超紧凑涡轮过渡段流动特征与优化设计研究

Flow Mechanisms and Optimization Design Within a Super-Aggressive Intermediate Turbine Diffuser

对某型带支板超紧凑涡轮级间过渡段进行了数值模拟,讨论了综合评价过渡段气动性能的方法,分析了超紧凑过渡段内典型流动特征,并针对该超紧凑过渡段进行了改型设计。结果表明,考虑压缩性、面积比、出口面选取等影响因素的扩压效率计算能更加合理的描述过渡段扩压性能;超紧凑过渡段中机匣流动分离以及支板表面径向流动较强,从而形成复杂的二次流动结构,导致超紧凑过渡段内流动损失增加,是超紧凑过渡段内典型的流动特征;通过优化机匣和轮毂局部曲率,同时合理调整支板厚度分布和流向面积分布,优化设计后的超紧凑过渡段叶栅效率提高了4%,扩压效率提高了10.8%,出口面二次流动能减小了38%。

Fully understanding of the flow mechanism of a super-aggressive intermediate turbine diffusers(AITDs)is the key to developing novel design techniques.Firstly,the flow analysis method of the AITDs was investigated in this study,and a new method for comprehensively evaluating the aerodynamic performance of the AITDs was proposed.Then,the typical flow characteristics in the AITDs were analyzed.Finally,it was further discussed that the integrated design method of the AITDs taking the combined impact of upstream and downstream into consideration.Results show that the calculation of diffusional efficiency considering the influence factors such as compressibility,area ratio and outlet face selection can more reasonably describe the diffusivity of the transition section.In the AITDs,the casing flow separation and the radial flow around the struts are stronger,resulting in the formation of a complex secondary flow structure,and flow loss in the AITDs is increased,which is a typical flow characteristic in the AITDs.By optimizing the local curvature of the casing and the hub,the thickness distribution and flow area,the efficiency of cascades increased by 4%,diffuser efficiency increased by 10.8% and second kinetic energy(SKE)decreased by 38%.