Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “sprays”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 613 records · Page 34
All sourcesNASA NTRSDOE OSTI
NASA NTRS1992

A numerical model for coupling between atomization and spray dynamics in liquid rocket thrust chambers

This paper describes a novel method of coupling the atomization and spray combustion processes encountered in coaxial injection elements of liquid rocket engine thrust chambers. This method is based on the Jet-Embedding technique in which the liquid jet core equations and the gas phase equations are solved separately. The liquid and gas phase solutions, however, are coupled through the boundary conditions at the interface between the phases. The computational grid for the gas phase calculations are adapted to the shape of the liquid jet core. The axial variation of droplet sizes are calculated using a stability analysis appropriate for the atomization regime of liquid jet breakup. The predictions of this method have been validated with experimental data on low speed water jets. Using this method, calculations are performed for the SSME fuel preburner single injector flow field. The results obtained are in good agreement with the predictions of the volume-of-fluid method.

Giridharan, M. G.↗
NASA NTRS1993

Vacuum Plasma Spraying Of Copper Onto Titanium

Vacuum plasma spraying successful in depositing tenacious copper coat on flanges and other selected areas of titanium valve housing. Oxidation and concomitant brittleness eliminated.

Power, Chris↗
NASA NTRS1992

Numerical study on mixing of sprayed liquid in an LNG storage tank

This paper presents a numerical method to simulate the mixing of heavier LNG sprayed on lighter layer. Numerical results for evolutions of flow field and density field are obtained in a rectangular computational domain which includes the vicinity of the liquid surface. At the surface boundary, uniform distributions of the fluid velocity and the density are assumed. Detail structure of flow caused by impingements of liquid drops are neglected. But, to trigger a realistic motion, a series of random numbers is employed. It is used as an initial distribution of the density near the surface. This method successfully gives a realistic simulation of the mixing process. Numerical results for mixing velocity shows good agreement with experimental data.

Uchida, Hiroyuki↗
NASA NTRS1993

Atomizing-gas temperature effect on cryogenic spray dropsize

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

Ingebo, Robert D.↗
NASA NTRS1993

Velocity and drop size measurements in a swirl-stabilized, combusting spray

Velocity and drop size measurements are reported for a swirl-stabilized, combusting spray. For the gas phase, three components of mean and fluctuating velocity are reported. For the droplets, three components of mean and fluctuating velocity, diameter, and number flux are reported. The liquid fuel utilized for all the tests was heptane. The fuel was injected using an air-assist atomizer. The combustor configuration consisted of a center-mounted, air-assist atomizer surrounded by a coflowing air stream. Both the coflow and the atomizing air streams were passed through 45 degree swirlers. The swirl was imparted to both streams in the same direction. The combustion occurred unconfined in stagnant surroundings. The nonintrusive measurements were obtained using a two-component phase/Doppler particle analyzer. The laser-based instrument measured two components of velocity as well as droplet size at a particular point. Gas phase measurements were obtained by seeding the air streams with nominal 1 micron size aluminum-oxide particles and using the measured velocity from that size to represent the gas phase velocity. The atomizing air, coflow air, and ambient surroundings were all seeded with the aluminum-oxide particles to prevent biasing. Measurements are reported at an axial distance of 5 mm from the nozzle. Isothermal single-phase gas velocities are also reported for comparison with the combusting case.

Bulzan, Daniel L.↗
NASA NTRS1993

Modeling of spray droplets deformation and breakup

A droplet deformation and breakup (DDB) model is proposed to study shear-type mechanism of spray droplets in pure extentional flows. A numerical solution of the DDB model equation is obtained using a fourth-order Runge-Kutta initial-value solver. The predictions of the DDB model as well as semianalytical and the Taylor analogy models are compared with the experimental data (Krzeczkowski, 1980) for shear breakup, which depict the dimensionless deformation of the drop vs dimensionless time.

