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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 1,315 records · Page 73
All sourcesNASA NTRSDOE OSTI
NASA NTRS1971

Cold startup and low temperature performance of the Brayton cycle electrical subsystem

Cold performance tests and startup tests were conducted on the Brayton-cycle inverter, motor-driven pump, dc supply, speed control with parasitic load resistor and the Brayton control system. These tests were performed with the components in a vacuum and mounted on coldplates. A temperature range of ?25 to -50 C was used for the tests. No failures occurred, and component performance gave no indication that there would be any problem with the safe operation of the Brayton power generating system.

Vrancik, J. E.↗
NASA NTRS1975

Airloads investigation of an 0.030 scale model of the space shuttle vehicle 140A/B launch configuration (model 47-OTS) in the ARC 9 by 7 foot unitary plan wind tunnel for Mach 1.55 and 2.2 (iA14B), volume 1

Tests were conducted in September, 1973 on a launch vehicle configuration consisting of a space shuttle orbiter, an external tank, two solid rocket boosters, and associated intercomponent attach hardware. Model variables included elevon, rudder, and speed brake deflections. Aerodynamic loads were measured and surface pressure distributions were obtained simultaneously with six-component stability and control force data on the complete configuration. Angles of attack and sideslip were also investigated.

Gillins, R. L.↗
NASA NTRS1976

The effects of trailing vorticity on the flow through highly loaded cascades

This paper presents a procedure whereby three-dimensional inviscid flow through a highly loaded turbomachinery cascade of lifting lines can be treated by methods corresponding to classical aerodynamic theory. In contrast to earlier linearized (thin airfoil) three-dimensional theory, the present study allows analysis of the flow corresponding to the large turning and/or large pressure ratios induced by practical rotors or stators. For the sake of simplicity, the present paper is limited to incompressible flow through a highly loaded rectilinear cascade and to the design problem; i.e., given blade loading. Formulas are derived for both the mean and the three-dimensional components of the flow; in particular, the velocities at the blades induced by the trailing vorticity associated with nonuniform blade circulation are determined.

Mccune, J. E.↗
NASA NTRS1980

Preliminary results of steady state characterization of near term electric vehicle breadboard propulsion system

The steady state test results on a breadboard version of the General Electric Near Term Electric Vehicle (ETV-1) are discussed. The breadboard was built using exact duplicate vehicle propulsion system components with few exceptions. Full instrumentation was provided to measure individual component efficiencies. Tests were conducted on a 50 hp dynamometer in a road load simulator facility. Characterization of the propulsion system over the lower half of the speed-torque operating range has shown the system efficiency to be composed of a predominant motor loss plus a speed dependent transaxle loss. At the lower speeds with normal road loads the armature chopper loss is also a significant factor. At the conditions corresponding to a cycle for which the vehicle system was specifically designed, the efficiencies are near optimum.

Sargent, N. B.↗
NASA NTRS1983

Automation concepts for large space power systems

A study was undertaken to develop a methodology for analyzing, selecting, and implementing automation functions for multi-hundred-kW photovoltaic power systems intended for manned space station. The study involved identification of generic power system elements and their potential faults, definition of automation functions and their resulting benefits, and partitioning of automation functions between power subsystem, central spacecraft computer, and ground. Automation to a varying degree was concluded to be mandatory to meet the design and operational requirements of the space station. The key drivers are indefinite lifetime, modular growth, high performance flexibility, a need to accommodate different electrical user load equipment, on-orbit assembly/maintenance/servicing, and potentially large number of power subsystem components. Functions that are good candidates for automation via expert system approach includes battery management and electrical consumables management.

Imamura, M. S.↗
NASA NTRS1986

Calculating Bearing Forces From Strain-Gage Signals

Technique for obtaining force components on cylindrical bearing holder uses pairs of opposing strain gages. Signals proportional to outputs of pairs of opposing gages subtracted from each other. Subtraction nearly eliminates crosstalk between orthogonal force components. Signal-processing technique equally applicable to rotating as well as stationary loads.

