Film cooling performance in a low speed 1.5-stage turbine: effects of mainstream Reynolds number and turbulence

Abstract

The effects of mainstream Reynolds number and turbulence to film cooling performance were investigated experimentally and computationally under rotating conditions in a 1.5-stage turbine. The rotor of the turbine included 18 blades with chord of 124.3 mm and height of 99 mm. A film hole was set in the middle span of the rotor blade surface with injection angles of 28° on the pressure side and 36° on the suction side respectively. The Reynolds number based on the mainstream velocity of the turbine outlet and the chord length of the rotor blade varied from 1.9 × 105 to 2.1 × 105. Measurements were made at three different rotation speeds of 702, 737 and 800 rpm to keep the rotating number consistent at 0.0280 while the blowing ratio varied from 0.5 to 2.0. Air and CO2 worked as coolant to achieve the density ratio of 1.03 and 1.57, respectively. Computational investigation was performed using the hexahedral structured grids and k-e turbulence model. Results showed that the film coverage and cooling effectiveness are enlarged while the film deflection is weakened as the mainstream Reynolds number increases. Furthermore, the mainstream turbulence plays a negative role in the film coverage and cooling effectiveness at lower blowing ratio on both the pressure side and suction side while it promotes the film reattachment at higher blowing ratio on the suction side.