Study on Stabilization of Supersonic Combustion Using Ram Accelerator

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The main objects of the present research are to find the properties on the stability of the flame holding in supersonic flows of the combustible gas mixtures, as well as to show that the ram accelerator works as a powerful device to study the supersonic combustion. The ram accelerator we have developed in Hiroshima University is designed as a tool to make fundamental studies on the interactions of combustion with the shock waves, the boundary layer, and so on, so that tube has a rectangular cross section where parallel glass windows are mounted for optical observations. Then, we have got pictures of the flames in the supersonic flows, and the burning flow fields are made clear for various conditions. Flame holding properties are investigated for the different wedge angles and shapes of the side bodies of the projectile, or for the effects of boundary layer thickness. It is also shown that the back-step of the projectile is the most important part as a flame holder. A shock wave is always formed in front of the leading flame, which means the flame exists only in the subsonic region. The flow fields are so complicated that the numerical simulations are necessary to study the supersonic combustion. The computer program is also developed including full kinetic reactions of the CH_4-O_2-CO_2 mixtures, comparable to the experimental observations. Because of the practical necessary, CH_4-O_2-N_2 mixture system is to be used in experiments and the numerical simulations. The ram accelerator is working with the sub-detonative speed of the projectile, though super-detonative mode is also important. The properties of the detonations are also recently studied as a new propulsive device as a pulse detonation engine.