Studies on gas concentration reconstruction methods for simultaneous temperature and H2O concentration tomographic imaging in a flame based on tunable diode laser absorption spectroscopy

Abstract

Analysis of spatial temperature and gas concentration distributions is of great importance for combustion research. Algebraic reconstruction technique (ART) and adaptive algebraic reconstruction technique (AART) based on tunable diode laser absorption spectroscopy are both widely used methods for temperature tomographic imaging in a flame. After being obtained the temperature tomography through iterative method, the gas concentration reconstruction could be determined from a simple division equation (direct gas concentration algorithm) or iterative algorithm (ART gas concentration algorithm or AART gas concentration algorithm) for the second time. For the latter, iterative algorithm was used twice through the whole process. A series of numerical simulations were carried out by three gas concentration reconstruction methods mentioned above. The results demonstrated that AART method had better robustness for different phantoms and stability in the case that measured projections contained different levels of noise. Experimental measurements in a flat methane/air flame on a McKenna burner under three different equivalence ratios (1.0, 0.9, and 0.8) were conducted using AART gas concentration algorithm. The reconstructed results coincide well with those results obtained by thermocouple and theoretical calculation. Both simulation and experiment demonstrate that the AART gas concentration algorithm would be reliable and suitable for simultaneous temperature and H2O concentration tomographic imaging during combustion. As a consequence, this method has unrivalled potential for two-dimensional combustion diagnosis.