found that at high Damkohler number oscillatory heat release pattern closely followed the evolving vortex front. However, when Damkohler number became close to unity, heat release fluctuation wave no longer coincided with the coherent structures. A heat release deficit area was found near the dump plane when combustor was operated in lean premixed conditions. Active combustion instability suppression experiments were performed in a dump combustor using a controlled liquid fuel injection strategy. High-speed Schlieren results illustrated that vortex shedding plays an important role in maintaining self-sustained combustion instabilities. Complete combustion instability control requires total suppression of these large-scale coherent structures. The sound pressure level at the excited dominant

  19. Investigation of the Extinguishing Features for Liquid Fuels and Organic Flammable Liquids Atomized by a Water Flow

    NASA Astrophysics Data System (ADS)

    Voytkov, Ivan V.; Zabelin, Maksim V.; Vysokomornaya, Olga V.

    2016-02-01

    The processes of heat and mass transfer were investigated experimentally while moving and evaporating the atomized water flow in high-temperature combustion products of typical liquid fuels and organic flammable liquids: gasoline, kerosene, acetone, crude oil, industrial alcohol. We determined typical periods of liquid extinguishing by an atomized water flow of various dispersability. Data of the discharge of extinguishing medium corresponding to various parameters of atomization and duration of using the atomization devices was presented. It is shown that Um≈3.5 m/s is a minimal outflow velocity of droplets during moving while passing the distance of 1m in the high-temperature gas medium to stop the combustion of organic liquids.

  20. A New Finite-Conductivity Droplet Evaporation Model Including Liquid Turbulence Effect

    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 droplets of an evaporating spray is presented in this paper. The model is an extension of the T-blob and T-TAB atomization/spray model of Trinh and Chen [9]. This finite conductivity model is based on the two-temperature film theory in which the turbulence characteristics of the droplet are used to estimate the effective thermal diffusivity for the liquid-side film thickness. Both one-way and two-way coupled calculations were performed to investigate the performance cf this model against the published experimental data.

  1. Equilibrium Configuration in a Nematic Liquid Crystal Droplet with Homeotropic Anchoring of Finite Strength

    NASA Astrophysics Data System (ADS)

    Kanke, Masaki; Sasaki, Kazuo

    2013-09-01

    Equilibrium configuration of order parameter in a nematic liquid crystal droplet with homeotropic anchoring of finite strength at the surface is studied numerically by using the Landau--de Gennes approach. It is found that a hedgehog-like configuration with a disclination loop of a small radius is stable for strong anchoring while an axial configuration without defect is stable for weak anchoring. A first-order phase transition from one configuration to the other occurs as the strength of the anchoring is varied. The critical anchoring strength turns out to increase almost linearly with the inverse of the droplet radius.

  2. Droplet Burns in the Fiber-Supported Droplet Combustion Experiment

    NASA Technical Reports Server (NTRS)

    2003-01-01

    A fuel droplet burns in the Fiber-Supported Droplet Combustion (FSDC) Experiment on STS-94, July 4 1997, MET:02/19:20 (approximate). This experiment, performed in the Middeck Glovebox, allows us to study the burning of fuels such as n-heptane, n-decane, methanol, ethanol, methanol/water mixtures, and heptane/hexadecane mixtures in droplets as large as 6 mm (nearly 1/4 inch). In this sequence, you see the burn of a 5mm droplet of n-heptane, in a 30% O2/He environment at 1 atmosphere pressure. The droplet (looking bright pink because of reflected light) hangs suspended from the supporting fiber. FSDC-2 studied fundamental phenomena related to liquid fuel droplet combustion in air. Pure fuels and mixtures of fuels were burned as isolated single and dual droplets with and without forced air convection. The FSDC guest investigator was Forman Williams, University of California, San Diego. The experiment was part of the space research investigations conducted during the Microgravity Science Laboratory-1R mission (STS-94, July 1-17 1997). Advanced combustion experiments will be a part of investigations plarned for the International Space Station. (279KB JPEG, 1350 x 2026 pixels; downlinked video, higher quality not available) The MPG from which this composite was made is available at http://mix.msfc.nasa.gov/ABSTRACTS/MSFC-0300175.html.

  3. How faceted liquid droplets grow tails: from surface topology to active motion

    NASA Astrophysics Data System (ADS)

    Sloutskin, Eli

    Among all possible shapes of a volume V, a sphere has the smallest surface area A. Therefore, liquid droplets are spherical, minimizing their interfacial energy γA for a given interfacial tension γ > 0 . This talk will demonstrate that liquid oil (alkane) droplets in water, stabilized by a common surfactant can be temperature-tuned to adopt icosahedral and other faceted shapes, above the bulk melting temperature of the oil. Although emulsions have been studied for centuries no faceted liquid droplets have ever been reported. The formation of an icosahedral shape is attributed to the interplay between γ and the elastic properties of the interfacial monomolecular layer, which crystallizes here 10-15K above bulk melting, leaving the droplet's bulk liquid. The icosahedral symmetry is dictated by twelve five-fold topological defects, forming within the hexagonally-packed interfacial crystalline monolayer. Moreover, we demonstrate that upon further cooling this `interfacial freezing' effect makes γ transiently switch its sign, leading to a spontaneous splitting of droplets and an active growth of their surface area, reminiscent of the classical spontaneous emulsification, yet driven by completely different physics. The observed phenomena allow deeper insights to be gained into the fundamentals of molecular elasticity and open new vitas for a wide range of novel nanotechnological applications, from self-assembly of complex shapes to new delivery strategies in bio-medicine. Acknowledgment is made to the Donors of the American Chemical Society Petroleum Research Fund for support of this research and to the Kahn Foundation for the purchase of equipment.

  4. Wetted foam liquid fuel ICF target experiments

    DOE PAGES

    Olson, R. E.; Leeper, R. J.; Yi, S. A.; ...

    2016-05-26

    We are developing a new NIF experimental platform that employs wetted foam liquid fuel layer ICF capsules. We will use the liquid fuel layer capsules in a NIF sub-scale experimental campaign to explore the relationship between hot spot convergence ratio (CR) and the predictability of hot spot formation. DT liquid layer ICF capsules allow for flexibility in hot spot CR via the adjustment of the initial cryogenic capsule temperature and, hence, DT vapor density. Our hypothesis is that the predictive capability of hot spot formation is robust and 1D-like for a relatively low CR hot spot (CR~15), but will becomemore » less reliable as hot spot CR is increased to CR>20. Simulations indicate that backing off on hot spot CR is an excellent way to reduce capsule instability growth and to improve robustness to low-mode x-ray flux asymmetries. In the initial experiments, we will test our hypothesis by measuring hot spot size, neutron yield, ion temperature, and burn width to infer hot spot pressure and compare to predictions for implosions with hot spot CR's in the range of 12 to 25. Larger scale experiments are also being designed, and we will advance from sub-scale to full-scale NIF experiments to determine if 1D-like behavior at low CR is retained as the scale-size is increased. The long-term objective is to develop a liquid fuel layer ICF capsule platform with robust thermonuclear burn, modest CR, and significant α-heating with burn propagation.« less

  5. Wetted foam liquid fuel ICF target experiments

    SciTech Connect

    Olson, R. E.; Leeper, R. J.; Yi, S. A.; Kline, J. L.; Zylstra, A. B.; Peterson, R. R.; Shah, R.; Braun, T.; Biener, J.; Kozioziemski, B. J.; Sater, J. D.; Biener, M. M.; Hamza, A. V.; Nikroo, A.; Hopkins, L. Berzak; Ho, D.; LePape, S.; Meezan, N. B.

    2016-05-26

    We are developing a new NIF experimental platform that employs wetted foam liquid fuel layer ICF capsules. We will use the liquid fuel layer capsules in a NIF sub-scale experimental campaign to explore the relationship between hot spot convergence ratio (CR) and the predictability of hot spot formation. DT liquid layer ICF capsules allow for flexibility in hot spot CR via the adjustment of the initial cryogenic capsule temperature and, hence, DT vapor density. Our hypothesis is that the predictive capability of hot spot formation is robust and 1D-like for a relatively low CR hot spot (CR~15), but will become less reliable as hot spot CR is increased to CR>20. Simulations indicate that backing off on hot spot CR is an excellent way to reduce capsule instability growth and to improve robustness to low-mode x-ray flux asymmetries. In the initial experiments, we will test our hypothesis by measuring hot spot size, neutron yield, ion temperature, and burn width to infer hot spot pressure and compare to predictions for implosions with hot spot CR's in the range of 12 to 25. Larger scale experiments are also being designed, and we will advance from sub-scale to full-scale NIF experiments to determine if 1D-like behavior at low CR is retained as the scale-size is increased. The long-term objective is to develop a liquid fuel layer ICF capsule platform with robust thermonuclear burn, modest CR, and significant α-heating with burn propagation.

  6. Wetted foam liquid fuel ICF target experiments

    NASA Astrophysics Data System (ADS)

    Olson, R. E.; Leeper, R. J.; Yi, S. A.; Kline, J. L.; Zylstra, A. B.; Peterson, R. R.; Shah, R.; Braun, T.; Biener, J.; Kozioziemski, B. J.; Sater, J. D.; Biener, M. M.; Hamza, A. V.; Nikroo, A.; Berzak Hopkins, L.; Ho, D.; LePape, S.; Meezan, N. B.

    2016-05-01

    We are developing a new NIF experimental platform that employs wetted foam liquid fuel layer ICF capsules. We will use the liquid fuel layer capsules in a NIF sub-scale experimental campaign to explore the relationship between hot spot convergence ratio (CR) and the predictability of hot spot formation. DT liquid layer ICF capsules allow for flexibility in hot spot CR via the adjustment of the initial cryogenic capsule temperature and, hence, DT vapor density. Our hypothesis is that the predictive capability of hot spot formation is robust and 1D-like for a relatively low CR hot spot (CR∼15), but will become less reliable as hot spot CR is increased to CR>20. Simulations indicate that backing off on hot spot CR is an excellent way to reduce capsule instability growth and to improve robustness to low-mode x-ray flux asymmetries. In the initial experiments, we will test our hypothesis by measuring hot spot size, neutron yield, ion temperature, and burn width to infer hot spot pressure and compare to predictions for implosions with hot spot CR's in the range of 12 to 25. Larger scale experiments are also being designed, and we will advance from sub-scale to full-scale NIF experiments to determine if 1D-like behavior at low CR is retained as the scale-size is increased. The long-term objective is to develop a liquid fuel layer ICF capsule platform with robust thermonuclear burn, modest CR, and significant α-heating with burn propagation.

  7. Deformation and breakup of a liquid droplet past a solid circular cylinder: a lattice Boltzmann study.

    PubMed

    Li, Qiuxiang; Chai, Zhenhua; Shi, Baochang; Liang, Hong

    2014-10-01

    In this paper, we present a numerical study on the deformation and breakup behavior of liquid droplet past a solid circular cylinder by using an improved interparticle-potential lattice Boltzmann method. The effects of the eccentric ratio β, viscosity ratio λ between the droplet and the surrounding fluid, surface wettability, and Bond number (Bo) on the dynamic behavior of the liquid droplet are considered. The parameter β represents the degree that the solid cylinder deviates from the center line, and Bo is the ratio between the inertial force and capillary force. Numerical results show that there are two typical patterns, i.e., breakup and no breakup, which are greatly influenced by the aforementioned parameters. When β increases to a critical value βc, the droplet can pass the circular cylinder without a breakup, otherwise, the breakup phenomenon occurs. The critical eccentric ratio βc increases significantly with increasing Bo for case with λ>1, while for the case with λ<1, the viscosity effects on the βc is not obvious when Bo is large. For the breakup case, the amount of deposited liquid on the tip of the circular cylinder is almost unaffected by β. In addition, the results also show that the viscosity ratio and wettability affect the deformation and breakup process of the droplet. For case with λ<1, the viscosity ratio plays a minor role in the thickness variations of the deposited liquid, which decreases to a nonzero constant eventually; while for λ>1, the increase of the viscosity ratio significantly accelerates the decrease of the deposited liquid, and finally no fluid deposits on the cylinder. In term of the wettability, there occurs continuous gas phase trapped by the wetting droplet, but this does not happen for nonwetting droplet. Besides, for λ<1, the time required to pass the cylinder (tp) decreases monotonically with decreasing contact angle, while a nonmonotonic decrease appears for λ>1. It is also found that tp decreases

  8. 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.

  9. 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.

  10. High-Voltage Droplet Dispenser

    NASA Technical Reports Server (NTRS)

    Eichenberg, Dennis J.

    2003-01-01

    An apparatus that is extremely effective in dispensing a wide range of droplets has been developed. This droplet dispenser is unique in that it utilizes a droplet bias voltage, as well as an ionization pulse, to release a droplet. Apparatuses that deploy individual droplets have been used in many applications, including, notably, study of combustion of liquid fuels. Experiments on isolated droplets are useful in that they enable the study of droplet phenomena under well-controlled and simplified conditions. In this apparatus, a syringe dispenses a known value of liquid, which emerges from, and hangs onto, the outer end of a flat-tipped, stainless steel needle. Somewhat below the needle tip and droplet is a ring electrode. A bias high voltage, followed by a high-voltage pulse, is applied so as to attract the droplet sufficiently to pull it off the needle. The voltages are such that the droplet and needle are negatively charged and the ring electrode is positively charged.

  11. Comparison of alternate fuels for aircraft. [liquid hydrogen, liquid methane, and synthetic aviation kerosene

    NASA Technical Reports Server (NTRS)

    Witcofski, R. D.

    1979-01-01

    Liquid hydrogen, liquid methane, and synthetic aviation kerosene were assessed as alternate fuels for aircraft in terms of cost, capital requirements, and energy resource utilization. Fuel transmission and airport storage and distribution facilities are considered. Environmental emissions and safety aspects of fuel selection are discussed and detailed descriptions of various fuel production and liquefaction processes are given. Technological deficiencies are identified.

  12. Liquid fuel injection elements for rocket engines

    NASA Technical Reports Server (NTRS)

    Cox, George B., Jr. (Inventor)

    1993-01-01

    Thrust chambers for liquid propellant rocket engines include three principal components. One of these components is an injector which contains a plurality of injection elements to meter the flow of propellants at a predetermined rate, and fuel to oxidizer mixture ratio, to introduce the mixture into the combustion chamber, and to cause them to be atomized within the combustion chamber so that even combustion takes place. Evolving from these injectors are tube injectors. These tube injectors have injection elements for injecting the oxidizer into the combustion chamber. The oxidizer and fuel must be metered at predetermined rates and mixture ratios in order to mix them within the combustion chamber so that combustion takes place smoothly and completely. Hence tube injectors are subject to improvement. An injection element for a liquid propellant rocket engine of the bipropellant type is provided which includes tangential fuel metering orifices, and a plurality of oxidizer tube injection elements whose injection tubes are also provided with tangential oxidizer entry slots and internal reed valves.

  13. Liquid fuel injection elements for rocket engines

    NASA Astrophysics Data System (ADS)

    Cox, George B., Jr.

    1993-01-01

    Thrust chambers for liquid propellant rocket engines include three principal components. One of these components is an injector which contains a plurality of injection elements to meter the flow of propellants at a predetermined rate, and fuel to oxidizer mixture ratio, to introduce the mixture into the combustion chamber, and to cause them to be atomized within the combustion chamber so that even combustion takes place. Evolving from these injectors are tube injectors. These tube injectors have injection elements for injecting the oxidizer into the combustion chamber. The oxidizer and fuel must be metered at predetermined rates and mixture ratios in order to mix them within the combustion chamber so that combustion takes place smoothly and completely. Hence tube injectors are subject to improvement. An injection element for a liquid propellant rocket engine of the bipropellant type is provided herein which includes tangential fuel metering orifices, and a plurality of oxidizer tube injection elements whose injection tubes are also provided with tangential oxidizer entry slots and internal reed valves.

  14. Liquid fuel injection elements for rocket engines

    NASA Astrophysics Data System (ADS)

    Cox, George B., Jr.

    1993-11-01

    Thrust chambers for liquid propellant rocket engines include three principal components. One of these components is an injector which contains a plurality of injection elements to meter the flow of propellants at a predetermined rate, and fuel to oxidizer mixture ratio, to introduce the mixture into the combustion chamber, and to cause them to be atomized within the combustion chamber so that even combustion takes place. Evolving from these injectors are tube injectors. These tube injectors have injection elements for injecting the oxidizer into the combustion chamber. The oxidizer and fuel must be metered at predetermined rates and mixture ratios in order to mix them within the combustion chamber so that combustion takes place smoothly and completely. Hence tube injectors are subject to improvement. An injection element for a liquid propellant rocket engine of the bipropellant type is provided which includes tangential fuel metering orifices, and a plurality of oxidizer tube injection elements whose injection tubes are also provided with tangential oxidizer entry slots and internal reed valves.

  15. Temperature-Tuned Faceting and Shape Changes in Liquid Alkane Droplets

    DOE PAGES

    Guttman, Shani; Sapir, Zvi; Ocko, Benjamin M.; ...

    2017-01-09

    Recent extensive studies reveal that surfactant-stabilized spherical alkane emulsion droplets spontaneously adopt polyhedral shapes upon cooling below a temperature Td while remaining liquid. Further cooling induces the growth of tails and spontaneous droplet splitting. Two mechanisms were offered to account for these intriguing effects. One assigns the effects to the formation of an intradroplet frame of tubules consisting of crystalline rotator phases with cylindrically curved lattice planes. The second assigns the sphere-to-polyhedron transition to the buckling of defects in a crystalline interfacial monolayer, known to form in these systems at some Ts > Td. The buckling reduces the extensional energymore » of the crystalline monolayer’s defects, unavoidably formed when wrapping a spherical droplet by a hexagonally packed interfacial monolayer. The tail growth, shape changes, and droplet splitting were assigned to the decrease and vanishing of surface tension, γ. Here we present temperature-dependent γ(T), optical microscopy measurements, and interfacial entropy determinations for several alkane/surfactant combinations. We demonstrate the advantages and accuracy of the in situ γ(T) measurements made simultaneously with the microscopy measurements on the same droplet. The in situ and coinciding ex situ Wilhelmy plate γ(T) measurements confirm the low interfacial tension, ≲0.1 mN/m, observed at Td. Here, our results provide strong quantitative support validating the crystalline monolayer buckling mechanism.« less

  16. Light transmission of polymer-dispersed liquid crystal layer composed of droplets with inhomogeneous surface anchoring

    NASA Astrophysics Data System (ADS)

    Loiko, V. A.; Zyryanov, V. Ya.; Konkolovich, A. V.; Miskevich, A. A.

    2016-01-01

    We have developed a model and realized an algorithm for the calculation of the coefficient of coherent (direct) transmission of light through a layer of liquid crystal (LC) droplets in a polymer matrix. The model is based on the Hulst anomalous diffraction approximation for describing the scattering by an individual particle and the Foldy-Twersky approximation for a coherent field. It allows one to investigate polymer dispersed LC (PDLC) materials with homogeneous and inhomogeneous interphase surface anchoring on the droplet surface. In order to calculate the configuration of the field of the local director in the droplet, the relaxation method of solving the problem of minimization of the free energy volume density has been used. We have verified the model by comparison with experiment under the inverse regime of the ionic modification of the LC-polymer interphase boundary. The model makes it possible to solve problems of optimization of the optical response of PDLC films in relation to their thickness and optical characteristics of the polymer matrix, sizes, polydispersity, concentration, and anisometry parameters of droplets. Based on this model, we have proposed a technique for estimating the size of LC droplets from the data on the dependence of the transmission coefficient on the applied voltage.

