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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 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
NASA NTRS2010

Supersonic Free-Jet Combustion in a Ramjet Burner

A new dual-mode ramjet combustor concept intended for operation over a wide flight Mach number range is described. Subsonic combustion mode is similar to that of a traditional ram combustor which allows operation at higher efficiency, and to lower flight Mach numbers than current dual-mode scramjets. High speed mode is characterized by supersonic combustion in a free-jet that traverses the subsonic combustion chamber to a variable nozzle. The maximum flight Mach number of this scheme is governed largely by the same physics as its classical counterpart. Although a variable combustor exit aperture is required, the need for fuel staging to accommodate the combustion process is eliminated. Local heating from shock-boundary-layer interactions on combustor walls is also eliminated. Given the parallel nature of the present scheme, overall flowpath length is less than that of present dual-mode configurations. Cycle analysis was done to define the flowpath geometry for computational fluid dynamics (CFD) analysis, and then to determine performance based on the CFD results. CFD results for Mach 5, 8, and 12 flight conditions indicate stable supersonic free-jet formation and nozzle reattachment, thereby establishing the basic feasibility of the concept. These results also reveal the structure of, and interactions between the free-jet and recirculating combustion chamber flows. Performance based on these CFD results is slightly less than that of the constant-pressure-combustion cycle analysis primarily due to these interactions. These differences are quantified and discussed. Additional CFD results at the Mach 8 flight condition show the effects of nozzle throat area variation on combustion chamber pressure, flow structure, and performance. Calculations with constant temperature walls were also done to evaluate heat flux and overall heat loads. Aspects of the concept that warrant further study are outlined. These include diffuser design, ramjet operation, mode transition, loss mechanisms, and the effects of secondary flow for wall cooling and combustion chamber pressurization. Also recommended is an examination of system-level aspects such as weight, thermal management and rocket integration as well as alternate geometries and variable geometry schemes.

Trefny, Charles J.↗
DOE OSTI2024

A computational analysis of effective R-values of buried ducts – the dynamic performance of buried ducts

Here, this paper evaluates the thermal performance of ducts partially or fully buried in loose-fill attic insulation. The overall thermal resistance between the ducts and the attic is referred to as an effective R-value. This paper shows a strong dependency of assumed attic temperature on the effective R-value. Based on the results, the effective R-value can be about twice as much with an attic temperature of 130 °F [54.4 °C], compared to when the attic temperature is 80 °F [26.7 °C]. Thus, this paper provides a polynomial regression equation based on a large set of simulations to determine the effective R-value of buried ducts depending on attic temperature and whether the HVAC system runs in cooling or heating mode. Further, the work presented in this paper investigated the potential impact of convective airflow within the attic insulation, particularly around the ducts. The analysis was based on computational fluid dynamics (CFD) and indicated that convectional forces are presented around the exterior surface of the ducts, but with negligible impact on the overall heat balance between the duct and the attic space.

97 MATHEMATICS AND COMPUTING↗
DOE OSTI2020

The Installation of Direct Water-Cooling Systems to Reduce Cooling Energy Requirements for High-Performance Computing Centers

A large cluster of High-Performance Computing (HPC) equipment at the Lawrence Livermore National Laboratory in California was retrofitted with an Asetek cooling system. The Asetek system is a hybrid scheme with water-cooled cold plates on high-heat-producing components in the information technology (IT) equipment, and with the remainder of the heat being removed by conventional air-cooling systems. In order to determine energy savings of the Asetek system, data were gathered and analyzed two ways: using top-down statistical models, and bottom-up engineering models. The cluster, “Cabernet”, rejected its heat into a facilities cooling water loop which in turn rejected the heat into the same chilled water system serving the computer-room air handlers (CRAHs) that provided the air-based cooling for the room. Because the “before” and “after” cases both reject their heat into the chilled water system, the only savings is due to reduction in CRAH fan power. The top-down analysis showed a 4% overall energy savings for the data center (power usage effectiveness (PUE) —the ratio of total data center energy to IT energy— dropped from 1.60 to 1.53, lower is better); the bottom-up analysis showed a 3% overall energy savings (PUE from 1.70 to 1.66) and an 11% savings for the Cabernet system by itself (partial PUE of 1.51). Greater savings, on the order of 15-20%, would be possible if the chilled water system was not used for rejecting the heat from the Asetek system. About 37% of the heat from the Cab system was rejected to the cooling water, lower than at other installations.

