Experimental Investigation on Flow Field Characteristics of Impinging-Film Cooling

This paper describes an experimental investigation on flow field characteristics of impinging-film cooling. Particle Image Velocimetry (PIV) technology has been applied to observe the effect of blowing ratio (0.04 <= M <= 0.3), temperature ratio (0.73 <= T-u <= 0.91), jet-to-plate pitch (1.6 <= Z(n)<= 3.2), and spacing of impinging holes (1.94 <= Y-n <= 3.5) on the flow field patterns in an impinging-film cooling test rig under atmospheric pressure. Experiment results show that the near-wall entrained vortex at the downstream of the slit moves downstream of the test rig as the blowing ratio increases, which increases the effective protection length of the film. While the vortex at the end of the inducting slab is stronger, this will increase the mixing in the shear layer. The radial size of the near-wall entrained vortex tends to decrease as the temperature ratio increases at the low blow ratio, and the entrainment effect on the downstream of the slit becomes smaller, causing the separation zone to decrease. Increasing the jet-to-plate pitch, the size of the near-wall entrained vortex increases, and the thickness of the film layer increases, this strengthens the separation effect of the near-wall airflow from the wall surface. The larger the spacing of the impinging holes, the more uneven the velocity distribution of the film.