A numerical scheme for calculating hypersonic flows involving shock-induced combustion is discussed. The analysis is limited to inviscid flow and includes chemical nonequilibrium and real-gas effects. Two types of flows are considered. First, the hypersonic, exothermic blunt-body flow problem is examined for mixtures of Hi/Oi and Hi/air, and the numerical results are compared with experimental results. Second, a hypervelocity mass launcher concept known as the "ram accelerator" is investigated in the velocity range of 5-7 km/s. Temperature contours and the distribution of various physical quantities along the ram accelerator projectile surface and tube wall are presented for a 14-deg nose projectile and for a gas mixture of 2Hi + Oi + 5He.
Abstract. Experimental investigations on tile propulsive modes of the ram accelerator are reviewed in this paper. The ram accelerator is a ramjet-in-tube projectile accelerator whose principle of operation is similar to that of a supersonic air-breathing ramjet. The projectile resembles the centerbody of a ramjet and travels through a stationary tube filled with a premixed gaseous fuel and oxidizer mixture. The combustion process travels with the projectile, generating a pressure distribution which produces forward thrust on the projectile. Several modes of ram accelerator operation are possible which are distinguished by their operating velocity range and the manner in which the combustion process is initiated and stabilized. Propulsive cycles utilizing subsonic, thermally choked combustion theoretically allow projectiles to be accelerated to the Chapman-aouguet(C-J) detonation speed of a gaseous propellant mixture. In the superdetonative velocity range, the projectile is accelerated while always traveling faster than the C-J speed, and in the transdetonative regime (85-115 % of C-J speed) the projectile makes a smooth transition from a subdetonative to a superdetonative propulsive mode. This paper examines operation in these three regimes of flow using methane and ethylene based propellant mixtures in a 16 rn long, 38 mm bore ram accelerator using 45-90 g projectiles at velocities tap to 2500 m/s.
This investigation of the use of cryogens as energy storage media for zero emission vehicles has found that using liquid nitrogen to liquefy the working fluids of one or more closed Rankine power cycles can be an effective means for increasing motive power. System configurations are presented which can realize a specific energy greater than 400 kJ/kg-LN 2 (110 W-hr/kg-LN 2 ) without relying on isothermal expanders. A zero emission vehicle utilizing such a propulsion system would have an energy storage reservoir that can be refilled in a matter of minutes and a range comparable to that of a conventional automobile.
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