Earni, Shankar↗
DOE OSTI2023

Concurrent Cooling Effects of Dynamic Line Ratings on Wind Plant Gen-Tie Lines

This report was prepared for the Wind Energy Technology Office for the FY 2022, quarter 2 deliverable. This details the use of dynamic line rating technology to rate a series of gen tie lines connecting wind plants to the regional transmission lines. This consists of two primary study regions, the first on the desert west of Idaho Falls, and the second in the region east of the Cascades along the Columbia River Gorge. The TREAD program that was developed at INL was used to create generated gen-tie lines based on nearby regional transmission line connections. The capacity availability of the gen tie lines are compared with the power production of the wind farms. Overall, the INL Site location shows a much greater capacity for the gen-tie lines due to the higher wind speeds. Across both locations, the HRRR data shows higher wind speeds than observed at the observational weather stations. For both the Columbia Gorge and Idaho areas, the sites show that a statically rate gen-tie could carry additional capacity far above the rated during periods of high wind due to the concurrent cooling effects.

17 WIND ENERGY↗
NASA NTRS1975

Cold-air annular-cascade investigation of aerodynamic performance of core-engine-cooled turbine vanes. 1: Solid-vane performance and facility description

The aerodynamic performance of a solid (uncooled) version of a core engine cooled stator vane was experimentally determined in a full-annular cascade, where three-dimensional effects could be obtained. The solid vane, which serves as a basis for comparison with subsequent cooled tests, was tested over a range of aftermixed critical velocity ratios of 0.57 to 0.90. Overall vane aftermixed efficiencies were obtained over this critical velocity ratio range and compared with results from a two-dimensional cascade. The variation in vane efficiency and aftermixed flow conditions with circumferential and radial position were obtained and compared with design values. Vane surface static-pressure distributions were also measured and compared with theoretical results.

Goldman, L. J.↗
NASA NTRS1936

Performance of Air-cooled Engine Cylinders Using Blower Cooling

An investigation was made to obtain information on the minimum quantity of air and power required to cool conventional air cooled cylinders at various operating conditions when using a blower. The results of these tests show that the minimum power required for satisfactory cooling with an overall blower efficiency of 100 percent varied from 2 to 6 percent of the engine power depending on the operating conditions. The shape of the jacket had a large effect on the cylinder temperatures. Increasing the air speed over the front of the cylinder by keeping the greater part of the circumference of the cylinder covered by the jacket reduced the temperatures over the entire cylinder.

Schey, Oscar W↗
DOE OSTI2022

Transformational challenge reactor design characteristics

The Transformational Challenge Reactor (TCR) program was conceived with the goal to reduce costs and time frames associated with advanced reactor deployment by leveraging developments in advanced manufacturing, advanced materials, data science, and rapid prototyping and testing. The final deliverable of the TCR program was to be an operational test of a novel reactor design. The TCR core design incorporates a dense tri-structural-isotropic/SiC fuel form and volumetrically efficient yttrium hydride moderator, both of which were manufactured and characterized under the TCR program. The TCR is a 3 MW{sub th} He-cooled experimental nuclear reactor designed to reach a total integrated burnup of less than 24 effective full-power hours to keep the radioactive source term to a very low level. TCR design process revealed a positive moderator coefficient; however, the negative doppler coefficients for the fuel and thermal expansion of fuel, moderator, and core support plate yield an overall negative reactivity coefficient. Calculated fuel element temperatures and stresses are well within safety margins. The maximum hypothetical accident (i.e., de-pressurized loss of forced cooling) yields only a modest increase in reactor temperatures that are all within safety margins. This paper summarizes the high-level TCR design characteristics, which were derived from neutronics, thermohydraulics, thermomechanics, and safety analyses.

21 SPECIFIC NUCLEAR REACTORS AND ASSOCIATED PLANTS↗
NASA NTRS1965

A low-temperature thermal noise source for use at the Goonhilly satellite-communication earth station

A matched waveguide termination was required as part of the noise temperature calibration facility in the receiving system at the Goonhilly earth-station. For routine measurement of overall system noise temperature, this termination is at ambient temperature. For other noise measurements, and in particular for the measurement of the effective input noise temperature of the maser, the waveguide termination is cooled to 77°K by immersion in liquid nitrogen.

