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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 181 records · Page 10
All sourcesNASA NTRSDOE OSTI
NASA NTRS2000

Blade Surface Pressure Distributions in a Rocket Engine Turbine: Experimental Work With On-Blade Pressure Transducers

Understanding the unsteady aspects of turbine rotor flowfields is critical to successful future turbine designs. A technology program was conducted at NASA's Marshall Space Flight Center to increase the understanding of unsteady environments for rocket engine turbines. The experimental program involved instrumenting turbine rotor blades with surface-mounted high frequency response pressure transducers. The turbine model was then tested to measure the unsteady pressures on the rotor blades. The data obtained from the experimental program is unique in three respects. First, much more unsteady data was obtained (several minutes per set point) than has been possible in the past. Also, two independent unsteady data acquisition systems and fundamental signal processing approaches were used. Finally, an extensive steady performance database existed for the turbine model. This allowed an evaluation of the effect of the on-blade instrumentation on the turbine's performance. This unique data set, the lessons learned for acquiring this type of data, and the improvements made to the data analysis and prediction tools will contribute to future turbine programs such as those for reusable launch vehicles.

Hudson, Susan T.↗
NASA NTRS1987

Surface pressure measurements on the blade of an operating Mod-2 wind turbine with and without vortex generators

Pressure measurements covering a range of wind velocities were made at one span location on the surface of an operating Mod-2, 2500 kW, wind turbine blade. The data, which were taken with and without vortex generators installed on the leading edge, show the existence of higher pressure coefficients than would be expected from two-dimensional wind tunnel data. These high pressure ratios may be the result of three-dimensional flow over the blade, which delays flow separation. Data are presented showing the repetitiveness of abrupt changes in the pressure distribution that occur as the blade rotates. Calculated values of suction and flap coefficients are also presented.

Nyland, Ted W.↗
DOE OSTI2020

In Situ Studies of Methanol Decomposition Over Cu(111) and Cu2O/Cu(111): Effects of Reactant Pressure, Surface Morphology, and Hot Spots of Active Sites

The dissociative adsorption of methanol was investigated on Cu(111) and ultrathin Cu 2 O films. We employed synchrotron-based Ambient Pressure X-ray Photoelectron Spectroscopy (AP-XPS) and Scanning Tunneling Microscopy (STM) to study the dynamics of gas–solid interactions, and calculations based on Density Functional Theory (DFT) were used to examine the reaction path. C 1s XPS spectra revealed that methanol underwent dissociative adsorption on plain Cu(111) to form methoxy (CH 3 O), formaldehyde (H 2 CO), and formate (HCOO) at a pressure range of 0.5–10 mTorr, with these species remaining on the surface after evacuation. This was accompanied by the appearance of a low coverage (~0.05 ML) of O ads in the O 1s which can be considered a highly active site for methanol activation. The high activity is apparent by a coverage of 0.8 ML of methoxy at room temperature. STM was unable to image these species at room temperature as they were highly mobile on metallic copper. In contrast, for CH 3 OH on Cu 2 O/Cu(111), STM showed clear hot spots for reaction and a complex array of adsorption structures. On the oxide substrate, there was decomposition of methanol to H 2 CO, CH 3 O, HCOO, and hydrocarbon species (CH x ) due to the subsequent interactions of methanol with lattice oxygen. Cu(111) remained entirely saturated with decomposition products under 10 mTorr of methanol (θ ≈ 0.97 ML), whereas the Cu 2 O overlayer was saturated at a much lower coverage (θ ≈ 0.30 ML). STM revealed rows and step edges of Cu 2 O decorated with decomposition products and metallic Cu islands ~5 nm in size. The difference in activity between Cu(111) and Cu 2 O/Cu(111) is attributed to the significant amount of O present on the oxide surface. Additionally, Density Functional theory (DFT) calculations described the XPS measurements well, showing a likely methanol dissociation to *CH 3 O and therefore a surface reduction. More importantly, the DFT results revealed that it was the chemisorbed oxygen on Cu 2 O/Cu(111) which oxidized the dissociated *CH 3 O to *HCOO and eventually CO 2 , while the reaction only involving upper oxygen on the Cu 2 O hexagonal ring led to the formation of H 2 CO.

36 MATERIALS SCIENCE↗
NASA NTRS1983

Analysis of surface pressure distributions on two elliptic missile configurations

The state-of-the-art methods for predicting missile aerodynamic characteristics do not accurately predict the loads of missile configurations with bodies of elliptic cross section. An investigation of this problem found significant nonlinear flow disturbance on the windward surface of a 3:1 elliptic body at Mach 2.50 in addition to the nonlinear vortical flows which develop on the leeside. A nonlinear full-potential flow method (NCOREL) was found to provide extremely accurate pressure estimates for attached-flow conditions and the vortex prediction method contained in the state-of-the-art method (NOSEVTX) was shown to accurately calculate body vortices and leeside pressures.

