The existence of pressure pulsations greatly increases the vibration and noise of pumps and harms their service life. In this paper, a casing treatment was employed to explore its impact on the pressure pulsations. A U-tube type groove was created at the inlet end-wall of a centrifugal pump and front cover of the impeller to connect the impeller with the inlet pipe by passing impeller leading edge. An unsteady numerical investigation was launched of the pump with and without this casing treatment, to study its influence on the pressure pulsations inside the pump and the mechanisms behind. The numerical results of the pump without casing treatment was first compared with the test performance of the pump to validate the numerical method, and gave excellent agreements with the test results. The CFD results also showed that the casing treatment increases the head coefficient and efficiency of the pump. Pressure pulsations at a reduced mass flow condition were studied by monitoring unsteady pressure signals generated by the CFD at various locations inside the pump. A Fast Fourier transform (FFT) was performed on the signals. The pump employs a double tongues volute with each tongue covering 180∘ circumference. However, the two tongues are not identical with regard to the discharge of the pump. These geometric features of the volute and the pump’s operating condition generate several pressure pulsations in the frequencies of fn, 2fn, 3fn in the original pump. Due to the circumferential unifying capability of the casing treatment and its improvement to the impeller flow, these pulsations at impeller inlet are weakened or disappear when the U-tube is present. The pressure pulsation inside the impeller is less affected by the treatment. The 3fn pulsation at volute tongues also decreases or disappears for the same reasons, but fn pulsation increases slightly and this is due to the improved pressure recovery in the volute by the treatment which increases the pressure difference across one of the volute tongues. The unsteady radial force of the impeller exerting on journal bearings becomes more uniform and smaller when the casing treatment is employed.

中文翻译：

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U型管套管处理对离心泵小流量工况压力波动的影响

压力脉动的存在大大增加了泵的振动和噪声，损害了泵的使用寿命。在本文中，采用套管处理来探索其对压力脉动的影响。在离心泵进口端壁和叶轮前盖处开有U型管槽，通过叶轮前缘将叶轮与进口管连接起来。对带有和不带有这种套管处理的泵进行了非定常数值研究，以研究其对泵内压力脉动的影响及其背后的机制。首先将未经套管处理的泵的数值结果与泵的试验性能进行比较，以验证数值方法，并与试验结果非常吻合。CFD 结果还表明，套管处理提高了泵的扬程系数和效率。通过监测由 CFD 在泵内不同位置产生的不稳定压力信号，研究了减少质量流量条件下的压力脉动。对信号执行快速傅里叶变换 (FFT)。该泵采用双舌蜗壳，每个舌覆盖 180∘圆周。然而，这两个舌片在泵的排放方面并不相同。蜗壳的这些几何特征和泵的运行条件会产生几个压力脉动，频率为Fn,2Fn,3Fn在原泵中。由于套管处理的圆周统一能力及其对叶轮流动的改善，当U形管存在时，叶轮入口处的这些脉动会减弱或消失。叶轮内部的压力脉动受处理的影响较小。这3Fn出于同样的原因，涡舌处的脉动也会减少或消失，但Fn脉动略有增加，这是由于通过处理提高了蜗壳中的压力恢复，这增加了穿过蜗壳舌片之一的压力差。当采用外壳处理时，叶轮施加在轴颈轴承上的非定常径向力变得更加均匀且更小。