  17. Microfluidic chip-based liquid-liquid extraction and preconcentration using a subnanoliter-droplet trapping technique.

    PubMed

    Chen, Hong; Fang, Qun; Yin, Xue-Feng; Fang, Zhao-Lun

    2005-07-01

    A robust and simple approach for microfluidic liquid-liquid (L-L) extraction at the subnanoliter-scale was developed for on-chip sample pretreatment. Organic solvent droplets of a few hundred pL were trapped within micro recesses fabricated in the channel walls of a microfabricated glass chip. L-L extraction was performed by delivering aqueous samples through the channel, with the sample stream continuously flowing adjacent to the droplets. The analytes in aqueous streams were enriched within the droplet with high preconcentration factors owing to both phase transfer and dissolution of organic solvent into the bypassing aqueous sample. An aqueous solution of butyl rhodamine B (BRB) and 1-hexanol were used, respectively, as sample and extractant to demonstrate the performance of the system. The fluorescence intensity of the dye extracted into the droplet was monitored in situ by LIF. The system proved to be an efficient means for achieving high enrichment factors of over 1000, with sample consumption of a few microL. Quantitative measurement of the extracted analyte was achieved with a linear response in the range 1 x 10(-9)-8 x 10(-7) M BRB. The precision of the measured fluorescence values for a 10(-7) M BRB standard with a 12.5 min preconcentration period was 6.6% RSD (n = 5).

  18. Supercritical microgravity droplet vaporization

    NASA Technical Reports Server (NTRS)

    Hartfield, J.; Curtis, E.; Farrell, P.

    1990-01-01

    Supercritical droplet vaporization is an important issue in many combustion systems, such as liquid fueled rockets and compression-ignition (diesel) engines. In order to study the details of droplet behavior at these conditions, an experiment was designed to provide a gas phase environment which is above the critical pressure and critical temperature of a single liquid droplet. In general, the droplet begins as a cold droplet in the hot, high pressure environment. In order to eliminate disruptions to the droplet by convective motion in the gas, forced and natural convection gas motion are required to be small. Implementation of this requirement for forced convection is straightforward, while reduction of natural convection is achieved by reduction in the g-level for the experiment. The resulting experiment consists of a rig which can stably position a droplet without restraint in a high-pressure, high temperature gas field in microgravity. The microgravity field is currently achieved by dropping the device in the NASA Lewis 2.2 second drop tower. The performance of the experimental device and results to date are presented.

  19. Shapes of a liquid droplet in a periodic box

    NASA Astrophysics Data System (ADS)

    Prestipino, Santi; Caccamo, Carlo; Costa, Dino; Malescio, Gianpietro; Munaò, Gianmarco

    2015-08-01

    Within the coexistence region between liquid and vapor the equilibrium pressure of a simulated fluid exhibits characteristic jumps and plateaus when plotted as a function of density at constant temperature. These features exclusively pertain to a finite-size sample in a periodic box, as they are washed out in the bulk limit. Below the critical density, at each pressure jump the shape of the liquid drop undergoes a morphological transition, changing from spherical to cylindrical to slablike as the density is increased. We formulate a simple theory of these shape transitions, which is adapted from a calculation originally developed by Binder and coworkers [L. G. MacDowell, P. Virnau, M. Muller, and K. Binder, J. Chem. Phys. 120, 5293 (2004), 10.1063/1.1645784]. Our focus is on the pressure equation of state (rather than on the chemical potential, as in the original work) and includes an extension to elongated boxes. Predictions based on this theory well agree with extensive Monte Carlo data for the cut-and-shifted Lennard-Jones fluid. We further discuss the thermodynamic stability of liquid drops with shapes other than the three mentioned above, like those found deep inside the liquid-vapor region in simulations starting from scratch. Our theory classifies these more elaborate shapes as metastable.

  20. Lu and Duque play with a droplet of liquid

    NASA Image and Video Library

    2003-10-25

    ISS007-E-18001 (25 October 2003) --- Astronaut Edward T. Lu (with camera), Expedition 7 NASA ISS science officer and flight engineer, and European Space Agency (ESA) astronaut Pedro Duque of Spain observe a bubble of liquid floating freely in the Zvezda Service Module on the International Space Station (ISS).

  1. Controlling micro-sized droplet generation using electrical pulses for studying liquid-liquid systems

    NASA Astrophysics Data System (ADS)

    Fernandino, M.; La Forgia, N.; Vera, A. J.; Bjerknes, J.; Dorao, C. A.

    2014-04-01

    Water droplets removal from oil is a critical process in several industries, in particular in the oil and gas industry. Water/oil separation is commonly done in large gravitational sedimentation tanks, which are over dimensioned due to the lack of accurate models to allow for optimization. This can become challenging for off-shore and subsea processing installations. One of the bottlenecks to study droplet dynamics in the micron range, is the generation of droplets with less than 100μm in diameter. In this regard, one of the most promising techniques for controlling the generated droplet size is based on the use of a high voltage electrical signal or electro-hydrodynamic technique (EHD). Although much work on EHD and droplet generation can been found in the literature, many challenges still remain. One of this is the generation of droplets smaller than 100μm in diameter in a controllable, on-demand manner. In this work, the effect of the meniscus shape and the electric pulse characteristics on the size of the generated droplet is investigated. Both the meniscus height and width help to determine the droplet size, with the latter having a stronger effect. No significant influence of the pulse amplitude and pulse width was observed for the tested conditions.

  2. Using liquid droplet penetration experiments to determine wetting properties of powders

    NASA Astrophysics Data System (ADS)

    Callegari, Gerardo; Liu, Zhanjie; Wang, Yifan; Muzzio, Fernando; Drazer, German

    2016-11-01

    We show that the spontaneous penetration of droplets on a powder bed provides a simple way to characterize the wetting properties of a test liquid. Specifically, we demonstrate that calculating the appropriate dimensionless penetrating volume and time, and performing supplementary experiments with a reference liquid, it is possible to obtain the contact angle between the test liquid and the powder. Interestingly, the proposed analysis lets us calculate the contact angle without having to compute the solution to the 3D penetration problem. This approach is valid when the contact area between the droplet and the powder bed remains constant, which is a good approximation in many powder systems. We first test the validity of our approach by studying droplets of different sizes and show that the non-dimensional penetration curves are independent of the initial volume and contact radius of the drops, as predicted. We then use a reference liquid (silicone oil) to measure the contact angle of water on three powder systems with increasing number of pharmaceutical components and different processing conditions known to affect blend wettability. We show that the proposed method is able to capture the overlubrication of the blend, a well-known effect in pharmaceutical manufacturing.

  3. Shape evolution of a single liquid-crystal droplet immersed in an isotropic matrix under transient and steady flow.

    PubMed

    Wu, Youjun; Yu, Wei; Zhou, Chixing; Xu, Yuanze

    2007-04-01

    The morphology evolution of immiscible polymer-liquid crystal systems is quite different from flexible polymer-polymer mixtures due to the anisotropic properties of liquid crystals. The deformation and retraction of a single low molar mass liquid crystal 4'-pentyl-4-biphenylcarbonitrile (5CB) droplet and 4'-octyl-4-biphenylcarbonitrile (8CB) dispersed in polydimethyl-siloxane under two-dimensional linear flow was investigated by a computer-controlled four-roll mill, which is equipped with an optical microscope and a digital camera. The deformation parameter and orientation angle during deformation versus capillary number was obtained and compared with calculations using the Maffettone-Minale (MM) model and the Yu-Zhou liquid-crystal (YZ-LC) model. The MM model can describe the behavior of a Newtonian droplet in another Newtonian matrix whereas the YZ-LC model can describe the behavior of a LC droplet in a Newtonian matrix. The results showed that the deformation and rotation of a LC droplet is more difficult than viscoelastic droplets, possibly because of the resistance of the nematic elastic energy induced by the nematic mesogens deformation and orientation under flow field. Furthermore, the different behavior between flow-aligning 5CB and flow-tumbling 8CB droplets and the influence of droplet size of LC on deformation and retraction were discussed by experiment and calculation; the results reveal that the different size LC droplets show different evolution curves.

  4. An Oil-Stream Photomicrographic Aeroscope for Obtaining Cloud Liquid-Water Content and Droplet Size Distributions in Flight

    NASA Technical Reports Server (NTRS)

    Hacker, Paul T.

    1956-01-01

    An airborne cloud aeroscope by which droplet size, size distribution, and liquid-water content of clouds can be determined has been developed and tested in flight and in wind tunnels with water sprays. In this aeroscope the cloud droplets are continuously captured in a stream of oil, which Is then photographed by a photomicrographic camera. The droplet size and size distribution can be determined directly from the photographs. With the droplet size distribution known, the liquid-water content of the cloud can be computed from the geometry of the aeroscope, the airspeed, and the oil-flow rate. The aeroscope has the following features: Data are obtained semi-automatically, and permanent data are taken in the form of photographs. A single picture usually contains a sufficient number of droplets to establish the droplet size distribution. Cloud droplets are continuously captured in the stream of oil, but pictures are taken at Intervals. The aeroscope can be operated in icing and non-icing conditions. Because of mixing of oil in the instrument, the droplet-distribution patterns and liquid-water content values from a single picture are exponentially weighted average values over a path length of about 3/4 mile at 150 miles per hour. The liquid-water contents, volume-median diameters, and distribution patterns obtained on test flights and in the Lewis icing tunnel are similar to previously published data.

  5. Coupled modeling of water transport and air-droplet interaction in the electrode of a proton exchange membrane fuel cell

    NASA Astrophysics Data System (ADS)

    Esposito, Angelo; Pianese, Cesare; Guezennec, Yann G.

    In this work, an accurate and computationally fast model for liquid water transport within a proton exchange membrane fuel cell (PEMFC) electrode is developed by lumping the space-dependence of the relevant variables. Capillarity is considered as the main transport mechanism within the gas diffusion layer (GDL). The novelty of the model lies in the coupled simulation of the water transport at the interface between gas diffusion layer and gas flow channel (GFC). This is achieved with a phenomenological description of the process that allows its simulation with relative simplicity. Moreover, a detailed two-dimensional visualization of such interface is achieved via geometric simulation of water droplets formation, growth, coalescence and detachment on the surface of the GDL. The model is useful for optimization analysis oriented to both PEMFC design and balance of plant. Furthermore, the accomplishment of reduced computational time and good accuracy makes the model suitable for control strategy implementation to ensure PEM fuel cells operation within optimal electrode water content.

  6. Simulation and experimental validation of droplet dynamics in microchannels of PEM fuel cells

    NASA Astrophysics Data System (ADS)

    Ashrafi, Moosa; Shams, Mehrzad; Bozorgnezhad, Ali; Ahmadi, Goodarz

    2016-12-01

    In this study, dynamics of droplets in the channels of proton exchange membrane fuel cells with straight and serpentine flow-fields was investigated. Tapered and filleted channels were suggested for the straight and serpentine flow-fields respectively in order to improve water removal in channels. Surface tension and wall adhesion forces were applied by using the volume of fluid method. The hydrophilic walls and hydrophobic gas diffusion layer were considered. The mechanism of droplets movement with different diameters was studied by using the Weber and capillary numbers in simple and tapered straight channels. It was illustrated that the flooding was reduced in tapered channel due to increase of water removal rate, and available reaction sites improved subsequently. In addition, film flow was formed in the tapered channel more than the simple channel, so pressure fluctuation was decreased in the tapered channel. Moreover, the water coverage ratio of hydrophilic tapered surface was more than the simple channel, which enhanced water removal from the channel. The filleted serpentine channel was introduced to improve water removal from the simple serpentine channel. It was shown by observation of the unsteady and time-averaged two-phase pressure drop that in the filleted serpentine channels, the two-phase pressure drop was far less than the simple serpentine channel, and also the accumulation of water droplets in the elbows was less leading to lower pressure fluctuation. The numerical simulation results were validated by experiments.

  7. Determination of droplet contours in liquid-liquid flows within microchannels

    NASA Astrophysics Data System (ADS)

    Pulvirenti, B.; Rostami, B.; Puccetti, G.; Morini, G. L.

    2015-11-01

    An experimental analysis of the droplet regime with a silicone oil-water two-phase flow within a micro cross-junction, varying the average velocity of the fluids, has been carried out. The micro cross-junction is made as intersection of two glass microchannels with a stadium-shaped cross-section with height H=190 μm and width Wj=195 μm within the junction and W=390 μm before and after the junction. The water flow rate is broken in droplets having spherical shape with dimensions and velocity that depend on the average velocity ratio imposed. Different kinds of intermittent droplets have been observed, in the ranges of average velocity (0.0105-0.042) m/s and (0.0004-0.0050) m/s for oil and water, respectively. The droplet velocity has been calculated starting from the detection of the shape of the droplets and then by the evaluation of the displacement of the droplets in the unit of time. The images of the droplets have been obtained from a high-speed camera, connected to an inverted microscope. The procedure of water phase contour detection is based on Matlab Image Toolbox scripts.

  8. Final optics protection in laser inertial fusion with cryogenic liquid droplets

    SciTech Connect

    Moir, R W

    2000-08-31

    A burst of x rays and vaporized debris from high yield targets can damage the final optics in laser inertial fusion energy (IFE) power plants and in laboratory experimental facilities such as the National Ignition Facility (NIF) or Laser MegaJoule (LMJ). Noble gases such as Xe or Kr have been proposed to protect final optics from target-produced x rays and debris. Some problems with the use of such ambient gas fills are the large amount of gas involved, heat transfer to a cryogenic target, potential resonant reradiation of x rays absorbed, and a nonuniform index of refraction due to turbulence interfering with the focusing of laser light. Also the fast igniter laser intensity may be too great for propagation through an ambient gas. We propose to provide the gas in the form of many small closely spaced liquid droplets injected in front of the optics. In the case of NIF, the droplets would be injected only when needed just before a high yield shot. The laser light that is absorbed will cause evaporation of the liquid and spreading of this gas. The liquid droplets intercept only {approx}5% of the laser light allowing {approx}95% to pass through to the target. The light absorbed in the NIF example (assumed to be 50% of the intercepted light, whose intensity is 3.6 x 10{sup 9} W/cm{sup 2}) would cause the xenon droplets to evaporate and spread uniformly such that the x rays from 10 eV to 2 keV are appreciably attenuated when they arrive 40 to 70 ns later at the optical surface. X rays above 3 keV and below 10 eV are not attenuated very much but their intensities are rapidly falling off in this range anyway. Typical droplet sizes are {approx}10 {micro}m radius with a spacing of {approx}0.4 mm. The gas would also protect vaporized target debris from condensing on the optics due to the 0.2 mg/cm{sup 2} of xenon (5 x 10{sup 17} cm{sup -2} or 8 Torr-cm for l-e-folding of 1 keV x-rays). These droplets might be produced with technology similar to ink jet technology and photo

  9. Plasma charging and electron-based reactions at the plasma-liquid interface of an isolated liquid droplet

    NASA Astrophysics Data System (ADS)

    Maguire, Paul; Mahony, Charles; Kelsey, Colin; Rutherford, David; Mariotti, Davide; Diver, Declan

    2016-09-01

    The study of plasma-liquid interactions opens up exciting new opportunities for applications but numerous investigative challenges remain. The use of isolated and stable spherical liquid microdroplets in a non-thermal equilibrium atmospheric pressure plasma offers a new platform for experimental and theoretical investigations. Since the droplet assumes floating potential, a high flux of electrons with low net energy ( thermal) becomes fixed and solvated within the first monolayers of the liquid leading to highly reactive and rapid chemical reactions. We observe such reactions, e.g. H2 O2 and metal nanoparticle formation, at rates that are much higher than reported elsewhere. Since the isolated droplet radius is greater than Debye lengths and mean free paths, we have an opportunity to directly compare, for the first time, long-standing collisional probe theories in this important regime. We measure a lower bound average charge of >1E5 electrons on a 13um droplet. Simulations of unipolar corona charging for this size predict 1E3 electrons. A Comsol-based drift-diffusion model is currently under development and so far experiment and theory match within 1 order of magnitude but improvements in measurement technique are in progress. Funding from EPSRC acknowledged (Grants EP/K006088/1 and EP/K006142/1).

  10. Droplet Size Distribution and Liquid Volume Concentration in a Water Spray: Predictions and Measurements

    DTIC Science & Technology

    1984-01-01

    liquid volume copcentration at different distances from the injector have been measured. The predictions showed good agreement with experimental results...11,2,3,4,5,91, however their validation with experimental data has not often been attempted, mainly due to the difficulty _ in getting experimental results...The droplet velocity at the beginning is not measured, but the atomizer used in the experiments was a twin- -fluid atomizer, described in 18T, and

  11. Two-frequency forcing of droplet rebounds on a liquid bath

    NASA Astrophysics Data System (ADS)

    Sampara, Naresh; Gilet, Tristan

    2016-11-01

    Droplets can bounce indefinitely on a liquid bath vertically vibrated in a sinusoidal fashion. We here present experimental results that extend this observation to forcing signals composed of a combination of two commensurable frequencies. The Faraday and Goodridge thresholds are characterized. Then a number of vertical bouncing modes are reported, including walkers. The vertical motion can become chaotic, in which case the horizontal motion is an alternation of walk and stop.

  12. Mass Transfer in the Dissolution of a Multi-Component Liquid Droplet in an Immiscible Liquid Environment

    PubMed Central

    Su, Jonathan T.; Needham, David

    2013-01-01

    The Epstein Plesset equation has recently been shown to accurately predict the dissolution of a pure liquid microdroplet into a second immiscible solvent, such as oil into water. Here, we present a series of new experiments and a modification to this equation to model the dissolution of a two-component oil-mixture microdroplet into a second immiscible solvent, in which the two materials of the droplet have different solubilities. The model is based upon a reduced surface area approximation and the assumption of ideal homogenous mixing: Massfluxdmidt=AfraciDi(ci-cs){1R+1πDit}, where Afraci is the area fraction of component I; ci and cs are the initial and saturation concentrations of the droplet material in the surrounding medium; R is the radius of the droplet; t is time; and Di is the coefficient of diffusion of component I in the surrounding medium. This new model has been tested by use of a two-chamber micropipette-based method, which measured the dissolution of single individual microdroplets of mutually-miscible liquid mixtures (ethyl acetate/butyl acetate, and butyl acetate/amyl acetate) into water. We additionally measured the diffusion coefficient of the pure materials: ethyl acetate, butyl acetate, and amyl acetate, in water at 22 deg C. Diffusion coefficients for the pure acetates in water were: 8.65 x 10−6, 7.61 x 10−6, and 9.14 x 10−6 cm2/s respectively. This model accurately predicts the dissolution of microdroplets for the ethyl acetate/butyl acetate and butyl acetate/amyl acetate systems given the solubility and diffusion coefficients of each of the individual components in water as well as the initial droplet radius. The average mean squared error was 8.96%. The dissolution of a spherical ideally mixed multi-component droplet closely follows the modified Epstein Plesset model presented here. PMID:24050124

  13. Distillation of liquid fuels by thermogravimetry

    SciTech Connect

    Huang, He; Wang, Keyu; Wang, Shaojie; Klein, M.T.; Calkins, W.H.

