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Sample records for evaporating fuel sprays

  1. Accurate analysis of multicomponent fuel spray evaporation in turbulent flow

    NASA Astrophysics Data System (ADS)

    Rauch, Bastian; Calabria, Raffaela; Chiariello, Fabio; Le Clercq, Patrick; Massoli, Patrizio; Rachner, Michael

    2012-04-01

    The aim of this paper is to perform an accurate analysis of the evaporation of single component and binary mixture fuels sprays in a hot weakly turbulent pipe flow by means of experimental measurement and numerical simulation. This gives a deeper insight into the relationship between fuel composition and spray evaporation. The turbulence intensity in the test section is equal to 10%, and the integral length scale is three orders of magnitude larger than the droplet size while the turbulence microscale (Kolmogorov scales) is of same order as the droplet diameter. The spray produced by means of a calibrated droplet generator was injected in a gas flow electrically preheated. N-nonane, isopropanol, and their mixtures were used in the tests. The generalized scattering imaging technique was applied to simultaneously determine size, velocity, and spatial location of the droplets carried by the turbulent flow in the quartz tube. The spray evaporation was computed using a Lagrangian particle solver coupled to a gas-phase solver. Computations of spray mean diameter and droplet size distributions at different locations along the pipe compare very favorably with the measurement results. This combined research tool enabled further investigation concerning the influencing parameters upon the evaporation process such as the turbulence, droplet internal mixing, and liquid-phase thermophysical properties.

  2. Convective Evaporation Of Sprayed Liquid

    NASA Technical Reports Server (NTRS)

    Bellan, Josette; Harstad, Kenneth G.

    1987-01-01

    Theoretical model developed to analyze behavior of both dense and dilute clusters of evaporating liquid drops in gas flows. Particularly useful in search for methods of controlling evaporation, ignition, and combustion of fuel sprays.

  3. 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.

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

    PubMed

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

    2016-03-15

    This Letter demonstrates the application of filtered Rayleigh scattering (FRS) for quantitative two-dimensional fuel vapor/air mixing measurements in an evaporating hydrocarbon fuel spray flow. Using the FRS approach, gas-phase measurements are made in the presence of liquid-phase droplets without interference. Effective suppression of the liquid-phase droplet scattering using FRS is enabled by the high spectral purity of the current Nd:YAG laser system. Simultaneous Mie-scattering imaging is used to visualize the droplet field and illustrate the droplet loading under which the FRS imaging is applied in the current spray flows. The initial quantification of the FRS imaging is based on calibration measurements from a flow cell of known fuel vapor/air mixtures, while future work targets the utilization of a Rayleigh-Brillouin spectral model for quantification of the FRS signals. PMID:26977637

  5. Dense spray evaporation as a mixing process

    NASA Astrophysics Data System (ADS)

    de Rivas, A.; Villermaux, E.

    2016-05-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2013-06-01

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

  7. 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.

  8. The lifetime of evaporating dense sprays

    NASA Astrophysics Data System (ADS)

    de Rivas, Alois; Villermaux, Emmanuel

    2015-11-01

    We study the processes by which a set of nearby liquid droplets (a spray) evaporates in a gas phase whose relative humidity (vapor concentration) is controlled at will. A dense spray of micron-sized water droplets is formed in air by a pneumatic atomizer and conveyed through a nozzle in a closed chamber whose vapor concentration has been pre-set to a controlled value. The resulting plume extension depends on the relative humidity of the diluting medium. When the spray plume is straight and laminar, droplets evaporate at its edge where the vapor is saturated, and diffuses through a boundary layer developing around the plume. We quantify the shape and length of the plume as a function of the injecting, vapor diffusion, thermodynamic and environment parameters. For higher injection Reynolds numbers, standard shear instabilities distort the plume into stretched lamellae, thus enhancing the diffusion of vapor from their boundary towards the diluting medium. These lamellae vanish in a finite time depending on the intensity of the stretching, and relative humidity of the environment, with a lifetime diverging close to the equilibrium limit, when the plume develops in an medium saturated in vapor. The dependences are described quantitatively.

  9. Statistical Model of Evaporating Multicomponent Fuel Drops

    NASA Technical Reports Server (NTRS)

    Harstad, Kenneth; LeClercq, Patrick; Bellan, Josette

    2007-01-01

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

  10. Modeling of gas turbine fuel nozzle spray

    SciTech Connect

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

    1997-01-01

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

  11. Evaporating Spray in Supersonic Streams Including Turbulence Effects

    NASA Technical Reports Server (NTRS)

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

    2006-01-01

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

  12. Simulations of Evaporating Multicomponent Fuel Drops

    NASA Technical Reports Server (NTRS)

    Bellan, Josette; Le Clercq, Patrick

    2005-01-01

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

  13. Fuel spray diagnostics

    NASA Technical Reports Server (NTRS)

    Bosque, M. A.

    1984-01-01

    Several laser measurement methods are being studied to provide the capability to make droplet size and velocity measurements under a variety of spray conditions. The droplet sizing interferometer (DSI) promises to be a successful technique because of its capability for rapid data acquisition, compilation and analysis. Its main advantage is the ability to obtain size and velocity measurements in air-fuel mixing studies and hot flows. The existing DSI at NASA Lewis is a two-color, two-component system. Two independent orthogonal measurements of size and velocity components can be made simultaneously. It also uses an off-axis large-angle light scatter detection. The fundamental features of the system are optics, signal processing and data management system. The major component includes a transmitter unit, two receiver units, two signal processors, two data management systems, two Bragg cell systems, two printer/plotters, a laser, power supply and color monitor.

  14. Photomicrographic Studies of Fuel Sprays

    NASA Technical Reports Server (NTRS)

    Lee, Dana W; Spencer, Robert C

    1934-01-01

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

  15. Pollutant Formation in Monodisperse Fuel Spray Combustion

    NASA Technical Reports Server (NTRS)

    Cernansky, N. P.; Sarv, H.

    1983-01-01

    The combustion of liquid sprays represents an extremely important class of combustion processes. In the transition region, encompassing droplet sizes in the range of 25-80 micron diameter, the mixing and evaporation processes are both incomplete at the flame front and burning occurs in a combined diffusive and premixed fashion. Under these conditions, the relative importance of heterogeneous and homogeneous effects in dominating the combustion process is switched and gives rise to a number of interesting phenomena. NO (sub x) formation in monodisperse spray combustion was investigated with the following specific objectives: (1) to quantitatively determine the effect of droplet size, number density, etc. on NO sub x formation in monodisperse fuel spray combustion; and (2) to isolate the important physical and chemical phenomena in NO sub x formation in these combustion systems.

  16. Detailed fuel spray analysis techniques

    NASA Technical Reports Server (NTRS)

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

    1983-01-01

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

  17. Evaluation of a locally homogeneous model of spray evaporation

    NASA Technical Reports Server (NTRS)

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

    1979-01-01

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

  18. A study of diamond laminated surfaces in evaporative spray cooling

    NASA Astrophysics Data System (ADS)

    Sehmbey, M. S.; Pais, M. R.; Chow, L. C.

    This effort is directed towards studying the performance of diamond laminated surfaces under conditions of evaporative spray cooling of high-heat-flux electronic components. The experimental results presented illustrate the robustness of the surface, as well as its heat transfer characteristics, wettability and roughness. Exceptional heat flux rates of over 1100 W/sq cm were obtained within superheats of 40 C.

  19. Evaporative spray cooling of plain and microporous coated surfaces.

    SciTech Connect

    Kim, J. H.; You, S. M.; Choi, S. U.-S.; Energy Technology; Univ. of Texas at Arlington

    2004-07-01

    Experiments were performed on air and evaporative spray cooling of plain and microporous coated surfaces on flat and cylindrical heaters. Micron-size aluminum particles were used to build the microporous structures on the heated surfaces. To analyze the evaporative cooling, heat transfer curves were obtained in the form of the wall temperature difference versus heat flux. The heat transfer coefficients were also determined as a function of heat flux. Three water flow rates (1.25, 1.75 and 2.40 ml/min) were tested for the flat heater and one rate (3.0 ml/min) for the cylindrical heater, maintaining the air pressure of 7 psig (48 kPa) at the inlet of the nozzle. The effect of different particle sizes in the coating was also tested to optimize the microporous coating technique. Spraying water droplets on the microporous coating surface enhanced the heat removal due to the capillary pumping phenomenon through the microporous cavities connecting each other. The evaporative spray cooling increased the heat transfer coefficient by up to 400% relative to that of the uncoated surface cooled by dry air, and this enhancement was maintained at high heat fluxes by using microporous surfaces.

  20. Evaluation of a locally homogeneous model of spray evaporation

    NASA Technical Reports Server (NTRS)

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

    1978-01-01

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

  1. Effects of sea spray evaporation and dissipative heating on intensity and structure of tropical cyclone

    NASA Astrophysics Data System (ADS)

    Cheng, Xiaoping; Fei, Jianfang; Huang, Xiaogang; Zheng, Jing

    2012-07-01

    To examine effects of sea spray evaporation and dissipative heating on structure and intensity of a real tropical cyclone, the sea spray flux parameterization scheme was incorporated into the fifth-generation Pennsylvania State University-National Center for Atmospheric Research Mesoscale Model (MM5). Sensitivity tests were performed with varying the spray source function intensities and with and without dissipation heating. The numerical results indicate that sea spray evaporation increases the interfacial sensible heat flux, which is increased by 16% for the moderate spray and 47% for the heavy spray, but has little effect on the interfacial latent heat flux. The net effect of sea spray evaporation is to decrease the total sensible heat flux and to increase the total latent heat flux. The total enthalpy flux is increased by 1% and 12% with moderate and strong spray amounts, respectively. Consistent with these results, the intensity of the tropical cyclone is increased by 5% and 16% in maximum 10-m wind speed, respectively, due to sea spray evaporation. Sea spray evaporation and dissipative heating modify the tropical cyclone structure in important but complex ways. The effect of sea spray on the near-surface temperature and moisture depends on the spray amounts and its location within the tropical cyclone. Within the high-wind region of a tropical cyclone, the lower atmosphere becomes cooler and moister due to the evaporation of sea spray. However, the dissipative heating offsets the cooling due to sea spray evaporation, which makes the lower atmosphere warmer.

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

    SciTech Connect

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

    2006-09-15

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

  3. Experiments on the Distribution of Fuel in Fuel Sprays

    NASA Technical Reports Server (NTRS)

    Lee, Dana W

    1932-01-01

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

  4. CFD Modeling of Superheated Fuel Sprays

    NASA Technical Reports Server (NTRS)

    Raju, M. S.

    2008-01-01

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

  5. Fuel thermal stability effects on spray characteristics

    NASA Technical Reports Server (NTRS)

    Lefebvre, A. H.; Nickolaus, D.

    1987-01-01

    The propensity of a heated hydrocarbon fuel toward solids deposition within a fuel injector is investigated experimentally. Fuel is arranged to flow through the injector at constant temperature, pressure, and flow rate and the pressure drop across the nozzle is monitored to provide an indication of the amount of deposition. After deposits have formed, the nozzle is removed from the test rig and its spray performance is compared with its performance before deposition. The spray characteristics measured include mean drop size, drop-size distribution, and radial and circumferential fuel distribution. It is found that small amounts of deposition can produce severe distortion of the fuel spray pattern. More extensive deposition restores spray uniformity, but the nozzle flow rate is seriously curtailed.

  6. Droplet-turbulence interactions in subcritical and supercritical evaporating sprays

    NASA Technical Reports Server (NTRS)

    Santavicca, Domenic A.; Coy, Edward; Greenfield, Stuart; Song, Young-Hoon

    1991-01-01

    The objective of this research is to obtain an improved understanding of droplet turbulence interactions in vaporizing liquid sprays under conditions typical of those encountered in liquid fueled rocket engines. The interaction between liquid droplets and the surrounding turbulent gas flow affects droplet dispersion, droplet collisions, droplet vaporization and gas-phase, fuel-oxidant mixing, and therefore has a significant effect on the engine's combustion characteristics. An example of this is the role which droplet-turbulence interactions are believed to play in combustion instabilities. Despite their importance, droplet-turbulence interactions and their effect on liquid fueled rocket engine performance are not well understood. This is particularly true under supercritical conditions, where many conventional concepts, such as surface tension, no longer apply. Our limited understanding of droplet-turbulence interactions, under both subcritical conditions, represents a major limitation in our ability to design improved liquid previously unavailable information and valuable new insights which will directly impact the design of future liquid fueled rocket engines, as well as, allow for the development of significantly improved spray combustion models, making such models useful design tools.

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

    NASA Technical Reports Server (NTRS)

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

    1984-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    1984-07-01

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

  9. A theoretical and experimental study of turbulent evaporating sprays

    NASA Technical Reports Server (NTRS)

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

    1984-01-01

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

  10. Preliminary Photomicrographic Studies of Fuel Sprays

    NASA Technical Reports Server (NTRS)

    Lee, Dana W; Spencer, Robert C

    1932-01-01

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

  11. Evaporation and Combustion Characteristics of Multicomponent Fuels

    NASA Astrophysics Data System (ADS)

    Govindaraju, Pavan; Stagni, Alessandro; Ihme, Matthias

    2015-11-01

    Current generation fuels are mixtures of hundreds of complicated organic compounds and accurate modeling of their combustion characteristics provides fundamental physical insights which also help in the design of efficient combustors. This however requires accurate simulation of both evaporation and combustion processes, which, in case of such fuels, demands an approach based on calculating properties using only the information of functional groups present in the mixture. The presentation will elaborate on the assumptions and the framework utilized for evaporation and chemical mechanisms. We also present a comparison between various fuels used in the aviation industry as test cases while highlighting on their pros and cons. The focus of the talk will however be on the physical aspects captured using 1D simulations, i.e., preferential evaporation of each species, ignition parameters and emissions while justifying the numerical calculations with experimental data at each stage. Further work involving the coupling of flow with evaporation and combustion can be performed and we briefly discuss why a DNS is necessary to characterize the various combustion regimes. Federal Aviation Administration.

  12. The evaporation of dense sprays as a mixing process

    NASA Astrophysics Data System (ADS)

    de Rivas, Alois; Villermaux, Emmanuel

    2014-11-01

    A dense spray of micron-sized droplets (water or ethanol) is formed in air by a pneumatic atomizer in a closed chamber, and is then conveyed through a nozzle in ambient air, forming a plume whose extension depends on the relative humidity of the diluting medium. We focus on the dry ambient medium, and large plume Reynolds number limit. Standard shear instabilities develop at the plume edge, forming the stretched lamellar structures familiar with passive scalars, except that these vanish in a finite time, because individual droplets evaporate at their border. Experiments also demonstrate that the lifetime of an individual droplet embedded in a lamellae is much larger than expected from the usual d-square law for an isolated droplet. By analogy with the way mixing times are understood from the convection-diffusion equation for passive scalars, we show that the lifetime of a lamellae stretched at a rate γ is tv =1/γ ln (1/+ ϕ ϕ ) where ϕ is a parameter which incorporates the thermodynamic and diffusional properties of the vapor in the diluting phase. The droplets field thus behaves as a -non conserved- passive scalar.

  13. Measurements in liquid fuel sprays

    NASA Technical Reports Server (NTRS)

    Chigier, N.; Mao, C. P.

    1985-01-01

    A ground test facility is being established at NASA Lewis Research Center to simulate the environmental and flight conditions needed to study adverse weather effects. One of the most important components is the water spray system which consists of many nozzles fitted on spray bars. Water is injected through air-assisted atomizers to generate uniform size drops to simulate icing in clouds. The primary objective is to provide experimental data on drop size distribution over a wide range of operating conditions. Correlation equations for mean drop size and initial injection parameters are being determined to assist in the design and modification of the Altitude Wind Tunnel. Special emphasis is being placed on the study of the aerodynamic structure of the air-assisted atomizer sprays. Detailed measurements of the variation of drop size distribution and velocity as a function of time and space are being made. Accurate initial and boundary conditions are being provided for computer model evaluation.

