To analyze the influence of indirect initiation

a method was first established to evaluate the average cycle thermal efficiency of the system whose working fluid experienced different combustion processes in combustion chamber. Then

the thermal efficiency and deflagration to detonation transition (DDT) characteristics of two detonation tube models with different obstacles were investigated by the 2-D numerical simulations. The ratio of combustion wave run-up distance to DDT distance (defined as ξ) was also studied. The results show that: (1) the thermal efficiency of the pulsed detonation engine (PDE) model can be both influenced by the indirect initiation and different obstacles; (2) when ξ approaches to 1

the average thermal efficiency of the system is only 60% of ideal detonation cycle; (3) the effects of indirect initiation are weakened with the increase of ξ; (4) when ξ approaches to 1.5

the average thermal efficiency will reach 93% of ideal detonation cycle.