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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 487 records · Page 27
All sourcesNASA NTRSDOE OSTI
NASA NTRS1960

Effect on Gaseous Film Cooling of Coolant Injection Through Angled Slots and Normal Holes

A study was made to determine the effect of coolant injection angularity on gaseous film-cooling effectiveness. In the correlation of experimental data an effective injection angle was defined by a vector summation of the coolant and mainstream gas flows. The cosine of this angle was used as a parameter to empirically develop a corrective term to qualify a correlating equation presented in Technical Note D-130 that was limited to tangential injection of the coolant. Data were also obtained for coolant injection through rows of holes normal to the test plate. The slot correlating equation was adapted to fit these data by the definition of an effective slot height. An additional corrective term was then determined to correlate these data.

Papell, S. Stephen↗
NASA NTRS2014

Effects of Spent Cooling and Swirler Angle on a 9-Point Swirl-Venturi Injector

This paper presents multipoint Lean-Direct-Injection (LDI) emissions results for flame tube combustion tests at an inlet pressure of 1034 kPa and inlet temperatures between 835 and 865 K; these are the combustor inlet conditions that the High Speed Research (HSR) program used for supersonic cruise. It focuses on one class of LDI geometry, 9-point swirl-venturi LDI (SV-LDI). Two parameters are compared in this paper: the use of dome cooling air and the swirler blade angle. Dome cooling air is called "spent cooling" and is at combustor inlet conditions. Three cooling variations are studied: cooling at the venturi throat, cooling at the dome face, and no cooling at all. Two swirler blade angles are studied: 45deg and 60deg. The HSR 9-point SV-LDI emissions are also compared to a similar 9-point SV-LDI design which was used in the later ultra-efficient engine technology (UEET) program. The HSR and UEET designs cannot be compared directly due to different UEET combustor conditions. Therefore, this paper uses previously published UEET correlation equations to make comparisons. Results show that using a 45deg swirler produces lower NOx emissions than using a 60deg swirler. This is consistent with the later UEET results. The effects of spent cooling depend on swirler angle, spent cooling location, and the test conditions. For the configuration with 45deg swirlers, spent cooling delivers lower NOx emissions when it is injected at the throat. For the 60deg swirler, spent cooling does not have much effect on NOx emissions. These results might be caused by the location and the intensity of the flame recirculation zone.

He, Zhuohui J.↗
NASA NTRS2013

Effects of Spent Cooling and Swirler Angle on a 9-point Swirl-Venturi Injector

This paper presents multipoint lean-direct-injection (LDI) emissions results for flame tube combustion tests at an inlet pressure of 1034 kPa and inlet temperatures between 835 and 865 K; these are the combustor inlet conditions that the High Speed Research (HSR) program used for supersonic cruise. It focuses on one class of LDI geometry, 9-point swirl-venturi LDI (SV-LDI). Two parameters are compared in this paper: the use of dome cooling air and the swirler blade angle. Dome cooling air is called 'spent cooling' and is at combustor inlet conditions. Three cooling variations are studied: cooling at the venturi throat, cooling at the dome face, and no cooling at all. Two swirler blade angles are studied: 45 deg and 60 deg. The HSR 9-point SV-LDI emissions are also compared to a similar 9-point SV-LDI design which was used in the later ultra-efficient engine technology (UEET) program. The HSR and UEET designs cannot be compared directly due to different UEET combustor conditions. Therefore, this paper uses previously published UEET correlation equations to make comparisons. Results show that using a 45 deg swirler produces lower NOx emissions than using a 60 deg swirler. This is consistent with the later UEET results. The effects of spent cooling depend on swirler angle, spent cooling location, and the test conditions. For the configuration with 45 deg swirlers, spent cooling delivers lower NOx emissions when it is injected at the throat. For the 60 deg swirler, spent cooling does not have much effect on NOx emissions. These results might be caused by the location and the intensity of the flame recirculation zone.