  14. Influence of Spray Formulation and Leaf Surface Structure on Droplet Evaporation and Wetted Area

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The fate of pesticide droplets on leaves is seriously influenced by spray formulations and fine structures on leaf surfaces. Evaporation times and wetted areas of droplets on hairy and waxy geranium leaf surfaces were determined under controlled conditions. Droplet evaporation processes were taken w...

  15. Analysis of polydisperse fuel spray flame

    NASA Astrophysics Data System (ADS)

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

    2016-06-01

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

  16. A tabulated chemistry approach for numerical modeling of diesel spray evaporation in a 'stabilized cool flame' environment

    SciTech Connect

    Kolaitis, D.I.; Founti, M.A.

    2006-04-15

    Droplet evaporation in a 'stabilized cool flame' environment leads to a homogeneous, heated air-fuel vapor mixture that can be subsequently either burnt or utilized in fuel-reforming applications for fuel cell systems. The paper investigates the locally occurring physico-chemical phenomena in an atmospheric pressure, diesel spray, stabilized cool flame reactor, utilizing a tabulated chemistry approach in conjunction with a two-phase, Eulerian-Lagrangian computational fluid dynamics code. Actual diesel oil physical properties are used to model spray evaporation in the two-phase simulations, whereas the corresponding chemistry is represented by n-heptane. A lookup table is constructed by performing a plethora of perfectly stirred reactor simulations, utilizing a semidetailed n-heptane oxidation chemical kinetics mechanism. The overall exothermicity of the preignition n-heptane oxidation chemistry and the fuel consumption rates are examined as a function of selected independent parameters, namely temperature, fuel concentration, and residence time; their influence on cool flame reactivity is thoroughly studied. It is shown that the tabulated chemistry approach allows accurate investigation of the chemical phenomena with low computational cost. The two-phase flow inside the stabilized cool flame reactor is simulated, utilizing the developed lookup table. Predictions are presented for a variety of test cases and are compared to available experimental data, with satisfactory agreement. Model validation tests indicate that prediction quality improves with increasing values of air temperature at the reactor's inlet. (author)

  17. Effect of Pre-evaporation on Flame Spread Limit of a Fuel Droplet Array

    NASA Astrophysics Data System (ADS)

    Yamamoto, Shin; Kikuchi, Masao; Suematsu, Takaaki; Yoda, Shinichi; Mikami, Masoto

    Spray combustion is utilized in various fields such as gas turbine and aero-engine. Combustion exhaust gas is one of the causes concerning global warming of the earth and the air pollution. In order to improve environmental problems, it is necessary to develop combustion technology which has high efficiency and low environmental loads. However, spray combustion is com-plex phenomena that grain refinement of fuel, the evaporation, diffusion, ignition and flame spread, etc. progress simultaneously. Therefore, it is important to clarify details of spray combustion mechanism. Objective of our research is clarification of flame spread mechanism between droplets for fundamental research of spray combustion by utilizing the microgravity experiments and numerical analysis. It is useful to employ a fuel droplet array as the simplified model in order to elucidate detail flame spread mechanism between fuel droplets. The micro-gravity environment enables to expand time and spatial scale without the disturbing effect of natural convection. This is useful for clarification of complex phenomena such as combustion. icrogravity experiments have been performed in a drop tower, parabolic flight, and sounding rocket. In our research, it was revealed and classified that there are three modes concerning the flame spread of a linear droplet array. Appearances of flame spread modes are depending on non-dimensional ambient temperature RT/L and droplet spacing S/d. Here, R represents the universal gas constant, T, is the gas temperature, L, is the latent heat, S, is the droplet spacing, and d, is the initial diameter of the droplet. However, flame spread mode is changed by the formation of fuel vapor around droplets. Formation of fuel vapor depends on pre-evaporation of fuel droplets. Moreover, flame structure is also changed by pre-evaporation. The flame spread limit between droplets is affected by pre-evaporation of fuel droplets. The flame spread limit (S/d) is an important factor to the

  18. Modeling of evaporation and oxidation phenomena in plasma spraying of metal powders

    NASA Astrophysics Data System (ADS)

    Zhang, Hanwei

    Plasma spraying of metals in air is usually accompanied by evaporation and oxidation of the sprayed material. Optimization of the spraying process must ensure that the particles are fully molten during their short residence time in the plasma jet and prior to hitting the substrate, but not overheated to minimize evaporation losses. In atmospheric plasma spraying (ASP), it is also clearly desirable to be able to control the extent of oxide formation. The objective of this work to develop an overall mathematical model of the oxidization and volatilization phenomena involved in the plasma-spraying of metallic particles in air atmosphere. Four models were developed to simulate the following aspects of the atmospheric plasma spraying (APS) process: (a) the particle trajectories and the velocity and temperature profiles in an Ar-H 2 plasma jet, (b) the heat and mass transfer between particles and plasma jet, (c) the interaction between the evaporation and oxidation phenomena, and (d) the oxidation of liquid metal droplets. The resulting overall model was generated by adapting the computational fluid dynamics code FIDAP and was validated by experimental measurements carried out at the collaborating plasma laboratory of the University of Limoges. The thesis also examined the environmental implications of the oxidization and volatilization phenomena in the plasma spraying of metals. The modeling results showed that the combination of the standard k-s model of turbulence and the Boussinesq eddy-viscosity model provided a more accurate prediction of plasma gas behavior. The estimated NOx generation levels from APS were lower than the U.S.E.P.A. emission standard. Either enhanced evaporation or oxidation can occur on the surface of the metal particles and the relative extent is determined by the process parameters. Comparatively, the particle size has the greatest impact on both evaporation and oxidation. The extent of particle oxidation depends principally on gas

  19. Development of a laboratory prototype spraying flash evaporator.

    NASA Technical Reports Server (NTRS)

    Gaddis, J. L.

    1972-01-01

    A functional description of the flash evaporator that is being developed as a candidate for the Space Shuttle Environmental Control System thermal control is presented. A single evaporator configuration uses water as an evaporant to accommodate on-orbit peak heat loads and Freon 22 for terrestrial flight phases below 120,000 ft altitude. Development history, test plans, and operational characteristics are described. Detailed information is included to show: design features, fabrication techniques used for a prototype unit, redundancy considerations, and the control arrangement.

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

    NASA Technical Reports Server (NTRS)

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

    1982-01-01

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

  1. Effects of Feedstock Decomposition and Evaporation on the Composition of Suspension Plasma-Sprayed Coatings

    NASA Astrophysics Data System (ADS)

    Mauer, G.; Schlegel, N.; Guignard, A.; Vaßen, R.; Guillon, O.

    2015-10-01

    Emerging new applications and growing demands of plasma-sprayed coatings have initiated the development of new plasma spray processes. One of them is suspension plasma spraying (SPS). The use of liquid feedstock such as suspensions yields higher flexibility compared to the conventional atmospheric plasma spray processes as even submicron-to nano-sized particles can be processed. This allows achieving particular microstructural features, e.g., porous segmented or columnar-structured thermal barrier coatings. To exploit the potentials of such novel plasma spray processes, the plasma-feedstock interaction must be understood better. In this study, decomposition and evaporation of feedstock material during SPS were investigated, since particular difficulties can occur with respect to stoichiometry and phase composition of the deposits. Plasma conditions were analyzed by optical emission spectroscopy (OES). Experimental results are given, namely for gadolinium zirconate and for lanthanum strontium cobalt ferrite deposition. Moreover, the applied OES approach is validated by comparison with the simpler actinometry method.

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

    NASA Technical Reports Server (NTRS)

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

    2006-01-01

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

  3. Direct numerical simulation of ignition in turbulent n-heptane liquid-fuel spray jets

    SciTech Connect

    Wang, Y.; Rutland, C.J.

    2007-06-15

    Direct numerical simulation was used for fundamental studies of the ignition of turbulent n-heptane liquid-fuel spray jets. A chemistry mechanism with 33 species and 64 reactions was adopted to describe the chemical reactions. The Eulerian method is employed to solve the carrier-gas flow field and the Lagrangian method is used to track the liquid-fuel droplets. Two-way coupling interaction is considered through the exchange of mass, momentum, and energy between the carrier-gas fluid and the liquid-fuel spray. The initial carrier-gas temperature was 1500 K. Six cases were simulated with different droplet radii (from 10 to 30 {mu}m) and two initial velocities (100 and 150 m/s). From the simulations, it was found that evaporative cooling and turbulence mixing play important roles in the ignition of liquid-fuel spray jets. Ignition first occurs at the edges of the jets where the fuel mixture is lean, and the scalar dissipation rate and the vorticity magnitude are very low. For smaller droplets, ignition occurs later than for larger droplets due to increased evaporative cooling. Higher initial droplet velocity enhances turbulence mixing and evaporative cooling. For smaller droplets, higher initial droplet velocity causes the ignition to occur earlier, whereas for larger droplets, higher initial droplet velocity delays the ignition time. (author)

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

    NASA Astrophysics Data System (ADS)

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

    2013-11-01

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

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

    NASA Technical Reports Server (NTRS)

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

    1987-01-01

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

  6. Preliminary Tests on the Vaporization of Fuel Sprays

    NASA Technical Reports Server (NTRS)

    Rothrock, A M

    1932-01-01

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

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

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

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

    NASA Astrophysics Data System (ADS)

    Kannaiyan, Kumaran; Sadr, Reza

    2011-11-01

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

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

    PubMed

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

    2015-10-13

    We demonstrate real-time quantitative phase imaging as a new optical approach for measuring the evaporation dynamics of sessile microdroplets. Quantitative phase images of various droplets were captured during evaporation. The images enabled us to generate time-resolved three-dimensional topographic profiles of droplet shape with nanometer accuracy and, without any assumptions about droplet geometry, to directly measure important physical parameters that characterize surface wetting processes. Specifically, the time-dependent variation of the droplet height, volume, contact radius, contact angle distribution along the droplet's perimeter, and mass flux density for two different surface preparations are reported. The studies clearly demonstrate three phases of evaporation reported previously: pinned, depinned, and drying modes; the studies also reveal instances of partial pinning. Finally, the apparatus is employed to investigate the cooperative evaporation of the sprayed droplets. We observe and explain the neighbor-induced reduction in evaporation rate, that is, as compared to predictions for isolated droplets. In the future, the new experimental methods should stimulate the exploration of colloidal particle dynamics on the gas-liquid-solid interface. PMID:26389788

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

    NASA Technical Reports Server (NTRS)

    Rothrock, A M; Waldron, C D

    1931-01-01

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

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

    NASA Technical Reports Server (NTRS)

    Wierum, F. A.

    1979-01-01

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

  12. Spray evaporation and dispersion of n-heptane droplets within premixed flame

    NASA Astrophysics Data System (ADS)

    Chrigui, Mouldi; Zghal, Ali; Sadiki, Amsini; Janicka, Johannes

    2010-10-01

    A detailed numerical simulation of n-heptane droplets was carried out on a stationary three-dimensional configuration with complex geometry. The investigations focused on spray evaporation and dispersion within a carrier phase that featured operating conditions similar to those found in industrial applications, i.e. elevated pressure and temperature. The simulations were carried out using the Eulerian-Lagrangian approach with two-way coupling. There were two cases. The first dealt with spray characteristics within the preheated carrier phase without considering combustion. The second investigated the influence of combustion on droplet characteristics. Both cases had the same boundary conditions. The numerical simulations used two models to compute the progress variable mean reaction rate that governs the combustion process, which is captured by the Bray-Moss-Libby model.

  13. Numerical simulation of emulsified fuel spray combustion with puffing and micro-explosion

    SciTech Connect

    Watanabe, Hirotatsu; Matsushita, Yohsuke; Aoki, Hideyuki; Miura, Takatoshi

    2010-05-15

    The purpose of this study was to develop numerical simulation of spray combustion of emulsified fuel with considering puffing and micro-explosion. First, a mathematical model for puffing was proposed. In the proposed puffing model, the rate of mass change of a droplet during puffing was expressed by the evaporation rate of dispersed water and the mass change rate due to fine droplets spouted from the droplet surface. The mass change rate due to fine droplets was related to the evaporation rate of the dispersed water and each liquid content. This model had only one experimental parameter. The essential feature of this model was that it was simple to apply to numerical simulation of spray combustion. First, the validity of the proposed puffing model was investigated with the experimental results for a single droplet. The calculated results for a single droplet with the experimental parameter varying from 5.0 to 10 were in good agreement with the experimental results. Moreover, numerical simulation of spray combustion of emulsified fuel was carried out. The occurrence of puffing and micro-explosion was determined by the inner droplet temperature. When micro-explosion occurred, a droplet changed to vapor rapidly. When the proposed puffing model was used in numerical simulation of spray combustion, the experimental parameter in the puffing model was determined for each droplet by random numbers within the range 5.0-10. The calculated results of spray combustion of emulsified fuel without considering puffing or micro-explosions were different from the experimental results even where combustion reactions were almost terminated. Meanwhile, the calculated results when considering puffing and micro-explosions were in good agreement with experimental results at the same location. (author)

  14. Jet-A fuel evaporation analysis in conical tube injectors

    NASA Astrophysics Data System (ADS)

    Lai, M.-C.; Chue, T.-H.; Zhu, G.; Sun, H.; Tacina, R.; Chun, K.; Hicks, Y.

    1991-01-01

    A simple one-dimensional drop-life-history analysis and a multidimensional spray calculation using KIVA-II code are applied to the vaporization of Jet-A fuel in multiple tube injectors. Within the assumptions of the analysis, the one-dimensional results are useful for design purposes. The pressure-atomizer breakup models do not accurately predict the dropsize measured experimentally or deduced from the one-dimensional analysis. Cold flow visualization and dropsize measurements show that capillary wave breakup mechanism plays an important role in the spray angle and droplet impingement on the tube wall.

  15. Characteristics of MCrAlY coatings sprayed by high velocity oxygen-fuel spraying system

    SciTech Connect

    Itoh, Y.; Saitoh, M.; Tamura, M.

    2000-01-01

    High velocity oxygen-fuel (HVOF) spraying system in open air has been established for producing the coatings that are extremely clean and dense. It is thought that the HVOF sprayed MCrAlY (M is Fe, Ni and/or Co) coatings can be applied to provide resistance against oxidation and corrosion to the hot parts of gas turbines. Also, it is well known that the thicker coating can be sprayed in comparison with any other thermal spraying systems due to improved residual stresses. However, thermal and mechanical properties of HVOF coatings have not been clarified. Especially, the characteristics of residual stress, that are the most important property from the view point of production technique, have not been made clear. In this paper, the mechanical properties of HVOF sprayed MCrAlY coatings were measured in both the case of as-sprayed and heat-treated coatings in comparison with a vacuum plasma sprayed MCrAlY coatings. It was confirmed that the mechanical properties of HVOF sprayed MCrAlY coatings could be improved by a diffusion heat treatment to equate the vacuum plasma sprayed MCrAlY coatings. Also, the residual stress characteristics were analyzed using a deflection measurement technique and a X-ray technique. The residual stress of HVOF coating was reduced by the shot-peening effect comparable to that of a plasma spray system in open air. This phenomena could be explained by the reason that the HVOF sprayed MCrAlY coating was built up by poorly melted particles.

  16. Dropwise ignition versus external ignition for multicomponent fuel sprays

    NASA Astrophysics Data System (ADS)

    Mawid, M.; Aggarwal, S. K.

    1988-07-01

    An attempt has been made to identify conditions for dropwise ignition and spray ignition. Both pure as well as multicomponent fuels are considered. For dropwise ignition, an existing ignition criterion has been modified to account for the nonlinear dependence of reaction rate on fuel and oxygen concentrations and to account for the multicomponent nature of the fuel. The external or spray ignition is considered through the zero heat flux condition at the ignition source. The effect of chemical kinetics is examined by employing reaction schemes with unity as well as non-unity exponents of fuel and oxygen concentrations. Results indicate that for most of the conditions considered, the individual droplet ignition is favored over the external ignition. Only when the drop diameter is smaller than 30 microns, the spray ignites earlier than droplets. The addition of a small amount of a volatile component significantly enhances the ignitability of both modes. However, the effect is stronger for the dropwise ignition mode.

