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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 829 records · Page 46
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NASA NTRSDate not supplied

Recent Ground-based Test Results for the Closed Loop Two-Phase Flow Chilldown Test Module for Future Integration with the Flow Boiling and Condensation Experiment onboard International Space Station

Effective cryogenic fluid management is important to the success of future manned and unmanned NASA missions, and the transfer line chilldown process is recognized as a key technological challenge. To address this challenge, the Two-phase Flow and Thermal Management Lab (TFTML) at Case Western Reserve University is collaborating with NASA Glenn Research Center to develop, test and deploy a closed loop two-phase flow chilldown test section onboard the International Space Station to be integrated with the current Flow Boiling and Condensation Experiment (FBCE) module. The final results of this project will create the first chilldown process database under pure and sustained microgravity conditions and will significantly advance the understanding of the chilldown process for cryogenic fluid management. In the present work, the ground-based test results of the closed loop SS-316 chilldown test section in a horizontal configuration at varying inlet mass flow rates (3-40 g/s) and inlet liquid subcooling (5-35 0C) are presented. The working fluid is PF-5060 and the chilldown curves captured the entire quenching curve involving the different boiling regimes and temperature transition points viz., film boiling, Leidenfrost/re-wetting point, transition boiling, critical heat flux (CHF), nucleate boiling, onset of nucleate boiling (ONB) and single-phase liquid flow regions, when the test section is pre-heated to around 250 0C. The major findings of the present study are, (i) the bottom part of the test section sees a lower re-wetting temperature due to the horizontal flow configuration, (ii) the re-wetting temperatures are relatively unaffected by inlet liquid mass flow rates though the increase in mass flow rates reduce the chilldown time, and (iii) the re-wetting temperatures decrease with decrease in inlet liquid subcooling. Further, preliminary flow visualization studies in a transparent pyrex test section will also be presented to understand the intricate flow boiling regime transitions during the chilldown process.

ISS↗
NASA NTRS1959

Characteristics of Five Ejector Configurations at Free-Stream Mach Numbers from 0 to 2.0

Thrust, air-handling, and base-pressure characteristics of five ejector configurations were investigated in the Lewis 8-by 6-foot wind tunnel at free-stream Mach numbers from 0 to 2.0 over ranges of primary-jet pressure ratio up to 24 and corrected secondary weight-flow ratio up to 13 percent. The ejector-shroud geometries varied from convergent to divergent. Base pressure ratio and ejector performance were interrelated by means of an exit-momentum parameter. Correlations, to at least a first approximation, with base pressure ratio, of both internal-ejector-flow separation and external-flow separation over the model boattail were shown. Furthermore, it was shown that magnitudes and exact trends in base pressure ratio depended largely, and in a complicated fashion, on ejector geometry and amount of secondary flow. External-stream effects on ejector jet thrust were determined for a typical schedule of jet-engine pressure ratios. With the exception of the ejector having the largest (1.81) shroud-exit-to primary-diameter ratio, there were no stream effects at Mach numbers from 1.5 to 2.0 and variations from quiescent-air thrust data were less than 2.5 percent at the subsonic speed investigated.

Klann, John L.↗
NASA NTRS1975

Computation of three-dimensional, inviscid supersonic flows

The paper sets forth in detail a method for the finite-difference computation of three-dimensional supersonic fields in an Eulerian mesh. First-, second-, and third-order finite difference schemes are examined. Attention is given to proper treatment of the impermeable and permeable boundaries encompassing the computational plane. Numerical results are presented for certain specific configurations: a conical wing-body combination, internal corner flow, a two-dimensional blunt body, an interfering shock problem, and three-dimensional inviscid supersonic flow past a shuttle-orbiter type vehicle.

Kutler, P.↗
NASA NTRS1976

Finite-volume solution of the Euler equations for steady three-dimensional transonic flow

A numerical finite-volume method is proposed for solving the Euler equations of a steady three-dimensional flow. The subsonic regions embedded in steady supersonic flow about aircraft are computed by introducing a time-dependent coordinate system that maps the fuselage and wing into one coordinate surface. The suitability of the method to a delta-winged aircraft is demonstrated, and its applicability to rectangular-winged aircraft and problems in internal transonic flow is pointed out.

