Experimental study on the flow and heat transfer mechanism of the pre-cooler in the hypersonic aeroengine

Anlysis of flow structure and loss behind a wall-cooled cylinder is of great significance for the study of tubular pre-cooler, which is applied to the air breathing hypersonic aeroengine. In this paper, the flow structure and loss of the wake behind a cooled cylinder are investigated by means of Paricle Image Velocimerty(PIV), which is in the condition of Re=5000,7000,8000, forced convection regime with Ri<0.1 as well as the temperature difference at 0K and 30K. Meanwhile, comparative anlysis is conducted on the time-averaged flow field and POD mode distribution for the condition metioned above.The results show that the influence of heat transfer on flow structure and loss in cylinder wake region still exist even when Ri<0.1. When Re=5000, becasuse of heat transfer the distance between cylinder and minimum dimensionless velocity position in time-averaged flow field reduces approximately 2.5%, as well as the percentage of the 1^st POD mode energy decreased by about 1%. When Re=8800, heat transfer makes the 2^nd POD mode energy percentage increase about 0.7% as well. Further analysis indicates that viscous dissipation is a significant factor for the effect of heat transfer on each POD mode energy, as well as corresponding mode energy decreases with the increasing of viscous dissiapation.