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At least 271 records · Page 15

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NASA NTRS1982

Energy efficient engine high-pressure turbine detailed design report

The energy efficient engine high-pressure turbine is a single stage system based on technology advancements in the areas of aerodynamics, structures and materials to achieve high performance, low operating economics and durability commensurate with commercial service requirements. Low loss performance features combined with a low through-flow velocity approach results in a predicted efficiency of 88.8 for a flight propulsion system. Turbine airfoil durability goals are achieved through the use of advanced high-strength and high-temperature capability single crystal materials and effective cooling management. Overall, this design reflects a considerable extension in turbine technology that is applicable to future, energy efficient gas-turbine engines.

Thulin, R. D.↗

NASA NTRS1983

Vertical ascending electrophoresis of cells with a minimal stabilizing medium

Vertical fractionation of a mixture of fixed horse and human red blood cells layered over a stabilizing support medium was done to give a valid comparison with proposed space experiments. In particular, the effects of sample thickness and concentration on zone migration rate were investigated. Electrophoretic mobilities of horse and human cells calculated from zone migration rates were compatible with those obtained by microelectrophoresis. Complete cell separation was observed when low power and effective cooling were employed.

Omenyi, S. N.↗

NASA NTRS1984

Heat transfer and turbulence measurements of a film-cooled flow over a convexly curved surface

Heat transfer and hydrodynamic boundary layer measurements were made in a turbulent boundary layer on a convex surface with 13 rows of injection. Both full- and partial-coverage cases were tested for three blowing ratios: 0.2, 0.4, and 0.6. Heat transfer results are discussed in terms of Stanton number with injection air temperature equal to wall temperature. In the blown region, for both m (blowing ratio) = 0.2 and 0.4, the local response of the boundary layer is dominated by curvature, and m = 0.4 shows higher cooling effects than m = 0.2 or 0.6, as expected, based on flat-plate results. Hydrodynamic measurements with a triple-hot-wire suggest the existence of two streamwise lanes. Lanes containing injection holes are highly affected by injection and show a definite streamwise evolution. Lanes which do not contain holes are not affected much by injection and show little change in the streamwise direction.

Furuhama, K.↗

NASA NTRS1985

Film cooling on a convex wall: Heat transfer and hydrodynamic measurements for full and partial coverage

Turbine-blade cooling is an important issue for high-efficiency turbine engines, and discrete-hole injection is widely used as a cooling method. In the present study, detailed measurements were made of the heat transfer and hydrodynamics of a film-cooled flow on a convex wall, both for full and partial coverage. Two important parameters were altered: the blowing ratio, m, and the number of rows of injection holes. Three values of m were tested: m = 0.2, 0.4, and 0.6. In the blown region, m = 0.4 results in the lowest Stanton numbers of the three blowing ratios tested. This indicates that the value of m = 0.4 is near optimum on the convex wall from the point of view of cooling effect by injection. In the recovery region, Stanton numbers gradually approach the no injection values. Although the heat-transfer behavior during recovery from injection looks relatively complicated, the behavior of Stanton number can be explained in terms of two mechanisms: recovery from the thermal effect of injection and recovery from the turbulence augmentation. This interpretation of the data is supported by the hydrodynamic and temperture-profile measurements. For partial blowing cases, the data follow the full-coverage values inside the blown region. In the unblown region, both in the curved and in the flat plate, the effect of the number of blown rows is clearly seen. Hydrodynamic boundary-layer profiles were measured with the aid of a triple hot-water probe. Three mean-velocity components and six turbulence quantities were simultaneously measured, and inside the blown region strong three-dimensionality was observed.

Furuhama, K.↗

NASA NTRS1985

An experimental data base for material selection and design of high-speed, high-pressure, oxygen turbomachinery

New technologies for space-based, reusable, throttleable, cryogenic, orbit transfer propulsion are being evaluated. A variable-thrust (200 to 3000 lbF), 2000 psi chamber pressure, LO2/LH2 engine has been selected to demonstrate the 20-hour, 500-restart life goal, and a specific impulse of 480 lbF-sec/lbM. The advanced design uses warm oxygen to power a fully integrated turbopump that delivers 4500 psi LO2. The selected engine cycle provides the following advantages over conventional expander cycle designs which use H2 to drive the LH2 and LO2 pumps; higher engine operating pressures and performance in a smaller envelope, lower turbine operating temperatures, elimination of interpropellant seals and purges, and an extended throttling range. The design approach and results of testing to characterize materials for use in high-pressure gaseous oxygen are discussed. Test methods include particle impact testing in a sonic-flow, hot GO2 streams and forced, high-speed friction rubbing testing. Materials are exposed to oxygen and nitrogen atmospheres at pressures of 100, 1000, and 3000 psi to identify separately the gas cooling effects from the metal oxidation effects at the rubbing surface. The selection of candidate design materials is based on an analytical parameter defined as the burn factor. Typical materials tested include carbon steel, stainless steel, nickel, copper, and monel alloys.

