叶尖间隙控制系统中横流效应的试验研究

Experimental Study on Cross Flow Effect in TipClearance Control System

关键词:  叶尖间隙控制  横流  冲击  强化传热

Key words:  Tip clearance control  Cross flow  Impingement  Heat transfer enhancement

摘要:

为了研究带初始横流冷却管式阵列射流冲击换热特性，以基于机匣热变形控制的叶尖间隙控制系统为对象，试验研究了机匣外置多排冷却空气管结构中，初始横流雷诺数（0~8×10⁴）对射流冲击机匣表面换热特性的影响。研究中发现，相比横流雷诺数，冲击雷诺数对靶面平均换热系数的影响更大，平均换热系数随着冲击雷诺数的增加显著提高。初始横流的加入，冲击滞止区发生了沿初始横流流向的偏移，削弱了靶面的冲击换热效果，局部换热数的峰值呈现出先减小后增加的规律。研究结果表明，当横流雷诺数超过4×10⁴后，冲击滞止区下游出现一个“鱼尾形”的换热强化区域，且随着横流雷诺数增加，该鱼尾状区域范围逐步增大，靶面换热效果得到一定程度的提升。冲击孔间距越小，靶面局部和平均换热系数越大，此时横流的影响相对较小，在本文研究参数范围内，冲击孔间距比为4时，会获得更好的换热效果。

Abstract:

To investigate the heat transfer characteristics of the jet impact casing surface in the external multi-row cooling air pipe structure with initial corss flow， for blade tip clearance control systems based on casing thermal deformation control, the experimental study research was conducted to investigates the effects of initial cross flow Reynolds number (0~8×10⁴) on the heat transfer characteristics of the jet impact casing surface in the external multi-row cooling air pipe structure. It is found that compared with the cross flow Reynolds number, the impinging jet Reynolds number has greater influence on the average heat transfer coefficient at the targets, and the average heat transfer coefficient increases significantly with increasing the impinging Reynolds number. With the introduction of initial cross flow, the impingement stagnation zone exhibits an offset along the initial transverse flow, which weaken the targets’ heat transfer effect and the peak of the local heat transfer number decreases firstly and then increases. The study shows that when the cross flow Reynolds number is larger than 4×10⁴, a ‘fish-tailed’ heat transfer enhancement zone can be observed downstream of the stagnation zone. The cover region of the tail area increases gradually with increasing the cross flow Reynolds number, and the target surface heat transfer effect is improved. The smaller the impingement hole spacing, the higher the local and average heat transfer coefficient at the target surface, and the influence of the cross flow is relatively small. In this paper, the heat transfer effect will be better if the ratio of impingement hole spacing is 4.