    1996-12-31

    In this paper, design and operation of a custom-built thermogravimetric apparatus for the distillation of liquid fuels are reported. Using a sensitive balance with scale of 0.001 g and ASTM distillation glassware, several petroleum and petroleum-derived samples have been analyzed by the thermogravimetric distillation method. When the ASTM distillation glassware is replaced by a micro-scale unit, sample size could be reduced from 100 g to 5-10 g. A computer program has been developed to transfer the data into a distillation plot, e.g. Weight Percent Distilled vs. Boiling Point. It also generates a report on the characteristic distillation parameters, such as, IBP (Initial Boiling Point), FBP (Final Boiling Point), and boiling point at 50 wt% distilled. Comparison of the boiling point distributions determined by TG (thermogravimetry) with those by SimDis GC (Simulated-Distillation Gas Chromatography) on two liquid fuel samples (i.e. a decanted oil and a filtered crude oil) are also discussed in this paper.

  14. Taylor cone and jetting from liquid droplets in electrospinning of nanofibers

    NASA Astrophysics Data System (ADS)

    Yarin, A. L.; Koombhongse, S.; Reneker, D. H.

    2001-11-01

    Sessile and pendant droplets of polymer solutions acquire stable shapes when they are electrically charged by applying an electrical potential difference between the droplet and a flat plate, if the potential is not too large. These stable shapes result only from equilibrium of the electric forces and surface tension in the cases of inviscid, Newtonian, and viscoelastic liquids. In liquids with a nonrelaxing elastic force, that force also affects the shapes. It is widely assumed that when the critical potential φ0* has been reached and any further increase will destroy the equilibrium, the liquid body acquires a conical shape referred to as the Taylor cone, having a half angle of 49.3°. In the present work we show that the Taylor cone corresponds essentially to a specific self-similar solution, whereas there exist nonself-similar solutions which do not tend toward a Taylor cone. Thus, the Taylor cone does not represent a unique critical shape: there exists another shape, which is not self-similar. The experiments of the present work demonstrate that the observed half angles are much closer to the new shape. In this article a theory of stable shapes of droplets affected by an electric field is proposed and compared with data acquired in our experimental work on electrospinning of nanofibers from polymer solutions and melts.

  15. Organized Assemblies of Colloids Formed at the Poles of Micrometer-Sized Droplets of Liquid Crystal

    PubMed Central

    Wang, Xiaoguang; Miller, Daniel S.; de Pablo, Juan J.

    2014-01-01

    We report on the formation of organized assemblies of 1 μm-in-diameter colloids (polystyrene (PS)) at the poles of water-dispersed droplets (diameters 7 - 20 μm) of nematic liquid crystal (LC). For 4-cyano-4′-pentylbiphenyl droplets decorated with two to five PS colloids, we found 32 distinct arrangements of the colloids to form at the boojums of bipolar droplet configurations. Significantly, all but one of these configurations (a ring comprised of five PS colloids) could be mapped onto a local (non-close packed) hexagonal lattice. To provide insight into the origin of the hexagonal lattice, we investigated planar aqueous—LC interfaces, and found that organized assemblies of PS colloids did not form at these interfaces. Experiments involving the addition of salts revealed that a repulsive interaction of electrostatic origin prevented formation of assemblies at planar interfaces, and that regions of high splay near the poles of the LC droplets generated cohesive interactions between colloids that could overcome the repulsion. Support for this interpretation was obtained from a model that included (i) a long-range attraction between adsorbed colloids and the boojum due to the increasing rate of strain (splay) of LC near the boojum (splay attraction), (ii) an attractive inter-colloid interaction that reflects the quadrupolar symmetry of the strain in the LC around the colloids, and (iii) electrostatic repulsion between colloids. The model predicts that electrostatic repulsion between colloids can lead to a ∼1,000 kBT energy barrier at planar interfaces of LC films, and that the repulsive interaction can be overcome by splay attraction of the colloids to the boojums of the LC droplets. Overall, the results reported in this paper advance our understanding of the directed assembly of colloids at interfaces of LC droplets. PMID:25284139

  16. Organized assemblies of colloids formed at the poles of micrometer-sized droplets of liquid crystal.

    PubMed

    Wang, Xiaoguang; Miller, Daniel S; de Pablo, Juan J; Abbott, Nicholas L

    2014-11-28

    We report on the formation of organized assemblies of 1 μm-in-diameter colloids (polystyrene (PS)) at the poles of water-dispersed droplets (diameters 7-20 μm) of nematic liquid crystal (LC). For 4-cyano-4'-pentylbiphenyl droplets decorated with two to five PS colloids, we found 32 distinct arrangements of the colloids to form at the boojums of bipolar droplet configurations. Significantly, all but one of these configurations (a ring comprised of five PS colloids) could be mapped onto a local (non-close packed) hexagonal lattice. To provide insight into the origin of the hexagonal lattice, we investigated planar aqueous-LC interfaces, and found that organized assemblies of PS colloids did not form at these interfaces. Experiments involving the addition of salts revealed that a repulsive interaction of electrostatic origin prevented formation of assemblies at planar interfaces, and that regions of high splay near the poles of the LC droplets generated cohesive interactions between colloids that could overcome the repulsion. Support for this interpretation was obtained from a model that included (i) a long-range attraction between adsorbed colloids and the boojum due to the increasing rate of strain (splay) of LC near the boojum (splay attraction), (ii) an attractive inter-colloid interaction that reflects the quadrupolar symmetry of the strain in the LC around the colloids, and (iii) electrostatic repulsion between colloids. The model predicts that electrostatic repulsion between colloids can lead to a ∼1000kBT energy barrier at planar interfaces of LC films, and that the repulsive interaction can be overcome by splay attraction of the colloids to the boojums of the LC droplets. Overall, the results reported in this paper advance our understanding of the directed assembly of colloids at interfaces of LC droplets.

  17. Hydrosol droplet casting process for production of nuclear fuel and breeder material granules

    SciTech Connect

    Langen, H.; Ringel, H.; Zimmer, E.

    1980-03-18

    A hydrosol containing, in nitrate form, a fuel or fuel-andbreeder material which is projected horizontally in the form of droplets into a gas phase containing gaseous ammonia and allowed to fall in a drip-casting column into a precipitation bath containing ammonium hydroxide. In the gas phase, the droplets are hardened just enough to prevent their deformation upon penetrating into the precipitation bath where the hardening is completed. A falling height of 5 cm is suitable. The granules are washed free of ammonium nitrate, then dried, and then sintered. The heavy metal content in the hydrosol is between 1.5 and 3 moles per liter, and the pH value of the precipitation bath is between 8 and 9. The hydrosol contains the heavy metal in oxide form and the process can be used with a thorium oxide hydrosol or a hydrosol that, in addition to thorium oxide, contains the oxide of hexavalent uranium, in the latter case the hexavalent uranium being present in a proportion up to 25% by weight of the total heavy metal. The process is also applicable to producing kernels of mixed thorium and plutonium oxides. In the case of uraniumcontaining granules, the sintering step is carried out in a reducing atmosphere to convert the uranium to the tetravalent state.

  18. Heterogeneous uptake of 8-2 fluorotelomer alcohol on liquid water and 1-octanol droplets.

    PubMed

    Li, Yongquan; Demerjian, Kenneth L; Williams, Leah R; Worsnop, Douglas R; Kolb, Charles E; Davidovits, Paul

    2006-06-01

    The heterogeneous uptake of the 8-2 fluorotelomer alcohol, F(CF2)8CH2CH2OH, on liquid water surfaces over the temperature range 256-273 K and on 1-octanol surfaces over the temperature range 264-295 K has been investigated with a droplet train flow reactor. The uptake coefficient on water droplets is zero within the error of the measurement (+/-0.01) and is independent of droplet temperature. In contrast, significant uptake onto 1-octanol is observed. Measured uptake coefficients for 1-octanol showed a negative temperature dependence, varying from 0.034 +/- 0.005 (1sigma) at 295 K to 0.103 +/- 0.009 at 264 K. The measured uptake coefficients on 1-octanol were independent of gas-liquid contact time, for typical contact times varying between 3 and 15 ms, and independent of the 8-2 fluorotelomer alcohol gas-phase concentration, indicating that the uptake coefficients are equivalent to mass accommodation coefficients. The uptake coefficients on 1-octanol were also independent of relative humidity. These results show that the uptake of FTOHs on or into the aqueous component of cloud/fog droplets or aqueous aerosol particles is not likely to be an important atmospheric sink for these compounds. In these experiments, 1-octanol was used as a model compound for organic-containing atmospheric particles. The larger uptake coefficient measured for 1-octanol surfaces indicates that FTOH partitioning to organic-containing cloud/fog droplets and aerosol particles may be an atmospheric loss mechanism.

  19. Three-dimensional analysis of thermo-mechanically rotating cholesteric liquid crystal droplets under a temperature gradient

    NASA Astrophysics Data System (ADS)

    Yamamoto, T.; Kuroda, M.; Sano, M.

    2015-02-01

    We studied the rotational motion of cholesteric liquid crystal droplets under a temperature gradient (the Lehmann effect). We found that different surface treatments, planar and homeotropic anchoring, provided three types of droplets with different textures and geometries. The rotational velocity of these droplets depends differently on their size. Determining the three-dimensional structures of these droplets by the fluorescence confocal polarizing microscopy, we propose a phenomenological equation to explain the rotational behavior of these droplets. This result shows that the description by the Ericksen-Leslie theory should be valid in the bulk of the droplet, but we need to take into account the surface torque induced by temperature gradient to fully understand the Lehmann effect.

  20. Self-Assembly of Silver Nanowire Ring Structures Driven by the Compressive Force of a Liquid Droplet.

    PubMed

    Seong, Baekhoon; Park, Hyun Sung; Chae, Ilkyeong; Lee, Hyungdong; Wang, Xiaofeng; Jang, Hyung-Seok; Jung, Jaehyuck; Lee, Changgu; Lin, Liwei; Byun, Doyoung

    2017-04-11

    In a nanowire dispersed in liquid droplets, the interplay between the surface tension of the liquid and the elasticity of the nanowire determines the final morphology of the bent or buckled nanowire. Here, we investigate the fabrication of a silver nanowire ring generated as the nanowire encapsulated inside of fine droplets. We used a hybrid aerodynamic and electrostatic atomization method to ensure the generation of droplets with scalable size in the necessary regime for ring formation. We analytically calculate the compressive force of the droplet driven by surface tension as the key mechanism for the self-assembly of ring structures. Thus, for potential large-scale manufacturing, the droplet size provides a convenient parameter to control the realization of ring structures from nanowires.

  1. Liquid-Grain Mixing Suppresses Droplet Spreading and Splashing during Impact

    NASA Astrophysics Data System (ADS)

    Zhao, Song-Chuan; de Jong, Rianne; van der Meer, Devaraj

    2017-02-01

    Would a raindrop impacting on a coarse beach behave differently from that impacting on a desert of fine sand? We study this question by a series of model experiments, where the packing density of the granular target, the wettability of individual grains, the grain size, the impacting liquid, and the impact speed are varied. We find that by increasing the grain size and/or the wettability of individual grains the maximum droplet spreading undergoes a transition from a capillary regime towards a viscous regime, and splashing is suppressed. The liquid-grain mixing is discovered to be the underlying mechanism. An effective viscosity is defined accordingly to quantitatively explain the observations.

  2. Packaging a liquid metal ESD with micro-scale Mercury droplet.

    SciTech Connect

    Barnard, Casey Anderson

    2011-08-01

    A liquid metal ESD is being developed to provide electrical switching at different acceleration levels. The metal will act as both proof mass and electric contact. Mercury is chosen to comply with operation parameters. There are many challenges surrounding the deposition and containment of micro scale mercury droplets. Novel methods of micro liquid transfer are developed to deliver controllable amounts of mercury to the appropriate channels in volumes under 1 uL. Issues of hermetic sealing and avoidance of mercury contamination are also addressed.

  3. Organosiloxane working fluids for the liquid droplet radiator

    NASA Technical Reports Server (NTRS)

    Buch, R. R.; Huntress, A. R.

    1985-01-01

    Siloxane-based working fluids for advanced space radiators requiring direct fluid exposure to the space environment are evaluated. Isolation of five candidate fluids by vacuum distillation from existing siloxane polymers is discussed. The five fluids recovered include a polydimethylsiloxane, three phenyl-containing siloxanes, and a methylhexylsiloxane. Vapor pressures and viscosities for the five fluids are reported over the temperature range of 250 to 400 K. Use of thermal-gravimetric analysis to reliably estimate vapor pressures of 10 to the -8 power Pascals is described. Polydimethylsiloxane (PDMS) and polymethylphenylsiloxane (PMPS) are selected from the five candidate fluids based on favorable vapor pressure and viscosity, as well as perceived stability in low-Earth orbit environments. Characterization of these fluids by infrared spectroscopy, Si-29 NMR, gel-permeation chromatography, and liquid chromatography is presented. Both fluids consist of narrow molecular weight distributions, with average molecular weights of about 2500 for PDMS and 1300 for PMPS.

  4. IR spectra of water droplets in no man's land and the location of the liquid-liquid critical point

    NASA Astrophysics Data System (ADS)

    Ni, Yicun; Skinner, J. L.

    2016-09-01

    No man's land is the region in the metastable phase diagram of water where it is very difficult to do experiments on liquid water because of homogeneous nucleation to the crystal. There are a number of estimates of the location in no man's land of the liquid-liquid critical point, if it exists. We suggest that published IR absorption experiments on water droplets in no man's land can provide information about the correct location. To this end, we calculate theoretical IR spectra for liquid water over a wide range of temperatures and pressures, using our E3B3 model, and use the results to argue that the temperature dependence of the experimental spectra is inconsistent with several of the estimated critical point locations, but consistent with others.

  5. IR spectra of water droplets in no man's land and the location of the liquid-liquid critical point.

    PubMed

    Ni, Yicun; Skinner, J L

    2016-09-28

    No man's land is the region in the metastable phase diagram of water where it is very difficult to do experiments on liquid water because of homogeneous nucleation to the crystal. There are a number of estimates of the location in no man's land of the liquid-liquid critical point, if it exists. We suggest that published IR absorption experiments on water droplets in no man's land can provide information about the correct location. To this end, we calculate theoretical IR spectra for liquid water over a wide range of temperatures and pressures, using our E3B3 model, and use the results to argue that the temperature dependence of the experimental spectra is inconsistent with several of the estimated critical point locations, but consistent with others.

  6. Droplet Combustion and Soot Formation in Microgravity

    NASA Technical Reports Server (NTRS)

    Avedisian, C. Thomas

    1994-01-01

    One of the most complex processes involved in the combustion ot liquid fuels is the formation of soot. A well characterized flow field and simplified flame structure can improve considerably the understanding of soot formation processes. The simplest flame shape to analyze for a droplet is spherical with its associated one-dimensional flow field. It is a fundamental limit and the oldest and most often analyzed configuration of droplet combustion. Spherical symmetry in the droplet burning process will arise when there is no relative motion between the droplet and ambience or uneven heating around the droplet periphery, and buoyancy effects are negligible. The flame and droplet are then concentric with each other and there is no liquid circulation within the droplet. An understanding of the effect of soot on droplet combustion should therefore benefit from this simplified configuration. Soot formed during spherically symmetric droplet combustion, however, has only recently drawn attention and it appears to be one of the few aspects associated with droplet combustion which have not yet been thoroughly investigated. For this review, the broad subject of droplet combustion is narrowed considerably by restricting attention specifically to soot combined with spherically symmetric droplet burning processes that are promoted.

  7. High temperature fast response pressure probe for use in liquid metal droplet dispensers

    NASA Astrophysics Data System (ADS)

    Rollinger, B.; Mansour, M.; Abhari, R. S.

    2012-06-01

    A miniature fast response high temperature pressure probe, with demonstrated use in liquid metals up to 255 °C (528 K), has been developed. Innovative packaging technologies have been applied to integrate a conventional piezoresistive silicon pressure sensor into the probe, without the need of an auxiliary water-cooling system. In situ static calibrations are used to verify the linearity of the pressure signal and the stability of the pressure sensitivity (0.5% standard deviation over 70 min at 255 °C). Dynamic calibration, completed in an air shock tube facility, yields the probe's natural frequency. This frequency, when corrected for probe operation in liquid tin, is found to be 100 kHz. The reliability and accuracy of the probe is assessed by mounting it in a tin droplet dispenser for use in an extreme ultraviolet light source. Droplet dispensers typically include an excitation mechanism, which can be based on the generation of acoustic pressure waves to impose a desired droplet frequency. The probe accuracy is verified by the comparison of pressure measurements with laser Doppler vibrometry measurements of the pressure generating structure. A reference pressure measurement, conducted at representative conditions, shows a complex frequency response, with peaks distributed over three orders of magnitude and maximum amplitude of 440 mbar. Time variance of the excitation mechanism due to thermal transients is studied by monitoring the pressure response during operation. Finally, the linearity of the excitation system, with respect to the excitation amplitude, is verified by response measurements. In conclusion, the developed probe is capable of characterizing the excitation mechanism of a liquid metal droplet dispenser. Additionally, real-time monitoring of the performance of the excitation system during long-term operation is possible.

  8. Analysis of stochastic crystallization in micron-sized droplets of undercooled liquid l-arabitol.

    PubMed

    Guinet, Yannick; Carpentier, Laurent; Paccou, Laurent; Derollez, Patrick; Hédoux, Alain

    2016-11-29

    Kinetics of isothermal crystallization of l-arabitol were analyzed from the undercooled liquid state within micron-sized droplets from micro-Raman spectroscopy. This study reveals that crystallization slightly above Tg is controlled by stochastic heterogeneous nucleation inherent to the droplet size. Microscopic Raman investigations performed in droplets give the unique opportunity to analyze the pure metastable Form II of l-arabitol. It was found that Form II is characterized by a molecular packing more compact than that of the stable Form I, inherent to strong intermolecular hydrogen bonding. Kinetics laws obtained by analyzing several droplets at different temperatures, reveal the transient character of Form II, quasi systematically detected during the crystallization process of form I. Form II appears as the first step of crystallization prior to successive short-living metastable states which is necessary to achieve a complete crystallization in Form I. It was found that the kinetics of conversion between the metastable states (Form II) into Form I is dependent on the amount of strong hydrogen bonding distinctive of Form II. Copyright © 2016 Elsevier Ltd. All rights reserved.

  9. Fiber-Supported Droplet Combustion Experiment-2

    NASA Technical Reports Server (NTRS)

    Colantonio, Renato O.

    1998-01-01

    A major portion of the energy produced in the world today comes from the burning of liquid hydrocarbon fuels in the form of droplets. Understanding the fundamental physical processes involved in droplet combustion is not only important in energy production but also in propulsion, in the mitigation of combustion-generated pollution, and in the control of the fire hazards associated with handling liquid combustibles. Microgravity makes spherically symmetric combustion possible, allowing investigators to easily validate their droplet models without the complicating effects of gravity. The Fiber-Supported Droplet Combustion (FSDC-2) investigation was conducted in the Microgravity Glovebox facility of the shuttles' Spacelab during the reflight of the Microgravity Science Laboratory (MSL- 1R) on STS-94 in July 1997. FSDC-2 studied fundamental phenomena related to liquid fuel droplet combustion in air. Pure fuels and mixtures of fuels were burned as isolated single and duo droplets with and without forced air convection. FSDC-2 is sponsored by the NASA Lewis Research Center, whose researchers are working in cooperation with several investigators from industry and academia. The rate at which a droplet burns is important in many commercial applications. The classical theory of droplet burning assumes that, for an isolated, spherically symmetric, single-fuel droplet, the gas-phase combustion processes are much faster than the droplet surface regression rate and that the liquid phase is at a uniform temperature equal to the boiling point. Recent, more advanced models predict that both the liquid and gas phases are unsteady during a substantial portion of the droplet's burning history, thus affecting the instantaneous and average burning rates, and that flame radiation is a dominant mechanism that can extinguish flames in a microgravity environment. FSDC-2 has provided well-defined, symmetric droplet burning data including radiative emissions to validate these theoretical

  10. Numerical Simulation of the Combustion of Fuel Droplets: Finite Rate Kinetics and Flame Zone Grid Adaptation (CEFD)

    NASA Technical Reports Server (NTRS)

    Gogos, George; Bowen, Brent D.; Nickerson, Jocelyn S.

