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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 991 records · Page 55
All sourcesNASA NTRSDOE OSTI
NASA NTRS1979

A dc model for power switching transistors suitable for computer-aided design and analysis

A model for bipolar junction power switching transistors whose parameters can be readily obtained by the circuit design engineer, and which can be conveniently incorporated into standard computer-based circuit analysis programs is presented. This formulation results from measurements which may be made with standard laboratory equipment. Measurement procedures, as well as a comparison between actual and computed results, are presented.

Wilson, P. M.↗
NASA NTRS1979

Effects of diffusion factor, aspect ratio and solidity on overall performance of 14 compressor middle stages

A series of high hub tip radius ratio compressor stages representative of the middle and latter stages of axial flow compressors is discussed. The effects of aspect ratio, diffusion factor, and solidity on rotor and stage performance are determined. Fourteen middle stages are tested to study the effects on performance of varying both diffusion through the rotor and stator blades and blade aspect ratio. The design parameters in the streamline analysis program, the blade geometry program, and the blade coordinate program are presented.

Britsch, W. R.↗
NASA NTRS1979

Analysis of the Effects of Impurities in Silicon

A solar cell fabrication and analysis program to determine the effects on the resultant solar cell efficiency of impurities incorporated into silicon is conducted. Flight quality technologies and quality assurance are employed to assure that variations in cell performance are due to the impurities incorporated in the silicon. The type and level of impurity doping in each test lot is given and the mechanism responsible for the degradation of cell performance is identified and correlated to the doped impurities.

Wohlgemuth, J. H.↗
NASA NTRS1979

The effect of fuel sprays on emissions from a gas turbine combustor

A research gas turbine combustor which allows for independent control of drop size, fuel/air ratio, air inlet temperature, pressure, reference velocity, and residence time has been used to study the influence of fuel spray characteristics on primary zone emissions. Local concentrations of oxides of nitrogen, carbon monoxide and unburned hydrocarbons at various locations in the flow, local gas temperature, gas velocity, and the turbulence intensity (measured with laser velocimetry) are obtained. A comprehensive data analysis program to compute the local fuel/air ratio and the sum of the mole fractions of the species present confirms the validity of the emissions data. Increasing drop size is correlated with an increase in unburned hydrocarbons, while increasing residence time is associated with sharp decreases in hydrocarbons and carbon monoxide and an increase in oxides of nitrogen.

Nicholls, J. A.↗
NASA NTRS1979

Diagnostics of wear in aeronautical systems

The use of appropriate diagnostic tools for aircraft oil wetted components is reviewed, noting that it can reduce direct operating costs through reduced unscheduled maintenance, particularly in helicopter engine and transmission systems where bearing failures are a significant cost factor. Engine and transmission wear modes are described, and diagnostic methods for oil and wet particle analysis, the spectrometric oil analysis program, chip detectors, ferrography, in-line oil monitor and radioactive isotope tagging are discussed, noting that they are effective over a limited range of particle sizes but compliment each other if used in parallel. Fine filtration can potentially increase time between overhauls, but reduces the effectiveness of conventional oil monitoring techniques so that alternative diagnostic techniques must be used. It is concluded that the development of a diagnostic system should be parallel and integral with the development of a mechanical system.

Wedeven, L. D.↗
NASA NTRS1980

Predicting crack propagation

Flaw growth under load is predicted in two dimensions with Advanced Crack Propagation Predictive Analysis Program (FLAGR04). FLAGR04 accommodates variety of cracks, crack transitions, stress gradients, changes in material properties, and Willenberg retardation. Program is written in FORTRAN IV for batch execution and is available for CDC and IBM machines.

Hu, T.↗
NASA NTRS1981

NASTRAN modifications for recovering strains and curvatures

NASTRAN, NASA's general-purpose finite-element structural analysis program, has been modified to allow recovery of surface strains, reference plane strains, and local curvatures at nodes of general plane elements. NASTRAN routines that operate on element stress/strain/temperature relationships and strain/temperature relationships have been modified to incorporate generation and return of strains and curvatures in lieu of stresses. Strains and curvatures are then transformed to material axes and interpolated to generate corresponding strains and curvatures at nodes of element. This interpolation is accomplished using special surface-mapping function.

Chamis, C. C.↗
NASA NTRS1981

An all-FORTRAN version of NASTRAN for the VAX

All FORTRAN version of NASA structural analysis program NASATRAN is implemented on DEC VAX-series computer. Applications of NASATRAN extend to almost every type of linear structure and construction. Two special features are available in VAX version; program is executed from terminal in manner permitting use of VAX interactive debugger, and links are interactively restarted when desired by first making copy of all NASATRAN work files.

Purves, L.↗
NASA NTRS1980

Analysis of the effects of impurities in silicon

A solar cell fabrication and analysis program was conducted to determine the effects on the resultant solar cell efficiency of impurities intentionally incorporated into silicon. It was found that certain impurities such as titanium, tantalum, and vanadium were bad, even in very small concentrations. Cell performance appeared relatively tolerable to impurities such as copper, carbon, calcium, chromium, iron and nickel (in the concentration levels which were considered).