Schoenman, L.↗

NASA NTRS1986

Venus mesosphere and thermosphere. I - Heat budget and thermal structure

The calculation of a reasonable global average temperature structure is the first step in the simulation of the dynamics and observed characteristics of Venus's upper mesosphere and thermosphere. Various physical processes that influence Venus temperatures are examined, using updated inputs and new parameterizations. It is demonstrated, using a one-dimensional NLTE radiative transfer code, that temperatures observed during the Pioneer Venus mission can be reproduced using an O-CO2 collisional excitation rate coefficient of 4 x 10 to the -13th cu cm/s for strong 15-micron cooling, balanced by 9.5 percent-efficient EUV heating. Cooling by eddy mixing is at best a minor contribution to the total cooling required. Exospheric temperatures are calculated to vary by 60 K or less over a solar cycle, in rough agreement with observations. It is concluded that CO2 cooling effectively buffers against such solar perturbations, due to its nonlinear temperature dependence.

Dickinson, R. E.↗

NASA NTRS1987

Nonlinear heat transfer and structural analyses of SSME turbine blades

Three-dimensional nonlinear finite-element heat transfer and structural analyses were performed for the first stage high-pressure fuel turbopump blade of the space shuttle main engine (SSME). Directionally solidified (DS) MAR-M 246 material properties were considered for the analyses. Analytical conditions were based on a typical test stand engine cycle. Blade temperature and stress-strain histories were calculated using MARC finite-element computer code. The study was undertaken to assess the structural response of an SSME turbine blade and to gain greater understanding of blade damage mechanisms, convective cooling effects, and the thermal-mechanical effects.

Abdul-Aziz, A.↗

NASA NTRS1987

Hydrogen scramjet with sidewall injection - Shock tunnel simulations

A free-piston shock tunnel has been used to obtain test data on a scramjet combustion chamber with sidewall injection. The results obtained indicate that combustion was strongly influenced by a region of fuel whose temperature was held below its ignition temperature by wall-cooling effects; this increased the fraction of unburned fuel and resulted in a significant loss of specific impulse. Aerodynamic heating would keep the walls above hydrogen ignition temperature in an actual scramjet powerplant, however. Maximum specific impulse was obtained with a combination of parallel and transverse injection in a long combustion chamber, followed by a dual stage expansion.

Morgan, R. G.↗

NASA NTRS1988

Thermal-structural analyses of Space Shuttle Main Engine (SSME) hot section components

Three dimensional nonlinear finite element heat transfer and structural analyses were performed for the first stage high pressure fuel turbopump (HPFTP) blade of the space shuttle main engine (SSME). Directionally solidified (DS) MAR-M 246 and single crystal (SC) PWA-1480 material properties were used for the analyses. Analytical conditions were based on a typical test stand engine cycle. Blade temperature and stress strain histories were calculated by using the MARC finite element computer code. The structural response of an SSME turbine blade was assessed and a greater understanding of blade damage mechanisms, convective cooling effects, and thermal mechanical effects was gained.

Abdul-Aziz, Ali↗

NASA NTRS1988

Aerodynamic flow quality and acoustic characteristics of the 40- by 80-foot test section circuit of the National Full-Scale Aerodynamic Complex

The 40- by 80-foot wind tunnel circuit of the National Full-Scale Aerodynamic Complex (NFAC) has recently undergone major modifications and subsequently completed final acceptance testing. The initial testing and calibration of the wind tunnel are described and in many cases these results are compared with predictions derived from model tests and theoretical analyses. The wind tunnel meets or exceeds essentially all performance objectives. The facility runs smoothly and routinely at its maximum test-section velocity of 300 knots (Mach number = 0.45). An effective cooling air exchange system enables the wind tunnel to operate indefinitely at this maximum power condition. Throughout the operating envelope of the wind tunnel the test-section dynamic pressure is uniform to within + or - 0.5 deg, and the axial component of turbulence is generally less than 0.5 percent. Acoustic measurements indicate that, due to the low noise fans and acoustic treatment in the wind-tunnel circuit and test section, the background noise level in the test section is comparable to other large-scale acoustic wind tunnels in the United States and abroad.

Olson, Lawrence E.↗

NASA NTRS1988

Do volcanic eruptions affect climate? Sulfur gases may cause cooling

The relationship between volcanic eruptions on earth and the observed climatic changes is investigated. The results of the comparison and analyses of volcanologic and climatologic data sets for the years between 1880 and 1980 indicate that changes in temperature caused by even of the largest eruptions recorded during this time were about the same as normal variations in temperature. However, when temperature records for several months or years preceding and following a given eruption were analyzed, a statistically significant temperature decrease of 0.2-0.5 C was found for the periods of one to two years immediately following some of the 19th and 20th century explosive events that prodiced large aerosol clouds (e.g., Krakatau and Agung eruptions). It is suggested that the content of sulfur in the erupted magma determines the size of aerosol cloud producing the cooling effect.