Allen, J. M.↗
NASA NTRS2012

Measuring Global Surface Pressures on a Circulation Control Concept Using Pressure Sensitive Paint

This report will present the results obtained from the Pressure Sensitive Paint (PSP) technique on a circulation control concept model. This test was conducted at the National Transonic Facility (NTF) at the NASA Langley Research Center. PSP was collected on the upper wing surface while the facility was operating in cryogenic mode at 227 K (-50 oF). The test envelope for the PSP portion included Mach numbers from 0.7 to 0.8 with angle of attack varying between 0 and 8 degrees and a total pressure of approximately 168 kPa (24.4 psi), resulting in a chord Reynolds number of approximately 15 million. While the PSP results did exhibit high levels of noise in certain conditions (where the oxygen content of the flow was very small), some conditions provided good correlation between the PSP and pressure taps, showing the ability of the PSP technique. This work also served as a risk reduction opportunity for future testing in cryogenic conditions at the NTF.

Watkins, Anthony N.↗
NASA NTRS2010

Active Flow Control Strategies Using Surface Pressure Measurements

Evaluate the efficacy of Microjets Can we eliminate/minimize flow separation? Is the flow unsteadiness reduced? Guidelines for an active control Search for an appropriate sensor. Examine for means to develop a flow model for identifying the state of flow over the surface Guidelines toward future development of a Simple and Robust control methodology

Kumar, Vikas↗
NASA NTRS1980

A correlation method to predict the surface pressure distribution of an infinite plate or a body of revolution from which a jet is issuing

A correlation method to predict pressures induced on an infinite plate by a jet exhausting normal to the plate into a subsonic free stream was extended to jets exhausting at angles to the plate and to jets exhausting normal to the surface of a body revolution. The complete method consisted of an analytical method which models the blockage and entrainment properties of the jet and an empirical correlation which accounts for viscous effects. For the flat plate case, the method was applicable to jet velocity ratios up to ten, jet inclination angles up to 45 deg from the normal, and radial distances up to five diameters from the jet. For the body of revolution case, the method was applicable to a body at zero degrees angle of attack, jet velocity ratios 1.96 and 3.43, circumferential angles around the body up to 25 deg from the jet, axial distances up to seven diameters from the jet, and jet-to-body diameter ratios less than 0.1.

Perkins, S. C., Jr.↗
NASA NTRSDate not supplied

A Network of Surface Pressure Observations to Constrain Aerosol Forcing in Mars Climate Models

The evolving distribution of radiatively active dust and water ice clouds plays a major role in modulating the seasonal and interannual variation in the thermal forcing of the Martian atmosphere. Thermal tides are the global-scale atmospheric response to the diurnally varying thermal forcing due to aerosol heating within the atmosphere and radiative and convective heat transfer from the surface. The tide includes westward propagating (sun-synchronous) waves driven in response to solar heating, as well as nonmigrating waves that result from zonal variations in the thermotidal forcing caused by variations in topography and surface thermal properties and in the distribution of aerosols (dust and water ice clouds).

R. J. Wilson↗
NASA NTRS1976

Io's atmosphere and ionosphere - New limits on surface pressure from plasma models

The paper studies charge particle impact as a mechanism for the production of Io's ionosphere. Pioneer 10 thermal plasma measurements and magnetospheric plasma models which explain the observed spatial distribution of neutral hydrogen and sodium atoms in the vicinity of Jupiter's satellite Io imply electron fluxes of about 10 to the 10th/sq cm/s. The fluxes and the temperature (about 100 eV) of this plasma suggest that electron impact ionization is the dominant process in forming the ionosphere of Io. It is found that the surface number density of the neutral species required to match the observed electron density profiles is about 10 to the 9th/cu cm or less. This value is two orders of magnitude lower than previous estimates.

Johnson, T. V.↗
NASA NTRS1983

Surface pressures induced on a flat plate with in-line and side-by-side dual jet configurations

A jet in a crossflow is of interest in numerous practical situations including jet-powered VTOL aircraft. Two aspects of the problem have received little prior study. First is the effect of the angle of the jet to the crossflow. Second is the performance of dual-jet configurations both in-line and side-by-side. The test plan for this work was designed to address these two aspects. The experiments were conducted in the 7 x 10 tunnel at NASA Ames at velocities from 14.5 - 35.8 m/sec (47.6 - 117.4 ft/sec.). Detailed pressure distributions are presented for single and dual jets over a range of velocity ratios from 3 to 8, spacings from 2 to 6 diameters and injection angles of 90, 75, and 105 degrees. The effects of the various parameters and the differences between the axisymmetric and flat plate geometries on the nature, size, shape, and strength of the interaction regions on the body surfaces are shown.