TERMINAL↗
NASA NTRS2021

The simulation of the impact of the spatial distribution of vegetation on the urban microclimate: A case study in Mostaganem

Increasing vegetation is one of the solutions proposed to mitigate the phenomenon of urban heat islands. The present research aims to study the effect of the spatial distribution of vegetation on the urban microclimate during the summer period. The city of Mostaganem with its Mediterranean climate was chosen as a case study. Based on meteorological data collected on a hot day in July, the study is carried out using the ENVI-met 4.4.5. Scenarios of different vegetation layouts were carried out. Air, mean radiant and surface temperatures are the microclimatic parameters that have been analyzed for each of the scenarios, and in order to study the outdoor thermal comfort, the Predicted Mean Vote (PMV) is chosen as the comfort index, it compares the average value of the votes of a large group of people on the thermal sensation scale. The study revealed that tree alignments can have a cooling effect on the city temperature close to 1.2◦C. However, its impact on reducing the surface temperature can reach up to 4 ◦C. The introduction of vegetation on the site had the overall effect of lowering the air temperature and therefore relatively improving the level of comfort compared to the reference scenario. But, in order to reduce discomfort to an acceptable level during the day, vegetation can be simultaneously accommodated by city parameters such as urban form.

Nora Bachir↗
NASA NTRSDate not supplied

Select Variables Affecting Thermal System Design of a Liquid-Cooled Stator

NASA Glenn Researchers have endeavored to create a high-power-density, efficient electric motor called the High Efficiency Megawatt Motor (HEMM) with a goal of exceeding 98% efficiency and 1.46 MW of power. These aggressive goals were set because increasing the power density and efficiency of electric machines (motors and generators) is integral to bringing electrified aircraft (EA) to commercial realization. Resistive losses in the stator windings are by far the largest (34%) contributor to this design’s total energy losses. Previous testing of a HEMM-like stator test article (statorette) showed good agreement between measured performance and model predictions. Therefore, a foundation was provided to test other engineering parameters that are encountered when designing an electric machine. Of particular interest are the effects of changes to the thickness of the epoxy from the potting process, changes in the fluid volume/flow path around the end windings, and changes in the viscosity of the cooling fluid on the overall thermal performance of the unit. The impact of those parameters as revealed through a third-generation build, test, and finite element model analysis of a statorette test section is the focus of this paper.

EAP↗
DOE OSTI2020

Corrigendum and Addendum: Helium flux effects on bubble growth and surface morphology in plasma-facing tungsten from large-scale molecular dynamics simulations (2019 Nucl. Fusion 59 066035)

Two of the simulations discussed in a prior article (Hammond et al 2019 Nucl. Fusion 59 066035) were affected by a simulation glitch. We repeated the affected calculations and discuss them here. Here, the overall conclusions are essentially unchanged, though the details are different. In particular, observations that we referred to as ‘concerted bursting’ were caused primarily by non-physical heating and cooling applied by the thermostat after most atoms’ velocities were deleted (for reasons that are not known for certain). The phenomenon of one bubble bursting and causing another nearby bubble to burst does exist, though its effects are much less spectacular in the absence of non-physical driving forces. The observation of an interconnected network of sub-surface cavities formed by burst bubbles is real, and the observation of holes on the surface 1–2 nm in diameter is also confirmed.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗
NASA NTRS1991

ALS LOX/H2 subscale coaxial injector testing

Tests of a 40K subscale LOX/H2 coaxial LOX swirl injector conducted without injector or chamber degradation are reported. Chamber pressures ranged from 1572 to 2355 psia with overall mixture ratios from 5.04 to 6.39. The highest characteristic velocities were measured when the mixture ratio across the injector face was uniform. Scarfing of the outer row LOX posts had the largest effect on chamber heating rates. As a result of the tests, the LSI design was modified to arrange the outer row LOX posts in a circular pattern, eliminate O/F biasing and fuel film cooling, and modify the interpropellant plate to allow for larger pressure differentials during the start and cutoff transients. Testing of a 100 K LOX/H2 coaxial LOX swirl injector involved chamber pressure ranging from 700 to 2500 psia with overall mixture ratios from 3.2 to 8.8. Stable combustion was observed to a fuel temperature of 90R and characteristic velocity efficiencies were good.

