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At least 271 records · Page 15

All sources NASA NTRS DOE OSTI

NASA NTRS1985

Unsteady pressure measurements on a biconvex airfoil in a transonic oscillating cascade

Flush-mounted dynamic pressure transducers were installed on the center airfoil of a transonic oscillating cascade to measure the unsteady aerodynamic response as nine airfroils were simultaneously driven to provide 1.2 deg of pitching motion about the midchord. Initial tests were performed at an incidence and angle of 0 deg and A Mach number of 0.65 in order to obtain results in a shock-free compressible flowfield. Subsequent tests were performed at an incidence angle of 7 deg and Mach number of 0.8 in order to observe the surface pressures with an oscillating shock near the leading edge of the airfoil. Results are presented for interblade phase angles of 90 and -90 deg and at blade oscillatory frequencies of 200 and 500 Hz (semi-chord reduced frequencies up to about 0.5 at a Mach number of 0.8). Results from the zero-incidence cascade are compared with a classical unsteady flat-plate analysis. Flow visualization results depicting the shock motion on the airfoils in the high-incidence cascade are discussed. The airfoil pressure data are tabulated.

Shaw, L. M.↗

NASA NTRS1986

Unsteady pressure measurements on a biconvex airfoil in a transonic oscillating cascade

Flush-mounted dynamic pressure transducers were installed on the center airfoil of a transonic oscillating cascade to measure the unsteady aerodynamic response as nine airfols were simultaneously driven to provide 1.2 deg of pitching motion about the midchord. Initial tests were performed at an incidence and angle of 0 deg and A Mach number of 0.65 in order to obtain results in a shock-free compressible flowfield. Subsequent tests were performed at an incidence angle of 7 deg and Mach number of 0.8 in order to observe the surface pressures with an oscillating shock near the leading edge of the airfoil. Results are presented for interblade phase angles of 90 and -90 deg and at blade oscillatory frequencies of 200 and 500 Hz (semi-chord reduced frequencies up to about 0.5 at a Mach number of 0.8). Results from the zero-incidence cascade are compared with a clasical usnteady flat-plate analysis. Flow visualization results depicting the shock motion on the airfoils in the high-incidence cascade are discussed. The airfoil pressure data are tabulated.

Shaw, L. M.↗

NASA NTRS1991

Heat transfer and pressure measurements for the SSME fuel turbine

A measurement program is underway using the Rocketdyne two-stage Space Shuttle Main Engine (SSME) fuel turbine. The measurements use a very large shock tunnel to produce a short-duration source of heated and pressurized gas which is subsequently passed through the turbine. Within this environment, the turbine is operated at the design values of flow function, stage pressure ratio, stage temperature ratio, and corrected speed. The first stage vane row and the first stage blade row are instrumented in both the spanwise and chordwise directions with pressure transducers and heat flux gages. The specific measurements to be taken include time averaged surface pressure and heat flux distributions on the vane and blade, flow passage static pressure, flow passage total pressure and total temperature distributions, and phase resolved surface pressure and heat flux on the blade.

Dunn, Michael G.↗

NASA NTRS1976

Force and pressure measurements on an airfoil oscillating through stall

Details of force, moment, and pressure distributions on a two-dimensional, 4-ft chord, NACA 0012 airfoil, oscillating in pitch through stall, in a 7 ft x 10 ft low-speed wind tunnel are presented. Tests were run with the airfoil in a closed test section and also in a test section having four longitudinal slots in each sidewall set to provide minimum tunnel interference on the wing in steady flow. In steady flow, differences between the results for the closed and 2% open case are small. The dynamic stall process is not triggered by the bursting of a laminar separation bubble but rather by the separation of the turbulent boundary layer downstream of the bubble.

Parker, A. G.↗

NASA NTRS1951

Characteristics of a wedge with various holder configurations for static-pressure measurements in subsonic gas streams

The characteristics of a wedge static-pressure sensing element with various holder configurations were determined and compared with the characteristics of the conventional tube. The probes were tested over a range of Mach number from 0.3 to 0.95 and at various pitch and yaw angles. The investigation showed that the spike-mounted wedge sensing element has a pressure coefficient comparable with the conventional subsonic static-pressure probe and the pressure coefficient of the wedge varied less than that of the conventional probe for corresponding change of yaw angle.

Gettelman, Clarence C↗

NASA NTRS2001

Pressure Probe Designs for Dynamic Pressure Measurements in a Supersonic Flow Field

A series of dynamic flow field pressure probes were developed for use in large-scale supersonic wind tunnels at NASA Glenn Research Center. These flow field probes include pitot, static, and five-hole conical pressure probes that are capable of capturing fast acting flow field pressure transients that occur on a millisecond time scale. The pitot and static probes can be used to determine local Mach number time histories during a transient event. The five-hole conical pressure probes are used primarily to determine local flow angularity, but can also determine local Mach number. These probes were designed, developed, and tested at the NASA Glenn Research Center. They were also used in a NASA Glenn 10- by 10-Foot Supersonic Wind Tunnel (SWT) test program where they successfully acquired flow field pressure data in the vicinity of a propulsion system during an engine compressor stall and inlet unstart transient event. Details of the design, development, and subsequent use of these probes are discussed in this report.

