不同工况下水泵水轮机尾水管压力脉动特性与改善措施研究

Research on Pressure Pulsation Characteristics and Improvement Measures of Pump Turbine Draft Tube under Different Working Conditions

不稳定水流诱发的压力脉动是引起水力机械振动进而影响水泵水轮机安全运行的重要原因。为研究不同流量下水泵水轮机尾水管涡带形态的演变,分析空化系数对涡带形态的影响,基于FBM湍流模型,针对水泵水轮机五种典型运行工况进行非定常数值模拟,重点比较了不同流量与空化系数对尾水管涡带形态的影响。结果表明,当机组运行在0.5倍和1.1倍设计流量时,空化的影响最为明显。为了缓解尾水管压力脉动,进一步探究了抑涡槽和导流隔板对尾水管内部流态和低频压力脉动的影响。流场分析表明,抑涡槽和导流隔板能有效改善尾水管直锥段内部流态和压力分布,同时使得扩散段内部流动变得更稳定,尾水管涡带引起的压力脉动幅值和水流圆周速度变化整体降低。

The pressure pulsation produced by the unstable flow is an important reason for the vibration of hydraulic machinery,which in turn affects the stable operation of the pump turbine.In order to study the vortex rope evolution in pump turbine draft tube under different flow conditions and analyze the influence of cavitation coefficient on vortex shape,this paper selects five typical flow conditions to simulate unsteady flows in the pump turbine based on the FBM turbulence model,and the analysis focuses on the influence of different flow rates and cavitation coefficients on the vortex shape in the draft tube.The results show that cavitation has the most obvious influence on the 50%and 110%Q_r(Q_r:rated flow discharge)flow conditions.Further,the effects of vortex suppression grooves and diversion baffles on the internal flow pattern in the draft tube and the low-frequency pressure pulsation due to the vortex rope are investigated.It is noted that the vortex suppression grooves and diversion baffles can effectively improve the internal flow and pressure pulsation in the straight cone of the draft tube.