Numerical study on transient regression rate and combustion characteristics of segregated AP-based oxidizer/TAGN-based fuel

In the present study, a two-dimensional combustion model is established to simulate transient flow and combustion characteristics of a segregated oxidizer/fuel solid motor (SOFSM). A detailed gas-phase reaction kinetic mechanism with 35 species and 190-step reactions is developed to describe the gas-phase combustion process between AP-based oxidizer and TAGN-based fuel. The effects of mass flux and initial temperature of inflow oxidizer gas on the transient flow and combustion characteristics of the TAGN-based fuel are numerically investigated. With the mass flux of inflow oxidizer gas increasing from 249 kg·m−2·s−1 to 995 kg·m−2·s−1, the maximum spatially averaged regression rate of the burning surface of TAGN-based fuel increases by almost 200 % and the combustion efficiency first increases and then decreases with a maximum combustion efficiency of 94.3 % at the mass flux of 442 kg·m−2·s−1. With the initial temperature of inflow oxidizer gas increasing from 1000 K to 1750 K, the maximum average regression rate of the burning surface of TAGN-based fuel increases by around 10 %. Meanwhile, the combustion efficiency increases from 88.38 % to 95.8 %. During the combustion process (almost 3 s), the spatially averaged regression rate remains basically stable from 0.5 s to 2 s and increases slightly from 2.0 s to 3.0 s for given mass flux and initial temperature, indicating the combustion process is basically stable under the studied conditions. The results also show that during the transient combustion process, a large vortex first appears and then is split into a major vortex and a small one in the post-combustion chamber. With the increase of the mass flux and initial temperature of inflow oxidizer gas, the size of the vortex increases while the center position of the vortex moves towards the burning surface, which significantly enhances the mixing process and increases combustion efficiency.