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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 523 records · Page 29
All sourcesNASA NTRSDOE OSTI
NASA NTRS1972

Fuel droplet burning rates at high pressures

Combustion of methanol, ethanol, propanol -1, n - pentane, n - heptane and n - decane was observed in air under natural convection conditions at pressures up to 100 atm. The droplets were simulated by porous spheres with diameters in the range 0.63 - 1.90 cm. The pressure levels of the tests were high enough so that near critical combustion was observed for methanol and ethanol. Measurements were made of the burning rate and liquid surface temperatures of the fuels. The data were compared with variable property analysis of the combustion process, including a correction for natural convection. The burning rate predictions of the various theories were similar and in fair agreement with the data. The high pressure theory gave the best prediction for the liquid surface temperatures of ethanol and propanol -1 at high pressure. The experiments indicated the approach of critical burning conditions for methanol and ethanol at pressures on the order of 80 - 100 atm, which was in good agreement with the predictions of both the low and high pressure analysis.

Canada, G. S.↗
NASA NTRS1973

Droplet monitoring probe

A droplet monitoring system is disclosed for analysis of mixed-phase fluid flow in development of gas turbines. The system uses a probe comprising two electrical wires spaced a known distance apart and connected at one end to means for establishing a dc potential between the wires. A drop in the fluid stream momentarily contacting both wires simultaneously causes and electrical signal which is amplified, detected and counted.

Baughman, J. R.↗
NASA NTRS1973

Fuel droplet burning rates at high pressures.

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

Canada, G. S.↗
NASA NTRS1973

Deformation and burst of a liquid droplet freely suspended in a linear shear field

A theoretical method is presented for predicting the deformation and the conditions for breakup of a liquid droplet freely suspended in a general linear shear field. This is achieved by expanding the solution to the creeping-flow equations in powers of the deformation parameter epsilon and using linear stability theory to determine the onset of bursting. When compared with numerical solutions and with the available experimental data, the theoretical results are generally found to be of acceptable accuracy although, in some cases, the agreement is only qualitative.

Barthes-Biesel, D.↗
NASA NTRS1975

Investigation of critical burning of fuel droplets

Steady and unsteady combustion of liquid fuel droplets under rocket engine conditions was analyzed. Emphasis was placed on combustion at elevated pressures and temperatures. The results and their technical application to the design of liquid fueled rocket engines and the determination of combustion instability characteristics of these engines were summarized.

Faeth, G. M.↗
NASA NTRS1975

Mechanism of ignition in shock wave interactions with reactive liquid droplets

A detailed qualitative analysis of the processes leading to the explosive ignition of a reactive liquid droplet that is suspended in a gas-phase oxidizer and subjected to the passage of a shock wave, is presented. The interval of time between shock wave passage and ignition is described by identifying a two-stage process which consists of a period of relative reactive dormancy that is followed by a chemical induction period leading to the thermal explosion of reactant that has been stripped from the liquid drop, vaporized, and mixed with the gas-phase oxidizer. The results of first-order calculations based on this model are presented and compared with experimental data for diethlcyclohexane drops in oxygen.

Pierce, T. H.↗
NASA NTRS1975

Skylab Fluid Mechanics Simulations: Oscillation, Rotation, Collision and Coalescence of Water Droplets Under Low-Gravity Environment

Skylab 4 crew members performed a series of demonstrations showing the oscillations, rotations, as well as collision coalescence of water droplets which simulate various physical models of fluids under low gravity environment. The results from Skylab demonstrations provide information and illustrate the potential of an orbiting space-oriented research laboratory for the study of more sophisticated fluid mechanic experiments. Experiments and results are discussed.

Otha H Vaughan, Jr↗
NASA NTRS1977

Generator of droplet tracers for holographic flow visualization in water tunnels

Design of a tracer-particle generator for use in holographic flow visualization of complex flow fields is discussed. Desired characteristics of the tracer particles, including a size range of 20 to 200 microns, a spherical shape to facilitate focusing of holograms, and a fluid density near that of ambient particles, are reviewed; a particle injection rate of 100 to 1000 per sec in water tunnels with flow velocities between one and 10 meters per sec is also desirable. The operation of the particle generator, which produces uniform droplets with the specified optical properties, is described.

Charwat, A. F.↗
NASA NTRS1977

Observations on the burning of droplets in the absence of buoyancy

?The first stages of an experimental study on droplet burning at zero gravity are described. Motivations for the work are to investigate transient burning and effects of finite-rate chemistry, in a geometrical configuration sufficiently simple for theoretical analyses to be performed in detail and checked against experiment. Two possible approaches to the experimental problem are to establish burning in a freely falling chamber in a drop tower and to perform the experiments in a research facility in space, such as spacelab. The work reported here concerns the drop-tower experiments. The design of these experiments is discussed, and preliminary results of the experimental program are given. Critical problems in drop-tower testing of this kind, especially timing problems that arise in this particular experiment, are emphasized.

Knight, B.↗
NASA NTRS1979

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

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

Miles, J. H.↗
NASA NTRS1979

Negative pressures and melting point depression in oxide-coated liquid metal droplets

Negative pressures and melting point depression in oxide-coated liquid metal droplets are studied. The calculation presented show the existence of large negative pressures when the oxide coating is thick enough. The change in the melting point caused by these negative pressures should be considered in studies of homogeneous crystal nucleation. Furthermore, since the negative pressure raises the entropy of the melt, it increases the entropy loss at the crystal-melt interface; the resulting increase of the surface tension could have a large effect on the homogeneous nucleation frequency.

Spaepen, F.↗
NASA NTRS1980

Photographic measurement of droplet density

Density of cloud droplets in expansion chamber or static diffusion liquid chamber is measured with error of less than 3 percent by improved photographic technique. Precision is substantial advance over 10 percent accuracy limitation in methods used in past. Method should be useful in pollutant analysis, fine-particle research, and aerosol studies.

Yager, W. C.↗