Wohlgemuth, J.↗
NASA NTRS1980

The performance and efficiency of four motor/controller/battery systems for the simpler electric vehicles

A test and analysis program performed on four complete propulsion systems for an urban electric vehicle (EV) is described and results given. A dc series motor and a permanent magnet (PM) motor were tested, each powered by an EV battery pack and controlled by (1) a series/parallel voltage-switching (V-switch) system; and (2) a system using a pulse width modulation, 400 Hz transistorized chopper. Dynamometer tests were first performed, followed by eV performance predictions and data correlating road tests. During dynamometer tests using chopper control; current, voltage, and power were measured on both the battery and motor sides of the chopper, using three types of instrumentation. Conventional dc instruments provided adequate accuracy for eV power and energy measurements, when used on the battery side of the controller. When using the chopper controller, the addition of a small choke inductor improved system efficiency in the lower duty cycle range (some 8% increase at 50% duty cycle) with both types of motors. Overall system efficiency rankings during road tests were: (1) series motor with V-switch; (2) PM motor with V-switch; (3) series motor with chopper; and (4) PM motor with chopper. Chopper control of the eV was smoother and required less driver skill than V-switch control.

Shipps, P. R.↗
NASA NTRS1980

Microcomputer system for medium-sized and experimental finite element analysis

The development of a microcomputer system is described. A series of finite element analysis programs are evaluated in terms of their cost effective application within the microcomputer system. It is shown that the system is practically maintenance free and can be sustained by individual laboratories of standard scale in the educational or academic environment.

Yamada, Y.↗
NASA NTRS1982

Heat-Energy Analysis for Solar Receivers

Heat-energy analysis program (HEAP) solves general heat-transfer problems, with some specific features that are "custom made" for analyzing solar receivers. Can be utilized not only to predict receiver performance under varying solar flux, ambient temperature and local heat-transfer rates but also to detect locations of hotspots and metallurgical difficulties and to predict performance sensitivity of neighboring component parameters.

Lansing, F. L.↗
NASA NTRS1981

Combustor liner durability analysis

An 18 month combustor liner durability analysis program was conducted to evaluate the use of advanced three dimensional transient heat transfer and nonlinear stress-strain analyses for modeling the cyclic thermomechanical response of a simulated combustor liner specimen. Cyclic life prediction technology for creep/fatigue interaction is evaluated for a variety of state-of-the-art tools for crack initiation and propagation. The sensitivity of the initiation models to a change in the operating conditions is also assessed.

Moreno, V.↗
NASA NTRS1981

Integrated Analysis Capability (IAC) development

The technical and programmatic aspects of the integrated analysis capability (IAC) are described. The (IAC) is an interdisciplinary analysis system containing a wide range of general purpose analysis programs that are interfaced via a common data base and a unified executive. The system is designed with significant interactive capability as well as the capability to support the entire range of design phases from the definition phase to the verification phase. The system functions as a standalone or interfaced with IPAD.

Young, J. P.↗
NASA NTRS1980

Study of fuel cell on-site, integrated energy systems in residential/commercial applications

Three building applications were selected for a detailed study: a low rise apartment building; a retail store, and a hospital. Building design data were then specified for each application, based on the design and construction of typical, actual buildings. Finally, a computerized building loads analysis program was used to estimate hourly end use load profiles for each building. Conventional and fuel cell based energy systems were designed and simulated for each building in each location. Based on the results of a computer simulation of each energy system, levelized annual costs and annual energy consumptions were calculated for all systems.

Wakefield, R. A.↗
NASA NTRS1981

Electromagnetic deep-probing (100-1000 kms) of the Earth's interior from artificial satellites: Constraints on the regional emplacement of crustal resources

A spherical harmonic analysis program is being tested which takes magnetic data in universal time from a set of arbitrarily space observatories and calculates a value for the instantaneous magnetic field at any point on the globe. The calculation is done as a least mean-squares value fit to a set of spherical harmonics up to any desired order. The program accepts as a set of input the orbit position of a satellite coordinates it with ground-based magnetic data for a given time. The output is a predicted time series for the magnetic field on the Earth's surface at the (r, theta) position directly under the hypothetically orbiting satellite for the duration of the time period of the input data set. By tracking the surface magnetic field beneath the satellite, narrow-band averages crosspowers between the spatially coordinated satellite and the ground-based data sets are computed. These crosspowers are used to calculate field transfer coefficients with minimum noise distortion. The application of this technique to calculating the vector response function W is discussed.

Hermance, J. F.↗
NASA NTRS1980

Resolving the percentage of component terrains within single resolution elements

An approximate maximum likelihood technique employing a widely available discriminant analysis program is discussed that has been developed for resolving the percentage of component terrains within single resolution elements. The method uses all four channels of Landsat data simultaneously and does not require prior knowledge of the percentage of components in mixed pixels. It was tested in five cases that were chosen to represent mixtures of outcrop, soil and vegetation which would typically be encountered in geologic studies with Landsat data. For all five cases, the method proved to be superior to single band weighted average and linear regression techniques and permitted an estimate of the total area occupied by component terrains to within plus or minus 6% of the true area covered. Its major drawback is a consistent overestimation of the pixel component percent of the darker materials (vegetation) and an underestimation of the pixel component percent of the brighter materials (sand).

Marsh, S. E.↗
NASA NTRS1981

An objective method for forecasting tropical cyclone intensity using Nimbus-5 electrically scanning microwave radiometer measurements

An empirical analysis program, based on finding an optimal representation of the data, is applied to 120 observations of 29 1973 and 1974 North Pacific tropical cyclones. It is found that the algorithms developed from the Nimbus-5 Electrically Scanning Microwave Radiometer (ESMR-5) base alone outperformed the Joint Typhoon Warning Center (JTWC) operational forecast for the 48 and 72 hour maximum wind speed. It is also found that the ESMR-5 data base, when combined with the non-satellite base, produced algorithms that improved the 24 and 48 hour maximum wind-speed forecast by as much as 10% and the 72 hour maximum wind forecast by approximately 16% as compared to the forecast obtained from the algorithms developed from the non-satellite data base alone.

Hunter, H. E.↗