Pressure Forces on Variable Conical Nozzles: A Theoretical Study of Pressure and Turning Moment Distribution on Turbojet Engine Reheat Systems

REHEAT systems for turbo‐jet engines employ variable area convergent nozzles, and modern developments have produced nozzles made up of a series of flaps or fingers, as shown in fig. 1. These flaps have to be supported against the internal gas load to maintain a given area. The turning moment on each flap is usually balanced by a single element through a mechanical linkage; the element may take the form of a rod in tension or a shaft in torsion. This note provides a theoretical study of the nature of this load. In addition, the concept of frictional forces is introduced and a method developed for calculating the forces prevailing in flight, provided that two constants are determined from sea level test results.