Experimental investigation of the influence of density ratio and vane exit Mach number on platform cooling

The present paper reports the results of an experimental investigation of the influence of coolant to mainstream density ratio (DR) on the thermal and aerodynamic behavior of a nozzle vane cascade with platform cooling through slot or discrete holes. Measurements were carried out on a 6 vane cascade at low (1.6%) and high (9%) inlet turbulence intensity level, with blowing ratios (BR) varied in the range of 1-2. Tests were performed injecting carbon dioxide (DR = 1.5) as coolant flow. Aerodynamic investigations were performed by means of a miniaturized 5-hole pressure probe traversed in a downstream plane to assess the impact of the aforementioned parameters on secondary flows structure and related losses. Concerning thermal measurements, the binary PSP technique was employed to measure the adiabatic film cooling effectiveness. Three platform cooling schemes have been investigated: the first one features a slot located upstream of the leading edge, the second one makes use of cylindrical holes distributed both upstream and inside of the passage and the last one is based on standard 10-10-10 shaped holes. These results will be compared with previous data [1] obtained testing the same cooling schemes with a high inlet turbulence intensity level and injecting air as coolant (DR = 1). These cooling schemes are representative of real engine platform film cooling configurations and will allow to critically assess the impact of density ratio and mainstream turbulence intensity level on cascade aerodynamic and thermal performance for variable injection conditions.[1] G. Barigozzi, A. Perdichizzi, L. Abba, L. Pestelli, 2020, “Platform Film Cooling Investigation on an Hp Nozzle Vane Cascade with Discrete Shaped Holes and Slot Film Cooling” ASME Paper GT2020-2849.