Effect of Discharge Elbow on Performance of the Axial Flow Pump in Saddle Zone
Effect of Discharge Elbow on Performance of the Axial Flow Pump in Saddle Zone
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DOI：
10.5293/ijfms.2020.13.4.775
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发表时间：
2020-12
影响因子：
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通讯作者：
Xianfang Wu;Heyu Ye;M. Tan;Hou-lin Liu
中科院分区：
文献类型：
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作者：
Xianfang Wu;Heyu Ye;M. Tan;Hou-lin Liu
排出弯头是轴流泵系统的重要组成部分，性能曲线上的鞍区是轴流泵的一个特殊特性。为了揭示泄流弯头对轴流泵鞍区的影响，本文通过模拟和试验研究了两种不同泄流弯头(90°和60°)轴流泵的鞍区性能。首先，分析了排气弯头对泵能量性能的影响。结果表明，不同流量弯头的模型泵鞍区始终在0.5QBEP~0.6QBEP之间(QBEP代表最佳效率点处的流量)，扬程在0.55QBEP处最小。然后，对不同模型的压力脉动进行了分析。结果表明，与90°排量弯头模型相比，在各流量下，60°排量弯头模型叶轮进口和泵出口的压力脉动峰峰值均显著减小。当排液弯头为90°时，叶轮进口和泵出口压力脉动的主频为叶片通过频率FP，在鞍区出现较多的低频脉动分量。当排量弯头为60°时，泵出口压力脉动的主频由叶片通过频率FP变为轴向通过频率Fn。最后，通过数值模拟，给出了系统内特性的研究重点。研究发现，在马鞍区条件下，这两种排气弯头都出现了少量的涡流，而在泵出口延伸处出现了高速区。用60°泄流弯头代替90°泄流弯头后，流线分布更加均匀，涡流引起的水力损失减小。
The discharge elbow is an important part for the axial flow pump system, and the saddle area on the performance curve is a special characteristic of the axial flow pump. In order to reveal the influence of discharge elbow on the saddle zone, the saddle zone performance of an axial flow pump with two different discharge elbows (90° and 60°) is described in this paper by simulation and test. First, the effect of discharge elbows on pump energy performance is analyzed. The results indicate that the saddle zone of model pump with different discharge elbows is always between 0.5QBEP and 0.6QBEP (QBEP represents flow rate at the best efficient point), and the head value reaches the minimum at 0.55QBEP. Then, the analysis on pressure pulsation of different models is shown. The results show that compared to 90° discharge elbow model, the peak to peak value of pressure pulsation of 60° discharge elbow model at impeller inlet and pump outlet all reduces significantly under each flow rate. When the discharge elbow is 90°, the main frequency of the pressure pulsation at impeller inlet and pump outlet is the blade passing frequency fp, and many low-frequency pulsation components appear in saddle zone. When the discharge elbow is 60°, the main frequency of pressure pulsation at pump outlet changes from the blade passing frequency fp to the axial passing frequency fn. Finally, a focus by the numerical simulation about the internal characteristics is given. It is found that a small amount of vortex occurs in these two discharge elbows at saddle zone condition while the high speed area appears in pump outlet extend. After the 90° discharge elbow is replaced by 60° discharge elbow, the streamline distribution becomes more uniform and the hydraulic loss caused by the vortex decreases.