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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 793 records · Page 44
All sourcesNASA NTRSDOE OSTI
NASA NTRS1993

Numerical prediction of transition of the F-16 wing at supersonic speeds

This work is part of the high speed research program currently underway at NASA. This project has the goal of gaining understanding of the technical requirements for supersonic-hypersonic flight. Specifically, this research is part of a continuing project to study the laminar flow over swept wings at high speeds and involves the numerical prediction of the flow about the F-16XL wing. The research uses the CNS/ARC3D codes and the resulting crossflow velocity components in order to estimate transition locations on the wing. Effects of angle of attack on the extent of laminar flows was found to be minimal. This result can be attributed to the fact that a laminar flow airfoil was used in this study, which has a continuous favorable pressure gradient over approximately the first 20 percent of the chord for angles of attacks up to 10 degrees. It should also be noted that even after 20 percent chord the pressure gradient either slowly continued to increase, but never decreased before 90 percent chord, except for the higher swept cases when separation occurs. Angles of attack greater than 10 degrees were not considered since this study assumes natural laminar flow for normal supersonic cruise flight conditions.

Cummings, Russell M.↗
NASA NTRS2010

Ongoing Study of Supersonic Retro-Propulsion Using Structured Overset Grids and OVERFLOW

The interest in supersonic retro-propulsion (SRP) as a means of deceleration during planetary entry increases with the desire to land high mass vehicles on Mars. Since it is difficult to obtain flight data or properly simulate this type of flow field in a wind tunnel, the use of computational fluid dynamics (CFD) becomes increasingly important, as does the need to verify the current CFD methods. This presentation will show results from structured overset grids and OVERFLOW, a Reynolds Averaged Navier-Stokes solver, obtained during the continuing CFD verification process. Flow structure, surface pressure, forces, and moments are compared to historic and modern wind tunnel data as well as to other Navier-Stokes solvers, DPLR and FUN3D. Cases include single and multiple nozzle cases from the Jarvinen and Adams experiment,i the Daso et al experiment, and a recent test in the NASA Langley Unitary Wind Tunnel (scheduled for June 2010).

Schauerhamer, Daniel Guy↗
NASA NTRS1991

Continuous wave laser absorption techniques for gasdynamic measurements in supersonic flows

Line-of-sight measurements of velocity, temperature, pressure, density, and mass flux were performed in a transient shock tube flow using three laser absorption schemes. All methods employed an intracavity-doubled ring dye laser tuned to an OH transition at 306 nm. In the first scheme, the gas was labeled by 193.3-nm excimer photolysis of H2O, and the passage of the generated OH was detected downstream. In the second method, the laser was tuned at a rate of 3 kHz over the R1(7) and R1(11) line pair, and absorption was simultaneously monitored at 90 and 60 deg with respect to the flow. Velocity was determined from the Doppler shift of the profiles and the temperature from the intensity ratio of the lines. Pressure was determined from both the magnitude of absorption and the collisional broadening. In the third method, the laser wavelength was fixed at a single frequency, and a continuous measurement of velocity and pressure was obtained using the signals from the two beam paths. All methods gave results which compare favorably to calculated values.

Davidson, David F.↗
NASA NTRS1991

A continuous mixing model for pdf simulations and its applications to combusting shear flows

The problem of time discontinuity (or jump condition) in the coalescence/dispersion (C/D) mixing model is addressed in this work. A C/D mixing model continuous in time is introduced. With the continuous mixing model, the process of chemical reaction can be fully coupled with mixing. In the case of homogeneous turbulence decay, the new model predicts a pdf very close to a Gaussian distribution, with finite higher moments also close to that of a Gaussian distribution. Results from the continuous mixing model are compared with both experimental data and numerical results from conventional C/D models.

