ABSTRACT

Impingement cooling is conducive to enhancing the cooling performance of turbine blade trailing edge channel, and slot ejection can be adopted for additional cooling. This paper explores the influence of the chordwise length ratio of the impingement cavity to the ejection slot on the channel’s heat transfer and friction factor. In the experiment, three models with the chordwise length ratios (CR) of 1.6, 0.68, and 0.36 were tested under the Reynolds number of 22,000–69000. The flow field was numerically simulated when CR = 0.68. The distribution of Nusselt number on the pressure and suction sides of impingement cavity and ejection slot was obtained. Besides, the heat transfer distribution mechanism was explained based on the flow characteristics obtained through numerical study. Through evaluation of the overall heat transfer and pressure loss of each structure, it can be observed that chordwise length ratio constitutes an important factor for heat transfer. It was found that the overall Nusselt number is larger when CR is smaller, but there is a limit to the enhancement of heat transfer performance. Among the three models, the structure with CR = 0.68 suffers the maximum pressure loss. In conclusion, the cooling performance could be improved, with less pressure loss, by optimizing the chordwise length ratio of the impingement cavity to the ejection slot.

摘要

冲击冷却有利于提高涡轮叶片后缘通道的冷却性能，可采用槽喷射进行附加冷却。本文探讨了冲击腔与喷射槽的弦长比对通道传热和摩擦系数的影响。在实验中，三个模型的弦长比（CR）分别为 1.6、0.68 和 0.36，在 22,000-69000 的雷诺数下进行了测试。当 CR = 0.68 时，对流场进行了数值模拟。得到了冲击腔和喷射槽压力侧和吸力侧的努塞尔数分布。此外，还根据数值研究得到的流动特性解释了传热分布机理。通过对每个结构的整体传热和压力损失的评估，可以观察到弦长比是传热的重要因素。发现整体努塞尔数较大时CR较小，但传热性能的提高有一定限度。三种模型中，CR  =0.68的结构压力损失最大。总之，通过优化冲击腔与喷射槽的弦向长度比，可以提高冷却性能，同时减少压力损失。