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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 469 records · Page 26
All sourcesNASA NTRSDOE OSTI
NASA NTRS1992

Three-dimensional flow phenomena in a transonic, high-through-flow, axial-flow compressor stage

A detailed aerodynamic study of a transonic, high-through-flow, single stage compressor is presented. The compressor stage was comprised of a low-aspect-ratio rotor combined alternately with two different stator designs. Both experimental and numerical studies are conducted to understand the details of the complex flow field present in this stage. Aerodynamic measurements using high-frequency, Kulite pressure transducers and conventional probes are compared with results from a three-dimensional viscous flow analysis. A steady multiple blade row approach is used in the numerical technique to examine the detailed flow structure inside the rotor and the stator passages. The comparisons indicate that many flow field features are correctly captured by viscous flow analysis, and therefore unmeasured phenomena can be studied with some level of confidence.

Copenhaver, William W.↗
NASA NTRS1992

Structural and loads analysis of a two-stage fully reusable Advanced Manned Launch System

The conceptual design of a rocket-powered, two-stage fully reusable launch vehicle has been performed as a part of NASA's Advanced Manned Launch System (AMLS) study. This paper summarizes the structural design and loads analysis of this two-stage fully reusable launch vehicle. The method used to determine the structural weights consists of generating a finite-element model for each vehicle, selecting a set of critical loading conditions, determining the loads on the model caused by those conditions, determining the model response and changing the sizes of individual elements to obtain a safe structure. The integrated loads on the two-stage vehicle were obtained from a three-degrees-of-freedom trajectory analysis.

Robinson, James C.↗
NASA NTRS1993

Determining successional stage of temperate coniferous forests with Landsat satellite data

Thematic Mapper (TM) digital imagery was used to map forest successional stages and to evaluate spectral differences between old-growth and mature forests in the central Cascade Range of Oregon. Relative sun incidence values were incorporated into the successional stage classification to compensate for topographic induced variation. Relative sun incidence improved the classification accuracy of young successional stages, but did not improve the classification accuracy of older, closed canopy forest classes or overall accuracy. TM bands 1, 2, and 4; the normalized difference vegetation index; and TM 4/3, 4/5, and 4/7 band ratio values for o|d-growth forests were found to be significantly lower than the values of mature forests. The Tasseled Cap features of brightness, greenness, and wetness also had significantly lower old-growth values as compared to mature forest values .

Fiorella, Maria↗
NASA NTRS1993

Averaging techniques for steady and unsteady calculations of a transonic fan stage

It is often desirable to characterize a turbomachinery flow field with a few lumped parameters such as total pressure ratio or stage efficiency. Various averaging schemes may be used to compute these parameters. Here three averaging schemes, the momentum, energy, and area averaging schemes, are described and compared for two computed solutions of the midspan section of a transonic fan stage: a steady averaging-plane solution in which average rotor outflow conditions were used as stator inflow conditions and an unsteady rotor-stator interaction solution. The unsteady solution is described, some unsteady flow phenomena are discussed and the steady pressure distributions are compared. Despite large unsteady pressure fluctuations on the stator surface, the steady pressure distribution matched the average unsteady distribution almost exactly. Stator wake profiles, stator loss coefficient, and stage efficiency were computed for the two solutions with the three averaging schemes and are compared. In general the energy averaging scheme gave good agreement between the averaging-plane solution and the time-averaged unsteady solution, even though certain phenomena due to unsteady wake migration were neglected.

