| Oil and gas mixed transportation technology is an efficient and economical way of oilfield exploitation in recent years.Axial oil-gas multiphase pump as the core equipment of oil and gas mixing technology,is a collection of conventional liquid pump and gas compressor performance in the integration of heterogeneous conveyer,It works in series with several compression stages,each compression stage consists of a impeller and a diffuser.As an important structural parameter,the semi-cone angle of hub has important influence on the compression stage performance of the oil-gas multiphase pump.Therefore,the study of semi-cone angle impeller and diffuser hub is special significance.This article choses the self-developed compression stage of YQH-100 helico-axial oil-gas multiphase pump as research object,numerical simulation was carried out under the condition of choosing the Mixture model,standard k-? turbulence model and using SIMPLE to calculate the velocity-pressure coupling,and discusses the influence law of the change about the size of semi-cone angle semi-cone angle impeller and diffuser hub on the compression stage performance of the oil-gas multiphase pump.The main research contents and conclusions are as follows:1.Five single compression stage of axial oil-gas multiphase pump schemes with the semi-cone angle of hub about 4.08°,6°,8°,10° and 12° were designed.The numerical simulation was carried out in five operating conditions with inlet gas volume fraction(GVF)of 0,10%,30%,50% and 70%.The results show that with the increase of the semi-cone angle of hub,the head of the impeller decreases firstly and then increases,the hydraulic loss of diffuser increases continuously.The head of the single compression stage of multiphase pump decreases firstly,then increases and decreases finally.The shaft power gradually decreases and the efficiency gradually increases.Under the same inlet gas volume fraction(GVF),the single compression stage of multiphase pump with different semi-cone angle of hub has better supercharging capacity,and the compression stage has the strongest supercharging capacity when the semi-cone angle of hub is 4.08°.The higher inlet gas volume fraction(GVF),the smaller pressure gradient from the inlet of impeller to the outlet of diffuser for the single compression stage of multiphase pump with the same semi-cone angle of hub.When the semi-cone angle of hub increases,the back-flow at the outlet of the impeller decreases,and more uniform distribution of gas within t he impeller,but the vortex flow increases in the diffuser channel.2.In order to take into consideration of the head and efficiency of the compression stage of multiphase pump,and considering the characteristics of the gas phase in the gas-liquid two-phase medium that can be compressed when the multiphase pump is operated in the field,a three-stage compression model scheme for oil-gas multiphase pump(New Model)with a step change in the semi-cone angle of hub is presented,recorded as “NM”.The numerical simulation was carried out in five operating conditions with inlet gas volume fraction(GVF)of 0,10%,30%,50% and 70%,respectively,and compared with the three-stage compression model of YQH-100 oil-gas multiphase pump(Original Model),record as “OM”,which is constant at all stages of the semi-cone angle of hub.The results show that with the increase of the inlet gas volume fraction(GVF),the head of NM decreases more slowly and the performance is more stably.The average head and efficiency of OM at different gas volume fraction are taken as reference.Under the same conditions,the average head of the NM is reduced by 0.52%,but the efficiency increases by 3.69%.Compared with the OM,there are fewer high pressure areas at the outlet of impeller working face of NM,the internal flow of impeller and diffuser is more smooth and the gas distribution on the flow channel is more uniform. |
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