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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 55 records · Page 3
All sourcesNASA NTRSDOE OSTI
DOE OSTI2021

Understanding HPC Benchmark Performance on Intel Broadwell and Cascade Lake Processors

Hardware platforms in high performance computing are constantly getting more complex to handle even when considering multicore CPUs alone. Numerous features and configuration options in the hardware and the software environment that are relevant for performance are not even known to most application users or developers. Microbenchmarks, i.e., simple codes that fathom a particular aspect of the hardware, can help to shed light on such issues, but only if they are well understood and if the results can be reconciled with known facts or performance models. The insight gained from microbenchmarks may then be applied to real applications for performance analysis or optimization. In this paper we investigate two modern Intel x86 server CPU architectures in depth: Broadwell EP and Cascade Lake SP. We highlight relevant hardware configuration settings that can have a decisive impact on code performance and show how to properly measure on-chip and off-chip data transfer bandwidths. The new victim L3 cache of Cascade Lake and its advanced replacement policy receive due attention. Finally we use DGEMM, sparse matrix-vector multiplication, and the HPCG benchmark to make a connection to relevant application scenarios.

97 MATHEMATICS AND COMPUTING↗
NASA NTRS1974

Performance of a model cascade thrust reverser for short-haul applications

Aerodynamic and acoustic characteristics are presented for a cowlmounted, model cascade thrust reverser suitable for short-haul aircraft. Thrust reverser efficiency and the influence on fan performance were determined from isolated fan-driven models under static and forward velocity conditions. Cascade reverser noise characteristics were determined statically in an isolated pipe-flow test, while aerodynamic installation effects were determined with a wind-tunnel, fan-powered airplane model. Application of test results to short-haul aircraft calculations demonstrated that such a cascade thrust reverser may be able to meet both the performance and noise requirements for short-haul aircraft operation. However, aircraft installation effects can be quite significant.

Dietrich, D. A.↗
NASA NTRS1974

Performance of a model cascade thrust reverser for short-haul applications

Aerodynamic and acoustic characteristics are presented for a cowl-mounted, model cascade thrust reverser suitable for short-haul aircraft. Thrust reverser efficiency and the influence on fan performance were determined from isolated fan-driven models under static and forward velocity conditions. Cascade reverser noise characteristics were determined statically in an isolated pipe-flow test, while aerodynamic installation effects were determined with a wind-tunnel, fan-powered airplane model. Application of test results to short-haul aircraft calculations demonstrate that such a cascade thrust reverser may be able to meet both the performance and noise requirements for short-haul aircraft operation. However, aircraft installation effects can be quite significant.

Dietrich, D. A.↗
NASA NTRS1974

Cold-air annular-cascade investigation of aerodynamic performance of cooled turbine vanes. 1: Facility description and base (solid) vane performance

The aerodynamic performance of a solid vane was experimentally determined in a full-annular cascade, where three-dimensional effects could be obtained. This vane was of the same size and profile as the cooled vanes to be subsequently tested. The vanes were tested over a pressure ratio range that corresponded to mean-radius ideal aftermixed critical velocity ratios of 0.71 to 0.89. Overall vane aftermixed efficiencies were obtained over this range of critical velocity ratios and compared with results from a four-vane annular-sector cascade. The variation in vane aftermixed conditions and vane aftermixed efficiency with radius were also obtained and compared with design values. Vane surface static-pressure distributions were measured and compared with theory and with the results obtained in the four-vane cascade.

Goldman, L. J.↗
NASA NTRS1975

Cold-air annular-cascade investigation of aerodynamic performance of cooled turbine vanes. 2: Trailing-edge ejection, film cooling, and transpiration cooling

The aerodynamic performance of four different cooled vane configurations was experimentally determined in a full-annular cascade at a primary- to coolant-total-temperature ratio of 1.0. The vanes were tested over a range of coolant flow rates and pressure ratios. Overall vane efficiencies were obtained and compared, where possible, with the results obtained in a four-vane, annular-sector cascade. The vane efficiency and exit flow conditions as functions of radial position were also determined and compared with solid (uncooled) vane results.

