Experimental investigation of the flow at the entrance of a rotodynamic multiphase pump by visualization

In order to minimize the negative influence of mixed conditions at the entrance of a rotodynamic multiphase pump (MPP), a buffer tank was designed and installed in front of the pump. The structure of the buffer tank and the scheme of openings on the central porous pipe were designed and presented in this study. Visualization tests were conducted under different conditions to verify the rationality of the design buffer tank. Two indexes, i.e. the flow pattern for the gas-liquid two-phase flow and the distribution law for the bubble size, were used to evaluate the performance of the device. The test results showed that uniform bubble flow was presented after the mixture passes through the buffer tank and no aggregations of big bubbles were observed. It indicated that the flow pattern of the mixture was optimized with the designed structure of the buffer tank and the opening scheme on the central porous pipe. It can be concluded that the buffer tank enables the perfect mixture of the gas and liquid fluid. A set of experiments were also conducted to study the distribution of the bubble sizes and bubble numbers with the inlet gas volume fraction and rotation speed. The variations of bubble size with inlet gas volume fraction (IGVF) and rotation speed were plotted. It was shown that bubble sizes grew up with the increase of the IGVF but decreased with the increasing rotation speed. In addition, curves are drawn to express the relationship of bubble size with IGVF and rotation speed.