Numerical simulation on heat transfer and entropy generation of impingement cooling on boss shaped surface

凸台形表面冲击冷却换热及熵增的数值模拟研究

School of Power and Energy, Northwestern Polytechnical University, Xi’an 710072, China

Received: 6 July 2021

Abstract

Using impingement jet to cool the external cavity of the end wall of the gas turbine guide blade is very effective for prolonging the service life of the gas turbine and ensuring its safety operation. In this paper, the numerical simulation method is used to study the impingement cooling heat transfer performance of the boss shaped surface in the external cavity of the end wall of the gas turbine guide blade, and the entropy generation of the impingement heat transfer process is analyzed. The results show that the average Nusselt number on the impingement target surface and the impingement hole surface increase with the increase of the Reynolds number of the impingement jet. When the Reynolds number is constant, the average Nusselt number of impingement target surface and impingement hole surface decrease with the increase of impingement target distance, but the cooling range on the impingement target surface increases and the heat transfer is more uniform. With the increase of the width of the boss shaped upper surface, the cooling range on the impingement target surface relatively decreases, and the average Nusselt numbers of the impingement target surface decreases and that of the impingement hole surface increases respectively. The heat transfer of the upper surface of the boss is better than that of the lower surface on both sides. The entropy generation in the process of impingement cooling mainly comes from the entropy production caused by viscous dissipation and the entropy flow caused by heat transfer. The entropy production in the flow vortex region is the main reason for the entropy generation. The research conclusions can provide basis and reference for optimizing the structural and operating parameters of boss shaped impingement cavity and improving its impingement heat transfer effect.

摘要

采用冲击换热方式对燃气涡轮导向叶片端壁外侧腔体进行冷却，对于延长燃气涡轮的使用寿命和保障其安全运行十分有效。采用数值模拟方法，对燃气涡轮导向叶片端壁外侧腔体内凸台形表面的冲击冷却换热性能进行研究，并对冲击换热过程的熵增进行分析。研究表明: 随着冲击气流雷诺数的增大，冲击靶面与冲击孔面上的平均努塞尔数增大; 雷诺数一定时，增大冲击靶距，冲击靶面和冲击孔面平均努塞尔数减小，但冲击靶面上的被冷却范围增大，换热更加均匀; 增大凸台上表面的宽度，冲击靶面上的被冷却范围相对减小，冲击靶面和冲击孔面的平均努塞尔数分别减小与增大; 凸台上表面比其两侧的下表面换热更好; 冲击冷却过程的熵增主要来源于因黏性耗散产生的熵产及换热产生的熵流，流动涡旋区的熵产是熵增的主要原因。研究结论可为优化凸台形冲击腔的结构参数及操作参数，提高其冲击换热效果提供依据和参考。