周向角和直径比对切向双旋流冷却流动与传热特性的作用机理

Effects of Circumferential Angle and Diameter Ratio on the Flow and Heat Transfer Characteristics of Double Swirl Cooling

考虑到当前对透平叶片前缘双旋流冷却结构的流动与传热机理认识不足,建立了合理的切向双旋流冷却结构模型,采用雷诺时均Navier-Stokes方程求解SSTk-ω湍流模型,数值分析了周向角为60°~120°、直径比为0.435~1.2时双旋流腔内的流动和传热特性。计算结果表明:与单旋流冷却相比,冷气在双旋流腔内形成相反涡对,在融合区出现冲击和再附现象,使综合换热性能更好。随着周向角增大,旋流腔壁面的努塞尔数先增大后减小,而摩擦系数呈现相反的变化趋势,评估得到周向角为90°时的综合换热因子最高,可以达到1.49;当直径比为0.6时,综合换热因子可达到1.52,当直径比小于0.6时,综合换热性能几乎不受直径比影响,而直径比大于0.6时,综合换热性能随直径比增大而减小,尤其在直径比大于1时急剧下降。

Considering the lack of understanding of the flow and heat transfer mechanism of the double swirl cooling structure at the leading edge of turbine blades,a reasonable tangential double swirl cooling structure model was established.The SST k-ωturbulence model was solved by using the Reynolds averaged Navier-Stokes(RANS)equation.The flow and heat transfer characteristics of the double swirl chamber were analyzed when the circumferential angle is 60°-120°and the diameter ratio is 0.435-1.2.The results show that,compared with the single swirl cooling,the opposite vortex pair is formed in the double swirl chamber,and the phenomenon of impingement and reattachment appears in the fusion zone,which makes the comprehensive heat transfer performance better.With the increase of the circumferential angle,the Nusselt number of the swirl chamber wall increases first and then decreases,while the friction coefficient shows an opposite trend.It is estimated that the comprehensive heat transfer factor reaches its highest value 1.94 when the circumferential angle is 90°.When the diameter ratio is 0.6,the comprehensive heat transfer factor can reach 1.52;when the diameter ratio is less than 0.6,the comprehensive heat transfer performance is almost unaffected;and when is greater than 0.6,the comprehensive heat transfer performance decreases with the diameter ratio,especially when the diameter ratio is greater than 1,the performance drops dramatically.