Goldman, L. J.↗
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 NTRS1976

Cold-air annular-cascade investigation of aerodynamic performance of core-engine-cooled turbine vanes. 2: Pressure surface trailing edge ejection and split trailing edge ejection

The aerodynamic performance of two trailing edge ejection cooling configurations of a core-engine stator vane were experimentally determined in an ambient inlet-air full-annular cascade where three-dimensional effects could be obtained. The tests were conducted at the design mean-radius ideal aftermixed critical velocity ratio of 0.778. Overall vane aftermixed thermodynamic and primary efficiencies were obtained over a range of coolant flows to about 10 percent of the primary flow at a primary to coolant total temperature ratio of 1.0. The radial variation in efficiency and the circumferential and radial variations in vane-exit total pressure were determined. Comparisons are made with the solid (uncooled) vane.

Mclallin, K. L.↗
NASA NTRS1975

Aerodynamic performance of a fully film cooled core turbine vane tested with cold air in a two-dimensional cascade

The aerodynamic performance of a fully film cooled core turbine vane was investigated experimentally in a two-dimensional cascade of 10 vanes. Three of the 10 vanes were cooled; the others were solid (uncooled) vanes. Cold air was used for both the primary and coolant flows. The cascade test covered a range of pressure ratios corresponding to ideal exit critical velocity ratios of 0.6 to 0.95 and a range of coolant flow rates to 7.5 percent of the primary flow. The coolant flow was varied by changing the coolant supply pressure. The principal measurements were cross-channel surveys of exit total pressure, static pressure, and flow angle. The results presented include exit survey data and overall performance in terms of loss, flow angle, and weight flow for the range of exit velocity ratios and coolant flows investigated. The performance of the cooled vane is compared with the performance of an uncooled vane of the same profile and also with the performance obtained with a single cooled vane in the 10-vane cascade.

Stabe, R. G.↗
NASA NTRS1975

Aerodynamic performance of a ceramic-coated core turbine vane tested with cold air in a two-dimensional cascade

The aerodynamic performance of a core turbine vane with a ceramic coating was investigated experimentally in a two-dimensional cascade of 10 vanes. The vane was first tested with a rough coating and then retested after the coating had been smoothed. The test fluid was atmospheric air. The cascade tests covered a range of pressure ratios corresponding to ideal exit critical velocity ratios of 0.6 to 0.95. The principal measurements were cross-channel surveys of exit total pressure, static pressure, and flow angle. The results presented include exit survey results and overall performance in terms of flow angle, weight flow, and kinetic energy loss. The performance of the ceramic-coated vanes is compared with the performance of an uncoated vane having a similar profile.

Stabe, R. G.↗
NASA NTRS1986

Performance analysis of a cascaded coding scheme with interleaved outer code

A cascaded coding scheme for a random error channel with a bit-error rate is analyzed. In this scheme, the inner code C sub 1 is an (n sub 1, m sub 1l) binary linear block code which is designed for simultaneous error correction and detection. The outer code C sub 2 is a linear block code with symbols from the Galois field GF (2 sup l) which is designed for correcting both symbol errors and erasures, and is interleaved with a degree m sub 1. A procedure for computing the probability of a correct decoding is presented and an upper bound on the probability of a decoding error is derived. The bound provides much better results than the previous bound for a cascaded coding scheme with an interleaved outer code. Example schemes with inner codes ranging from high rates to very low rates are evaluated. Several schemes provide extremely high reliability even for very high bit-error rates say 10 to the -1 to 10 to the -2 power.

Lin, S.↗
NASA NTRS1983

Aerodynamic performance of an annular classical airfoil cascade

Results are presented for a series of experiments that were performed in a large-scale subsonic annular cascade facility that was specifically designed to provide three-dimensional aerodynamic data for the verification of numerical-calculation codes. In particular, the detailed three-dimensional aerodynamic performance of a classical flat-plate airfoil cascade is determined for angles of incidence of 0, 5, and 10 deg. The resulting data are analyzed and are correlated with predictions obtained from NASA's MERIDL and TSONIC numerical programs. It is found that: (1) at 0 and 5 deg, the airfoil surface data show a good correlation with the predictions; (2) at 10 deg, the data are in fair agreement with the numerical predictions; and (3) the two-dimensional Gaussian similarity relationship is appropriate for the wake velocity profiles in the mid-span region of the airfoil.

