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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 19 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Shaping High Efficiency, High Temperature Cavity Tubular Solar Central Receivers

High temperature solar receivers are developed in the context of the Gen3 solar thermal power plants, in order to power high efficiency heat-to-electricity cycles. Since particle technology collects and stores high temperature solar heat, CNRS (French National Center for Scientific Research) develops an original technology using fluidized particles as HTF (heat transfer fluid). The targeted particle temperature is around 750 °C, and the walls of the receiver tubes, reach high working temperatures, which impose the design of a cavity receiver to limit the radiative losses. Therefore, the objective of this work is to explore the cavity shape effect on the absorber performances. Geometrical parameters are defined to parametrize the design. The size and shape of the cavity, the aperture-to-absorber distance and its tilt angle. A thermal model of a 50 MW hemi-cylindrical tubular receiver, closed by refractory panels, is developed, which accounts for radiation and convection losses. Parameter ranges that reach a thermal efficiency of at least 85% are explored. This sensitivity analysis allows the definition of cavity shape and dimensions to reach the targeted efficiency. For an aperture-to-absorber distance of 9 m, the 85% efficiency is obtained for aperture areas equal or less than 20 m2 and 25 m2 for high, and low convection losses, respectively.

Gueguen, Ronny (ORCID:0000000252368638)↗
NASA NTRS2021

NASA High Efficiency, High OPR Capable Small Core Compressor

As future aircraft become lighter and more aerodynamically efficient, thrust requirements will decrease, reducing the core size of the engine. Furthermore, in the pursuit of improved fuel burn, engine overall pressure ratio and bypass ratio will increase, further driving down engine core size (core size being defined as high-pressure compressor [HPC] exit-corrected flow). These drivers together mean that the core size for future single-aisle aircraft applications will shrink below 3.0 lb/s. Traditionally, this small core compressor size is in the domain of axi-centrifugal designs, machines that are typically less efficient and limited to pressure ratios of ~25 due to stress and thermomechanical fatigue in the centrifugal impeller. In this light, NASA and Pratt & Whtiney (P&W) embarked upon a program to develop technologies to enable an all-axial high-pressure compressor with a core size below 3.0 lb/s and an overall pressure ratio greater than 50. The challenge with an all-axial high-pressure compressor at this core size is the small span at the rear of the compressor. As core size is scaled down, the rotor tip clearances, stator hub seal clearances, fillet sizes and leading edge thicknesses do not scale, leading to significant efficiency penalties. The goal of this program is to recover this lapse and realize the cycle benefits of small core size and high overall pressure ratio. The small core challenges described are mitigated through design optimization and technology insertion, enabling an estimated 5 to 10% fuel burn reduction relative to 2020 best-in-class. Three test rigs run at NASA Glenn Research Center evolved the small core design: a low-speed rig to vet technology and validate tools, and two high speeds rigs, the first to demonstrate an optimized meanline design and the second to validate technology to manage large rotor tip gaps. The efficiency improvement validated with these rigs has unlocked the small core design space, demonstrating that small core compressors can maintain a similar efficiency to current best-in-class large core size compressors. In addition to advancing the state-of-the-art of technology, the program has also advanced the modeling standards for multistage compressors with large clearance-to-span ratios. A best practice modeling standard was developed over the course of the program, incorporating learning from all three rig programs.

Axial Compressors↗
NASA NTRS1979

High Efficiency, High Density Terrestrial Panel

Terrestrial panels were fabricated using rectangular cells. Packing densities in excess of 90% with panel conversion efficiencies greater than 13% were obtained. Higher density panels can be produced on a cost competitive basis with the standard salami panels.

Wohlgemuth, J.↗
DOE OSTI2021

Amorphous and Nanocomposite Magnets for High Efficiency, High Speed Motor Designs

This project developed metal amorphous nanocomposite (MANC) soft magnetic materials (SMMs) for a rare earth (RE)-free 2.5 kW motor with 4% increased efficiency. The Project modeled RE-free motor topologies. The project outcomes addressed: (a) metal to alloy processing & magnet core production; (b) soft magnetic laminate & core post-processing; and (c) producing a 2.5 kW motor extending to TRL-5.

30 DIRECT ENERGY CONVERSION↗
NASA NTRS1980

Design requirements for high-efficiency high concentration ratio space solar cells

A miniaturized Cassegrainian concentrator system concept was developed for low cost, multikilowatt space solar arrays. The system imposes some requirements on solar cells which are new and different from those imposed for conventional applications. The solar cells require a circular active area of approximately 4 mm in diameter. High reliability contacts are required on both front and back surfaces. The back area must be metallurgically bonded to a heat sink. The cell should be designed to achieve the highest practical efficiency at 100 AMO suns and at 80 C. The cell design must minimize losses due to nonuniform illumination intensity and nonnormal light incidence. The primary radiation concern is the omnidirectional proton environment.

Rauschenbach, H.↗
NASA NTRS1968

High efficiency, high frequency magnetic deflection driver

Electromagnetic deflection yoke stores energy during the scan and releases it in the flyback or retrace. The operation of the device involves a method of switching to a voltage high enough to dissipate the flyback pulse during the retrace time and then operating during the scan time at a much lower voltage.