Fenwick, J. R.↗
NASA NTRS1982

Structural analysis

Hot section components of aircraft gas turbine engines are subjected to severe thermal-structural loading conditions, especially during the start-up and take-off portions of the engine cycle. The most severe and damaging stresses and strains are those induced by the steep thermal gradients induced during the start-up transient. These transient stresses and strains are also the most difficult to predict, in part because the temperature gradients and distributions are not well known or predictable, and also because the cyclic elasto-viscoplastic behavior of the materials at these extremes of temperature and strain are not well known or predictable. One element of the structures program will develop improved time-varying thermal-mechanical load models for the entire engine mission cycle from start-up to shutdown. The thermal model refinements will be consistent with those required by the structural code including considerations of mesh-point density, strain concentrations, and thermal gradients. Models will be developed for the burner liner, turbine vane and turbine blade.

Johns, R. H.↗
NASA NTRS1985

Cyclic structural analyses of anisotropic turbine blades for reusable space propulsion systems

Turbine blades for reusable space propulsion systems are subject to severe thermomechanical loading cycles that result in large inelastic strains and very short lives. These components require the use of anisotropic high-temperature alloys to meet the safety and durability requirements of such systems. To assess the effects on blade life of material anisotropy, cyclic structural analyses are being performed for the first stage high-pressure fuel turbopump blade of the space shuttle main engine. The blade alloy is directionally solidified MAR-M 246 alloy. The analyses are based on a typical test stand engine cycle. Stress-strain histories at the airfoil critical location are computed using the MARC nonlinear finite-element computer code. The MARC solutions are compared to cyclic response predictions from a simplified structural analysis procedure developed at the NASA Lewis Research Center.

Manderscheid, J. M.↗
NASA NTRS1985

Large deflection behavior of quasi-isotropic laminates under low-velocity impact type point loading

Eight-ply quasi-isotropic circular composite plates of Thornel 300 graphite in Narmco 5208 epoxy resin (T300/5208) were analyzed to obtain the large deformation behavior under low-velocity impact type point loads. A simple plate-membrane coupling model was developed. The impact type point loads were replaced by equivalent quasi-static point loads. The plate-membrane coupling model was used to obtain the large deformation shapes for the thin circular composite laminates. The analyses indicated that the large deformation shapes of the composite plates under point loads vary with the center point displacements, and hence are different for different load levels. Quasi-isotropic plates were analyzed by replacing anisotropic bending stiffness components with the equivalent flexural stiffness for the isotropic plates. The plate-membrane coupling model was verified by conducting a series of tests on clamped circular quasi-isotropic laminates. Deflected shapes for the thin composite plates were experimentally obtained. These shapes agreed well with the analytically predicted shapes.

Kelkar, A.↗
NASA NTRS1985

Three-dimensional inviscid analysis of radial turbine flow and a limited comparison with experimental data

The three-dimensional inviscid DENTON code is used to analyze flow through a radial-inflow turbine rotor. Experimental data from the rotor are compared with analytical results obtained by using the code. The experimental data available for comparison are the radial distributions of circumferentially averaged values of absolute flow angle and total pressure downstream of the rotor exit. The computed rotor-exit flow angles are generally underturned relative to the experimental values, which reflect the boundary-layer separation at the trailing edge and the development of wakes downstream of the rotor. The experimental rotor is designed for a higher-than-optimum work factor of 1.126 resulting in a nonoptimum positive incidence and causing a region of rapid flow adjustment and large velocity gradients. For this experimental rotor, the computed radial distribution of rotor-exit to turbine-inlet total pressure ratios are underpredicted due to the errors in the finite-difference approximations in the regions of rapid flow adjustment, and due to using the relatively coarser grids in the middle of the blade region where the flow passage is highly three-dimensional. Additional results obtained from the three-dimensional inviscid computation are also presented, but without comparison due to the lack of experimental data. These include quasi-secondary velocity vectors on cross-channel surfaces, velocity components on the meridional and blade-to-blade surfaces, and blade surface loading diagrams. Computed results show the evolution of a passage vortex and large streamline deviations from the computational streamwise grid lines. Experience gained from applying the code to a radial turbine geometry is also discussed.

