Unsteady energy transfer characteristics of gas–liquid two-phase multiphase pump based on pulsation statistics

•The average energy transfer and energy loss mechanism in the multiphase pump are studied comprehensively.•The statistical distribution of unsteady energy pulsations in the multiphase pump is analyzed.•The energy conversion characteristics between gas and liquid phases in the multiphase pump are clarified. Multiphase pump is a special type of pump for conveying gas–liquid two-phase medium, which has a wide range of applications in marine energy engineering. The unsteady energy transfer process in multiphase pumps when transporting gas–liquid two-phase medium is completely different from that when transporting pure liquid. In this paper, the experimental testing and numerical simulation research methods are combined, the average energy transfer, energy pulsation distribution and energy conversion between gas and liquid phases in the multiphase pump are studied comprehensively. Based on the energy transfer theory and statistical distribution results of energy pulsation, a direct flow field analysis tool was constructed to determine the specific location and intensity of gas relative pressure fluctuations. The energy conversion and transfer relationship between gas–liquid two phases was established, and the transfer process between gas-phase energy and liquid–phase energy in multiphase pump are discussed. Then, the energy transfer characteristic mechanism in the flow field of multiphase pump is elucidated. It is found that the accumulation of gas will lead to the blockage of the average energy transfer and the decrease of the efficiency and shaft power. The kinetic energy pulsation in the multiphase pump becomes stronger and the potential energy pulsation is significantly improved under the gas-containing condition. More mechanical energy in the impeller is converted into unstable energy pulsation, which brings greater instability. With the increase of the volume fraction of the imported gas, the energy transfer process between the gas and liquid in the multiphase pump is more intense, resulting in more entropy production loss, and the thermal efficiency of the pump decreases. The research results can provide theoretical basis and reference for the study of energy transfer characteristics of multiphase fluid machinery.