Modelling of Ram-Accelerator Flow Fields

Abstract

Dynamic phenomena in 'ram-accelerator', a ramjet-in-tube concept for accelerating projectiles to ultra high velocities, have been investigated analytically and compared with the experimental investigations reported in open literature. The projectile resembles the centrebody of a conventional ramjet, but travels through a stationary tube filled with a mixture of gaseous fuel and oxidizer. The energy release process travels with a projectile inside the accelerator tube. The characteristics of subsonic combustion, thermally-choked mode of propulsion, which is capable of increasing the velocity up to Chapman-Jouguet (C-J) detonation velocity of the propellant mixture used in ram-accelerator tube, have been studied. The ram-accelerator with a fixed diffuser area ratio operates with different initial velocities for different propellant mixtures. Propellant mixture with CO/sub 2/ as diluent is used for velocity range ~770-1150 m/S; propellant mixture with nitrogen as diluent is used for velocity range ~ 925-1450 m/s and that with helium as diluent is used for velocity range ~ 1500-2000 m/s. Mixtures of propellants with different diluents in varying degree of proportions, giving rise to different acoustic and C-J detonation speeds, have been investigated to evaluate their suitability in the ram-accelerator divided into several segments.