Ground-based Simulation Method For The Flow Characteristics Of BLI Inlet And Preliminary Experiment

Since BLI inlet is highly integrated with the airframe without any boundary layer diverter, it is particularly suitable for the blended-wing-body aircraft. In this paper, a BLI inlet is designed, and the flow characteristics within it are numerically studied. Besides, a subsonic test bed with two flowpaths is built for experimental study of the BLI inlet. The test bed has the ability to simulate the actual flow, which is verified by the CFD results. Some preliminary experiments are carried out on this test bed, and the experimental results agree well with the computational results in general.Both of the computational and experimental results show that the boundary layer ingestion makes the flow structure different from the conventional S-shaped inlet without boundary layer ingestion. A typical flow phenomenon, which is caused by the blunted cowl body/boundary layer interaction, is observed at the entrance of the inlet. The number and location of the saddle points as well as the separation lines in this region change with the outlet Mach number. In the diffuser, the boundary layer ingested gradually accumulates at the bottom wall, and then the secondary flow develops into a vortex-pair at the aft of the second bend. Some fluid within the boundary layer is pulled towards the core flow by the vortex-pair, which develop into a low total pressure region on the AIP plane. Furthermore, the boundary layer accumulates more seriously and the effects of the vortex pair get stronger under lower outlet Mach number, higher freestream Mach number, or more boundary layer ingestion, resulting in a lower total pressure recovery coefficient. Besides, as the outlet Mach number increasing, the total pressure recovery coefficient of the BLI inlet increases at first and then declines, while it will decreases monotonously in the conventional S-shaped inlet.In addition, both computational and experimental results indicate that the test bed can simulate the actual flow characteristics of the BLI inlet. And different freestream Mach number, outlet Mach number and amount of the boundary layer ingestion can be achieved by this test bed. Therefore, the design of the test bed is proved to be successful.