Modelling of flame structure using thickened flame model coupled with multi-step reaction mechanism

Thickened flame (TF) model is one of the effective methods to simulate combustion phenomenon. Theoretically, it could be extended to multi-step chemical reaction mechanism. However, the results in the present work shown that TF model coupled with multi-step mechanism will underestimate burnt gas temperature, whether in confined or unconfined space. Meanwhile, some post-flame species (CO, OH) concentration are overestimated, which means the decrease in burnt gas temperature is mainly caused by enhanced species diffusion. Dynamic thickened flame (DTF) model coupled with multi-step mechanism performs well for predicting species concentration and combustion state. So it is not recommended to use TF model coupled with a multi-step chemical reaction mechanism. However, the dynamically thickened flame thickness is obviously thinner than the theoretical expectations for the dynamic thickening factor, which is always used to determine thickening factor for a certain mesh size. The main heat release rate zone couldn’t be thickened as expected. A new DTF model used for multi-step reaction mechanism was proposed. The results show that it can both predict the flame structure accurately and get the flame thickness as expected.