Preliminary Research No Hypersonic Axisymmetric Curved Compression System

The aerodynamic design of compression surface in hypersonic inlet is essentially an organization of the wall and shock system, so the key problem is how to efficiently compress coming flow with shock waves or compression waves. This paper investigated a new method of designing axisymmetric compression surface, which can generate physical compression wall according given pressure distribution. In the designing, a step by step process developed from theory of rotational characteristics and Taylor‐Maccoll(T‐M)equation, is repeatedly applied according to the assigned pressure distribution, and ultimately the compression wall and the whole flow field can be obtained. The compression wall, a concave surface, would generate a concave shock wave. The compression efficiency is higher, because the free stream can be compressed by both shock wave and, more isentropic compression waves.The flow characteristic of compression surface with constant pressure gradient was investigated. The result shows, the flow is rotational; along different streamlines, the pressure distribution, Mach number distribution and the density distribution is different; and similarity law can not be satisfied between different streamlines.The influence of the pressure distribution on the compression performance was specially investigated, due to the importance of the pressure distribution to the shape and property of the compression surface. The pressure distribution rules can be various much, and this paper proposed a piecewise rule. The surface is divided into front, middle and rear segment, and each has linear pressure gradient distribution, in addition the entire pressure distribution function is kept continuous and derivative, then totally 5 independent parameters are needed. Under this pressure distribution rule, influence of the 5 designing parameters on the compression surface performance was studied. The result indicates, under the designing condition, total pressure recovery of the surface decreases, while pressure ratio, drag coefficient, total compression angle and length‐height ratio all increase with the increase of each parameter, of which K2 and K3 have most huge impact; and the flow are not very sensitive to the coming flow condition.Based on above results, a surrogate model was established, and then single‐objective and multi‐objective optimization were carried out using genetic algorithm, ultimately several Pareto set were obtained. A new hypersonic axisymmetric inlet was designed using one of the optimal solutions. The new inlet was investigated through numerical simulation, and was compared with the normal triple‐cone and cone‐isentropic inlet. The numerical simulations indicated that, under the present condition, the inlet length can be reduced remarkably, about 11.8% and 26.8% of the triple‐cone and the cone‐isentropic inlet respectively; under the design point, total pressure recovery of the new inlet is approximately the same as triple‐cone inlet; under the start point the flow capture ratio is improved by 19.3% and 24.2% than the triple‐cone and cone‐isentropic inlet respectively, and is not very sensitive to the change of coming flow Mach number; under the start point the total pressure recovery is improved by 6.32% and 4.99% than the triple‐cone and cone‐isentropic inlet respectively; the new inlet has better performance at angle of attack than normal inlet, and is not very sensitive to the change of attack angle. Generally speaking, the new inlet has a superior overall performance.