Influence of Variable Blocking Ratio on DDT Process

Abstract

The influence of a variable blocking ratio on the DDT process is investigated through numerical simulation and experiment. Two dimensionless parameters, the average blocking ratio (BR¯) and the blocking ratio change rate (α), are specified to characterize the blocking ratio of obstacles. Four arrangements are utilized to describe the variation trend of the blocking ratio in a combustor. The main results are as follows: The obstacles can stretch the flame surface and facilitate reflection and diffraction of shock waves, which causes the acceleration of the flame front. The “hot spot” plays a vital role in the formation process of detonation waves. The overdriven detonation waves generated from “hot spots” promote the energy in the primary reaction zone, stimulating the formation of self-sustaining detonation. Compared with the fixed blocking ratio arrangement, the variable blocking ratio of obstacles can shorten the DDT distance. When BR¯=0.43, |α| = 0.03, and the variation trend (0.52–0.34–0.49) is adopted, the minimum DDT distance is obtained in numerical and experimental results. This paper can help with the design of detonation combustors in the future.

Keywords

• PDE
• DDT
• variable blocking ratio