Shock tube validation experiments for the simulation of ram-accelerator-related combustion and gasdynamic problems

This paper presents the work done at the ISL for validating the shock tube as a useful tool for simulating ram-accelerator-related combustion and gasdynamic phenomena. We were able to show that, with a specially devised expansion shock tube, an explosive gas mixture can be accelerated to a superdetonative velocity without autoignition. By reducing the driver length, a test flow of decreasing velocity was generated enabling the observation of all three detonative regimes of interest namely super-, trans- and subdetonative in only one experiment. Pressure measurements in a combustion test chamber provided the ignition conditions for different gas mixtures and varying flow geometry. An unexpected sharp onset of the ignition was found. The experiments in the shock tube will be able to support and optimize the operation of two ram accelerator facilities, a small and a large one that are presently being built at the ISL.