轴流泵作液力透平飞逸过程瞬态流动特性研究

Research on Transient Flow Characteristics of Axial-flow Pump as Hydraulic Turbine during Runaway Transition

为研究轴流泵作液力透平在飞逸过程中的瞬态流动特性,使用Fluent软件中的用户自定义函数功能(User Defined Function,UDF),基于流动控制方程和RNG k-ε湍流模型对飞逸过程进行数值模拟,详细分析了其外特性参数变化、压力脉动特性以及不同流量工况和叶轮转动惯量对转速的影响规律。结果表明:在飞逸过程中,叶轮转速在极短时间内急剧上升,飞逸转速为初始转速的1.48倍,叶轮扭矩、扬程和轴向力变化情况基本相同,先急剧下降,然后出现微小上升,随后持续降低,最终达到稳定值;与导叶流道、叶轮流道和叶轮出口处相比,导叶与叶轮动静交界面处压力波动最为剧烈,而在动静交界面上,越靠近轮缘,压力波动幅度越大;在同一流量工况下,随着叶轮部件转动惯量的增大,飞逸时间也在增大,飞逸转速基本保持不变,在同一转动惯量下,当流量增大时,飞逸转速随之上升,且流量越大上升速度越快,而飞逸时间减短。

In order to study the transient flow characteristics of axial-flow pump as hydraulic turbine during runaway transition,the user defined function(UDF)in Fluent software was used to numerically simulate the runaway transition based on the flow governing equation and RNG k-εturbulence model.The changes of external characteristic parameters,the pressure pulsation characteristics,and the influences of different flow conditions and moment of inertia of impeller on the speed were analyzed in detail.The results show that during runaway transition,the impeller speed increases sharply in a very short period of time,and the runaway speed is 1.48 times of the initial speed.The changes of impeller torque,head and axial force are basically the same,which first decreases sharply,then increases slightly,soon after decreases continuously,and finally reaches a stable value.Compared with guide vane runner,impeller run ner and impeller outlet,the pressure fluctuation is the most severe at the interface between guide vane and impeller,while for the dynamic-static interface,the closer the interface is to the rim,the greater the pressure fluctuation is.Under the same flow condition,with the increase of the moment of inertia of the impeller component,the runaway time also increases,and the runaway speed basically remains unchanged.Under the same moment of inertia,when the flow rate increases,the runaway speed will rise,and the higher the flow rate,the faster the rise speed,while the runaway time decreases.