Film Cooling Effectiveness of Forward and Backward Compound-Angled Trench-Holes Under Coolant Cross-Flow Effects

Film coverage characteristics of backward and forward compound-angled film-holes embedded in the transverse trench were measured under two cross-flow ratios (Cr=0.08 and 0.16) and three blowing ratios (BR=0.5, 1.0 and 2.0) by means of infrared thermal imaging technology. Comparisons indicated that trench, compound-angle, and backward injection have a significant inhibitory-effect on the jet separation phenomenon occurring in the simple-angled forward injection case, and hence the closely corresponding cooling air coverage is improved obviously. Cross-flow could effectively suppress the deflection of film cooling effectiveness caused by compound-angled ejection in the case of large-cavity intake, making the more even distribution of cooling air. At the same Cr, small BRs caused the better overall coverage of cooling air from the backward ejections than that of the forward ejections, while large BRs induced the reverse conclusion. At the small Cr=0.08, the 120° trenched-holes presented the best film coverage at each BR, and the effectiveness was increased about 42% relative to the common simple-hole, while under the large Cr=0.16, the 60° trenched-holes showed the best film coverage, and the increment of effectiveness was about 26%. © 2021, Science Press. All right reserved.