叶尖间隙控制系统悬浮管换热单元数值研究

Numerical Study of Suspending Tube Heat TransferUnit for a Blade Tip Clearance Control System

关键词:  间隙控制  冲击换热  出流方式  横流  肋化表面

Key words:  Clearance control  Impinging jet heat transfer  Outflow type  Cross-flow  Ribbed surface

摘要:

为了改善机匣内横流影响，提高冷气的热沉利用效果，设计了一种叶尖间隙控制系统新型悬浮管式冷却结构，并抽象出典型换热单元开展数值模拟研究。重点关注了悬浮管上冷却孔冲击雷诺数、冲击孔间距、冷却空气出流方式等对该冷却结构流动换热特性的影响。研究中发现:悬浮管相邻冲击射流之间会相互影响并形成“喷泉流”现象；随着悬浮管冷却孔冲击雷诺数减小、冲击孔间距增大，冲击靶面换热效果降低，“喷泉流”现象不再明显。同时由于悬浮管本体及盖板的空间限制作用，冲击腔中会形成沿周向、轴向的横流。研究结果表明，当机匣侧方位冷气出流时，机匣表面沿轴向的横流最为明显。相较于机匣侧面出流，盖板垂直出流以及盖板垂直/机匣侧面同时出流时，两高肋之间区域的换热得到明显加强。其中垂直出流时增幅最大，可达20%。

Abstract:

To improve the effects of cross-flow and the usage of coolant heat sinks， the numerical simulation is carried out in the present study for a typical heat transfer unit in a new type of suspending tube cooling structure of a blade tip clearance control system. The effects of some key parameters are studied on the heat transfer characteristics of the cooling structure， such as the impinging Reynolds number， distance of jet to jet and outflow type. It is found that a phenomenon of ‘fountain flow’ appears formed by the interaction of adjacent impinging jets of suspending tubes. With decreasing the impinging Reynolds number and increasing the distance of jet to jet， the heat transfer on the target is weakened and the phenomenon of ‘fountain flow’ is no more significant. Due to the space limitation caused by the suspending tubes and the cover plate， the circumferential and axial cross-flows are formed in impinging chamber. When the coolant flow exits from the side of the case， the axial cross-flow is most significant on the casing surface. Compared to the outflow from the side of the case， the heat transfer between the two high ribs is enhanced considerably when the outflow is from the top of the case， or from both the top and the side of the case. A maximum increase is up to around 20% when the outflow is from the top.