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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 433 records · Page 24

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NASA NTRS1982

The dryout region in frictionally heated sliding contacts

Some conditions under which boiling and two-phase flow can occur in or near a wet sliding contact are determined and illustrated. The experimental apparatus consisted of a tool pressed against an instrumented slider plate and motion picture sequences at 4000 frames/sec. The temperature and photographic data demonstrated surface conditions of boiling, drying, trapped gas evolution (solutions), and volatility of fluid mixture components. The theoretical modeling and analysis are in reasonable agreement with experimental data.

Hendricks, R. C.↗

NASA NTRS1982

Thermal control for the 1990's

Current thermal distribution systems on large spacecraft, such as the Space Shuttle and Spacelab, use pumped fluid loops that circulate the coolant between a series of user stations and a single rejection point, involving complex plumbing and controls with a significant power penalty and limited reliability. In order to provide heat transport at near-isothermal conditions in future large spacecraft, two-phase flow systems will be implemented by taking advantage of the heat of vaporization and condensation of common working fluids at minimal expenditure of power and temperature variation. Such systems are considered for the cases of the thermal requirements of nearly 100 potential astrophysics and astronomy instruments. Data on temperature requirements, power dissipations, environmental fluxes, heat addition or rejection, and general description, are used to form conceptual designs for the thermal utility.

Ollendorf, S.↗

NASA NTRS1983

Analogy between fluid cavitation and fracture mechanics

When the stresses imposed on a fluid are sufficiently large, rupture or cavitation can occur. Such conditions can exist in many two-phase flow applications, such as the choked flows, which can occur in seals and bearings. Nonspherical bubbles with large aspect ratios have been observed in fluids under rapid acceleration and high shear fields. These bubbles are geometrically similar to fracture surface patterns (Griffith crack model) existing in solids. Analogies between crack growth in solid and fluid cavitation are proposed and supported by analysis and observation (photographs). Healing phenomena (void condensation), well accepted in fluid mechanics, have been observed in some polymers and hypothesized in solid mechanics. By drawing on the strengths of the theories of solid mechanics and cavitation, a more complete unified theory can be developed.

Hendricks, R. C.↗

NASA NTRS1982

The dryout region in frictionally heated sliding contacts

Some conditions under which boiling and two-phase flow can occur in or near a wet sliding contact are determined and illustrated. The experimental apparatus consisted of a tool pressed against an instrumented slider plate and motion picture sequences at 4000 frames/sec. The temperature and photographic data demonstated surface conditions of boiling, dry, trapped gas evolution (solutions), and volatility of fluid mixture components. The theoretical modeling and analysi are in reasonable agreement with experimental data. Previously announced in STAR as N82-28574

Hendricks, R. C.↗

NASA NTRS1984

Thermal control

There are basically three key ingredients to the thermal control system for any large space platform or space station. These are heat rejection (from a centralized radiator or from body mounted radiators), heat acquisition (from payloads), and heat transport (via a transport loop to the radiator). The echnical approach in the heat rejection area is to construct the radiator from individual elements so that it can be built on-orbit, is very insensitive to meteoroid and debris hazards, and is repairable. In the area of thermal acquisition and transport an added effort to better understand two phase flow in zero gravity by analysis and testing is suggested.

Haslett, B.↗

NASA NTRS1984

Bearing tester data compilation, analysis and reporting and bearing math modeling, volume 1

Thermal and mechanical models of high speed angular contact ball bearings operating in LOX and LN2 were developed and verified with limited test data in an effort to further understand the parameters that determine or effect the SSME turbopump bearing operational characteristics and service life. The SHABERTH bearing analysis program which was adapted to evaluate shaft bearing systems in cryogenics is not capable of accommodating varying thermal properties and two phase flow. A bearing model with this capability was developed using the SINDA thermal analyzer. Iteration between the SHABERTH and the SINDA models enable the establishment of preliminary bounds for stable operation in LN2. These limits were established in terms of fluid flow, fluid inlet temperature, and axial load for a shaft speed of 30,000 RPM.

Marshall, D. D.↗

NASA NTRS1984

A two-equation turbulence model for two-phase jets

A recently-developed two-equation turbulence model for two-phase flows (Elghobashi and Abou-Arab, 1983) is tested for the flow of a turbulent axisymmetric gaseous jet laden with spherical solid particles of uniform size. The agreement between the predictions of experimental data is good.

Elghobashi, S.↗

NASA NTRS1986

Heat-Pipe Array for Large-Area Cooling

High rates of heat transfer anticipated. Prototype evaporative cold plate gathers waste heat from equipment mounted on it. Plate made by welding together flanges of several sections of heat pipe. Since plate separates liquid and vapor phases at inlet and outlet ports, eliminates complexities and uncertainties of two-phase flow in zero gravity. On earth, inlet valve enables plate to operate at relatively-large height differences with other plates in same system.