He, ZH., Joe↗
NASA NTRS1980

Curved film cooling admission tube

Effective film cooling to protect a wall surface from a hot fluid which impinges on or flows along the surface is provided. A film of cooling fluid having increased area is provided by changing the direction of a stream of cooling fluid through an angle of from 135 deg. to 165 deg. before injecting it through the wall into the hot flowing gas. The 1, cooling fluid is injected from an orifice through a wall into a hot flowing gas at an angle to form a cooling fluid film. Cooling fluid is supplied to the orifice from a cooling fluid source via a turbulence control passageway having a curved portion between two straight portions. The angle through which the direction of the cooling fluid is turned results in less mixing of the cooling fluid with the hot gas, thereby substantially increasing the length of the film in a downstream direction.

Graham, R. W.↗
NASA NTRS1992

Effects of turbine cooling assumptions on performance and sizing of high-speed civil transport

The analytical study presented examines the effects of varying turbine cooling assumptions on the performance of a high speed civil transport propulsion system as well as the sizing sensitivity of this aircraft to these performance variations. The propulsion concept employed in this study was a two spool, variable cycle engine with a sea level thrust of 55,000 lbf. The aircraft used for this study was a 250 passenger vehicle with a cruise Mach number of 2.4 and 5000 nautical mile range. The differences in turbine cooling assumptions were represented by varying the amount of high pressure compressor bleed air used to cool the turbines. It was found that as this cooling amount increased, engine size and weight increased, but specific fuel consumption (SFC) decreased at takeoff and climb only. Because most time is spent at cruise, the SFC advantage of the higher bleed engines seen during subsonic flight was minimized and the lower bleed, lighter engines led to the lowest takeoff gross weight vehicles. Finally, the change in aircraft takeoff gross weight versus turbine cooling level is presented.

Senick, Paul F.↗
NASA NTRS1992

Effects of turbine cooling assumptions on performance and sizing of high-speed civil transport

The analytical study presented examines the effects of varying turbine cooling assumptions on the performance of a high speed civil transport propulsion system as well as the sizing sensitivity of this aircraft to these performance variations. The propulsion concept employed in this study was a two spool, variable cycle engine with a sea level thrust of 55,000 lbf. The aircraft used for this study was a 250 passenger vehicle with a cruise Mach number of 2.4 and 500 nautical mile range. The differences in turbine cooling assumptions were represented by varying amount of high pressure compressor bleed air used to cool the turbines. It was found that as this cooling amount increased, engine size and weight increased, but specific fuel consumption (SFC) decreased at takeoff and climb only. Because most time is spent at cruise, the SFC advantage of the higher bleed engines seen during subsonic flight was minimized and the lower bleed, lighter engines led to the lowest takeoff gross weight vehicles. Finally, the change in aircraft takeoff gross weight versus turbine cooling level is presented.

Senick, Paul F.↗
NASA NTRS1999

EEG Analysis of the Effects of Therapeutic Cooling on the Cognitive Performance of Multiple Sclerosis Patients

The objective of this project was to determine whether a controlled period of head and torso cooling would enhance the cognitive performance of multiple sclerosis patients. Nineteen MS patients (11 men and 8 women) participated in the study. Control data were taken from nineteen healthy volunteers (12 men and 7 women). All but six of nineteen MS patients tested improved their cognitive performance, as measured by their scores on the Rao test battery. A second objective was to gain insight into the neurological effects of cooling. Visual evoked potentials (VEPs) stimulated by a reversing checkerboard pattern were recorded before and after cooling. We found that cooling selectively benefited the cognitive performance of those MS patients whose pre-cooling VEPs were abnormally shaped (which is an indication of visual pathway impairment due to demyelinization). Moreover, for female MS patients, the degree of cognitive performance improvement following cooling was correlated with a change in the shape of their VEPs toward a more normal shape following cooling.

Montgomery, Leslie D.↗
DOE OSTI2022

Bifunctional Asymmetric Fabric with Tailored Thermal Conduction and Radiation for Personal Cooling and Warming

Personal thermal management is emerging as a promising strategy to provide thermal comfort for the human body while conserving energy. By improving control over the heat dissipating from the human body, personal thermal management can provide effective personal cooling and warming. Here, we propose a facile surface modification approach to tailor the thermal conduction and radiation properties based on commercially available fabrics, to realize better management of the whole heat transport pathway from the human body to the ambient. Additionally, a bifunctional asymmetric fabric (BAF) offering both a cooling and a warming effect is demonstrated. Due to the advantages of roughness asymmetry and surface modification, the BAF demonstrates an effective cooling effect through enhanced heat conduction and radiation in the cooling mode; in the warming mode, heat dissipation along both routes is reduced for personal warming. As a result, a 4.6 °C skin temperature difference is measured between the cooling and warming BAF modes, indicating that the thermal comfort zone of the human body can be enlarged with one piece of BAF clothing. We expect this work to present new insights for the design of personal thermal management textiles as well as a novel solution for the facile modification of available fabrics for both personal cooling and warming.

