Understanding and overcoming scene-change artifacts in imaging Fourier-transform spectroscopy of turbulent jet engine exhaust

Tremblay, Pierre; Gross, Kevin C.; Farley, Vincent; Chamberland, Martin; Villemaire, André; Perram, Glen P.

doi:10.1117/12.828001

Cited by 13 publications

(17 citation statements)

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“…We have previously reported a method of processing interferograms when studying turbulent sources. 8 However, that method has not yet been used in the study of this smokestack data.…”

Section: Methodsmentioning

confidence: 99%

“…The scale factor appears symmetric about the optical center pixel near (i , j ) = (30, 40). Fitting Equation 8 to the values of m i ,j obtained for all pixels gives estimates of (i 0 , j 0 ) = (31.1, 39.4) and (θ W , θ H ) = (325, 326) × 10 −6 μrad. These results are Table 1.…”

Section: Spectral Axis Calibrationmentioning

confidence: 99%

“…While it reduces the dynamic range available for measuring the modulated signal that encodes the spectral information, it is beneficial in the analysis and processing of interferograms collected from turbulent sources. 7,8 This paper presents the complete spectro-radiometric calibration procedure used to process recent field measurements of the emission plume from a coal-fired power plant near Dayton, Ohio. Asymmetric-length interferograms were collected and a simple method of interferogram weighting and spectral averaging is devised which leads to an easily modeled instrument line shape (ILS) free from imaginary artifacts.…”

Section: Introductionmentioning

confidence: 99%

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Instrument calibration and lineshape modeling for ultraspectral imagery measurements of industrial smokestack emissions

Gross¹,

Tremblay

Bradley³

et al. 2010

SPIE Proceedings

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The Telops Hyper-Cam midwave (InSb 1.5-5.5 μm) imaging Fourier-transform spectrometer observed the plume from a coal-burning power plant smokestack. From a distance of 600 meters, the plume was captured on a 128 × 64 pixel sub-window of the focal-plane array with each pixel imaging a 19.5 × 19.5 cm 2 region. Asymmetric interferograms were collected with long side and short side maximal optical path differences of 2.4 cm and 0.9 cm, respectively. Interferograms were recorded for each scan direction. The plume was strongly emissive across 1800-3000 cm −1 , and raw spectra revealed emissions from CO 2 , CO, H 2 O, NO, SO 2 , and HCl. A complete description of the instrument calibration and lineshape modeling is presented, including a simple and computationally efficient method of averaging spectra from forwardand reverse-scan interferograms that avoids the need to model a complex instrument lineshape. A simple radiative transfer model is developed to interpret the spectrum between 2565 ≤ν ≤ 3000 cm −1 . Examination of the HCl spectrum demonstrates exceptional agreement between the data and an ideal instrument lineshape. For a pixel immediately above the stack exit, the plume temperature is estimated to be 399.6 ± 0.6 K with an SO 2 concentration of 376 ± 10 ppm v , and these values agree well with in situ measurements of 407.0 ± 0.2 K and 383 ± 2 ppm v , respectively.

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“…We have previously reported a method of processing interferograms when studying turbulent sources. 8 However, that method has not yet been used in the study of this smokestack data.…”

Section: Methodsmentioning

confidence: 99%

Section: Spectral Axis Calibrationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Instrument calibration and lineshape modeling for ultraspectral imagery measurements of industrial smokestack emissions

Gross¹,

Tremblay

Bradley³

et al. 2010

SPIE Proceedings

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“…[4][5][6][7][8] For the engine measurements, more than 14, 000 symmetric-length interferograms were collected on a 64 × 32 pixel sub-window of the 320 × 256 pixel InSb focal-plane array (FPA). With an angular instantaneous field-of-view of 0.326 mrad, this translates to a 6.25 × 3.12 cm 2 total FOV.…”

Section: Methodsmentioning

confidence: 99%

First imaging Fourier-transform spectral measurements of detonation in an internal combustion engine

Gross¹,

Borel²,

White

et al. 2010

SPIE Proceedings

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The Telops Hyper-Cam midwave (InSb 1.5-5.5 μm) imaging Fourier-transform spectrometer (IFTS) observed repeated detonations in an ethanol-powered internal combustion (IC) engine. The IC engine is a Megatech Corporation MEG 150 with a 1 in. bore, 4 in. stroke, and a compression ratio of 3 : 1. The IC combustion cylinder is made from sapphire permitting observation in the visible and infrared. From a distance of 3 m, the IFTS imaged the combustion cylinder on a 64 × 32 pixel array with each pixel covering a 0.1 × 0.1 cm 2 area. More than 14, 000 interferograms were collected at a rate of 16 Hz. The maximum optical path difference of the interferograms was 0.017 cm corresponding to an unapodized spectral resolution of 36 cm −1 . Engine speed was varied between 600-1200 RPM to de-correlate the observation time scale from the occurrence of detonations. A method is devised to process the ensemble of interferograms which takes advantage of the DC component so that the time history of the combustion spectrum can be recovered at each pixel location. Preliminary results of this analysis will be presented.

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“…The interferograms appeared noisy as a result of stochastic intensity fluctuations caused by turbulence in the plume. Temporal averaging substantially reduced the noise in the interferogram [27,28].…”

Section: Imagerymentioning

confidence: 99%

Thermal degradation of Poly(methyl methacrylate) with a 1.064 μm Nd:YAG laser in a buoyant flow

Acosta

Gross

Perram

2015

Polymer Degradation and Stability

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Understanding and overcoming scene-change artifacts in imaging Fourier-transform spectroscopy of turbulent jet engine exhaust

Cited by 13 publications

References 0 publications

Instrument calibration and lineshape modeling for ultraspectral imagery measurements of industrial smokestack emissions

Instrument calibration and lineshape modeling for ultraspectral imagery measurements of industrial smokestack emissions

First imaging Fourier-transform spectral measurements of detonation in an internal combustion engine

Thermal degradation of Poly(methyl methacrylate) with a 1.064 μm Nd:YAG laser in a buoyant flow

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