Bergsten, D. E.↗
NASA NTRS1957

Comparison of NACA 65-series compressor-blade pressure distributions and performance in a rotor and in cascade

An investigation has been conducted to compare the performance of NACA 65-series compressor blades in two-dimensional cascade with that in an axial flow compressor. Blade pressure distributions were obtained by the use of a mercury-seal pressure-transfer device. The comparison indicated that cascade data accurately predicted the turning angle and blade pressure distribution obtained in the compressor at design conditions.

CASCADES↗
DOE OSTI2023

Pushing the performance limits of long wavelength interband cascade lasers using innovative quantum well active regions

Here, we report significantly enhanced device performance in long wavelength interband cascade lasers (ICLs) by employing a recently proposed innovative quantum well (QW) active region containing strained InAsP layers. These ICLs were able to operate at wavelengths near 14.4 μm, the longest ever demonstrated for III–V interband lasers, implying great potential of ICLs to cover an even wider wavelength range. Also, by applying the aforesaid QW active region configuration on ICLs at relatively short wavelengths, ICLs were demonstrated at a low threshold current density (e.g., 13 A/cm 2 at 80 K) and at temperatures up to 212 K near 12.4 μm, more than 50 K higher than the previously reported ICLs with the standard W-shape QW active region at similar wavelengths. This suggests that the QW active region with InAsP layers can be used to improve device performance at the shorter wavelengths.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
NASA NTRS1988

Experimental investigation of the performance of a supersonic compressor cascade

Supersonic cascade wind tunnel results are presented for a linear, supersonic compressor cascade derived from the near-tip section of a high-throughflow axial flow compressor rotor over the inlet Mach number range of 1.30-1.71. Laser anemometry was used to obtain flow-velocity measurements showing the wave pattern in the entrance region. Attention is given to the unique-incidence relationship for this cascade, which relates the supersonic inlet Mach number to the inlet flow direction. An empirical correlation is obtained for the influence of the independent parameters of back pressure, axial velocity density ratio, and blade element performance.

Tweedt, T. L.↗
DOE OSTI2021

Design of a bifunctional TEMPO-tertiary amine mesoporous silica catalyst for the three-step cascade synthesis of a chromene derivative

A key challenge is design of materials and processes whereby competing reagents or conditions do not harm the multi-step sequence, thus allowing for more efficient chemical synthesis with elimination of work-up and separation steps. In this work, a three-step reaction cascade is performed using a porous bifunctional dimethylpropylamine-TEMPO-MCM41 catalyst, converting the commodity chemicals benzyl alcohol, sodium hypochlorite, and malononitrile to a biologically active anti-cancer, and anti-malarial 2-amino-chromene derivative. The cascade first utilizes a TEMPO-catalyzed oxidation of benzyl alcohol to benzaldehyde with NaOCl as the terminal oxidant. This is followed by a two-step, dual base catalyzed Knoevenagel condensation with malononitrile followed by a Michael addition with lawsone. Optimal conditions converting benzyl alcohol to 2-amino-5,10-dioxo-4-phenyl-5,10-dihydro-4H-benzo[g]chromene-3-carbonitrile include the delayed addition of malononitrile and lawsone during the three-step reaction sequence, which results in a 2-amino-chromene yield of over 80%. The importance of stepwise reagent addition is rationalized due to the unfavorable adsorption of acidic lawsone on the surface-grafted base catalyst. Tertiary Brønsted base sites of dimethylpropylamine outperform the more Lewis basic primary propylamine functionalized catalyst. This work outlines a simple and effective method for generating mesoporous materials with two types of active sites via co-condensation and thiol-ene coupling procedures.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