FILM COOLING PERFORMANCE IN A LOW-SPEED 1.5-STAGE TURBINE: EFFECTS OF BLOWING RATIO AND ROTATION

Abstract

This paper presents experimental investigations on film cooling performance under rotation in a low-speed 1.5-stage turbine using the thermochromic liquid crystal (TLC) technique. The experiment was accomplished in a test facility which was recently established to study rotating film cooling performance in realistic turbine stages. Eighteen blades of chord length of 0.1243 m and height of 0.099 m were installed in the rotor. A film hole with diameter of 0.004 m, angled 28 degrees and 36 degrees tangentially to the pressure surface and suction surface in streamwise, respectively, was set in the middle span of the rotor blade. All measurements were made at three different rotating speeds of 600, 667 and 702 rpm with the blowing ratios varying from 0.3 to 3.0. The Reynolds number based on the mainstream velocity of the turbine outlet and the chord length of the rotor blade was fixed at 1.89 x 10(5). Results show that on the pressure side, the film coverage and cooling effectiveness scaled up with the blowing ratio and the film deflected centrifugally; on the suction side, the maximum film coverage and cooling effectiveness were obtained at moderate blowing ratio and a centripetal deflection of the film was observed. The film deflection could be amplified by either decreasing the blowing ratio or increasing the rotation number on both sides. Overall, blowing ratio and rotation play significant roles in the film cooling performance.