Numerical Evaluation of Heat Release Rate and Equivalence Ratio Determination Using Chemiluminescence in Premixed Ethanol/Air Flames

Abstract

The flame self-light emission can be readily imaged with modern digital cameras and analyzed with the ever-increasing computing and processing power. Therefore, chemiluminescence, as a promising optical diagnostic tool, is worthy of further investigation. In the present study, numerical analysis, which is based on excited state species (OH*, CH* and Csub>2*) chemiluminescence profiles in one-dimensional laminar premixed ethanol/air flames, is conducted on determination of heat release rate and equivalence ratio. The capability of flame chemiluminescence being a sensor of heat release rate at various equivalence ratios is discussed by integration of rate of production analysis and sensitivity analysis. Also, the phenomenon, showing that the peak chemiluminescence intensity ratio of C2*/CH* has a tendency of increasing almost linearly first and then descending with the local equivalence ratio, is demonstrated from the aspect of chemical mechanism for the first time. The results indicate that reactions Csub>2H+Osub>2 CH*+COsub>2 and sub>2H+H Hsub>2+Csub>2* are of great significance to invert the monotonicity of the chemiluminescence intensity ratio of Csub>2 */CH* with the equivalence ratio. Additionally, the locations of the maximum peak intensities of each excited state species are different at various equivalence ratios. The deviation is mainly attributed to certain specific reaction paths. Therefore, reaction paths analysis is carried out for a better understanding of ethanol oxidation process and the formation and decay reactions of the excited radicals. This work illustrates the correlations between chemiluminescence and flame characteristics in ethanol/air flame, giving insight into further investiagtion of chemilumienscence experimental tests.