High Temperature Gasdynamics Laboratory

Escondido, United States

High Temperature Gasdynamics Laboratory

Escondido, United States
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Chang L.S.,Stanford University | Chang L.S.,High Temperature Gasdynamics Laboratory | Strand C.L.,Stanford University | Strand C.L.,High Temperature Gasdynamics Laboratory | And 7 more authors.
AIAA Journal | Year: 2011

Measurements of mass flux are obtained in a vitiated supersonic ground-test facility using a sensor based on lineof-sight diode laser absorption of water vapor. Mass flux is determined from the product of measured velocity and density. The relative Doppler shift of an absorption transition for beams directed upstream and downstream in the flow is used to measure velocity. Temperature is determined from the ratio of absorption signals of two transitions (λ1 1349 nm and λ2 1341:5 nm) and is coupled with a facility pressure measurement to obtain density. The sensor exploits wavelength-modulation spectroscopy with second-harmonic detection for large signal-to-noise ratios and normalization with the 1f signal for rejection of non-absorption-related transmission fluctuations. The sensor line of sight is translated both vertically and horizontally across the test section for spatially resolved measurements. Time-resolved measurements of mass flux are used to assess the stability of flow conditions produced by the facility. Measurements of mass flux are within 1.5% of the value obtained using a facility predictive code. The distortion of the wavelength-modulation spectroscopy lineshape caused by boundary layers along the laser line of sight is examined and the subsequent effect on the measured velocity is discussed. Amethod for correcting measured velocities for flow nonuniformities is introduced and application of this correction brings measured velocities within 4 m/s of the predicted value in a 1630 m/s flow. Copyright © 2011 by the American Institute of Aeronautics and Astronautics, Inc.


Schultz I.A.,Stanford University | Schultz I.A.,High Temperature Gasdynamics Laboratory | Goldenstein C.S.,Stanford University | Goldenstein C.S.,High Temperature Gasdynamics Laboratory | And 8 more authors.
Journal of Propulsion and Power | Year: 2014

The development and use of a tunable diode laser absorption spectroscopy sensor for combustion product water vapor in a hydrogen-fueled model scramjet combustor are presented. A pair of absorption transitions was selected from the combination bands of water vapor near 1.4 μm exploiting telecommunications diode laser and fiber technologies. Wavelength-modulation spectroscopy with detection of the peak second-harmonic signal was used owing to its superior noise-rejection capabilities. The sensor measured temperature and H2O column density at two axial planes downstream of fuel injection with the absorption line-of-sight positioned at over 40 measurement locations using a translation stage system. The combustion product concentration and the gas temperature were not uniform along the line-of-sight, and the influence of these nonuniformities on the interpretation of the tunable diode laser measurements is discussed. The measurements are compared with published computational fluid dynamics simulations using two different kinetic mechanisms. Copyright © 2013 by the American Institute of Aeronautics and Astronautics, Inc.


Chang L.S.,Stanford University | Chang L.S.,High Temperature Gasdynamics Laboratory | Jeffries J.B.,Stanford University | Jeffries J.B.,High Temperature Gasdynamics Laboratory | And 2 more authors.
AIAA Journal | Year: 2010

A mass flux sensor based on line-of-sight diode laser absorption of water vapor is designed, constructed, and tested in a low-speed wind tunnel in anticipation of subsequent use in supersonic test facilities. Water vapor absorption is monitored to capitalize on its presence in air and in combustion-driven facilities as well as the availability of fiber-coupled diode lasers that access the 2v1,2v3, and v1 + v 3 absorption bands near 1.4 microns. Mass flux is determined from the product of measured velocity and density. Velocity is obtained from the relative Doppler shift of an absorption transition for beams directed upstream and downstream in the flow. Temperature is determined from the ratio of absorption signals of two transitions and is coupled with a facility pressure measurement to obtain density. The sensor exploits wavelength-modulation spectroscopy with second-harmonic detection (wavelength-modulation spectroscopy-2f) for large signal-to-noise ratios. Optimization of the modulation for 1/-normalized wavelength-modulation spectroscopy-2f (wavelength-modulation spectroscopy-2f/1f) signals for velocity sensing is presented for the first time. Criteria to select the absorption transitions are presented and the spectroscopic parameters of the needed database are determined with laboratory measurements. Using this database, the measurement of temperature is validated within 1% of thermocouple measurements in a heated cell. The velocity measurements are validated from 2.5-18 m/s with a measurement uncertainty of ±0.5 m/s in a high-uniformity wind tunnel. Copyright © 2010 by Leyen S. Chang, Jay B. Jeffries, and Ronald K. Hanson. Published by the American Institute of Aeronautics and Astronautics, Inc.


Barbour E.A.,Stanford University | Barbour E.A.,High Temperature Gasdynamics Laboratory | Hanson R.K.,Stanford University | Hanson R.K.,High Temperature Gasdynamics Laboratory
Journal of Propulsion and Power | Year: 2010

Performance losses in the form of chemical nonequilibrium, heat transfer, and friction are investigated in the context of a detonation tube with nozzles using quasi-one-dimensional computational fluid dynamics. Finite-rate chemistry losses incur up to 10% penalty in overall cycle impulse for mixtures containing fuel and oxygen. These same losses are greatly reduced when oxygen is replaced by air because of reduced energy available through chemical recombination. Heat transfer and friction are less important, both for diverging and converging nozzles (∼5% overall cycle impulse). The exception is for H2=air where losses can be up to 15%. Finally, a method of predicting losses assuming steady flow nozzles, thereby greatly reducing computational cost, is explored. Copyright © 2009 by the American Institute of Aeronautics and Astronautics, Inc.


Miller V.A.,Stanford University | Miller V.A.,High Temperature Gasdynamics Laboratory | Gamba M.,Stanford University | Gamba M.,University of Michigan | And 4 more authors.
AIAA Journal | Year: 2014

The article focuses on secondary diaphragm thickness effects and improved pressure measurements in an expansion tube. Analog or digital signal processing can be used to filter some noise from the measurements, but at the expense of measurement bandwidth or accuracy; thus, the engineer must compromise between bandwidth and SNR to acquire reliable pressure measurements. Shock speeds are measured 2 m from the primary diaphragm station in the driven section of the expansion tube, and 1mfrom the secondary diaphragm station in the expansion section of the tube. The four sensors are mounted in a flat plate with a sharp leading edge, which is installed into the test section of the expansion tube. As a derivative result, it was concluded that secondary diaphragm thickness has no observable impact on test gas conditions, as inferred from shock Mach numbers. It has also been shown that piezoresistive transducer measurement quality depends on the material into which the sensor is mounted and whether or not the sensor circuit is grounded.

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