Schetz, J. A.↗
NASA NTRS1961

Surface Pressures and Heat Transfer on Unswept Blunt Plates in Helium at High Mach Numbers

Pressure distributions and local convective heat-transfer coefficients on a flat plate at zero angle of attack were measured in helium. Data were obtained with various amounts of leading-edge bluntness at Mach numbers of 12.5 and 14.7. The pressures on a sharp leading-edged plate were not influenced by the leading edge and were predicted by the first-order, hypersonic, weak-interaction theory. Pressures on blunt plates were correlated by introducing the leading-edge Reynolds number as a parameter. Measured heat-transfer coefficients on the sharp plate agreed with predictions obtained form existing exact solutions for hear transfer across the laminar boundary layer. For the blunt plates a comparison of theory with experiment indicated that more knowledge of the flow field between the sock wave and plate surface is necessary before an adequate prediction of convective heat transfer can be made. Shock-wave shapes for the blun plates at a Mach number 12.5 and zero angle of attack were measured. At distances between 2 and 60 leading-edge thicknesses from the shock vertex, the shock-wave shapes were found to be represented by a modified form of the blast-wave analogy.

Marvin, Joseph G.↗
NASA NTRS1976

Cold-air annular-cascade investigation of aerodynamic performance of core-engine-cooled turbine vanes. 2: Pressure surface trailing edge ejection and split trailing edge ejection

The aerodynamic performance of two trailing edge ejection cooling configurations of a core-engine stator vane were experimentally determined in an ambient inlet-air full-annular cascade where three-dimensional effects could be obtained. The tests were conducted at the design mean-radius ideal aftermixed critical velocity ratio of 0.778. Overall vane aftermixed thermodynamic and primary efficiencies were obtained over a range of coolant flows to about 10 percent of the primary flow at a primary to coolant total temperature ratio of 1.0. The radial variation in efficiency and the circumferential and radial variations in vane-exit total pressure were determined. Comparisons are made with the solid (uncooled) vane.

Mclallin, K. L.↗
NASA NTRS1982

A comparison of computed Space Shuttle Orbiter surface pressures with flight measurements

Vehicles such as the Shuttle Orbiter operate over a wide range of angle of attack when entering the earth's atmosphere. This angle-of-attack range can be divided into two classes, a moderate regime, and a high regime for angles of attack greater than 30 deg. The HALIS (High Alpha Inviscid Solution) code was developed for computing flowfields in the high angle-of-attack regime. The present investigation is concerned with conducting a comparison of HALIS results with wind-tunnel data and the limited flight data from STS-1. The investigation shows that at high angle-of-attack, the axial flow over the entire windward surface can be subsonic, and, for those conditions, where the subsonic axial flow is confined to the nose of the vehicle, embedded regions of subsonic axial flow may be found along the vehicle strake tips.

Weilmuenster, K. J.↗
NASA NTRS1982

Experimental study of surface pressures induced on a flat plate and a body of revolution by various dual jet configurations

The effect of the angle of a jet to a crossflow, the performance of dual jet configurations, and a jet injected from a body of revolution as opposed to a flat plate were investigated during experiments conducted in the 7x10 tunnel at NASA Ames at Velocities from 14.5 m/sec to 35.8 m/sec (47.6 to 117.4 ft/sec.). Pressure distributions are presented for single and dual jets over a range of velocity ratios from 2 to 10, spacings from 2 to 6 diameters and injection angles of 90, 75, 60, and 105 degrees. For the body of revolution tests, the ratio of the jet to body diameters was set as large (1/2) in order to be more representative of V/STOL aircraft applications. Flat plate tests involved dual jets both aligned and in side by side configurations. The effects of the various parameters and the differences between the axisymmetric and planar body geometrics on the nature, size, shape, and strength of the interaction regions on the body surfaces are shown. Some flowfield measurements are also presented, and it is shown that a simple analysis is capable of predicting the trajectories of the jets.

Schetz, J. A.↗
DOE OSTI2024

Surface Pressure Fluctuations Induced by a Hypersonic Turbulent Boundary Layer on a Sharp Cone at Angle of Attack

High-fidelity simulations are performed to characterize the turbulence-induced wall pressure fluctuations on a sharp cone at a 5.5° angle-of-attack in a Mach 8 flow. Wall-resolved large-eddy simulation (LES) and wall-modeled large-eddy simulation (WMLES) results are compared to measurements at several locations on the cone body, where comparisons with high-frequency PCB sensors are good, while comparison with low-frequency kulite sensors varies depending on the location. For a given streamwise location, simulation results show significant azimuthal variation in the wall pressure fluctuation statistics. Comparisons between LES and WMLES results indicate that WMLES can accurately reproduce the low-frequency component of the autospectra quite well, while slight sensitivity is apparent in the coherence. A grid sensitivity study for WMLES further demonstrated sensitivity in the wall pressure fluctuation coherence, but not in the autospectra.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