小流量工况下混流泵涡识别及其演变规律

Vortex identification and its evolution law of mixed-flow pump under low-flow condition

为了研究小流量工况下混流泵内部流动状态及涡结构的演化规律,采用大涡模拟的计算方法并结合先进的Omega涡识别方法,对某混流泵小流量工况下的涡结构进行识别,获得了叶轮内部典型涡结构的特征和演化规律,并与叶片表面的涡量生成和流动分离情况进行对比分析.研究结果表明:Omega方法克服了第二代涡识别方法需要人为调节阈值的缺陷,可以较好地识别小流量工况下混流泵内部的精细涡结构;在小流量工况下,混流泵内的叶片斜向涡带、叶尖涡和叶尖分离涡、通道涡以及尾缘脱离涡是叶轮流道内生成的典型涡结构,它们有各自独立的生成和发展过程,又相互作用,使叶轮内流场更加紊乱.本研究揭示了小流量工况下混流泵内部特有的涡结构特征与演变规律,可为包括混流泵在内的叶轮机械流场分析和性能优化提供一定的理论指导和技术支撑.

In order to study evolution law of the flow state and vortex structure of a mixed-flow pump under low-flow conditions,the large eddy simulation and the advanced Omega vortex identification method were used to identify the vortex structure in a mixed-flow pump under low-flow conditions.The characteristics and evolution law of the typical vortex structures in the impeller were obtained,and the results were compared with vorticity generation and flow separation on blade surface.The results show that the Omega method overcomes the problem that the second generation vortex identification method needs to manually adjust the threshold value,and can identify the fine vortex structure in the mixed-flow pump under the condition of low-flow.Under low-flow conditions,the vane oblique vortex belt,tip vortex,tip separation vortex,passage vortex and trailing edge separation vortex in the mixed-flow pump are typical vortex structures generated in the impeller passage.They have their own independent gene-ration and development process,and interact with each other,making the flow field in the impeller more chaotic.This study reveals the unique vortex structure characteristics and evolution laws in the mixed-flow pump under low-flow conditions,which can provide a theoretical guidance and technical support for the flow field analysis and performance optimization of turbomachinery including mixed-flow pump.