Aerothermal Investigations on Mixing Flow Field of Film Cooling With Swirling Coolant Flow

Abstract

This paper describes the experimental results of a new film cooling method that utilizes swirling coolant flow through circular and shaped film cooling holes. The experiments were conducted by using a scaleup model of a filmcooling hole installed on the bottom surface of a lowspeed wind tunnel. Swirling motion of the film coolant was induced inside a hexagonal plenum using two diagonal impingement jets, which were inclined at an angle of خ± toward the vertical direction and installed in staggered positions. These two impingement jets generated a swirling flow inside the plenum, which entered the filmcooling hole and maintained its angular momentum until exiting the filmcooling hole. The slant angle of the impingement jets was changed to خ±â€‰= 0 deg, 10 deg, 20 deg, and 30 deg in the wind tunnel tests. The film cooling effectiveness on a flat wall was measured by a pressure sensitive paint (PSP) technique. In addition, the spatial distributions of the nondimensional concentration (or temperature) and flow field were measured by laserinduced fluorescence (LIF) and particle image velocimetry (PIV), respectively. In the case of a circular filmcooling hole, the penetration of the coolant jet into the mainstream was suppressed by the swirling motion of the coolant. As a result, although the coolant jet was deflected in the pitch direction, the film cooling effectiveness on the wall maintained a higher value behind the cooling hole over a long range. Additionally, the kidney vortex structure disappeared. For the shaped cooling hole, the coolant jet spread wider in the spanwise direction downstream. Thus, the pitchaveraged film cooling effectiveness downstream was 50% higher than that in the nonswirling case.