Hsu, A. T.↗
DOE OSTI2026

Continuous Counter‐Current Microfluidic Liquid–Liquid Extraction Achieved Using a Pair of Wettable Screen Meshes

Continuous counter‐current microfluidic liquid–liquid extraction performs separations by flowing immiscible liquids in opposing directions within a single flow channel. In principle, this flow arrangement enables a large number of theoretical separation units in a small footprint, without using interstage valving, pumping, and phase separation. Despite its potential for excellent separation performance, this microfluidic scheme rarely appears in literature due to the requirement for capillary forces to be greater than hydrodynamic forces for stable flow. We present a novel microfluidic device and flow approaches that overcome this force‐balance challenge, enabling stable, long‐duration continuous counter‐current flow. Additionally, we cover a suite of methodologies for quantifying the performance of the microfluidic device, revealing the number of theoretical equilibrium stages achieved. The enabling technologies include a woven mesh screen‐based microfluidic device architecture that is easily fabricated outside of a clean room, surface functionalization strategies to promote conjugate (organic/aqueous) wettability, flow approaches to eliminate bubbles and carryover, and computer‐aided flow automation with optical measurement of extraction performance. The reported experiments lasted for over 36 h, terminated only at experiment conclusion, where the device still exhibited good performance. Automated Raman spectroscopy was used for solute quantitation of the ternary system tert‐butanol in a toluene/water matrix, a ternary system that was specifically chosen to analyze the device's performance with a small solute partition ratio and to enable in‐line Raman measurements of solute concentrations in both phases. The microfluidic device possessed a 55 mm contact length and a 38.5 µL internal volume. During counter‐current flow, we observed approximately 37 equilibrium stages (37 ± 13) based on a best‐fit of the solute fraction remaining in the aqueous phase using a Kremser Group Method analysis.

36 MATERIALS SCIENCE↗
NASA NTRS1998

International Space Station Cathode Life Testing Status

To demonstrate adequate lifetime and performance capabilities of a hollow cathode for use on the International Space Station (ISS) plasma contactor system, life tests of multiple hollow cathode assemblies (HCAs) were initiated at operating conditions simulating on-orbit operation. Three HCAs are presently being tested. These HCAs are operated with a continuous 6 sccm xenon flow rate and 3 A anode current. Emission current requirements are simulated with a square waveform consisting of 50 minutes at a 2.5 A emission current and 40 minutes with no emission current. As of July 1998, these HCAs have accumulated between 1 1,700 and 14,200 hours. While there have been changes in operatin, behavior the three HCAs continue to operate stably within ISS specifications and are expected to demonstrate the required lifetime.

Sarver-Verhey, Timothy R.↗
NASA NTRS2005

Actively Cooled SLMS(TM) Technology for HEL Applications

Mr. Jacoby is the Chief Scientist for Schafer's Lightweight Optical Systems business area with twenty four years experience in laser and optical systems for space and military applications. He and colleague Dr. Goodman conceived and developed Silicon Lightweight Mirrors (SLMS(TM)) technologies for space applications from the extreme UV to FAR IR wavelengths. Schafer has demonstrated two different methods for actively cooling our Silicon Lightweight Mirrors (SLMS(TM)) technology. Direct internal cooling was accomplished by flowing liquid nitrogen through the continuous open cell core of the SLMS(TM) mirror. Indirect external cooling was accomplished by flowing liquid nitrogen through a CTE matched Cesic square-tube manifold that was bonded to the back of the mirror in the center. Testing was done in the small 4-foot thermal/vacuum chamber located at the NASA/MSFC X-Ray Calibration Facility. Seven thermal diodes were located over the front side of the 5 inch diameter mirror and one was placed on the outlet side of the Cesic manifold. Results indicate that the mirror reaches steady state at 82K in less than four minutes for both cooling methods. The maximum temperature difference of the eight diodes was less than 200 mK when the mirror was internally cooled and covered with MLI to insulate it from the large 300 K aluminum plate that was used to mount it.

