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发动机实际比冲的预计,是一个急待解决的问题。对比冲效率影响最大的因素来自两个方面。一方面来自推进剂;其中铝粉的燃烧效率,以及燃烧生成的Al_2O_3粒子对比冲有很大影响。另一方面来自喷管结构,其几何形状及壁面附面层状态也对比冲有很大影响。美国Hercules 公司和Thiokol 公司拟制了一套比冲损失的分析计算方法,考虑了除铝粉燃烧效率以外的几项主要损失。其中尤以两相流的损失和扩散损失为最大。对于推进剂含铝量在18～19%以下,工作压力不太低、燃气停留时间在20毫秒以上的发动机,这一方法是适用的。理论比冲预计值与实测值相差约为0.6%对于含铝量较大的推进剂或燃气停留时间较短的发动机,铝粉燃烧效率可能成为影响比冲效率的重要因素。对于多级火箭的顶级发动机往往需要考虑这一问题。但是目前关于铝粉在发动机流场中燃烧的规律性还认识不足,理论研究工作还不能提供有力的设计准则,需要做进一步的工作。本文综合介绍了有关的几篇国外资料,供有关人员参考。
The actual engine specific impulse is an urgent problem to be solved. The factors that make the most impact on efficiency are from two aspects. On the one hand from the propellant; which burning efficiency of aluminum powder, as well as the combustion of Al 2 O 3 particles produced by the contrast has a great impact. On the other hand from the nozzle structure, its geometry and wall surface layer status also has a significant impact on contrast. Hercules and Thiokol companies in the United States prepared a set of analytical calculations for specific impulse losses that take into account several major losses beyond the efficiency of aluminum powder combustion. Among them, the loss of two-phase flow and the diffusion loss are the largest. This method is suitable for engines where the aluminum content of the propellant is below 18-19%, the working pressure is not too low, and the gas residence time is above 20ms. The theoretical impulse predicted value and the measured value difference of about 0.6% For the larger amount of aluminum propellant or gas residence time shorter engine, the combustion efficiency of aluminum powder may be an important factor affecting the specific impulse efficiency. For the top stage multi-stage rocket engine often need to consider this issue. However, at present, the regularity of the combustion of aluminum powder in the engine flow field is still lack of understanding. Theoretical research can not provide strong design criteria and further work is required. This article gives a comprehensive introduction of several relevant foreign materials for reference of relevant personnel.