Observation of the Flowfield and Flame around the Ram-Accelerator Projectile Traveling near the CJ Detonation Speed

Abstract

The combustion and thrust characteristics of a ram accelerator in a case where the projectile speed was close to the Chapman-Jouguet (CJ) detonation speed were experimentally investigated. Methane-air mixtures with different equivalence ratios were used in the experiments. In the case of the fuel-lean condition, positive net thrust was not obtained although the combustion region was kept behind the projectile. That is to say, the combustion near the projectile was extremely weak. In the case of the equivalence ratio of unity, a flamelet attached to the projectile shoulder was observed. The flamelet generated the secondary shock wave. The secondary shock wave induced the ignition of the mixture, and the combustion occurred near the tube wall, thus enhancing the combustion of the nearby projectile. The results indicate that the appropriate configuration of the flame can drastically enhance the thrust.