STUDY ON THE COMBUSTION IN RAM ACCELERATOR

冲压加速器是近年来开始研究的，有望作为空间飞行器的经济发射装置，因为它可以在没有火箭助推器的情况下以很高的速度发射。它也有望成为超声速燃烧研究的基础实验装置。在本研究项目中，我们制作了一个小型的冲压加速器，使我们能够光学地观察燃烧流场，以获得其基本数据，因为我们认为对冲压加速器的认识水平还没有达到实际应用的水平。我们试过让它作为一个撞击加速器工作，当抛射物的初始速度不是很高初始压力也不像世界上其他撞击加速器那么高。我们还编制了一个计算机程序，对弹丸周围燃烧流场进行了数值模拟，并与实验结果进行了比较，以期为冲压加速器的研制提供参考。为了给弹丸提供足够的初始速度，我们研制了一种轻气炮，以加速弹丸。我们研制的轻型气枪是由气体爆轰驱动的，容易获得高压。我们开发的冲压加速器的下一个部分是打破发动机的装置，并从管中疏散驾驶员气体。由于这些发展，弹丸可以满足起动条件的运动。很明显，要得到稳定的燃烧，起动条件的范围很窄。初始速度有一个下限，这取决于压力和气体混合物的组成，以及要点燃的弹壳的大小。由于ram加速器的运行参数太多，目前还不能完全确定其启动条件的范围。数值模拟帮助我们在这些起始条件下进行实验。为了模拟初始非定常启动过程，必须求解相互独立运动的弹丸和弹壳周围燃烧的高速气流。采用解自适应多级网格细化方法和移动边界技术，得到了与实验结果定性一致的数值解。少

Ram acceletator is recently begun to study expecting the possibility to use as the economic launcher of space vehicles, for the projectile can be launched with very high speed without booster rocket motor. It is also expected as the fundamental experimental apparatus to study on the supersonic combustion. In the present reserch project we made a small ram accelerator, which allowa us optically to observe the burning flow fields in order to get its fundamental data, for we considered as the understanding level on the ram accelerator is not ready for its practical use. We have been tried to make it work as a ram accelerator, when initial velocity of the projectile is not so high and when initial pressure is not so high as other ram accelerators in the world. We have also developed a computer program to simulate numerically the burning flow field around the projectile in order to help our development of the ram accelerator by comparing with our experimental results.The development of our … More ram accelerator is started by that of a light gas gun to give the projectile enough initial speed. The light gas gun we developed is driven by gaseous detonation, which is easy to get high pressure. The next parts of the ram accelerator we developed are the apparatus to break a sabot and to evacuat the driver gas from the tube. As a result of these developments, the projectile can travel satisfying the conditions to start. It is cleared that the range of starting conditions is very narrow to get stable combustion. There is a lower limit of initial speed, which depends on the pressure and the composition of the gas mixture as well as the size of the sabot to ignite. As there are so many parameters to run the ram accelerator, we could not complete to decide the range of its starting conditions up to now. The numerical simulatios help us to do experiments on these starting conditions. We have to solve the burning high speed gas flow around the projectile and the sabot to ignite, which move independently each other, to simulate the initial unsteady starting processes. We got the numerical solutions in qualitative agreement with the experiments, using the solution adaptive multilevel grid refinement method and the moving boundary technique. Less