Rizzi, A.↗
NASA NTRS1985

Multiple-scale turbulence closure modeling of confined recirculating flows

A multiple-scale turbulence closure scheme is developed for the numerical predictions of confined recirculating flows. This model is based on the multiple-time-scale concepts of Hanjalic et al. (1980) and takes into account the non-equilibrium spectra energy transfer mechanism. Problems concerning new formulation of energy transfer rate equations and subsequent model coefficient redefinition and energy spectrum partition are discussed. Comparisons are made with several experiments of internal recirculating flows for the purpose of model validation. Numerical results using the present model show significant improvement of predictive capability over that obtained with the single-scale k-epsilon model and show promising potential for complex turbulent flow predictions.

Chen, C. P.↗
DOE OSTI2019

Effect of internal magnetic field on collective flow in heavy ion collisions at intermediate energies

The properties of nuclear matter under extreme conditions of high temperature, density, and isospin asymmetry have attracted wide attention in recent years. At present, heavy ion reactions in combination with corresponding model simulations are one of the most important ways to investigate this subject. It is known that a strong magnetic field can be created in heavy ion collisions. However, its effect on the motion of charged particles is usually neglected in previous transport model simulations. In this work, within the ultrarelativistic quantum molecular dynamics (UrQMD) model, the temporal evolution and spatial distribution of the internal magnetic field are calculated. The magnetic field strength is found to reach about eB ≈ 470 MeV 2 (B ≈ 8 × 10 16 G) for Au + Au collisions at E lab = 1 GeV/nucleon with impact parameter of 7 fm. The magnetic field in Cu + Au collisions exhibits somewhat different spatial distribution from that in Au + Au collisions. The magnetic field is found to affect the directed flow of pions at forward and backward rapidities to some extent, dependent of the impact parameter and beam energy while the effect on the elliptic flow is small. In addition, the effects of the magnetic field on the π – /π + ratio over the whole rapidity range and the elliptic flow difference $v$$^{n}_{2}$–$v$$^{p}_{2}$ between neutrons and protons at forward and backward rapidities are on the same order as those from the nuclear symmetry energy. Here, the $v$$^{n}_{2}$–$v$$^{p}_{2}$ difference in the midrapidity region is not strongly affected by the magnetic field, and the total π – /π + yield ratio is immune to it. It is advisable to include the magnetic field effects in future studies using pion flow, pion yield ratio, and nucleon elliptic flow difference to probe the symmetry energy at super saturation densities.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
DOE OSTI2016

Unimolecular dissociation dynamics of vibrationally activated CH 3 CHOO Criegee intermediates to OH radical products

The hydroxyl radical is a vital atmospheric oxidant, and a significant source of its production occurs through alkene ozonolysis. This takes place via a cycloaddition reaction and subsequent fragmentation to form an energized carbonyl oxide (for example, CH 3 CHOO), known as a Criegee intermediate, which can then either react with another atmospheric species or decay and, in doing so, produce the hydroxyl radical. In this work, we examine the dissociation dynamics of a prototypical Criegee intermediate by characterizing the translational and internal energy distributions of the OH radical products, which reflect critical configurations along the reaction pathway. Experimentally, the kinetic energy release to OH products is ascertained through velocity map imaging. Theoretically, quasi-classical trajectories are performed on a new full-dimensional, ab initio potential energy surface. Both experiment and theory show that most of the available energy flows into internal excitation of the vinoxy products. The isotropic angular distribution of OH fragments indicates that dissociation occurs in ≥2 ps, in agreement with theory.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1998