42 ENGINEERING↗
NASA NTRS1949

Effect of Air Cooling of Turbine Disk on Power and Efficiency of Turbine from Turbo Engineering Corporation TT13-18 Turbosupercharger.

An investigation was conducted to determine the effect of turbine-disk cooling with air on the efficiency and the power output of the radial-flow turbine from the Turbo Engineering Corporation TT13-18 turbosupercharger. The turbine was operated at a constant range of ratios of turbine-inlet total pressure to turbine-outlet static pressure of 1,5 and 2.0, turbine-inlet total pressure of 30 inches mercury absolute, turbine-inlet total temperature of 12000 to 20000 R, and rotor speeds of 6000 to 22,000 rpm, Over the normal operating range of the turbine, varying the corrected cooling-air weight flow from approximately 0,30 to 0.75 pound per second produced no measurable effect on the corrected turbine shaft horsepower or the turbine shaft adiabatic efficiency. Varying the turbine-inlet total temperature from 12000 to 20000 R caused no measurable change in the corrected cooling-air weight flow. Calculations indicated that the cooling-air pumping power in the disk passages was small and was within the limits of the accuracy of the power measurements. For high turbine power output, the power loss to the compressor for compressing the cooling air was approximately 3 percent of the total turbine shaft horsepower.

Berkey, William E.↗
DOE OSTI2022

Investigation of Gas Turbine Internal Cooling Using Supercritical CO 2 —Effect of Surface Roughness and Channel Aspect Ratio

In this paper, an experimental and numerical investigation of internal cooling channels with rib turbulators is presented with sCO 2 as the working fluid at process conditions (pressure-20.7 MPa and temperature up to 150 °C). The effect of channel aspect ratio up to 2:1 on thermal-hydraulic performance is explored in additively manufactured rectangular channels and square channels, both with and without 60 deg ribs on the top and bottom sides. The Wilson-plot method is employed to experimentally measure channel-averaged Nusselt number over a Reynolds number range up to 370,000. The friction factor is calculated from pressure drop and mass flow rate and additionally, the overall thermal performance factor (TPF) is reported. A companion computational fluid dynamics (CFD) simulation is performed for the rib turbulated cooling configurations reported in the experiments using the Reynolds average Navier–Stokes-based turbulence model. The objective of the numerical study is to gain insight into the local heat transfer augmentation in the ribbed channels as a result of varying the aspect ratio, channel configuration (square versus rectangular), operating conditions (Reynolds number) and the surface roughness, an inherent outcome of the additive manufacturing process. Surface roughness is simulated using sand grain roughness height (K S ) calculated from the experimental data, and a comparison is presented with the corresponding channel configuration with varying surface roughness heights starting from smooth surfaces (K S = 0). Experimental results indicate that the heat transfer augmentation is negligible in the rectangular channels with ribs on the long side compared to the square channel. However, it is enhanced by 60% in comparison to placing ribs on the shorter side. The TPF remains constant at around 1 for the entire range of Reynolds numbers consistent with prior work at the National Energy Technology Laboratory (NETL). Here, the simulation results highlight that increased surface roughness can have a favorable considerable influence on Nusselt number and overall thermal performance enhancement.

