An experimental investigation of cooling characteristics at a vane end-wall with a locally enhanced hole-layout

Abstract

This paper presents an experimental investigation on the effect of film hole-layout at a turbine vane end-wall on the cooling performances, including the distributions of overall cooling effectiveness, uniformity of temperature field and highest temperature drop, using a hot wind tunnel and an Infrared Thermal Imaging System (ITIS). Two specimens were manufactured and used. One is named as “uniform hole-layout (UHL)”, where ten rows of film holes were uniformly arranged along the axial direction. However, UHL results in a non-uniform temperature distribution over the entire end-wall surface, and the low film coverage and bad reliability in the regions near leading edge (LE) and pressure side (PS) of the vane thereby. To improve the cooling performance in these regions, a new layout named as “locally enhanced hole-layout (LEHL)” was proposed. The difference from the previous experiments conducted under adiabatic assumption is that, the conjugate heat transfer is considered, and the conjugate-temperature distribution is used as the basis of design of LEHL. The comparisons of the cooling performances of two specimens at various mass flow ratios (MFRs) of coolant-to-mainstream revealed that: (1) from MFR = 0.5% to 1.5%, using LEHL, the area-averaged overall cooling effectiveness over the entire end-wall, in LE region and in the corner of PS can be increased by at least 32.3%, 34.2% and 26.2%, respectively; and (2) the temperature differences from PS to suction side (SS) and the temperature at the entire end-wall can be significantly reduced by LEHL. Therefore, the design strategy of new hole-layout using the conjugate-temperature is conducive to obtain the simultaneous improvement of film coverage and working life.