考虑自然对流的某固体火箭发动机慢速烤燃特性数值分析

针对某高氯酸铵/端羟基聚丁二烯(AP/HTPB)推进剂固体火箭发动机,采用两步总包反应描述AP/HTPB 的烤燃过程,建立了考虑发动机空腔自然对流的二维轴对称烤燃模型,对加热速率分别为 3.6、7.2 和10.8 K/h 时火箭发动机的慢速烤燃行为进行了数值预测,研究了该火箭发动机的热安全性问题。结果表明,固体火箭发动机空腔内的自然对流对 AP/HTPB 推进剂的着火温度、着火延迟期和着火位置有一定影响,在热安全性精确分析中不可忽略。3种加热速率下,AP/HTPB 推进剂的最初着火位置均出现在药柱肩部的环形区域内,3种加热速率对应的着火延迟期、着火温度及着火时壳体温度分别为30.71、20.06、18.68 h,526.52、528.10、530.64 K,和479.56、496.82、508.77 K。随着加热速率的增大,烤燃响应区域向推进剂与绝热层交界处移动,着火位置的二维截面由椭圆形变为半椭圆形。

Numerical analysis of slow cook-off characteristics for solid rocket motor with natural convection

A two-dimensional axisymmetric model about slow cook-off of solid rocket motor was established, where the process of slow cook-off for ammonium perchlorate/hydroxyl-terminated polybutadiene (AP/HTPB) propellant described by a two-step global chemical reaction kinetics, and natural convection of motor cavity was considered. The purpose of this paper is to study the thermal safety problems of solid rocket motor with ammonium perchlorate/hydroxyl-terminated polybutadiene (AP/HTPB) propellant. Numerical predictions of slow cook-off behavior for a motor were conducted at the heating rate s of 3.6, 7.2 and 10.8 K/h, respectively. The results show that the natural convection in the cavity of the solid rocket motor has a certain influence on the ignition temperature, ignition delay of the AP/HTPB propellant, and cannot be ignored in the accurate analysis of thermal safety. At the three heating rates, the initial ignition position of AP/HTPB propellants appeared in the annular region on the shoulder of the propellant. The ignition delay period, the ignition temperature and the temperature of the shell at the three heating rates were 30.71, 20.06, 18.68 h; 526.52, 528.10, 530.64 K; and 479.56, 496.82, 508.77 K; respectively. With the increase of heating rate, the response area of the cook-off is shifted to the junction between the propellant and the insulation, and the two-dimensional section of the ignition position is changed from ellipse to semi-ellipse.