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Direct Numerical Simulation of Flame Propagation and Deflagration to Detonation Transition in Confined Space with Different Perforated Plate Positions

ABSTRACT Flame acceleration and the deflagration to detonation transition (DDT) are important physical phenomena in combustion theories. The main objective of this work is to provide a comprehensive understanding of the effect of the positions of obstacles when a flame propagates in obstructed confined channels, using two-dimensional direct numerical simulations (DNSs) with the detailed chemical kinetics mechanism of H2. The underlying mechanism for the flame propagation and detonation, affected by the obstacles with the flame-shockwave and flame–vortex interactions, is investigated. In 1000 K cases, two different detonation modes associated with flame propagation are observed, where for the case with obstacles near the ignition kernel, autoignition takes place in the end-gas region as predicted, while for the case with obstacles far away from the ignition kernel, autoignition occurs, instead, in front of the flame and triggers a DDT immediately. Both of two modes consist three processes: flame propagation stages, flame-pressure wave/shockwave interaction, and detonation development. The evolutions of centerline temperature and pressure are employed to explicitly demonstrate the detonation process. The differences in the shockwave formation, peak temperature, and pressure values can be clearly observed. The mechanisms of the different detonation modes induced by different obstacle positions are analyzed in detail for the first time. The results indicate that the compressed and preheated temperature of the unburned mixture determines the detonation combustion mode. The conclusion is further proved in the flame-shockwave number variation and detonation modes transition when initial temperature is changed. This study will provide new insight into the DDT and detonation phenomena in engines.