On-orbit refueling and space circulation technologies involve the use of a space micropump to transport gas-liquid mixed fluids, which affects the gas-liquid mass transfer and dynamic behaviors. To predict dynamic mass transfer processes, our proposed dissolved and released models were applied to space micropump calculation after the verification of dissolved oxygen concentration and micropump energy characteristics. The mass transfer characteristics and gas-liquid states were investigated by combining the correlation analyses. The results show that the dissolved concentration and the volume fraction are considered to be strongly related to the mass transfer rate, and the effect of turbulence kinetic energy cannot be ignored particularly in impeller and volute. Based on this, the gas-liquid state parameters are focused on unidirectional dissolved and bidirectional released-dissolved conditions. The released gas occupied the head of the suction surface of the long blades and developed downstream, and its presence causes a significant gas increase in downstream. According to the mass-transfer characteristics comparisons, the oxygen increment deceases as the inlet dissolved oxygen concentration increases, exhibiting the similarity of two-film theory. In addition, the evolution increases the fluctuation in the gas volume fraction and the total hydraulic loss. The current study provides guidance for the fueling gas-liquid mixed delivery status, and the dissolved gas concentration must be controlled strictly to avoid the evolution of gas to ensure the safety and decrease the flow loss.

The purpose of this paper is to reveal the dynamic mass transfer effects between gas and liquid on pressure fluctuations in a space micropump using our proposed computational model of gas–liquid mass transfer. Complex dissolution and evolution processes were applied to achieve accurate dynamic gas–liquid mass transfer predictions in the micropump. The validation of experiments was conducted by measuring the performance characteristics of the micropump, and the mass transfer model was verified by a dissolved oxygen concentration experiment in plug discharge flow. Based on this, four conditions including unsteady single-phase, two-phase without mass transfer, dissolution, and coexisting dissolved–released flows calculations are discussed to clarify the frequency contents, generation reasons, and propagation law. Combined with entropy production analysis, the pressure fluctuation influenced by the dissolution and evolution is illustrated. The results exhibit that the evolution of the gas is located on the head of the long blade suction surface in the impeller. When a unidirectional gas-to-liquid dissolution process occurs, the fluctuating amplitude of the characteristic dominant 5 fn is significantly weakened; otherwise, when dissolution and evolution coexist, the amplitude is significantly promoted as the released gas increase the flow instability. In addition, the distributions of local high entropy production induced by mean and fluctuating velocity gradients overlap that of large mass transfer rates and high amplitude of the mixing frequency in the volute, exhibiting the relationship between entropy production, mass transfer, and flow instability. The current study provides a guidance that the dissolved gases’ concentration must be controlled strictly to avoid the evolution of gas for the safety and stability of the space hydraulic system.

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