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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 1,009 records · Page 56
All sourcesNASA NTRSDOE OSTI
NASA NTRS1982

Evaluation of SRB phenolic TPS material made by an alternate vendor

Tests conducted to evaluate the adequacy of solid rocket booster (SRB) phenolic thermal protection system (TPS) material supplied by an alternate vendor chosen by United Space Boosters, Inc. (USBI), to replace the current phenolic TPS sections used thus far on the first four Shuttle flights. The phenolic TPS is applied mainly to the attach and kick rings of the solid rocket booster (SRB). Full-scale sectional models of both the attach and kick ring structure were made up with 0.0265 in. thick stainless steel thin skin covers with thermocouples on them to determine the heating rates. Such models were made up for both the forward and rear faces of the kick ring which has a different configuration on each side. The thin skins were replaced with the alternate phenolic TPS sections cut from flight hardware configuration phenolic parts as supplied by the new vendor. Two tests were performed for each configuration of the attach and kick rings and the samples were exposed to the flow for a duration that gave a heat load equivalent to that obtained in the series of runs made for the current line of phenolic TPS. The samples performed very well with no loss of any phenolic layers. The post-test samples looked better than those used to verify the current phenolic TPS.

Karu, Z. S.↗
NASA NTRS1984

Zero-g experiments with a He II active phase separator for space application

An active phase separator (APS) for temperature control of He II space cooling systems was tested in a zero-g environment during a series of parabolic flights on a NASA KC 135 aircraft. The APS provides for liquid-gas separation and features an annular gap, a downstream heat exchanger and an upstream ball closure. The apparatus was operated during acceleration and floating and in two different heat load situations. The tests confirmed that adequate mass flow rates could be maintained using a vacuum pump to simulate space vacuum and that residual liquid could be evaporated from the heat exchanger after closing a ball valve to seal off flows.

Denner, H. D.↗
NASA NTRS1985

Thermomechanical modeling of the Colorado Plateau-Basin and range transition zone

The Colorado Plateau (CP) basin and range (B & R) boundary is marked by a transition zone on the order of 75 to 150 km in width. As one moves westward across this transition from the CP interior to the B & R there is a variation in the surface topography, surface heat flow, Bouguer gravity, seismicity, and crustal structure. This transition extends eastward into the western CP from the Wastach-Hurricane fault line and is largely coincident with the high plateaus of Utah and the Wasatch Mountains. It has been suggested that this transition zone marks a thermal and tectonic encroachment of the CP by the B & R. A simple two dimensional numerical model of the thermal regime for the transition zone was constructed to test the hypothesis that the observed geophysical signatures across the transition are due to lateral heat conduction from steady state uniform extension within the B & R lithosphere. Surface heat flow, uplift due to flexure from thermal buoyant loading, and regional Bouguer gravity are computed for various extension rates, crustal structures, and compensation depths.

Londe, M. D.↗
NASA NTRS1989

High speed turboprop aeroacoustic study (single rotation). Volume 1: Model development

A frequency-domain noncompact-source theory for the steady loading and volume-displacement (thickness) noise of high speed propellers has been developed and programmed. Both near field and far field effects have been considered. The code utilizes blade surface pressure distributions obtained from three-dimensional nonlinear aerodynamic flow field analysis programs as input for evaluating the steady loading noise. Simplified mathematical models of the velocity fields induced at the propeller disk by nearby wing and fuselage surfaces and by angle-of-attack operation have been developed to provide estimates of the unsteady loading imposed on the propeller by these potential field type interactions. These unsteady blade loadings have been coupled to a chordwise compact propeller unsteady loading noise model to provide predictions of unsteady loading noise caused by these installation effects. Finally, an analysis to estimate the corrections to be applied to the free-field noise predictions in order to arrive at the measurable fuselage sound pressure levels has been formulated and programmed. This analysis considers the effects of fuselage surface reflection and diffraction together with surface boundary layer refraction. The steady loading and thickness model and the unsteady loading model have been verified using NASA-supplied data for the SR-2 and SR-3 model propfans. In addition, the steady loading and thickness model has been compared with data from the SR-6 model propfan. These theoretical models have been employed in the evaluation of the SR-7 powered Gulfstream aircraft in terms of noise characteristics at representative takeoff, cruise, and approach operating conditions. In all cases, agreement between theory and experiment is encouraging.

