デュアルベルノズル内部における剥離点の制御

Abstract

Dual bell nozzle has a structure that combines two bell nozzles with different expansion ratios, consisting of a base nozzle with a low expansion ratio and an extension nozzle with a high expansion ratio. In this paper, axisymmetric two-dimensional unsteady numerical calculations were performed using two types of dual bell nozzles. There was a difference whether there is a step at inflection point of the nozzle, and the conditions for controlling separation inside the nozzle and creating a stable flow were investigated. The step size is 0.01 times the throat radius. Grid points of the nozzle were 800 in the axial direction and 200 in the radial direction. The static pressure at the outlet was set to 3kPa, and the total pressure at the inlet was linearly increased from 3kPa to 600kPa in 0.3 second. Injection of nozzle inflection point with step were set to no injection, 50 kPa and 100 kPa. The working fluid was ideal gas air. The calculation results were arranged by the nozzle pressure ratio (NPR), and the thrust coefficient and the wall pressure were compared. As a result, it was found that adding a step to the inflection point of the dual bell nozzle has little effect on the nozzle performance. In addition, the separation point inside the nozzle could be controlled by the injection from the nozzle inflection point.