Research On A Two-Dimensional Variable Geometry Supersonic Inlet

In order to break through the performance limit of conventional supersonic inlets and meet the higher requirements of ramjets,and realize the high efficiency flight of supersonic aircraft at wide Mach number,the design method and aerodynamic performance of a two-dimensional wide-speed-range supersonic variable geometry inlet are studied by combined theoretical analysis with numerical simulation.Firstly,aiming at the operating requirement of ramjets in wide speed range,the design of a widespeed-range fixed geometry inlet was completed.Based on the fixed geometry inlet,the bleed control in the internal contraction section was studied,and the influence of the bleed position on the self-starting performance and other main aerodynamic performances in the critical conditions of the inlet is obtained.The results show that the bleed position with the maximum critical pressure is not same to that with the highest self-starting capability of the inlet.For this study,when (?)=0.31,the self-starting performance is the highest.Whereas,when (?)=0.15,the critical pressure is maximum.Secondly,the preliminary design of a variable geometry inlet with integrated internal/external compression regulation is carried out,and the feasibility of a three-dimensional bleed control method with a vent hole on the side plate is verified.After demonstrating the preliminary design scheme,a optimization work for variable geometry inlet is conducted to eliminate the shortcomings of "low overall aerodynamic performance gain of the inlet due to the bleed position at the downstream of the throat,severe sudden expansion of the duct,discontinuity of profile transition".And the influence of throat position on the inlet performances was carried out.It is found that the aerodynamic performance of the variable geometry inlet increases first,then keeps relatively constant and finally decreases with the advance of the horizontal position of the throat station.In addition,compared with the preliminary design,the optimized scheme increases the critical pressure ratio by 29.5% and the total pressure recovery coefficient by 17.2% under shock-on-lip condition.Finally,the three-dimensional effects on the inlet performance were studied.It is found that the sidewall increases the proportion of low-energy flow in the throat station,and severe swept shock/boundary layer interaction occurs at the sidewall of the outer compression section at high Mach numbers.The vortices in the interaction zone causes the accumulation of low-energy flow in the corner or cause the low-energy flow near the sidewall to mix with the mainstream,which increase the total pressure loss and reduce the anti-pressure capability of the inlet.In order to improve the aerodynamic performance of the three-dimensional inlet,this paper proposes a type of “swept-cut open sidewall” based on the suppression of the strong swept shock/boundary-layer interaction in the external compression section.The numerical results show that after the optimization of the sidewall,the proportion of low-energy flow at the entrance of the internal contraction duct decreases significantly,and the flow uniformity at the throat station improves obviously.Compared with the baseline threedimensional inlet,the flow coefficient decreases by only 2.3%,but the critical pressure ratio increases by 29.8%,and the total pressure recovery coefficient increases by 28.5%.