STUDY ON THE COMBUSTION IN RAM ACCELERATOR

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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