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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 1,369 records · Page 76

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NASA NTRS1976

Evaluation of the flat-plate solar collector system for electric power generation

This evaluation of the flat-plate collector system was designed to determine the number of flat-plate collectors required to generate a given amount of electricity with optimum efficiency. Variable parameters are the temperature of the heat-transport fluid, both to and from the collector field. In the analysis, the efficiency of the flat-plate collectors was coupled to the efficiency of the thermal cycle to calculate optimal overall system efficiencies. Overall system efficiencies for the system are on the order of 3.5 per cent or less. Over two million 4 ft-by-4 ft collectors would be required to produce 100,000 kW(e). Based on the results, it can be shown that the limiting factor in the use of the flat-plate collector system for electric power generation is the efficiency of the collectors. An increase in the overall system efficiency can occur only if the collector efficiency can be increased at higher surface temperatures.

Athey, R. E.↗

NASA NTRS1977

Aerodynamic characteristics of supersonic fighter airplane configurations based on Soviet design concepts

The aerodynamic, stability, and control characteristics of several supersonic fighter airplane concepts are examined. The configurations, which are based on Soviet design concepts, include fixed-wing aircraft having delta wings, swept wings, and trapezoidal wings, and a variable wing-sweep aircraft. Each concept employs aft tail controls. The concepts vary from lightweight, single-engine, air superiority, point interceptor, or ground attack types to larger twin-engine interceptor and reconnaissance designs. Analytical and experimental results indicate that careful application of the transonic or supersonic area rule can provide nearly optimum shaping for minimum drag for a specified Mach number requirement. In addition, through the proper location of components and the exploitation of interference flow fields, the concepts provide linear pitching moment characteristics, high control effectiveness, and reasonably small variations in aerodynamic center location with a resulting high potential for maneuvering capability.

Spearman, M. L.↗

NASA NTRS1985

High-efficiency cell concepts on low-cost silicon sheets

The limitations on sheet growth material in terms of the defect structure and minority carrier lifetime are discussed. The effect of various defects on performance are estimated. Given these limitations designs for a sheet growth cell that will make the best of the material characteristics are proposed. Achievement of optimum synergy between base material quality and device processing variables is proposed. A strong coupling exists between material quality and the variables during crystal growth, and device processing variables. Two objectives are outlined: (1) optimization of the coupling for maximum performance at minimal cost; and (2) decoupling of materials from processing by improvement in base material quality to make it less sensitive to processing variables.

Bell, R. O.↗

NASA NTRS1985

Waveguide PIN junction electrooptic phase modulators Theoretical analysis and design criteria

Basic design equations for waveguide PIN heterojunction electrooptic phase modulators utilizing the linear electrooptic effect are derived, and criteria for optimum operation (in terms of obtainable phase shifts) are discussed. Although the numerical examples pertain to devices fabricated of the AlGaAs system on (100) substrates, the same method can be directly applied to modulators fabricated of other materials.

Marshall, W. K.↗

NASA NTRS1989

Adaptive clutter rejection filters for airborne Doppler weather radar applied to the detection of low altitude windshear

An optimum adaptive clutter rejection filter for use with airborne Doppler weather radar is presented. The radar system is being designed to operate at low-altitudes for the detection of windshear in an airport terminal area where ground clutter returns may mask the weather return. The coefficients of the adaptive clutter rejection filter are obtained using a complex form of a square root normalized recursive least squares lattice estimation algorithm which models the clutter return data as an autoregressive process. The normalized lattice structure implementation of the adaptive modeling process for determining the filter coefficients assures that the resulting coefficients will yield a stable filter and offers possible fixed point implementation. A 10th order FIR clutter rejection filter indexed by geographical location is designed through autoregressive modeling of simulated clutter data. Filtered data, containing simulated dry microburst and clutter return, are analyzed using pulse-pair estimation techniques. To measure the ability of the clutter rejection filters to remove the clutter, results are compared to pulse-pair estimates of windspeed within a simulated dry microburst without clutter. In the filter evaluation process, post-filtered pulse-pair width estimates and power levels are also used to measure the effectiveness of the filters. The results support the use of an adaptive clutter rejection filter for reducing the clutter induced bias in pulse-pair estimates of windspeed.