Choo, Y. K.↗
NASA NTRS1985

Cyclic structural analyses of anisotropic turbine blades for reusable space propulsion systems

Turbine blades for reusable space propulsion systems are subjects to severe thermomechanical loading cycles that result in large inelastic strains and very short lives. These components require the use of anisotropic high temperature alloys to meet the safety and durability requirements of such systems. To assess the effects on blade life of material anisotropy, cyclic structural analyses are being performed for the first stage high pressure fuel turbopump blade (HPFTB) of the space shuttle main engine (SSME). The blade alloy is directionally solidified MAR-M 246 alloy. The analyses are based on a typical test stand engine cycle. Stress-strain histories at the airfoil critical location are computed using the MARC nonlinear finite element computer code.

Manderscheid, J. M.↗
NASA NTRS1985

Three-dimensional inviscid analysis of radial-turbine flow and a limited comparison with experimental data

The three-dimensional inviscid DENTON code is used to analyze flow through a radial-inflow turbine rotor. Experimental data from the rotor are compared with analytical results obtained by using the code. The experimental data available for comparison are the radial distributions of circumferentially averaged values of absolute flow angle and total pressure downstream of the rotor exit. The computed rotor-exit flow angles are generally underturned relative to the experimental values, which reflect the boundary-layer separation at the trailing edge and the development of wakes downstream of the rotor. The experimental rotor is designed for a higher-than-optimum work factor of 1.126 resulting in a nonoptimum positive incidence and causing a region of rapid flow adjustment and large velocity gradients. For this experimental rotor, the computed radial distribution of rotor-exit to turbine-inlet total pressure ratios are underpredicted due to the errors in the finite-difference approximations in the regions of rapid flow adjustment, and due to using the relatively coarser grids in the middle of the blade region where the flow passage is highly three-dimensional. Additional results obtained from the three-dimensional inviscid computation are also presented, but without comparison due to the lack of experimental data. These include quasi-secondary velocity vectors on cross-channel surfaces, velocity components on the meridional and blade-to-blade surfaces, and blade surface loading diagrams. Computed results show the evolution of a passage vortex and large streamline deviations from the computational streamwise grid lines. Experience gained from applying the code to a radial turbine geometry is also discussed.

Choo, Y. K.↗
NASA NTRS1988

Utilization of artificial intelligence techniques for the Space Station power system

Due to the complexity of the Space Station Electrical Power System (EPS) as currently envisioned, artificial intelligence/expert system techniques are being investigated to automate operations, maintenance, and diagnostic functions. A study was conducted to investigate this technology as it applies to failure detection, isolation, and reconfiguration (FDIR) and health monitoring of power system components and of the total system. Control system utilization of expert systems for load scheduling and shedding operations was also researched. A discussion of the utilization of artificial intelligence/expert systems for Initial Operating Capability (IOC) for the Space Station effort is presented along with future plans at Rocketdyne for the utilization of this technology for enhanced Space Station power capability.

Evatt, Thomas C.↗
NASA NTRS1989

Analytical and finite element solutions of some problems using a viscoplastic model

The feasibility of using a viscoplastic model developed by Robinson to perform a nonlinear structural analysis was investigated. The paper presents analytical solutions for three classical problems: (1) a pressurized thick-walled cylinder, (2) a thin rotating disk, and (3) a pressurized thick-walled sphere. The analytical expressions derived for the stress and the strain rates for these components are general in nature as they consider both the mechanical and thermal loadings to be time-dependent. A computer program VISTAN (VIscoplastic STructural ANalyzer) was developed to obtain the stress and strain distributions. The finite element solutions for these problems are also presented. The numerical results pertaining to isothermal loading conditions are provided. The results obtained demonstrate the feasibility of using the viscoplastic model developed by Robinson to perform nonlinear structural analyses.