    2002-01-01

    The NASA Nebraska Space Grant (NSGC) & EPSCoR programs have continued their effort to support outstanding research endeavors by funding the Numerical Simulation of the Combustion of Fuel Droplets study at the University of Nebraska at Lincoln (UNL). This team of researchers has developed a transient numerical model to study the combustion of suspended and moving droplets. The engines that propel missiles, jets, and many other devices are dependent upon combustion. Therefore, data concerning the combustion of fuel droplets is of immediate relevance to aviation and aeronautical personnel, especially those involved in flight operations. The experiments being conducted by Dr. Gogos and Dr. Nayagam s research teams, allow investigators to gather data for comparison with theoretical predictions of burning rates, flame structures, and extinction conditions. The consequent improved hndamental understanding droplet combustion may contribute to the clean and safe utilization of fossil hels (Williams, Dryer, Haggard & Nayagam, 1997, 72). The present state of knowledge on convective extinction of he1 droplets derives fiom experiments conducted under normal gravity conditions. However, any data obtained with suspended droplets under normal gravity are grossly affected by gravity. The need to obtain experimental data under microgravity conditions is therefore well justified and addresses one of the goals of NASA s Human Exploration and Development of Space (HEDS) microgravity combustion experiment.

  11. The JPL Direct Methanol Liquid-feed PEM Fuel Cell

    NASA Technical Reports Server (NTRS)

    Halpert, G.; Surampudi, S.

    1994-01-01

    Recently, there has been a breakthrough in fuel cell technology in the Energy Storage Systems Group at the Jet Propulsion Laboratory with the develpment of a direct methanol, liquid-feed, solid polymer electrolyte membrane (PEM) fuel cell... The methanol liquid-feed, solid polymer electrolyte (PEM) design has numerous system level advantages over the gas-feed design. These include:...

  12. 40 CFR 1066.970 - Refueling test for liquid fuels.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 33 2014-07-01 2014-07-01 false Refueling test for liquid fuels. 1066.970 Section 1066.970 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) AIR... Emission Test Procedures for Motor Vehicles § 1066.970 Refueling test for liquid fuels. Except as...

  13. Liquid Fuels and Natural Gas in the Americas

    EIA Publications

    2014-01-01

    The Energy Information Administration's (EIA) Liquid Fuels and Natural Gas in the Americas report, published today, is a Congressionally-requested study examining the energy trends and developments in the Americas over the past decade. The report focuses on liquid fuels and natural gas—particularly reserves and resources, production, consumption, trade, and investment—given their scale and significance to the region.

  14. Aircraft-Fuel-Tank Design for Liquid Hydrogen

    NASA Technical Reports Server (NTRS)

    Reynolds, T W

    1955-01-01

    Some of the considerations involved in the design of aircraft fuel tanks for liquid hydrogen are discussed herein. Several of the physical properties of metals and thermal insulators in the temperature range from ambient to liquid-hydrogen temperatures are assembled. Calculations based on these properties indicate that it is possible to build a large-size liquid-hydrogen fuel tank which (1) will weigh less then 15 percent of the fuel weight, (2) will have a hydrogen vaporization rate less than 30 percent of the cruise fuel-flow rate, and (3) can be held in a stand-by condition and readied for flight in a short time.

  15. Thermocapillary migration of liquid droplets in a temperature gradient in a density matched system

    NASA Technical Reports Server (NTRS)

    Rashidnia, N.; Balasubramaniam, R.

    1991-01-01

    An experimental investigation of thermocapillary flow in droplets of a vegetable oil (partially hydrogenated soybean oil) immersed in silicone oil was conducted in a test cell with a heated top wall and a cooled bottom wall. The liquids are nearly immiscible and have equal densities at a temperature below the room temperature, thus providing a simulation of low-gravity conditions by reducing the buoyancy forces. The interfacial tension between the two oils was measured in the temperature range 20 to 50 C using a capillary tube and (d sigma)/(d T) was determined to be negative. Droplets ranging in sizes from 3 mm to 1 cm diameter were injected into the silicone oil. The vertical temperature profile in the bulk liquid (silicone oil) produces temperature variations along the interface which induce variations in the interfacial tension. The flow inside the droplet driven by the resulting interfacial shear stresses was observed using a laser light-sheet flow visualization technique. The flow direction is consistent with the sign of (d sigma)/(d T). The observed maximum surface velocities are compared to the theoretical predictions of Young et al. (1959).

  16. Coloring Rate of Phenolphthalein by Reaction with Alkaline Solution Observed by Liquid-Droplet Collision.

    PubMed

    Takano, Yuuka; Kikkawa, Shigenori; Suzuki, Tomoko; Kohno, Jun-ya

    2015-06-11

    Many important chemical reactions are induced by mixing two solutions. This paper presents a new way to measure rates of rapid chemical reactions induced by mixing two reactant solutions using a liquid-droplet collision. The coloring reaction of phenolphthalein (H2PP) by a reaction with NaOH is investigated kinetically. Liquid droplets of H2PP/ethanol and NaOH/H2O solutions are made to collide, which induces a reaction that transforms H2PP into a deprotonated form (PP(2-)). The concentration of PP(2-) is evaluated from the RGB values of pixels in the colored droplet images, and is measured as a function of the elapsed time from the collision. The obtained rate constant is (2.2 ± 0.7) × 10(3) M(-1) s(-1), which is the rate constant for the rate-determining step of the coloring reaction of H2PP. This method was shown to be applicable to determine rate constants of rapid chemical reactions between two solutions.

  17. Thermocapillary migration of liquid droplets in a temperature gradient in a density matched system

    NASA Technical Reports Server (NTRS)

    Rashidnia, N.; Balasubramaniam, R.

    1989-01-01

    An experimental investigation of thermocapillary flow in droplets of a vegetable oil (partially hydrogenated soybean oil) immersed in silicone oil was conducted in a test cell with a heated top wall and a cooled bottom wall. The liquids are nearly immiscible and have equal densities at a temperature below the room temperature, thus providing a simulation of low-gravity conditions by reducing the buoyancy forces. The interfacial tension between the two oils was measured in the temperature range 20 to 50 C using a capillary tube and (d sigma)/(d T) was determined to be negative. Droplets ranging in sizes from 3 mm to 1 cm diameter were injected into the silicone oil. The vertical temperature profile in the bulk liquid (silicone oil) produces temperature variations along the interface which induce variations in the interfacial tension. The flow inside the droplet driven by the resulting interfacial shear stresses was observed using a laser light-sheet flow visualization technique. The flow direction is consistent with the sign of (d sigma)/(d T). The observed maximum surface velocities are compared to the theoretical predictions of Young et al. (1959).

  18. Low Emissions Burner Technology for Metal Processing Industry using Byproducts and Biomass Derived Liquid Fuels

    SciTech Connect

    Agrawal, Ajay; Taylor, Robert

    2013-09-30

    This research and development efforts produced low-emission burner technology capable of operating on natural gas as well as crude glycerin and/or fatty acids generated in biodiesel plants. The research was conducted in three stages (1) Concept definition leading to the design and development of a small laboratory scale burner, (2) Scale-up to prototype burner design and development, and (3) Technology demonstration with field vefiication. The burner design relies upon the Flow Blurring (FB) fuel injection based on aerodynamically creating two-phase flow near the injector exit. The fuel tube and discharge orifice both of inside diameter D are separated by gap H. For H < 0.25D, the atomizing air bubbles into liquid fuel to create a two-phase flow near the tip of the fuel tube. Pressurized two-phase fuel-air mixture exits through the discharge orifice, which results in expansion and breakup of air bubbles yielding a spray with fine droplets. First, low-emission combustion of diesel, biodiesel and straight VO (soybean oil) was achieved by utilizing FB injector to yield fine sprays for these fuels with significantly different physical properties. Visual images for these baseline experiments conducted with heat release rate (HRR) of about 8 kW illustrate clean blue flames indicating premixed combustion for all three fuels. Radial profiles of the product gas temperature at the combustor exit overlap each other signifying that the combustion efficiency is independent of the fuel. At the combustor exit, the NOx emissions are within the measurement uncertainties, while CO emissions are slightly higher for straight VO as compared to diesel and biodiesel. Considering the large variations in physical and chemical properties of fuels considered, the small differences observed in CO and NOx emissions show promise for fuel-flexible, clean combustion systems. FB injector has proven to be very effective in atomizing fuels with very different physical properties, and it offers a

  19. Integrated design of integral liquid fuel ramjet

    NASA Astrophysics Data System (ADS)

    Gu, Liangxian; Yang, Jianxin; Ma, Jia; Liu, Jingchun

    1993-04-01

    Integrated design of integral liquid fuel ramjet (ILFR) is regarded as a system of the combination of missile and ILFR, which aims at obtaining the optimum performance of the system and optimizing the parameters of both missile and ramjet. In this paper, supersonic cruise missile of medium range is taken as a calculation example. In accordance with the features of integrated ramjet, the integrated design of missile and integral ramjet are discussed here. Missile configuration and ramjet parameters are optimized and then the maximum range is obtained based on two typical cases in medium and low height cruising. Some problems related to choosing missile and ramjet parameters are also, discussed and analyzed for application in different cruise heights.

  20. Biomass gasification for liquid fuel production

    NASA Astrophysics Data System (ADS)

    Najser, Jan; Peer, Václav; Vantuch, Martin

    2014-08-01

    In our old fix-bed autothermal gasifier we tested wood chips and wood pellets. We make experiments for Czech company producing agro pellets - pellets made from agricultural waste and fastrenewable natural resources. We tested pellets from wheat and rice straw and hay. These materials can be very perspective, because they dońt compete with food production, they were formed in sufficient quantity and in the place of their treatment. New installation is composed of allothermal biomass fixed bed gasifier with conditioning and using produced syngas for Fischer - Tropsch synthesis. As a gasifying agent will be used steam. Gas purification will have two parts - separation of dust particles using a hot filter and dolomite reactor for decomposition of tars. In next steps, gas will be cooled, compressed and removed of sulphur and chlorine compounds and carbon dioxide. This syngas will be used for liquid fuel synthesis.

  1. Biomass gasification for liquid fuel production

    SciTech Connect

    Najser, Jan E-mail: vaclav.peer@vsb.cz; Peer, Václav E-mail: vaclav.peer@vsb.cz

    2014-08-06

    In our old fix-bed autothermal gasifier we tested wood chips and wood pellets. We make experiments for Czech company producing agro pellets - pellets made from agricultural waste and fastrenewable natural resources. We tested pellets from wheat and rice straw and hay. These materials can be very perspective, because they dońt compete with food production, they were formed in sufficient quantity and in the place of their treatment. New installation is composed of allothermal biomass fixed bed gasifier with conditioning and using produced syngas for Fischer - Tropsch synthesis. As a gasifying agent will be used steam. Gas purification will have two parts - separation of dust particles using a hot filter and dolomite reactor for decomposition of tars. In next steps, gas will be cooled, compressed and removed of sulphur and chlorine compounds and carbon dioxide. This syngas will be used for liquid fuel synthesis.

  2. Biological production of liquid fuels from biomass

    SciTech Connect

    1982-01-01

    A scheme for the production of liquid fuels from renewable resources such as poplar wood and lignocellulosic wastes from a refuse hydropulper was investigated. The particular scheme being studied involves the conversion of a cellulosic residue, resulting from a solvent delignified lignocellulosic feed, into either high concentration sugar syrups or into ethyl and/or butyl alcohol. The construction of a pilot apparatus for solvent delignifying 150 g samples of lignocellulosic feeds was completed. Also, an analysis method for characterizing the delignified product has been selected and tested. This is a method recommended in the Forage Fiber Handbook. Delignified samples are now being prepared and tested for their extent of delignification and susceptibility to enzyme hydrolysis. Work is continuing on characterizing the cellulase and cellobiase enzyme systems derived from the YX strain of Thermomonospora.

  3. Conversion of olefins to liquid motor fuels

    DOEpatents

    Rabo, Jule A.; Coughlin, Peter K.

    1988-01-01

    Linear and/or branched claim C.sub.2 to C.sub.12 olefins are converted to hydrocarbon mixtures suitable for use as liquid motor fuels by contact with a catalyst capable of ensuring the production of desirable products with only a relatively minor amount of heavy products boiling beyond the diesel oil range. The catalyst having desirable stability during continuous production operations, comprises a steam stabilized zeolite Y catalyst of hydrophobic character, desirably in aluminum-extracted form. The olefins such as propylene, may be diluted with inerts, such as paraffins or with water, the latter serving to moderate the acidity of the catalyst, or to further moderate the activity of the aluminum-extracted catalyst, so as to increase the effective life of the catalyst.

  4. Nucleation of liquid droplets and voids in a stretched Lennard-Jones fcc crystal

    SciTech Connect

    Baidakov, Vladimir G. Tipeev, Azat O.

    2015-09-28

    The method of molecular dynamics simulation has been used to investigate the phase decay of a metastable Lennard-Jones face-centered cubic crystal at positive and negative pressures. It is shown that at high degrees of metastability, crystal decay proceeds through the spontaneous formation and growth of new-phase nuclei. It has been found that there exists a certain boundary temperature. Below this temperature, the crystal phase disintegrates as the result of formation of voids, and above, as a result of formation of liquid droplets. The boundary temperature corresponds to the temperature of cessation of a crystal–liquid phase equilibrium when the melting line comes in contact with the spinodal of the stretched liquid. The results of the simulations are interpreted in the framework of classical nucleation theory. The thermodynamics of phase transitions in solids has been examined with allowance for the elastic energy of stresses arising owing to the difference in the densities of the initial and the forming phases. As a result of the action of elastic forces, at negative pressures, the boundary of the limiting superheating (stretching) of a crystal approaches the spinodal, on which the isothermal bulk modulus of dilatation becomes equal to zero. At the boundary of the limiting superheating (stretching), the shape of liquid droplets and voids is close to the spherical one.

  5. Nucleation of liquid droplets and voids in a stretched Lennard-Jones fcc crystal.

    PubMed

    Baidakov, Vladimir G; Tipeev, Azat O

    2015-09-28

    The method of molecular dynamics simulation has been used to investigate the phase decay of a metastable Lennard-Jones face-centered cubic crystal at positive and negative pressures. It is shown that at high degrees of metastability, crystal decay proceeds through the spontaneous formation and growth of new-phase nuclei. It has been found that there exists a certain boundary temperature. Below this temperature, the crystal phase disintegrates as the result of formation of voids, and above, as a result of formation of liquid droplets. The boundary temperature corresponds to the temperature of cessation of a crystal-liquid phase equilibrium when the melting line comes in contact with the spinodal of the stretched liquid. The results of the simulations are interpreted in the framework of classical nucleation theory. The thermodynamics of phase transitions in solids has been examined with allowance for the elastic energy of stresses arising owing to the difference in the densities of the initial and the forming phases. As a result of the action of elastic forces, at negative pressures, the boundary of the limiting superheating (stretching) of a crystal approaches the spinodal, on which the isothermal bulk modulus of dilatation becomes equal to zero. At the boundary of the limiting superheating (stretching), the shape of liquid droplets and voids is close to the spherical one.

  6. Surfactant Induced Interfacial Anchoring Transitions in Nematic Liquid Crystal Droplets on Glass Surfaces

    NASA Astrophysics Data System (ADS)

    Kulkarni, Siddharth; Thareja, Prachi

    The interfacial adsorption of surfactants at planar nematic liquid crystal (NLC)-water interface induces an ordering transition from a tilted to perpendicular anchoring with the increase in surfactant concentration at CN=C/Ccmc≪1, where Ccmc is the Critical Micelle Concentration of surfactants in water. In this study, we show that depending upon the surfactant structure a tilted to perpendicular NLC anchoring transition is observed at C/Ccmc≥1 in 5CB droplets of size 50-70μm. Micrometer sized 5CB droplets are deposited on glass surfaces using flow coating of 5CB-in-ethanol solutions. When placed on 5CB drop decorated glass surfaces, the aqueous surfactant solutions of aliphatic chain surfactants (SDS, CTAB and CPBr) at CN<1, result in an optical transition to a bright-cross texture attributed to the tilted anchoring of 5CB molecules at 5CB-water interface. At C/Ccmc≥1, perpendicular anchoring of 5CB molecules at 5CB-water interface results in a droplet texture with a hedgehog defect. In contrast, aqueous solutions of SDBS lead to 5CB droplets with a bright-cross texture regardless of the surfactant concentration in the aqueous phase. These results indicate that the orientation of 5CB molecules is independent of the nature of the surfactant headgroup. In addition, 5CB droplet decorated OTS treated glass substrates show a hedgehog texture which disappears completely on exposure to organic vapors with the response time-dependent on the polarity of the vapor molecules.

  7. Infrared thermography-based visualization of droplet transport in liquid sprays

    NASA Astrophysics Data System (ADS)

    Akafuah, Nelson K.; Salazar, Abraham J.; Saito, Kozo

    2010-05-01

    An infrared thermography-based technique for the characterization and visualization of liquid sprays was developed. The technique was tested on two atomizers: a high-speed rotary bell atomizer and a high volume low pressure air-assisted atomizer. The technique uses an infrared thermography-based measurement in which a uniformly heated background acts as a thermal radiation source, and an infrared camera as the receiver. The infrared energy emitted by the radiation source in traveling through the spray is attenuated by the presence of the droplets inside the spray. The infrared intensity is captured by the receiver showing the attenuation in the image as a result of the presence of the spray. The captured thermal image is used to study detailed macroscopic features of the spray flow field and the evolution of the paint droplets as they are transferred from the applicator to the target surface.

  8. Liquid fuels by direct liquefaction of biomass

    SciTech Connect

    Davis, H.G.; Figueroa, C.; Schaleger, L.L.

    1982-03-01

    Conversion of Douglas fir wood chips to a crude fuel oil, under an atmosphere of carbon monoxide, hydrogen and steam has been accomplished by at least two proceses. An oil-wood-flour slurry (oil recycle) process has been operated smoothly at DOE's process development unit (PDU) in Albany, Oregon. Operability was achieved at the cost of extremely high recycle ratio of product oil (about 19/1) and of effluent water. A single pass, water-slurry process, originally developed at the Lawrence Berkeley Laboratory (LBL), has also been tested at Albany. LBL is currently operating a bench-scale continuous liquefaction unit. The feedstock has been an aqueous slurry of prehydrolyzed Douglas fir wood chips. Yields of oil product are higher than was estimated from the Albany experience but are consistently lower than achieved by the recycle process. The difference is real, and is caused by a greater formation of water-soluble products such as carboxylic acids in the water-slurry process. In work to date at LBL, no significant difference in either oil yield or product analysis has been found when the CO-H/sub 2/ reactant gas mixture is replaced by either CO or H/sub 2/ alone. Since CO feed largely reacts to form H/sub 2/ and CO/sub 2/ by shift reaction, it is economically desirable to use a hydrogen-rich reaction gas. The product oil is a crude material, feedable as a heavy liquid fuel oil at temperatures somewhat above ambient, very low in sulfur and nitrogen, but containing 10 to 19% oxygen, largely as phenols. The crude product has been shown to be capable of replacing number 6 fuel oil in the test boiler at the Pittsburgh Energy Technology Center. Process flow sheets, stoichiometry, operating problems, and methods of product characterization are discussed, as well as possibilities for an improved process.

