某型燃气轮机排气段支撑型线优化设计研究

Optimization of Struts Molded Line in a Gas Turbine Exhaust Diffuser

燃气轮机排气段气动性能的优劣对机组整机效率有显著影响。支撑部件附近流动状况复杂,会对排气段性能产生极大影响。基于某型燃气轮机排气段初始流场特征,开展了排气段前、后支撑型线的优化设计。重点考虑对前支撑的优化设计,完成了三种型线优化方案,并应用S1流面计算方法在宽广的来流角度范围下进行损失计算,选择出气动性能最优的结果。后支撑对流动效率影响比前支撑小,因此对后支撑完成了一种适应当地流场的简单优化设计。最后,采用耦合涡轮末级的排气段三维数值模拟方法,对支撑型线优化前后排气段的气动性能变化进行了分析,支撑优化后排气段流动损失比原型明显降低,总压保持因数提高了1.4%。研究成果可为燃气轮机排气段气动设计与优化提供参考。

The aerodynamic performance of exhaust diffuser has significant influence on the efficiency of gas turbine. The flow status near the struts is complex and will significantly affect performance of exhaust diffusers. The front and back molded lines of struts were optimized based on the characteristics of original flow in exhaust diffusor of a gas turbine. With a focus on the front struts,three optimization schemes of molded line were proposed. Under condition of large range of inlet flow angles, loss calculation was carried out applying S1 stream surface method, and the result with the best aerodynamic performance was achieved. Since the back strut had less impact on the flow efficiency than that of front strut, a simplified optimization adapting to the local field flow for the back strut was conducted. Finally, 3D numerical simulation method coupling with the last stage of turbine was applied to analyze the aerodynamics performance of struts in exhaust diffuser before and after optimization. The results showed that the flow loss after optimization was obviously decreased than that of original type, and total pressure maintaining coefficient was raised by 1. 4%. The research results can provide reference for aerodynamic design and optimization of exhaust diffuser in gas turbine.