Heat transfer in two-pass smooth square channel under large rotation numbers
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摘要: 通过提高回转通道内气体压力到500 kPa以上，显著扩展了实验参数范围.实验雷诺数Re和旋转数Ro范围分别为10 000~70 000和0~2.08，完全匹配了真实发动机的Re和Ro.在此基础上实验研究了高旋转数下方截面光滑U型通道的换热特性.结果表明，在高旋转数下，旋转效应对通道进口和转弯段局部换热的影响比进口效应和弯道效应显著；第1通道后缘面换热随旋转数的增大而增强，而中下游前缘面在超过临界旋转数后换热增强；高旋转数下第2通道下游后缘面的换热强于前缘面.Abstract: The rotation number range was expanded significantly through increasing the absolute pressure of the channel to about 5 atm. Experiments were carried out to investigate heat transfers in a smooth square two-pass channel under large rotation numbers. In current study, Reynolds and rotation number range from 10 000 to 70 000 and zero to 2.08 respectively, which covered the real engine parameters. It is found that when the rotation number is large enough, the effect of rotation dominates the heat transfer at the inlet and the turn portion, instead of the entrance effect and the turn effect. As the channel rotated, the Nusselt number of the first pass was found to increase monotonically on the trailing wall, however to increase on the middle and downstream of leading wall exceeding certain critical rotation numbers. And a new phenomena is found in the downstream of the second pass, which is that the heat transfer on trailing surface exceeds the leading surface at high rotation numbers.
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Key words:
- gas turbines /
- blade cooling /
- two-pass channel /
- convective heat transfer /
- high rotation number
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