Inlets, exits, and cooling problems II : exits

摘要

The exit nozzle for air-breathing engines should perform two functions. First, it should control airflow in a manner consistent with optimum engine performance. Second, it should provide optimum thrust. These requirements will be satisfied if the nozzle has the correct throat and exit areas. If the aircraft is to operate over a range of flight speeds, nozzle geometry must be varied to obtain optimum performance at all speeds. For air-breathing engines, nozzle pressure ratio increases rapidly with flight speed at the higher speeds, so that, in general, large exit area variations will be required. This paper discusses the compromise between the mechanical complexity and weight of the variable nozzle and the performance penalties of the fixed nozzle. A Mach 4 turbojet and a Mach 7 ramjet are considered.