离心泵内实际的流动是三维、粘性、非定常的流动，空间任何一点的状态都是随时间变化的。国内外的大量实验和理论研究表明，水泵内非定常流动影响着叶片载荷、效率特性等各方面的性能。其中，空化和动静干涉是引起水泵内部压力脉动的两个主要因素。

The actual flow in centrifugal pump is three-dimensional, viscous and unsteady flow. The state of any point in the space varies with time. A large number of experimental and theoretical studies at home and abroad show that unsteady flow in pump affects the performance of blade load and efficiency. Among them, cavitation and dynamic interference are two main factors that cause pressure pulsation in pump.

与空化相关的压力脉动，对水力系统的稳定性、系统运行安全有很大影响，人们也对此展开了大量研究。目前空化流场中压力脉动的研究已涉及到多种装置系统，如反向磁盘[1]，灌排双向立式泵装置[2]、蝶形阀[3]、喷嘴[4]、诱导轮[5]、离心泵[6]和水轮机[7]等。基于大量研究可发现，汽蚀对压力脉动的影响（除叶频或轴频外）主要体现在两个方面，一是出现低频成分，周华[8]、王泽军[9]和李胜才[10]等通过试验得出低频压力脉动是空化发生的伴生现象。二是可能出现高频脉冲成分，是指空泡溃灭和回弹再生所发射的脉冲，在空化压力脉动中以高频分量的形式出现。通常空泡在破裂的过程中不但出现“噼啪”噪音，而且形成所谓的空化脉动，空化脉动诱导生成高频压力脉冲[11]。

The pressure pulsation related to cavitation has great influence on the stability of hydraulic system and the safety of system operation. A lot of researches have been carried out. At present, the research of pressure pulsation in the cavitation flow field has involved a variety of device systems, such as reverse disk [1], bidirectional vertical pump device [2], butterfly valve [3], nozzle [4], inducer [5], centrifugal pump [6] and hydraulic turbine [7], etc. Based on a large number of studies, it is found that the effect of cavitation on pressure pulsation (except blade frequency or axial frequency) is mainly reflected in two aspects. One is the emergence of low frequency components. The results of the experiments show that the low frequency pressure pulsation is associated with the occurrence of cavitation through the experiments of [8], Wang Zejun [9] and Li Shengcai [10]. The two is the possibility of high frequency pulse component, which means the burst of bubble collapse and the springback regeneration, and it appears in the form of high frequency component in the cavitation pressure pulsation. Generally, the "crackling" noise is not only appeared in the process of the cavitation, but also the so-called cavitation pulsation, and the cavitation pulsation is induced to generate high frequency pressure pulse [11].

研究表明，离心泵内部的动静干涉是引起压力脉动的主要原因之一，文献[12,13,14]成功地捕捉了叶轮-蜗壳的动静干涉作用引起的流场非定常流动特性。潘中永等[15]认为动静干涉是导致泵内部流动不稳定的一个重要原因，这种流动不稳定性最明显的特征就是引起的内部压力脉动的主频与叶片通过频率相同。Parrondo Gayo等[16]测试了离心泵蜗壳圆周方向的压力脉动，揭示了流量和叶片/隔舌位置是引起脉动的主要原因，并指出最大脉动值出现在距离隔舌最近的位置和小流量工况时。文献[17,18,19]指出，离心泵内部的压力以叶片旋转频率发生周期性变化，且额定流量时的压力波动幅度比偏工况时要小。倪永燕[20]和耿少娟[21]等也采用商用软件对离心泵全流道内进行了非定常湍流模拟，研究进一步表明叶轮和隔舌的动静干涉对叶轮流道出口压力脉动影响显著。

The research shows that the static and static interference in the centrifugal pump is one of the main causes of pressure pulsation. [12,13,14] successfully captured the unsteady flow characteristics of the flow field caused by the static and static interference of the impeller - volute. Pan Zhongyong and other [15] think that the static and static interference is an important reason for the instability of the internal flow of the pump. The most obvious characteristic of the flow instability is that the main frequency of the internal pressure pulsation is the same as the frequency of the blade passing through the blade. Parrondo Gayo and [16] test the pressure pulsation in the circumferential direction of the centrifugal pump volute. It reveals that the main cause of the pulsation is the flow rate and the position of the blade / tongue, and points out that the maximum pulsation occurs at the nearest position of the tongue and the small flow condition. Literature [17,18,19] points out that the pressure inside the centrifugal pump changes periodically with the rotating frequency of the blade, and the pressure fluctuation amplitude at the rated flow rate is smaller than that at the bias condition. Ni Yongyan [20] and Geng Shan [21] have also used commercial software to simulate the unsteady turbulent flow in the full flow channel of the centrifugal pump. The study further shows that the dynamic and static interference of the impeller and the tongue is significant to the pressure pulsation of the outlet of the impeller runner.

上述研究虽然使我们对空化和动静干涉引起的流场不稳定流动有了一定的理解，但二者相结合对水泵脉动的影响仍有待于深入研究。计算以一台在现场运行ns=270的双吸泵为例，对其在设计工况（1.0Qo）下，倒灌1m时的非定常空化流场进行压力脉动分析，旨在探寻该水泵振动的主要来源并给出有效的改进建议。

Although the above studies have given us a certain understanding of the unsteady flow in the flow field caused by cavitation and static interference, the effect of the combination of the two on the pulsation of the pump still needs to be studied. The pressure pulsation analysis of the unsteady cavitation flow field under the design condition (1.0Qo) for the inverted 1m under the design condition (1.0Qo) was carried out to find out the main source of the vibration of the pump and the effective suggestions for improvement were given in the case of a double suction pump running ns=270 on the spot.