Rongsheng Zhu

Effect of gas quantity on two-phase flow characteristics of a mixed-flow pump

The inlet gas quantity has a great influence on the performance and inner flow characteristics of a mixed-flow pump. In this article, both numerical and experimental methods are used to carry out this research work. The effects under the steady gas volume fraction state and the transient gas quantity variation process on the mixed-flow pump are investigated and compared in detail. It could be concluded that the head of the mixed-flow pump shows slight decline at the low gas volume fraction state, while it decreases sharply at the high gas volume fraction state and then decreases with the increasing gas quantity. There is an obvious asymmetric blade vapor density on the blade suction side under each cavitation state. The cavities can be weakened obviously by increasing the inlet gas volume fraction within a certain range. It has little influence on the internal unsteady flow of the mixed-flow pump when the gas volume fraction is less than 10%, but the pump starts to operate with a great unsteady characteristic when the inlet gas volume fraction increases to 15%.

Cavitation of dissolved oxygen liquid water under negative pressure

ABSTRACT Cavitation is widespread, but there has been a large difference between experiments and theories about cavitation. In this manuscript, the effects of oxygen molecules on the bubble nucleation of dissolved oxygen liquid are studied by molecular dynamics (MD) simulation using flexible water molecules. The results show that the maximum critical negative pressure calculated by liquid water with dissolved oxygen molecules is −165 MPa ∼ −170 MPa, and the magnitude of bubble nucleation rate is 35. The critical negative pressure of liquid water is mainly determined by the interaction of water molecules in liquid water. The effect of oxygen dissolved in water is mainly reflected in the ability to rapidly ‘catalyse’ the generation of bubbles. Through the analysis of the electrostatic interaction of the system, it is found that the difference between the experiment and the MD simulations and the fact that the bubbles finally formed are cavities are due to the selection of the water molecule model.