Edelstein, F.↗

NASA NTRS1985

Optical technique to study the impact of heavy rain on aircraft performance

A laser based technique was investigated and shown to have the potential to obtain measurements of the size and velocity of water droplets used in a wind tunnel to simulate rain. A theoretical model was developed which included some simple effects due to droplet nonsphericity. Parametric studies included the variation of collection distance (up to 4 m), angle of collection, effect of beam interference by the spray, and droplet shape. Accurate measurements were obtained under extremely high liquid water content and spray interference. The technique finds applications in the characterization of two phase flows where the size and velocity of particles are needed.

Hess, C. F.↗

NASA NTRS1987

Algorithm for Fluid Networks

Algorithm performs either transient integration or steady-state relaxation of network that represents internal fluid system. Valid for both single and two-phase flow of any fluid and includes both heat-transfer and work terms. General enough to simulate almost any flow system to almost any degree of detail desired. Encoded into computer program FLUINT, will work in conjunction with SINDA-85 program to enable analysis of pipelines; heating, ventilating, and cooling systems; and almost any other system that involves both fluid flow and heat transfer. Other possible extensions includes effects of flexibilities of containers, high-velocity flow, gravitation, acceleration, and opening and closing valves.

Cullimore, Brent A.↗

NASA NTRS1986

Fiber optic sensors; Proceedings of the Meeting, Cannes, France, November 26, 27, 1985

The conference presents papers on distributed sensors and sensor networks, signal processing and detection techniques, temperature measurements, chemical sensors, and the measurement of pressure, strain, and displacements. Particular attention is given to optical fiber distributed sensors and sensor networks, tactile sensing in robotics using an optical network and Z-plane techniques, and a spontaneous Raman temperature sensor. Other topics include coherence in optical fiber gyroscopes, a high bandwidth two-phase flow void fraction fiber optic sensor, and a fiber-optic dark-field microbend sensor.

Arditty, Herve J.↗

NASA NTRS1987

Two-phase measurements of a spray in the wake of a bluff body

The dynamics of spray drop interaction with the turbulent, recirculating wake of a flat disk bluff body were investigated using a phase Doppler particle analyzer to determine drop size and velocity and the gas-phase velocity. Detailed measurements obtained included spray drop size, axial and radial velocity, angle of trajectory, and size-velocity correlations. The gas-phase velocity was determined from seeding of the two-phase flow. Results showed dramatic differences in drop behavior for various size classes when interacting with the turbulent flow field. Small drops were quickly entrained and recirculated, while initially, the larger drops continued in the general direction of the spray cone. Further downstream, significant numbers of large drops recirculated, generating a bifurcated size-velocity correlation. These lateral convections and streamwise accelerations and decelerations strongly influenced the number density along with size and velocity distributions. The complex interaction of the spray with the turbulent air-flow points out the need for spatially-resolved measurements that determine drop behavior for individual size classes, rather than characterizing a spray only via simple integral quantities such as the Sauter mean diameter.

Rudoff, R. C.↗

NASA NTRS1988

Fuel-injector/air-swirl characterization

Experimental data on the characteristics of the spray produced by a gas-turbine engine airblast fuel injector are reported. The data acquired include the mass-flux distribution measured by use of a high-resolution spray patternator; the gas-phase velocity field measured by use of a two-component laser Doppler velocimeter, and the liquid droplet size and velocity distributions measured by use of a single-component phase-Doppler anemometer. The data are intended for use in assessments of two-phase flow computational methods as applied to combustor design procedures.

Mcvey, J. B.↗

NASA NTRS1988

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

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

Powell, Eugene A.↗

NASA NTRS1989

Workshop on Two-Phase Fluid Behavior in a Space Environment

The Workshop was successful in achieving its main objective of identifying a large number of technical issues relating to the design of two-phase systems for space applications. The principal concern expressed was the need for verified analytical tools that will allow an engineer to confidently design a system to a known degree of accuracy. New and improved materials, for such applications as thermal storage and as heat transfer fluids, were also identified as major needs. In addition to these research efforts, a number of specific hardware needs were identified which will require development. These include heat pumps, low weight radiators, advanced heat pipes, stability enhancement devices, high heat flux evaporators, and liquid/vapor separators. Also identified was the need for a centralized source of reliable, up-to-date information on two-phase flow in a space environment.

Swanson, Theodore D.↗

NASA NTRS1989

Time analysis of polydisperse sprays in complex turbulent environments

The two-phase flow field of a small swirl-stabilized burner has been investigated, using a phase Doppler particle analyzer to obtain the velocity, drop size, and time of arrival components. Water/kerosene comparisons were made for the case of nonreacting flow. It is found that the spray flow field is strongly influenced by the aerodynamic flow field and by the reaction and fluid properties. It is noted that vortex shedding produces clusters of drops.

Rudoff, R. C.↗

NASA NTRS1990

Behavior Of Evaporating Liquid Drops In Clusters

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

Bellan, Josette↗

NASA NTRS1991

Status of heavy rain tests

The heavy rain effects program is presented in the form of the view-graphs. The following topics are covered: rain effects on airfoil performance; two-phase flow dynamics; wind tunnel test results; issues; large-scale results; and summary.

Bezos, Gaudy↗