  17. Some Characteristics of Fuel Sprays from Open Nozzles

    NASA Technical Reports Server (NTRS)

    Rothrock, A M; Lee, D W

    1930-01-01

    The penetration and cone-angle of fuel sprays from open nozzles were recorded with the NACA Spray Photography Equipment. The results show that for injection systems in which the rate of pressure rise at the discharge orifice is high, open nozzles give spray-tip velocities and penetrations which compare favorably with those of closed nozzles. The spray cone-angle was the same for all tests, although open nozzles having different orifice diameters were used, and one nozzle was used both as an open and as a closed nozzle. In designing a fuel system using open nozzles, particular care must be taken to avoid air pockets. The check valve should be placed close to the discharge orifice.

  18. Novel method for the measurement of liquid film thickness during fuel spray impingement on surfaces.

    PubMed

    Henkel, S; Beyrau, F; Hardalupas, Y; Taylor, A M K P

    2016-02-01

    This paper describes the development and application of a novel optical technique for the measurement of liquid film thickness formed on surfaces during the impingement of automotive fuel sprays. The technique makes use of the change of the light scattering characteristics of a metal surface with known roughness, when liquid is deposited. Important advantages of the technique over previously established methods are the ability to measure the time-dependent spatial distribution of the liquid film without a need to add a fluorescent tracer to the liquid, while the measurement principle is not influenced by changes of the pressure and temperature of the liquid or the surrounding gas phase. Also, there is no need for non-fluorescing surrogate fuels. However, an in situ calibration of the dependence of signal intensity on liquid film thickness is required. The developed method can be applied to measure the time-dependent and two-dimensional distribution of the liquid fuel film thickness on the piston or the liner of gasoline direct injection (GDI) engines. The applicability of this technique was evaluated with impinging sprays of several linear alkanes and alcohols with different thermo-physical properties. The surface temperature of the impingement plate was controlled to simulate the range of piston surface temperatures inside a GDI engine. Two sets of liquid film thickness measurements were obtained. During the first set, the surface temperature of the plate was kept constant, while the spray of different fuels interacted with the surface. In the second set, the plate temperature was adjusted to match the boiling temperature of each fuel. In this way, the influence of the surface temperature on the liquid film created by the spray of different fuels and their evaporation characteristics could be demonstrated. PMID:26906828

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

    NASA Astrophysics Data System (ADS)

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

    2015-11-01

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

  20. An Experimental Investigation and Numerical Analysis of Multi-Component Fuel Spray

    NASA Astrophysics Data System (ADS)

    Myong, Kwang-Jae; Arai, Motoyuki; Tanaka, Tomoyuki; Senda, Jiro; Fujimoto, Hajime

    In this study, droplet atomization and vaporization characteristics with multi-component fuel were investigated by experimental and numerical simulation methods. Spray characteristics of multi-component fuel including spray cone angle, spray angle and spray tip penetration were analyzed from shadowgraph imaging. Numerical simulation to investigate spatial distribution of fuel-vapor concentration of each component within multi-component fuel was implemented in KIVA code. Vaporization process was calculated by a simple two-phase region which was approximated by modified saturated liquid-vapor line. Experimental results show that spray cone angle and spray angle become larger increasing in mass fraction of low boiling point component. And spray tip penetration becomes shorter with increasing in mass fraction of low boiling point component in vaporizing spray during that is same on every mixed fuel in non-vaporizing spray. From numerical simulation results, temporal and spatial distribution of each fuel vapor concentration was found to be stratification.

  1. Spray Penetration with a Simple Fuel Injection Nozzle

    NASA Technical Reports Server (NTRS)

    Miller, Harold E; Beardsley, Edward G

    1926-01-01

    The purpose of the tests covered by this report was to obtain specific information on the rate of penetration of the spray from a simple injection nozzle, having a single orifice with a diameter of 0.015 inch when injecting into compressed gases. The results have shown that the effects of both chamber and fuel pressures on penetration are so marked that the study of sprays by means of high-speed photography or its equivalent is necessary if the effects are to be appreciated sufficiently to enable rational analysis. It was found for these tests that the negative acceleration of the spray tip is approximately proportional to the 1.5 power of the instantaneous velocity of the spray tip.

  2. Certification of an agricultural spray aircraft on ethanol fuel

    SciTech Connect

    Shauck, M.E.; Zanin, M.G.

    1994-12-31

    A Piper Pawnee, one of the most common agricultural spray aircraft, is currently undergoing Federal Aviation Administration (FAA) certification to allow the use of denatured ethanol as its fuel. This certification is part of a broader effort to introduce ethanol as a replacement for aviation gasoline. Various reasons brought about the choice of an agricultural spray aircraft to be certified on ethanol. One is the minimization of initial fuel distribution problems. Agricultural aviation often requires only single fuel storage since most of the flying is local. Additionally, corn-produced ethanol is the natural fuel of choice for farming operations. The increased power developed on ethanol compared to aviation gasoline (avgas) is very important when operating heavily loaded spray aircraft at very low altitudes. The power-plant, a Lycoming IO-540, is already certified. The aircraft is currently flying on ethanol in order to satisfy the airframe requirements. The effort is being supported by a consortium of organizations of corn-producing states. Upon completion of certification, the aircraft will be demonstrated around the mid-western states. Certification will allow the use of the aircraft in the commercial arena. Many mid-western agricultural spray operations and ag-pilots have already expressed interest in converting their aircraft to ethanol fuel.

  3. Diffusion properties of aqueous slurries in evaporative spray drying of copper (II) chloride dihydrate

    NASA Astrophysics Data System (ADS)

    Slowikowski, M.; Naterer, G. F.; Odukoya, A.

    2014-09-01

    This study examines the evaporative heat transfer and diffusive mass transfer of a droplet of CuCl2 solution. The validation of a new predictive model involves comparisons with experimental data from previous studies of different fluids based on non-dimensional analysis. The study provides new insight about the effects of different concentrations of water on the CuCl2 slurry drying at low to moderate air temperatures. Predictive correlations of heat and mass transfer are developed for the aqueous solution, subject to various drying conditions. The analysis is performed for moist air in contact with a sprayed aqueous solution of copper (II) chloride dihydrate [CuCl2·(2H2O)]. Results are presented and discussed for the drying processes.

  4. High-pressure combustion of binary fuel sprays

    NASA Technical Reports Server (NTRS)

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

    1995-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    1992-12-01

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

  6. Influence of drop size distribution and fuel vapor fraction on premixed spray combustion

    NASA Astrophysics Data System (ADS)

    Machiroutu, Sridhar Venkatabojji

    Premixed spray combustion is affected by fuel and oxidizer properties, mixture equivalence ratio and spray quality. The spray quality is characterized by a mean droplet diameter (SMD) and a droplet size distribution (DSD). Prior experimental studies have considered only the influence of SMD, in part due to the difficulty in controlling the DSD independently. The present work provides experimental evidence demonstrating the effect of the fuel droplet size distribution and fuel vapor fraction on premixed spray combustion. Combustion experiments were performed in a pilot-ignited, continuous flow, tubular, vertical test rig wherein fuel sprays were injected into an air stream. A novel twin-atomizer technique that allowed control over overall equivalence ratio, SMD, DSD, and fuel vapor fraction of the premixed spray was used to generate test sprays. A line-of-sight, infrared (IR) extinction technique was developed to quantify the fuel vapor fraction in premixed sprays. Radial distributions of fuel vapor were evaluated using an 'onion peeling' deconvolution technique. Combustion of test sprays indicated flame propagation among regions of high fuel vapor fraction to generate a high rate of combustion. In lean premixed sprays, the presence of a low fuel vapor concentration does not impact the combustion process. Experimental evidence demonstrating the enhancement of flame propagation velocity for optimal SMDs of ethanol sprays has been found. It was observed that test sprays with narrower DSDs have faster burning rates and more complete combustion. The DSD of the sprays were characterized with a droplet surface-area-based standard deviation of the DSD.

  7. Numerical investigation of spray ignition of a multi-component fuel surrogate

    NASA Astrophysics Data System (ADS)

    Backer, Lara; Narayanaswamy, Krithika; Pepiot, Perrine

    2014-11-01

    Simulating turbulent spray ignition, an important process in engine combustion, is challenging, since it combines the complexity of multi-scale, multiphase turbulent flow modeling with the need for an accurate description of chemical kinetics. In this work, we use direct numerical simulation to investigate the role of the evaporation model on the ignition characteristics of a multi-component fuel surrogate, injected as droplets in a turbulent environment. The fuel is represented as a mixture of several components, each one being representative of a different chemical class. A reduced kinetic scheme for the mixture is extracted from a well-validated detailed chemical mechanism, and integrated into the multiphase turbulent reactive flow solver NGA. Comparisons are made between a single-component evaporation model, in which the evaporating gas has the same composition as the liquid droplet, and a multi-component model, where component segregation does occur. In particular, the corresponding production of radical species, which are characteristic of the ignition of individual fuel components, is thoroughly analyzed.

  8. 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.

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

    SciTech Connect

    Moran, D.P.

    1994-10-01

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

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

    NASA Technical Reports Server (NTRS)

    Lee, Dana W

    1936-01-01

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

  11. Thermal Plasma Spraying Applied on Solid Oxide Fuel Cells

    NASA Astrophysics Data System (ADS)

    Soysal, D.; Arnold, J.; Szabo, P.; Henne, R.; Ansar, S. A.

    2013-06-01

    Solid oxide fuel cells (SOFCs), attractive for diverse applications in a broad range from small portable and auxiliary power units, up to central power systems, are conventionally produced by sintering methods. However, plasma spraying promises some advantages particularly for cells with metal support. In the present paper, research activities conducted in recent years at DLR as well as latest developments on plasma sprayed functional layers for SOFC as cathodes, electrolytes, and anodes are reported. Power densities of more than 800 mW/cm2 were achieved for plasma sprayed single cells of 12.56 cm2 size, and 300 mW/cm2, respectively, with a 250 W stack made of 10 cells. These values were attained at 0.7 V and 800 °C, with H2:N2 = 1:1 as fuel gas and air as oxidizing gas. Furthermore, continuous operation of more than 5000 h was attained with a plasma sprayed metal-supported SOFC stack which could also withstand more than 30 redox and thermal cycles.

  12. Vacuum plasma spray applications on liquid fuel rocket engines

    NASA Technical Reports Server (NTRS)

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

    1992-01-01

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

  13. Vacuum plasma spray applications on liquid fuel rocket engines

    NASA Astrophysics Data System (ADS)

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

    1992-07-01

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

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

    NASA Technical Reports Server (NTRS)

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

    1984-01-01

    A monodisperse aerosol generator was modified to study ignition requirements, flammability limits, and flame speeds in the transition region. An ignition system was developed and tested. The fabrication of an optical drop sizing system is nearly complete. Preliminary measurements of droplet size effects on the minimum ignition energy for n-heptane sprays performed. Parameteric studies of droplet size effects on minimum ignition energies of various fuels including alcohols are in progress.

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

    NASA Astrophysics Data System (ADS)

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

    2016-09-01

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

  16. Efficiency of using solid wood fuels in maple syrup evaporators. Forest service research paper (final)

    SciTech Connect

    Garrett, L.D.

    1981-01-01

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

  17. Process gases for high velocity oxy-fuel thermal spraying

    SciTech Connect

    Creffield, G.K.; Chapman, I.F.; Cole, M.A.; Page, W.J.; McDonough, T.

    1994-12-31

    The importance of fuel and other process gases for high velocity oxy-fuel (HVOF) thermal spraying and especially the delivery of them to the point of use is well recognized. Problems associated with the supply of liquid fuel gases, at the high flow rates and pressures required by this process, have been addressed. Considerable development work has gone into designing an appropriate liquid withdrawal and vaporizer system for propylene, which overcomes these previous difficulties and enables users to maintain adequate fuel gas flow rates in order to ensure optimum operating conditions for the production of high quality coatings. A feature of the thermal spray process is that the temperature of the workpiece is kept low, typically below 150 C, in order to reduce residual stresses in the coating and to protect heat sensitive substrates. Traditionally this has been by compressed air, however, improved cooling has been achieved using carbon dioxide. Specially designed equipment is now available which provides and directs a cold mixture of carbon dioxide gas and solid particles (snow) via suitable nozzles, on the workpiece. The position of the cooling stream can be varied, depending on the application. These developments emphasize the importance now attached to providing dedicated gas installation packages for HVOF.

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

    NASA Technical Reports Server (NTRS)

    Lee, Dana W

    1937-01-01

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

  19. A Nonlinear Model for Fuel Atomization in Spray Combustion

    NASA Technical Reports Server (NTRS)

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

    2003-01-01

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

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

    NASA Technical Reports Server (NTRS)

    Joachim, W F; Beardsley, Edward G

    1928-01-01

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

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

    PubMed

    Laha, T; Liu, Y; Agarwal, A

    2007-02-01

    Free standing structures of hypereutectic aluminum-23 wt% silicon nanocomposite with multiwalled carbon nanotubes (MWCNT) reinforcement have been successfully fabricated by two different thermal spraying technique viz Plasma Spray Forming (PSF) and High Velocity Oxy-Fuel (HVOF) Spray Forming. Comparative microstructural and mechanical property evaluation of the two thermally spray formed nanocomposites has been carried out. Presence of nanosized grains in the Al-Si alloy matrix and physically intact and undamaged carbon nanotubes were observed in both the nanocomposites. Excellent interfacial bonding between Al alloy matrix and MWCNT was observed. The elastic modulus and hardness of HVOF sprayed nanocomposite is found to be higher than PSF sprayed composites. PMID:17450788

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

    NASA Astrophysics Data System (ADS)

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

    2015-07-01

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

  3. Evaporation Of Clustered Drops Of Binary-Liquid Fuels

    NASA Technical Reports Server (NTRS)

    Bellan, Josette; Harstad, Kenneth G.

    1993-01-01

    Report repeats and elaborates upon information presented in "Diffusion Of Mass In Evaporating Multicomponent Drops" (NPO-18206). Presents details of mathematical model of evaporation of binary liquid from both dense and dilute clusters of drops. Interactions among evaporation, diffusion in liquids, slip velocity, and other phenomena modeled.

  4. Solid oxide fuel cell electrolytes produced by a combination of suspension plasma spray and very low pressure plasma spray.

    SciTech Connect

    Slamovich, Elliot; Fleetwood, James; McCloskey, James F.; Hall, Aaron Christopher; Trice, Rodney Wayne

    2010-07-01

    Plasma spray coating techniques allow unique control of electrolyte microstructures and properties as well as facilitating deposition on complex surfaces. This can enable significantly improved solid oxide fuel cells (SOFCs), including non-planar designs. SOFCs are promising because they directly convert the oxidization of fuel into electrical energy. However, electrolytes deposited using conventional plasma spray are porous and often greater than 50 microns thick. One solution to form dense, thin electrolytes of ideal composition for SOFCs is to combine suspension plasma spray (SPS) with very low pressure plasma spray (VLPPS). Increased compositional control is achieved due to dissolved dopant compounds in the suspension that are incorporated into the coating during plasma spraying. Thus, it is possible to change the chemistry of the feed stock during deposition. In the work reported, suspensions of sub-micron diameter 8 mol.% Y2O3-ZrO2 (YSZ) powders were sprayed on NiO-YSZ anodes at Sandia National Laboratories (SNL) Thermal Spray Research Laboratory (TSRL). These coatings were compared to the same suspensions doped with scandium nitrate at 3 to 8 mol%. The pressure in the chamber was 2.4 torr and the plasma was formed from a combination of argon and hydrogen gases. The resultant electrolytes were well adhered to the anode substrates and were approximately 10 microns thick. The microstructure of the resultant electrolytes will be reported as well as the electrolyte performance as part of a SOFC system via potentiodynamic testing and impedance spectroscopy.