Jacoby, Marc T.↗
DOE OSTI2021

Permafrost Promotes Shallow Groundwater Flow and Warmer Headwater Streams

Abstract The presence of permafrost influences the flow paths of water through Arctic landscapes and thereby has the potential to impact stream discharge and thermal regimes. Observations from 11 headwater streams in Alaska showed that July water temperatures were higher in catchments with more near‐surface permafrost. We apply a fully coupled cryohydrology model to investigate if the impact of permafrost on flow path depth could cause the same pattern in temperatures of groundwater discharging from hillslopes to streams. The model simulates surface energy and water balances, snow, and subsurface water and energy balances for two‐dimensional hillslope model cases with varying permafrost extent. We find that hillslopes with continuous permafrost have more shallow flow paths and twice as high rates of evapotranspiration, compared to hillslopes with no permafrost. For our simulated cases, 6.7% of the horizontal water flux moves through the top organic soil layers when there is continuous permafrost, while only 0.5% moves through organic layers without permafrost. The deeper flow paths in permafrost‐free simulations buffer seasonal temperature extremes, so that summer groundwater discharge temperatures are highest with continuous permafrost. Our results suggest that permafrost thawing alters groundwater flow paths and can lead to decreases in summer stream temperatures and reductions in evapotranspiration in headwater catchments. These changes are of potential importance for stream biotic components of ecosystems, however, the full impact remains unknown.

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS1991

Non-isotropic turbulence effects on spray combustion

A numerical model for the prediction of local properties of statistically stationary spray-combusting flows is evaluated by comparison with experimental data. To appraise the relative performance of turbulence models, computations were carried out by the k-epsilon model and the algebraic stress model. The present numerical results show the qualitative agreement with experimental data. In terms of overall local flow properties, the algebraic stress model improves a degree of conformity to the experimental data due to its ability to introduce the nonisotropic turbulence effects. Two swirl numbers are considered to investigate the influence of swirl on the droplet evaporation and trajectories, and the effects of droplet/turbulence interactions in flow properties. It is found that the large swirl produces a higher evaporationn rate, and more intensive turbulent mixing and burning. The discrepancies observed in the results are attributed mainly to uncertainties in the initial spray size and velocity distributions, the droplet/wall impingement interaction, the combustion model with the fast chemistry and the turbulence models dealing with the strong streamline curvature and complex interactions between the dispersed droplets and the continuous gas-phase flows.

Kim, Y. M.↗
NASA NTRS2024

Hybrid Thermally Efficient Core (HyTEC) HyTEC Phase 1 – Advanced Aerodynamics Final Report

The objective of the Hybrid Thermally Efficient Core (HyTEC) – Advanced High Pressure Turbine (HPT) Aerodynamics project is to develop technology for a compact core that contributes to significant fuel burn reductions of 5-10% over current generation technologies. To accomplish this, the HPT is incorporating a range of aerodynamic features and technologies to improve component efficiency and provide favorable systems level trades. In particular, this project explored low solidity airfoils, advanced tip treatments, platform contouring, and advanced ceramic matrix composite (CMC) Stage 2 Nozzle (S2N) airfoils to eliminate the need for post throat cooling in a compact core environment. The maturation of these technology areas is expected to provide a significant improvement in component efficiencies, and consequently reductions in fuel burn, over the current state of the art (SoA). To mature these technologies to Technology Readiness Level (TRL) 4, a test campaign was performed that consisted of four tests at three facilities. TRL 3 testing was performed in the CW22 linear cascade at NASA Glenn for blade and nozzle technologies, TRL 4 nozzle testing was performed at GE Aerospace (GEA) Test Cell A8, and TRL 4 blade testing was performed at the Notre Dame Turbomachinery Laboratory (NDTL) using the Transonic Research Turbine (TRT) rig. Low solidity was successfully demonstrated to a TRL 4 level. Low solidity nozzles showed benefits in line with pre-project expectations, while low solidity blades were shown to have an aerodynamic penalty. Crucially, this program only considered the aerodynamic losses, and systems trades such as reductions in cooling flows are expected to continue to make low solidity blades a net positive. By successfully quantifying the aerodynamic performance in this project, these trades can be conducted to determine where in the engine architecture low solidity blades will contribute positively to system operation. Platform contouring was demonstrated to a TRL 4 level, with performance in line with the lower end of the pre-project expected range. Advanced tip treatments performance levels were indeterminate, showing the expected improvements to flow physics but with a performance level confounded by several rig issues including whirl mode induced variation in tip clearance. The elimination of post-throat cooling on the S2N was successfully demonstrated to provide a performance benefit, however that benefit was approximately half the level that was expected in pre-project predictions. Overall, the technology maturation plan for HyTEC Phase 1 was successful, bringing the suite of technologies to TRL 4.