Conceptual Design Method Developed for Advanced Propulsion Nozzles

As part of a contract with the NASA Lewis Research Center, a simple, accurate method of predicting the performance characteristics of a nozzle design has been developed for use in conceptual design studies. The Nozzle Performance Analysis Code (NPAC) can predict the on- and off-design performance of axisymmetric or two-dimensional convergent and convergent-divergent nozzle geometries. NPAC accounts for the effects of overexpansion or underexpansion, flow divergence, wall friction, heat transfer, and small mass addition or loss across surfaces when the nozzle gross thrust and gross thrust coefficient are being computed. NPAC can be used to predict the performance of a given nozzle design or to develop a preliminary nozzle system design for subsequent analysis. The input required by NPAC consists of a simple geometry definition of the nozzle surfaces, the location of key nozzle stations (entrance, throat, exit), and the nozzle entrance flow properties. NPAC performs three analysis "passes" on the nozzle geometry. First, an isentropic control volume analysis is performed to determine the gross thrust and gross thrust coefficient of the nozzle. During the second analysis pass, the skin friction and heat transfer losses are computed. The third analysis pass couples the effects of wall shear and heat transfer with the initial internal nozzle flow solutions to produce a system of equations that is solved at steps along the nozzle geometry. Small mass additions or losses, such as those resulting from leakage or bleed flow, can be included in the model at specified geometric sections. A final correction is made to account for divergence losses that are incurred if the nozzle exit flow is not purely axial.

Nadell, Shari-Beth↗
NASA NTRS1986

Turbulent flow field predictions in sharply curved turn-around ducts

Two-dimensional turbulent flow of incompressible Newtonian fluids in sharply curved 180 deg turn around ducts is studied. Results of an approximate numerical flow field analysis utilizing an orthogonal, body-fitted, curvilinear coordinate system are compared to results based on a traditional cylindrical reference frame. Qualitative induction of general streamfield characteristics as well as quantitative benchmarks for the planning of future experimentation are provided. In addition, preliminary results of an augmented kappa - epsilon turbulence model analysis, which explicitly accounts for the effects of streamline curvature and pressure strain in internal turbulent flows, are presented. Specific model difficulties are discussed and comparisons with standard kappa - epsilon model predictions are included.

Santi, L. M.↗
NASA NTRS2000

High-Frequency Excitation of a Plane Wake

In the early 1990's, Glezer and his co-workers at Georgia Tech made a startling discovery. They found that forcing at frequencies too high to directly affect the production scales led to a dramatic alteration in the development of a turbulent shear layer. An experimental study of this phenomenon is presented in Wiltse and Glezer. They used piezoelectric actuators located near the jet exit plane to force the shear layers of a square low-speed jet. The actuators were driven at a high frequency in the Kolmogorov inertial subrange, much higher than the frequencies associated with the large-scale motion (where the turbulent energy is produced and located) but much lower than those associated with the Kolmogorov scale (where the turbulent energy is dissipated). Measurements of the shear-layer turbulence showed that direct excitation of small-scale motion by high-frequency forcing led to an increase in the turbulent dissipation of more than an order of magnitude in the initial region of the shear layer! The turbulent dissipation gradually decreased with downstream distance but remained above the corresponding level for the unforced flow at all locations examined. The high-frequency forcing increased the turbulent kinetic energy in the initial region near the actuators, but the kinetic energy decreased quite rapidly with downstream distance, dropping to levels that were a small fraction of the level for the unforced case. Perhaps most importantly from the present standpoint, the high-frequency forcing significantly decreased the energy in the large-scale motion, increasingly so with downstream distance. Wiltse and Glezer interpreted this behavior as an enhanced transfer of energy from the large scales to the small scales. The initial work by Wiltse and Glezer has expanded into other applications. To explore the potential of high-frequency forcing for active acoustic suppression, in 1998 the first author proposed a set of experiments involving an edge tone shear layer and an open cavity flow. This work was funded by the US Air Force Research Laboratory, and the experiments were developed and executed at Boeing by Raman and Kibens. These experiments involved high-frequency forcing applied to low-speed flows using wedge piezo actuators and powered resonance tubes. The system is simple, open loop, compact, potentially requires little power, and is easily integrated. Dramatic results, such as reductions of 20 dB in spectral peaks and 5-8 dB in overall levels across the entire acoustic spectrum, were obtained in some cases. Sample results are presented. Following this success in low-speed flows, an international cooperative program continuing this work involved transonic experiments in a mid-size facility in the United Kingdom. Similar reductions in noise level were obtained in these transonic experiments. Discussion of this work is given in Raman et at. and Stanek, Raman, Kibens, and Ross. Other experiments at Georgia Tech have shown significant potential of high-frequency forcing in controlling reaction rates in chemically reacting flows.

