Investigation On Supersonic/Hypersonic Curved Compression System With Isentropic Compression Wave Decentralization-Intersection

In order to improve the wall pressure and Mach number distribution of the conventional isentropic surface having focused isentropic compression waves, a detailed study is performed on the new curved compression system with isentropic compression waves decentralization-intersection by theoretically analysis, numerical simulation and wind tunnel testing.Firstly, a new curved compression system with controlled isentropic compression degree along the flow direction is investigated using the coordinate transformation theory through analyzing the conventional isentropic surface design methodology and flow field characteristics. The special compression surface is parametric studied and compared with the conventional geometric truncated isentropic surface. Results show that the compression surface can produce decentralized and not focused isentropic compression waves. These waves converge orderly. The compression surface length is shortened obviously and maintains the isentropic compression flow characteristic. Meanwhile, its wall pressure and Mach number distributions are improved.The isentropic compression waves decentralization and convergence are determined by the curved surface. Therefore, the curved compression system with given the wall pressure rise law is investigated using the rotational method of characteristics, and an S type pressure rise law is proposed. Its front pressure gradient change slope is larger, but the terminal slope decreases gradually towards zero. The surface end will not appear larger adverse pressure gradient. The surface using S type pressure rise law is applied to design two-dimensional inlet. At uniform and non-uniform conditions, the performance is compared with normal compression inlets under the same design conditions. Results show that the external surface length can be shortened effectively by using curved shock which is not insensitive to the Mach number variation and causes less loss. So the off-design performance is improved. Moreover, the performance and flow distortion are slightly influenced by non-uniform flow.In order to improve the wall Mach number distribution of isentropic surface, the curved compression system with given the wall deceleration law is investigated directly from the effect of deceleration function. The wall Mach number linear and quadratic distribution normal deceleration laws are studied according to isentropic surface coordinate transformation. Then a deceleration law with wall Mach number using two stages distribution is developed. Curved surfaces with different wall deceleration laws are used to design hypersonic two-dimensional inlets, and compared with normal three-wedge and S type pressure rise law inlet under the same design conditions. Results show that the curved surfaces with wall Mach number quadratic and linear distribution have high similarity with isentropic surface and X axis coordinate scaling factor Sx=0.5 surface respectively. It is easier to control the flow direction compression degree change, when the deceleration law is divided into two stages. Especially, curved surface with controlled wall deceleration law combines mainly isentropic compression with little shock compression to compress airflow, and its wall pressure gradient changes relatively moderate. The inlet external surface length is shortened and the loss is reduced, so its overall performance is increased significantly.In order to take advantage of curved surfaces with controlled wall pressure rise law and deceleration law, the curved compression system with wall pressure and Mach number complex distribution is investigated from the two aspects: geometric and aerodynamic combination. The two kinds of combination surface are compared and used to design inlet based on the reference inlet. Results show that the advantages of curved surface designed by a single parameter are performed using geometric and aerodynamic combination. The wall parameter distributions are improved effectively and tend to be more reasonable. The inlet with combination surface can reduce the flow loss, so the overall performance is increased significantly.Comparison of several typical curved surfaces, the curved surface with wall Mach number linear distribution is applied to improve topwall and sidewall of reference three-dimensional sidewall compression inlet under the same configuration, total compression and sidewall compression mode, and compared with the reference inlet. The curved compression sidewall inlet with both topwall and sidewall using curved surface is obtained. Numerical results show that the inlet combines isentropic compression with weaker shock compression to compress airflow, and the spillage window is smaller. Therefore, the inlet has higher compression efficiency and flow capture capacity in the entire operating range of Ma=4~7. Experimental results show that topwall and sidewall pressure distribution have curved surface characteristics at design and off-design conditions. At Ma=6, the inlet has a total pressure recovery of 0.544, an exit Mach number of 2.70, a compression ratio of 28.