High pressure turbine↗
NASA NTRS1997

International Space Station Cathode Life Testing

Four hollow cathode assembly (HCA) life tests were initiated at operating conditions simulating on-orbit operation of the International Space Station plasma contactor. The objective of these tests is to demonstrate the mission-required 18,000 hour lifetime with high-fidelity development model HCAS. HCAs are operated with a continuous 6 sccm xenon flow rate and 3 A anode current. On-orbit emission current requirements are simulated with a square waveform consisting of 50 minutes at a 2.5 A emission current and 40 minutes with no emission current. One HCA test was terminated after approximately 8,000 hours so that a destructive analysis could be performed. The analysis revealed no life-limiting processes and the ultimate lifetime was projected to be greater than the mission requirement. Testing continues for the remaining three HCAs which have accumulated approximately 8,000 hours, 10,000 hours, and 11,000 hours, respectively, as of June 1997. Anode and bias voltages, strong indicators of cathode electron emitter condition, are within acceptable ranges and have exhibited no life- or performance-limiting phenomena to date.

Soulas, George C.↗
NASA NTRS1979

Experimental evaluation of a pilot multinozzle-duct apparatus

A pilot multinozzle and duct were tested at ambient enthalpy to evaluate the suitability of such apparatus for testing thermal protection system panels mounted in the sidewalls of the duct downstream of the nozzle array. The flow field in the duct was complex: effects of wakes and shock waves from the nozzle dominated the flow field; the wakes continually mixed with the surrounding fluid; the boundary layer on the sidewalls of the duct was nonuniform; and near the exit of the duct the sidewall pressure variation was as much as 8.5 percent about the mean wall pressure. Starting loads on the duct walls were higher than those of a similar conventional nozzle and duct. It was concluded that the multinozzle-duct apparatus was not suitable for testing TPS panels, although the design and flow-field information should be of interest to designers of high-energy gasdynamic lasers.

Puster, R. L.↗
NASA NTRS1973

Computer program for the prediction of reorientation flow dynamics

Program uses Navier-Stokes and continuity equations for incompressible, viscous fluid as the basic equations governing reorientation flow dynamics. Program can simulate curved as well as straight-walled boundaries; has ability to calculate both free-surface and confined flows; and can be used in either cylindrical or plane geometry.

Betts, W. S., Jr.↗
DOE OSTI2022

Effect of Initial Water Saturation on The Performance of Fracturing Fluids With and Without Polyallylamine under Simulated EGS Conditions

Objectives/Scope: StimuFrac (US Patents 9,873,828 B2 and 9,447,315 B2), a CO2-reactive polymer aqueous solution [polyallylamine (PAA) 1wt% in water] combined with CO2, can be used as a less water-intensive fracturing fluid for enhanced geothermal systems (EGS). Our previous results show that in hot dry rock (HDR), PAA/CO2 fracturing fluids outperformed other fluids such as water, CO2, and CO2/water in generating large fractures with less fluid consumed. The objective of this work is to study the effect of initial water saturation of rock on the performance of StimuFrac fluid in ½ foot cubic rock samples and under representative EGS pressure/temperature conditions using cyclic and constant flow rate injection strategies. The fracturing results are compared with results using different fracturing fluids in terms of controlling fracture propagation rates, fracture hydraulic conductivity, breakdown pressures and volumes of fluids required. Methods/Procedures/Process: In all tests, water was initially injected into the rock to increase the water saturation before the fracturing processes to simulate actual geothermal reservoir conditions. For the cyclic injection, one complete cycle consisted of (1) a PAA slug (or water slug) injection followed by (2) CO2 injection to initiate the fracture. In the second step of the first cycle, the pressure of CO2 is increased until a maximum pressure is reached (fracture is initiated at this moment), and then the injection of CO2 is allowed for another 30 seconds to propagate the fracture. Then, the two-step cycle of PAA followed by CO2 injection (up to 2-4 mL/min) was continued. For the constant flow rate injection strategies, the initial water saturation was increased by injecting water at 1000 psi and 200°C for three days. After that, an initial slug of water, CO2, or PAA was injected and then fracturing was initiated and propagated by injecting CO2 at a constant flow rate. Applications/Significance/Novelty: The results of this study suggest that water saturation, especially near the wellbore region, will significantly affect the fracturing fluid transmission into the rock porous media by changing the relative permeability of CO2 or water, thus affecting the fracture initiation and propagation. In this study, fracturing with cyclic injection or constant flow rate injection methods were performed using three different kinds of fluids systems. These fluids are water, CO2, or CO2 with PAA. Splitting the rock samples in half after fracturing reveals that the fracture propagation is significantly limited under these high water saturated conditions compared to dry initial conditions: The fractures propagate less than 1/3 length of the distance from the wellbore to rock surface, and in some cases no fracture is generated. This may be caused by the fact that leak-off is dominating the fracturing process and the injected fluid flow rate is not high enough to overcome the leak-off even under high flow rate injection conditions. Additionally, CO2 could be leaking off into the wellbore annulus and this may be making it more difficult to generate pressure gradients away from the near-wellbore region.