Ibrahim, E. A.↗
NASA NTRS1993

Effects of detailed droplet heating models on turbulent sprays vaporization behavior

The effects of three different droplet heating models on the vaporization history and internal structure of turbulent liquid fuel sprays were investigated. The models considered were the infinite-diffusion, diffusion-limit, and effective-conductivity models. A numerical solution for the models was developed and implemented in the KIVA-II computer code. Low temperature and relatively high temperature numerical studies were conducted. The low temperature computations were compared with existing experimental data. The comparisons showed that while the infinite-diffusion and diffusion-limit models respectively overpredicted and underpredicted the fuel vapor peak concentration and distribution in the combustor, the effective-conductivity model gave results that were in better agreement with measurements. A limited study for the high temperature case was performed due to lack of experimental data and predictions using the three models were compared with each other.

Mawid, M. A.↗
NASA NTRS1993

Atomizing-gas temperature effect on cryogenic spray dropsize

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

Ingebo, Robert D.↗
NASA NTRS1933

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

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.

Gelalles, A G↗
NASA NTRS1933

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

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.

Lee, Dana W↗
NASA NTRS1937

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

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.

Rothrock, A M↗
NASA NTRS1954

An analytical study of the effect of airplane wake on the lateral dispersion of aerial sprays

Calculations are made to determine the trajectories of liquid droplets introduced into the air disturbances generated by an airplane engaged in aerial spraying. The effects of such factors as the positions at which droplets are ejected into the disturbances, airplane lift coefficient, and altitude are investigated. The distribution of deposit on the ground is computed for several droplet-size spectra, variations in the rate at which mass is ejected along the span, and lateral flight-path spacings. Consideration is then given to the problem of adjusting these factors with the aim of improving the uniformity and increasing the effective width of the deposit. The results indicate that the lateral dispersion of droplets is increased when the spanwise position at which particles are ejected is moved toward the wing tip. Greater dispersion also results when the airplane lift coefficient or altitude is increased.

Reed, Wilmer H , III↗
NASA NTRS1994

Preventing Clogging In A Vacuum Plasma Spray Gun

Modification of powder-injection ports enables lengthy, high-temperature deposition operations. Graphite inserts prevent clogging of ports through which copper powder injected into vacuum plasma spray (VPS) gun. Graphite liners eliminate need to spend production time refurbishing VPS gun, reducing cost of production and increasing productivity. Concept also applied to other material systems used for net-shape fabrication via VPS.

Krotz, Phillip D.↗
NASA NTRS1994

Examining Thermally Sprayed Coats By Fluorescence Microscopy

True flaws distinquished from those induced by preparation of specimens. Fluorescence microscopy reveals debonding, porosity, cracks, and other flaws in specimens of thermally sprayed coating materials. Specimen illuminated, and dye it contains fluoresces, emitting light at different wavelength. Filters emphasize contrast between excitation light and emission light. Specimen viewed directly or photographed on color film.

Street, Kenneth W., Jr.↗
NASA NTRS1994

Rugged Preheaters For Vacuum Plasma Spraying

Electric preheater units built to ensure large workpieces to be coated with metals by vacuum plasma spraying heated uniformly to requisite high temperatures by time plasma torch arrives. Units similar to electrical-resistance ribbon heaters in toasters and in some small portable electric "space" heaters. Nichrome resistance-heating ribbons wrapped around ceramic insulating spools on rings and on plates. Round workpiece placed in middle of ring preheater. Plate preheaters stacked as needed near workpiece.

Woodford, William H.↗
NASA NTRS1993

On the combustion of a laminar spray

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.

Levy, Yeshayahou↗
NASA NTRS1993

Droplet-turbulence interactions in sprays exposed to supercritical environmental conditions

The goal of this research was to experimentally characterize the behavior of droplets in vaporizing sprays under conditions typical of those encountered in high pressure combustion systems such as liquid fueled rocket engines. Of particular interest are measurements of droplet drag and lift, droplet dispersion, droplet heating, and droplet vaporization under both subcritical and supercritical conditions. A summary of the major accomplishments achieved during the period from June 1990 through June 1993, a brief description and status report on five research areas, which were directly or indirectly supported by this grant, and a list of publications and personnel associated with this research is included.

Santavicca, Domenic A.↗