Porro, A. Robert↗

NASA NTRS1994

Pressure measurements of a three wave journal air bearing

In order to validate theoretical predictions of a wave journal bearing concept, a bench test rig was assembled at NASA Lewis Research Center to measure the steady-state performance of a journal air bearing. The tester can run up to 30,000 RPM and the spindle has a run out of less than 1 micron. A three wave journal bearing (50 mm diameter and 58 mm length) has been machined at NASA Lewis. The pressures at 16 ports along the bearing circumference at the middle of the bearing length were measured and compared to the theoretical prediction. The bearing ran at speeds up to 15,000 RPM and certain loads. Good agreement was found between the measured and calculated pressures.

Dimofte, Florin↗

NASA NTRS1999

Noninvasive Intracranial Volume and Pressure Measurements Using Ultrasound (Head and Spinal)

Prevention of secondary brain injuries following head trauma can be accomplished most easily when intracranial pressure (ICP) is monitored. However, current measurement techniques are invasive and thus not practical in the combat environment. The Pulsed Phase Lock Loop device, which was developed and patented by consultants Drs. Yost and Cantrell, uses a unique, noninvasive ultrasonic phase comparison method to measure slight changes in cranial volume which occur with changes in ICP. Year two studies included whole body head-up and head-down tilting effects on intracranial compliance and pressure in six healthy volunteers.

Hargens, Alan R.↗

NASA NTRS2001

Vibration Sensitivity of a Wide-Temperature Electronically Scanned Pressure Measurement (ESP) Module

A vibration sensitivity test was conducted on a Wide-Temperature ESP module. The test object was Module "M4," a 16-channel, 4 psi unit scheduled for installation in the Arc Sector of NTF. The module was installed on a vibration exciter and loaded to positive then negative full-scale pressures (+/-2.5 psid). Test variables were the following: Vibration frequencies: 20, 55, 75 Hz. Vibration level: 1 g. Vibration axes: X, Y, Z. The pressure response was measured on each channel, first without and then with the vibration turned on, and the difference analyzed by means of the statistical t-test. The results show that the vibration sensitivity does not exceed 0.01% Full Scale Output per g (with the exception of one channel on one axis) to a 95 percent confidence level. This specification, limited by the resolution of the pressure source, lies well below the total uncertainty specification of 0.1 percent Full Scale Output.

Zuckerwar, Allan J.↗

NASA NTRS1999

Pressure Measurements Using an Airborne Differential Absorption Lidar: Analysis of the Systematic Error Sources - Part 1

Remote airborne measurements of the vertical and horizontal structure of the atmospheric pressure field in the lower troposphere are made with an oxygen differential absorption lidar (DIAL). A detailed analysis of this measurement technique is provided which includes corrections for imprecise knowledge of the detector background level, the oxygen absorption fine parameters, and variations in the laser output energy. In addition, we analyze other possible sources of systematic errors including spectral effects related to aerosol and molecular scattering interference by rotational Raman scattering and interference by isotopic oxygen fines.

Flamant, Cyrille N.↗

DOE OSTI2022

Vapor detection and vapor pressure measurements of fentanyl and fentanyl hydrochloride salt at ambient temperatures

There is a need for non-contact, real-time vapor detection of drugs to combat illicit transportation and help curb the opioid epidemic. The low-volatility of drugs, like fentanyl, makes room temperature vapor detection of illicit drugs challenging, but feasible by atmospheric flow tube-mass spectrometry (AFT-MS). AFT-MS is a non-contact vapor detection approach capable of ultra-trace detection of drugs, including fentanyl and its analogs at low parts-per-quadrillion (ppqv) levels. The determination of vapor pressure values of fentanyl is necessary to understand potential vapor concentrations that may be available for detection. In this paper, vapor pressures of fentanyl free base and fentanyl hydrochloride salt (a common form of the illicit drug) were measured as a function of temperature at or near ambient conditions using the transpiration (gas saturation) method and AFT-MS. Based on our measurements, the vapor pressure of fentanyl at 25 °C is 9.0 × 10-14 atm (90 ppqv), and the vapor pressure of fentanyl hydrochloride at 25 °C is 1.8 x 10-17 atm (0.018 ppqv). We also demonstrate non-contact, real-time vapor detection of fentanyl. Preconcentration of vapors can further extend the detection capabilities. The collection, desorption, and detection of fentanyl vapors at ambient conditions was demonstrated for sampling times of seconds to an hour resulting in increased signal. AFT-MS is a viable detection method of fentanyl and other drugs for screening of packages and cargo.

atmospheric flow tube-mass spectrometry (AFT-MS), ↗

NASA NTRS1988

Laser velocimeter and total pressure measurements in circular-to-rectangular transition ducts

A comprehensive set of total pressure and three-component laser velocimetry (LV) data were obtained within two circular-to-rectangular transition ducts at low subsonic speeds. This set of reference data was acquired for use in identifying secondary flow mechanisms and for assessing the accuracy of computational procedures for calculating such flows. Data were obtained at the inlet and exit planes of an aspect ratio three duct having a length-to-diameter ratio of one (AR310) and an aspect ratio six duct having a length-to-diameter ratio of three (AR630). Each duct was unseparated throughout its transition section. It is therefore concluded that secondary flows can play an important part in the fluid dynamics of transition ducts and needs to be addressed in computational analysis. The strength of the secondary flows depends on both the aspect ratio and relative axial duct length.

