Experimental and numerical investigations of vane endwall film cooling with different density ratios

In the current paper, endwall film cooling and its secondary effect on vane surfaces in a linear cascade are measured using pressure sensitive paint (PSP) at different density ratios. Flow fields are obtained by a validated numerical method. Upstream double-row film cooling holes with an inclination angle (alpha) of 30 deg. are studied, including streamwise cylindrical holes, compound-angled cylindrical holes and double-jet film-cooling (DJFC) holes. The density ratio (DR) varies as 1.0, 1.5 and 2.5. Low- and high-blowing ratio conditions (M = 0.5 and 2.0) are also considered. Results reveal that, at a low blowing ratio, higher endwall cooling effectiveness is obtained as the DR increases, while the variation of density ratio shows a limited impact on the secondary cooling effectiveness of vane surfaces. At a high blowing ratio, with the increase of DR, the coolant coverage gradually shrinks, especially on the endwall and the vane pressure surface. Moreover, obvious differences in coolant coverage are observed among the investigated cooling configurations.