Investigation of pressure pulsation and unsteady multiphase flow characteristics in multiphase rotodynamic pump using dynamic mode decomposition

With the development of offshore oil fields, gas–liquid multiphase mixed transport technology has attracted more attention by various countries for its remarkable economic benefits. Due to its capability to pump out large gas content, compact structure, and insensitivity to solid particles, so the multiphase rotodynamic pump (MPP) is operating in many gas–oil fields. By the mean of dynamic mode decomposition method, the unsteady flow field and mechanism of pressure pulsation are analyzed, the main flow field structures are extracted, and its complex flow field is decomposed into flow field characteristics in the second compression cell with different energies and frequencies, including basic mode characteristics, dynamic mode flow field characteristics of rotor–stator interaction, and its high-order harmonic behavior. In different locations of second stage, intricate pressure pulsation characteristics occur and harm the MPP operation and ruled by various frequencies. The mutual matching of different rotor and stator blade numbers resulting in a rotor–stator interaction frequency in impeller and diffuser, which will excite higher harmonics of the impeller blade frequency. At low inlet gas volume fraction (IGVF i.e., 10%), there are low-and high-pressure pulsation in the impeller and diffuser flow passages. However, under high IGVF (i.e., 20%), the pressure pulsation is characterized by low- and high-pressure pulsation in the impeller passage, while in the both diffuser conditions there are groups of flow passages of low- and high-pressure pulsation.