AP/HTPB推进剂微尺度燃烧特性的数值分析

为研究高氯酸铵/端羟基聚丁二烯(AP/HTPB)固体推进剂颗粒的微尺度燃烧特性,基于气固耦合,采用简化的两步总包化学反应动力学机理,建立了二维周期性三明治定常燃烧模型,采用FLUENT软件,数值分析了AP/HTPB的微观燃烧特性。结果表明,AP体积分数为0.75条件下,低压(0.4 MPa)时,AP/HTPB燃烧的总体火焰以预混燃烧为主,AP燃速低于HTPB燃速,随着压力升高,大于2.5 MPa时,火焰呈扩散结构,AP燃速高于HTPB燃速;压力越高,气相对固相的热反馈越强,耦合面上的温度和燃烧速率越高。气相的体积释放速率随着压力的增加而增加,放热区域收缩,相连的两个放热核心区分裂为两个独立的放热核心区。当燃烧压力不变(2.5 MPa),AP体积分数为0.7~0.95时,AP含量越小,则一个周期三明治单元中粘合剂HTPB的宽度相对越大,火焰面趋于分裂为两个狭长带状火焰面,温度随之递增。

Numerical Simulation of Micro-scale Combustion Characteristics of AP/HTPB Propellant

To study the microscale combustion characteristics of ammonium perchlorate/hydroxyl-terminated polybutadiene(AP/HTPB) composite propellant particle, a 2D steady state combustion model of a periodic sandwich unit was established based on gas-solid coupling, using simplified two-step global chemical reaction kinetic mechanism. The microscale combustion characteristics of AP/HTPB were numerically analyzed by FLUENT software. Results show that under the condition of volume fraction of AP as 0.75, at the low pressure of <0.4 MPa, the overall flame of AP/HTPB combustion is a premixed combustion and the burning rate of AP is lower than that of HTPB. With increasing the pressure, when the pressure is more than 2.5 MPa, the flame reveals in a diffusion structure and the burning rate of AP is higher than that of HTPB. The higher the pressure, the stronger the thermal feedback from gas phase to solid phase, and the higher the temperature and burning rate on coupled surface. The volume release rate in the gas phase increases with increasing the pressure, the exothermic region contracts and the two connected exothermic core regions split to two independent core regions.When the combustion pressure is constant (2.5 MPa) and the volume fraction of AP changes from 0.7 to 0.95, the smaller the AP content, the relatively larger the binder HTPB width in a periodic sandwich unit, the flame surface tends to split into two narrow and long strip flame surface, and the temperature increases with splitting.