Avishek Guha

Tomographic Imaging of Flames: Assessment of Reconstruction Error Based on Simulated Results

Temperature and concentration distributions of a horizontal section through a simulated stationary test flame were reconstructed with the help of computer tomography. The study uses temperature and concentration distributions equal to published time-averaged data for the Sandia D flame. Projection values are obtained by simulated line-of-sight integration for two water vapor (H2O) absorption lines in the 6930–6940  cm−1 range, where direct absorption spectroscopy and wavelength modulation spectroscopy with second harmonic frequency detection are considered. The projected values obtained from line-of-sight measurements are deconvoluted by tomographic methods, where Abel inversion and filtered backprojection are investigated. The tomographic reconstruction yields spatially resolved spectroscopic data, which is then used to calculate distributions for temperature and concentrations. Results illustrate that tunable diode laser absorption spectroscopy artifacts are caused by relatively small errors in reconstr...

Limited View Tomography of Combustion Zones Using Tunable Diode Laser Absorption Spectroscopy: Simulation of an Algebraic Reconstruction Technique

Temperature and concentration distributions of a simulated flame were reconstructed with the help of computer tomography and tunable diode laser absorption spectroscopy (TDLAS). Reconstructions were based on the simulated numerical values of temperature and concentration of a stationary flame. Integrated absorption measurements along the line-of-sight (LOS) across the flames due to absorption by water vapor (H2O) in the near infra-red (NIR) region, specifically the 6930–6940 cm−1 range, were simulated to obtain the projection values for tomography. Spectroscopic parameters for the absorptions transitions, such as line-strengths, transition wavenumbers, collisional broadening coefficients and coefficients for their temperature dependency were selected from the HITRAN 2004 database. Simulated LOS data are inverted using a multiplicative algebraic reconstruction technique (MART), which are known to outperform traditional filtered back projection methods for cases with limited numbers of views. Based on spatially resolved reconstructions of spectroscopic data, temperature and concentration distributions are calculated using the wavelength modulation spectroscopy with second harmonic detection (WMS-2f) technique. A parametric study based on the number of views, orientation of views and number of rays per view required by the ART is performed in order to assess requirements for an acceptable reconstruction.Copyright

A tunable diode laser sensor for temperature measurement in large-scale hydrogen generation furnaces

A compact TDL sensor is developed for temperature measurement in large scale SMR furnaces. Careful wavelength selection enables measurement in the long path, high absorbance, combustion environment, with single telecom laser at low cost.

Tomographic Imaging of Combustion Zones: Impact of Measurement Noise and Reconstruction Error

Temperate and concentration distributions of a horizontal section through a stationary test flame were reconstructed with the help of computer tomography. Simulated reconstructions are based on temperature and concentrations distributions equal to published time-averaged data of the Sandia D flame. Based on property distributions, line integrated absorption due to water vapor (H 2 O) in the 6930-6940 cm 1 range was simulated to obtain projection values for tomographic reconstructions, where spectroscopic parameters for absorption features were obtained from the HITRAN 2004 1 database. Simulated projection values were calculated for direct absorption spectroscopy (DA) and wavelength modulation spectroscopy with second harmonic frequency detection (WMS-2f). The resulting projections were de-convoluted by tomographic methods, where Abel inversion and filtered backprojection were investigated. Based on the reconstructed spatial distribution of spectroscopic data, temperature and concentration profiles were obtained. Results highlight the impact of uncertainties introduced by measurement noise, deviations of reconstructed values, and tomographic artifacts. The comparisons of reconstructed results indicate that WMS-2f in conjunction with tomography is a viable method to reconstruct spatially resolved temperature and concentration distributions for stationary flames.

Innocuous Intracellular Ice Formation in Adult Stem Cells in the Presence of Polyvinylpyrollidone

The objective of this work was to assess the effect of 10% (w/v) polyvinylpyrrolidone (PVP) on the pattern of intracellular ice formation (IIF) in human adipose tissue derived adult stem cells (ASCs) in the absence of serum and other cryoprotective agents (CPAs).