Measurement of Temperatures and Oh Concentrations of Solid Propellant Flames Using Absorption Spectroscopy

Lu, Yang; Freyman, Todd M.; Kuo, Kenneth K.

doi:10.1080/00102209508907717

Cited by 18 publications

(4 citation statements)

References 6 publications

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“…11 and 12. Both temperature and concentration data are in good agreement with data from Vanderhoff 4 and Lu 5 who, like us, performed absorption spectroscopy at a nitrogen pressure of 1.6 MPa.…”

Section: Resultssupporting

confidence: 87%

Snapshot Absorption Spectroscopy

Homan

Vanderhoff

1999

Appl Spectrosc

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Experimental improvements have been made in the UV-visible absorption spectroscopy technique applied to propellant flame diagnostics. The two-dimensional feature of an intensified charge-coupled device (CCD) detector was used to simultaneously record multiple, spatially distinct absorption spectra over a region of 0.35 cm. Temporal resolution has been increased to 1 ms by pulsing a simmering xenon arc lamp. The resulting increase in the light intensity by 30 to 70 times over the nonpulsed output provides the necessary light flux to achieve single-pulse, multiple absorption spectra. Species with low concentrations can be measured with the inclusion of multiple-pass optics to increase the effective pathlength through the combustion region. Due to broadband UV-visible absorption observed in propellant flame spectra, typically only 20% of the incident light is transmitted. However, inclusion of a neutral-density filter during the measurement of the incident intensity I0 allows the dynamic range of the detector to be effectively increased by a factor of 5. With these improvements, temperature and OH and NO concentration maps, with 1 ms temporal resolution, have been determined with two different propellant flames.

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Section: Resultssupporting

confidence: 87%

Snapshot Absorption Spectroscopy

Homan

Vanderhoff

1999

Appl Spectrosc

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“…These conditions lead to synthetic spectral transmittances that are consistent with measurements through an actual ame. 2,3 It is assumed that the FTIR spectrometer operates at a spectral resolution of 1.93 cm 1 . For a rapid-scanning spectrometer, such as the Nicolet 740, spectra can be acquired at the rate of 5 Hz at this spectral resolution.…”

Section: Discussion Of Resultsmentioning

confidence: 99%

“…[4][5][6] Although temperature and species concentrations can vary along the LOS within the ame, it appears that many investigators have not accounted for this effect in their datareduction analysis. [1][2][3][4][5][6] In essence, their results represent a weighted average of temperature and species concentrations over the measurement's path length. The development of point-based nonintrusive diagnostic techniques, such as laserinduced uorescence (LIF) and planar LIF (PLIF), 1 has been highly successful; however, their applications in high-pressure ames of solid propellants cause some concern with treatment of quenching effects.…”

mentioning

confidence: 99%

Line-of-Sight Temperature and Species Profiles Determined from Spectral Transmittances

Mallery

Thynell

1997

Journal of Thermophysics and Heat Transfer

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Line-of-sight (LOS) variations of temperature and concentrations of CO and H 2 O within a simulated high-pressure ame are deduced using an inverse analysis. In this work, synthetic spectral transmittances, acquired by a Fourier transform infrared spectrometer along a single LOS, represent the experimental data. The theoretical basis of the analysis is that spectral variations in the absorption coef cient contain information about spatial variations in temperature and species concentrations. The Marquardt-Levenberg method is used to solve for the temperature and species concentrations. Accurate spatial variations of temperature and species concentrations can be recovered when changes in the spectral transmittances caused by noise are smaller than those changes caused by spatial variations in temperature and species concentrations. The recovered centerline temperatures and species concentrations are, respectively, within 5 and 20% of the synthetic values, when the variations in spectral transmittance caused by noise are about the same as that caused by spatial variations in temperature and species concentrations. As temperature increases, a redistribution in the molecular states decreases the spectral absorptances, thereby causing the analysis to become more sensitive to the effects of noise. Nomenclaturec = speed of light, m/s E = rotational energy of lower state F = spectral transmittance g = normalized rovibrational (rotational-vibrational) line shape function h = Planck's constant k = Boltzmann's constant L = 0.0025 m, half of path length m P = order of power series used to approximate partial-pressure pro les m T = order of power series used to approximate temperature pro les N = number of molecules per cm 3 per atm N d = number of data points in measurement N np = number of gaseous species present along the line of sight that is not being quanti ed N p = number of half-periods used to calculate integral over the wave number range N r = number of rovibrational transitions N s = number of species N x = order of quadrature used in the integral along path length N = order of quadrature used in convolution integral P = pressure, atm P i,m = coef cients for partial pressure of ith species Q = partition function S = line intensity T = temperature, K T m = coef cients for temperature pro le w l = weights for Gauss-Legendre quadrature X n (x) = row vector of species mole fractions, Xn = ( ) X , X , X N CO H O 2 2 x = distance along the line of sight from the center of the ame z = x/L = absorption coef cient p = half-width at half-height of spectral line, cm 1 max = maximum retardation of moving mirror, cm n = half-period of instrument line shape, cm 1 = wave number, cm 1 = standard deviation = temperature exponent for p 2 = sum of squares, Eq. (11) = Gaussian distribution function Subscripts i = ith species j= jth rovibrational transition k, l = index for quadrature noise = quantity affected by noise r = reference state t = total true = true quantity 0 = rovibrational line center Superscripts 1, 2 = steps 1 and 2 of d...

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“…Extensive reviews of optical methods applied to solid propellant flames have been reported by Parr and Hanson-Parr [1,2]. Line-of-sight optical techniques such as emission [3,4], UV/visible [5,6], midinfrared [7], and Fourier transform infrared (FTIR) [8] absorption spectroscopies have been used to measure temperature and concentration profiles in these flames. Significant effort was devoted to improve performances, in particular in terms of spatial resolution and signal-to-noise ratio.…”

Section: Introductionmentioning

confidence: 99%

Detection of iron atoms by emission spectroscopy and laser-induced fluorescence in solid propellant flames

et al. 2018

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Planar laser-induced fluorescence on atomic iron is investigated in this paper, and a measurement strategy is proposed to monitor the fluorescence of iron atoms with good sensitivity. A model is proposed to fit the experimental fluorescence spectra, and good agreement is found between simulated and experimental spectra. Emission and laser-induced fluorescence measurements are performed in the flames of ammonium perchlorate composite propellants containing iron-based catalysts. A fluorescence signal from iron atoms after excitation at 248 nm is observed for the first time in propellant flames. Images of the spatial distribution of iron atoms are recorded in the flame in which turbulent structures are generated. Iron fluorescence is detected up to 1.0 MPa, which opens the way to application in propellant combustion.

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Measurement of Temperatures and Oh Concentrations of Solid Propellant Flames Using Absorption Spectroscopy

Cited by 18 publications

References 6 publications

Snapshot Absorption Spectroscopy

Snapshot Absorption Spectroscopy

Line-of-Sight Temperature and Species Profiles Determined from Spectral Transmittances

Detection of iron atoms by emission spectroscopy and laser-induced fluorescence in solid propellant flames

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