Keel, Byron M.↗

NASA NTRS1991

Lunar electric power systems utilizing the SP-100 reactor coupled to dynamic conversion systems

An integration study was performed by coupling an SP-100 reactor to either a Brayton or Stirling power conversion subsystem. The application was for a surface power system to supply power requirements to a lunar base. A power level of 550 kWe was selected based on the NASA Space Exploration Initiative 90-day study. Reliability studies were initially performed to determine optimum power-conversion redundancy. This study resulted in selecting three operating engines and one standby unit. Integratiaon-design studies indicated that either the Brayton or Stirling power conversion subsystem could be integrated with the SP-100 reactor. The Stirling system had an integration advantage because of smaller piping size and fewer components. The Stirling engine, however, is more complex and heavier than the Brayton rotating unit, which tends to offset the Stirling integration advantage. From a performance consideration, the Brayton had a 9-percent mass advantage and the Stirling a 50-percent radiator-area advantage.

Harty, Richard B.↗

NASA NTRS1993

Lunar electric power systems utilizing the SP-100 reactor coupled to dynamic conversion systems

An integration study was performed by Rocketdyne under contract to NASA-LeRC. The study was concerned with coupling an SP-0100 reactor to either a Brayton or Stirling power conversion system. The application was for a surface power system to supply power requirements to a lunar base. A power level of 550 kWe was selected based on the NASA Space Exploration Initiative 90-day study. Reliability studies were initially performed to determine optimum power conversion redundancy. This study resulted in selecting three operating engines and one stand-by unit. Integration design studies indicated that either the Brayton or Stirling power conversion systems could be integrated with the PS-100 reactor. The Stirling system had an integration advantage because of smaller piping size and fewer components. The Stirling engine, however, is more complex and heavier than the Brayton rotating unit, which tends to off-set the Stirling integration advantage. From a performance consideration, the Brayton had a 9 percent mass advantage, and the Stirling had a 50 percent radiator advantage.

Harty, Richard B.↗

NASA NTRS1999

Design of a Low Speed Fan Stage for Noise Suppression

This report describes the design of a low tip speed, moderate pressure rise fan stage for demonstration of noise reduction concepts. The fan rotor is a fixed-pitch configuration delivering a design pressure ratio of 1.378 at a specific flow of 43.1 lbm/sec/sq ft. Four exit stator configurations were provided to demonstrate the effectiveness of circumferential and axial sweep in reducing rotor-stator interaction tone noise. The fan stage design was combined with an axisymmetric inlet, conical convergent nozzle, and nacelle to form a powered fan-nacelle subscale model. This model has a 22-inch cylindrical flow path and employs a rotor with a 0.30 hub-to-tip radius ratio. The design is fully compatible with an existing NASA force balance and rig drive system. The stage aerodynamic and structural design is described in detail. Three-dimensional (3-D) computational fluid dynamics (CFD) tools were used to define optimum airfoil sections for both the rotor and stators. A fan noise predictive system developed by Pratt & Whitney under contract to NASA was used to determine the acoustic characteristics of the various stator configurations. Parameters varied included rotor-to-stator spacing and vane leading edge sweep. The structural analysis of the rotor and stator are described herein. An integral blade and disk configuration was selected for the rotor. Analysis confirmed adequate low cycle fatigue life, vibratory endurance strength, and aeroelastic suitability. A unique load carrying stator arrangement was selected to minimize generation of tonal noise due to sources other than rotor-stator interaction. Analysis of all static structural components demonstrated adequate strength, fatigue life, and vibratory characteristics.

