Thermodynamics and wave processes in high Mach number propulsive ducts

Analysis of the flow in a propulsive duct indicates that, at high Mach numbers, the thermodynamic energy of the fluid is delivered directly into compression and expansion waves. The importance of the resulting wave phenomena is explored by considering the net thrust delivered by a two dimensional convergent-divergent duct with a simplified, planar heat addition zone. It is found that net thrust is reduced when operating at other than the design Mach number, an effect which is most severe for Mach numbers exceeding the design value. An idealized model is developed, involving a self-induced heat injection cycle, and it is seen that the waves produced by this cycle can be the dominant agency in producing thrust.