Implementation of non-intrusive jet exhaust species distribution measurements within a test facility

Wright, Paul; McCormick, David; Kliment, Joshua; Ozanyan, Krikor B.; Johnson, Mark P.; Black, John D.; Tsekenis, Stylianos-Alexios; Fisher, Edward; McCann, H.; Lengden, Michael; Wilson, David; Johnstone, Walter; Archilla, Victor; Gonzalez-Nunez, Alvaro; Feng, Yutong; Nilsson, Johan

doi:10.1109/aero.2016.7500731

Cited by 14 publications

(25 citation statements)

References 21 publications

(18 reference statements)

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“…(6) based a high resolution grid with n = 10000 elements for a target concentration image χ and then infused with zero-mean Gaussian noise at a standard deviation of 10% of each data value. The model was constructed to simulate the measurements of the FLITES system [3] based on a beam arrangement of six projection angles at {0, 30, 60, 90, 120, 150} degrees, each comprising twenty one parallel beams, as shown in the schematic of figure 1.…”

Section: Numerical Resultsmentioning

confidence: 99%

“…We are interested in the situations where the degrees of freedom n in the sought image exceed significantly the number of available data m, as this tends to be the usual setting in practical CST experiments [2], [3]. For m n the coefficients matrix in Eq.…”

Section: A Linear Attenuation Model For Concentra-tionmentioning

confidence: 99%

“…At the FLITES experiment an optical imaging ring has been constructed [3] to provide 126 simultaneous measurements of CO 2 equally arranged in 6 projection angles, using the calibration-free 2f/1f wavelength modulation spectroscopy technique (TDLS-WM) [5]. The light sources and sensors are positioned perimetrically at a 12-sided ring of 7 m in diameter.…”

Section: Real Data Reconstructionmentioning

confidence: 99%

“…Chemical Species Tomography (CST) aims to image the concentration of chemical species present in gas mixtures [1]. Its application to carbon dioxide (CO 2 ) in gas turbine aero-engine exhausts is motivated by the aviation industry's need to reduce CO 2 emissions and to enable the analysis of emissions data in order to diagnose engine condition [2], [3]. As CO 2 is a major product of the combustion process, it provides a good proxy to understand the complex phenomena that govern the performance of advanced gas turbines and predict irregularities and faults.…”

Section: Introductionmentioning

confidence: 99%

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Constrained models for optical absorption tomography

et al. 2017

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We consider the inverse problem of concentration imaging in optical absorption tomography with limited data sets. The measurement setup involves simultaneous acquisition of near-infrared wavelength-modulated spectroscopic measurements from a small number of pencil beams equally distributed among six projection angles surrounding the plume. We develop an approach for image reconstruction that involves constraining the value of the image to the conventional concentration bounds and a projection into low-dimensional subspaces to reduce the degrees of freedom in the inverse problem. Effectively, by reparameterizing the forward model, we impose, simultaneously, spatial smoothness and a choice among three types of inequality constraints, namely, positivity, boundedness, and logarithmic boundedness in a simple way that yields an unconstrained optimization problem in a new set of surrogate parameters. Testing this numerical scheme with simulated and experimental phantom data indicates that the combination of affine inequality constraints and subspace projection leads to images that are qualitatively and quantitatively superior to unconstrained regularized reconstructions. This improvement is more profound in targeting concentration profiles of small spatial variation. We present images and convergence graphs from solving these inverse problems using Gauss-Newton's algorithm to demonstrate the performance and convergence of our method.

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Section: Numerical Resultsmentioning

confidence: 99%

Section: A Linear Attenuation Model For Concentra-tionmentioning

confidence: 99%

Section: Real Data Reconstructionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Constrained models for optical absorption tomography

et al. 2017

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“…parallel (58,144,161,163,167) and fan-shaped (150,164,168,169) beam arrangements, the measurement space should be sampled evenly in spatial and angular dimensions to achieve the best image reconstruction results. Subject to the limits imposed by the physical size of the collimators and detectors, regular beam arrangements are often impractical in particular applications such as a multi-cylinder engine and a gas turbine engine (31,170).…”

Section: Beam Optimizationmentioning

confidence: 99%

Laser absorption spectroscopy for combustion diagnosis in reactive flows: A review

Liu

2018

Applied Spectroscopy Reviews

165

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Laser absorption spectroscopy (LAS) has been rapidly developed and widely applied to combustion diagnosis in recent decades. As a costeffective tool for measuring multiple combustion parameters, LAS provides unique properties in terms of accuracy and sensitivity for understanding the reactions and kinetics in reactive flows. Line-ofsight and tomographic LAS techniques have stimulated numerous applications and been proved to be robust for in situ combustion diagnosis in uniform and non-uniform combustion fields, respectively. This review highlights the breakthroughs in the evolution of LAS techniques from the viewpoints of key principles, sensors and instrumentations developed for combustion diagnosis, with particular emphasis on a series of spatially-resolved LAS techniques with their recent applications on obtaining high-fidelity measurement results with minimal intrusion to the practical combustors. Along the way, we note some challenges and requirements for further development of the LAS-based combustion diagnosis.

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Multiparameter gas sensing with linear hyperspectral absorption tomography

Grauer¹,

Emmert²,

Sanders³

et al. 2019

Meas. Sci. Technol.

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Hyperspectral absorption tomography (HAT) reconstructs the distribution of key gas parameters, including composition, pressure, and temperature, from multi-beam absorbance data with numerous spectral resolution elements. There is a nonlinear relationship between the parameters of interest and the spectral absorption coefficient, which must be incorporated into the tomography algorithm. Nonlinear HAT simultaneously reconstructs the composition and temperature of a gas by minimizing a single nonconvex objective function, which combines the light attenuation and spectroscopy models, using a metaheuristic technique. The time required for this computation depends, strongly, on the assumed heuristics, but the high computational cost limits the problem size and, hence, the obtainable spatial resolution. Conversely, linear HAT reconstructs the absorption coefficient for each measurement wavenumber, individually, exploiting the linear structure of the underlying tomography problem. Local spectra are then post-processed with a spectroscopic model to recover multiple parameters. The linear technique enables accurate reconstructions on a high-resolution grid by way of an established statistical imaging algorithm. Moreover, local spectra can be employed to gauge phenomena such as multi-species broadening and line mixing with a calibrated regression model. We simulate linear and nonlinear HAT and reconstruct experimental absorbance data using the former approach to demonstrate its superior performance. Nonlinear reconstructions required a 100-fold computational effort compared to linear HAT. In our experimental test, we reconstructed the mole fraction, pressure, and temperature of water vapor in a stagnation flow, which represents the first three-parameter laser absorption tomography experiment. Simulated and experimental results in our paper make a comprehensive case for linear HAT compared to the nonlinear method.

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Implementation of non-intrusive jet exhaust species distribution measurements within a test facility

Cited by 14 publications

References 21 publications

Constrained models for optical absorption tomography

Constrained models for optical absorption tomography

Laser absorption spectroscopy for combustion diagnosis in reactive flows: A review

Multiparameter gas sensing with linear hyperspectral absorption tomography

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