Dexter, Carol E.↗
NASA NTRS2017

Microstructure Based Material-Sand Particulate Interactions and Assessment of Coatings for High Temperature Turbine Blades

Gas turbine engines for military/commercial fixed-wing and rotary wing aircraft use thermal barrier coatings in the high-temperature sections of the engine for improved efficiency and power. The desire to further make improvements in gas turbine engine efficiency and high power-density is driving the research and development of thermal barrier coatings and the effort of improving their tolerance to fine foreign particulates that may be contained in the intake air. Both commercial and military aircraft engines often are required to operate over sandy regions such as in the Middle-East nations, as well as over volcanic zones. For rotorcraft gas turbine engines, the sand ingestion is adverse during take-off, hovering near ground, and landing conditions. Although, most of the rotorcraft gas turbine engines are fitted with inlet particle separators, they are not 100 percent efficient in filtering fine sand particles of size 75 microns or below. The presence of these fine solid particles in the working fluid medium has an adverse effect on the durability of turbine blade thermal barrier coatings and overall performance of the engine. Typical turbine blade damages include blade coating wear, sand glazing, Calcia-Magnesia-Alumina-Silicate (CMAS) attack, oxidation, plugged cooling holes, all of which can cause rapid performance deterioration including loss of aircraft. The objective of this research is to understand the fine particle interactions with typical ceramic coatings of turbine blades at the microstructure level. A finite-element based microstructure modeling and analysis has been performed to investigate particle-surface interactions, and restitution characteristics. Experimentally, a set of tailored thermal barrier coatings and surface treatments were down-selected through hot burner rig tests and then applied to first stage nozzle vanes of the Gas Generator Turbine of a typical rotorcraft gas turbine engine. Laser Doppler velocity measurements were performed during hot burner rig testing to determine sand particle incoming velocities and their rebound characteristics upon impact on coated material targets. Further, engine sand ingestion tests were carried out to test the CMAS tolerance of the coated nozzle vanes. The findings from this on-going collaborative research to develop the next-gen sand tolerant coatings for turbine blades are presented in this paper.

Engine Tests↗
NASA NTRS1984

A two-dimensional analysis of laser heat addition in converging nozzles

The two-dimensional equations of motion describing the interaction between a laser beam and a flowing gas are considered. An implicit numerical scheme is used to solve these equations for unchoked flow through a converging-diverging nozzle. Separate grids are used for the fluid dynamics and the radiation equations. The effects of beam focusing and cross-beam intensity profiles are included. The calculations are based upon real gas properties for all quantities except the gas absorptivity, which is taken as a constant. The solutions contain the expected hot central core region with cool gas near the walls. This results in steep temperature gradients in both the streamwise and cross-stream directions. The absorption zone acts as a blockage in the nozzle causing a nonuniform velocity profile at the inlet and an overall decrease in mass flow. The absorption region also forces the streamlines to move away from the axis of symmetry, although this effect is not strong.

Molvik, G. A.↗
NASA NTRS1988

The structure of shocks with thermal conduction and radiative cooling

A general analysis is presented of the structure of a steady state, plane-parallel shock wave in which both thermal conduction and radiative cooling are important. The fluid is assumed to have a perfect-gas equation of state, with radiative cooling a function only of its temperature and density. Conduction in both diffusive and saturated regimes is treated. For the case of a strong shock, with conductivity and cooling function varying as power laws in temperature, approximate analytic solutions describing the shock wave are derived. For a plasma of solar composition, conduction is found to have a significant effect on the shock temperature and overall thickness of the postshock layer only for shock velocities greater than about 30,000 km/s, corresponding to shock temperatures greater than about 10 to the 10th K, but it affects the local structure of parts of the shock wave at much lower velocities. The effects of conduction are greatly enhanced if the heavy-element abundance is increased.

Lacey, Cedric G.↗
NASA NTRS1997

The Effects of Liquid Cooling Garments on Post-Space Flight Orthostatic Intolerance

Post space flight orthostatic intolerance among Space Shuttle crew members following exposure to extended periods of microgravity has been of significant concern to the safety of the shuttle program. Following the Challenger accident, flight crews were required to wear launch and entry suits (LES). It was noted that overall, there appeared to be a higher degree of orthostatic intolerance among the post-Challenger crews (approaching 30%). It was hypothesized that the increased heat load incurred when wearing the LES, contributed to an increased degree of orthostatic intolerance, possibly mediated through increased peripheral vasodilatation triggered by the heat load. The use of liquid cooling garments (LCG) beneath the launch and entry suits was gradually implemented among flight crews in an attempt to decrease heat load, increase crew comfort, and hopefully improve orthostatic tolerance during reentry and landing. The hypothesis that the use of the LCG during reentry and landing would decrease the degree of orthostasis has not been previously tested. Operational stand-tests were performed pre and post flight to assess crewmember's cardiovascular system's ability to respond to gravitational stress. Stand test and debrief information were collected and databased for 27 space shuttle missions. 63 crewpersons wearing the LCG, and 70 crewpersons not wearing the LCG were entered into the database for analysis. Of 17 crewmembers who exhibited pre-syncopal symptoms at the R+O analysis, 15 were not wearing the LCG. This corresponds to a 21% rate of postflight orthostatic intolerance among those without the LCG, and a 3% rate for those wearing LCG. There were differences in these individual's average post-flight maximal systolic blood pressure, and lower minimal Systolic Blood pressures in those without LCG. Though other factors, such as type of fluid loading, and exercise have improved concurrently with LCG introduction, from this data analysis, it appears that LCG usage provided a significant degree of protection from post-flight orthostatic intolerance.

