混流泵瞬态加速流空化的数值模拟与实验研究

Numerical and experimental research on cavitation of accelerating flow in mixed flow pump

该文针对名义比转速为800的某一混流泵模型,采用shear stress transport(SST)k-ω湍流模型和Zwart空化模型,通过自编程序控制转速和流量变化,实现了启动过程空化流的精细化数值模拟;研究了加速流过程叶轮内瞬态空化的演变过程,并结合高速摄影实验验证了数值模拟结果的准确性;定量分析了混流泵加速流过程中叶轮内空泡总体积的变化规律。研究结果表明,混流泵加速流空化主要表现为四个阶段:无空泡阶段、空泡增长阶段、空泡减少阶段和空泡稳定阶段。叶顶区的初始空化为刮起涡空化,随后泄漏涡(TLV)空化出现并逐渐发展,到加速完成时刻与刮起涡空化和间隙空化结合形成三角形空化云,并逐渐往叶片尾缘移动;吸力面(SS)上的片状空化演化主要分为增长阶段和消散阶段,其中冲角的变化是造成这一现象的直接原因。当冲角为正值时,在SS面上片状空化发展,冲角为负值时,SS面上低压区逐渐消失,片状空化区域逐渐减小和消散。

In this paper,based on the shear stress transport(SST)k-ωturbulence model and the Zwart cavitation model,for a mixed flow pump model with a specific speed of 800,the fine numerical simulation of the cavitation flow during the startup process is realized through self-programming to control the speed and flow changes.The evolution process of transient cavitation in the impeller of the accelerated flow process is studied,combined with high-speed photography experiment which verified the accuracy of the results.Quantitative analysis of the change of the total volume of cavities in the impeller during the accelerated flow of the model pump is implemented.The results show that cavitation can be divided into four stages,namely:no cavitation stage,cavitation growth stage,cavitation reduction stage,cavitation stabilization stage.The initial cavitation in the tip area is the scraped vortex cavitation,and then the leakage vortex(TLV)cavitation appears and gradually expands toward the chord direction.When the acceleration is completed,it combines with the scraped vortex cavitation and the gap cavitation to form triangular cavitation cloud,which gradually move toward the trailing edge of the blade.The evolution of sheet cavitation on the suction surface(SS)is divided into the growth phase and the dissipation phase.The change in the incidence angle is the direct cause of this phenomenon.If the incidence angle is positive,the sheet cavitation develops on the SS;if the incidence angle is negative,the low pressure area on the SS gradually disappears and the sheet cavitation gradually decreases and dissipates.