Patrick, William P.↗

NASA NTRS1990

Pressure-Measuring Diaphragm Transmits Optical Signals

Proposed sapphire diaphragm performs two functions in instrumented research engine or pressure vessel. Serves both as pressure sensor and as window for observation, optical probing, or optical transmission of other measurements. Deflections of sapphire diaphragm alters resistances of strain gauges mounted around its periphery. At same time, transparent material enables optical measurements of conditions in chamber. Additional information obtained about conditions in chamber without need for additional sensor mounts.

Hill, Arthur J.↗

NASA NTRS1989

Heat-transfer and surface-pressure measurements for the SSME fuel-side turbopump turbine

Detailed heat flux and surface pressure distribution on the first-stage vane and blade of the Space Shuttle Main Engine fuel side turbopump turbine are examined. The specific turbine being utilized for the study is a combination of actual engine hardware and reproduced hardware consistent with that being used at NASA-Marshall for the initial measurements in their newly constructed blow-down turbine test facility. The facility is of the short duration shock tunnel variety, which permits use of thin film thermometers which are used to measure the surface temperature histories at prescribed locations on the turbine component parts. Heat flux values are then inferred from the temperature histories using standard data reduction procedures. The measurement program is described in detail.

Dunn, Michael G.↗

NASA NTRS1977

Combustor fluctuating pressure measurements in-engine and in a component test facility - A preliminary comparison

Combustor internal fluctuating pressure and far-field noise generated in a YF-102 turbofan engine are investigated; combustor internal measurements are also made in a duct-component test facility operating over a range of conditions encompassing those characteristic of the aircraft engine. Although directly measured spectra for the engine and the duct-component test facility show discrepancies, the results of coherence function, transfer function and phase relationship comparisons suggest that the internal dynamics of the combustor as an acoustic source may be preserved in a component test facility.

Reshotko, M.↗

NASA NTRS1975

Force and pressure measurements on an airfoil oscillating through stall, part 2

Details of force, moment, and pressure distributions on a two dimensional, four foot chord, NACA 0012 airfoil, oscillating in pitch through stall, in a 7 ft. x 10 ft. low speed wind tunnel, are presented. Tests were run with the airfoil in a closed test section and also in a test section having four longitudinal slots in each sidewall set to provide minimum tunnel interference on the wing in steady flow. In unsteady flow, differences between the results for the closed and 2% open case are small. The dynamic stall process is not triggered by the bursting of a laminar separation bubble but rather by the separation of the turbulent boundary layer downstream of the bubble.

Parker, A. G.↗

NASA NTRS1977

Combustor fluctuating pressure measurements in engine and in a component test facility: A preliminary comparison

In a program to investigate combustor noise, measurements were made with a YF-102 engine of combustor internal fluctuating pressure and far field noise. The relationship of far field noise to engine internal measurement was ascertained. The relationships between combustor internal measurements obtained in an engine and those obtained in a component test facility were established by using a YF-102 combustor, instrumented identically with that used in the engine tests. The combustor was operated in a component test facility over a range of conditions encompassing engine operation. A comparison of the directly measured spectra at corresponding locations in the two tests showed significant differences. The results of two point signal analyses within each combustor, were similar for both tests, indicating that the internal dynamics of the combustor as an acoustic source are preserved in a component test facility.

Reshotko, M.↗

NASA NTRS1991

Flow visualization and quantitative velocity and pressure measurements in simulated single and double brush seals

A method to visualize and characterize the complex flow fields in simulated single and double brush seals is presented. The brush seal configuration was tested in a gravity fed water tunnel and a pump driven pressurized oil tunnel. Visualization of the flow field revealed regions that are characteristically river jetting, vortical, crossflow and exist upstream, downstream or within the seal. Such flows are especially engendered by variations in fiber void that are spatial and temporal and affect changes in seal leakage and stability. While the effects of interface motion and cylindrical configuration have not been considered herein, it is believed that the observed flow fields and pressure drop patterns characterize flow phenomenology in brush seals. The axial pressure profiles upstream, across and downstream of the brush have been measured under a variety of inlet pressure conditions and the ensuing pressure maps are presented and discussed. Through the application of the Full Flow Field Tracking method developed by the authors, the flow patterns and the accompanying fluid velocities inside the brush were non-intrusively determined and graphically reconstructed.

Braun, M. J.↗