基于CFD的离心泵叶片水力矩非定常特性

Unsteady characteristics of blade hydraulic moment in centrifugal pumps with CFD

为研究离心泵叶片水力矩的非定常特性,利用CFD技术对XS50-160/7.5型离心泵内部流场进行三维非定常数值模拟,并通过离心泵能性能试验验证了数值模拟的有效性与准确性.通过模拟得到不同工况下叶片水力矩和叶片表面各监测点的压力脉动情况,并对其进行了分析.分析结果表明:在各工况下,叶片通过频率分量在叶片水力矩脉动中均占主导地位,泵轴转动频率分量在叶片表面压力脉动中均占主导地位;当频率大于叶片通过频率后,水力矩脉动强度与叶片表面压力脉动强度均相对较小;在设计工况下,叶片水力矩强度的RMS(均方根)值最小,偏离设计工况点越远,其RMS值越大,小流量工况和大流量工况下水力矩强度的RMS值相对于设计工况点近似对称分布;叶片压力面压力脉动强度大于吸力面压力脉动强度,叶片进口处压力脉动强度远小于叶片出口处压力脉动强度.

Unsteady characteristics of blade hydraulic moment in centrifugal pumps are key factors having strong influence on pump operation. There is few literature on the unsteady hydraulic moment currently. Thus, with CFD technology, the 3D unsteady flow numerical simulations were executed on a model of XS50 - 160/7.5 pump for capturing the flow character inside the impeller under 5 different operation conditions. An experiment has been done for verification of the validity and accuracy. The hydraulic moment fluctuation and the pressure fluctuation on blade surface under 5 different operation conditions were obtained with the simulation. The results of the simulation show that the blade passing frequency plays a dominant role in the fluctuation of the hydraulic moment at design and off-design conditions under various operating conditions. Meanwhile, the rotating frequency of impeller plays a dominant role in the pressure fluctuation in the impeller at design and off-design conditions. When the frequency is higher than the blade passing frequency, the strength of hydraulic moment pulsation and pressure pulsation on the surface of blade are both relatively weak. At design point, the minimum RMS of the hydraulic moment fluctuation occurred. With the deviation from the design point, the RMS value goes higher. The RMS values at low flow rate condition and at high flow rate condition are almost symmetrically distributed about the design point. The pressure fluctuation in the pressure surface of the blade is stronger than that in the suction surface, that in the outlet zone is stronger than in the inlet zone.