Whitfield, C. E.↗
NASA NTRS1991

Thin film heat flux sensor for Space Shuttle Main Engine turbine environment

The Space Shuttle Main Engine (SSME) turbine environment stresses engine components to their design limits and beyond. The extremely high temperatures and rapid temperature cycling can easily cause parts to fail if they are not properly designed. Thin film heat flux sensors can provide heat loading information with almost no disturbance of gas flows or of the blade. These sensors can provide steady state and transient heat flux information. A thin film heat flux sensor is described which makes it easier to measure small temperature differences across very thin insulating layers.

Will, Herbert↗
NASA NTRS1954

Comparison of Performance of Experimental and Conventional Cage Designs and Materials for 75-millimeter-bore Cylindrical Roller Bearings at High Speed

The results of two investigations, one to determine the relative merits of four experimental and two conventional design 75-millimeter-bore (size 215) cylindrical roller bearings and one to determine the relative merits of nodular iron and bronze as cage materials for this size and type of bearing, are presented in this report. Nine test bearings were operated over a range of dn values (product of bearing bore in mm and shaft speed in r.p.m) from 0.3 x 10(6) to 2.3 x 20(6), radial loads for 7 to 1613 pounds, and oil flows from 2 to 8 pounds per minute with a single-jet circulatory oil feed. Of the six bearings used to evaluate designs, four were experimental types with outer-race-riding cages and inner-race-guided rollers, and two were conventional types, one with outer-race-guided rollers and cage and one with inner-race-guided rollers and cage. Each of these six test bearings was equipped with a different design cage made of nodular iron. The experimental combination of an outer-race-riding cage with a straight-through outer race and inner-race-guided rollers was found to give the best over-all performance based on limiting dn values and bearing temperatures.

Anderson, William J↗
NASA NTRS1996

Pioneer Venus Data Analysis

Analysis and interpretation of data from the Orbiter Retarding Potential Analyzer (ORPA) onboard the Pioneer Venus Orbiter is reported. By comparing ORPA data to proton data from the Orbiter Plasma Analyzer (OPA), it was found that the ORPA suprathermal electron densities taken outside the Venusian ionopause represent solar wind electron densities, thus allowing the high resolution study of Venus bow shocks using both magnetic field and solar wind electron data. A preliminary analysis of 366 bow shock penetrations was completed using the solar wind electron data as determined from ORPA suprathermal electron densities and temperatures, resulting in an estimate of the extent to which mass loading pickup of O+ (UV ionized O atoms flowing out of the Venus atmosphere) upstream of the Venus obstacle occurred. The pickup of O+ averaged 9.95%, ranging from 0.78% to 23.63%. Detailed results are reported in two attached theses: (1) Comparison of ORPA Suprathermal Electron and OPA Solar Wind Proton Data from the Pioneer Venus Orbiter and (2) Pioneer Venus Orbiter Retarding Potential Analyzer Observations of the Electron Component of the Solar Wind, and of the Venus Bow Shock and Magnetosheath.

Jones, Douglas E.↗
NASA NTRS1996

SCISEAL: A CFD Code for Analysis of Fluid Dynamic Forces in Seals

A 3D CFD code, SCISEAL, has been developed and validated. Its capabilities include cylindrical seals, and it is employed on labyrinth seals, rim seals, and disc cavities. State-of-the-art numerical methods include colocated grids, high-order differencing, and turbulence models which account for wall roughness. SCISEAL computes efficient solutions for complicated flow geometries and seal-specific capabilities (rotor loads, torques, etc.).

