Supersonic Mass-Flux Measurements via Tunable Diode Laser Absorption and Nonuniform Flow Modeling

Chang, Leyen S.; Strand, Christopher L.; Jeffries, Jay B.; Hanson, Ronald K.; Diskin, G. S.; Gaffney, Richard L.; Capriotti, D. P.

doi:10.2514/1.j051118

Cited by 61 publications

(15 citation statements)

References 15 publications

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“…The viability of TDLAS as a simple, low-power, robust diagnostic for scramjets has been demonstrated in several ground tests (for example [8][9][10][11]) and in one flight test [12,13]. With the notable exception of the flight test system, most tests have concentrated on water vapor measurements in the combustor.…”

Section: Previous Tunable Diode Laser Absorption Spectroscopy Senmentioning

confidence: 99%

Rugged, Scramjet Inlet Temperature and Velocity Sensor: Design and Ground Test

et al. 2016

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The design and testing of a gas temperature and velocity scramjet engine inlet sensor based on tunable diode laser absorption spectroscopy of oxygen is discussed. The robustness and stability of the optical design necessitated by the dynamic vibrational and thermal environment were balanced against the need for compact size and very high signalto-noise ratio in a low-pressure, high-altitude flight regime. Test results demonstrated very good mechanical and thermal stability and an adequate signal-to-noise ratio for altitudes up to 30 km with predicted O 2 absorbance peaks greater than the signal standard deviation by a factor of more than 3. Nomenclature I, I 0 = signal intensity with and without sample gas (arbitrary units) T= I∕I 0 , sample gas transmittance

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Section: Previous Tunable Diode Laser Absorption Spectroscopy Senmentioning

confidence: 99%

Rugged, Scramjet Inlet Temperature and Velocity Sensor: Design and Ground Test

et al. 2016

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“…The lineshape function is defined to have an area of unity and can be eliminated from calculations by measuring the integrated area; this is the total area under the absorbance profile for a single line as shown in Eq. (3).…”

Section: Iia Absorption Fundamentalsmentioning

confidence: 99%

“…Historically, tunable diode laser absorption spectroscopy (TDLAS) sensors have played a pivotal role in this process by supplying reliable in situ measurements of important thermophysical properties such as temperature, species concentration, pressure, and velocity. 1,2,3 However, in the past sensors have either assumed that the conditions were uniform along the line-of-sight (LOS) or added complications by measuring along many lines in order to determine nonuniform distributions. 4 Here we acknowledge non-uniformity along the the LOS, but use a new scanned wavelength-modulation spectroscopy (WMS) strategy to measure changes to the transition lineshape due to non-uniformity and provide quantitative WMS absorption results.…”

Section: Introductionmentioning

confidence: 99%

Hypersonic scramjet testing via TDLAS measurements of temperature and column density in a reflected shock tunnel

Schultz

Goldenstein

Strand

et al. 2014

52nd Aerospace Sciences Meeting

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A wavelength-multiplexed two-color TDLAS sensor probing transitions near 1.4 µm was developed to measure H2O temperature and column density simultaneously across three lines-of-sight in a ground-based model scramjet combustor. High-enthalpy scramjet conditions equivalent to Mach 10 flight were generated with a reflected shock tunnel. The sensor hardware development and optical engineering to overcome noisy combustor conditions including short test time, beam steering, and mechanical vibration are discussed. A new scanned wavelength-modulation spectroscopy (WMS) technique was used to acquire the complete spectral lineshape while maintaining the high signal-to-noise ratio characteristic of WMS measurements. Two combusting flow experiments were conducted and the results compared with steady-state CFD calculations, with both the simulations and the measurements finding formation of H2O from H2 combustion during the test time. To our knowledge, this work represents the first use of WMS in a reflected shock tunnel and the first use of scanned-WMS in a scramjet combustor. Nomenclature I 0 = incident spectral intensity, W/cm 2 s −1 I t = transmitted spectral intensity, W/cm 2 s −1 ν = optical frequency, cm −1 α = absorbance L = optical path length, cm n i = number density of absorbing species, molecules/cm 3 S n = transition linestrength, cm −1 /molecule cm −2 φ = lineshape function T = temperature, K P = pressure, atm χ = gas mole fraction vector χ i = gas mole fraction of species i A = integrated absorbance, cm −1 N i = column density, molecules/cm −2 σ i = column density (mass basis), kg/cm −2 ρ i = density of absorbing species i, kg/m −3 Q = partition function of absorption transition AIAA SciTech h = Planck constant, J·s c = speed of light, cm/s E = lower state energy of absorption transition, cm −1 k = Boltzmann constant, J/K ν 0 = line-center frequency of absorption transition, cm −1 I 0 = average laser intensity, W/cm 2 s −1 i n = intensity sinusoid amplitude (n=1, 2) ψ n = intensity sinusoid phase shifts (n=1, 2) ν = laser center frequency, cm −1 a n = wavelength scan and modulation depths (n=1, 2) Ψ n = wavelength sinusoid phase shifts (n=1, 2) f s = laser scan frequency, Hz f m = laser modulation frequency, Hz Φ = fuel-air equivalence ratio θ = angle of attack γ = heat capacity ratio c P /c V

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“…16 The error caused by temperature and velocity gradients along the LOS in velocity measurement using WMS-TDLAS was analyzed. 17,18 There has been a lack of quantitative analysis on the effect of temperature gradients across the LOS laser spectroscopy for gas concentration measurements.…”

Section: Introductionmentioning

confidence: 99%

Thermal Boundary Layer Effects on Line-of-Sight Tunable Diode Laser Absorption Spectroscopy (TDLAS) Gas Concentration Measurements

Werhahn

Ebert

2018

Appl Spectrosc

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The effects of thermal boundary layers on tunable diode laser absorption spectroscopy (TDLAS) measurement results must be quantified when using the line-of-sight (LOS) TDLAS under conditions with spatial temperature gradient. In this paper, a new methodology based on spectral simulation is presented quantifying the LOS TDLAS measurement deviation under conditions with thermal boundary layers. The effects of different temperature gradients and thermal boundary layer thickness on spectral collisional widths and gas concentration measurements are quantified. A CO TDLAS spectrometer, which has two gas cells to generate the spatial temperature gradients, was employed to validate the simulation results. The measured deviations and LOS averaged collisional widths are in very good agreement with the simulated results for conditions with different temperature gradients. We demonstrate quantification of thermal boundary layers' thickness with proposed method by exploitation of the LOS averaged the collisional width of the path-integrated spectrum.

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Supersonic Mass-Flux Measurements via Tunable Diode Laser Absorption and Nonuniform Flow Modeling

Cited by 61 publications

References 15 publications

Rugged, Scramjet Inlet Temperature and Velocity Sensor: Design and Ground Test

Rugged, Scramjet Inlet Temperature and Velocity Sensor: Design and Ground Test

Hypersonic scramjet testing via TDLAS measurements of temperature and column density in a reflected shock tunnel

Thermal Boundary Layer Effects on Line-of-Sight Tunable Diode Laser Absorption Spectroscopy (TDLAS) Gas Concentration Measurements

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