Diode laser absorption spectroscopy of water vapor in a scramjet combustor

Griffiths, Alan D.; Houwing, A. F. P.

doi:10.1364/ao.44.006653

Cited by 44 publications

(26 citation statements)

References 13 publications

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“…In this work, we focused on analyzing the uncertainties of velocity measurements using TDLAS, especially when applied in high speed flows such as those encountered in scramjet facilities [6,7]. Velocity is a critical parameter for propulsion study, and various mechanisms can cause nonuniformity in supersonic flows.…”

Section: Introductionmentioning

confidence: 99%

Uncertainty in velocity measurement based on diode-laser absorption in nonuniform flows

Cai

et al. 2012

Appl. Opt.

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This work investigates the error caused by nonuniformities along the line-of-sight in velocity measurement using tunable diode-laser absorption spectroscopy (TDLAS). Past work has demonstrated TDLAS as an attractive diagnostic technique for measuring velocity, which is inferred from the Doppler shift of two absorption features using two crossing laser beams. However, because TDLAS is line-of-sight in nature, the obtained velocity is a spatially averaged value along the probing laser beams. As a result, nonuniformities in the flow can cause uncertainty in the velocity measurement. Therefore, it is the goal of this work to quantify the uncertainty caused by various nonuniformities typically encountered in practice, including boundary layer effects, the divergence/convergence of the flow, and the methods used to fit the Doppler shift. Systematic analyses are performed to quantify the uncertainty under various conditions, and case studies are reported to illustrate the usefulness of such analysis in interpreting experimental data obtained from a scramjet facility. We expect this work to be valuable for the design and optimization of TDLAS-based velocimetry, and also for the quantitative interpretation of the measurements.

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Section: Introductionmentioning

confidence: 99%

Uncertainty in velocity measurement based on diode-laser absorption in nonuniform flows

Cai

et al. 2012

Appl. Opt.

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“…Most of the applications of diode laser absorption spectroscopy in engines, as opposed to wind-tunnel models, have used water vapor as the absorbing species and distributed feedback diode lasers as the light source (Griffiths and Houwing 2005, Upschulte et al 2000, Zhao et al 2003, Chang et al 2010). However, these tests tended to concentrate on the combustor behavior of the engine, where water vapor is produced in large quantities by the combustion processes.…”

Section: Summary Of Previous Researchmentioning

confidence: 99%

Diode Laser Sensor for Scramjet Inlets

O’Byrne¹,

Wittig²,

Kurtz³

et al. 2011

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Report Documentation PageForm Public reporting burden for the collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to Washington Headquarters Services, Directorate for Information Operations and Reports, 1215 Jefferson Davis Highway, Suite 1204, Arlington VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to a penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number. REPORT DATE JUN 20112. REPORT TYPE This work presents test results of a diode-laser sensor for an axially symmetric inlet in a Mach 6 hypersonic flow facility. The conical inlet design presented here is more realistic than the flat plate design presented in the previous report, and is similar to the design that will be chosen as part of the Australian Space Research Program SCRAMSPACE flight test scheduled for 2012. The optical system was changed for this study to make the pitch and catch optics less sensitive to vibration, and to fit into a smaller volume than for the previous test. In addition, wavelength modulation detection was attempted with the system. Initial tests of the conical inlet design showed that it was not starting, as indicated using flow visualization images. The second version of the sensor has similar velocity sensitivity to the system used for the flat plate inlet test. The conical system was, however, still too susceptible to amplitude noise, which hinders the ability of the system to measure the free stream temperature or the angle of attack. Electrical problems with the log-ratio amplifier prevented temperature measurements for the vehicle. Preliminary vibration tests have shown that the problem is caused by independent motion between the laser and collimator when the tunnel fires. A preliminary design of a low-power lock-in amplifier for use in field experiments was completed, and tests with current inputs in place of photodiodes proved successful. SUBJECT TERMS

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“…Consequently, many variations of the TDLAS diagnostic have been successfully demonstrated for in situ measurements of various flow parameters in scramjet test facilities [11][12][13][14][15][16][17]. For instance, Upschultep et al [11] measured velocity, static temperature, and water vapor concentration at the inlet of the combustor in a direct-connected test facility.…”

Section: Introductionmentioning

confidence: 99%

“…For instance, Upschultep et al [11] measured velocity, static temperature, and water vapor concentration at the inlet of the combustor in a direct-connected test facility. Griffiths and Houwing [13] measured temperature and water vapor concentration in the expanding exit region of the combustor in a shock tunnel at a 20 kHz repetition rate. Liu et al [14] measured the temperature and water partial pressure at eight fixed vertical positions at the exit section using both direct absorption and a wavelength modulation strategy.…”

Section: Introductionmentioning

confidence: 99%

Simultaneous measurements of multiple flow parameters for scramjet characterization using tunable diode-laser sensors

et al. 2011

Appl. Opt.

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This paper reports the simultaneous measurements of multiple flow parameters in a scramjet facility operating at a nominal Mach number of 2.5 using a sensing system based on tunable diode-laser absorption spectroscopy (TDLAS). The TDLAS system measures velocity, temperature, and water vapor partial pressure at three different locations of the scramjet: the inlet, the combustion region near the flame stabilization cavity, and the exit of the combustor. These measurements enable the determination of the variation of the Mach number and the combustion mode in the scramjet engine, which are critical for evaluating the combustion efficiency and optimizing engine performance. The results obtained in this work clearly demonstrated the applicability of TDLAS sensors in harsh and high-speed environments. The TDLAS system, due to its unique virtues, is expected to play an important role in the development of scramjet engines.

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Diode laser absorption spectroscopy of water vapor in a scramjet combustor

Cited by 44 publications

References 13 publications

Uncertainty in velocity measurement based on diode-laser absorption in nonuniform flows

Uncertainty in velocity measurement based on diode-laser absorption in nonuniform flows

Diode Laser Sensor for Scramjet Inlets

Simultaneous measurements of multiple flow parameters for scramjet characterization using tunable diode-laser sensors

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