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At least 865 records · Page 48

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NASA NTRS1972

Long term tests of a SNAP-19 thermoelectric generator.

Results of tests performed on a SNAP 19 thermoelectric generator, SN-20. The SN-20 generator was tested for approximately 37,000 hours using electrical heating to simulate the heat released by isotope decay. After 27,000 hours of operation the output power from the generator decreased to approximately 1/3 of the beginning of life value while the internal resistance increased by a factor of 5. Analysis of the test results, confirmed by preliminary metallographic examination, indicated that the output power degradation was the result of excessive sublimation of the thermoelectric material and loss of the hot junction bond due to the depletion of the internal cover gas. This also resulted in excessive junction temperatures. Comparison is made with the behavior observed from the two flight generators and a tentative conclusion is advanced as to the reason for their failure.

Rouklove, P.↗

NASA NTRS1973

NASTRAN data generation of helicopter fuselages using interactive graphics

The development and implementation of a preprocessor system for the finite element analysis of helicopter fuselages is described. The system utilizes interactive graphics for the generation, display, and editing of NASTRAN data for fuselage models. It is operated from an IBM 2250 cathode ray tube (CRT) console driven by an IBM 370/145 computer. Real time interaction plus automatic data generation reduces the nominal 6 to 10 week time for manual generation and checking of data to a few days. The interactive graphics system consists of a series of satellite programs operated from a central NASTRAN Systems Monitor. Fuselage structural models including the outer shell and internal structure may be rapidly generated. All numbering systems are automatically assigned. Hard copy plots of the model labeled with GRID or elements ID's are also available. General purpose programs for displaying and editing NASTRAN data are included in the system. Utilization of the NASTRAN interactive graphics system has made possible the multiple finite element analysis of complex helicopter fuselage structures within design schedules.

Sainsbury-Carter, J. B.↗

NASA NTRS1973

Percy Thomas wind generator designs

The technical and economic feasibilities of constructing a windpowered generator with a capacity of 2,000 to 4,000 kilowatt are considered. Possible benefits of an integrated wind generating electric energy source in an electric utility network are elaborated. Applications of a windpowered waterpump, including its use as a pumping source for hydroelectric pump storage operations, are also mentioned. It is concluded that the greatest potential of the wind generator is to generate heat directly and not conversion to electricity and then to heat.

Lines, C. W.↗

NASA NTRS1974

Laboratory ultrasonic generator

The characteristics of an ultrasonic generator with magnetostrictive amplifiers are described. The generator was designed to supply an output power of about 400 watts at a consumption of about 1 kilowatt. The generator produces sound waves in the frequency range of 18 to 30 KHz. The circuit design is described and examples of the construction are illustrated. The generator is used to study different industrial processes such as the effect of ultrasonic radiation of the emulsification of liquids, the dispersion of solids, and ultrasonic filtration.

Tudose, C.↗

NASA NTRS1974

Hot and cold body reference noise generators from 0 to 40 GHz

This article describes the design, development, and analysis of exceptionally accurate radiometric noise generators from 0-40 GHz to serve as standard references. Size, weight, power, and reliability are optimized to meet the requirements of NASA air- and space-borne radiometers. The radiometric noise temperature of these noise generators is, unavoidably, calculated from measured values rather than measured directly. The absolute accuracy and stability are equal to or better than those of reliable standards available for comparison. A noise generator has been developed whose measurable properties (VSWR, line loss, thermometric temperatures) have been optimized in order to minimize the effects of the uncertainty in the calculated radiometric noise temperatures. Each measurable property is evaluated and analyzed to determine the effects of the uncertainty of the measured value. Unmeasurable properties (primarily temperature gradients) are analyzed, and reasonable precautions are designed into the noise generator to guarantee that the uncertainty of the value remains within tolerable limits.

Hornbostel, D. H.↗

NASA NTRS1975

Controlled generation of large volumes of atmospheric clouds in a ground-based environmental chamber

Atmospheric clouds were generated in a 23,000 cubic meter environmental chamber as the first step in a two part study on the effects of contaminants on cloud formation. The generation procedure was modeled on the terrestrial generation mechanism so that naturally occurring microphysics mechanisms were operative in the cloud generation process. Temperature, altitude, liquid water content, and convective updraft velocity could be selected independently over the range of terrestrially realizable clouds. To provide cloud stability, a cotton muslin cylinder 29.3 meters in diameter and 24.2 meters high was erected within the chamber and continuously wetted with water at precisely the same temperature as the cloud. The improved instrumentation which permitted fast, precise, and continual measurements of cloud temperature and liquid water content is described.

