Abstract: In order to enhance the stealthy ability and reduce the drag of an aircraft, the combination of the stealthy fuselage of plane abdomen with a submerged inlet is a good approach. But the free stream is hard to enter the submerged inlet on the plane surface according to previous research. Therefore, for the improvement of the aerodynamic performance of this type inlet, effects of three important entrance parameters on the performance are investigated by wind-tunnel experiments and some useful conclusions are obtained. Then by selecting a group of suitable entrance parameters, a submerged inlet with the trapezoid entrance on the plane surface is designed and verified by wind tunnel tests. Results indicate:(1) The vortices generated by the two side edges and the transverse pressure gradient near the entrance caused by the ramp angle are two main forces which drive the free stream to enter the inlet and affect the inlet's performance apparently. Additionally, suitable aft lip can contribute to the reduction of the total pressure distortion by adjusting the distribution of the total pressure at the exit of the submerged inlet. (2) By selecting the ramp angle 23°, the side edge angle 4° and characteristic parameter of aft lip 30°, a submerged inlet on the plane surface is designed and validated.When Ma₀=0.7,α＝-2°~8°,β＝0°~2°, the total pressure recovery coefficient ranges from 0.920 to 0.952 and the circumferential total pressure distortion index ranges from 1.142% to 2.237%, which shows clearly that the performance of the submerged inlet is acceptable. (3) The increase of attack angle is benefit to the total pressure recovery coefficient and the circumferential total pressure distortion, while small yaw does not bring obvious influence on the performance of the inlet.

Key words: inlet, submerged inlet on the plane surface, entrance parameter, side edge angle of the entrance, ramp angle, characteristic parameter of aft lip, total pressure recovery coefficient, circumferential total pressure recovery distortion index