横流下前向与反向复合角沟槽孔气膜冷却效率

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

利用红外热像技术实验分析了横流比(Cr=0.08,0.16)和吹风比(BR=0.5,1.0,2.0)对横向沟槽内反向和前向复合角气膜孔的气膜覆盖特性的影响。数据对比指出:沟槽、复合角度和反向冷气出流对于前向简单孔所发生的射流分离现象存在明显的抑制作用,有利于提高气膜覆盖。复合角度在大腔进气(Cr=0)时会引起冷却效率偏转,而横流进气可以有效抑制冷却效率的偏转,使得气膜在横流方向分布更加均匀。在相同横流比时,小吹风比导致反向孔的整体气膜覆盖优于前向孔,大吹风比下情况相反。小横流比时,120°沟槽孔在各吹风比呈现出最好的气膜覆盖,较简单角孔而言,效率提高约42%;大横流比时,60°沟槽孔在各吹风比呈现出最好的气膜覆盖,效率提高约26%。

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%.