Dalton, W. N.↗

NASA NTRS2007

Spherical Cryogenic Hydrogen Tank Preliminary Design Trade Studies

A structural analysis, sizing optimization, and weight prediction study was performed by Collier Research Corporation and NASA Glenn on a spherical cryogenic hydrogen tank. The tank consisted of an inner and outer wall separated by a vacuum for thermal insulation purposes. HyperSizer (Collier Research and Development Corporation), a commercial automated structural analysis and sizing software package was used to design the lightest feasible tank for a given overall size and thermomechanical loading environment. Weight trade studies were completed for different panel concepts and metallic and composite material systems. Extensive failure analyses were performed for each combination of dimensional variables, materials, and layups to establish the structural integrity of tank designs. Detailed stress and strain fields were computed from operational temperature changes and pressure loads. The inner tank wall is sized by the resulting biaxial tensile stresses which cause it to be strength driven, and leads to an optimum panel concept that need not be stiffened. Conversely, the outer tank wall is sized by a biaxial compressive stress field, induced by the pressure differential between atmospheric pressure and the vacuum between the tanks, thereby causing the design to be stability driven and thus stiffened to prevent buckling. Induced thermal stresses become a major sizing driver when a composite or hybrid composite/metallic material systems are used for the inner tank wall for purposes such as liners to contain the fuel and reduce hydrogen permeation.

Arnold, Steven M.↗

NASA NTRS2008

Parametric Study of High Frequency Pulse Detonation Tubes

This paper describes development of high frequency pulse detonation tubes similar to a small pulse detonation engine (PDE). A high-speed valve injects a charge of a mixture of fuel and air at rates of up to 1000 Hz into a constant area tube closed at one end. The reactants detonate in the tube and the products exit as a pulsed jet. High frequency pressure transducers are used to monitor the pressure fluctuations in the device and thrust is measured with a balance. The effects of injection frequency, fuel and air flow rates, tube length, and injection location are considered. Both H2 and C2H4 fuels are considered. Optimum (maximum specific thrust) fuel-air compositions and resonant frequencies are identified. Results are compared to PDE calculations. Design rules are postulated and applications to aerodynamic flow control and propulsion are discussed.

Cutler, Anderw D.↗

NASA NTRSDate not supplied

Optimization of a Parametric Lobe Mixer for Internally Mixed Nozzles

The results of the first phase of an optimization study on a parametric procedurally-generated lobe mixer are presented. This mixer is part of a dual-stream plug nozzle system, designed under NASA’s CST project for use in near-term commercial supersonic applications. Data was obtained numerically using NASA’s in-house CFD code FUN3D and analyzed to determine mixer performance. Phase I of the study examined five independently-variable geometric parameters describing the lobe mixer. Methods of Design of Experiments (DoE) were used to obtain a parametric model to quickly evaluate mixer performance and determine an optimum configuration. Mixers that induced strong axial vorticity and shear layers without causing flow separation were found to perform best, with exit temperature variance highly inversely correlated to mixing effectiveness.

Lobe Mixer↗

NASA NTRSDate not supplied

Optimization of a Parametric Lobe Mixer for Internally Mixed Nozzles

Lobe mixer↗

DOE OSTI2023

Design, Optimization, and Validation of GaN-Based DAB Converter for Active Cell Balancing in BTMS Applications: Preprint

This paper focuses on the design of a bidirectional dual active bridge (DAB) DC/DC converter that utilizes Gallium Nitride (GaN) switches as active components. In the existing literature, MOSFET-based DAB for active cell balancing is available, but GaN-based DAB converter for active cell balancing is still new. The proposed modular isolated GaN-based DAB converter is designed as an individual module of active cell balancing for behind-the-meter storage (BTMS) applications, targeting high-power charging stations. Modular isolated converters are connected to each cell (low voltage bus), and each cell is connected in series to build up a battery module. According to the reference current command of supervisory control, each DAB converter can transfer power back and forth through the high voltage (HV) bus to balance the State of Charge (SoC) between the cells. Each module DAB converter is designed at a 50W power rating. Switch power and transformer losses are analyzed for different switching frequencies, showing the optimum switching frequency for minimum losses. Furthermore, the procedure to select the required gate driver and the PCB layout optimization are discussed. Finally, the DAB performance analysis of GaNbased DAB and Si-based DAB is provided for a battery module operating with a LiFeMnPO4 prismatic cell with 3.2V 20Ah rated values.

active cell balancing↗

NASA NTRS1993

Development of an iron nitrate resistant injector valve for the Space Shuttle orbiter primary thruster

Design of a direct-acting valve (DAV) for a primary thruster which is fully interchangeable with a thruster equipped with pilot-operated valves is described. The DAV is based on a bellows to isolate propellants form the actuator for maximum resistance to iron nitrate and other contamination and to select optimum materials for the actuator. It provides improved seal performance under all operating conditions and insensitivity to pressure transients. As compared with the existing pilot-operated valve, the DAV design is much simpler, consists of fewer parts, and will be lower in cost.

