涡轮端壁内部点阵冷却结构的流热耦合研究

Conjugate Heat Transfer Studies on an Internal Lattice Cooling Structure of Turbine Endwalls

为了进一步提高涡轮端壁的综合冷却性能,以某航空发动机高压涡轮静叶端壁内部冷却结构为研究对象,以点阵结构作为端壁的内部冷却结构,不仅能提高端壁的综合冷却有效度,还能在不影响叶栅气动性能的同时,降低内部冷气的压力损失。对不同吹风比下无内部冷却和内部冲击冷却与点阵冷却端壁的耦合传热特性进行研究,对比分析了各端壁的综合冷却有效度和内部的流动换热特性。结果表明:随着吹风比增大,有内部冷却时端壁中上游的综合冷却有效度大幅提升,而端壁下游的综合冷却有效度由外部气膜冷却主导,其最佳吹风比约为3.0,且几乎不受内部冷却结构的影响;与无内部冷却端壁相比,冲击冷却和点阵冷却端壁的综合冷却有效度得到了大幅提升,且点阵冷却端壁的综合冷却有效度和气动性能均要优于冲击冷却端壁。在吹风比为1.5、3.0和7.0时,点阵冷却端壁的面积平均综合冷却有效度比冲击冷却端壁分别高出1.48%、1.10%和1.33%,在总换热量上则分别高出35.8%、34.0%和7.5%,而其表征流动损失的泵功反而比冲击冷却端壁分别低了36.0%、36.9%和35.1%。

To further improve overall cooling performance of a turbine endwall,internal cooling structures of the vane endwall for the high-pressure turbine of an aeroengine was focused on in this study.Using a lattice structure for internal cooling could not only improve overall cooling effectiveness of the endwall,but also reduce pressure losses of internal cooling structures without affecting aerodynamic performance within the turbine passage.The conjugate heat transfer characteristics of endwalls without internal cooling and with internal impingement cooling and lattice cooling for different blowing ratios were investigated.Overall cooling effectiveness and flow and heat transfer characteristics for different internally-cooled endwalls were analyzed and compared.Results revealed that overall cooling effectiveness in the upstream area of the endwall with internal cooling was greatly improved with the increase of blowing ratios,but that in the downstream area was mainly determined by external film cooling and an optimal blowing ratio was 3.0,which was rarely dependent from the internal cooling.Compared with the endwall without internal cooling,the endwalls with impingement cooling and lattice cooling showed much higher overall cooling effectiveness,and the endwall with lattice cooling was better than that with impingement cooling in terms of overall cooling effectiveness and aerodynamic performance.For the blowing ratios of 1.5,3.0 and 7.0,the endwall with lattice cooling was 1.48%,1.10%,and 1.33%higher respectively in area-average overall cooling effectiveness and 35.8%,34.0%and 7.5%higher respectively in total heat transfer rates,but 36.0%,36.9%,and 35.1%lower respectively in pressure losses compared with that with impingement cooling.