Determination of stage-wise pressure pulsation in a vertical multistage electrical submersible pump

摘要

Centrifugal-type electric submersible pumps (ESPs) are extensively utilized in agriculture, oil and gas industries, and several other industrial applications. Such ESPs are designed to be used at various operating conditions due to which a pulsation in the pressure field is present inside the pump. The pressure pulsation causes flow-induced vibration which probably can lead to a failure of the pump components. Since the role of the pump is critical in industries, condition monitoring during the operation of the pump is important. This article reports the results of an experimental investigation of mapping of pressure pulsation characteristics with speed and stage in a multistage ESP when it is operated at three different flow rates of 0.8Q(n), Q(n), and 1.2Q(n) at five speeds. Pressure pulsation measurements are conducted on each stage of a five-stage vertical submersible pump using miniature pressure transducers at 0.8Q(n), Q(n), and 1.2Q(n) for various speeds. To describe the origin and development of the pressure pulsation, a Fast Fourier Transformation (FFT) was performed on the signals. Results have indicated that at all these three flowrates when the ESP is operating at the highest speed 1.2N(n), the pressure pulsation is maximum at stage 2 and stage 4. The amplitude of pressure pulsation was found maximum at 1/2nd harmonic followed by the value at 1st harmonic, respectively. The experimental results have shown that stage 4 experienced the maximum amplitude of pressure pulsation at the highest operating speed of 1.2N with magnitudes of 331.33, 380.81, and 406.54 kPa, respectively at 0.8Q(n), Q(n,) and 1.2Q(n). Further, it was observed that the influence of sub-harmonics is present at stages of ESP irrespective of discharge and speed which indicated that the inherent flow field inside the stages of a multistage ESP is completely nonlinear and complex.