Effects of the purge coolant jet on the turbine endwall film cooling performance considering the geometric features of the upstream slot

This study investigated several crucial parameters of the end-wall slot, namely the inclination angle, width, outlet position, and outlet fillet. Slot cooling effectively reduced the end-wall thermal load. To experimentally assess the end-wall film cooling effectiveness, the pressure−sensitive paint (PSP) measurement method was employed. Both experimental findings and numerical simulations were used to analyze the aerodynamic cooling characteristics in the end-wall region for various slot configurations. The results revealed that the area with high cooling effectiveness significantly expanded as the slot inclination angle (α) and the distance (D) between the slot outlet and the vane decreased, and as the fillet radius (R) increased. For example, at a mass flow ratio (MFR) of 2.0 %, reducing α from 50° to 30° led to a 22.9 % decrease in the average cooling effectiveness. In contrast, at an MFR of 1.5 %, increasing R from 5 mm to 10 mm resulted in an 11.5 % improvement in the average cooling effectiveness. Moreover, reducing the slot width (d) enlarged the coolant coverage area, thereby significantly enhancing the average cooling effectiveness on the end-wall surface. Specifically, at an MFR of 2.0 %, increasing d from 1.8 mm to 5.4 mm led to a 22.4 % decrease in the average cooling effectiveness. It is worth noting that when d = 1.8 mm, the area with high cooling effectiveness was slightly smaller than that of the baseline width of 3.6 mm.