Althavale, Mahesh M.↗
NASA NTRS1959

Investigation of the Effects of Low Reynolds Number Operation on the Performance of a Single-Stage Turbine with a Downstream Stator

High-altitude turbojet performance is adversely affected by the effects of low air density. This performance loss is evaluated as a Reynolds number effect, which represents the increased significance of high fluid viscous forces in relation to dynamic fluid forces as the Reynolds number is decreased. An analytical and experimental investigation of the effects of low Reynolds number operation on a single-stage, high-work-output turbine with a downstream stator was carried out at Reynolds numbers of 182,500, 39,600, and 23,000, based on average rotor-design flow conditions. At low Reynolds numbers and turbulent flow conditions, increased viscous losses caused decreased effective flow area, and thus decreased weight flow, torque, and over-all efficiency at a given equivalent speed and pressure ratio. Decreasing the Reynolds number from 182,500 to 23,000 at design equivalent speed resulted in a 5.00-point loss in peak over-all turbine efficiency for both theory and experiment. The choking equivalent weight flow decreased 2.30 percent for these conditions. Limiting loading work output was reached at design equivalent speed for all three Reynolds numbers. The value of limiting loading work output at design speed decreased 4.00 percent as Reynolds number was decreased from 182,500 to 23,000. A theoretical performance-prediction method using basic boundary-layer relations gave good agreement with experimental results over most of the performance range at a given Reynolds number if the experimental and analytical design operating conditions were carefully matched at the highest Reynolds number with regard to design performance parameters. High viscous losses in the inlet stator and rotor prevented the attainment of design equivalent work output at the lowest Reynolds number of 23,000.

Forrette, Robert E.↗
NASA NTRS2000

The SR-71 Test Bed Aircraft: A Facility for High-Speed Flight Research

The SR-71 test bed aircraft is shown to be a unique platform to flight-test large experiments to supersonic Mach numbers. The test bed hardware mounted on the SR-71 upper fuselage is described. This test bed hardware is composed of a fairing structure called the "canoe" and a large "reflection plane" flat plate for mounting experiments. Total experiment weights, including the canoe and reflection plane, as heavy as 14,500 lb can be mounted on the aircraft and flight-tested to speeds as fast as Mach 3.2 and altitudes as high as 80,000 ft. A brief description of the SR-71 aircraft is given, including details of the structural modifications to the fuselage, modifications to the J58 engines to provide increased thrust, and the addition of a research instrumentation system. Information is presented based on flight data that describes the SR-71 test bed aerodynamics, stability and control, structural and thermal loads, the canoe internal environment, and reflection plane flow quality. Guidelines for designing SR-71 test bed experiments are also provided.

Corda, Stephen↗
NASA NTRS1995

Can Satellite Geodesy Disentangle Holocene Rebound and Present-Day Glacier Balance Signatures?

The secular drift of the precession of the ascending node of the LAGOES -1 satellite is apparently linked to the Earth s paleoclimate through the slow viscous response of the mantle to ice sheet/ocean mass transfer during the last great continental deglaciation . The secular node acceleration is particularly sensitive to the longest wavelengths of the paleo -surface loading that have been memorized by the mantle glacio -isostatic flow. Tide gauge records for the last 130 years show a post-glacial rebound-corrected sea-level rise of 2.4 n 0.9 mm yr-1.

glacio-isostatic flow tide gauge records post-glac↗
NASA NTRS2011

Cartesian Off-Body Grid Adaption for Viscous Time- Accurate Flow Simulation

An improved solution adaption capability has been implemented in the OVERFLOW overset grid CFD code. Building on the Cartesian off-body approach inherent in OVERFLOW and the original adaptive refinement method developed by Meakin, the new scheme provides for automated creation of multiple levels of finer Cartesian grids. Refinement can be based on the undivided second-difference of the flow solution variables, or on a specific flow quantity such as vorticity. Coupled with load-balancing and an inmemory solution interpolation procedure, the adaption process provides very good performance for time-accurate simulations on parallel compute platforms. A method of using refined, thin body-fitted grids combined with adaption in the off-body grids is presented, which maximizes the part of the domain subject to adaption. Two- and three-dimensional examples are used to illustrate the effectiveness and performance of the adaption scheme.

