出流孔型对平板气膜冷却影响机理的研究

Numerical Simulation on Effects of Different Film Cooling Holes on Plate

关键词:  气膜冷却  数值模拟  水滴形孔  收敛缝形孔  扇形孔 

Key words:  Film cooling  Numerical simulation  Water-drop shape hole  Converging slot hole  Fan hole

摘要:

为了研究不同孔型对平板气膜冷却的影响,针对圆形,扇形,水滴形,收敛缝形四种气膜出流孔型的流动和传热特性进行了数值模拟。研究结果表明,圆形孔、扇形孔和水滴形孔气膜出口下游出现从中心向上抬升的反向旋转涡对,将主流燃气卷吸进来；收敛缝形孔在侧向的扩张型面使得气膜出流在展向的覆盖更为均匀,这有效地阻止了高温气体的侵入；在相同吹风比下,收敛缝形孔在气膜出口附近区域的平均绝热冷却效率则明显要高于其余三种孔,随着吹风比的增大,这种差距越发明显；孔型对对流换热系数增强比的影响区域仅局限在邻近气膜孔出口大约7倍气膜孔径的范围内。 

Abstract:

Numerical simulation was carried out to study the flow and heat transfer characteristics of film cooling on flat plate with different hole shapes including circle, fan, water-drop and converging slot. The results show that the counter-rotating vortex pair lifting up from the center have appeared in the outlet of film with circle-shaped, fan-shaped water-drop shaped hole, which will revolve the mainstream gas flow into the film coolant. Film from converging slot shows different flow characteristics.The slot with a spanwise expansion makes film spreading widely on the wall which effectively prevents the invasion of hot gas. Under the same blowing ratio, the cooling effectiveness of the converging slot hole is significantly better than the other three holes. With increasing blowing ratio, this advantage of the converging slot is more obvious.The impact of hole shape on heat transfer enhancement ratio is limited in the range of 7times of film hole diameter away from the outlet. 