EXPERIMENTAL AND NUMERICAL INVESTIGATION ON HEAT TRANSFER AND FLOW CHARACTERISTICS OF ARRAY JET IMPINGEMENT COOLING WITH FILM EXTRACTION AT THE TURBINE SHROUD

Jet impingement cooling is applied as an effective forced convection cooling method in regions with high thermal loads. This paper investigates the application of an array jet impingement with film holes extraction system on the turbine shroud. The cooling air is first accelerated through jet holes and impinging on the internal wall. Subsequently, the spent air is discharged in perpendicular directions through film holes. The distribution of wall Nusselt number is spatially resolved through liquid crystal thermography (LCT), and the flow structure of the impinging jets is obtained by 3D steady-state numerical simulation to further analyze the mechanism of jet-enhanced heat transfer. The effect of jet Reynolds number based on the jet hole diameter, jet-to-target spacing, and jet-to-jet spacing in the X and Y direction are investigated with a parameter range of 9100 ≤ Re ≤ 19800, 6.0 ≤ H/D ≤ 12.5, 4.0 ≤ A/D ≤ 7.5, 9.0 ≤ C/D ≤ 17.0. The results show that the wall heat transfer is mainly affected by the impinging jets, wall jets, the interaction between adjacent wall jets, and film hole extraction. The jet Reynolds number does not affect the flow structure and wall heat transfer distribution. The increased momentum decay of the jet flow due to the increase in jet-to-target spacing causes the wall heat transfer to decrease monotonically. The variation of jet-to-jet spacing in the Y direction has little effect on the area-averaged Nusselt number of the target wall, but it will shift the stagnation region. While the heat transfer at the sidewall is more sensitive to the jet-to-jet spacing in the Y direction. With the decreasing of the jet-to-jet spacing in the X direction, the area occupied by the stagnation gradually increases, thus, the area-averaged Nusselt number is significantly enhanced. In addition, other heat transfer regions are also significantly enhanced due to the increased amount of cooling air.