喷嘴周向位置和旋流腔拔模斜度对旋流冷却的影响

Effects of Jet Nozzle Circumferential Position and Vortex Chamber Draft Angle on the Flow and Heat Transfer Characteristics of Vortex Cooling

为了研究喷嘴周向位置及旋流腔拔模斜度对旋流冷却流动和传热特性的影响,探究综合性能更为优良的冷却结构,建立了适用于叶片前缘的旋流冷却模型。在验证了湍流模型的前提下,采用CFD方法对不同模型的流动换热特性进行了对比分析。结果表明:冷气从进口射入旋流腔,形成高速旋转运动;冷气的三维流线沿轴向先径向收缩后径向扩张。喷嘴周向位置改变时,高速旋流区和低速旋流区的相对位置改变,并且高Nu区域的周向位置改变。对于叶根进气的情况,拔模斜度增大时,高速旋流区面积增加,低速旋流区面积减小,并且压力系数减小;当拔模斜度为正值时,压力系数沿轴向降低;拔模斜度为负值时,压力系数沿轴向升高,高Nu区域面积随着拔模斜度的增加而增加。叶根进气时,以拔模斜度为-1°时为参考值,拔模斜度增大至1°时,换热强度提高了9.1%,靶面传热量增加了8.4%,摩擦因数减小了4.1%,综合换热因数提升了8.8%。本文研究分析了不同几何参数下的旋流冷却流动和换热特性,以期为实际叶片前缘冷却结构的设计提供一定的理论参考。

The effects of jet nozzle circumferential position and vortex chamber draft angle were numerically investigated based on the vortex cooling model suitable for blade leading edge. With the verified turbulence model, the CFD method was carried out to analyze and compare the flow and heat transfer behaviors of different cooling models. Results showed that high speed rotational flow is formed by the cooling air injected from the nozzles. The cooling aires three dimensional streamlines first shrink and then expand radially along the axial direction. When the jet nozzle circumferential position changes, the relative position of high speed vortex region and low speed vortex region may also change, and the position of high Nusselt number region alters circumferentially. When inlet is on the shroud side, the area of high speed vortex region is enlarged and the area of low speed vortex region is contracted with the vortex chamber draft angle. Moreover, the pressure coefficient decreases as the vortex chamber draft angle increases. When the vortex chamber draft angle is positive, the pressure coefficient increases along the axial direction; when the vortex chamber draft angle is negative, the pressure coefficient decreases along the axial direction. If the vortex chamber draft angle is set 1° as the reference, when the vortex chamber draft angle is increased to 1°, the heat transfer intensity is increased by 9.1%, the wall heat flux is increased by 8.4%, the friction factor is decreased by 4. 1% and the comprehensive thermal performance coefficient is increased by 8.8% compared with their corresponding reference values. The flow and heat transfer characteristics of the vortex cooling under different geometrical parameters investigated in this paper, and aims to provide references for designing practical blade tip cooling structures.