Jian, Guoqing↗
NASA NTRS1980

Influence of pressure driven secondary flows on the behavior of turbofan forced mixers

A finite difference procedure was developed to analyze the three dimensional subsonic turbulent flows in turbofan forced mixer nozzles. The method is based on a decomposition of the velocity field into primary and secondary flow components which are determined by solution of the equations governing primary momentum, secondary vorticity, thermal energy, and continuity. Experimentally, a strong secondary flow pattern was identified which is associated with the radial inflow and outflow characteristics of the core and fan streams and forms a very strong vortex system aligned with the radial interface between the core and fan regions. A procedure was developed to generate a similar generic secondary flow pattern in terms of two constants representing the average radial outflow or inflow in the core and fan streams as a percentage of the local streamwise velocity. This description of the initial secondary flow gave excellent agreement with experimental data. By identifying the nature of large scale secondary flow structure and associating it with characteristic mixer nozzle behavior, it is felt that the cause and effect relationship between lobe design and nozzle performance can be understood.

Anderson, B.↗
NASA NTRS1993

The heart works against gravity

The circulatory systems of vertebrate animals are closed, and blood leaves and returns to the heart at the same level. It is often concluded, therefore, that the heart works only against the viscous resistance of the system, not against gravity, even in vascular loops above the heart in which the siphon principle operates. However, we argue that the siphon principle does not assist blood flow in superior vascular loops if any of the descending vasculature is collapsible. If central arterial blood pressure is insufficient to support a blood column between the heart and the head, blood flow ceases because of vascular collapse. Furthermore, the siphon principle does not assist the heart even when a continuous stream of blood is flowing in a superior loop. The potential energy gained by blood as it is pumped to the head is lost to friction in partially collapsed descending vessels and thus is not regained. Application of the Poiseuille equation to flow in collapsible vessels is limited; resistance depends on flow rate in partially collapsed vessels with no transmural pressure difference, but flow rate is independent of resistance. Thus the pressure developed by the heart to establish a given flow rate is independent of the resistance occurring in the partially collapsed vessels. The pressure depends only on the height of the blood column and the resistance in the noncollapsed parts of the system. Simple laboratory models, involving water flow in collapsible tubing, dispel the idea that the siphon principle facilitates blood flow and suggest that previously published results may have been affected by experimental artifact.

Review, Tutorial↗
DOE OSTI2023

Geometric Optimization of an Electrochemical Purification Cell to Prevent Corrosion in CSP Plants During Operation

When exposed to moisture or oxygen, molten chloride salts produce corrosive impurities which degrade containment alloys. This can significantly decrease the lifetime and increase costs of molten-salt-based systems. To overcome this barrier, we designed and modeled an electrochemical purification cell to remove the corrosive impurity MgOH+. Various reactor architectures, including continuous stirred tank reactors (CSTRs) and plug flow reactors (PFRs) were investigated. Steady-state thermoelectric properties were evaluated using analytical methods, allowing assessment of the effects of structure and design parameters such as flow rate, cell length, and cross-sectional area of molten salt. The results suggest that our design could most effectively increase reliability and decrease costs of molten-chloride-salt-based systems by protecting them during continuous operation using an annular plug flow reactor.

analytical modeling↗