发散孔结构参数对横向波纹表面气膜绝热冷却效率的影响

针对加力燃烧室特定横向波纹结构的隔热屏发散冷却进行数值模拟,主要研究发散孔孔节距、孔径以及开孔率等3个结构参数对发散冷却效率的影响。结果表明:由于处于波纹波谷的相邻气膜射流更易于形成相干,从而在波谷形成更强的集聚效应,造成波谷附近的绝热壁面温度低于波峰区域；在相同的壁面单位面积冷气用量下,减小孔径、增大开孔率均显著改善气膜冷却效率,尤其是在发散气膜的前排起始段；发散孔流向节距大于展向节距的长菱形排布相对较优,但在小吹风比下发散孔排布节距比对展向平均绝热冷却效率的影响非常微弱。 

Effects of structural parameters of effusion holes on adiabatic film cooling effectiveness over transverse corrugated surface

Numerical simulation was carried out to study the effusion cooling on a specific transverse corrugated heat-shield used in aero-engine afterburner. Three main geometric parameters, including spanwise-to-streamwise pitch ratio, hole diameter and perforated percentage, were taken into consideration. Result showed that, in the wavy valley of transverse corrugated surface, the coolant jets ejected from adjacent holes were prone to interact each other, thus forming more coolant accumulation. Due to this feature, the adiabatic wall temperature on the wavy valley of transverse corrugated surface was relatively lower than that on the wavy peak. In general, reducing the hole diameter and enlarging the perforated percentage were illustrated to be significantly helpful to enhance the film cooling effectiveness under the same coolant usage for a given protected area, especially in the front developing zone of an effusion cooling scheme. Besides, the effusion holes arranged in a super-long-diamond mode where the streamwise hole-to-hole pitch was bigger than spanwise hole-to-hole pitch showed more favorable. However, the effect of spanwise-to-streamwise pitch ratio on the laterally-averaged adiabatic film cooling effectiveness was very weak at low blowing ratio.