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

    NASA Astrophysics Data System (ADS)

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

    2016-02-01

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

  6. One-dimensional and quasi-one-dimensional ZnO nanostructures prepared by spray-pyrolysis-assisted thermal evaporation

    NASA Astrophysics Data System (ADS)

    Liu, Wen-Cheng; Cai, Wei

    2008-03-01

    One-dimensional (1D) and quasi-1D ZnO nanostructures have been fabricated by a kind of new spray-pyrolysis-assisted thermal evaporation method. Pure ZnO powder serves as an evaporation source. Thus-obtained products have been characterized by X-ray diffraction (XRD) analysis, scanning electron microscope (SEM) equipped with energy dispersive X-ray spectroscopy (EDS), transmission electron microscope (TEM). The room temperature photoluminescence spectrum of these ZnO nanostructures is presented. The results show that as-grown ZnO nanomaterials have a hexagonal wurtzite crystalline structure. Besides nanosaws, nanobelts and nanowires, complex ZnO nanotrees have also been observed in synthesized products. The study provides a new simple route to construct 1D and quasi-1D ZnO nanomaterials, which can probably be extended to fabricate other oxide nanomaterials with high melting point and doped oxide nanomaterials.

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

    NASA Technical Reports Server (NTRS)

    Gelalles, A G

    1930-01-01

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

  8. Original use of a direct injection high efficiency nebulizer for the standardization of liquid fuels spray flames

    NASA Astrophysics Data System (ADS)

    Lemaire, R.; Maugendre, M.; Schuller, T.; Therssen, E.; Yon, J.

    2009-10-01

    It is of practical importance to lead laboratory-scale experiments allowing a better understanding of the impact of commercial fuels composition on the formation of combustion residues such as soot particles. To this end, a hybrid burner has been designed recently to burn high-speed sprays of small liquid fuel droplets. It consists of a Holthuis (previously McKenna) burner originally equipped with a direct injection high efficiency nebulizer for the atomization of liquid hydrocarbons. A detailed description of this original setup is given in this paper. A priori estimations of atomization and evaporation times and length scales are then proposed and compared with experimental data. Droplet-size distribution measurements obtained in nonreacting conditions using a Malvern Spraytec particle sizer are presented and compared with values estimated by calculation. Cold sprays contours and liquid jet lengths in flames determined by Mie scattering at 532 and 1064 nm, respectively, are also presented. The results discussed in this work indicate that the hydrodynamic characteristics of the sprays generated with our system are relatively independent of the physical properties of fuels leading to comparable flames with identical liquid jet lengths, dimensions, and global structure. This feature facilitates an accurate comparison of flames burning various liquid hydrocarbons, which is of interest to emphasize differences in pollutants emissions and to highlight chemical effects for soot formation analysis.

  9. Injector spray characterization of methanol in reciprocating engines

    SciTech Connect

    Dodge, L.; Naegeli, D.

    1994-06-01

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

  10. Group evaporation

    NASA Technical Reports Server (NTRS)

    Shen, Hayley H.

    1991-01-01

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

  11. An evaporative and engine-cycle model for fuel octane sensitivity prediction

    SciTech Connect

    Moran, D.P.; Taylor, A.B.

    1995-12-31

    The Motor Octane Number (MON) ranks fuels by their chemical resistance to knock. Evaporative cooling coupled with fuel chemistry determine Research Octane Number (RON) antiknock ratings. It is shown in this study that fuel Octane sensitivity (numerically RON minus MON) is liked to an important difference between the two test methods; the RON test allows each fuel`s evaporative cooling characteristics to affect gas temperature, while the MON test generally eliminates this effect by pre-evaporation. In order to establish RON test charge temperatures, a computer model of fuel evaporation was adapted to Octane Engine conditions, and simulations were compared with real Octane Test Engine measurements including droplet and gas temperatures. A novel gas temperature probe yielded data that corresponded well with model predictions. Tests spanned single component fuels and blends of isomers, n-paraffins, aromatics and alcohols. Commercially available automotive and aviation gasolines were also tested. A good correlation was observed between the computer predictions and measured temperature data across the range of pure fuels and blends. A numerical method to estimate the effect of precombustion temperature differences on Octane sensitivity was developed and applied to analyze these data, and was found to predict the widely disparate sensitivities of the tested fuels with accuracy. Data are presented showing mixture temperature histories of various tested fuels, and consequent sensitivity predictions. It is concluded that a fuel`s thermal-evaporative behavior gives rise to fuel Octane sensitivity as measured by differences between the RON and MON tests. This is demonstrated by the success, over a wide range of fuels, of the sensitivity predictor method describes. Evaporative cooling, must therefore be regarded as an important parameter affecting the general road performance of automobiles.

  12. Microstructure and properties of tungsten carbide coatings sprayed with various high-velocity oxygen fuel spray systems

    NASA Astrophysics Data System (ADS)

    Schwetzke, R.; Kreye, H.

    1999-09-01

    This article reports on a series of experiments with various high-velocity oxygen fuel spray systems (Jet Kote, Top Gun, Diamond Jet (DJ) Standard, DJ 2600 and 2700, JP-5000, Top Gun-K) using different WC-Co and WC-Co-Cr powders. The microstructure and phase composition of powders and coatings were analyzed by optical and scanning electron microscopy and x-ray diffraction. Carbon and oxygen content of the coatings were determined to study the decarburization and oxidation of the material during the spray process. Coatings were also characterized by their hardness, bond strength, abrasive wear, and corrosion resistance. The results demonstrate that the powders exhibit various degrees of phase transformation during the spray process depending on type of powder, spray system, and spray parameters. Within a relatively wide range, the extent of phase transformation has only little effect on coating properties. Therefore, coatings of high hardness and wear resistance can be produced with all HVOF spray systems when the proper spray powder and process parameters are chosen.

  13. Gas density effect on dropsize of simulated fuel sprays

    NASA Technical Reports Server (NTRS)

    Ingebo, Robert D.

    1989-01-01

    Two-phase flow in pneumatic two-fluid fuel nozzles was investigated experimentally to determine the effect of atomizing-gas density and gas mass-flux on liquid-jet breakup in sonic-velocity gas-flow. Dropsize data were obtained for the following atomizing-gases: nitrogen; argon; carbon dioxide; and helium. They were selected to cover a gas molecular-weight range of 4 to 44. Atomizing-gas mass-flux ranged from 6 to 50 g/sq cm-sec and four differently sized two-fluid fuel nozzles were used having orifice diameters that varied from 0.32 to 0.56 cm. The ratio of liquid-jet diameter to SMD, D sub o/D sub 32, was correlated with aerodynamic and liquid-surface forces based on the product of the Weber and Reynolds number, and gas-to-liquid density ratio, rho sub g/rho sub 1. To correlate spray dropsize with breakup forces produced by using different atomizing-gases, a new molecular-scale dimensionless group was derived. The derived dimensionless group was used to obtain an expression for the ratio of liquid-jet diameter to SMD, D sub o/D sub 32. The mathematical expression of this phenomenon incorporates the product of the Weber and Reynolds number, liquid viscosity, surface tension, acoustic gas velocity, the RMS velocity of gas molecules, the acceleration of gas molecules due to gravity, and gas viscosity. The mathematical expression encompassing these parameters agrees well with the atomization theory for liquid-jet breakup in high velocity gas flow. Also, it was found that at the same gas mass-flux, helium was considerably more effective than nitrogen in producing small droplet sprays with SMD's in the order of 5 micrometers.

  14. Gas density effect on dropsize of simulated fuel sprays

    NASA Technical Reports Server (NTRS)

    Ingebo, Robert D.

    1989-01-01

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

  15. Characterization of high velocity oxy-fuel combustion sprayed hydroxyapatite.

    PubMed

    Haman, J D; Lucas, L C; Crawmer, D

    1995-02-01

    Bioceramic coatings, created by the high velocity oxy-fuel combustion spraying of hydroxyapatite (HA) powders onto commercially pure titanium, were characterized in order to determine whether this relatively new coating process can be successfully applied to bioceramic coatings of orthopaedic and dental implants. Fourier transform infrared spectroscopy, X-ray diffraction and scanning electron microscopy were used to characterize both the HA starting powders and coatings. A 12 wk immersion test was conducted and the resulting changes in the coatings were also characterized. Calcium ion release during dissolution was measured with flame atomic absorption during the first 6 weeks of the immersion study. A comparison of powder and coating X-ray diffraction patterns and lattice parameters revealed an HA-type coating with some loss in crystallinity. Fourier transform infrared results showed a partial loss of the OH- group during spraying, however the phosphate groups were still present. Scanning electron microscopy analysis showed a lamellar structure with very close coating-to-substrate apposition. The coatings experienced a loss of calcium during the immersion study, with the greatest release in calcium occurring during the first 6 days of the study. No significant structural or chemical changes were observed during the 12 wk immersion study. These results indicate that the high velocity oxy-fuel process can produce an HA-type coating; however, the process needs further optimization, specifically in the areas of coating-to-substrate bond strength and minimization of phases present other than HA, before it would be recommended for commercial use. PMID:7749000

  16. A laser tomographic investigation of liquid fuel sprays

    NASA Technical Reports Server (NTRS)

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

    1980-01-01

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

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

    NASA Astrophysics Data System (ADS)

    Hugo, Bruce Robert

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

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

    NASA Astrophysics Data System (ADS)

    Kannaiyan, Kumaran; Sadr, Reza

    2015-11-01

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

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

    NASA Astrophysics Data System (ADS)

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

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

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

    SciTech Connect

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

    1993-06-01

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

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

    NASA Technical Reports Server (NTRS)

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

    2000-01-01

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

  2. Diffusion Of Mass In Evaporating Multicomponent Drops

    NASA Technical Reports Server (NTRS)

    Bellan, Josette; Harstad, Kenneth G.

    1992-01-01

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

  3. Analytical and mechanical testing of high velocity oxy-fuel thermal sprayed and plasma sprayed calcium phosphate coatings.

    PubMed

    Haman, J D; Chittur, K K; Crawmer, D E; Lucas, L C

    1999-01-01

    Plasma spraying (PS) is the most frequently used coating technique for implants; however, in other industries a cheaper, more efficient process, high-velocity oxy-fuel thermal spraying (HVOF), is in use. This process provides higher purity, denser, more adherent coatings than plasma spraying. The primary objective of this work was to determine if the use of HVOF could improve the mechanical properties of calcium phosphate coatings. Previous studies have shown that HVOF calcium phosphate coatings are more crystalline than plasma sprayed coatings. In addition, because the coatings are exposed to more complex loading profiles in vivo than standard ASTM tensile tests provide, a secondary objective of this study was to determine the applicability of four-point bend testing for these coatings. Coatings produced by HVOF and PS were analyzed by profilometry, diffuse reflectance Fourier transform infrared spectroscopy, X-ray diffraction, four-point bend, and ASTM C633 tensile testing. HVOF coatings were found to have lower amorphous calcium phosphate content, higher roughness values, and lower ASTM C633 bond strengths than PS coatings; however, both coatings had similar crystal unit cell sizes, phases present (including hydroxyapatite, beta-tricalcium phosphate, and tetracalcium phosphate), and four-point bend bond strengths. Thus, the chemical, structural, and mechanical results of this study, in general, indicate that the use of HVOF to produce calcium phosphate coatings is equivalent to those produced by plasma spraying. PMID:10556851

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

    NASA Astrophysics Data System (ADS)

    Sazhin, Sergei S.; Qubeissi, Mansour Al

    2016-06-01

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

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

    PubMed

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

    2015-01-01

    The emission characteristics of motorcycles using gasoline and E10 (90% gasoline and 10% ethanol by volume) were investigated in this article. Exhaust and evaporative emissions of three motorcycles were investigated on the chassis dynamometer over the Urban Driving Cycle (UDC) and in the Sealed Housing for Evaporative Determination (SHED) including regulated and unregulated emissions. The regulated emissions were detected by an exhaust gas analyzer directly. The unregulated emissions including carbonyls and volatile organic compounds (VOCs) were sampled through battery-operated air pumps using tubes coated with 2,4-dinitrophenylhydrazine (DNPH) and Tenax TA, respectively. The experimental results showed that the emission factors of total hydrocarbons (THC) and carbon monoxide (CO) from E10 fueling motorcycles decreased by 26%-45% and 63%-73%, while the emission factor of NOx increased by 36%-54% compared with those from gasoline fueling motorcycles. For unregulated emissions, the emission amount of VOCs from motorcycles fueled with E10 decreased by 18%-31% while total carbonyls were 2.6-4.5 times higher than those for gasoline. For evaporative emissions of THC and VOCs, for gasoline or E10, the diurnal breathing loss (DBL) was higher than hot soak loss (HSL). Using E10 as a fuel does not make much difference in the amount of evaporative THC, while resulted in a slightly growth of 14%-17% for evaporative BETX (benzene, toluene, ethylbenzene, xylene). PMID:25302450

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

    NASA Technical Reports Server (NTRS)

    Vezhba, I.

    1979-01-01

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

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

    NASA Technical Reports Server (NTRS)

    Lee, Dana W

    1933-01-01

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

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

    NASA Astrophysics Data System (ADS)

    Tahsini, A. M.; Farshchi, M.

    2010-10-01

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

  9. 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.

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

    SciTech Connect

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

    1993-12-31

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

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

    NASA Technical Reports Server (NTRS)

    Rothrock, A M; Marsh, E T

    1934-01-01

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

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

    NASA Technical Reports Server (NTRS)

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

    1980-01-01

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

  13. Composition changes in liquid oxygen as a result of evaporation and relation to fuel cell operation

    NASA Technical Reports Server (NTRS)

    Easter, R. W.

    1973-01-01

    An expression is presented which may be used to estimate changes in composition as a consequence of evaporation during the storage of liquid oxygen. The sensitivity of fuel-cell systems to such changes is discussed, and sample calculations are presented.

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

    NASA Astrophysics Data System (ADS)

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

    2016-01-01

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

  15. Experimental investigation of the liquid fuel evaporation in a premix duct for lean premixed and prevaporized combustion

    SciTech Connect

    Brandt, M.; Gugel, K.O.; Hassa, C.

    1997-10-01

    Liquid fuel evaporation was investigated in a premix duct, operating at conditions expected for lean premixed and prevaporized combustion. Results from a flat prefilming airblast atomizer are presented. Kerosine Jet A was used in all experiments. Air pressure, air temperature, and liquid fuel flow rate were varied separately; their relative influences on atomization, evaporation, and fuel dispersion are discussed. The results show that at pressures up to 15 bars and temperatures up to 850 K, nearly complete evaporation of the fuel was achieved, without autoignition of the fuel. For the configuration tested, the fuel distributions of the liquid and evaporated fuel show very little difference in their dispersion characteristics and were not much affected by a variation of the operating conditions.

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

    PubMed

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

    2016-09-13

    Numerical investigations of the dynamics and evaporative cooling of water droplets impinging onto heated surfaces can be used to identify spray cooling mechanisms. Droplet impingement dynamics and evaporation are simulated using the presented numerical model. Volume-of-fluid method is used in the model to track the free surface. The contact line dynamics was predicted from a dynamic contact angle model with the evaporation rate predicted by a kinetic theory model. A species transport equation was solved in the gas phase to describe the vapor convection and diffusion. The numerical model was validated by experimental data. The physical effects including the contact angle hysteresis and the thermocapillary effect are analyzed to offer guidance for future numerical models of droplet impingement cooling. The effects of various parameters including surface wettability, surface temperature, droplet velocity, droplet size, and droplet temperature were numerically studied from the standpoint of spray cooling. The numerical simulations offer profound analysis and deep insight into the spray cooling heat transfer mechanisms. PMID:27531256

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

    NASA Astrophysics Data System (ADS)

    Feddema, Rick

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

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

    NASA Technical Reports Server (NTRS)

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

    1982-01-01

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

  19. Diesel engine emissions and combustion predictions using advanced mixing models applicable to fuel sprays

    NASA Astrophysics Data System (ADS)

    Abani, Neerav; Reitz, Rolf D.

