固体火箭喷管中的烧蚀控制机制

对碳基材料,以热化学烧蚀三方程模型为基础,在考虑粒子侵蚀,烧蚀与传热耦合的情况下,进行了全喷管烧蚀控制机制的研究,喷管中的烧蚀控制机制有化学动力学控制,扩散控制和双控制三种机制。通过研究,得到如下结论:1)对于由扩散控制和化学动力学控制确定的烧蚀率相差约20倍以上时,可以简化为按烧蚀率低的一种控制机制来计算;否则,应当按既考虑扩散控制,又考虑化学动力学控制的双控制机制来计算。2)在固体火箭喷管中,大体上喉部和扩张段的烧蚀是化学动力学控制的,而收敛段的烧蚀是由扩散控制的。3)由于在收敛段由两种机制控制的烧蚀率相差较小,因此,在收敛段的烧蚀率应当按双控制机制来计算。喉部和扩张段的烧蚀可简化为动力学控制机制。

ABLATIVE CONTROL MECHANISM IN SOLID ROCKET NOZZLE

According to the aerodynamic-thermochemical ablation model, the ablative mass calculation equations are deduced. According to the transient equivalent thermo-capaci-ty heat-conduction equation, its implicit scheme is deduced under the condition of ablative moving boundaries for multi-layer construction of nozzle. Then, these equations are coupled-ly solved. By study, authors find that there are different ablative control mechanisms on different positions of nozzle. kinetics, diffusion or double control mechanism, and following conclusions may be obtained; ( 1) It is important to divide ablative mechanisms into diffusion, kinetics or double control mechanisms for ablative calculation in nozzle. (2) When the difference between ablative rate determinded by diffusion and that by ki-netics control mechanisms is equal to or more than 20 times, the ablative rate may be simpli-fiedly calculated according to that control mechanism which brings about lower ablative rate. (3) In solid rocket nozzle, roughly, the ablation is controled by diffusion in convergent portion, but by kinetics in throat and divergent portions. (4) In solid rocket nozzle, the ablative rates in throat and divergent portions may be simplif iedly calculated by the kinetics control mechanism, but the ablative rate in convergent portion must be calculated by double control mechanism.