Wichmann, Horst↗

NASA NTRS1994

Stiffening of the ACES deployable space boom

The purpose of this design project was to design an active planar stiffening device for the existing ACES (Acoustic Containerless Experiment System) structure. the ACES structure was modeled using simple beam theory. Various concepts were generated about how the stiffening device should be configured in order to perform at an optimum level. The optimum configuration was selected to be a single set of spreaders located approximately 63% of the distance down the beam. Actuation was to be provided by a DC electric motor. From the test results, the design group was able to draw conclusions and make recommendations about the utility of further research into this area.

Sidwell, Vince↗

NASA NTRS1989

Using computer graphics to design Space Station Freedom viewing

An important aspect of planning for Space Station Freedom at the United States National Aeronautics and Space Administration (NASA) is the placement of the viewing windows and cameras for optimum crewmember use. Researchers and analysts are evaluating the placement options using a three-dimensional graphics program called PLAID. This program, developed at the NASA Johnson Space Center (JSC), is being used to determine the extent to which the viewing requirements for assembly and operations are being met. A variety of window placement options in specific modules are assessed for accessibility. In addition, window and camera placements are analyzed to insure that viewing areas are not obstructed by the truss assemblies, externally-mounted payloads, or any other station element. Other factors being examined include anthropometric design considerations, workstation interfaces, structural issues, and mechanical elements.

Goldsberry, B. S.↗

NASA NTRS1984

K-Band Latching Switches

Design, development, and tests are described for two single-pole-double-throw latching waveguide ferrite switches: a K-band switch in WR-42 waveguide and a Ka-band switch in WR-28 waveguide. Both switches have structurally simple junctions, mechanically interlocked without the use of bonding materials; they are impervious to the effects of thermal, shock, and vibration stresses. Ferrite material for the Ka-band switch with a proper combination of magnetic and dielectric properties was available and resulted in excellent low loss, wideband performance. The high power handling requirement of the K-band switch limited the choice of ferrite to nickel-zinc compositions with adequate magnetic properties, but with too low relative dielectric constant. The relative dielectric constant determines the junction dimensions for given frequency responses. In this case the too low value unavoidably leads to a larger than optimum junction volume, increasing the insertion loss and restricting the operating bandwidth. Efforts to overcome the materials-related difficulties through the design of a composite junction with increased effective dielectric properties efforts to modify the relative dielectric constant of nickel-zinc ferrite are examined.

Piotrowski, W. S.↗

NASA NTRS1998

Bi-Level Integrated System Synthesis (BLISS)

BLISS is a method for optimization of engineering systems by decomposition. It separates the system level optimization, having a relatively small number of design variables, from the potentially numerous subsystem optimizations that may each have a large number of local design variables. The subsystem optimizations are autonomous and may be conducted concurrently. Subsystem and system optimizations alternate, linked by sensitivity data, producing a design improvement in each iteration. Starting from a best guess initial design, the method improves that design in iterative cycles, each cycle comprised of two steps. In step one, the system level variables are frozen and the improvement is achieved by separate, concurrent, and autonomous optimizations in the local variable subdomains. In step two, further improvement is sought in the space of the system level variables. Optimum sensitivity data link the second step to the first. The method prototype was implemented using MATLAB and iSIGHT programming software and tested on a simplified, conceptual level supersonic business jet design, and a detailed design of an electronic device. Satisfactory convergence and favorable agreement with the benchmark results were observed. Modularity of the method is intended to fit the human organization and map well on the computing technology of concurrent processing.

Sobieszczanski-Sobieski, Jaroslaw↗