    2010-09-01

    An advanced mixing model was applied to study engine emissions and combustion with different injection strategies ranging from multiple injections, early injection and grouped-hole nozzle injection in light and heavy duty diesel engines. The model was implemented in the KIVA-CHEMKIN engine combustion code and simulations were conducted at different mesh resolutions. The model was compared with the standard KIVA spray model that uses the Lagrangian-Drop and Eulerian-Fluid (LDEF) approach, and a Gas Jet spray model that improves predictions of liquid sprays. A Vapor Particle Method (VPM) is introduced that accounts for sub-grid scale mixing of fuel vapor and more accurately and predicts the mixing of fuel-vapor over a range of mesh resolutions. The fuel vapor is transported as particles until a certain distance from nozzle is reached where the local jet half-width is adequately resolved by the local mesh scale. Within this distance the vapor particle is transported while releasing fuel vapor locally, as determined by a weighting factor. The VPM model more accurately predicts fuel-vapor penetrations for early cycle injections and flame lift-off lengths for late cycle injections. Engine combustion computations show that as compared to the standard KIVA and Gas Jet spray models, the VPM spray model improves predictions of in-cylinder pressure, heat released rate and engine emissions of NOx, CO and soot with coarse mesh resolutions. The VPM spray model is thus a good tool for efficiently investigating diesel engine combustion with practical mesh resolutions, thereby saving computer time.

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

    SciTech Connect

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

    2013-10-01

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

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

    NASA Technical Reports Server (NTRS)

    Rothrock, A M; Waldron, C D

    1937-01-01

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

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

    NASA Astrophysics Data System (ADS)

    Hackett, Charles Marcou

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

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

    NASA Technical Reports Server (NTRS)

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

    1988-01-01

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

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

    NASA Technical Reports Server (NTRS)

    Harstad, K.; Bellan, J.

    1991-01-01

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

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

    NASA Technical Reports Server (NTRS)

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

    1984-01-01

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

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

    NASA Technical Reports Server (NTRS)

    Rothrock, A M; Marsh, E T

    1931-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-06-01

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

  8. A computational study of droplet evaporation with fuel vapor jet ejection induced by localized heat sources

    NASA Astrophysics Data System (ADS)

    Sim, Jaeheon; Im, Hong G.; Chung, Suk Ho

    2015-05-01

    Droplet evaporation by a localized heat source under microgravity conditions was numerically investigated in an attempt to understand the mechanism of the fuel vapor jet ejection, which was observed experimentally during the flame spread through a droplet array. An Eulerian-Lagrangian method was implemented with a temperature-dependent surface tension model and a local phase change model in order to effectively capture the interfacial dynamics between liquid droplet and surrounding air. It was found that the surface tension gradient caused by the temperature variation within the droplet creates a thermo-capillary effect, known as the Marangoni effect, creating an internal flow circulation and outer shear flow which drives the fuel vapor into a tail jet. A parametric study demonstrated that the Marangoni effect is indeed significant at realistic droplet combustion conditions, resulting in a higher evaporation constant. A modified Marangoni number was derived in order to represent the surface force characteristics. The results at different pressure conditions indicated that the nonmonotonic response of the evaporation rate to pressure may also be attributed to the Marangoni effect.

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

    SciTech Connect

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

    1991-07-01

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

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

    SciTech Connect

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

    1991-07-01

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

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

    NASA Astrophysics Data System (ADS)

    Khan, Mohammed N.; Shamim, Tariq

    2014-08-01

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

  12. Analysis of a High Velocity Oxygen-Fuel (HVOF) thermal spray torch. Part 2, Computational results

    SciTech Connect

    Oberkampf, W.L.; Talpallikar, M.

    1993-12-31

    The fluid dynamics inside and outside a High Velocity Oxygen-Fuel (HVOF) torch are analyzed using computational fluid dynamic (CFD) techniques. The thermal spray device analyzed is similar to a Metco Diamond Jet torch with powder injection. The spray nozzle is axisymmetric with powder injected on the centerline, premixed fuel and oxygen fed from an annulus, and air cooling injected along the interior surface of the aircap choked flow conditions occur at the exit of the aircap and a supersonic, under-expanded jet develops externally. The details of the CFD simulation are given in a companion paper. This paper describes the general gas dynamic features of HVOF spraying and then gives a detailed discussion of the computational predictions of the present analysis. The gas velocity, temperature, pressure and Mach number distributions are presented for various locations inside and outside the torch. Characteristics of the metal spray particle velocity, temperature, Mach number, trajectory, and phase state (solid or liquid) are also presented and discussed. Extensive numerical flow visualization is provided to show flow features such as mixing layers, shock waves, and expansion waves.

  13. Two-Phase PIV: Fuel-Spray Interaction with Surrounding Air

    NASA Astrophysics Data System (ADS)

    Dankers, Stefan; Gotthardt, Mark; Stengler, Thomas; Ohmstede, Gerhard; Hentschel, Werner

    The demand for improvement of combustion-engine processes leads to a great need for detailed experimental information about the complicated processes of injection, breakup and propagation of the fuel jet and the vaporization of the fuel. Thus, in the presented work it was the aim to visualize the air flow that is induced by the injected fuel jet and also to explore the air entrainment into the fuel spray. This was done using two-phase PIV (particle image velocimetry). The fuel jet was illuminated with a Nd:YAG PIV-laser and PIV analysis was done by simply measuring the elastically scattered light of the fuel droplets. For the investigation of the surrounding air propylene-carbonate doped with DCM-dye was dispersed and the droplets were added to the continuous gas flow upstream of the chamber. Scattered and fluorescence signals, respectively, were detected perpendicular to the laser sheet with a CCD camera. To detect the gas flow, the scattered light from the liquid fuel was suppressed by an OG 590 longpass filter glass that transmits the fluorescence signal of the DCM-dye. It was possible to measure both the fuel jet and the gas flow in the presence of the fuel spray and a clear separation of the two phases could be achieved. In both (fuel and air) vector pictures corresponding vortices could be identified near the air/fuel boundary layer. Maximum velocities in the jet are depending on the operation conditions up to 150ms-1 and the gas flow has typically a velocity of 1 to 10ms-1. In the region next to the injector the air was pressed away during the injection. After the end of the injection a strong fast air entrainment flow into this region can be observed that compensates the pressure difference.

  14. Heat Transfer to Fuel Sprays Injected into Heated Gases

    NASA Technical Reports Server (NTRS)

    Selden, Robert F; Spencer, Robert C

    1938-01-01

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

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

    NASA Technical Reports Server (NTRS)

    Rothrock, A M; Spencer, R C

    1935-01-01

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

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

    SciTech Connect

    Oberkampf, W.L.; Talpallikar, M.

    1994-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2011-07-01

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

  18. Modeling the influence of precursor volatility and molecular structure on secondary organic aerosol formation using evaporated fuel experiments

    NASA Astrophysics Data System (ADS)

    Jathar, S. H.; Donahue, N. M.; Adams, P. J.; Robinson, A. L.

    2013-09-01

    We use SOA production data from an ensemble of evaporated fuels to test various SOA formation models. Except for gasoline, traditional SOA models focusing exclusively on volatile species in the fuels under-predict the observed SOA formation. These models can be improved dramatically by accounting for lower volatility species, but at the cost of a large set of free parameters. In contrast, a SOA model based only on the volatility of the precursor, starting with the volatility distribution of the evaporated fuels and optimized for the volatility reduction of first-generation products, reasonably reproduces the observed SOA formation with relatively few free parameters. The exceptions are exotic fuels such as Fischer-Tropsch fuels that expose the central assumption of the volatility based model that most emissions consist of complex mixtures displaying reasonably average behavior. However, for the vast majority of fuels, the volatility based model performs well.

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

    PubMed

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

    2015-12-28

    Modern diesel injectors operate at very high injection pressures of about 2000 bar resulting in injection velocities as high as 700 m/s near the nozzle outlet. In order to better predict the behavior of the atomization process at such high pressures, high-resolution spray images at high repetition rates must be recorded. However, due to extremely high velocity in the near-nozzle region, high-speed cameras fail to avoid blurring of the structures in the spray images due to their exposure time. Ultrafast imaging featuring ultra-short laser pulses to freeze the motion of the spray appears as an well suited solution to overcome this limitation. However, most commercial high-energy ultrafast sources are limited to a few kHz repetition rates. In the present work, we report the development of a custom-designed picosecond fiber laser generating ∼ 20 ps pulses with an average power of 2.5 W at a repetition rate of 8.2 MHz, suitable for high-speed imaging of high-pressure fuel jets. This fiber source has been proof tested by obtaining backlight images of diesel sprays issued from a single-orifice injector at an injection pressure of 300 bar. We observed a consequent improvement in terms of image resolution compared to standard white-light illumination. In addition, the compactness and stability against perturbations of our fiber laser system makes it particularly suitable for harsh experimental conditions. PMID:26832004

  20. Fuel spray simulation with two-fluid nozzles

    NASA Astrophysics Data System (ADS)

    Ingebo, Robert D.

    1989-01-01

    Two-phase interacting flow inside a two-fluid fuel atomizer was investigated and a correction of aerodynamic and liquid-surface forces with characteristic drop diameter was obtained for liquid-jet breakup in Mach 1 gas flow. Nitrogen gas mass-flux was varied from 6 to 50 g/sq cm sec by using four differently sized two-fluid atomizers with nozzle diameters varying from 0.32 to 0.56 cm. The correlation was derived by using the acoustic gas velocity, V sub c, as a basic parameter in defining and evaluating the dimensionless product of the Weber (We) and Reynolds (Re) numbers. By using the definition of WeRe, it was found that the ratio of orifice diameter to Sauter mean drop diameter could be correlated with the dimensionless ratio WeRe and the gas to liquid density ratio.

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

    NASA Astrophysics Data System (ADS)

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

    2008-08-01

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

  2. Erosion Resistance of High Velocity Oxy-Fuel WC-Co-Cr Thermal Spray Coatings

    NASA Astrophysics Data System (ADS)

    Imeson, Chris

    Thermal spray coatings have been incorporated in oil and gas extraction efforts for many years. Recently, High Velocity Oxy-Fuel (HVOF) has become increasingly incorporated where erosive environments are present. This study investigates the microstructural and mechanical properties of HVOF WC-Co-Cr coatings deposited at SharkSkin Coatings ltd. The deposited coatings exhibited a low porosity with high adhesion strength, hardness, and superior erosion resistance. In this study, a recirculating solid particle erosion testing machine was designed and fabricated to simulate an erosive environment on a laboratory scale. This study was also aimed at improving microstructures and mechanical properties of the coatings by modifying the two coating deposition parameters e.g. standoff and pre-cycle heating. It was determined that pre-spray substrate heating negatively affected the coatings microstructures e.g. porosity, while reducing the stand-off distance positively influenced the coating microstructures and mechanical properties, e.g. erosion resistance.

  3. Numerical simulation of the flow field and fuel sprays in an IC engine

    NASA Technical Reports Server (NTRS)

    Nguyen, H. L.; Schock, H. J.; Ramos, J. I.; Carpenter, M. H.; Stegeman, J. D.

    1987-01-01

    A two-dimensional model for axisymmetric piston-cylinder configurations is developed to study the flow field in two-stroke direct-injection Diesel engines under motored conditions. The model accounts for turbulence by a two-equation model for the turbulence kinetic energy and its rate of dissipation. A discrete droplet model is used to simulate the fuel spray, and the effects of the gas phase turbulence on the droplets is considered. It is shown that a fluctuating velocity can be added to the mean droplet velocity every time step if the step is small enough. Good agreement with experimental data is found for a range of ambient pressures in Diesel engine-type microenvironments. The effects of the intake swirl angle in the spray penetration, vaporization, and mixing in a uniflow-scavenged two-stroke Diesel engine are analyzed. It is found that the swirl increases the gas phase turbulence levels and the rates of vaporization.

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

    SciTech Connect

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

    2009-06-15

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

  5. Development of methanol evaporation plate to reduce methanol crossover in a direct methanol fuel cell

    NASA Astrophysics Data System (ADS)

    Zhang, Ruiming

    This research focuses on methanol crossover reduction in direct methanol fuel cells (DMFC) through separating the methanol vapor from its liquid phase and feeding the vapor passively at low temperature range. Membrane electrode assemblies (MEAs) were fabricated by using commercial available membrane with different thickness at different anode catalyst loading levels, and tested under the operating conditions below 100°C in cell temperature and cathode exit open to ambient pressure. Liquid methanol transport from the anode through the membrane into cathode ("methanol crossover") is identified as one of the major efficiency losses in a DMFC. It is known that the methanol crossover rate in the vapor phase is much lower than in liquid phase. Vapor feed can be achieved by heating the liquid methanol to elevated temperatures (>100°C), but other issues limit the performance of the cell when operating above 100°C. High temperature membranes and much more active cathode catalyst structures are required, and a complex temperature control system must be employed. However, methanol vapor feed can also occur at a lower temperature range (<100°C) by separating its vapor from the liquid phase by evaporation through a porous body. The methanol crossover with this vapor feed mode is lower compared with the direct liquid methanol feed. A new method of using a methanol evaporation plate (MEP) to separate the vapor from its liquid phase to reduce the liquid methanol crossover at low temperature range is developed. A MEP plays the roles of liquid/vapor methanol phase separation and evaporation in a DMFC. The goal of this study is to develop a MEP with the proper properties to achieve high methanol phase separation efficiency and fast methanol evaporation rate over a wide range of temperature, i.e., from room temperature up to near boiling temperature (100°C). MEP materials were selected and characterized. MEPs made from three different types were tested extensively with different

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

    PubMed

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

    2003-06-01

    The large presence of aromatic compounds in distillate fossil fuels should allow, in line of principle, to follow the fuel consumption and/or the presence of unburned fuel in a high temperature environment like a burner or the exhaust of combustion systems by exploiting the high fluorescence emission of aromatic fuel components. To this aim an UV-excited fluorescence source has to be used since the aromatic fuel components are strongly fluorescing in the UV region of the emission spectrum. In this work UV-excited laser induced fluorescence (LIF) diagnostics was applied to spray flames of kerosene in order to follow the fuel consumption and the formation of aromatic species. A strong UV signal was detected in the spray region of the flame that presented a shape similar to that found in the LIF spectra preliminary measured on the cold spray and in the room-temperature fluorescence of fuel solutions. The decrease of UV signal along the spray flame region was associated to the consumption of the fuel, but more difficult seems to be the attribution of a broad visible emission, that is present downstream of the flame. The visible emission feature could be assigned to flame-formed PAH species contained in the high molecular weight species, hypothesizing that their fluorescence spectra are shifted toward the visible for effect of the high temperature flame environment. PMID:12718975

  7. Effects of Air-Fuel Spray and Flame Formation in a Compression-Ignition Engine

    NASA Technical Reports Server (NTRS)

    Rothrock, A M; Waldron, C D

    1937-01-01

    High-speed motion pictures were taken at the rate of 2,500 frames per second of the fuel spray and flame formation in the combustion chamber of the NACA combustion apparatus. The compression ratio was 13.2 and the speed 1,500 revolutions per minute. An optical indicator was used to record the time-pressure relationship in the combustion chamber. The air-fuel ratio was varied from 10.4 to 365. The results showed that as the air-fuel ratio was increased definite stratification of the charge occurred in the combustion chamber even though moderate air flow existed. The results also showed the rate of vapor diffusion to be relatively slow.

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

    NASA Technical Reports Server (NTRS)

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

    1982-01-01

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

  9. Influence of spray additives on droplet evaporation and residual patterns on wax and wax-free surfaces

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Evaporation time and wetted area of single droplets sizing from 246 to 886 µm at relative humidity (RH) ranging from 30 to 90% were measured with sequential images under controlled laboratory conditions. Droplets were placed inside an environmental-controlled chamber under a stereoscope and a high ...

