Numerical Investigation of Tip Leakage Vortex Cavitation in Axial Waterjet Pump With Different Tip Gap Sizes

Shun Xu, B. Ji, X. Long, Z. Qian, Gui-bin Li, Jia-jian Zhou
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Abstract

The flow field in the tip region of the axial-flow waterjet pump is very complex. Although it has been studied for many years, many relevant phenomena have still been a puzzle. In present paper, many detailed data on instantaneous inner structures of the tip leakage flow and evolution of the tip leakage vortex cavitation with different tip gap sizes are offered. The numerical simulation has been conducted by using SAS turbulence model and ZGB cavitation model to understand the cavitation-vortex interaction mechanism. The predicted cavitation performance exhibits a reasonable agreement with the experimental results. Based on the illustration, with the impeller tip gap size decreasing, the cavitation area in rotating region gradually decreases. The cavitation development enhances vorticity production in an axial-flow waterjet pump. Vortices are mainly located at the impeller tip leakage region. The analysis of the relative vorticity transport equation indicates that the baroclinic torque term and the vortex dilation term have significant effects on cavitation, the main contributor to vortex generation is the vortex dilation term. In addition, in the impeller tip region, the effect of viscous diffusion term cannot be ignored, and the cavitation area has a larger amplitude of pressure pulsation.
不同叶尖间隙尺寸轴向喷水泵叶尖泄漏涡空化的数值研究
轴流式水射流泵叶顶区域的流场非常复杂。尽管人们对它进行了多年的研究,但许多相关现象仍然是一个谜。本文提供了叶尖泄漏流动的瞬时内部结构和不同叶尖间隙大小下叶尖泄漏涡空化的详细数据。采用SAS湍流模型和ZGB空化模型进行数值模拟,了解空化-涡相互作用机理。预测的空化性能与实验结果吻合较好。由图可知,随着叶轮叶顶间隙的减小,旋转区空化面积逐渐减小。空化的发展提高了轴流泵涡量的产生。旋涡主要分布在叶顶泄漏区。对相对涡量输运方程的分析表明,斜压转矩项和涡膨胀项对空化有显著影响,涡膨胀项是涡产生的主要因素。此外,在叶轮尖端区域,粘性扩散项的影响不容忽视,空化区域的压力脉动幅值较大。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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