Billica, Roger↗
NASA NTRS2006

The Boiling eXperiment Facility (BXF) for the Microgravity Science Glovebox (MSG)

Boiling is an effective means of cooling by removing heat from surfaces through vaporization of a working fluid. It is also affected by both the magnitude and direction of gravity. By conducting pool boiling tests in microgravity, the effect of buoyancy n the overall boiling process and the relative magnitude of other phenomena can be assessed. The Boiling eXperiment Facility (BXF) is being built for the Microgravity Science Glovebox. This facility will conduct two pool boiling studies. The first study the Microheater Array Boiling Experiment (MABE) uses two 96 element microheater arrays, 2.7 mm and 7.0 mm in size, to measure localized hear fluxes while operating at a constant temperature. The other experiment, the Nucleate Pool Boiling eXperiment (NPBX) uses a 85 mm diameter heater wafer that has been "seeded" with five individually-controlled nucleation sites to study bubble nucleation, growth, coalescence and departure. The BXF uses normal-perfluorohexane as the test fluid and will operate between pressures of 60 to 244 Pa. and temperatures of 35 to 60 C. Both sets of experimental heaters are highly instrumented. Pressure and bulk fluid temperature measurements will be made with standard rate video. A high speed video system will be used to visualize the boiling process through the bottom of the MABE heater arrays. The BXF is currently scheduled to fly on Utilization Flight-13A.1 to the ISS with facility integration into the MSG and operation during Increment 15

McQuillen, John↗
DOE OSTI2021

Effect of thermal aging and irradiation on microstructure and crack growth response of Alloy 690

Nickel-base Alloy 690 and the associated weld Alloys 52 and 152 are typically used for nozzle penetrations in replacement heads for pressurized water reactor (PWR) vessels, because of their excellent overall resistance to general corrosion and environmental degradation, primarily stress corrosion cracking (SCC). However, many of the existing PWRs reactors are expected to operate for 40-80 years. Likewise, advanced water-cooled small modular reactors (SMRs) will use Ni-Cr alloys and are expected to receive initial operating licenses for 60 years. Hence, the thermal stability of Ni-Cr alloys is a potential concern for the long-term performance of both existing and advanced nuclear plants, and possibly spent fuel storage containers. The objective of this research is to understand the microstructural changes occurring in high-Cr, Ni-based Alloy 690 during long time exposure to the reactor operating temperatures, and the effect of these changes on the service performance. One area of particular concern is the potential for long range ordering (LRO), i.e. formation of the intermetallic Ni 2 Cr phase under prolonged exposure to reactor temperatures and/or irradiation, which can increase strength, decrease ductility, and cause dimensional changes or lead to in-service embrittlement of components made with these alloys. Hence, this research focused on the microstructural evolution and the SCC response of Alloy 690 under accelerated thermal aging and irradiation conditions. The materials studied involved Alloy 690 from two sources: (i) Alloy 690 plate from an Alloy 152 dissimilar metal weld (DMW) joining the Alloy 690 plate to Alloy 533 LAS, aged at three different temperatures (370°C, 400°C and 450°C) for up to 75,000h (equivalent to 60 years of service), and (ii) specimens neutron-irradiated in the BOR-60 reactor up to 40 dpa. For aged Alloy 690 specimens, hardness was found to increase with aging time, however, the microstructural characterization by means of synchrotron X-ray did not find evidence of LRO. The microstructural characterization of neutron-irradiated specimens by TEM found no evidence of LRO either. Testing in a primary water environment of Alloy 690 specimens aged to a 60-year service equivalent revealed a fatigue and corrosion fatigue crack growth responses similar to those measured on the un-aged alloy. The SCC CGR response was also low. Overall, the two Alloy 690 heats investigated in this work, aged up to 60-year service equivalents or exposed to neutron irradiation up to 40 dpa, did not exhibit a deterioration in microstructure or performance.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