Simultaneous reconstruction of temperature and concentration of H2O and soot based on infrared emission spectrum by inverse analysis

The simultaneous measurement of temperature and concentration of species for emission-based measuring methods is difficult due to the coupling of the radiation from soot and gas. In this paper, a new method, the stochastic particle swarm optimization and line-by-line (SPSO-LBL) algorithm using emission spectrum, was proposed for simultaneous reconstruction of temperature, concentration of H2O and soot. The validation results calculated by SPSO-LBL algorithm showed that the average relative error was less than 0.1%, verifying the accuracy of SPSO-LBL algorithm. The flame temperature, molar fraction of H2O and soot volume fraction (SVF) in laminar ethylene flames at different equivalence ratios were inverted using SPSO-LBL algorithm based on the emission spectrum of flame. The results showed that the calculated spectral radiative intensity agreed well with the measured spectral radiative intensity, and the maximum relative error was less than 8% for all cases. Under the equivalence ratios of 0.80, 1.07 and 1.38, the temperature, molar fraction of H2O, and SVF decreased with the increase of height due to the radiative heat transfer between flame and surrounding environment as well as diffusion of H2O and soot from burner nozzle to the downstream of the flame. When the equivalence ratio increased to 1.75, the temperature increased first and then decreased, the molar fraction of H2O decreased, and the SVF increased with the increase of height since the suppression effect of H2O on the formation of soot decreased.