Research On Form Surface Aerodynamic Optimization Method Of Ramjet Assisted Range Projectile Inlet

With the development of long range of projectile and rocket weapon, the extended range technology of the traditional hollow base projectile and base bleed shell can't satisfy the need of its firing range any more, so by applying ramjet to fulfill the range increase of projectile is studying and applying more and more. Inlet is an important part of ramjet assisted projectile, its performance will affect the ramjet thrust directly, so affects the fire range of projectiles. While form surface of the inlet is generally not regulated, thus inlet performance and projectile air resistance characteristic depend on form surface directly; the inlet is associated with the arc part of projectile, and arc-shaped part is one of the important resources of shell resistance, so it is very necessary to optimize form surface of inlet and arc-shaped part. Based on these factors, in this paper, a set of optimal design method about inlet form surface is built, and the specific contents are as follows:Firstly, in this paper, the geometric model of ramjet assisted projectile has been builded, and moreover the numerical simulation of the flow field inside and outside when ramjet engine stops working has been studied, and the resistance force of different parts in this situation has been analyzed. Thus three-dimensional numerical simulation of the inner flow field of air-inlet has been done when ramjet motor was working, and studied the structure of air-inlet inner flow field, and gives emphasis to the reinforcing rib, boundary layer and interference between shock-wave and boundary layer acting on the characteristics of air-inlet, in addition, analyzes the change law of air-inlet characteristics in different mach number of coming flow and different attack angle. The results gotten provide a theoretical basis to follow-up study.Secondly, the optimization design method based on one-dimensional fluid theory about form surface has been set up, and by using this method, single-objective and multi-objective optimization have been done to inlet form surface design parameters, by building the capability parameter mathematical model and the outer body resistance force mathematical model of supersonic multi-angle(multi-wedge) air-inlet, the total pressure recovery coefficients and crust resistance force of air-inlet have been deduced based on one-dimensional flow in air-inlet, and compile C language program to solve its value; Automatic optimizing platform has been built by integrating C language program with optimizing strategy, so accomplished the single target optimization of single-angle, double-angle, tri-angle and single-wedge, double-wedge, tri-wedge air-inlet. Comparing the optimization result with the result of Schittcowski, they accord with each other very well, and testify the result of optimization credible. The resistance force curve of ramjet projectile outer case has been given according to Fraenkel theory, building the mathematical model of outer case resistance, and studying the characteristics of outer body in fixed areas ratio and different ratio of areas. Based on those, multi-objective optimization was made on the design parameter of air-inlet form surfaces above, so the best design curves of different air-inlet have been attained.Thirdly, establishes the integrated optimization platform based on numerical simulation, put inlet parameterized model, fluid field simulation and optimization method together on the platform, achieves inlet form surface automated optimizing, and by utilizing this method, single-objective and multi-objective optimization has been done. Apply NURBS theory to design the inlet subsonic form surface, establish the optimization geometry model, make the air-inlet flow field numerical simulation results as the evaluate system, by applying special topology structure to partition the flow field, and succeed in avoiding the aberration of the air-inlet flow field grid in the process of updating; meanwhile by setting the monitor surface of shockwave, ensure the shockwave is locating at the throat in the process of fluid field iteration; by applying the method of optimization to optimize the single-objective and multi-objective air-inlet surface, so optimized inlet could greatly reduce the shell force and increase the field of fire by sacrificing less total pressure recovery coefficient.Finally, make the supersonic wind tunnel experiment of the inlet optimized, measure the internal surface static pressure of windward and leeward and the total pressure of air-inlet outlet when the mach number of coming flow was 2.5 and 2.0, shoot schlieren chart of the flow field, the result is consistent with the simulation result well, that indicates the simulation results can reflect the variety of static pressure and total pressure in air-inlet, so the optimization result based on numerical simulation is more reliable.