Wyss, M. L.↗
NASA NTRS1993

Unsteady aerodynamic flow phenomena in a transonic compressor stage

A three-dimensional unsteady, viscous aerodynamic analysis has been developed for the flow inside a transonic, high-through-flow, single stage compressor. The compressor stage is comprised of a low-aspect-ratio rotor and a closely coupled stator. The analysis is based on a numerical method for solving the three-dimensional Navier-Stokes equation for unsteady viscous flow through multiple turbomachinery blade rows. The method solves the fully three-dimensional Navier-Stokes equation with an implicit scheme. A two-equation turbulence model with a low-Reynolds-number modification is applied for the turbulence closure. A third-order accurate upwinding scheme is used to approximate convection terms while a second-order accurate central difference scheme is used for the discretization of the viscous terms. A second-order accurate scheme is employed for the temporal discretization. The numerical method is applied to study the unsteady flow field inside a transonic, high-through-flow, axial compressor stage. The numerical results are compared with available experimental data.

Hah, C.↗
NASA NTRS1993

Design and test of a small two stage counter-rotating turbine for rocket engine application

The aerodynamic design and rig test evaluation of a small counter-rotating turbine system is described. The technology represented by this turbine is being developed for application in an advanced upper stage rocket engine turbopump. This engine will employ an oxygen/hydrogen expander cycle and achieve high performance through efficient combustion, high combustion pressure, and high area ratio exhaust nozzle expansion. Engine performance goals require that the turbopump drive turbines achieve high efficiency at low gas flow rates. The low flow rates result in very small airfoil diameter, height and chord. The high efficiency and small size requirements present a challenging turbine design problem. The unconventional approach employed to meet this challenge is described, along with the detailed design process and resulting airfoil configurations. The method and results of full scale aerodynamic performance evaluation testing of both one and two stage configurations, as well as operation without the secondary stage stator are presented. The overall results of this effort illustrate that advanced aerodynamic design tools and hardware fabrication techniques have provided improved capability to produce small high performance turbines for advanced rocket engines.

Huber, F. W.↗
NASA NTRS1993

Three-dimensional flow analysis inside turbomachinery stages with steady and unsteady Navier-Stokes method

This study presents a numerical method for solving the three-dimensional, Navier-Stokes equations for unsteady, viscous flow through multiple turbomachinery blade rows. The method solves the fully three-dimensional Navier-Stokes equations with an implicit scheme which is based on a control volume approach. A two-equation turbulence model with a low Reynolds number modification is employed in the present study. A third-order accurate upwinding scheme is used to approximate convection terms while a second order accurate central difference scheme is used for the discretization of viscous terms. A second-order accurate scheme is employed for the temporal discretization. The numerical method is applied to study the unsteady flow field of a subsonic turbine stage and the unsteady flow field inside a transonic, high-through-flow, axial compressor stage. The stage calculation is performed by coupling the stator and the rotor flow fields at each time step through an over-laid grid.

Copenhaver, W. W.↗
NASA NTRS1941

Two-stage Supercharging

The arrangement of the parts and the installation and control problems of the two-stage mechanically driven superchargers for aircraft engines are discussed. Unless an entirely new form of supercharging is developed, there will be a definite need for a two-stage centrifugal supercharger. It is shown that the two-stage mechanically driven supercharger itself is a comparatively simple device; the complications arise from the addition of inter-coolers and controls.

Buck, Richard S↗
NASA NTRS1950

Altitude Performance and Operational Characteristics of 29-inch-diameter Tail-pipe Burner with Several Fuel Systems and Fuel-cooled Stage-type Flame Holders on J35-A-5 Turbojet Engine / Richard L. Golladay and Harry E. Bloomer

An investigation of tail-pipe burning was conducted in the NACA Lewis altitude wind tunnel with a full-scale turbojet engine and an 29-inch-diameter tail-pipe burner. Effects of fuel distribution and number and arrangement of stages on performance and operational characteristics of several fuel-cooled flame holders are presented and discussed. Operation with a three-stage flame holder having the large stage upstream was the most efficient. Combustion efficiency was slightly increased at high altitudes by injecting fuel upstream of the flame holder.