Cain, Alan B.↗
NASA NTRS1986

Turbulent flow field predictions in sharply curved turn around ducts

In this investigation, two-dimensional turbulent flow of incompressible Newtonian fluids in sharply curved 180 deg turn around ducts is studied. Results of an approximate numerical flow field analysis utilizing an orthogonal, body-fitted, curvilinear coordinate system are compared to results based on a traditional cylindrical reference frame. Qualitative indication of general streamfield characteristics as well as quantitative benchmarks for the planning of future experimentation are provided. In addition, preliminary results of an augmented kappa-epsilon turbulence model analysis, which explicitly accounts for the effects of streamline curvature and pressure strain in internal turbulent flows, are presented. Specific model difficulties are discussed and comparisons with standard kappa-esilon model predictions are included.

Santi, L. M.↗
DOE OSTI2019

First observation and characterization of vortex flow in steel micronozzles for high-pressure diesel injection

Vortex flows can be observed in many industrial systems. One of the most intricate vortex flows is the one formed in high-pressure fuel injector nozzles, which dynamics and influence on initial jet formation have been veiled due to great difficulties in observation of micro-scale fluids enclosed with steel nozzles. In this study, an X-ray tracer imaging method was used to visualize the transient fluid motion in steel micronozzles for the high-pressure diesel injection. The 1 μm-size tungsten particles were added to the diesel so that well-contrasted X-ray images of in-nozzle flows can be recorded with high-energy polychromatic X-ray beams. The X-ray images revealed, for the first time, the transient behavior of vortex flow, vortex-type cavitation and flow separation inside the steel nozzle. The needle-lift dependence of in-nozzle vortex flow dynamics was then modeled and correlated to those observed in large-scale optical nozzles in previous studies. Here, the results showed that the in-nozzle vortex and emerging jet flow characteristics of the practical nozzle were similar with those of large-scale nozzles, which suggested that the results of previous fundamental studies can be closely linked to practical cases.

42 ENGINEERING↗
DOE OSTI2014

Analytical and experimental studies of leak location and environment characterization for the international space station

The International Space Station program is developing a robotically-operated leak locator tool to be used externally. The tool would consist of a Residual Gas Analyzer for partial pressure measurements and a full range pressure gauge for total pressure measurements. The primary application is to demonstrate the ability to detect NH{sub 3} coolant leaks in the ISS thermal control system. An analytical model of leak plume physics is presented that can account for effusive flow as well as plumes produced by sonic orifices and thruster operations. This model is used along with knowledge of typical RGA and full range gauge performance to analyze the expected instrument sensitivity to ISS leaks of various sizes and relative locations (“directionality”). The paper also presents experimental results of leak simulation testing in a large thermal vacuum chamber at NASA Goddard Space Flight Center. This test characterized instrument sensitivity as a function of leak rates ranging from 1 lb{sub m/}/yr. to about 1 lb{sub m}/day. This data may represent the first measurements collected by an RGA or ion gauge system monitoring off-axis point sources as a function of location and orientation. Test results are compared to the analytical model and used to propose strategies for on-orbit leak location and environment characterization using the proposed instrument while taking into account local ISS conditions and the effects of ram/wake flows and structural shadowing within low Earth orbit.

42 ENGINEERING↗
NASA NTRS1991

Triton's global heat budget

Internal heat flow from radioactive decay in Triton's interior along with absorbed thermal energy from Neptune total 5 to 20 percent of the insolation absorbed by Triton, thus comprising a significant fraction of Triton's surface energy balance. These additional energy inputs can raise Triton's surface temperature between approx. 0.5 to 1.5 K above that possible with absorbed sunlight alone, resulting in a factor of approx. 1.5 to 2.5 increase in Triton's basal atmospheric pressure. If Triton's internal heatflow is concentrated in some areas, as is likely, local effects such as enhanced sublimation with subsequent modification of albedo could be quite large. Furthermore, indications of recent albedo change on Triton suggest that Triton's surface temperature and pressure may not now be in steady state, further suggesting that atmospheric pressure on Triton was as much as 10 times higher in the recent past.

