Analysis of Local Extinction and Re-Ignition in Turbulent Diffusion Flame with Chemical Explosive Mode Analysis and Lagrangian Investigation

摘要

Lagrangian investigations of the local extinction and re-ignition of turbulent diffusion flame are performed by one-dimensional turbulence (ODT) model with detailed chemistry. Based on the chemical explosive mode analysis (CEMA) and Lagrangian tracer method, diagnostic tools are defined to calculate the local Damk?hler number and distinguish the different scenarios of extinction and re-ignition. The results show that the local extinction region can be characterized by a large negative Damk?hler number based on CEMA, while the stable burning region can be characterized by a large positive Damk?hler number. From the Lagrangian investigation, two scenarios of local extinction, i.e., severe extinction with lower temperature and moderate extinction with higher temperature, are shown. Meanwhile, two re-ignition mechanisms are distinguished by the explosion index of the process prior to re-ignition. It is found that re-ignition mechanism via independent flamelet corresponds to a high radical explosion index and small temperature gradient, while re-ignition mechanism through premixed flame propagation corresponds to a rather long preheat period with thermal runaway and high temperature explosion index.