Hettel, H. J.↗

NASA NTRS1974

Performance testing of thermoelectric generators at JPL

Results of life tests of thermoelectric generators ranging in output power from 800 microwatts to 170 watts. Emphasis is placed on the results obtained from tests of three advanced prototypes - a high-performance generator, a transit-type generator, and a ring converter. In addition, the results of life tests of a number of generators representing Nimbus, Pioneer, and Viking technology are presented.

Rouklove, P.↗

NASA NTRS1975

Dynamo generation in Mercury

Models of the interior and thermal evolution of Mercury calculated by Siegfried and Solomon (1974) using Lewis' (1972) cosmochemical calculations to constrain the composition are tested for four necessary conditions for MHD dynamo generation. It is shown that dynamo generation requires at least a partially fluid interior, an energy source that drives a flow of core fluid relative to the rigidly rotating planet, a magnetic-field diffusion time in excess of the characteristic fluid-flow time scale, and a fluid flow of sufficient complexity to satisfy Cowling's (1934) theorem. It is concluded that a literal interpretation of Lewis' calculations implies that dynamo generation in Mercury is improbable. Generation would be possible only if the metallic core were contaminated with substantial amounts of radioactive material.

Stevenson, D. J.↗

NASA NTRS1975

A study of sound generation in subsonic rotors, volume 2

Computer programs were developed for use in the analysis of sound generation by subsonic rotors. Program AIRFOIL computes the spectrum of radiated sound from a single airfoil immersed in a laminar flow field. Program ROTOR extends this to a rotating frame, and provides a model for sound generation in subsonic rotors. The program also computes tone sound generation due to steady state forces on the blades. Program TONE uses a moving source analysis to generate a time series for an array of forces moving in a circular path. The resultant time series are than Fourier transformed to render the results in spectral form. Program SDATA is a standard time series analysis package. It reads in two discrete time series and forms auto and cross covariances and normalizes these to form correlations. The program then transforms the covariances to yield auto and cross power spectra by means of a Fourier transformation.

Chalupnik, J. D.↗

NASA NTRS1976

Evaluation of a spacecraft nitrogen generator

A method is discussed of generating nitrogen for cabin leakage makeup aboard space vehicles having longer duration missions. The nitrogen generation concept is based on using liquid hydrazine as the stored form of nitrogen to reduce the higher tankage and expendables weight associated with high pressure gaseous or cryogenic liquid nitrogen storage. The hydrazine is catalytically dissociated to yield a mixture of nitrogen and hydrogen. The nitrogen/hydrogen mixture is then separated to yield the makeup nitrogen. The excess supply of hydrogen would be available for use in the reduction of metabolic carbon dioxide. A detailed comparison was completed of Palladium/Silver and Polymer Electrochemical-based Nitrogen Generation Systems. The palladium/silver-based system was judged better than the Polymer Electrochemical Nitrogen Generation System because of lower expendable weight and palladium/silver nitrogen/hydrogen separation represents 'off-the-shelf' technology.

Marshall, R. D.↗

NASA NTRS1977

An automated data generator for NASTRAN

A modeling system based on construction-in-context of geometry and physical properties data is adapted for NASTRAN finite element data generation. This system was originally developed for generating three-dimensional finite data for composite structures in PATCHES-III using parametric cubic models. These finite line, surface and volume models constructed using simple data directives will be subdivided into NASTRAN finite elements and their supporting data in the new data generator. Any geometry can be constructed as illustrated by a compressor fan blade with camber, twist and changing airfoil section and the shape then subdivided using a uniform or non-uniform mesh. Special emphasis is given to the adaption of construction-in-context to composite material property modeling. A PMAT series of directives is described for any one, two or three-dimensionally reinforced composite that allows the phase properties, as well as composite properties, to be generated.

