Transport Performance Of Axial-flow Multiphase Pump On Gas-liquid Mixture Is Improved Based On The Orthogonal Test

In the exploration of offshore crude oil,the technique of oil-gas mixed transportation can greatly reduce the exploration cost and improve the efficiency.As one of the most important equipment of oil-gas mixed transportation,the optimization and design of the multiphase pump are particularly urgent in contemporary era with the increasing demand for energy.In this paper,the orthogonal test design method and CFD technology are used to optimize the head and efficiency indexes under the rated flow rate with 15% inlet gas volume fraction.The blade shroud angles at the leading edge and trailing edge,and axial length of the impeller,as well as the inlet incidence angle and blade number of the diffuser,five factors in total are selected for the orthogonal test.The weight function is used to determine the final trial protocol.The performance curves,internal flow field and energy conversion characteristics of the pump before and after optimization were compared and analyzed,the point under rated flow rate with IGVF=15% are taken as example for energy conversion characteristics and internal flow field.The conclusions are as follows:(1)The first three factors,which have influence on the head and efficiency indexes,are the blade shroud angle at the trailing edge and leading edge of the impeller,axial length of the impeller.Among those factors,the blade shroud angle at the trailing edge has the greatest influence on the efficiency and head indexes,which indicates that the blade shroud angle at the trailing edge is a parameter which is of great importance in the multiphase pump.(2)After the optimization,the head and efficiency of the multiphase pump are improved under 0%-20% inlet gas volume fraction,and with the increase of inlet gas volume fraction,the head and efficiency is improved more.Under IGVF=20%,the head of the optimized pump is increased by 3.5m,and the efficiency is increased by 9.64% compared with the base pump.Under pure water points,the efficiency of each point is improved,however,the head is only increased near the rated flow rate.In the rated flow rate under pure water,the head of optimized pump is increased by 1m and the efficiency is increased by 1.47%.(3)The blade angle at the leading edge of the base impeller is less than the flow angle,which induce the passages at the inlet of the impeller forming a local high-speed area,and the blade suction surfaces forming a local low-pressure area,and then leading a negative increment of head at the inlet of the base impeller,and the greatly changes of pressurization capacity in each region.After the optimization,the local high-speed area at the inlet of the impeller disappears,and the local low-pressure area on the suction surface of the blade disappears.The pressurization capacity in each region of the impeller is positive,and the pressurization capacity of each region is more even.By the optimization of the blade angle at the trailing edge and the axial length of the impeller,the accumulation of gas phase on the blade suction surface at the outlet of the impeller is weakened,the flow-state is improved,and the energy loss is greatly reduced.both the pressurizing and conveying capacity on gas-liquid mixture of the impeller are greatly improved after the optimization.(4)After the optimization,the flow-state at the bladeless area between the impeller and diffuser as well as the inlet of the diffuser is better,the energy loss is smaller.It shows that the blade angle at the trailing edge of the impeller and the blade angle at the leading edge of the impeller match better.However,the pressure distribution at the outlet section of the diffuser is more uneven,which makes the flow-state more disorder,the phenomenon of gas phase accumulation increases,and energy loss increases.