Numerical Study of the Detonation Structure in Rich Acetylene-Air Mixtures

A numerical simulation of the detonation propagation process of acetylene-air under fuel-rich conditions is carried out using a reduced acetylene reaction model. The loose coupling method is used to solve the conservation equations with source terms. The flow is solved explicitly using a gas kinetic scheme, and the chemical reactions are solved implicitly. The numerical results show that the oxidation reaction is the chain initiation in the self-sustained detonation propagation process in rich acetylene. The self-decomposition reaction of acetylene provides the energy to maintain the coupling between the shock wave and the chemical reaction zone. The results show that the initial induced reaction is still an oxidation reaction due to the low activation energy of the oxidation reaction under the condition of low oxygen content. The intensity of the transverse wave is affected by the acetylene concentration. The post-detonation disturbance of temperature is mainly affected by the strength of the tail of transverse wave and the area of the unreacted pocket. With the increase of acetylene concentration, the self-decomposition process of acetylene increases the intensity of the transverse wave tail and improves the degree of temperature homogenization. This creates a formation-fragmentation-regeneration cycle of polycyclic aromatic hydrocarbons. This process changed the branching ratio of polycyclic aromatic hydrocarbons with different structures and delayed the formation of polycyclic aromatic hydrocarbons. When the acetylene concentration is low, the region where the dominant temperature after detonation is 1500 ~ 2500 K provides a favorable environment for the growth of polycyclic aromatic hydrocarbons.