TURBINES, GAS - AFTERBURNING↗
NASA NTRS1951

Performance of single-stage compressor designed on basis of constant total enthalpy with symmetrical velocity diagram at all radii and velocity ratio of 0.7 at rotor hub / Jack R. Burtt and Robert J. Jackson

A typical inlet axial-flow compressor inlet stage, which was designed on the basis of constant total enthalpy with symmetrical velocity diagram at all radii, was investigated. At a tip speed of 1126 feet per second, a peak pressure ratio of 1.28 was obtained at an efficiency of 0.76. At a tip speed, the highest practical flow was 28 pounds per second per square foot frontal area with an efficiency of 0.78. Data for a rotor relative inlet Mach number range of from 0.5 to 0.875 indicates that the critical value for any stage radial element is approximately 0.80 for the stage investigated.

FANS↗
NASA NTRS1953

Performance of a turbojet engine with adjustable first-stage turbine stator and variable-area exhaust nozzle

The performance of a turbojet engine with a two-stage turbine, an adjustable first-stage turbine stator, and a variable-area exhaust nozzle was investigated at selected constant engine speeds and two simulated flight conditions. For the particular component characteristics of the engine investigated, little improvement in thrust levels of interest by use of an adjustable rather than an optimum fixed first-stage turbine stator.

ENGINES, TURBOJET↗
NASA NTRS1953

Effect of Axially Staged Fuel Introduction on Performance of One-quarter Sector of Annular Turbojet Combustor

The design principle of injecting liquid fuel at more than one axial station in an annual turbojet combustor was investigated. Fuel was injected into the combustor as much as 5 inches downstream of the primary fuel injectors. Many fuel-injection configurations were examined and the performance results are presented for 11 configurations that best demonstrate the trends in performance obtained. The performance investigations were made at a constant combustor-inlet pressure of 15 inches of mercury absolute and at air flows up to 70 percent higher than values typical of current design practice. At these higher air flows, staging the fuel introduction improved the combustion efficiency considerably over that obtained in the combustor when no fuel staging was employed. At air flows currently encountered in turbojet engines, fuel staging was of minor value. Radial temperature distribution seemed relatively unaffected by the location of fuel-injection stations.

COMBUSTION - EFFECT OF ENGINE OPERATING CONDITIONS↗
NASA NTRS1954

Multiple over-all performance and rotating-stall characteristics of a 15-stage experimental axial-flow compressor at an intermediate speed

The 15-stage experimental axial-flow compressor was investigated at 78.5 percent of design speed, which falls in the region of the surge-limit line discontinuity. In this region indications of multiple characteristic curves of compressor operation had been found. On the basis of previous stage-matching analyses, these multiple performance characteristics appear to be the result of multiple-valued stage performance characteristics. At this speed of 78.5 percent, at least six separate characteristic performance curves were found, associated with five different numbers of rotating stall configurations, from zero to four stall zones. It was difficult in many cases to repeat a given performance curve by approaching the test speed in a similar manner, and many of the curves were not stable, the no-stall curve being the only definitely repeatable one. In some cases a jump from one curve to another took place at the surge point, while in others the change occurred within the usual limits of a conventional performance curve and without any sudden obvious changes in observed data. In general, as the number of zones in the rotating-stall pattern decreased, the maximum weight flow, maximum efficiency, and maximum pressure ratio of the resultant curves were increased. It appears, therefore, that multiple performance characteristics at the given speed are encountered in the region of the discontinuity of the surge line.

Lucas, James G↗
NASA NTRS1957

Analytical and Experimental Investigation of the Effects of Compressor Interstage Air Bleed on Performance Characteristics of a 13-stage Axial-flow Compressor

Air was bled over the fifth-and tenth-stage rotor-blade rows through ports designed to pass 11 and 9 percent of the inlet flow, respectively, at 80 percent speed. Along the rated operating line the maximum speed at which rotating stall was encountered was lowered by either of these bleeds, and the stall patterns below these speeds were altered so that no dangerous resonant rotor-blade bending vibrations were excited. The combination of the two bleeds completely eliminated rotating stall to at least 50 percent speed. The compressor-discharge weight flow was decreased only at intermediate speeds, and the overall pressure ratio was affected only at intermediate speeds, and the overall pressure ratio was affected only by the combination bleed at intermediate speeds. Fifth-stage bleed increased compressor efficiency at low speeds, and tenth-stage bleed decreased efficiency at intermediate speeds.