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

    SciTech Connect

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

    1995-09-01

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

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

    NASA Technical Reports Server (NTRS)

    Beardsley, E G

    1928-01-01

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

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

    SciTech Connect

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

    1993-12-31

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

  13. Effect of orifice length-diameter ratio on fuel sprays for compression-ignition engines

    NASA Technical Reports Server (NTRS)

    Gelalles, A G

    1933-01-01

    Experimental results on the effect of the length-diameter ratio of the orifice on the spray characteristics, together with a brief analysis of the factors affecting these characteristics, are presented in this report. The length-diameter ratios tested ranged from 0.5 to 10; the orifice diameters from 0.008 to 0.040 inch; and the injection pressures from 2,000 to 8,000 pounds per square inch. The density of the air into which the fuel was discharged was varied from 0.38 to 1.35 pounds per cubic foot.

  14. Particle melting behavior during high-velocity oxygen fuel thermal spraying

    NASA Astrophysics Data System (ADS)

    He, J.; Ice, M.; Lavernia, E.

    2001-03-01

    Particle melting behavior during high-velocity oxygen fuel (HVOF) thermal spraying was investigated using Inconel 625 powders. The powder characteristics and coating properties were investigated using scanning electron microscopy (SEM), x-ray, and microhardness studies. Results indicated that the volume fraction of unmelted particles in the coatings was dependent on the proportion of powder within a specified size range, in these experiments, 30 to 50 µm. This particle size range was primarily determined by the particle temperature, which was measured during spraying. Particle temperature significantly decreased as particle size increased. The microhardness values for the coatings containing unmelted particles were predicted by a simple rule-of-mixtures equation for the case of a low volume fraction of unmelted particles. However, for the condition of high volume fraction of unmelted particles, the measured microhardness values did not compare favorably with the calculated values, probably due to the presence of porosity, which occurred in the form of voids found among unmelted particles. The microstructure and characteristics of the feedstock powder were retained in the corresponding coating under certain spray conditions.

  15. In vitro performance of ceramic coatings obtained by high velocity oxy-fuel spray.

    PubMed

    Melero, H; Garcia-Giralt, N; Fernández, J; Díez-Pérez, A; Guilemany, J M

    2014-01-01

    Hydroxyapatite coatings obtained by plasma-spraying have been used for many years to improve biological performance of bone implants, but several studies have drawn attention to the problems arising from high temperatures and the lack of mechanical properties. In this study, plasma-spraying is substituted by high velocity oxy-fuel (HVOF) spray, with lower temperatures reached, and TiO2 is added in low amounts to hydroxyapatite in order to improve the mechanical properties. Four conditions have been tested to evaluate which are those with better biological properties. Viability and proliferation tests, as well as differentiation assays and morphology observation, are performed with human osteoblast cultures onto the studied coatings. The hydroxyapatite-TiO2 coatings maintain good cell viability and proliferation, especially the cases with higher amorphous phase amount and specific surface, and promote excellent differentiation, with a higher ALP amount for these cases than for polystyrene controls. Observation by SEM corroborates this excellent behaviour. In conclusion, these coatings are a good alternative to those used industrially, and an interesting issue would be improving biological behaviour of the worst cases, which in turn show the better mechanical properties. PMID:25201392

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

    NASA Technical Reports Server (NTRS)

    Shuen, J. S.

    1985-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-09-01

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

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

    NASA Technical Reports Server (NTRS)

    Sarv, H.

    1985-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-11-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-11-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

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

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

    NASA Astrophysics Data System (ADS)

    Afshar, Ali

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

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

    NASA Astrophysics Data System (ADS)

    Fleetwood, James D.

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

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

    SciTech Connect

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

    1993-12-31

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

  5. Semi-automated structural characterisation of high velocity oxy fuel thermally sprayed WC-Co based coatings

    NASA Astrophysics Data System (ADS)

    Fay, M. W.; Han, Y.; McCartney, G.; Korpiola, K.; Brown, P. D.

    2008-08-01

    The application of an automated procedure for the rapid assessment of selected area electron diffraction patterns is described. Comparison with complementary EDX spectra has enabled the thermal decomposition reactions within high velocity oxy-fuel thermally sprayed WC-Co coatings to be investigated.

  6. Aerodynamic study on supersonic flows in high-velocity oxy-fuel thermal spray process

    NASA Astrophysics Data System (ADS)

    Katanoda, Hiroshi; Matsuoka, Takeshi; Kuroda, Seiji; Kawakita, Jin; Fukanuma, Hirotaka; Matsuo, Kazuyasu

    2005-06-01

    To clarify the characteristics of gas flow in high velocity oxy-fuel (HVOF) thermal spray gun, aerodynamic research is performed using a special gun. The gun has rectangular cross-sectional area and sidewalls of optical glass to visualize the internal flow. The gun consists of a supersonic nozzle with the design Mach number of 2.0 followed by a straight passage called barrel. Compressed dry air up to 0.78 MPa is used as a process gas instead of combustion gas which is used in a commercial HVOF gun. The high-speed gas flows with shock waves in the gun and jets are visualized by schlieren technique. Complicated internal and external flow-fields containing various types of shock wave as well as expansion wave are visualized.

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

    SciTech Connect

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

    2011-01-15

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

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

    NASA Technical Reports Server (NTRS)

    Rothrock, A M

    1931-01-01

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

  9. NOx formation from the combustion of monodisperse n-heptane sprays doped with fuel-nitrogen additives

    NASA Technical Reports Server (NTRS)

    Sarv, Hamid; Cernansky, Nicholas P.

    1989-01-01

    A series of experiments with simulated synthetic fuels were conducted in order to investigate the effect of droplet size on the conversion of fuel-nitrogen to NOx. Pyridine and pyrrole were added to n-heptane as nitrogen-containing additives and burned as monodisperse fuel droplets under various operating conditions in a spray combustion facility. The experimental results indicate that under stoichiometric and fuel-rich conditions, reducing the droplet size increases the efficiency of fuel-N conversion to NOx. This observation is associated with improved oxidation of the pyrolysis fragments of the additive by better oxygen penetration through the droplet flame zone. The dominant reactions by which fuel-N is transformed to NOx were also considered analytically by a premixed laminar flame code. The calculations are compared to the small droplet size results.

  10. Liquid spray cooling of a heated surface

    NASA Technical Reports Server (NTRS)

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

    1981-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-09-01

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

  12. Effect of Nozzle Design on Fuel Spray and Flame Formation in a High-Speed Compression-Ignition Engine

    NASA Technical Reports Server (NTRS)

    Rothrock, A M; Waldron, C D

    1937-01-01

    Fuel was injected from different type of injection nozzles into the combustion chamber of the NACA combustion apparatus, operated as a compression-ignition engine. High speed motion pictures were taken of the fuel sprays and combustion. Single-orifice nozzles of 0.008, 0.020, and 0.040 inch diameter, and multiorifice nozzles having 2, 6, and 16 orifices were tested. Nozzles having impinging jets and slit orifices were also included. The photographs indicate that the rate of vapor diffusion from the spray is comparatively slow and that this slow rate of diffusion for combustion chambers with little or no air flow prevents the compression-ignition engine from giving the high performance inherent in the high compression ratios. The sprays from the multiorifice nozzles destroyed the air movement to a greater extent than did those from single orifice nozzles. It is concluded that high performance cannot be realized until the methods of distributing the fuel are improved by means of the injection-nozzle design, air flow, or both.

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

    NASA Astrophysics Data System (ADS)

    Wang, Xiaoguang; Song, Qiuzhi; Yu, Zhiyi

    2016-02-01

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

  14. Characterization of sprays

    NASA Astrophysics Data System (ADS)

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

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

  15. Characterization of sprays

    NASA Technical Reports Server (NTRS)

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

    1984-01-01

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

  16. Titanium dioxide reinforced hydroxyapatite coatings deposited by high velocity oxy-fuel (HVOF) spray.

    PubMed

    Li, H; Khor, K A; Cheang, P

    2002-01-01

    Hydroxyapatite (HA) coatings with titania addition were produced by the high velocity oxy-fuel (HVOF) spray process. Mechanical properties of the as-sprayed coatings in terms of adhesive strength, shear strength and fracture toughness were investigated to reveal the effect of the titania reinforcement on HA. Qualitative phase analysis with X-ray diffraction (XRD) showed that mutual chemical reaction between TiO2 and HA, that formed CaTiO3 occurred during coating formation. Differential scanning calorimetry (DSC) analysis of the starting powders showed that the mutual chemical reaction temperature was approximately 1410 degrees C and the existence of TiO2 can effectively inhibit the decomposition of HA at elevated temperatures. The positive influence of TiO2 addition on the shear strength was revealed. The incorporation of 10 vol% TiO2 significantly improved the Young's modulus of HA coatings from 24.82 (+/- 2.44) GPa to 43.23 (+/- 3.20) GPa. It decreased to 38.51 (+/- 3.65) GPa as the amount of TiO2 increased to 20 vol%. However, the addition of TiO2 has a negative bias on the adhesive strength of HA coatings especially when the content of TiO2 reached 20 vol%. This is attributed to the weak chemical bonding and brittle phases existing at the splats' interface that resulted from mutual chemical reactions. The fracture toughness exhibited values of 0.48 (+/- 0.08) MPa m0.5, 0.60 (+/- 0.07) MPa m0.5 and 0.67 (+/- 0.06) MPa m0.5 for the HA coating, 10 vol% TiO2 blended HA coating and 20 vol% TiO2 blended HA coating respectively. The addition of TiO2 in HA coating with the amount of less than 20 vol% is suggested for satisfactory toughening effect in HVOF HA coating. PMID:11762858

  17. Hot air drum evaporator

    DOEpatents

    Black, Roger L.

    1981-01-01

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

  18. Controllable p- and n-type doping of poly[2-methoxy-5-(2‧-methyl-hexyloxy)-p-phenylenevinylene] films prepared by evaporative spray deposition using ultradilute solution

    NASA Astrophysics Data System (ADS)

    Sakiyama, Shin; Mizutani, Naoki; Fujita, Katsuhiko

    2016-04-01

    Evaporative spray deposition using an ultradilute solution (ESDUS) enables polymer film preparation using diluted solution at ppm levels. We used this method for p- and n-type doping of poly[2-methoxy-5-(2‧-methyl-hexyloxy)-p-phenylenevinylene] (MEH-PPV), which is a bipolar-transport polymer semiconductor. The device characteristics indicated a drastic improvement of conductivity with carrier mobility. Moreover, the doping efficiency was higher than 15% in both p- and n-type doping owing to the wide dopant dispersion realized by the ESDUS technique.

  19. Deposition of solid oxide fuel cell electrodes by solution precursor plasma spray

    NASA Astrophysics Data System (ADS)

    Wang, Youliang

    Porous La1-xSrxMnO3 (LSM) perovskite cathodes and Yttria Stabilized Zirconia (YSZ)-Nickel (Ni) anodes were successfully deposited by direct current arc solution precursor plasma spray (DC-SPPS), in which a solution precursor of the product material was injected into DC plasma jet. The deposition mechanisms, such as the changes in the solution precursor with the increase of temperature and the evolution of the droplet as it moved along the plasma jet, as well as the impact of the synthesized particles onto the substrate, were investigated. The effects of processing parameters on the microstructure and phase composition of the fabricated LSM cathode and Ni-YSZ anode were examined systematically using TGA/TDA, XRD and SEM. Coating deposition efficiencies and porosities as a function of processing parameters were analyzed by statistical experimental design techniques, based on which the deposition processes were optimized. In addition, the hardness and electrical resistance of the fabricated coatings were measured. From the theoretical and experimental analyses conducted, a comprehensive description of the DC-SPPS process was developed. The precursor solution droplets undergo breakup; solvent evaporation and precursor salt precipitation and crystallization; precursor salt melting and decomposition; nucleation and growth of particles of the product phase; agglomeration, sintering, and perhaps melting of these particles; and impact onto the substrate. The breakup of droplets can only occur in the short period of time after the droplets are injected into the plasma jet. Agglomeration of droplets or particles may occur at any point along the plasma plume. This work has clearly established: (a) the critical importance of droplet breakup and the agglomeration of precursors or synthesized particles in-flight in the plasma jet in determining the structure of the deposited coating, and (b) the basis of the low deposition efficiencies obtained in DC-SPPS. The microstructure and

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

    NASA Astrophysics Data System (ADS)

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

    2004-12-01

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

  1. Modeling of Two-Phase Flow and Heat Transfer in Low-Temperature Oxygen-Fuel Spray Process

    NASA Astrophysics Data System (ADS)

    Shan, Y. G.; Shen, C. H.; Jia, L. B.; Mostaghimi, J.

    2014-01-01

    The low-temperature oxygen-fuel (LTOF) spray is a modification of high velocity oxygen fuel spray. In this process, the high-temperature gas is accelerated to supersonic speed through a Laval nozzle followed by a straight barrel. By injecting room temperature gas into the mixing chamber, the temperature of the gas can be controlled in a range of about 1000-2500 K, so that some oxygen and temperature-sensitive materials, such as titanium and copper, can avoid oxidation or decomposition during the spraying process. The purpose of this paper is to establish a 2-D mathematical model to simulate the supersonic gas dynamics and particles behavior in LTOF process. The temperature and velocity of the flow fields, and the trajectory and heating of in-flight particles are predicted for different operating parameters. The model is validated by experimental data in the literature. Effects of the mixing gas flow rates, particle sizes, and injection conditions on this process were investigated as well.

  2. Modeling the effects of drop drag and breakup on fuel sprays

    NASA Astrophysics Data System (ADS)

    Liu, Alex B.; Mather, Daniel; Reitz, Rolf D.

    1993-03-01

    Spray models were evaluated using experimentally measured trajectories and drop sizes of single drops injected into a high relative velocity gas flow. The computations were made using a modified version of the KIVA-2 code. It was found that the drop drag coefficient and the drop breakup time model constant had to be adjusted in order to match the measurements. Based on these findings, a new drop drag submodel is proposed in which the drop drag coefficient changes dynamically with the flow conditions. The model accounts for the effects of drop distortion and oscillation due to the relative motion between the drop and the gas. The value of the drag coefficient varies between the two limits of that of a rigid sphere (no distortion) and that of a disk (maximum distortion). The modified model was also applied to diesel sprays. The results show that the spray tip penetration is relatively insensitive to the value used for the drop drag coefficient. However, the distribution of drop sizes within sprays is influenced by drop drag. This is due to the fact that changes in drop drag produce changes in the drop-gas relative velocity. This, in turn, causes changes in the spray drop size through the drop breakup and coalescence processes. The changes occur in such a way that the net effect on the spray penetration is small over the tested ranges of conditions. These results emphasize that measurements of spray penetration are not sufficient to test and produce improved spray models. Instead, local measurements of drop size and velocity are needed to develop accurate spray models.

  3. Effect of High-Velocity Oxy-Fuel (HVOF) Thermal Spraying on Physical and Mechanical Properties of Type 316 Stainless Steel

    SciTech Connect

    Terry C. Totemeier

    2005-09-01

    Data on the microstructural, physical, and mechanical characteristics of high-velocity oxygen-fuel (HVOF)-sprayed type 316 stainless steel coatings are presented and compared with properties of wrought 316 stainless steel. Coatings were prepared at three different spray particle velocities; coating characteristics are presented as a function of velocity. The coatings had relatively low porosity and oxide contents and were significantly harder than annealed, wrought 316 stainless steel. The hardness difference is primarily attributed to high dislocation densities resulting from peening imparted by high-velocity spray particles. The coating hardness increased with increasing spray particle velocity, reflecting increased peening effects. The elastic modulus of the coatings was essentially identical to wrought material. The mean coefficient of thermal expansion of as-sprayed coatings was lower than wrought material, but the expansion of annealed coatings matched the wrought behavior.

