An experimental and modeling study on extinction strain rate in C2HX flames with varied oxygen content

Abstract

The extinction strain rates (ESR) is an important physical-chemical properties of fuels. Therefore, an experiment study on ESR is crucial for studying emission reduction techniques. In this work, the ESR and laminar burning velocity (LBV) of C2HX fuels under a wide range of conditions are determined experimentally. Moreover, a series of the reduced mechanisms for predicting ESR and LBV of C2 hydrocarbons (C2H2, C2H4, C2H6) is provided, because the research of mechanism reduction seldom pay attention to ESR and LBV. The contribution of this work is therefore the improvement of understanding of the oxidation characteristics of light C2 hydrocarbons and to provide reduced skeletal mechanisms for those fuels with different levels of accuracy for their interaction with reduced oxygen content. For these gas mixtures, the extinction strain rates (ESR) and the laminar burning velocity (LBV), two important physical-chemical properties, were investigated in a counterflow and a heat flux burner setup under atmospheric conditions (1 bar and 298 K). The LBV of the premixed flames, as well as the ESR of the non-premixed C2Hx/O2/N2 flames, are determined experimentally and compared to the numerical predictions of a detailed mechanism (USC II) and the seven corresponding reduced skeletal mechanisms. The present study highlights the non-linear influence on the ESR of C2 hydrocarbons that were found with decreasing fuel content and decreasing oxygen content in either case. Since C2H2 has a significantly higher reactivity than C2H4 and C2H6, this is manifested in lower ESR and higher LBV for the same conditions. The recently developed species-targeted global sensitivity analysis (STGSA) is used to develop reduced mechanisms, showing that they can reproduce the ESR trends and are within the determined measurement uncertainty in a wide range of operating conditions. In addition, these developed significantly reduced mechanisms remain good at predicting the laminar burning velocity. The research generated a unique experimental dataset of the ESR and LBV of C2Hx which was also used to develop reduced mechanisms. Sensitivity analysis for the ESR and LBV gives insight into the difference between ESR and LBV calculations.