نوع مقاله : مقاله پژوهشی
1 گروه مکانیک- دانشکده مهندسی- دانشگاه بیرجند- بیرجند- ایران
2 هیات علمی دانشگاه آزاد اسلامی واحد نجف آباد
عنوان مقاله [English]
This paper aims to numerically investigate the effect of blockage ratio on the mechanisms governing the deflagration to detonation transition (DDT) in inhomogeneous mixtures of H2-air. The study combustion chamber is a closed rectangular cross-section channel with obstacles that have been studied in three blockage ratios of 10, 30, and 60 percent and at different obstacle spacing. The present numerical simulation was performed using the SST-K-ω turbulence model and the combustion model of the Weller flame wrinkling and the HLLC method was used to shock-capturing. The results show that for the 10% blockage ratio, the onset of detonation occurred in the unobstructed part of the channel and for the blockage ratios of 30% and 60% DDT occurred in the obstructed section of the channel. The mechanisms governing the DDT process change as the blockage ratio and obstacle spacing change. The Mach reflection from the lower wall of the channel and the formation of the reactive Mach stem, the reflection of the Mach stem from the wall of the lower obstacles, and the reflection of incident shock from the wall of the upper obstacles are the most important governing mechanisms observed. The results also show that flame acceleration and the occurrence of DDT in the channel occur faster as the blockage ratio increases. The fastest onset of detonation occurred at the blockage ratio of 60% and the space to height ratio of S/H = 2.5.