Self, Stephen↗

NASA NTRS1990

External Peltier Cooler For Low-Noise Amplifier

Inexpensive Peltier-effect cooling module made of few commercially available parts used to reduce thermal noise in microwave amplifier. Retrofitted to almost any microwave low-noise amplifier or receiver preamplifier used in communication, telemetry, or radar. Includes copper or aluminum cold plate held tightly against unit to be cooled by strap-type worm-gear clamps.

Soper, Terry A.↗

NASA NTRS1989

Quantitative NDE applied to composites and metals

Research at the NASA/Langley Research Center concerning quantitative NDE of composites and metals is reviewed. The relationship between ultrasonics and polymer cure is outlined. NDE models are presented, which can be used to develop measurement technologies for characterizing the curing of a polymer system for composite materials. The models can be used to determine the glass transition temperature, the degree of cure, and the cure rate. The application of the model to control autoclave processing of composite materials is noted. Consideration is given to the use of thermal diffusion models combined with controlled thermal input measurements to determine the thermal diffusivity of materials. Also, a two-dimensional physical model is described that permits delaminations in samples of Space Shuttle Solid Rocket Motors to be detected in thermograms in the presence of cooling effects and uneven heating.

Heyman, Joseph S.↗

NASA NTRS1992

Simulations of surface winds at the Viking Lander sites using a one-level model

The one-level model developed by Mass and Dempsey for use in predicting surface flows in regions of complex terrain was adapted to simulate surface flows at the Viking lander sites on Mars. In the one-level model, prediction equations for surface winds and temperatures are formulated and solved. Surface temperatures change with time in response to diabatic heating, horizontal advection, adiabatic heating and cooling effects, and horizontal diffusion. Surface winds can change in response to horizontal advection, pressure gradient forces, Coriolis forces, surface drag, and horizontal diffusion. Surface pressures are determined by integration of the hydrostatic equation from the surface to some reference level. The model has successfully simulated surface flows under a variety of conditions in complex-terrain regions on Earth.

Bridger, Alison F. C.↗

NASA NTRS1991

Hybrid approach to data reduction for multi-sensor hot wires

A hybrid approach to implementing the calibration equations for a multisensor hot-wire probe is discussed. The approach combines some of the speed of a look-up approach with the moderate storage requirements of direct calculation based on functional fitting. Particular attention is given to timing and storage comparisons for an X-wire probe. The method depends on the oft-employed concept of an effective cooling velocity which is a function only of the bridge output voltage.

Hooper, C. L.↗

NASA NTRS1990

Analysis of radiation parameters derived from the multisatellite Earth Radiation Budget Experiment

To quantify the diurnal radiative heating and cooling cycles of the earth and the atmosphere, data from instruments on the Earth Radiation Budget Satellite (ERBS) spacecraft and NOAA-9 satellites obtained from February 1985 through January 1986 were used to investigate longwave (LW) and shortwave (SW) flux as well as albedo for each month of the year. Seasonal variations of radiative parameters and their diurnal cycles are examined for the deserts, vegetated land, and oceans over the globe. The results show significant seasonal variations in both the outgoing LW and the absorbed SW flux, and a pronounced difference was found between oceanic and continental surfaces. Over much of the globe, LW warming is balanced by SW cooling, and clouds have a net cooling effect on the earth. Many areas of the earth were found to exhibit significant diurnal variations in both the LW flux and albedo.

Gibson, G. G.↗

NASA NTRS1923

Experiments with a built-in or fuselage radiator

The experiments discussed here were performed to determine whether radiators having similar cooling properties offer less resistance when incorporated into the fuselage, than when the hitherto customary arrangement is employed, with the radiator in the free air current more or less independent of the fuselage. The experiments indicated that the quantity of air flowing through the radiator is greatest when the fuselage and the radiator are separate. However, separate radiators cause more air resistance. When the radiator is incorporated into the fuselage, it is only possible to obtain a quantity equal to that which flows through the radiator in the free air current if the lateral outlet vents are widened or the quantity of air in increased by some special means, such as fans. Whether it is possible, in practice, to obtain the necessary cooling effect in this way, together with reduced resistance of the fuselage, is not decided here, since it is a question of construction.

Wiesselsberger, C↗

NASA NTRS1990

Digital control of magnetic bearings in a cryogenic cooler

This paper describes the design of a digital control system for control of magnetic bearings used in a spaceborne cryogenic cooler. The cooler was developed by Philips Laboratories for the NASA Goddard Space Flight Center. Six magnetic bearing assemblies are used to levitate the piston, displacer, and counter-balance of the cooler. The piston and displacer are driven by linear motors in accordance with Stirling cycle thermodynamic principles to produce the desired cooling effect. The counter-balance is driven by a third linear motor to cancel motion induced forces that would otherwise be transmitted to the spacecraft. An analog control system is currently used for bearing control. The purpose of this project is to investigate the possibilities for improved performance using digital control. Areas for potential improvement include transient and steady state control characteristics, robustness, reliability, adaptability, alternate control modes, size, weight, and cost. The present control system is targeted for the Intel 80196 microcontroller family. The eventual introduction of application specific integrated circuit (ASIC) technology to this problem may produce a unique and elegant solution both here and in related industrial problems.

Feeley, J.↗