Aerodynamic and Endwall Film-Cooling Investigations of a Gas Turbine Nozzle Guide Vane Applying Temperature-Sensitive Paint

Endwall film-cooling investigations are conducted with a single row of fan-shaped holes in a low-speed, six-bladed linear cascade. The incidence of the inlet flow was changed between −5 deg and 40 deg to achieve higher loading conditions, which results in an intensification of the secondary flow and enhanced interaction with the injected coolant. The investigated profile is based on a near-hub section of the nozzle guide vane of a highly loaded gas turbine. The aerodynamic performance was investigated using pneumatic probes. The film-cooling effectiveness distribution is determined using the temperature-sensitive paint technique. Carbon dioxide was used as coolant to provide elevated density ratios of about 1.4. Although low thermal conductivity material is used for the endwall test plate, the measured temperature fields show influences of 3D-heat conduction inside the test plate. To measure film effectiveness and the heat transfer separately, an adiabatic test surface is needed. Therefore, the effects of heat conduction are modeled using the finite-element-method. With the resulting convective heat flux pattern derived from the computations, the endwall film-cooling measurements are corrected. Furthermore, this approach is applied to evaluate the heat loss inside the holes and the film discharge temperature at the hole exit.