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

    NASA Astrophysics Data System (ADS)

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

    2011-03-01

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

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

    NASA Technical Reports Server (NTRS)

    Prok, George M

    1957-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

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

  7. Improved Orifice Plate for Spray Gun

    NASA Technical Reports Server (NTRS)

    Cunningham, W.

    1986-01-01

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

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

    NASA Astrophysics Data System (ADS)

    Hu, Chih-Chieh

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

  9. Evaporative precooling unit

    SciTech Connect

    Rogers, A.R.

    1988-03-15

    In combination with a refrigeration unit, an evaporative heat exchange unit for precooling an air stream traveling toward and over the condensing coil of the refrigeration unit is described. The heat exchange unit includes: (a) a frame, (b) a porous heat transfer pad mounted in the frame; (c) nozzle means carried on the frame for directing a spray mist forwardly of the heat transfer pad, the spray mist emitted from the nozzle means initially traveling in a direction of travel such that the mist will not contact the porous heat transfer pad; (d) means mounted on the frame for causing the turbulent intermixing of the air stream with the spray mist prior to the air stream passing through the porous heat transfer pad; and (e) means for controlling the quantity of water emitted by the nozzle means such that substantially all of the spray mist is intermixed with the air stream prior to the air stream passing through the heat transfer pad.

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

    NASA Technical Reports Server (NTRS)

    Beardsley, Edward G

    1928-01-01

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

  11. Vacuum Plasma Spray of Cu-8Cr-4Nb for Advanced Liquid-Fuel Combustion Chambers

    NASA Technical Reports Server (NTRS)

    Zimmerman, F.; Elam, S.; Ellis, D.; Miller, H.; McKechnie, T.; Hickman, R.

    2001-01-01

    Vacuum plasma spray (VPS) formed Cu-8Cr-4Nb alloy, with low oxygen, exhibits higher strength at room and elevated temperature than material formed by extrusion. The VPS formed material exhibits slightly lower ductility than the extruded material. VPS forming of Cu-8Cr-4Nb can be used to produce near net structures with mechanical properties comparable to current extruded material.

  12. On the gas dynamics of HVOF thermal sprays. [HVOF (High-Velocity Oxy-Fuel)

    SciTech Connect

    Hackett, C.M.; Settles, G.S.; Miller, J.D.

    1993-01-01

    An experimental study has been performed on the gas dynamic aspects of the HVOF thermal spray process. A commercially-available HVOF gun (Hobart Tafa JP-5000) is used in this study. Optical diagnostic techniques including microsecond-exposure schlieren and shadowgraph imaging are applied to visualize the hot supersonic jet produced by this equipment without any particle injection. Rapid turbulent mixing of the jet with the surrounding atmosphere is observed, which is an issue of concern in coating quality because of the possibility of oxidation of the sprayed particles. This mixing appears principally to be a function of the density ratio between the hot jet and the cold atmosphere, rather than depending upon the combustion-chamber pressure or barrel length. The supersonic core of the HVOF jet dissipates rapidly due to the, mixing, so that the jet is no longer supersonic when it impinges upon the target surface being sprayed. Secondary issues also observed in this study include strong jet-noise radiation from the HVOF plume and the entrainment and induced bulk motion of the surrounding air. All these issues have a background in the field of gas dynamics which has not been previously applied to thermal spray technology.

  13. Continuous synthesis of graphene sheets by spray pyrolysis and their use as catalysts for fuel cells.

    PubMed

    Zou, Biao; Wang, Xiao Xia; Huang, Xin Xin; Wang, Jian Nong

    2015-01-14

    Graphene sheets (GNS) were synthesized continuously by spray pyrolysis of iron carbonyl and pyridine. The Pt catalyst supported on GNS exhibited excellent durability for oxygen reduction reaction (ORR). The GNS, when used as a metal-free catalyst for ORR, showed performance even better than the commercial Pt/C catalyst. PMID:25421428

  14. On the combustion of a laminar spray

    NASA Technical Reports Server (NTRS)

    Levy, Yeshayahou; Bulzan, Daniel L.

    1993-01-01

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

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

    PubMed

    Kawahara, Nobuyuki; Tsuboi, Kazuya; Tomita, Eiji

    2014-01-13

    The behaviors of laser-induced plasma and fuel spray were investigated by visualizing images with an ultra-high-speed camera. Time-series images of laser-induced plasma in a transient spray were visualized using a high-speed color camera. The effects of a shockwave generated from the laser-induced plasma on the evaporated spray behavior were investigated. The interaction between a single droplet and the laser-induced plasma was investigated using a single droplet levitated by an ultrasonic levitator. Two main conclusions were drawn from these experiments: (1) the fuel droplets in the spray were dispersed by the shockwave generated from the laser-induced plasma; and (2) the plasma position may have shifted due to breakdown of the droplet surface and the lens effect of droplets. PMID:24921999

  16. The effects of fuel additives on alcohol exhaust and evaporative emissions

    SciTech Connect

    Espinola, S.A.; Nebolon, J.F.; Pepley, R.K.; Tamura, A.T.

    1982-06-01

    As a result of the past decade of evaluation, the technical feasibility of alcohols as extenders and substitutes for gasoline in spark ignited engines has been generally established both with regards to performance and emissions. One of the problem areas is cold starting and warm-up driveability. High heats of vaporation and low vapor pressures at low temperatures of the alcohols are the cause of these problems. Current solutions include electric heating, separate fuel supply, and the addition of volatile components to the alcohol such as gasoline, isopentane and dimethyl ether. The alcohols typically are as clean burning or cleaner burning than gasoline. The effect on regulated emissions from using additives needs to be included in the evaluation of cold starting additives. This assessment should include consideration of total hydrocarbons as well as detailed hydrocarbons for photochemical impact and flame ionization detector responsivity. This paper presents an examination of the emissions evidence from two three-way catalysts equipped vehicles: A 1980 Ford Pinto and a 1981 Volkswagon Rabbit. The test fuels were neat methanol and a 5.5% (by mass) isopentane/methanol blend.

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

    NASA Astrophysics Data System (ADS)

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

    2016-05-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-11-01

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

  19. Tribological Properties of Hard Metal Coatings Sprayed by High-Velocity Air Fuel Process

    NASA Astrophysics Data System (ADS)

    Lyphout, C.; Sato, K.; Houdkova, S.; Smazalova, E.; Lusvarghi, L.; Bolelli, G.; Sassatelli, P.

    2016-01-01

    Lowering the thermal energy and increasing the kinetic energy of hard metal particles sprayed by the newly developed HVAF systems can significantly reduce their decarburization, and increases the sliding wear and corrosion resistance of the resulting coatings, making the HVAF technique attractive, both economically and environmentally, over its HVOF predecessors. Two agglomerated and sintered feedstock powder chemistries, WC-Co (88/12) and WC-CoCr (86/10/4), respectively, with increasing primary carbides grain size from 0.2 to 4.0 microns, have been deposited by the latest HVAF-M3 process onto carbon steel substrates. Their dry sliding wear behaviors and friction coefficients were evaluated at room temperature via Ball-on-disk (ASTM G99-90) wear tests against Al2O3 counterparts, and via Pin-on-disk (ASTM G77-05) wear tests against modified martensitic steel counterparts in both dry and lubricated conditions. Sliding wear mechanisms, with the formation of wavy surface morphology and brittle cracking, are discussed regarding the distribution and size of primary carbides. Corrosion behaviors were evaluated via standard Neutral Salt Spray, Acetic Acid Salt Spray, accelerated corrosion test, and electrochemical polarization test at room temperature. The optimization of the tribological properties of the coatings is discussed, focusing on the suitable selection of primary carbide size for different working load applications.

  20. Characterization of the bone-like apatite precipitated on high velocity oxy-fuel (HVOF) sprayed calcium phosphate deposits.

    PubMed

    Khor, K A; Li, H; Cheang, P

    2003-02-01

    Bone-like apatite was precipitated on the surface of thermal sprayed calcium phosphate coatings following in vitro incubation in a simulated body fluid. The coatings were initially deposited on titanium alloy substrates by the high velocity oxy-fuel (HVOF) spray technique. Structural characterization and mechanical evaluation of the precipitated apatite layer were conducted. Results showed that the precipitation rate was directly influenced by the local Ca(2+) concentration in the vicinity of the coating's surface and that preferential dissolution of certain phases was found to accelerate the precipitation of the bone-like apatite. The dense precipitates exhibited a competitive Young's modulus value of approximately 120GPa, which was obtained through nanoindentation. This compared favorably to the calcium phosphate matrix. Differences in microstructure at various locations within the layer resulted in altered Young's modulus and microhardness values. Precipitation mechanism investigation was carried out through a comparative experiment. Chemical analysis showed that the precipitation of bone-like apatite on the calcium phosphate coating was quite conceivably a partial diffusion-controlled process. PMID:12485795

  1. Properties of heat-treated calcium phosphate coatings deposited by high-velocity oxy-fuel (HVOF) spray.

    PubMed

    Li, H; Khor, K A; Cheang, P

    2002-05-01

    The influence of crystallization, upon heat treatment, on the properties of high-velocity oxy-fuel (HVOF) sprayed hydroxyapatite (HA) coatings was investigated. The characterization of the HA coating was performed by X-ray diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FTIR). Differential Scanning Calorimeter (DSC) was employed to determine the crystallization temperature of the amorphous phase in an as-sprayed HA coating. The study demonstrated the effect of crystallization on the coating properties by considering the changes in materials chemistry, crystallinity level, and mechanical performance. Results showed that complete crystallization of the amorphous phase occurred at approximately 700 degrees C and the crystallization temperature was dependent on sample heating rate in the DSC test. The changes of ion groups were detected by FTIR, before and after the phase transformation. The crystallization of the coating after annealing at 750 degrees C resulted in a significant increase of the coatings' adhesive strength and shear strength, which attained maximum values 34 +/- 3 and 14.1 -/+ 0.8 MPa, respectively. Young's modulus increased from 21 +/- 1 to 25 +/- 2 GPa. Microhardness measurements confirmed the changes in coating properties. It is also found that the transformation from the amorphous phase has crystalline HA as the only resultant phase detected by XRD. PMID:11962650

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

    SciTech Connect

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

    1995-07-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2009-09-01

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

  4. Soil Evaporation

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Soil evaporation can significantly influence energy flux partitioning of partially vegetated surfaces, ultimately affecting plant transpiration. While important, quantification of soil evaporation, separately from canopy transpiration, is challenging. Techniques for measuring soil evaporation exis...

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-05-01

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

  7. Spray momentum measuring system

    NASA Technical Reports Server (NTRS)

    Sheffield, E. W.

    1971-01-01

    Technique enables accurate prediction of erosion and cavitation produced by fluid spray. Method measures high velocity sprays produced by small orifices. Originally designed to determine oxidizer-injection patterns of liquid fueled rocket engines, technique is used with other liquids, or, with appropriate modification, with gases.

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

    PubMed

    Zigan, Lars; Trost, Johannes; Leipertz, Alfred

    2016-02-20

    This paper reports for the first time, to the best of our knowledge, on the simultaneous imaging of the gas-phase temperature and fuel vapor mass fraction distribution in a direct-injection spark-ignition (DISI) spray under engine-relevant conditions using tracer planar laser-induced fluorescence (TPLIF). For measurements in the spray, the fluorescence tracer 3-pentanone is added to the nonfluorescent surrogate fuel iso-octane, which is excited quasi-simultaneously by two different excimer lasers for two-line excitation LIF. The gas-phase temperature of the mixture of fuel vapor and surrounding gas and the fuel vapor mass fraction can be calculated from the two LIF signals. The measurements are conducted in a high-temperature, high-pressure injection chamber. The fluorescence calibration of the tracer was executed in a flow cell and extended significantly compared to the existing database. A detailed error analysis for both calibration and measurement is provided. Simultaneous single-shot gas-phase temperature and fuel vapor mass fraction fields are processed for the assessment of cyclic spray fluctuations. PMID:26906600

  9. Application of high velocity oxygen fuel flame (HVOF) spraying to fabrication of La0.8Sr0.2Ga0.8Mg0.2O3 electrolyte for solid oxide fuel cells

    NASA Astrophysics Data System (ADS)

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

    2016-01-01

    La0.8Sr0.2Ga0.8Mg0.2O3 (LSGM) is considered a promising electrolyte for intermediate-temperature solid oxide fuel cells (IT-SOFCs) due to its high ionic conductivity and stability under fuel cell operating conditions. Here we report our findings in investigating the feasibility of using a high velocity oxygen fuel flame (HVOF) spraying process for cost-effective fabrication of dense LSGM electrolyte membranes. The flame and in-flight particle behavior were simulated numerically to optimize the microstructure and phase compositions of the LSGM deposits. The measured gas leakage rate of an LSGM deposit is ∼7 × 10-7 cm4gf-1 s-1. The single cell assembled with 50-55 μm HVOF-sprayed LSGM electrolyte shows open circuit voltage (OCV) of 1.08 V at 800 °C, suggesting that the as-sprayed LSGM deposit is dense enough for direct application as SOFC electrolyte. At 800 °C, the ionic conductivity of the sprayed LSGM deposit is ∼0.04 S cm-1, indicating that the HVOF spraying is a promising process for low-temperature fabrication of dense LSGM electrolyte membranes for IT-SOFCs.

  10. Computational fluid dynamic modeling of gas flow characteristics in a high-velocity oxy-fuel thermal spray system

    NASA Astrophysics Data System (ADS)

    Gu, S.; Eastwick, C. N.; Simmons, K. A.; McCartney, D. G.

    2001-09-01

    A computational fluid dynamics (CFD) model is developed to predict gas dynamic behavior in a high-velocity oxy-fuel (HVOF) thermal spray gun in which premixed oxygen and propylene are burnt in a 12 mm combustion chamber linked to a parallel-sided nozzle. The CFD analysis is applied to investigate axisymmetric, steady-state, turbulent, compressible, and chemically combusting flow both within the gun and in a free jet region between the gun and the substrate to be coated. The combustion of oxygen and propylene is modeled using a single-step, finite-rate chemistry model that also allows for dissociation of the reaction products. Results are presented to show the effect of (1) fuel-to-oxygen gas ratio and (2) total gas flow rate on the gas dynamic behavior. Along the centerline, the maximum temperature reached is insensitive to the gas ratio but depends on the total flow. However, the value attained (˜2500 K) is significantly lower than the maximum temperature (˜3200 K) of the annular flame in the combustion chamber. By contrast, the centerline gas velocity depends on both total flow and gas ratio, the highest axial gas velocity being attained with the higher flow and most fuel-rich mixture. The gas Mach number increases through the gun and reaches a maximum value of approximately 1.6 around 5 mm downstream from the nozzle exit. The numerical calculations also show that the residual oxygen level is principally dependent on the fuel-to-oxygen ratio and decreases by approximately fivefold as the ratio is varied from 90 to 69% of the stoichiometric requirement. The CFD model is also used to investigate the effect of changes in combustion chamber size and geometry on gas dynamics, and the results are compared with the nominal 12 mm chamber baseline calculations.

  11. A Novel Hybrid Axial-Radial Atmospheric Plasma Spraying Technique for the Fabrication of Solid Oxide Fuel Cell Anodes Containing Cu, Co, Ni, and Samaria-Doped Ceria

    NASA Astrophysics Data System (ADS)

    Cuglietta, Mark; Kuhn, Joel; Kesler, Olivera

    2013-06-01

    Composite coatings containing Cu, Co, Ni, and samaria-doped ceria (SDC) have been fabricated using a novel hybrid atmospheric plasma spraying technique, in which a multi-component aqueous suspension of CuO, Co3O4, and NiO was injected axially simultaneously with SDC injected radially in a dry powder form. Coatings were characterized for their microstructure, permeability, porosity, and composition over a range of plasma spray conditions. Deposition efficiency of the metal oxides and SDC was also estimated. Depending on the conditions, coatings displayed either layering or high levels of mixing between the SDC and metal phases. The deposition efficiencies of both feedstock types were strongly dependent on the nozzle diameter. Plasma-sprayed metal-supported solid oxide fuel cells utilizing anodes fabricated with this technique demonstrated power densities at 0.7 V as high as 366 and 113 mW/cm2 in humidified hydrogen and methane, respectively, at 800 °C.

