Abstract: A topmounted slotshaped inlet similar to that of an X47 vehicle is designed and numerically studied to obtain its flow structure and performance characteristics. Results indicate that due to rapid changes in duct width and longitudinal curvature the internal flow of the slotshaped inlet is unsatisfactory. The boundary layer accumulates near the top and bottom sides of the diffuser and even reverses at the top region of the duct aft part. When the free stream Mach number is 0.7 and the angle of attack is 0°, the total pressure recovery coefficient of the inlet is 0.975, and the totalpressuredistortion index reaches 0.484. In addition, the huge bump in the front of the duct fails to push the fuselage boundary layer away from the entrance of the inlet, whereas at positive angles of attack the leadingedge vortices on the upper surface of the forebody sweep aside part of the fuselage boundary layer, thus improving the quality of the entering flow and finally restraining the low total pressure regions at the bottom side of the exit plane. The results obtained may serve to provide direction for performance enhancement of this type of inlet.

Key words: aerospace propulsion system, slotshaped inlet, X-47, design, simulation