Schaff, F. L.↗
NASA NTRS1975

Studies of discharge mechanisms in high pressure gases-applications to high efficiency high power lasers

By measuring the absorption and emission cantinua of various states in the cesium/xenon molecule, the collisional rates critical in populating the alkali/rare gas excimer levels have been estimated. Cs atomic states that are weakly optically connected to ground have been shown to form excimer levels that are attractive as potential dissociation lasers. In particular, the (Cs/7 2S/Xe) excited molecule appears promising as a source of high energy laser radiation due to its large dissociation energy, stimulated emission cross section, and small population inversion densities. Monitoring of the optically pumped Cs2 molecular absorption profile in the presence of xenon shows a drastic change with increasing xenon pressure for the Cs2C band. Dominant absorption at large xenon densities is centered around approximately 6380 A as opposed to 6300 A for lower perturber pressure.

Cherrington, B. E.↗
NASA NTRS1979

Studies of basic mechanisms occurring in high pressure gases: Applications to high efficiency high power lasers

The atomic fluorine laser was investigated. In the hollow cathode, lasing on Fluorine transitions in the doublet system lasted for up to 80 microns with no signs of self-termination. The excitation process of the laser appears to depend heavily upon the fluorine donor utilized. For instance, a single step process is involved when NF3 is used whereas a two step process is evident for SF6. The details are discussed.

Crane, J. K., III↗
DOE OSTI2026

High-Efficiency, High-Current Laser-Driven Electron Injector

This final report describes research conducted under DOE Award DE-SC0021132, "High-Efficiency, High-Current Laser-Driven Electron Injector," during the period 09/01/2020–08/31/2023. The project investigates a largely unexplored regime of short-pulse laser–plasma interaction near the quarter-critical density in ultrathin gas targets as a novel electron injection mechanism for laser–wakefield acceleration (LWFA). The overarching goal is to develop high-efficiency, high-current electron sources driven by modest peak-intensity lasers at high repetition rate, suitable as compact injectors or front-ends for future laser-based accelerators.

43 PARTICLE ACCELERATORS↗
NASA NTRS1984

High efficiency IMPATT diodes for 60 GHz intersatellite link applications

Intersatellite links are expected to play an increasingly important role in future satellite systems. Improved components are required to properly utilize the wide bandwidth allocated for intersatellite link applications around 60 GHz. IMPATT diodes offer the highest potential performance as solid state power sources for a 60 GHz transmitter. Presently available devices do not have the desired power and efficiency. High efficiency, high power IMPATT diodes for intersatellite link applications are being developed by NASA and other government agencies. The development of high efficiency 60 GHz IMPATT diodes by NASA is described.

Haugland, E. J.↗
NASA NTRS1984

High efficiency IMPATT diodes for 60 GHz intersatellite link applications

Intersatellite links are expected to play an increasingly important role in future satellite systems. Improved components are required to properly utilize the wide bandwidth allocated for intersatellite link applications around 60 GHz. IMPATT diodes offer the highest potential performance as solid state power sources for a 60 GHz transmitter. Presently available devices do not have the desired power and efficiency. High efficiency, high power IMPATT diodes for intersatellite link applications are being developed by NASA and other government agencies. This paper describes the development of high efficiency 60 GHz IMPATT diodes by NASA. These programs are cofunded by the U.S. Air Force, Space Division.

Haugland, E. J.↗
NASA NTRS2004

Development and Characterization of High-Efficiency, High-Specific Impulse Xenon Hall Thrusters

This dissertation presents research aimed at extending the efficient operation of 1600 s specific impulse Hall thruster technology to the 2000 to 3000 s range. Motivated by previous industry efforts and mission studies, the aim of this research was to develop and characterize xenon Hall thrusters capable of both high-specific impulse and high-efficiency operation. During the development phase, the laboratory-model NASA 173M Hall thrusters were designed and their performance and plasma characteristics were evaluated. Experiments with the NASA-173M version 1 (v1) validated the plasma lens magnetic field design. Experiments with the NASA 173M version 2 (v2) showed there was a minimum current density and optimum magnetic field topography at which efficiency monotonically increased with voltage. Comparison of the thrusters showed that efficiency can be optimized for specific impulse by varying the plasma lens. During the characterization phase, additional plasma properties of the NASA 173Mv2 were measured and a performance model was derived. Results from the model and experimental data showed how efficient operation at high-specific impulse was enabled through regulation of the electron current with the magnetic field. The electron Hall parameter was approximately constant with voltage, which confirmed efficient operation can be realized only over a limited range of Hall parameters.

Hofer, Richard R.↗
DOE OSTI2021

High-efficiency High-energy Photon Radiography Panels [Slides]

Demonstrate a developmental path towards production of efficient radiography panel for high energy radiography while keeping the production cost reasonable. Fulfill some needs identified in the research thrust GOR 2/K/b "Diagnostics systems".

62 RADIOLOGY AND NUCLEAR MEDICINE↗