Revisit laminar premixed ethylene flames at elevated pressures: A mass spectrometric and laminar flame propagation study

Abstract

This work reports investigations on laminar premixed ethylene (C2H4) flames with special interests on measurements and kinetic modeling at elevated pressures. Chemical structures of laminar premixed C2H4/O2/Ar flames at 3 and 5 atm with the equivalence ratio of 1.4 were measured with molecular beam mass spectrometry. Both the stable and reactive species were identified and quantified in this work. Among them, the mole fractions of H and OH are evidently dependent on pressures. Laminar flame propagation of C2H4/air mixtures at 1 and 2 atm and that of C2H4/O2/He mixtures at 2 and 5 atm were also investigated in a high pressure constant-volume cylindrical combustion vessel at an unburnt temperature (Tu) of 298 K and equivalence ratios of 0.7–1.5. Besides, a kinetic model for C2H4 combustion was developed based on the evaluations of critical reactions with special concerns on recent theoretical calculation progress and validated against both the new data in this work and previous data of ethylene combustion in literature. The updated reactions of C2H4 + O from recent theoretical calculations in the present model can improve the predictions of both the flame speciation results and the laminar burning velocities (LBVs) under rich and elevated pressure conditions. Compared with previous models, C2H4 + O = 3CH2 + CH2O instead of C2H4 + O = CH3 + HCO becomes a major consumption pathway of C2H4 in the present model. This results in the lower production of CH3 which is responsible for the chain termination under rich and elevated pressure conditions. Therefore, the present model could lower down the predictions of the CH3-related speciation data and improve the LBV predictions under rich and elevated pressure conditions.