42 ENGINEERING↗
NASA NTRS2000

Unsteady High Turbulence Effects on Turbine Blade Film Cooling Heat Transfer Performance Using a Transient Liquid Crystal Technique

Unsteady wake effect, with and without trailing edge ejection, on detailed heat transfer coefficient and film cooling effectiveness distributions is presented for a downstream film-cooled gas turbine blade. Tests were performed on a five-blade linear cascade at an exit Reynolds number of 5.3 x 10(exp 5). Upstream unsteady wakes were simulated using a spoke-wheel type wake generator. Coolant blowing ratio was varied from 0.4 to 1.2; air and CO2 were used as coolants to simulate different density ratios. Surface heat transfer and film effectiveness distributions were obtained using a transient liquid crystal technique; coolant temperature profiles were determined with a cold wire technique. Results show that Nusselt numbers for a film cooled blade are much higher compared to a blade without film injection. Unsteady wake slightly enhances Nusselt numbers but significantly reduces film effectiveness versus no wake cases. Nusselt numbers increase only slic,htly but film cooling, effectiveness increases significantly with increasing, blowing ratio. Higher density coolant (CO2) provides higher effectiveness at higher blowing ratios (M = 1.2) whereas lower density coolant (Air) provides higher 0 effectiveness at lower blowing ratios (M = 0.8). Trailing edge ejection generally has more effect on film effectiveness than on the heat transfer, typically reducing film effectiveness and enhancing heat transfer. Similar data is also presented for a film cooled cylindrical leading edge model.

Han, J. C.↗
NASA NTRS1993

Venus pancake dome formation: Morphologic effects of a cooling-induced variable viscosity during emplacement

The distinctive steep-sided 'pancake' domes discovered in the Magellan images of Venus have morphologies that suggest formation by a single continuous emplacement of a high viscosity magma. A resemblance of the venusian domes to much smaller terrestrial rhyolite and dacite volcanic domes has prompted some authors to suggest that the domes on Venus also have high silica compositions and thus, high viscosities. However, viscosity is a function of crystallinity as well as silica content in a magma, and thus increases as a result of magmatic cooling. To investigate the effect of a cooling-induced viscosity increase on dome morphology, we have modeled the domes as radial viscous gravity currents that cool during emplacement. Various aspects of the investigation are discussed.

Sakimoto, S. E. H.↗
NASA NTRS2001

Icehouse Effect: A Selective Arctic Cooling Trend Current Models are Missing

The icehouse effect is a hypothesized climate feedback mechanism which could result in human-caused surface cooling trends in polar regions. Once understood in detail, it becomes apparent that these trends, which are discernable in the literature, but have been largely dismissed, do not conflict with the consensus assessment of the evidence, which infers century-scale Arctic warming. In fact, confirmation of the hypothesis would substantially strengthen the argument that there is a detectable human influence on today's climate. This apparent enigma is resolved only through careful attention to the detail of the hypothesis and the data supporting it. The posited surface cooling is entirely dependent on the existence of climate warming in layers capping the stable boundary layer. Also, the cooling is not pandemic, but is selective. It is readily revealed in properly sorted data by making use of the principles of micrometeorological similarity. Specifically, the cooling is manifest under a range of favorable turbulence conditions which can develop and disappear locally on time scales of minutes to hours because of the intrinsically intermittent nature of stable boundary layer turbulence. Because of the fine-scale nature of the processes which produce the cooling, modeling it is a difficult proposition. Vertical resolution on the order of 1 meter is required. Adequate models of intermittent surface fluxes coupled with radiation exchange do not currently exist, not as parameterizations for aggregated systems, nor in large eddy simulation (LES) models. This presentation will introduce the theory. An important testable null hypothesis emerges: the icehouse effect produces a unique signature or "fingerprint" which could not be produced by any other known process. The presence of this signature will be demonstrated using nearly all available Arctic temperature observations. Its aggregate effect is clearly found in Arctic monthly surface temperature trends when sorted by climatological stability. Using all available Arctic rawinsonde ascents - about 1.1 million profiles, "frozen moments" of the icehouse processes are captured in various states. Because turbulent time scales are so short in the stable boundary layer. each of these snapshots can be treated as independent -- their chronology is irrelevant. Micrometeorological similarity is invoked to reassemble the soundings into bins of similar stability and it is in a wide, coherent range of these stability bins where the cooling effect is revealed.