  9. Modeling the Maximum Spreading of Liquid Droplets Impacting Wetting and Nonwetting Surfaces.

    PubMed

    Lee, Jae Bong; Derome, Dominique; Guyer, Robert; Carmeliet, Jan

    2016-02-09

    Droplet impact has been imaged on different rigid, smooth, and rough substrates for three liquids with different viscosity and surface tension, with special attention to the lower impact velocity range. Of all studied parameters, only surface tension and viscosity, thus the liquid properties, clearly play a role in terms of the attained maximum spreading ratio of the impacting droplet. Surface roughness and type of surface (steel, aluminum, and parafilm) slightly affect the dynamic wettability and maximum spreading at low impact velocity. The dynamic contact angle at maximum spreading has been identified to properly characterize this dynamic spreading process, especially at low impact velocity where dynamic wetting plays an important role. The dynamic contact angle is found to be generally higher than the equilibrium contact angle, showing that statically wetting surfaces can become less wetting or even nonwetting under dynamic droplet impact. An improved energy balance model for maximum spreading ratio is proposed based on a correct analytical modeling of the time at maximum spreading, which determines the viscous dissipation. Experiments show that the time at maximum spreading decreases with impact velocity depending on the surface tension of the liquid, and a scaling with maximum spreading diameter and surface tension is proposed. A second improvement is based on the use of the dynamic contact angle at maximum spreading, instead of quasi-static contact angles, to describe the dynamic wetting process at low impact velocity. This improved model showed good agreement compared to experiments for the maximum spreading ratio versus impact velocity for different liquids, and a better prediction compared to other models in literature. In particular, scaling according to We(1/2) is found invalid for low velocities, since the curves bend over to higher maximum spreading ratios due to the dynamic wetting process.

  10. Generation of droplets via oscillations of a tapered capillary tube filled with low-viscosity liquids

    NASA Astrophysics Data System (ADS)

    Mao, Xinyu; Zhang, Lei; Zhao, Zhenhao; Lin, Feng

    2017-06-01

    Droplet formation via the oscillations of a tapered capillary tube is experimentally and numerically investigated using incompressible, low-viscosity Newtonian liquids. As in many other common methods of droplet generation, this technique features a transient flow that is directed out of a nozzle. However, due to the interactions of the oscillations, the tube, and the fluids, the flow rate upstream of the nozzle cannot be directly obtained. In this study, the motion of the tube is measured under the activation of a specific waveform, and the flow inside the tube and drop formation are further numerically studied using a non-inertial reference system in which the tube is stationary. The mechanism of ejection is quantitatively explained by analyzing the temporal variation in the velocity and pressure distributions inside the tube. The dynamics of drop formation, the drop velocity, and the drop radius are studied as functions of the dimensionless groups that govern the problem, including the Ohnesorge number Oh, the Weber number We, the gravitational Bond number G, and various length scale ratios. The results show that droplets are generated due to the inertia of the liquid and velocity amplification in the tapered section. By influencing the balance between the viscous effect and inertial effect of the liquid along the entire tube, the length scale ratios affect the evolution of the transient flow at the nozzle and eventually influence the drop radius and velocity. For liquids with viscosities close to that of pure water, the critical Reynolds number, at which a drop can be generated, linearly depends on the Z number (the reciprocal of Oh) at the nozzle.

  11. Formulating liquid hydrocarbon fuels for SOFCs

    NASA Astrophysics Data System (ADS)

    Saunders, G. J.; Preece, J.; Kendall, K.

    The injection of liquid hydrocarbons directly into an SOFC system is considered for application to hybrid vehicles. The main problem is carbon deposition on the nickel anode when molecules such as ethanol or iso-octane are injected directly. Such carbon deposition has been studied using a microtubular SOFC with a mass spectrometer analysing the product gases to investigate the reaction sequence and also to investigate the deposited carbon by temperature programmed oxidation (TPO). The results show that only two liquids could be injected directly onto nickel cermet anodes without serious carbon blockage, methanol and methanoic acid. Even then, TPO experiments revealed deposition of small amounts of carbon which could be prevented by small additions of air or water to the fuel. Gasoline type molecules like iso-octane killed the SOFC in about 30 min operation, with about 90% of the molecular carbon being deposited on the nickel cermet anode. However, certain mixtures of iso-octane, water, alcohol and surfactant were found to produce beneficial results with remarkably low carbon deposition, less than 1% of the molecular carbon appearing on the anode. Such formulations had octane numbers appropriate to internal combustion engine operation.

  12. Liquid transportation fuels from algal oils

    NASA Astrophysics Data System (ADS)

    Chen, Daichuan

    Liquid transportation fuels from renewable sources are becoming more prominent and important in modem society. Processing of hydrocarbon oils from algae has not been studied in detail in the past, so components which have been proposed for incorporation in algal oils via genetic engineering, such as cuparene, farnesene, phytol and squalene, have been subjected to processing via catalytic cracking in a pulse reactor at different temperatures. The cracking results showed that liquid products contained numerous high octane molecules which make it feasible for use in automobiles. Additionally, canola oil, chosen as an algal oil model compound, was studied as a feed for catalytic cracking in a fixed-bed reactor at atmospheric pressure over different types of zeolites. The results showed that MFI catalysts gave the highest yield of gasoline range products and lowest coke formation. Gallium loaded MFI zeolites increased the total aromatics yield for the canola oil cracking relative to the acid form of the zeolite. Finally, algal oils were cracked on several selected zeolites, and the results showed the same trend as canola oil cracking. MFI gave the highest gasoline yield (43.8 wt%) and lowest coke (4.7 wt%). The total aromatics yield from algae oil cracking is improved 7.8 wt% when MFI is loaded with gallium.

  13. Surfactant-induced ordering and wetting transitions of droplets of thermotropic liquid crystals "caged" inside partially filled polymeric capsules.

    PubMed

    Carlton, Rebecca J; Zayas-Gonzalez, Yashira M; Manna, Uttam; Lynn, David M; Abbott, Nicholas L

    2014-12-16

    We report a study of the wetting and ordering of thermotropic liquid crystal (LC) droplets that are trapped (or "caged") within micrometer-sized cationic polymeric microcapsules dispersed in aqueous solutions of surfactants. When they were initially dispersed in water, we observed caged, nearly spherical droplets of E7, a nematic LC mixture, to occupy ∼40% of the interior volume of the polymeric capsules [diameter of 6.7 ± 0.3 μm, formed via covalent layer-by-layer assembly of branched polyethylenimine and poly(2-vinyl-4,4-dimethylazlactone)] and to contact the interior surface of the capsule wall at an angle of ∼157 ± 11°. The internal ordering of LC within the droplets corresponded to the so-called bipolar configuration (distorted by contact with the capsule walls). While the effects of dodecyltrimethylammonium bromide (DTAB) and sodium dodecyl sulfate (SDS) on the internal ordering of "free" LC droplets are similar, we observed the two surfactants to trigger strikingly different wetting and configurational transitions when LC droplets were caged within polymeric capsules. Specifically, upon addition of SDS to the aqueous phase, we observed the contact angles (θ) of caged LC on the interior surface of the capsule to decrease, resulting in a progression of complex droplet shapes, including lenses (θ ≈ 130 ± 10°), hemispheres (θ ≈ 89 ± 5°), and concave hemispheres (θ < 85°). The wetting transitions induced by SDS also resulted in changes in the internal ordering of the LC to yield states topologically equivalent to axial and radial configurations. Although topologically equivalent to free droplets, the contributions that surface anchoring, LC elasticity, and topological defects make to the free energy of caged LC droplets differ from those of free droplets. Overall, these results and others reported herein lead us to conclude that caged LC droplets offer a platform for new designs of LC-droplet-based responsive soft matter that cannot be

  14. Fabrication and response of high concentration SIMPLE superheated droplet detectors with different liquids

    NASA Astrophysics Data System (ADS)

    Felizardo, M.; Morlat, T.; Marques, J. G.; Ramos, A. R.; Girard, TA; Fernandes, A. C.; Kling, A.; Lázaro, I.; Martins, R. C.; Puibasset, J.

    2013-09-01

    The combined measurement of dark matter interactions with different superheated liquids has recently been suggested as a cross-correlation technique in identifying WIMP candidates. We describe the fabrication of high concentration superheated droplet detectors based on the light nuclei liquids C3F8, C4F8, C4F10 and CCl2F2, and investigation of their irradiation response with respect to C2ClF5. The results are discussed in terms of the basic physics of superheated liquid response to particle interactions, as well as the necessary detector qualifications for application in dark matter search investigations. The possibility of heavier nuclei SDDs is explored using the light nuclei results as a basis, with CF3I provided as an example.

  15. Molecular Beam Studies of Volatile Liquids and Fuel Surrogates Using Liquid MICR

    DTIC Science & Technology

    2014-12-23

    vapor pressure liquids, including octane, isooctane, dodecane, squalane, methylnaphthalene, ethylene glycol , and Jet A and JP-8 fuels themselves...within the error bars. This result implies that the additives in JP-8 (such as fuel system deicer, chemically similar to ethylene glycol ) do not alter...AFRL-OSR-VA-TR-2015-0019 MOLECULAR BEAM STUDIES OF VOLATILE LIQUIDS AND FUEL SURROGATES USING LIQUID MICR Gilbert Nathanson UNIVERSITY OF WISCONSIN

  16. Molecular Beam Studies of Volatile Liquids and Fuel Surrogates Using Liquid Microjets

    DTIC Science & Technology

    2014-12-18

    wide range of high-vapor pressure liquids, including octane, isooctane, dodecane, squalane, methylnaphthalene, ethylene glycol , and Jet A and JP-8 fuels...JP-8 (such as fuel system deicer, chemically similar to ethylene glycol ) do not alter the dynamics of He atom evaporation. We also measured nearly...Molecular Beam Studies of Volatile Liquids and Fuel Surrogates Using Liquid Microjets Gilbert Nathanson, Department of Chemistry University of

  17. Sequential operation droplet array: an automated microfluidic platform for picoliter-scale liquid handling, analysis, and screening.

    PubMed

    Zhu, Ying; Zhang, Yun-Xia; Cai, Long-Fei; Fang, Qun

    2013-07-16

    This contribution describes a sequential operation droplet array (SODA) system, a fully automated droplet-based microfluidic system capable of performing picoliter-scale liquid manipulation, analysis, and screening. The SODA system was built using a tapered capillary-syringe pump module and a two-dimensional (2D) oil-covered droplet array installed on an x-y-z translation stage. With the system, we developed a novel picoliter-scale droplet depositing technique for forming a 2D picoliter-droplet array. On this basis, an automated droplet manipulation method with picoliter precision was established using the programmable combination of the capillary-based liquid aspirating-depositing and the moving of the oil-covered droplet array, the so-called "aspirating-depositing-moving" (ADM) method. Differing from the previously reported droplet systems based on microchips, microcapillaries, or digital microfluidics, this method can achieve complete and flexible droplet manipulations, including droplet assembling, generation, indexing, transferring, splitting, and fusion in the picoliter range, endowing the present system with ultralow sample/reagent consumptions and substantial versatility in analysis and screening for multiple different samples. To demonstrate its feasibility and versatility, we applied the SODA system in multiple experiments required in drug screening, including the screening of inhibitors for capases-1 from a chemical library, the measurement of IC50 values for the identified inhibitors, and the screening of the synergistic effect of multiple inhibitors. In the experiments, the consumptions of samples and reagents are only 60-180 pL for each droplet microreactor, which are commonly 3-5 orders of magnitude lower than those of conventional multiwell plate systems, and 1-2 orders of magnitude lower than other droplet-based microfluidic systems for multiple sample screening. The ability of the SODA system in performing complicated and multistep droplet

  18. Series of Two Droplets on Fiber Approaching Ignition

    NASA Technical Reports Server (NTRS)

    2003-01-01

    The Fiber-Supported Droplet Combustion (FSDC) uses two droplets positioned on the fiber wire, instead of the usual one. Two droplets more closely simulates the environment in engines, which ignite many fuel droplets at once. The behavior of the burning was also unexpected -- the droplets moved together after ignition, generating quite a bit of data for understanding the interaction of fuel droplets while they burn. Because FSDC is backlit (the bright glow behind the drops), you carnot see the glow of the droplets while they burn -- instead, you see them shrink! The small blobs left on the wire after the burn are the beads used to center the fuel droplet on the wire. This image was taken on STS-94, July 12, 1997, MET:10/19:13 (approximate). FSDC-2 studied fundamental phenomena related to liquid fuel droplet combustion in air. Pure fuels and mixtures of fuels were burned as isolated single and dual droplets with and without forced air convection. The FSDC guest investigator was Forman Williams, University of California, San Diego. The experiment was part of the space research investigations conducted during the Microgravity Science Laboratory-1R mission (STS-94, July 1-17 1997). Advanced combustion experiments will be a part of investigations planned for the International Space Station. (251KB JPEG, 1350 x 1523 pixels; downlinked video, higher quality not available) The MPG from which this composite was made is available at http://mix.msfc.nasa.gov/ABSTRACTS/MSFC-0300179.html

  19. Series of Two Droplets on Fiber Approaching Ignition

    NASA Technical Reports Server (NTRS)

    2003-01-01

    The Fiber-Supported Droplet Combustion (FSDC) uses two droplets positioned on the fiber wire, instead of the usual one. Two droplets more closely simulates the environment in engines, which ignite many fuel droplets at once. The behavior of the burning was also unexpected -- the droplets moved together after ignition, generating quite a bit of data for understanding the interaction of fuel droplets while they burn. Because FSDC is backlit (the bright glow behind the drops), you carnot see the glow of the droplets while they burn -- instead, you see them shrink! The small blobs left on the wire after the burn are the beads used to center the fuel droplet on the wire. This image was taken on STS-94, July 12, 1997, MET:10/19:13 (approximate). FSDC-2 studied fundamental phenomena related to liquid fuel droplet combustion in air. Pure fuels and mixtures of fuels were burned as isolated single and dual droplets with and without forced air convection. The FSDC guest investigator was Forman Williams, University of California, San Diego. The experiment was part of the space research investigations conducted during the Microgravity Science Laboratory-1R mission (STS-94, July 1-17 1997). Advanced combustion experiments will be a part of investigations planned for the International Space Station. (251KB JPEG, 1350 x 1523 pixels; downlinked video, higher quality not available) The MPG from which this composite was made is available at http://mix.msfc.nasa.gov/ABSTRACTS/MSFC-0300179.html

  20. High energy-density liquid rocket fuel performance

    NASA Technical Reports Server (NTRS)

    Rapp, Douglas C.

    1990-01-01

    A fuel performance database of liquid hydrocarbons and aluminum-hydrocarbon fuels was compiled using engine parametrics from the Space Transportation Engine Program as a baseline. Propellant performance parameters are introduced. General hydrocarbon fuel performance trends are discussed with respect to hydrogen-to-carbon ratio and heat of formation. Aluminum-hydrocarbon fuel performance is discussed with respect to aluminum metal loading. Hydrocarbon and aluminum-hydrocarbon fuel performance is presented with respect to fuel density, specific impulse, and propellant density specific impulse.

  1. High energy-density liquid rocket fuel performance

    NASA Technical Reports Server (NTRS)

    Rapp, Douglas C.

    1990-01-01

    A fuel performance database of liquid hydrocarbons and aluminum-hydrocarbon fuels was compiled using engine parametrics from the Space Transportation Engine Program as a baseline. Propellant performance parameters are introduced. General hydrocarbon fuel performance trends are discussed with respect to hydrogen-to-carbon ratio and heat of formation. Aluminum-hydrocarbon fuel performance is discussed with respect to aluminum metal loading. Hydrocarbon and aluminum-hydrocarbon fuel performance is presented with respect to fuel density, specific impulse and propellant density specific impulse.

  2. High energy-density liquid rocket fuel performance

    NASA Technical Reports Server (NTRS)

    Rapp, Douglas C.

    1990-01-01

    A fuel performance database of liquid hydrocarbons and aluminum-hydrocarbon fuels was compiled using engine parametrics from the Space Transportation Engine Program as a baseline. Propellant performance parameters are introduced. General hydrocarbon fuel performance trends are discussed with respect to hydrogen-to-carbon ratio and heat of formation. Aluminum-hydrocarbon fuel performance is discussed with respect to aluminum metal loading. Hydrocarbon and aluminum-hydrocarbon fuel performance is presented with respect to fuel density, specific impulse and propellant density specific impulse.

  3. Milking liquid nano-droplets by an IR laser: a new modality for the visualization of electric field lines

    NASA Astrophysics Data System (ADS)

    Vespini, Veronica; Coppola, Sara; Grilli, Simonetta; Paturzo, Melania; Ferraro, Pietro

    2013-04-01

    Liquid handling at micron- and nano-scale is of paramount importance in many fields of application such as biotechnology and biochemistry. In fact, the microfluidics technologies play an important role in lab-on-a-chip devices and, in particular, the dispensing of liquid droplets is a required functionality. Different approaches have been developed for manipulating, dispensing and controlling nano-droplets under a wide variety of configurations. Here we demonstrate that nano-droplets can be drawn from liquid drop or film reservoirs through a sort of milking effect achieved by the absorption of IR laser radiation into a pyroelectric crystal. The generation of the pyroelectric field induced by the IR laser is calculated numerically and a specific experiment has been designed to visualize the electric field stream lines that are responsible for the liquid milking effect. The experiments performed are expected to open a new route for the visualization, measure and characterization procedures in the case of electrohydrodynamic applications.

  4. Impact of a heterogeneous liquid droplet on a dry surface: application to the pharmaceutical industry.

    PubMed

    Bolleddula, D A; Berchielli, A; Aliseda, A

    2010-09-15

    Droplet impact has been studied for over a hundred years dating back to the pioneering work of Worthington. In fact, much of his ingenuity contributed to modern day high speed photography. Over the past 40 years significant contributions in theoretical, numerical, and experimental work have been made. Droplet impact is a problem of fundamental importance due to the wealth of applications involved, namely, spray coating, spray painting, delivery of agricultural chemicals, spray cooling, inkjet printing, soil erosion due to rain drop impact, and turbine wear. Here we highlight one specific application, spray coating. Although most studies have focused their efforts on low viscosity Newtonian fluids, many industrial applications such as spray coating utilize more viscous and complex rheology liquids. Determining dominant effects and quantifying their behavior for colloidal suspensions and polymer solutions remains a challenge and thus has eluded much effort. In the last decade, it has been shown that introducing polymers to Newtonian solutions inhibits the rebounding of a drop upon impact, Bergeron et al. Furthermore Bartolo et al. concluded that the normal stress component of the elongational viscosity was responsible for the rebounding inhibition of polymer based non-Newtonian solutions. We aim to uncover the drop impact dynamics of highly viscous Newtonian and complex rheology liquids used in pharmaceutical coating processes. The generation and impact of drops of mm and microm size drops of coating liquids and glycerol/water mixtures on tablet surfaces are systematically studied over a range of We approximately O(1-300), Oh approximately O(10(-2)-1), and Re approximately O(1-700). We extend the range of Oh to values above 1, which are not available to previous studies of droplet impacts. Outcomes reveal that splashing and rebounding are completely inhibited and the role of wettability is negligible in the early stages of impact. The maximum spreading diameter of

  5. Effect of oil droplets and their solid/liquid composition on the phase separation of protein-polysaccharide mixtures.

    PubMed

    Hanazawa, Tomohito; Murray, Brent S

    2013-08-06

    The phase separation of a model system consisting of sodium caseinate + xanthan ± a low fraction (up to 3 wt %) of an oil-in-water emulsion was studied at room temperature (20-25 °C). The composition of the oil phase was either 100 wt % n-tetradecane (TD); 50% TD + 50% eicosane (EC) or 100% EC. The droplets in these three "emulsions" were therefore totally liquid, partially solid, and totally solid, respectively. In the presence of 22 mM CaCl2, the mixed TD+EC droplets were most effective at inhibiting phase separation, while the EC emulsions could not prevent phase separation at all. At 32 mM CaCl2 the emulsions tended to promote phase separation, possibly due to enhanced calcium ion-induced droplet aggregation. The apparent interfacial viscosity (ηi) between two macroscopically separated phases was also measured. In the presence of the semisolid mixed droplets ηi = 25 mN s m(-1), significantly higher than ηi with the pure (liquid) TD droplets (15 mN s m(-1)) or with the pure solid EC droplets (12 mN s m(-1)) or in the absence of droplets (<3 mN s m(-1)). Confocal microscopy showed that the microstructure of the phase separating regions also depended upon the composition of the oil droplets, and it is tentatively suggested that the more marked effects of the mixed emulsion droplets were due to them forming a stronger network at the interface via partial coalescence. Control of the extent of interfacial aggregation of droplets is therefore possibly one way to influence the course of phase separation in biopolymer mixtures.