Lucas, James G↗
NASA NTRS1994

Two-Stage Series-Resonant Inverter

Two-stage inverter includes variable-frequency, voltage-regulating first stage and fixed-frequency second stage. Lightweight circuit provides regulated power and is invulnerable to output short circuits. Does not require large capacitor across ac bus, like parallel resonant designs. Particularly suitable for use in ac-power-distribution system of aircraft.

Stuart, Thomas A.↗
NASA NTRS1990

TROJID: A portable software package for upper-stage trajectory optimization

Performance optimization for upper-stage exoatmospheric vehicles often is performed within the framework of a full capability trajectory simulation package requiring either a large mainframe computer or powerful work-station. Since these software packages tend to include capabilities providing for high-fidelity boost and reentry simulations, the programs usually are quite large and not very portable. The program TROJID is an attempt to provide an environment for the optimization of upper-stage trajectories within a small package capable of being run on a standard desktop microcomputer. Utilizing a state-of-the-art nonlinear programming algorithm and a trajectory simulator implementing impulsive burns and an analytic coast phase propagator, TROJID is capable of producing trajectories for optimal multi-burn upper-stage orbit transfers. The package has been designed to allow full generality in definition of both the trajectory simulator and the parameter optimization problem.

Hammes, Steven M.↗
NASA NTRS1993

A two-stage (turbulent-drainage) mechanism for the emplacement of impact crater outflows on Venus

Several emplacement mechanisms were proposed for the unique flow features associated with 402 of the 912 impact craters found on Venus to date. Studies based on rheological models and laboratory results have suggested two separate depositional flow mechanisms: a turbulent emplacement and a lava like emplacement. Schultz proposed a progressive transition from the turbulent to the lava like mechanism during deceleration of some turbulent flows. He suggested that these composite flows were emplaced prior to the deposition of the normal ejecta. After an examination of the geomorphologic, stratigraphic, and topographic relations of the flows associated with the 402 craters, it is suggested that most of the outflows result from a two-stage emplacement process. In the first stage, a turbulent, proximal part is usually emplaced downrange of the impact site after the other ejecta materials. In the second stage, a distal part, composed of low-viscosity melt, slowly drains via dendritic channels from the proximal deposit and flows like lava. A few flows were identified that appear to have been emplaced prior to the ejecta; these flows likely result from a different mechanism.

Chadwick, D. J.↗
NASA NTRS1993

Averaging techniques for steady and unsteady calculations of a transonic fan stage

It is often desirable to characterize a turbomachinery flow field with a few lumped parameters such as total pressure ratio or stage efficiency. Various averaging schemes may be used to compute these parameters. The momentum, energy, and area averaging schemes are described and compared. The schemes were compared for two computed solutions of the midspan section of a transonic fan stage: a steady averaging-plane solution in which average rotor outflow conditions were used as stator inflow conditions, and an unsteady rotor-stator interaction solution. The solutions were computed on identical grids using similar Navier-Stokes codes and an algebraic turbulence model. The unsteady solution is described, some unsteady flow phenomena are discussed, and the steady pressure distributions are compared. Despite large unsteady pressure fluctuations on the stator surface, the steady pressure distribution matched the average unsteady distribution almost exactly. Stator wake profiles, stator loss coefficient, and stage efficiency were computed for the two solutions with the three averaging schemes and are compared. In general, the energy averaging scheme gave good agreement between the averaging-plane solution and the time-averaged unsteady solution, even though certain phenomena due to unsteady wake migration were neglected.

Wyss, M. L.↗