Wetzel, Peter J.↗
NASA NTRS1979

An experimental investigation to determine the effect of window cooling by mass injection for the Shuttle Infrared Leeside Temperature Sensing (SILTS) experiment

The effect of mass injection on the shuttle infrared leeside temperature sensing (SILTS) pod window surfaces in reducing window heating and minimizing window lens radiation during the reentry data taking period is investigated. Heat transfer coefficients on and around the simulated windows and window cavities are determined. Heat transfer rates and window coolant flow rates are reported for the SILTS configuration. A comparison of two windows' geometries and their effects on the heat transfer rate is discussed and oil flow photographs are presented to indicate how mass injection affects the flow field near the SILTS window.

Bradley, P. F.↗
DOE OSTI2019

Effect of Interlayer Cooling Time, Constraint and Tool Path Strategy on Deformation of Large Components Made by Laser Metal Deposition with Wire

Laser metal deposition with wire (LMD-w) is a developing additive manufacturing (AM) technology that has a high deposition material rate and efficiency and is suitable for fabrication of large aerospace components. However, control of material properties, geometry, and residual stresses is needed before LMD-w technology can be widely adopted for the construction of critical structural components. In this study, we investigated the effect of interlayer cooling time, clamp constraints, and tool path strategy on part distortion and residual stresses in large-scale laser additive manufactured Ti-6Al-4V components using finite element method (FEM). The simulations were validated with the temperature and the distortion measurements obtained from a real LMD-w process. We found that a shorter interlayer cooling time, full clamping constraints on the build plates, and a bidirectional tool path with 180° rotation minimized part distortion and residual stresses and resulted in symmetric stress distribution.

36 MATERIALS SCIENCE↗
NASA NTRS1992

Effects of the cooling system parameters on heat transfer and performance of the PAFC stack during transient operation

An experimental investigation for the effects of transient operation of a phosphoric acid fuel-cell stack on heat transfer and temperature distribution in the electrodes has been conducted. The proposed work utilized the experimental setup with modifications, which was designed and constructed under NASA Contract No. NCC-3-17(5). The experimental results obtained from this investigation and the mathematical model obtained under NASA Contract No. NCC3-17(4) after modifications, were utilized to develop mathematical models for transient heat transfer coefficient and temperature distribution in the electrode and to evaluate the performance of the cooling - system under unsteady state conditions. The empirical formulas developed were then implemented to modifying the developed computer code. Two incompressible coolants were used to study experimentally the effect of the thermophysical properties of the cool-ants on the transient heat transfer coefficient and the thermal contact resistance during start-up and shut-down processes. Coolant mass flow rates were verified from 16 to 88.2 Kg/hr during the transient process when the electrical power supply was gradually increased or decreased in the range (O to 3000 W/sq m). The effect of the thermal contact resistance with a range of stack pressure from O to 3500 KPa was studied.

Ridha, Rabi M. J.↗
DOE OSTI2020

Dispersion effect on the cooling rates

It is known that dispersion can redistribute the electron cooling rate between longitudinal and transverse planes. This note presents a simple analytical model to explain and estimate this redistribution effect. It shows that a small horizontal dispersion on ions can enhance horizontal cooling at the expense of longitudinal cooling rate. The electron dispersion is also beneficial to this effect.

43 PARTICLE ACCELERATORS↗
NASA NTRS1942

The Effect of Valve Cooling upon Maximum Permissible Engine Output as Limited by Knock

A Wright GR-1820-G200 cylinder was tested over a wide range of fuel-air ratios at maximum permissible power output as limited by knock with three different degrees of valve cooling. The valves used were stock valves (solid inlet valve and hollow sodium-cooled exhaust valve), hollow valves with no coolant, and hollow valves with flowing water as a coolant. Curves showing the variation in maximum permissible values of inlet-air pressure, indicated mean effective pressure, cylinder charge, and indicated specific fuel consumption with change in fuel-air ratio and valve cooling are shown. The use of valves cooled by a stream of water passing through their hollow interiors permitted indicated mean effective pressures 10 percent higher than the mean effective pressures permissible with stock valves when the engine was operated with fuel-air ratios from 0.055 to 0.065. Operation of the engine with lean mixtures with uncooled hollow valves resulted in power output below the output obtained with the stock valves. The data show an increase in maximum permissible indicated mean effective pressure due to cooling the valves, which averages only 2.1 percent with fuel-air ratios from 0.075 to 0.105.

Munger, Maurice↗