  6. Recognition of lunar glass droplets produced directly from endogenous liquids - The evidence from S-ZN coatings

    NASA Technical Reports Server (NTRS)

    Butler, P., Jr.

    1978-01-01

    Concentrated deposits of ultramafic droplets of green glass at Apollo 15 and orange and black glass at Apollo 17 are generally accepted as having volcanic, and so endogenous, origins. Since these droplets have S + Zn surface coatings with characteristics that fit a volcanic origin, the presence of similar coatings on dispersed droplets are taken as a good criterion of their volcanic origin. This criterion in concert with other criteria (homogeneity, absence of shocked relicts) that distinguish between volcanic and impact origins, has led to identification of a new ultramafic endogenous liquid that was erupted at Apollo 15. The brown glass droplets representing this liquid have a higher TiO2 content and are more mafic than any of the Apollo 15 basalts.

  7. Recognition of lunar glass droplets produced directly from endogenous liquids - The evidence from S-ZN coatings

    NASA Technical Reports Server (NTRS)

    Butler, P., Jr.

    1978-01-01

    Concentrated deposits of ultramafic droplets of green glass at Apollo 15 and orange and black glass at Apollo 17 are generally accepted as having volcanic, and so endogenous, origins. Since these droplets have S + Zn surface coatings with characteristics that fit a volcanic origin, the presence of similar coatings on dispersed droplets are taken as a good criterion of their volcanic origin. This criterion in concert with other criteria (homogeneity, absence of shocked relicts) that distinguish between volcanic and impact origins, has led to identification of a new ultramafic endogenous liquid that was erupted at Apollo 15. The brown glass droplets representing this liquid have a higher TiO2 content and are more mafic than any of the Apollo 15 basalts.

  8. Negative pressures and melting point depression in oxide-coated liquid metal droplets

    NASA Technical Reports Server (NTRS)

    Spaepen, F.; Turnbull, D.

    1979-01-01

    Negative pressures and melting point depression in oxide-coated liquid metal droplets are studied. The calculation presented show the existence of large negative pressures when the oxide coating is thick enough. The change in the melting point caused by these negative pressures should be considered in studies of homogeneous crystal nucleation. Furthermore, since the negative pressure raises the entropy of the melt, it increases the entropy loss at the crystal-melt interface; the resulting increase of the surface tension could have a large effect on the homogeneous nucleation frequency.

  9. Large scale molecular dynamics simulations of a liquid crystalline droplet with fast multipole implementations

    SciTech Connect

    Wang, Z.; Lupo, J.; Patnaik, S.S.; McKenney, A.; Pachter, R.

    1999-07-01

    The Fast Multipole Method (FMM) offers an efficient way (order O(N)) to handle long range electrostatic interactions, thus enabling more realistic molecular dynamics simulations of large molecular systems. The performance of the fast molecular dynamics (FMD) code, a parallel MD code being developed in the group, using the three-dimensional fast multipole method, shows a good speedup. The application to the full atomic-scale molecular dynamics simulation of a liquid crystalline droplet of 4-n-pentyl-4{prime}-cyanobiphenyl (5CB) molecules, of size 35,872 atoms, shows strong surface effects on various orientational order parameters.

  10. Cavitation and spallation in liquid metal droplets produced by subpicosecond pulsed laser radiation

    NASA Astrophysics Data System (ADS)

    Krivokorytov, M. S.; Vinokhodov, A. Yu.; Sidelnikov, Yu. V.; Krivtsun, V. M.; Kompanets, V. O.; Lash, A. A.; Koshelev, K. N.; Medvedev, V. V.

    2017-03-01

    The deformation and fragmentation of liquid metal microdroplets by intense subpicosecond Ti:sapphire laser pulses is experimentally studied with stroboscopic shadow photography. The experiments are performed at a peak intensity of 1014W /c m2 at the target's surface, which produces shock waves with pressures in the Mbar range. As a result of such a strong impact, the droplet is transformed into a complex-shaped hollow structure that undergoes asymmetrical expansion and eventually fragments. The hollow structure of the expanding target is explained by the effects of cavitation and spallation that follow the propagation of the laser-induced shock wave.

  11. Deformation and burst of a liquid droplet freely suspended in a linear shear field

    NASA Technical Reports Server (NTRS)

    Barthes-Biesel, D.; Acrivos, A.

    1973-01-01

    A theoretical method is presented for predicting the deformation and the conditions for breakup of a liquid droplet freely suspended in a general linear shear field. This is achieved by expanding the solution to the creeping-flow equations in powers of the deformation parameter epsilon and using linear stability theory to determine the onset of bursting. When compared with numerical solutions and with the available experimental data, the theoretical results are generally found to be of acceptable accuracy although, in some cases, the agreement is only qualitative.

  12. Conceptual design for a kerosene fuel-rich gas-generator of a turbopump-fed liquid rocket engine

    NASA Astrophysics Data System (ADS)

    Son, Min; Koo, Jaye; Cho, Won Kook; Lee, Eun Seok

    2012-10-01

    A design method for a kerosene fuel-rich gas-generator of a liquid rocket engine using turbopumps to supply propellant was performed at a conceptual level. The gas-generator creates hot gases, enabling the turbine to operate the turbopumps. A chemical non-equilibrium analysis and a droplet vaporization model were used for the estimation of the burnt gas properties and characteristic chamber length. A premixed counter-flow flame analysis was performed for the prediction of the burnt gas properties, namely the temperature, the specific heat ratio and heat capacity, and the chemical reaction time. To predict the vaporization time, the Spalding model, using a single droplet in convective condition, was used. The minimum residence time in the chamber and the characteristic length were calculated by adding the reaction time and the vaporization time. Using the characteristic length, the design methods for the fuel-rich gas-generator were established. Finally, a parametric study was achieved for the effects of the O/F ratio, mass flow rate, chamber pressure, initial droplet temperature, initial droplet diameter and initial droplet velocity.

  13. Evaporation of liquid droplets on solid substrates. I. Flat substrate with pinned or moving contact line

    NASA Astrophysics Data System (ADS)

    Amini, Amirhossein; Homsy, G. M.

    2017-04-01

    We study the evolution of the profile of a two-dimensional volatile liquid droplet that is evaporating on a flat heated substrate. We adopt a one-sided model with thermal control that, together with the lubrication approximation, results in an evolution equation for the local height of the droplet. Without requiring any presumption for the shape of the drop, the problem is formulated for the two modes of evaporation: a pinned contact line and a moving contact line with fixed contact angle. Numerical solutions are provided for each case. For the pinned contact line case, we observe that after a time interval the contact angle dynamics become nonlinear and, interestingly, the local contact angle goes to zero in advance of total evaporation of the drop. For the case of a moving contact line, in which the singularity at the contact line is treated by a numerical slip model, we find that the droplet nearly keeps its initial circular shape and that the contact line recedes with constant speed.

  14. A combined droplet train and ambient pressure photoemission spectrometer for the investigation of liquid/vapor interfaces

    SciTech Connect

    Starr, David E.; Wong, Ed K.; Worsnop, Douglas R.; Wilson, Kevin R.; Bluhm, Hendrik

    2008-05-01

    We describe a combined ambient pressure photoelectron spectroscopy/droplet train apparatus for investigating the nature and heterogeneous chemistry of liquid/vapor interfaces. In this instrument a liquid droplet train with typical droplet diameters from 50...150 {micro}m is produced by a vibrating orifice aerosol generator (VOAG). The droplets are irradiated by soft X-rays (100...1500 eV) in front of the entrance aperture of a differentially pumped electrostatic lens system that transfers the emitted electrons into a conventional hemispherical electron analyzer. The photoemission experiments are performed at background pressures of up to several Torr, which allows the study of environmentally important liquid/vapor interfaces, in particular aqueous solutions, under equilibrium conditions. The exposure time of the droplet surface to the background gases prior to the XPS measurement can be varied, which will allow future kinetic measurements of gas uptake on liquid surfaces. As an example, a measurement of the surface composition of a {chi} = 0.21 aqueous methanol solution is presented. The concentration of methanol at the vapor/liquid interface is enhanced by a factor of about 3 over the bulk value, while the expected bulk value is recovered at depths larger than about 1.5 nm.

  15. Measurement of interactions between solid particles, liquid droplets, and/or gas bubbles in a liquid using an integrated thin film drainage apparatus.

    PubMed

    Wang, Louxiang; Sharp, David; Masliyah, Jacob; Xu, Zhenghe

    2013-03-19

    A novel device was designed to measure drainage dynamics of thin liquid films confined between a solid particle, an immiscible liquid droplet, and/or gas bubble. Equipped with a bimorph force sensor, a computer-interfaced video capture, and a data acquisition system, the newly designed integrated thin film drainage apparatus (ITFDA) allows for the direct and simultaneous measurements of force barrier, true film drainage time, and bubble/droplet deformation under a well-controlled external force, receding and advancing contact angles, capillary force, and adhesion (detachment) force between an air bubble or oil droplet and a solid, a liquid, or an air bubble in an immiscible liquid. Using the diaphragm of a high-frequency speaker as the drive mechanism for the air bubble or oil droplet attached to a capillary tube, this newly designed device is capable of measuring forces over a wide range of hydrodynamic conditions, including bubble approach and retract velocities up to 50 mm/s and displacement range up to 1 mm. The results showed that the ITFDA was capable of measuring hydrodynamic resistance, film drainage time, and other important physical parameters between air bubbles and solid particles in aqueous solutions. As an example of illustrating the versatility, the ITFDA was also applied to other important systems such as interactions between air bubble and oil droplet, two air bubbles, and two oil droplets in an aqueous solution.

  16. Chemistry in the Venus clouds: Sulfuric acid reactions and freezing behavior of aqueous liquid droplets

    NASA Astrophysics Data System (ADS)

    Delitsky, M. L.; Baines, K. H.

    2015-11-01

    Venus has a thick cloud deck at 40-70 km altitude consisting of liquid droplets and solid particles surrounded by atmospheric gases. The liquid droplets are highly concentrated aqueous solutions of sulfuric acid ranging in concentration from 70-99 wt%. Weight percent drops off with altitude (Imamura and Hashimoto 2001). There will be uptake of atmospheric gases into the droplet solutions and the ratios of gas-phase to liquid-phase species will depend on the Henry’s Law constant for those solutions. Reactions of sulfuric acid with these gases will form products with differing solubilities. For example, uptake of HCl by H2SO4/H2O droplets yields chlorosulfonic acid, ClSO3H (Robinson et al 1998) in solution. This may eventually decompose to thionyl- or sulfuryl chlorides, which have UV absorbances. HF will also uptake, creating fluorosulfonic acid, FSO3H, which has a greater solubility than the chloro- acid. As uptake continues, there will be many dissolved species in the cloudwaters. Baines and Delitsky (2013) showed that uptake will have a maximum at ~62 km and this is very close to the reported altitude for the mystery UV absorber in the Venus atmosphere. In addition, at very strong concentrations in lower altitude clouds, sulfuric acid will form hydrates such as H2SO4.H2O and H2SO4.4H2O which will have very different freezing behavior than sulfuric acid, with much higher freezing temperatures (Carslaw et al, 1997). Using temperature data from Venus Express from Tellmann et al (2009), and changes in H2SO4 concentrations as a function of altitude (James et al 1997), we calculate that freezing out of sulfuric acid hydrates can be significant down to as low as 56 km altitude. As a result, balloons, aircraft or other probes in the Venus atmosphere may be limited to flying below certain altitudes. Any craft flying at altitudes above ~55 km may suffer icing on the wings, propellers, balloons and instruments which could cause possible detrimental effects (thermal

  17. TOPICAL REVIEW Elasto-capillarity: deforming an elastic structure with a liquid droplet

    NASA Astrophysics Data System (ADS)

    Roman, B.; Bico, J.

    2010-12-01

    Although negligible at macroscopic scales, capillary forces become dominant as the sub-millimetric scales of micro-electro-mechanical systems (MEMS) are considered. We review various situations, not limited to micro-technologies, where capillary forces are able to deform elastic structures. In particular, we define the different length scales that are relevant for 'elasto-capillary' problems. We focus on the case of slender structures (lamellae, rods and sheets) and describe the size of a bundle of wet hair, the condition for a flexible rod to pierce a liquid interface or the fate of a liquid droplet deposited on a flexible thin sheet. These results can be generalized to similar situations involving adhesion or fracture energy, which widens the scope of possible applications from biological systems, to stiction issues in micro-fabrication processes, the manufacturing of 3D microstructures or the formation of blisters in thin film coatings.

  18. Mechanically Stretchable and Electrically Insulating Thermal Elastomer Composite by Liquid Alloy Droplet Embedment

    PubMed Central

    Jeong, Seung Hee; Chen, Si; Huo, Jinxing; Gamstedt, Erik Kristofer; Liu, Johan; Zhang, Shi-Li; Zhang, Zhi-Bin; Hjort, Klas; Wu, Zhigang

    2015-01-01

    Stretchable electronics and soft robotics have shown unsurpassed features, inheriting remarkable functions from stretchable and soft materials. Electrically conductive and mechanically stretchable materials based on composites have been widely studied for stretchable electronics as electrical conductors using various combinations of materials. However, thermally tunable and stretchable materials, which have high potential in soft and stretchable thermal devices as interface or packaging materials, have not been sufficiently studied. Here, a mechanically stretchable and electrically insulating thermal elastomer composite is demonstrated, which can be easily processed for device fabrication. A liquid alloy is embedded as liquid droplet fillers in an elastomer matrix to achieve softness and stretchability. This new elastomer composite is expected useful to enhance thermal response or efficiency of soft and stretchable thermal devices or systems. The thermal elastomer composites demonstrate advantages such as thermal interface and packaging layers with thermal shrink films in transient and steady-state cases and a stretchable temperature sensor. PMID:26671673

  19. Droplet formation from the breakup of micron-sized liquid jets

    NASA Astrophysics Data System (ADS)

    van Hoeve, Wim; van der Bos, Arjan; Versluis, Michel; Snoeijer, Jacco; Brenner, Michael P.; Lohse, Detlef

    2009-11-01

    Droplet formation from the breakup of a liquid jet emerging from a micron-sized circular nozzle is investigated with ultra high-speed imaging at 1 million frames per second and within a lubrication approximation model [Eggers and Dupont, Phys. Rev. Lett. 262, 1994, 205-221]. The capillary time τc= √ρr^3 / γ is extremely small -- of the order of 1μs. In the analyzed low Reynolds number regime the jet breakup is driven by surface tension forces only. Rayleigh breakup is not influenced by the surrounding air. The high- speed imaging results and those from the model calculation perfectly agree for various liquid viscosities and jet velocities, confirming a universal scaling law also for diminutive Rayleigh jets.

  20. Vapor explosions during the impact of molten tin droplets into a liquid pool

    NASA Astrophysics Data System (ADS)

    Kouraytem, Nadia; Li, Er Qiang; Thoroddsen, Sigurdur

    2014-11-01

    High-speed video imaging is used to study the impact of a molten tin droplet into a liquid pool. Three different regimes have been identified as nucleation boiling, film boiling or vapor explosion. The latter generally comprises two stages; during the first stage, vapor gets entrapped into the molten tin drop and then, at a second stage, the vapor is superheated by the tin material, creating a violent expansion (explosion). It was observed that the addition of surfactant to the fluid pool could promote the explosion and make it occur at a lower temperature. Furthermore, other parameters such as the pool liquid surface tension, boiling temperature, viscosity and molten tin temperature have been varied to examine the explosion dynamics.

  1. Instability of nano- and microscale liquid metal filaments: Transition from single droplet collapse to multidroplet breakup

    SciTech Connect

    Hartnett, Chris A.; Mahady, Kyle; Fowlkes, Jason Davidson; Afkhami, Shahriar; Rack, P. D.; Kondic, L.

    2015-11-23

    We carry out experimental and numerical studies to investigate the collapse and breakup of finite size, nano- and microscale, liquid metal filaments supported on a substrate. We find the critical dimensions below which filaments do not break up but rather collapse to a single droplet. The transition from collapse to breakup can be described as a competition between two fluid dynamic phenomena: the capillary driven end retraction and the Rayleigh–Plateau type instability mechanism that drives the breakup. We focus on the unique spatial and temporal transition region between these two phenomena using patterned metallic thin film strips and pulsed-laser-induced dewetting. The experimental results are compared to an analytical model proposed by Driessen et al. and modified to include substrate interactions. Additionally, we report the results of numerical simulations based on a volume-of-fluid method to provide additional insight and highlight the importance of liquid metal resolidification, which reduces inertial effects.

  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. Wire melting and droplet atomization in a high velocity oxy-fuel jet

    SciTech Connect

    Neiser, R.A.; Brockmann, J.E.; O`Hern, T.J.

    1995-07-01

    Coatings produced by feeding a steel wire into a high-velocity oxy-fuel (HVOF) torch are being intensively studied by the automotive industry as a cost-effective alternative to the more expensive cast iron sleeves currently used in aluminum engine blocks. The microstructure and properties of the sprayed coatings and the overall economics of the process depend critically on the melting and atomization occurring at the wire tip. This paper presents results characterizing several aspects of wire melting and droplet breakup in an HVOF device. Fluctuations in the incandescent emission of the plume one centimeter downstream from the wire tip were recorded using a fast photodiode. A Fourier transform of the light traces provided a measure of the stripping rate of molten material from the wire tip. Simultaneous in-flight measurement of atomized particle size and velocity distributions were made using a Phase Doppler Particle Analyzer (PDPA). The recorded size distributions approximate a log-normal distribution. Small particles traveled faster than large particles, but the difference was considerably smaller than simple aerodynamic drag arguments would suggest. A set of experiments was carried out to determine the effect that variations in torch gas flow rates have on wire melt rate, average particle size, and average particle velocity. The observed variation of particle size with spray condition is qualitatively consistent with a Weber breakup of the droplets coming off the wire. The measurements also showed that it was possible to significantly alter atomized particle size and velocity without appreciably changing the wire melt rate.

