闸门慢速启动下水泵机组起动过程水力稳定性研究

Influence of Gate Slow Start on Hydraulic Stability of Pump Unit during Start-up Process

摘要:

为探究水泵机组起动过程中，闸门慢速启动对机组水力稳定性的影响，建立了泵机组全过流几何模型，采用铺层网格和动网格技术实现闸门运动和转轮旋转，分别对不同闸门启动速度下的水泵机组起动过程开展了三维数值模拟。设置3种不同闸门启动速度的控制方案，从外部参数变化、压力脉动特性和内流特性3个角度探究闸门慢速启动对水泵起动过程水力稳定性所产生的影响，结合熵产理论量化了不同区域的能量损失，进一步分析了泵起动过程中的能量损失变化。研究结果表明，不同控制方案在外部参数、压力波动、水头损失等方面表现出相似的演变趋势，但在时间进程和变化幅值上存在差异。在起动过程中，减慢闸门启动速度将减慢流量变化，减慢外特性参数的回落速率，方案1、2、3的进口流量分别于12.2、25.4、56.4s达到运行流量值；增大转矩和轴向力的波动幅值，同时增大机组内压力峰值和压力脉动峰峰值。水头损失方面，减慢闸门启动速度对能量损失的影响具有明显的时域双重性：加速阶段以增损为主，而后期则转为抑损。

Abstract:

In order to explore the influence of gate slow start on the hydraulic stability during the start-up process of the pump unit, a full-flow geometric model of the pump unit was established, and the gate movement and runner rotation were realized by using the laying mesh and dynamic mesh technology. The three-dimensional numerical simulation of the start-up process of the pump unit at different gate opening speeds was carried out. Three control schemes with different gate opening speeds were set up to explore the influence of gate slow start on the hydraulic stability of the pump startup process from the perspectives of external parameter changes, pressure pulsation characteristics and internal flow characteristics. Combined with the entropy production theory, the energy loss in different regions was quantified, and the change of energy loss in the pump starting process was further analyzed. The results showed that different control schemes showed similar evolution trends in external parameters, pressure fluctuation and head loss, but there were differences in time process and change amplitude. During the starting process, slowing down the opening speed of the gate would slow down the flow change and the falling rate of the external characteristic parameters. The inlet flow of Scheme 1, Scheme 2 and Scheme 3 reached the operating flow value at 12.2s, 25.4s and 56.4s, respectively. It would also increase the fluctuation amplitude of torque and axial force, and increase the peak pressure and pressure pulsation peak-to-peak value in the unit. In terms of head loss, the influence of reducing gate speed on energy loss had obvious time-domain duality: in the acceleration stage, the energy loss was mainly increased, while in the later stage, the loss was reduced.