Chapman-Jouguet Oblique Detonation Structure Around Hypersonic Projectiles

Abstract

How to generate a steady-state detonation around a hypersonic projectile in stoichiometric hydrogen-oxygen premixed gases is studied. The speed of the hypersonic projectiles was beyond the Chapman ‐Jouguet(C‐J) detonation speed. The e owe eld around the projectile was visualized by using a gate intensie ed charge-coupled device camera(single-frame schlieren picturesand OHradical self-emissionimages ). Threeparameters are varied:1 ) the projectile e ight length from diaphragm rupture location, 2 )the initial pressure of mixture below/above the critical pressureforsteady detonation initiation around a hypersonicprojectile, and3 )theprojectilespeed.Atthepressure condition below the criteria, the detonation structure is composed of three different shock and detonation waves, which appear just after a diaphragm rupture and evolve in time: an overdriven bow detonation wave, a strong detonation wave, and a diffracted shock wave. Their propagation after diaphragm rupture is investigated, and it is found that the C ‐J detonation wave moved away from the projectile and only a reactive bow shock wave remained around projectile far away from the diaphragm. At the pressure condition above the criteria, a steady oblique detonation wave was generated around the projectile as soon as the projectile broke the diaphragm. In this steady-state detonation-wave case, with respect to the e ow Mach number behind the wave front, the whole detonation wavewas divided into fourparts: 1 )strong overdriven detonation wave, 2 ) weak overdriven detonation wave, 3) quasi-C‐J detonation wave, and 4 ) C‐J detonation wave. It has been found that a rarefaction wave is generated at the projectile shoulder and that curvature of the wave has a signie cant effect on the structure of the detonation wave.