Stanton, E. L.↗

NASA NTRS1978

Power train analysis for the DOE/NASA 100-kW wind turbine generator

Progress in explaining variations of power experienced in the on-line operation of a 100 kW experimental wind turbine-generator is reported. Data are presented that show the oscillations tend to be characteristic of a wind-driven synchronous generator because of low torsional damping in the power train, resonances of its large structure, and excitation by unsteady and nonuniform wind flow. The report includes dynamic analysis of the drive-train torsion, the generator, passive driveline damping, and active pitch control as well as correlation with experimental recordings. The analysis assumes one machine on an infinite bus with constant generator-field excitation.

Seidel, R. C.↗

NASA NTRS1979

The design of relatively machine-independent code generators

Two complementary approaches were investigated. In the first approach software design techniques were used to design the structure of a code generator for Halmat. The major result was the development of an intermediate code form known as 7UP. The second approach viewed the problem as one in providing a tool to the code generator programmer. The major result was the development of a non-procedural, problem oriented language known as CGGL (Code Generator Generator Language).

Noonan, R. E.↗

NASA NTRS1979

Performance optimization of an MHD generator with physical constraints

A method to optimize the Faraday MHD generator performance under a prescribed set of electrical and magnet constraints is described. The results of generator performance calculations using this technique are presented for a very large MHD/steam plant. The differences between the maximum power and maximum net power generators are described. The sensitivity of the generator performance to the various operational parameters are presented.

Pian, C. C. P.↗

NASA NTRS1979

Technology advancement of an oxygen generation subsystem

An oxygen generation subsystem based on water electrolysis was developed and tested to further advance the concept and technology of the spacecraft air revitalization system. Emphasis was placed on demonstrating the subsystem integration concept and hardware maturity at a subsystem level. The integration concept of the air revitalization system was found to be feasible. Hardware and technology of the oxygen generation subsystem was demonstrated to be close to the preprototype level. Continued development of the oxygen generation technology is recommended to further reduce the total weight penalties of the oxygen generation subsystem through optimization.

Lee, M. K.↗

NASA NTRS1979

Turbulence generated by the interaction of entropy fluctuations with non-uniform mean flows

The turbulence generated by random entropy fluctuations in an accelerating stream is analyzed. The results are obtained by using rapid distortion theory together with a high frequency solution of a previously developed wave equation that governs the small-amplitude unsteady vortical and entropic motion on steady potential flows (Goldstein, 1978). Simple results are obtained for the case of symmetric contraction, expansion or combination of the two. It is shown that the energy of the entropy-generated turbulence increases more rapidly with the contraction ratio of a subsonic flow than that of any imposed upstream turbulence. This result indicates that the entropy-generated turbulence may be more significant than the hydrodynamically generated turbulence in the turbine stages of aircraft engines.

Goldstein, M. E.↗

NASA NTRS1979

Lewis Research Center studies of multiple large wind turbine generators on a utility network

A NASA-Lewis program to study the anticipated performance of a wind turbine generator farm on an electric utility network is surveyed. The paper describes the approach of the Lewis Wind Energy Project Office to developing analysis capabilities in the area of wind turbine generator-utility network computer simulations. Attention is given to areas such as, the Lewis Purdue hybrid simulation, an independent stability study, DOE multiunit plant study, and the WEST simulator. Also covered are the Lewis mod-2 simulation including analog simulation of a two wind turbine system and comparison with Boeing simulation results, and gust response of a two machine model. Finally future work to be done is noted and it is concluded that the study shows little interaction between the generators and between the generators and the bus.

Gilbert, L. J.↗

NASA NTRS1979

Control and stabilization of the DOE/NASA Mod-1 two megawatt wind turbine generator

This paper describes the controls design, performance simulation process and specialized dynamic considerations for the DOE/NASA Mod 1 wind turbine generator (WTG). It shows controls, structural and utility interface considerations of the wind turbine generator and shows how a wind turbine generator can be integrated with a synchronous power system. Differences with respect to fossil or hydro generation and their implications are vital to long-term WTG reliability and availability and acceptance by utilities and consumers. The paper describes the control performance requirements to provide stable pitch and excitation control with drivetrain torsional dynamics, and the control of power swing stability and utility feeder voltage due to wind gusts.

Barton, R. S.↗