Arya, V. K.↗
NASA NTRS1992

High-alpha vortex decoupling investigations on a chine forebody/Delta wing configuration at transonic Mach numbers

A test program conducted in the LaRC 8-foot Transonic Pressure Tunnel on a blended chine/delta wing model to verify the concept of controlled vortex decoupling via inboard leading-edge flaps for improved high-alpha lateral/directional characteristics is discussed. This test extended the Mach number range of a data base previously generated in a LaRC 7 ft. by 10 ft High Speed Tunnel investigation. Six-component force/moment, forebody surface pressures, and central and twin tall static and dynamic loads were measured at Mach numbers of 0.4 to 1.2; laser light-sheet visualizations were also performed. Selected data are analyzed and discussed, emphasizing lateral/directional improvements and tail environment enhanced attainable by leading-edge flaps in the maximum lift region.

Rao, Dhanvada M.↗
NASA NTRS1992

Multidisciplinary tailoring of hot composite structures

A computational simulation procedure is described for multidisciplinary analysis and tailoring of multilayered multimaterial hot composite engine structural components subjected to simultaneous multiple discipline-specific thermal, structural, vibration, and acoustic loadings including the effect of aggressive environments. The simulation is based on a 3D finite element analysis technique in conjunction with structural mechanics codes, thermal/acoustic analysis methods, and tailoring procedures. The integrated multidisciplinary simulation procedure is general-purpose including the coupled effects of nonlinearities in structure geometry, material, loading, and environmental complexities. The composite material behavior is assessed at all composite scales, i.e., the laminate/ply/constituents (fiber/matrix), via a nonlinear material characterization hygro-thermomechanical model. Sample tailoring cases exhibiting nonlinear material/loading/environmental behavior of aircraft engine fan blades, are presented. The various multidisciplinary loadings lead to different tailored designs, even those opposite of each other, as in the case of minimum material cost versus minimum structure weight and in the case of minimum vibration frequency versus minimum acoustic noise.

Singhal, Surendra N.↗
NASA NTRS1993

Multidisciplinary tailoring of hot composite structures

A computational simulation procedure is described for multidisciplinary analysis and tailoring of layered multi-material hot composite engine structural components subjected to simultaneous multiple discipline-specific thermal, structural, vibration, and acoustic loads. The effect of aggressive environments is also simulated. The simulation is based on a three-dimensional finite element analysis technique in conjunction with structural mechanics codes, thermal/acoustic analysis methods, and tailoring procedures. The integrated multidisciplinary simulation procedure is general-purpose including the coupled effects of nonlinearities in structure geometry, material, loading, and environmental complexities. The composite material behavior is assessed at all composite scales, i.e., laminate/ply/constituents (fiber/matrix), via a nonlinear material characterization hygro-thermo-mechanical model. Sample tailoring cases exhibiting nonlinear material/loading/environmental behavior of aircraft engine fan blades, are presented. The various multidisciplinary loads lead to different tailored designs, even those competing with each other, as in the case of minimum material cost versus minimum structure weight and in the case of minimum vibration frequency versus minimum acoustic noise.

Singhal, Surendra N.↗
NASA NTRS2001

Simulation of Aircraft Engine Blade-Out Structural Dynamics

A primary concern of aircraft structure designers is the accurate simulation of the blade-out event and the subsequent windmilling of the engine. Reliable simulations of the blade-out event are required to insure structural integrity during flight as well as to guarantee successful blade-out certification testing. The system simulation includes the lost blade loadings and the interactions between the rotating turbomachinery and the remaining aircraft structural components. General-purpose finite element structural analysis codes such as MSC NASTRAN are typically used and special provisions are made to include transient effects from the blade loss and rotational effects resulting from the engine's turbomachinery. The present study provides the equations of motion for rotordynamic response including the effect of spooldown speed and rotor unbalance and examines the effects of these terms on a cantilevered rotor. The effect of spooldown speed is found to be greater with increasing spooldown rate. The parametric term resulting from the mass unbalance has a more significant effect on the rotordynamic response than does the spooldown term. The parametric term affects both the peak amplitudes as well as the resonant frequencies of the rotor.

Lawrence, Charles↗