Propagation of gaseous detonation in spatially inhomogeneous mixtures

Abstract

In advanced detonation engines for propulsion and in strong accidental explosions with detonation development, spatially inhomogeneous mixtures may occur which can greatly affect the detonation propagation. In this study, detonation propagation in spatially inhomogeneous mixtures is investigated via numerical simulation considering detailed chemistry. The two-dimensional (2D) periodic sinusoidal distribution of reactant concentration is introduced in the inhomogeneous region. The emphasis is on assessing the effects of such spatially inhomogeneous mixture on local explosion and subsequent detonation development. It is found that successful detonation propagation always occurs in the spatially inhomogeneous mixtures with 2D periodic sinusoidal distribution of reactant concentration. This is interpreted through the formation and collision of curved shocks, local autoignition, and explosions happened in the first sinusoidal period. Moreover, the effects of wavelength and amplitude of sinusoidal distribution on the cellular structure and detonation speed are assessed. It is found that the detonation speed decreases as both the wavelength and amplitude increase. Unlike the detonation speed, three modes of the cellular structure, respectively, from the original cellular structure and local explosion are identified depending on the values of wavelength and amplitude. Furthermore, the position of the first local explosion is always found to be located in the high reactivity zones of the second half of first sinusoidal period. Furthermore, comparison between simulation results for one-dimensional (1D) and 2D periodic sinusoidal distribution of reactant concentration indicates that the formation of curved shocks and their collision caused by 2D sinusoidal distribution are crucial for successful detonation propagation in the inhomogeneous region. The present study helps to understand the detonation propagation in inhomogeneous mixtures.