Buning, Pieter G.↗
NASA NTRS2013

Interior Noise Predictions in the Preliminary Design of the Large Civil Tiltrotor (LCTR2)

A prediction scheme was established to compute sound pressure levels in the interior of a simplified cabin model of the second generation Large Civil Tiltrotor (LCTR2) during cruise conditions, while being excited by turbulent boundary layer flow over the fuselage, or by tiltrotor blade loading and thickness noise. Finite element models of the cabin structure, interior acoustic space, and acoustically absorbent (poro-elastic) materials in the fuselage were generated and combined into a coupled structural-acoustic model. Fluctuating power spectral densities were computed according to the Efimtsov turbulent boundary layer excitation model. Noise associated with the tiltrotor blades was predicted in the time domain as fluctuating surface pressures and converted to power spectral densities at the fuselage skin finite element nodes. A hybrid finite element (FE) approach was used to compute the low frequency acoustic cabin response over the frequency range 6-141 Hz with a 1 Hz bandwidth, and the Statistical Energy Analysis (SEA) approach was used to predict the interior noise for the 125-8000 Hz one-third octave bands.

Grosveld, Ferdinand W.↗
NASA NTRS1959

Externally Pressurized Journal Gas Bearings

Externally pressurized gas-lubricated bearings with multiple orifice feed are investigated. An analytical treatment is developed for a semi-cylindrical bearing with 9 orifices and for a cylindrical journal bearing with 192 radial and 24 axial orifices. Experiments are described on models of the two bearing configurations with specially designed fixtures which incorporate pneumatic loading and means for determining pressure profiles, gas flow and gap height. The correlation between theory and experiment is satisfactory.

Laub, John H.↗
NASA NTRS2020

Aerothermodynamics Technical Working Group: 2008 Turbomachinery Technology Assessment and Recommendations

This report documents the 2008 Turbomachinery Technology Assessment and Recommendations of the NASA-led Aerothermodynamics Technical Working Group (TWG). It includes technology review, assessment, and recommendation for future research and development. The areas covered are summarized as follows. Inlet Flow Distortion Sensitivity and Stability, Tip Leakage Flows in High-Pressure Cores, Endwall Contouring, Turbine Tip Flows, Combustor and Cooled-Turbine Interaction, Highly Loaded Low-Pressure Turbines.

Heidmann, James D.↗
DOE OSTI2023

An Efficient Three-Dimensional CFD-Based Numerical Wave Tank for a Wave Energy Converter in Extreme Irregular Waves: Preprint

A numerical wave tank approach for computational fluid dynamics (CFD) modelling of an extreme irregular seastate is presented. The technique couples a potential flow solution with a CFD solver for more efficient numerical predictions. This method has recently become attractive both for the research community and the industry working with offshore structures. The model is used to determine the response of a submerged pressure differential wave energy converter (WEC) in a fully nonlinear irregular wave condition using the high fidelity CFD code, STAR-CCM+. Potential flow based numerical models are commonly used to predict motions and performance of wave energy converters. Wave kinematics can deviate from potential flow predictions for extreme wave conditions; the excitation loads on an absorber can also be increasingly influenced by viscous effects, not captured in engineering level models. In these extreme conditions, a Reynolds-averaged Navier-Stokes CFD model can better predict motions and loads for a WEC. Long time series with varying random seed numbers can be used to identify singular extreme wave events from a stochastic irregular sea state. This approach simulates a more realistic wave series for a given sea state than a regular wave or a focused wave. However, it is computationally infeasible to run these long time series for three-dimensional (3D) CFD simulations. In this work, two-dimensional (2D) CFD simulations with a long domain allow the full development of an extreme nonlinear wave condition. The results are used to identify extreme events from a 50-year storm condition for the PacWave site off the coast of Oregon. A relatively short time window including this extreme event is then mapped to a 3D simulation using a user defined wave methodology. Convergence studies for domain length, wave forcing lengths, and time before the extreme event were conducted.

cfd↗