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

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

    NASA Technical Reports Server (NTRS)

    Gomez, Alessandro; Chen, Gung

    1995-01-01

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

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

    NASA Astrophysics Data System (ADS)

    Sharma, Prashant; Majumdar, Jyotsna Dutta

    2015-07-01

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

  15. Numerical modeling of in-flight characteristics of inconel 625 particles during high-velocity oxy-fuel thermal spraying

    NASA Astrophysics Data System (ADS)

    Gu, S.; McCartney, D. G.; Eastwick, C. N.; Simmons, K.

    2004-06-01

    A computational fluid dynamics (CFD) model is developed to predict particle dynamic behavior in a high-velocity oxyfuel (HVOF) thermal spray gun in which premixed oxygen and propylene are burnt in a combustion chamber linked to a long, parallel-sided nozzle. The particle transport equations are solved in a Lagrangian manner and coupled with the two-dimensional, axisymmetric, steady state, chemically reacting, turbulent gas flow. Within the particle transport model, the total flow of the particle phase is modeled by tracking a small number of particles through the continuum gas flow, and each of these individual particles is tracked independently through the continuous phase. Three different combustion chamber designs were modeled, and the in-flight particle characteristics of Inconel were 625 studied. Results are presented to show the effect of process parameters, such as particle injection speed and location, total gas flow rate, fuel-to-oxygen gas ratio, and particle size on the particle dynamic behavior for a parallel-sided, 12 mm long combustion chamber. The results indicate that the momentum and heat transfer to particles are primarily influenced by total gas flow. The 12 mm long chamber can achieve an optimum performance for Inconel 625 powder particles ranging in diameter from 20 to 40 µm. At a particular spraying distance, an optimal size of particles is observed with respect to particle temperature. The effect of different combustion chamber dimensions on particle dynamics was also investigated. The results obtained for both a 22 mm long chamber and also one with a conical, converging design are compared with the baseline data for the 12 mm chamber.

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

    PubMed

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

    2015-12-24

    Using blends of bioethanol and gasoline as automotive fuel leads to a net decrease in the production of harmful emission compared to the use of pure fossil fuel. However, fuel droplet evaporation dynamics change depending on the mixing ratio. Here we use single particle manipulation techniques to study the evaporation dynamics of ethanol/gasoline blend microdroplets. The use of an electrodynamic balance enables measurements of the evaporation of individual droplets in a controlled environment, while optical tweezers facilitate studies of the behavior of droplets inside a spray. Hence, the combination of both methods is perfectly suited to obtain a complete picture of the evaporation process. The influence of adding varied amounts of ethanol to gasoline is investigated, and we observe that droplets with a greater fraction of ethanol take longer to evaporate. Furthermore, we find that our methods are sensitive enough to observe the presence of trace amounts of water in the droplets. A theoretical model, predicting the evaporation of ethanol and gasoline droplets in dry nitrogen gas, is used to explain the experimental results. Also a theoretical estimation of the saturation of the environment, with other aerosols, in the tweezers is carried out. PMID:26633739

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

    NASA Technical Reports Server (NTRS)

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

    1983-01-01

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

  18. Synthesis of nanostructured WC-12 pct Co coating using mechanical milling and high velocity oxygen fuel thermal spraying

    SciTech Connect

    He, J. Ice, M.; Dallek, S.; Lavernia, E.J.

    2000-02-01

    A nanostructured WC-12 pct Co coating was synthesized using mechanical milling and high velocity oxygen fuel (HVOF) thermal spraying. The variation of powder characteristics with milling time and the performance of the coatings were investigated using scanning electron microscope (SEM), X-ray, transmission electron microscope (TEM), thermogravimetric analyzer (TGA), and microhardness measurements. There is no evidence that indicates the presence of an amorphous phase in the sintered WC-12 pct Co powder, and the binder phase in this powder is still crystalline Co. Mechanical milling of up to 20 hours did not lead to the formation of an amorphous phase in the sintered WC-12 pct Co powder. During the initial stages of the milling, the brittle carbide particles were first fractured into fragments and then embedded into the binder phase. This process gradually formed polycrystal nanocomposite powders of the Co binder phase and W carbide particles. The conventional cold welding and fracturing processes primarily occurred among the Co binder powders and polycrystal composite powders. The nanostructured WC-12 pct Co coatings, synthesized in the present study, consist of an amorphous matrix and carbides with an average particle diameter of 35 nm. The coating possesses an average microhardness of 1135 HV and higher resistance to indentation fracture than that of its conventional counterpart.

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

    SciTech Connect

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

    1996-09-01

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

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

    NASA Technical Reports Server (NTRS)

    Zimmerman, Frank

    2000-01-01

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

  1. Effect of elevated temperature and pressure on sprays from simplex swirl atomizers

    NASA Technical Reports Server (NTRS)

    Dodge, L. G.; Biaglow, J. A.

    1986-01-01

    An examination is made of the effects of air temperature and pressure on the spray quality of a moderately high capacity pressure swirl atomizer spraying jet-A and No. 2 diesel fuel. Drop size distributions, in terms of both Sauter mean diameter (SMD) and the width of the distribution given by the Rosin-Rammler N parameter, are determined over a variety of air conditions. Close to the nozzle, limited data suggest that the SMDs were a strong function of air density, but independent of air temperature. Trends of SMD and N are shown as a function of distance from the nozzle at all conditions, indicating some of the evaporation characteristics of fuel sprays.

  2. Effect of nano-crystallization of high velocity oxy-fuel-sprayed amorphous NiCrBSi alloy on properties of the coatings

    NASA Astrophysics Data System (ADS)

    Li, Chang-Jiu; Wang, Yu-Yue; Li, Hua

    2004-09-01

    NiCrBSi self-fluxing alloy coatings were deposited by high velocity oxy-fuel (HVOF) spraying. Annealing treatment was applied to the as-sprayed coatings to develop the microstructure of the Ni-based coating. The microstructure of the coating was characterized using optical microscopy, x-ray diffraction and transmission electron microscopy. The crystallization behavior of the amorphous coating was also characterized by differential scanning calorimetry. The properties of the coating were characterized by microhardness and abrasive wear tests. The results showed that the as-sprayed HVOF coating deposited by well melted spray particles exhibited a dense microstructure of amorphous phase. It was revealed that the crystallization of the amorphous phase in HVOF NiCrBSi coating occurs at a temperature of about 502°C. Annealing at temperature a little higher than recrystallization temperature leads to the formation of the nano-crystalline microstructure. The subsequent nanostructured Ni-based coating presents higher microhardness and excellent wear performance. With the further increase in annealing temperature, the growth of the nano-crystalline grains occurs and, accordingly, the microhardness of the coating and the wear performance decrease. Thereafter, the microstructure and properties of the Ni-based self-fluxing alloy coating can be controlled through postannealing treatment.

  3. 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.

  4. A single step solution combustion approach for preparing gadolinia doped ceria solid oxide fuel cell electrolyte material suitable for wet powder and plasma spraying processes

    NASA Astrophysics Data System (ADS)

    Shri Prakash, B.; William Grips, V. K.; Aruna, S. T.

    2012-09-01

    The present study explores the versatility of solution combustion method for preparing powders of varying characteristics suitable for intermediate temperature solid oxide fuel cell (IT-SOFC) fabrication. The promising electrolyte material for IT-SOFC, Gd0.2Ce0.8O2-δ (GDC), is considered for the present investigation. GDC powders consisting of sub-micron sized particles (<250 nm) and micron sized (>20 μm) particles are produced by varying the fuel used in the combustion reaction. Highly sinteractive nano-GDC powders prepared using oxalyl dihydrazide as a fuel results in dense pellets with high conductivity (3 × 10-4 Scm-1 at 400 °C). This powder also results in a stable suspension suitable for wet powder spraying and electrophoretic deposition. Powders with larger particle size (>20 μm) prepared by solution combustion method using mixture of fuels, exhibits necessary flowability for atmospheric plasma spraying (APS). GDC coatings fabricated by APS using flowable powders are dense with superior adhesion between the splats. Good adhesion between the splats in the APS coatings is attributed to the higher level of melting of the combustion synthesized particles in the plasma flame owing to their low specific mass.

  5. On the Oscillation of Combustion of a Laminar Spray

    NASA Technical Reports Server (NTRS)

    Levy, Yeshayahou; Bulzan, Daniel L.

    1995-01-01

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

  6. Spray Diagnostics in Rocket Engines Using Phase Doppler Analyzer

    NASA Technical Reports Server (NTRS)

    Isaac, Kakkattukuzhy M.

    1996-01-01

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

  7. Portable Spray Booth

    NASA Technical Reports Server (NTRS)

    Hansen, Timothy D.; Bardwell, Micheal J.

    1996-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-05-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

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

  10. Sprayed coatings

    NASA Astrophysics Data System (ADS)

    Steffens, H. D.

    1980-03-01

    Thermal spraying is shown to be an efficient means for the protection of surface areas against elevated temperature, wear, corrosion, hot gas corrosion, and erosion in structural aircraft components. Particularly in jet engines, numerous parts are coated by flame, detonation, or plasma spraying techniques. The applied methods of flame, detonation, and plasma spraying are explained, as well as electric arc spraying. Possibilities for spray coatings which meet aircraft service requirements are discussed, as well as methods for quality control, especially nondestructive test methods. In particular, coating characteristics and properties obtained by different spray methods are described, and special attention is paid to low pressure plasma spraying.

  11. Fundamental studies of spray combustion

    SciTech Connect

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

    1997-12-31

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

  12. Model of Mixing Layer With Multicomponent Evaporating Drops

    NASA Technical Reports Server (NTRS)

    Bellan, Josette; Le Clercq, Patrick

    2004-01-01

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

  13. Acoustic effects of sprays

    NASA Technical Reports Server (NTRS)

    Pindera, Maciej Z.; Przekwas, Andrzej J.

    1994-01-01

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

  14. 40 CFR 1045.25 - How do the requirements related to evaporative emissions apply to engines and their fuel systems?

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... of conformity issued under 40 CFR part 1060. (c) Fuel lines intended to be used with new engines and new portable marine fuel tanks must be certified to the applicable requirements of 40 CFR part 1060... of 40 CFR part 1060. (d) All persons installing engines certified under this part 1045 must...

  15. 40 CFR 1045.25 - How do the requirements related to evaporative emissions apply to engines and their fuel systems?

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... of conformity issued under 40 CFR part 1060. (c) Fuel lines intended to be used with new engines and new portable marine fuel tanks must be certified to the applicable requirements of 40 CFR part 1060... of 40 CFR part 1060. (d) All persons installing engines certified under this part 1045 must...

  16. 40 CFR 1045.25 - How do the requirements related to evaporative emissions apply to engines and their fuel systems?

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... of conformity issued under 40 CFR part 1060. (c) Fuel lines intended to be used with new engines and new portable marine fuel tanks must be certified to the applicable requirements of 40 CFR part 1060... of 40 CFR part 1060. (d) All persons installing engines certified under this part 1045 must...

  17. 40 CFR 1045.25 - How do the requirements related to evaporative emissions apply to engines and their fuel systems?

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... of conformity issued under 40 CFR part 1060. (c) Fuel lines intended to be used with new engines and new portable marine fuel tanks must be certified to the applicable requirements of 40 CFR part 1060... of 40 CFR part 1060. (d) All persons installing engines certified under this part 1045 must...

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

    NASA Technical Reports Server (NTRS)

    Bellan, J.; Harstad, K.

    1997-01-01

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

  19. 40 CFR 1045.25 - How do the requirements related to evaporative emissions apply to engines and their fuel systems?

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... of conformity issued under 40 CFR part 1060. (c) Fuel lines intended to be used with new engines and new portable marine fuel tanks must be certified to the applicable requirements of 40 CFR part 1060... of 40 CFR part 1060. (d) All persons installing engines certified under this part 1045 must...

  20. Plasma sprayed ceria-containing interlayer

    DOEpatents

    Schmidt, Douglas S.; Folser, George R.

    2006-01-10

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

  1. Spray combustion model improvement study, 1

    NASA Technical Reports Server (NTRS)

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

    1993-01-01

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

  2. Spray-on polyvinyl alcohol separators and impact on power production in air-cathode microbial fuel cells with different solution conductivities.

    PubMed

    Hoskins, Daniel L; Zhang, Xiaoyuan; Hickner, Michael A; Logan, Bruce E

    2014-11-01

    Separators are used to protect cathodes from biofouling and to avoid electrode short-circuiting, but they can adversely affect microbial fuel cell (MFC) performance. A spray method was used to apply a polyvinyl alcohol (PVA) separator to the cathode. Power densities were unaffected by the PVA separator (339±29mW/m(2)), compared to a control lacking a separator in a low conductivity solution (1mS/cm) similar to wastewater. Power was reduced with separators in solutions typical of laboratory tests (7-13mS/cm), compared to separatorless controls. The PVA separator produced more power in a separator assembly (SEA) configuration (444±8mW/m(2)) in the 1mS/cm solution, but power was reduced if a PVA or wipe separator was used in higher conductivity solutions with either Pt or activated carbon catalysts. Spray and cast PVA separators performed similarly, but the spray method is preferred as it was easier to apply and use. PMID:25260178

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

    NASA Technical Reports Server (NTRS)

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

    1990-01-01

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

  4. Antistatic sprays

    NASA Technical Reports Server (NTRS)

    Ming, James E.

    1989-01-01

    Antistatic sprays from several different manufacturers are examined. The sprays are examined for contamination potential (i.e., outgassing and nonvolatile residue), corrosiveness on an aluminum mirror surface, and electrostatic effectiveness. In addition, the chemical composition of the antistatic sprays is determined by infrared spectrophotometry, mass spectrometry, and ultraviolet spectrophotometry. The results show that 12 of the 17 antistatic sprays examined have a low contamination potential. Of these sprays, 7 are also noncorrosive to an aluminum surface. And of these, only 2 demonstrate good electrostatic properties with respect to reducing voltage accumulation; these sprays did not show a fast voltage dissipation rate however. The results indicate that antistatic sprays can be used on a limited basis where contamination potential, corrosiveness, and electrostatic effectiveness is not critical. Each application is different and proper evaluation of the situation is necessary. Information on some of the properties of some antistatic sprays is presented in this document to aid in the evaluation process.

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

    SciTech Connect

    Regina, J.R.

    2002-02-08

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

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

    NASA Technical Reports Server (NTRS)

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

    1977-01-01

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

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

    SciTech Connect

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

    2014-02-24

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

  8. Hot air drum evaporator. [Patent application

    DOEpatents

    Black, R.L.

    1980-11-12

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

  9. Water spray ejector system for steam injected engine

    SciTech Connect

    Hines, W.R.

    1991-10-08

    This paper describes a method of increasing the power output of a steam injected gas turbine engine. It comprises: a compressor, a combustor having a dome which receives fuel and steam from a dual flow nozzle, and a turbine in series combination with a gas flow path passing therethrough, and a system for injection of superheated steam into the gas flow path, the method comprising spraying water into the steam injection system where the water is evaporated by the superheated steam, mixing the evaporated water with the existing steam in the steam injection system so that the resultant steam is at a temperature of at least 28 degrees celsius (50 degrees fahrenheit) superheat and additional steam is added to the dome from the fuel nozzle to obtain a resultant increased mass flow of superheated steam mixture for injection into the gas flow path, and controlling the amount of water sprayed into the steam injection system to maximize the mass flow of superheated steam without quenching the flame.

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

    NASA Astrophysics Data System (ADS)

    Mann, B. S.

    2013-08-01

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