Effect of blockage mode on hydrogen deflagration to detonation transition in a long and narrow space

To investigate the mechanism of deflagration-to-detonation transition (DDT) in premixed hydrogen-air within confined a long and narrow space, several numerical simulations are conducted in this study. The propagation behavior of hydrogen premixed flames is described by coupling the SST k-? turbulence model with the detailed chemical reaction mechanism. The evolution of combustion-induced shock waves is accurately captured using the HLLC scheme. By analyzing the spatiotemporal characteristics of temperature, velocity, pressure, and flow field structures, this study focuses on revealing the triggering and evolution of DDT under four distinct blockage modes. The results indicate that the coupling effect between the superimposed shocks and the flames is significantly enhanced under the central blockage mode, making it most prone to inducing hydrogen DDT. The incident wave and the reflected wave from the blockages accelerate flame propagation and generation of hot spot through squeezing. As local temperature and pressure gradients increase, the overdriven detonation velocity significantly rises, while the steady-state detonation velocity approaches consistency. This indicates that the blockage mode primarily affects the activation of DDT, with limited effect on steady-state detonation propagation.