Modeling of the Process of Motion of a Scramjet in the Atmosphere

Abstract

Physical and mathematical model and results of modeling of the processes proceeding in the channel of a scramjet and in the surrounding atmosphere are presented for Mach numbers of 6.7-10. The mathematical model is based on the gas dynamics equations written in the two-dimensional approximation taking into account combustion of a gaseous fuel. Investigations are performed for regions of the incoming supersonic flow, inside of the scramjet channel, and outside of it. Dependences of the total aerodynamic force projection onto the direction of scramjet motion on its speed and mass fuel supply rate are analyzed. The application of scramjets is most optimal for motion in high layers of the atmosphere with high speeds and Mach numbers of incoming flow of 6-10 (1). However, their development faces considerable technical difficulties caused by large thermal and dynamic loads on the scramjet body, unstable regimes of engine operation, and difficulties in fuel supply to achieve a high degree of fuel combustion in the supersonic air flow (2). The scramjet thrust is produced by fuel combustion in the supersonic flow in the combustion chamber. The schematic diagram of the scramjet model is shown in Fig. 1. The scramjet channel is converged at the inlet, has a constant cross section in its short part, and then is diverged at the rare part. After the interaction of the incoming supersonic flow with the protrusive frontal part of the scramjet, an oblique shock wave is formed in air. A series of shock waves is formed inside of the scramjet channel. The temperature and pressure in the combustion region increase, and the flow diverges in the nozzle creating a thrust. The gas dynamics equations are used to model gas dynamics processes in the channel of the model scramjet and the incoming flow (Fig. 1). It is assumed that a proper amount of gaseous fuel is injected into the volume V of the channel of width 1 m. The mass supply rate of the fuel is uniform throughout the volume. It is assumed that the times of fuel mixing and burning are much less than the time of air passage through the scramjet channel. With allowance for the above assumptions, the system of gas dynamics equations in the 2D approximation has the form