Abstract

Tip clearance cavitation is one of the most common cavitation phenomena exist on duct propellers, pumps and some hydraulic turbines, which may lead to erosion of the components. Due to the influence of the nearby wall, cavitation inside the tip clearance is more complicated than other cases without interaction. So far, the understanding about the impact mechanism of tip clearance cavitation is still limited. In this paper, to obtain the impact behavior of tip clearance cavitation, a high-speed camera was used to capture the cavitation behavior inside the tip clearance of a hydrofoil, and surface paint coating peeling method was applied to show the impact region. Results indicated that cavitation around the tip of the hydrofoil was composed of a tip separation cavity and a tip leakage vortex cavity, and the one with contribution to impact was the tip separation cavity. Through the comprehensive analysis of the paint peeling region and dynamic behavior of tip separation cavity, the impact was found to be related to the local collapse and rebound of the cloud cavitation shed from the attached part. In addition, the influence of tip clearance size on the behavior of tip clearance cavitation was also investigated. As the tip clearance size increased, the tip separation cavity tended to transfer from sheet cavitation to vortex cavitation. These findings can provide a sound basis for evaluating the erosion risk arising from the tip clearance cavitation.

中文翻译：

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水翼叶尖间隙内空化冲击行为的实验研究

摘要

叶尖间隙空化是导管螺旋桨、泵和一些水轮机上最常见的空化现象之一，可能导致部件腐蚀。由于附近壁面的影响，叶尖间隙内的空化比其他没有相互作用的情况更加复杂。迄今为止，对于叶尖间隙空化的影响机制的认识仍然有限。本文为了获得叶尖间隙空化的冲击行为，采用高速摄像机捕捉水翼叶尖间隙内的空化行为，并采用表面油漆涂层剥离方法显示冲击区域。结果表明，水翼尖端周围的空化由尖端分离腔和尖端泄漏涡腔组成，其中对冲击有贡献的是尖端分离腔。通过对油漆剥落区域和尖端分离空腔动态行为的综合分析，发现该影响与云空化棚从附着部分的局部塌陷和反弹有关。此外，还研究了叶尖间隙尺寸对叶尖间隙空化行为的影响。随着叶尖间隙尺寸的增加，叶尖分离腔倾向于从片状空化转变为涡流空化。这些发现可以为评估叶尖间隙空化引起的侵蚀风险提供良好的基础。