Unsteady Combustion and Oblique Detonation Induced by Hypersonic Projectiles Flying in Hydrogen-Air Mixtures

Projectiles were fired at hypersonic speeds into stoichiometric H2-air mixtures. The flowfields around the projectiles were visualized using a high-speed framing schlieren technique. We comprehensively studied oblique detonation and oscillating combustion phenomena around the hypersonic projectiles, where the varied parameters were the projectile velocity, projectile-nose shape, projectile diameter and initial gas pressure. We studied, in detail, the dependence of the oscillating-combustion cycles on the projectile velocity. It has been found that the observed four oscillation modes are composed of three fundamental modes. We compared the present experimental results with the numerical results of Matsuo, Fujii and Fujiwara, and discussed a mechanism generating oscillating combustion.