Computational investigation of oblique detonation ramjet-in-tube concepts

Abstract

Ramjet-in-tube techniques have been proposed to accelerate masses up to thousands of kilograms to velocities of 0.7-12.0 km/s by chemical means. CFD calculations for three oblique detonation ramjet-in-tube drive modes are presented; the operational velocities for the present results range from 3.5 to 10.0 km/s. The first drive mode achieves ignition on the reflection of the nose cone bow shock. The second drive mode relies on a sudden, steep, but small increase in projectile radius to initiate a detonation wave, following a deliberately gentle, gradual compression process. The third drive mode is similar to the second mode except that the projectile is thermally protected by flying it through a core of pure hydrogen gas surrounded by a detonable mixture. At optimum operating conditions, the thrust pressure ratios (defined as the effective thrust pressure divided by the maximum cycle pressure) for the three modes range from 0.12 to 0.30, and the efficiencies (defined as the thrust times the velocity divided by the rate of chemical energy release) range from 0.09 to 0.26. Tables of thrust pressure ratios and efficiency data and representative plots of the pressure fields around the projectiles are presented.