Abstract: To match the real engine operating condition，Reynolds and Rotation number range of current experiment are expanded from 10000 to 70000 and 0 to 2.0 through increasing the absolute pressure of the air in the U-duct to 500kPa. Experiments have been conducted to investigate the heat transfer characteristics in a square U-duct with 90° ribs. The results indicate that Nusselt number ratio of leading wall in the first passage firstly decreases and then increases as the rotation number increasing，and the critical rotation number is constant，Roc=0.26. In the second passage，Nusselt number ratio of leading wall behaves constantly better than trailing wall with the increasing of the rotation number，which is totally different from that of the smooth channel. And contrary to the difference of Nusselt number ratio between inner and outer wall in the second passage of the smooth channel，it becomes smaller along the second passage of U-duct with 90° ribs.

Key words: Reynolds number；High rotation number；90° Rib；U-duct；Heat transfer characteristics

摘要： 通过提高U型通道气体压力到500kPa以上，将实验雷诺数Re和旋转数Ro范围分别扩展到10000～70000和0～2.0，从而匹配真实发动机转子叶片的工作条件。在此基础上实验研究了高旋转数下带直肋的、方形截面的U型通道的换热特性。研究结果表明:第一通道前缘面的努塞尔数比随旋转数的增大先下降后增强，该临界旋转数为定值Roc=0.26；随着旋转数的增大，第二通道前缘面的努塞尔数比一直高于后缘面，与光滑通道中的换热规律不同；随着旋转数的增大，第二通道内外侧面努塞尔数比的差异逐渐减小，在临近出口处几乎没有差异，与光滑通道相比正好相反。

关键词: 雷诺数；高旋转数；直肋；U型通道；换热特性