Numerical Simulation of Terminal Shock Oscillation in Over/Under Turbine-Based Combined-Cycle Inlet

Abstract

Abstract The physical characteristics of self-sustain shock oscillation and the key factors that affect the shock oscillation in turbine-based combined-cycle(TBCC) inlet were investigated through unsteady numerical simulation method in this paper. The terminal shock oscillation in the throat was caused by the separation bubble appeared in the lower wall of the turbojet flowpath. The angle of the splitter and the offset of the diffuser were the main factors which affect the characteristics of the shock oscillation. When the angle of the splitter increased from 0 deg to 12 deg, the frequency of terminal shock increased from 100Hz to 133Hz; while when it was greater than 18 deg the terminal shock oscillation phenomenon disappeared. Different offset of the turbojet diffuser affect the motion of terminal shock in the inlet. When the y-coordinate value of the control point (ym) in the turbojet diffuser was smaller than 1.5, the shock oscillated in the inlet; when ym was greater than 2.0, the shock oscillation disappeared. The bleed in the diffuser was able to control the oscillation of the terminal shock.