Objective To investigate the safety of solid rocket motor(SRM)when it was cook-off. Methods Finite element model of solid SRM was established, and the temperature distribution and the explosion delay time of propellant in fast cook-off mode and slow cook- off mode were computed. Results Propellant reached its critical temperature (352 ℃) after 47 h slow cook-off, while it reached its critical temperature (355 ℃) after 697 s fast cook-off. Conclusion It was proven that the thermal diffusivity in fast cook-off mode was greater than that in slow cook-off mode, while the temperature gradient had an opposite trend. The reaction position of propellant was different in the two different working modes when it reached critical temperature, and the thermal storage capacity of propellant was dependent on its thickness.%目的：研究固体火箭发动机遭受火烤时的安全性。方法建立发动机有限元模型，计算推进剂在慢速烤燃和快速烤燃工况下的温度分布和爆炸延迟时间。结果推进剂慢烤47 h后达到临界温度，其值为352℃；快烤推进剂加热697 s后达到临界温度，临界温度为355℃。结论推进剂在快速烤燃模式下的热扩散速率大于慢速烤燃工况下，但是温度梯度则相反。两种工况下推进剂达到临界温度后开始反应的位置不同，推进剂厚度决定了其储热能力。
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