  4. Two Droplets on Wire Approaching Ignition

    NASA Technical Reports Server (NTRS)

    2003-01-01

    The Fiber-Supported Droplet Combustion (FSDC) uses two droplets positioned on the fiber wire, instead of the usual one. Two droplets more closely simulates the environment in engines, which ignite many fuel droplets at once. The behavior of the burning was also unexpected -- the droplets moved together after ignition, generating quite a bit of data for understanding the interaction of fuel droplets while they burn. This MPEG movie (1.3 MB) shows a time-lapse of this burn (3x speed). Because FSDC is backlit (the bright glow behind the drops), you carnot see the glow of the droplets while they burn -- instead, you see them shrink! The small blobs left on the wire after the burn are the beads used to center the fuel droplet on the wire. This image was taken on STS-94, July 12, 1997, MET:10/19:13 (approximate). FSDC-2 studied fundamental phenomena related to liquid fuel droplet combustion in air. Pure fuels and mixtures of fuels were burned as isolated single and dual droplets with and without forced air convection. The FSDC guest investigator was Forman Williams, University of California, San Diego. The experiment was part of the space research investigations conducted during the Microgravity Science Laboratory-1R mission (STS-94, July 1-17 1997). Advanced combustion experiments will be a part of investigations planned for the International Space Station. (1.3MB, 12-second MPEG, screen 320 x 240 pixels; downlinked video, higher quality not available) A still JPG composite of this movie is available at http://mix.msfc.nasa.gov/ABSTRACTS/MSFC-0300178.html.

  5. Electrochemical device for syngas and liquid fuels production

    DOEpatents

    Braun, Robert J.; Becker, William L.; Penev, Michael

    2017-04-25

    The invention relates to methods for creating high value liquid fuels such as gasoline, diesel, jet and alcohols using carbon dioxide and water as the starting raw materials and a system for using the same. These methods combine a novel solid oxide electrolytic cell (SOEC) for the efficient and clean conversion of carbon dioxide and water to hydrogen and carbon monoxide, uniquely integrated with a gas-to-liquid fuels producing method.

  6. Application of linear polarized light for the discrimination of frozen and liquid droplets in ice nucleation experiments

    NASA Astrophysics Data System (ADS)

    Clauss, T.; Kiselev, A.; Hartmann, S.; Augustin, S.; Pfeifer, S.; Niedermeier, D.; Wex, H.; Stratmann, F.

    2013-04-01

    We report on the development and test results of the new optical particle counter TOPS-Ice (Thermo-stabilized Optical Particle Spectrometer for the detection of Ice). The instrument uses measurements of the cross-polarized scattered light by single particles into the near-forward direction (42.5° ± 12.7°) to distinguish between spherical and non-spherical particles. This approach allows the differentiation between liquid water droplets (spherical) and ice particles (non-spherical) having similar volume-equivalent sizes and therefore can be used to determine the fraction of frozen droplets in a typical immersion freezing experiment. We show that the numerical simulation of the light scattered on non-spherical particles (spheroids in random orientation) considering the actual scattering geometry used in the instrument supports the validity of the approach, even though the cross-polarized component of the light scattered by spherical droplets does not vanish in this scattering angle. For the separation of the ice particle mode from the liquid droplet mode, we use the width of the pulse detected in the depolarization channel instead of the pulse height. Exploiting the intrinsic relationship between pulse height and pulse width for Gaussian pulses allows us to calculate the fraction of frozen droplets even if the liquid droplet mode dominates the particle ensemble. We present test results obtained with TOPS-Ice in the immersion freezing experiments at the laminar diffusion chamber LACIS (Leipzig Aerosol Cloud Interaction Simulator) and demonstrate the excellent agreement with the data obtained in similar experiments with a different optical instrument. Finally, the advantages of using the cross-polarized light measurements for the differentiation of liquid and frozen droplets in the realistic immersion freezing experiments are discussed.

  7. High-Voltage Droplet Dispenser Developed

    NASA Technical Reports Server (NTRS)

    Eichenberg, Dennis J.; VanderWal, Randy L.

    2001-01-01

    Various techniques have been applied to deploying individual droplets for many applications, such as the study of the combustion of liquid fuels. Isolated droplet studies are useful in that they allow phenomena to be studied under well-controlled and simplified conditions. A high-voltage droplet dispenser has been developed that is extremely effective in dispensing a wide range of droplets. The dispenser is quite unique in that it utilizes a droplet bias voltage, as well as an ionization pulse, to release the droplet. The droplet is deployed from the end of a needle. A flat-tipped, stainless steel needle attached to a syringe dispenses a known value of liquid that hangs on the needle tip. Somewhat below the droplet is an annular ring electrode. A bias voltage, followed by a voltage pulse, is applied to attract the droplet sufficiently to pull it off the needle. The droplet and needle are oppositely charged relative to the annular electrode. The needle is negatively charged, and the annular ring is positively charged.

  8. Liquid-Feed Methanol Fuel Cell With Membrane Electrolyte

    NASA Technical Reports Server (NTRS)

    Surampudi, Subbarao; Narayanan, S. R.; Halpert, Gerald; Frank, Harvey; Vamos, Eugene

    1995-01-01

    Fuel cell generates electricity from direct liquid feed stream of methanol/water solution circulated in contact with anode, plus direct gaseous feed stream of air or oxygen in contact with cathode. Advantages include relative simplicity and elimination of corrosive electrolytic solutions. Offers potential for reductions in size, weight, and complexity, and for increases in safety of fuel-cell systems.

  9. Parametric Design Studies on a Direct Liquid Feed Fuel Cell

    NASA Technical Reports Server (NTRS)

    Frank, H. A.; Narayanan, S. R.; Nakamura, B.; Surampudi, S.; Halpert, G.

    1995-01-01

    Parametric design studies were carried out on a direct methanol liquid feed fuel cell employing 1 M MeOH fuel, air and oxygen as oxidant in a 2 inch x 2 inch cell employing polymeric electrolyte membranes. Measurements include voltage-current output parameters, methanol crossover rate, and impedance as a function of several design and operational variables. Design variables are described.

  10. Liquid-Feed Methanol Fuel Cell With Membrane Electrolyte

    NASA Technical Reports Server (NTRS)

    Surampudi, Subbarao; Narayanan, S. R.; Halpert, Gerald; Frank, Harvey; Vamos, Eugene

    1995-01-01

    Fuel cell generates electricity from direct liquid feed stream of methanol/water solution circulated in contact with anode, plus direct gaseous feed stream of air or oxygen in contact with cathode. Advantages include relative simplicity and elimination of corrosive electrolytic solutions. Offers potential for reductions in size, weight, and complexity, and for increases in safety of fuel-cell systems.

  11. Liquid-fueled SOFC power sources for transportation

    SciTech Connect

    Myles, K.M.; Doshi, R.; Kumar, R.; Krumpelt, M.

    1994-11-01

    Traditionally, fuel cells have been developed for space or stationary terrestrial applications. As the first commercial 200-kW systems were being introduced by ONSI and Fuji Electric, the potentially much larger, but also more challenging, application in transportation was beginning to be addressed. As a result, fuel cell-powered buses have been designed and built, and R&D programs for fuel cell-powered passenger cars have been initiated. The engineering challenge of eventually replacing the internal combustion engine in buses, trucks, and passenger cars with fuel cell systems is to achieve much higher power densities and much lower costs than obtainable in systems designed for stationary applications. At present, the leading fuel cell candidate for transportation applications is, without question, the polymer electrolyte fuel cell (PEFC). Offering ambient temperature start-up and the potential for a relatively high power density, the polymer technology has attracted the interest of automotive manufacturers worldwide. But the difficulties of fuel handling for the PEFC have led to a growing interest in exploring the prospects for solid oxide fuel cells (SOFCs) operating on liquid fuels for transportation applications. Solid oxide fuel cells are much more compatible with liquid fuels (methanol or other hydrocarbons) and are potentially capable of power densities high enough for vehicular use. Two SOFC options for such use are discussed in this report.

  12. Enhanced catalyst for conversion of syngas to liquid motor fuels

    DOEpatents

    Coughlin, P.K.; Rabo, J.A.

    1985-12-03

    Synthesis gas comprising carbon monoxide and hydrogen is converted to C[sub 5][sup +] hydrocarbons suitable for use as liquid motor fuels by contact with a dual catalyst system capable of enhancing the selectivity of said conversion to motor fuel range hydrocarbons and the quality of the resulting motor fuel product. The catalyst composition employs a Fischer-Tropsch catalyst, together with a co-catalyst/support component comprising a SAPO silicoaluminophosphate, non-zeolitic molecular sieve catalyst.

  13. Enhanced conversion of syngas to liquid motor fuels

    DOEpatents

    Coughlin, Peter K.; Rabo, Jule A.

    1986-01-01

    Synthesis gas comprising carbon monoxide and hydrogen is converted to C.sub.5.sup.+ hydrocarbons suitable for use as liquid motor fuels by contact with a dual catalyst system capable of enhancing the selectivity of said conversion to motor fuel range hydrocarbons and the quality of the resulting motor fuel product. The catalyst composition employs a Fischer-Tropsch catalyst, together with a co-catalyst/support component comprising SAPO silicoaluminophosphate, non-zeolitic molecular sieve catalyst.

  14. Enhanced catalyst for conversion of syngas to liquid motor fuels

    DOEpatents

    Coughlin, Peter K.; Rabo, Jule A.

    1985-01-01

    Synthesis gas comprising carbon monoxide and hydrogen is converted to C.sub.5.sup.+ hydrocarbons suitable for use as liquid motor fuels by contact with a dual catalyst system capable of enhancing the selectivity of said conversion to motor fuel range hydrocarbons and the quality of the resulting motor fuel product. The catalyst composition employs a Fischer-Tropsch catalyst, together with a co-catalyst/support component comprising SAPO silicoaluminophosphate, non-zeolitic molecular sieve catalyst.

  15. Electronic absorption spectroscopy of PAHs in supersonic jets and ultracold liquid helium droplets

    NASA Astrophysics Data System (ADS)

    Huisken, Friedrich; Staicu, Angela; Krasnokutski, Serge; Henning, Thomas

    Neutral and cationic polycyclic aromatic hydrocarbons (PAHs) are discussed as possible carriers of the diffuse interstellar bands (DIBs), still unassigned astrophysical absorption features observed in the spectra of reddened stars (Salama et al. 1999). Despite the importance of this class of molecules for astrophysics and nanophysics (PAHs can be regarded as nanoscale fragments of a sheet of graphite), the spectroscopic characterization of PAHs under well-defined conditions (low temperature and collision-free environment) has remained a challenge. Recently we have set up a cavity ring-down spectrometer combined with a pulsed supersonic jet expansion to study neutral and cationic PAHs under astrophysical conditions. PAHs studied so far include the neutral molecules anthracene (Staicu et al. 2004) and pyrene (Rouillé et al. 2004) as well as the cationic species naphthalene+ and anthracene+ (Sukhorukov et al. 2004). Employing another molecular beam apparatus, the same molecules (except of the cationic species) were also studied in liquid helium droplets (Krasnokutski et al. 2005, Rouillé et al. 2004). This novel technique combines several advantages of conventional matrix spectroscopy with those of gas phase spectroscopy. Notable advantages are the possibility to study molecules with low vapor pressure and to use a mass spectrometer facilitating spectral assignments. The most recent studies were devoted to phenanthrene and the more complicated (2,3)-benzofluorene. These molecules were investigated in the gas phase by cavity ring-down spectroscopy and in liquid helium droplets using depletion spectroscopy. For benzofluorene the present studies constitute the first reported measurements both in the gas phase and in helium droplets. The origin of the S1 ← S0 gas phase transition could be located at 29 894.3 cm-1, and a series of vibronic bands was recorded below 31 500 cm-1. In contrast to previously studied PAHs, the shift induced by the helium droplets was very

  16. Stable water isotopologue ratios in fog and cloud droplets of liquid clouds are not size-dependent

    USGS Publications Warehouse

    Spiegel, J.K.; Aemisegger, F.; Scholl, M.; Wienhold, F.G.; Collett, J.L.; Lee, T.; van Pinxteren, D.; Mertes, S.; Tilgner, A.; Herrmann, H.; Werner, Roland A.; Buchmann, N.; Eugster, W.

    2012-01-01

    In this work, we present the first observations of stable water isotopologue ratios in cloud droplets of different sizes collected simultaneously. We address the question whether the isotope ratio of droplets in a liquid cloud varies as a function of droplet size. Samples were collected from a ground intercepted cloud (= fog) during the Hill Cap Cloud Thuringia 2010 campaign (HCCT-2010) using a three-stage Caltech Active Strand Cloud water Collector (CASCC). An instrument test revealed that no artificial isotopic fractionation occurs during sample collection with the CASCC. Furthermore, we could experimentally confirm the hypothesis that the δ values of cloud droplets of the relevant droplet sizes (μm-range) were not significantly different and thus can be assumed to be in isotopic equilibrium immediately with the surrounding water vapor. However, during the dissolution period of the cloud, when the supersaturation inside the cloud decreased and the cloud began to clear, differences in isotope ratios of the different droplet sizes tended to be larger. This is likely to result from the cloud's heterogeneity, implying that larger and smaller cloud droplets have been collected at different moments in time, delivering isotope ratios from different collection times.

  17. Coupling liquid chromatography/mass spectrometry detection with microfluidic droplet array for label-free enzyme inhibition assay.

    PubMed

    Wang, Xiu-Li; Zhu, Ying; Fang, Qun

    2014-01-07

    In this work, the combination of droplet-based microfluidics with liquid chromatography/mass spectrometry (LC/MS) was achieved, for providing a fast separation and high-information-content detection method for the analysis of nanoliter-scale droplets with complex compositions. A novel interface method was developed using an oil-covered droplet array chip to couple with an LC/MS system via a capillary sampling probe and a 4 nL injection valve without the need of a droplet extraction device. The present system can perform multistep operations including parallel enzyme inhibition reactions in nanoliter droplets, 4 nL sample injection, fast separation with capillary LC, and label-free detection with ESI-MS, and has significant flexibility in the accurate addressing and sampling of droplets of interest on demand. The system performance was evaluated using angiotensin I and angiotensin II as model samples, and the repeatabilities of peak area for angiotensin I and angiotensin II were 2.7% and 7.5% (RSD, n = 4), respectively. The present system was further applied to the screening for inhibitors of cytochrome P450 (CYP1A2) and measurement of the IC50 value of the inhibitor. The sample consumption for each droplet assay was 100 nL, which is reduced 10-100 times compared with conventional 384-multi-well plate systems usually used in high-throughput drug screening.

  18. Gradient polymer-disposed liquid crystal single layer of large nematic droplets for modulation of laser light.

    PubMed

    Hadjichristov, Georgi B; Marinov, Yordan G; Petrov, Alexander G

    2011-06-01

    The light modulating ability of gradient polymer-disposed liquid crystal (PDLC) single layer of large droplets formed by nematic E7 in UV-cured polymer NOA65 is studied. Operating at relatively low voltages, such PDLC film with a of thickness 10-25 μm and droplet size up to 50 μm exhibits a good contrast ratio and is capable of producing a large phase shift for the propagating coherent light. For a linearly polarized He-Ne laser (λ=633 nm), an electrically commanded phase shift as large as π/2 can be obtained by the large-droplet region of the film. The electrically produced phase shift and its spatial profile controlled by the thickness of the gradient PDLC single layers of large nematic droplets can be useful for tunable spatial light modulators and other devices for active control of laser light.

  19. [Development of a droplet-interfaced high performance liquid chromatography-capillary electrophoresis two dimensional separation platform].

    PubMed

    Ye, Linquan; Wu, Qingshi; Dai, Simin; Xiao, Zhiliang; Zhang, Bo

    2011-09-01

    Proteomics demands high resolution multidimensional separation techniques due to its extremely high complexity. Droplet microfluidics provides a series of unique advantages in manipulating micro and nanolitre samples, such as micro-volume operation, limited diffusion and none cross-contaminating, therefore has the potential to be an ideal interface strategy for multidimensional separation. Using the microchips of different structures, functions such as "droplet generation" and "oil depletion" can be realized. Based on these functions, samples can be transferred from continuous flow to segmented flow and then back to continuous flow. In this way, different separation modes can be combined. In this study, droplet technology was utilized as a novel interface strategy in combining high performance liquid chromatography (HPLC) and capillary electrophoresis (CE). Using tryptic peptides mixture as a sample, this two dimensional HPLC-CE system provided high resolution separation with a peak capacity over 3000. This proof-of-principle study has demonstrated the usefulness of droplet interface technology in multidimensional separation.

  20. Modeling Droplet Motion on Liquid-Infused Surface Using Lattice Boltzmann Method

    NASA Astrophysics Data System (ADS)

    Zhao, Mingfei; Yong, Xin

    2015-11-01

    Understanding self-assembly of nanoparticles driven by the evaporation of the particle-covered sacrificial liquid mass dispensed on a solid substrate is of technological important for various printing and deposition techniques. Although the convective deposition of suspended nanoparticles (known as the coffee ring effect) has been studied extensively, the self-assembly of nanoparticles directly delivered to the liquid-gas interface remains unexplored. In this work, we develop a hybrid model that combines free-energy multiphase LBM with Lagrangian particle tracking method to reveal the complex interplay between nanoparticles, convective flow in liquid, and the dynamics of three-phase contact line on the substrate. We first verify our computational model using existing computational and experimental results. We then investigate the evaporation phenomena of a particle-covered droplet with specified nanoparticle distributions and wetting properties. By controlling the boundary conditions, we can implement desired contact angle hysteresis on the substrate that matches experiment observations. This study provides a theoretical framework to explore the dynamics of nanoparticle self-assembly at evaporating liquid-vapor interfaces.

  1. Dispersive liquid-liquid microextraction based on solidification of floating organic droplets followed by high performance liquid chromatography for the determination of duloxetine in human plasma.

    PubMed

    Suh, Joon Hyuk; Lee, Yun Young; Lee, Hee Joo; Kang, Myunghee; Hur, Yeoun; Lee, Sun Neo; Yang, Dong-Hyug; Han, Sang Beom

    2013-03-05

    A novel dispersive liquid-liquid microextraction method based on solidification of floating organic droplets (DLLME-SFO) technique was developed for the determination of duloxetine in human plasma samples by high performance liquid chromatography with fluorescence detection (HPLC-FLD). During the extraction procedure, plasma protein was precipitated by using a mixture of zinc sulfate solution and acetonitrile. After the protein precipitation step, duloxetine in an alkaline sample solution was quickly extracted by DLLME-SFO with 50 μL of 1-undecanol (extractant). Disperser was unnecessary because the small amount of remaining acetonitrile, which acts as a protein precipitating reagent, was also employed as a disperser; therefore, organic solvent consumption was reduced as much as possible. The emulsion was centrifuged and then fine droplets were floated to the top of the sample solution. The floated droplets were solidified in an ice bath and easily transferred. Various DLLME-SFO parameters such as extractant type, extractant amount, ionic strength, pH and extraction time were optimized. The chromatographic separation of duloxetine was carried out using ethanol as mobile phase. Validation of the method was performed with respect to linearity, intra- and inter-day accuracy and precision, limit of quantification (LOQ), and recovery. Calibration curves for duloxetine showed good linearity with correlation coefficients (r²) higher than 0.99. The method showed good precision and accuracy, with intra- and inter-assay coefficients of variation less than 15% (LOQ: less than 20%) at all concentrations. The recovery was carried out following the standard addition procedure with yields ranging from 59.6 to 65.5%. A newly developed environmentally friendly method was successfully applied to the pharmacokinetic study of duloxetine in human plasma and was shown to be an alternative green approach compared with the conventional solid-phase microextraction (SPME) and dispersive

  2. Ionic Liquid Fuels for Chemical Propulsion

    DTIC Science & Technology

    2014-11-20

    simply by forcing them through a nozzle using backing pressure. One successful way to spray ILs is by using an ultrasonic nozzle , as depicted in...black) and butylimidazole (red), e) DFT IR simulation of methylated TCM-, and f) DFT IR simulation of methylated dca-. Ultrasonic spray approach to...Figure 3a. The IL and the oxidizer droplet sizes, relative collision velocities and other parameters will be probed. The ultrasonic Distribution A

  3. Alternative Liquid Fuels Simulation Model (AltSim).

    SciTech Connect

    Baker, Arnold Barry; Williams, Ryan; Drennen, Thomas E.; Klotz, Richard

    2007-10-01

    The Alternative Liquid Fuels Simulation Model (AltSim) is a high-level dynamic simulation model which calculates and compares the production costs, carbon dioxide emissions, and energy balances of several alternative liquid transportation fuels. These fuels include: corn ethanol, cellulosic ethanol, biodiesel, and diesels derived from natural gas (gas to liquid, or GTL) and coal (coal to liquid, or CTL). AltSim allows for comprehensive sensitivity analyses on capital costs, operation and maintenance costs, renewable and fossil fuel feedstock costs, feedstock conversion efficiency, financial assumptions, tax credits, CO{sub 2} taxes, and plant capacity factor. This paper summarizes the preliminary results from the model. For the base cases, CTL and cellulosic ethanol are the least cost fuel options, at $1.60 and $1.71 per gallon, respectively. Base case assumptions do not include tax or other credits. This compares to a $2.35/gallon production cost of gasoline at September, 2007 crude oil prices ($80.57/barrel). On an energy content basis, the CTL is the low cost alternative, at $12.90/MMBtu, compared to $22.47/MMBtu for cellulosic ethanol. In terms of carbon dioxide emissions, a typical vehicle fueled with cellulosic ethanol will release 0.48 tons CO{sub 2} per year, compared to 13.23 tons per year for coal to liquid.