Brown, R. H.↗
NASA NTRS2015

Effects of Distortion on Mass Flow Plug Calibration

A numerical, and experimental investigation to study the effects of flow distortion on a Mass Flow Plug (MFP) used to control and measure mass-flow during an inlet test has been conducted. The MFP was first calibrated using the WIND-US flow solver for uniform (undistorted) inflow conditions. These results are shown to compare favorably with an experimental calibration under similar conditions. The effects of distortion were investigated by imposing distorted flow conditions taken from an actual inlet test to the inflow plane of the numerical simulation. The computational fluid dynamic (CFD) based distortion study only showed the general trend in mass flow rate. The study used only total pressure as the upstream boundary condition, which was not enough to define the flow. A better simulation requires knowledge of the turbulence structure and a specific distortion pattern over a range of plug positions. It is recommended that future distortion studies utilize a rake with at least the same amount of pitot tubes as the AIP rake.

Inlets↗
NASA NTRS1979

Parameterized convection within the moon and the terrestrial planets

For a fluid layer or a self-gravitating fluid sphere uniformly heated from within, the internal temperature can be parameterized in terms of the appropriate Rayleigh number. The heat generation term includes both radioactive heat release and transient heating or cooling. This parameterization has been verified by comparisons with laboratory experiments. Thermal history calculations have been carried out for the earth, Venus, Mars, Mercury, and the moon. The results for the earth and Venus indicate that two scales of convection are occurring, one including the surface plates and the second occurring beneath the surface plates. In all cases the present heat flows are between seven and twelve per cent greater than the values obtained assuming a steady state balance between heat flow and internal heat generation.

Turcotte, D. L.↗
NASA NTRS1998

Numerical Procedures for Inlet/Diffuser/Nozzle Flows

Two primitive variable, pressure based, flux-split, RNS/NS solution procedures for viscous flows are presented. Both methods are uniformly valid across the full Mach number range, Le., from the incompressible limit to high supersonic speeds. The first method is an 'optimized' version of a previously developed global pressure relaxation RNS procedure. Considerable reduction in the number of relatively expensive matrix inversion, and thereby in the computational time, has been achieved with this procedure. CPU times are reduced by a factor of 15 for predominantly elliptic flows (incompressible and low subsonic). The second method is a time-marching, 'linearized' convection RNS/NS procedure. The key to the efficiency of this procedure is the reduction to a single LU inversion at the inflow cross-plane. The remainder of the algorithm simply requires back-substitution with this LU and the corresponding residual vector at any cross-plane location. This method is not time-consistent, but has a convective-type CFL stability limitation. Both formulations are robust and provide accurate solutions for a variety of internal viscous flows to be provided herein.

Rubin, Stanley G.↗
NASA NTRS1983

On a finite-difference method for solving transient viscous flow problems

A method has been developed to solve the unsteady, compressible Navier-Stokes equation with the property of consistency and the ability of minimizing the equation stiffness. It relies on innovative extensions of the state-of-the-art finite-difference techniques and is composed of: (1) the upwind scheme for split-flux and the central scheme for conventional flux terms in the inviscid and viscous regions, respectively; (2) the characteristic treatment of both inviscid and viscous boundaries; (3) an ADI procedure compatible with interior and boundary points; and (4) a scalar matrix coefficient including viscous terms. The performance of this method is assessed with four sample problems; namely, a standing shock in the Laval duct, a shock reflected from the wall, the shock-induced boundary-layer separation, and a transient internal nozzle flow. The results from the present method, an existing hybrid block method, and a well-known two-step explicit method are compared and discussed. It is concluded that this method has an optimal trade-off between the solution accuracy and computational economy, and other desirable properties for analyzing transient viscous flow problems.

Li, C. P.↗