In this study, wave processes in pulse detonation facility are numerically simulated to gain basic understanding on the PDEs working mechanism. A detailed aspect of wave motion in one PDE cycle is obtained and can be used as the basis of PDE timing system. It is also understand that reflected rarefaction fans are strong enough to decrease the reaction product pressure at the closed end to a low level, but the temperature is still so high that auto-ignition of fresh gas mixture may be induced, therefore, a pure air purge must be employed to separate the fresh gas mixture from the high temperature products.