Laminar Flame Speed of Methane/Air at Engine-Relevant Conditions: Performance of Different Mechanisms

Abstract

Laminar flame speed (LFS) is used as an important input in certain turbulent premixed combustion modelling for spark ignition engines. At engine-relevant temperatures and pressures, the LFS is difficult to be measured and it is usually obtained from calculations using detailed or reduced chemical mechanisms. However, at very high temperature in the range of 700~1000 K, it is difficult to get the converged solutions during LFS calculation. In this study, the LFS at enginerelevant conditions are obtained from simulating propagating spherical CH 4 /air flames in a closed spherical vessel. The results from different chemical mechanisms are obtained and compared. It is found that there is significant difference between the LFSs predicted from different chemical mechanisms, especially at high temperatures and pressures. It is also shown that the reduced mechanism has very good performance in terms of predicting the LFS at engine-relevant conditions. Besides, the performance of difference chemical mechanisms in terms of predicting the ignition delay time and the excitation time is assessed and significant difference is also observed.