  4. Rethinking biological activation of methane and conversion to liquid fuels.

    PubMed

    Haynes, Chad A; Gonzalez, Ramon

    2014-05-01

    If methane, the main component of natural gas, can be efficiently converted to liquid fuels, world reserves of methane could satisfy the demand for transportation fuels in addition to use in other sectors. However, the direct activation of strong C-H bonds in methane and conversion to desired products remains a difficult technological challenge. This perspective reveals an opportunity to rethink the logic of biological methane activation and conversion to liquid fuels. We formulate a vision for a new foundation for methane bioconversion and suggest paths to develop technologies for the production of liquid transportation fuels from methane at high carbon yield and high energy efficiency and with low CO2 emissions. These technologies could support natural gas bioconversion facilities with a low capital cost and at small scales, which in turn could monetize the use of natural gas resources that are frequently flared, vented or emitted.

  5. Effect of liquid droplets on turbulence in a round gaseous jet

    NASA Technical Reports Server (NTRS)

    Mostafa, A. A.; Elghobashi, S. E.

    1986-01-01

    The main objective of this investigation is to develop a two-equation turbulence model for dilute vaporizing sprays or in general for dispersed two-phase flows including the effects of phase changes. The model that accounts for the interaction between the two phases is based on rigorously derived equations for turbulence kinetic energy (K) and its dissipation rate epsilon of the carrier phase using the momentum equation of that phase. Closure is achieved by modeling the turbulent correlations, up to third order, in the equations of the mean motion, concentration of the vapor in the carrier phase, and the kinetic energy of turbulence and its dissipation rate for the carrier phase. The governing equations are presented in both the exact and the modeled formes. The governing equations are solved numerically using a finite-difference procedure to test the presented model for the flow of a turbulent axisymmetric gaseous jet laden with either evaporating liquid droplets or solid particles. The predictions include the distribution of the mean velocity, volume fractions of the different phases, concentration of the evaporated material in the carrier phase, turbulence intensity and shear stress of the carrier phase, droplet diameter distribution, and the jet spreading rate. The predictions are in good agreement with the experimental data.

  6. Drying, phase separation, and deposition in droplets of sunset yellow chromonic liquid crystal

    NASA Astrophysics Data System (ADS)

    Gross, Adam; Davidson, Zoey S.; Huang, Yongyang; Still, Tim; Zhou, Chao; Yodh, A. G.

    We investigate the drying process and the final deposition patterns of multi-phase sessile droplets containing aqueous lyotropic chromonic liquid crystal (LC). The experiments employ a variety of optical techniques including profilometry, polarization optical microscopy and optical coherence microscopy. An unusual hierarchical LC assembly is observed during drying; in particular, LC mesogens are first formed at the start of drying and then compartments of isotropic, nematic and columnar phases arise. Nonuniform evaporation creates concentration gradients in droplets such that LC phases emerge from the outer edge of the drop and advance to the center over the course of drying. Distinct outward flows associated with the ``coffee-ring effect'' are seen initially, but the assembly of the mesogens creates viscosity, density, and surface tension gradients that effectively introduce new convective flows and complex LC phase boundaries within the drop. Finally, we show that the final deposit shape of chromonic materials changes with rate of evaporation. We gratefully acknowledge financial support through NSF DMR12-05463, MRSEC DMR11-20901, NASA NNX08AO0G, and NSF DBI-1455613.

  7. Measurement of the Mean Droplet Size in Horizontal, Isothermal Air--Water and Air--Viscous Liquid Free Jets in Quiescent Ambient

    NASA Astrophysics Data System (ADS)

    Al-Rabadi, S.; Al-Salaymeh, A.; Friedel, L.

    2005-11-01

    In a free jet where higher turbulence intensity than that of the ambient exists, the liquid phase fragmentation enhanced by aerodynamic forces that are associated with the co-flowed and entrained air is pronounced. Measurements using 2-D PDA as well as high-speed cinematography of air--water and air--viscous liquid in free jets at several nozzle exit pressures and nozzle outlet diameters have been conducted. It became evident that the mean droplet size decreases with increasing air--liquid phase mass flow ratio due to the increase of the shearing on the liquid phase. This leads to substantial liquid fragmentation (primary breakup) and, subsequently, to the formation of satellite droplets with small sizes. This trend becomes significant with increasing liquid viscosity. Higher liquid viscosity than that of water affects the droplet formation and breakup by reducing the rates of surface perturbations and consequently droplet distortions. The droplet velocity decreases with the downstream distance due to the continued air entrainment. The kinetic energy of the droplets is mostly dissipated during the collisions, which may induce further liquid fragmentation and hence formation of a number of relatively smaller droplets (secondary breakup), or the formation of comparatively larger liquid fragments that may rain out the free jet.

  8. Periodic emission of droplets from an oscillating electrified meniscus of a low-viscosity, highly conductive liquid

    NASA Astrophysics Data System (ADS)

    Hijano, A. J.; Loscertales, I. G.; Ibáñez, S. E.; Higuera, F. J.

    2015-01-01

    The generation of identical droplets of controllable size in the micrometer range is a problem of much interest owing to the numerous technological applications of such droplets. This work reports an investigation of the regime of periodic emission of droplets from an electrified oscillating meniscus of a liquid of low viscosity and high electrical conductivity attached to the end of a capillary tube, which may be used to produce droplets more than ten times smaller than the diameter of the tube. To attain this periodic microdripping regime, termed axial spray mode II by Juraschek and Röllgen [R. Juraschek and F. W. Röllgen, Int. J. Mass Spectrom. 177, 1 (1998), 10.1016/S1387-3806(98)14025-3], liquid is continuously supplied through the tube at a given constant flow rate, while a dc voltage is applied between the tube and a nearby counter electrode. The resulting electric field induces a stress at the surface of the liquid that stretches the meniscus until, in certain ranges of voltage and flow rate, it develops a ligament that eventually detaches, forming a single droplet, in a process that repeats itself periodically. While it is being stretched, the ligament develops a conical tip that emits ultrafine droplets, but the total mass emitted is practically contained in the main droplet. In the parametrical domain studied, we find that the process depends on two main dimensionless parameters, the flow rate nondimensionalized with the diameter of the tube and the capillary time, q , and the electric Bond number BE, which is a nondimensional measure of the square of the applied voltage. The meniscus oscillation frequency made nondimensional with the capillary time, f , is of order unity for very small flow rates and tends to decrease as the inverse of the square root of q for larger values of this parameter. The product of the meniscus mean volume times the oscillation frequency is nearly constant. The characteristic length and width of the liquid ligament

  9. Converting solar energy into liquid fuels

    SciTech Connect

    Reeser, L.G. ); Acra, A.P.L. ); Lee, T. )

    1995-01-01

    As projections indicate, our energy needs will exceed our estimates of finite reserves of fossil fuels. It becomes imperative that we develop programs to produce fuel from renewable resources. Brazil's program demonstrates how today's technologies can be used to integrate farming systems, reduce dependence on imported oil and improve the environment. This paper presents the highlights of this program. 6 tabs.

  10. Electrowetting on liquid-infused film (EWOLF): Complete reversibility and controlled droplet oscillation suppression for fast optical imaging

    PubMed Central

    Hao, Chonglei; Liu, Yahua; Chen, Xuemei; He, Yuncheng; Li, Qiusheng; Li, K. Y.; Wang, Zuankai

    2014-01-01

    Electrowetting on dielectric (EWOD) has emerged as a powerful tool to electrically manipulate tiny individual droplets in a controlled manner. Despite tremendous progress over the past two decades, current EWOD operating in ambient conditions has limited functionalities posing challenges for its applications, including electronic display, energy generation, and microfluidic systems. Here, we demonstrate a new paradigm of electrowetting on liquid-infused film (EWOLF) that allows for complete reversibility and tunable transient response simultaneously. We determine that these functionalities in EWOLF are attributed to its novel configuration, which allows for the formation of viscous liquid-liquid interfaces as well as additional wetting ridges, thereby suppressing the contact line pinning and severe droplet oscillation encountered in the conventional EWOD. Finally, by harnessing these functionalities demonstrated in EWOLF, we also explore its application as liquid lens for fast optical focusing. PMID:25355005

  11. Numerical analysis of natural convection in liquid droplets by phase change

    NASA Technical Reports Server (NTRS)

    Duh, J. C.; Yang, Wen-Jei

    1989-01-01

    A numerical analysis is performed on thermocapillary buoyancy convection induced by phase change in a liquid droplet. A finite-difference code is developed using an alternating-direction implicit (ADI) scheme. The intercoupling relation between thermocapillary force, buoyancy force, fluid property, heat transfer, and phase change, along with their effects on the induced flow patterns, are disclosed. The flow is classified into three types: thermocapillary, buoyancy, and combined convection. Among the three mechanisms, the combined convection simulates the experimental observations quite well, and the basic mechanism of the observed convection inside evaporating sessile drops is thus identified. It is disclosed that evaporation initiates unstable convection, while condensation always brings about a stable density distribution which eventually damps out all fluid disturbances. Another numerical model is presented to study the effect of boundary recession due to evaporation, and the 'peeling-off' effect (the removal of the surface layer of fluid by evaporation) is shown to be relevant.

  12. Jumping liquid metal droplet in electrolyte triggered by solid metal particles

    NASA Astrophysics Data System (ADS)

    Tang, Jianbo; Wang, Junjie; Liu, Jing; Zhou, Yuan

    2016-05-01

    We report the electron discharge effect due to point contact between liquid metal and solid metal particles in electrolyte. Adding nickel particles induces drastic hydrogen generating and intermittent jumping of a sub-millimeter EGaIn droplet in NaOH solution. Observations from different orientations disclose that such jumping behavior is triggered by pressurized bubbles under the assistance of interfacial interactions. Hydrogen evolution around particles provides clear evidence that such electric instability originates from the varied electric potential and morphology between the two metallic materials. The point-contact-induced charge concentration significantly enhances the near-surface electric field intensity at the particle tips and thus causes electric breakdown of the electrolyte.

  13. USC/AIAA student get away special project liquid droplet collector experiment

    NASA Technical Reports Server (NTRS)

    Levesque, Raymond J., II

    1987-01-01

    This experimental payload was developed in order to observe, in a micro-gravity vacuum environment, the characteristics and stability of a thin fluid film flowing across a slightly curved surface. The test apparatus was designed based upon various ground-based thin film investigations, combined with the constraints imposed by the rigors of launch and the space environment. Testing of the fluid test article at atmospheric pressure and in vacuum verified the design provisions employed concerning ultra-low inlet pressure pump construction, as well as confirming expected pressure losses in the system. During the course of hardware development and construction modifications were required; however, the overall payload configuration remained largely unchanged. This will allow for modification and reflight of the apparatus based upon the findings of the initial flight. The specific applications of this experiment include Liquid Droplet Radiator development and various forms of material transport in vacuum.

  14. Simulation of a liquid droplet ejection device using multi-actuator

    NASA Astrophysics Data System (ADS)

    Ono, Yoshihiro; Yoshino, Michitaka; Yasuda, Akira; Tanuma, Chiaki

    2016-07-01

    An equivalent circuit model for a liquid droplet ejection device using a multiactuator has been developed. The equivalent circuit was simplified using a gyrator in the synthesis of the outputs of many elements. The simulation was performed for an inkjet head having three piezoelectric elements using MATLAB/Simulink. In this model, the pressure chamber is filled with a Newtonian fluid. For this reason, the model assumed only the resistance component of the pressure chamber and the nozzle as a load. Furthermore, since the resistance component of the inlet is much larger than that of the nozzle, it is not considered in this model. As a result, by providing a time difference between the driving signals of the piezoelectric elements, we found that the pressure of the ink chamber could be arbitrarily controlled. By this model, it becomes possible to control the pressure in the ink chamber of the inkjet head required for the ejection of various inks.

  15. Jumping liquid metal droplet in electrolyte triggered by solid metal particles

    SciTech Connect

    Tang, Jianbo; Wang, Junjie; Liu, Jing E-mail: zhouyuan@mail.ipc.ac.cn; Zhou, Yuan E-mail: zhouyuan@mail.ipc.ac.cn

    2016-05-30

    We report the electron discharge effect due to point contact between liquid metal and solid metal particles in electrolyte. Adding nickel particles induces drastic hydrogen generating and intermittent jumping of a sub-millimeter EGaIn droplet in NaOH solution. Observations from different orientations disclose that such jumping behavior is triggered by pressurized bubbles under the assistance of interfacial interactions. Hydrogen evolution around particles provides clear evidence that such electric instability originates from the varied electric potential and morphology between the two metallic materials. The point-contact-induced charge concentration significantly enhances the near-surface electric field intensity at the particle tips and thus causes electric breakdown of the electrolyte.

  16. Ripples on a rising bubble through an immiscible two-liquid interface generate numerous micro droplets

    NASA Astrophysics Data System (ADS)

    Uemura, T.; Ueda, Y.; Iguchi, M.

    2010-11-01

    The mass transfer between immiscible two liquid phases can be greatly accelerated by bubbling gas through a reactor (Bird R. B., Stewart W. E. and Lightfoot E. N., Transport Phenomena, 2nd edition (John Wiley and Sons) 2002). Therefore, the physical phenomenon occurring during the passage of a rising bubble through an immiscible two-liquid interface is of particular interest. The passage of the bubble through the oil (upper phase)/water (lower phase) interface starts with an upward lifting of the interface, and the bubble attracts a column of the water phase upwards keeping a film of the water phase around itself. In the present study, a particular remark is given to the influence of different interface tensions retracting the water film, after the water film ruptured, which lays on the interface between air and silicone oil. Unlike the previous studies on the rupture of a single liquid film in a gas which is pulled due to the identical surface tension, this system can form concentric ripples on the outer interface of the water film (oil/water interface) around the bubble due to the weak interface tension. Then, numerous micro water droplets break out from the fully grown ripples.

  17. Sealed canister liquid sampling for fuel characterization shipments

    SciTech Connect

    Trimble, D.J.

    1995-01-12

    N-Reactor spent fuel elements will be removed from the sealed fuel storage canisters in the KW Basin and shipped to the 300 Area hot cells for characterization studies. Some of the canisters contain broken fuel elements exposing metallic uranium to the canister water. The exposed uranium surfaces have reacted with the water releasing fission product nuclides to the canister water. The extent of this release is unknown, but large radionuclide inventories could cause significant releases to the basin water. To avoid this, a method is needed to evaluate the magnitude of the canister water radioactivity to help make decisions about which canisters should not be opened for fuel sampling. The objective of this document is to provide a conceptual description of the process for obtaining and evaluating gas and liquid samples from KW fuel canisters in support of fuel characterization shipments. Also described are the decisions regarding the acceptability of a sample, the actions to be taken to obtain an acceptable sample, and the logical leading to decisions about opening canisters for fuel characterization sampling. This document will help guide a safety analysis of the liquid sampling process and the development of detailed procedures for the process. Outside the scope of this document are the processes for opening canisters, selecting fuel samples from opened canisters, shipping fuel samples, and closing canisters.

  18. Japan's research on droplet and droplet array combustion

    NASA Technical Reports Server (NTRS)

    Kono, Michikata

    1995-01-01

    In Japan, the ignition and combustion of the droplet and droplet array have been investigated by using microgravity condition. This is the short introduction of those studies; interactive combustion of two droplets, ignition experiment on droplet array, and microexplosion behavior of an emulsified fuel droplet.

  19. Soot formation during combustion of unsupported methanol/toluene mixture droplets in microgravity

    NASA Technical Reports Server (NTRS)

    Jackson, G. S.; Avedisian, C. T.; Yang, J. C.

    1991-01-01

    Results are reported of an experimental study tracing the influence of liquid composition on soot formation and the burning rate of a droplet composed of a binary miscible mixture of liquids. The mixture components represented a highly sooting fuel, toluene, and a nonsooting fuel, methanol. The toluene concentration in methanol was shown to dramatically influence flame luminosity and soot production. Neither burning rates nor a propensity for flame extinction appeared to be significantly affected by toluene mixture fractions. Five-percent toluene mixture droplets behaved like pure methanol droplets in terms of burning rate, lack of flame luminosity, and extinction. Increasing the toluene concentration in the droplets to 25 percent increased flame luminosity, yet no visible soot agglomerates were observed. The 50-percent-mixture droplets burned with highly luminous flames and large amounts of soot agglomerates collecting inside the flame. All the mixture droplets showed burning rates similar to those of pure methanol and likewise exhibited flame extinction before complete droplet vaporization.

  20. Droplet Suspended on a Wire Begins Ignition

    NASA Technical Reports Server (NTRS)

    2003-01-01

    The Fiber Supported Droplet Combustion Experiment completing a number of successful burns on STS-94, July 11, 1997, MET:9/17:40 (approximate). The photo shows a droplet of 95% heptane and 5% hexadecane, suspended and positioned by the fiber wire, just as it is being ignited by the glowing coil beneath. Study of the physical properties of burning fuel from this experiment is expected to contribute to more efficient use of fossil fuels and reduction of combustion by-products on Earth. The sequence is from a time-lapse movie (34 seconds condensed to 12 seconds), and clearly shows particles emanating from the droplet during the burn. The droplet shrank to nothing as it was consumed. FSDC-2 studied fundamental phenomena related to liquid fuel droplet combustion in air. Pure fuels and mixtures of fuels were burned as isolated single and dual droplets with and without forced air convection. The FSDC guest investigator was Forman Williams, University of California, San Diego. The experiment was part of the space research investigations conducted during the Microgravity Science Laboratory-1R mission (STS-94, July 1-17 1997). Advanced combustion experiments will be a part of investigations plarned for the International Space Station. (1.2 MB, 11-second MPEG, screen 320 x 240 pixels; downlinked video, higher quality not available) A still JPG composite of this movie is available at http://mix.msfc.nasa.gov/ABSTRACTS/MSFC-0300180.html.