Effect Of Gap Blade On The Performance Of Gas-liquid Multiphase Pump Under Gas Compressibility

Oil and gas are the lifeblood of national energy,and the innovation of their extraction and transportation technology can greatly save investment costs.Among them,multiphase transportation technology reduces the cost of gas-liquid separation process after oilfield development,and is favored by research institutions in various countries.In this paper,the helico-axial flow gas-liquid multiphase pump is taken as the research object,and numerical calculation is carried out based on the SST k-ωturbulence model.Study the influence of gas compressibility on the performance of gasliquid multiphase pump with different inlet gas volume fraction.Use the experience of the slotted flaps airline airfoils and slotted blades gap drainage technology,Two design schemes of multiphase pump blades are determined in this paper,blade gap width and blade gap deflection angle.The hydraulic performance changes of the modified multiphase pump were studied.The main research conclusions are as follows:(1)After considering the gas compressibility,there is a large deviation in the prediction of the external characteristics of the gas-liquid mulitiphase pump under high gas volume fraction.For the characteristic curve of the multiphase pump,when the inlet gas volume fraction is 80%,the efficiency difference of the multiphase pump under different gas compressibility is 4.3%,and the head difference is 9m.As for the internal flow field,the density of the mixed medium in the compression stage of the multiphase pump differs about 12% from that in the simulation of gas incompressibility,and the phase distribution of each flow channel in the multiphase pump is more uneven after considering the compressibility of gas,which leads to the uneven distribution of pressure field and turbulent kinetic energy.(2)The accumulation of air mass in the flow channel of the multiphase pump first appeared at the position of the leading edge of the suction surface,and then developed along the suction surface to the trailing edge,and the flow separation phenomenon in the middle of the blade was serious,so it was determined to open a gap in the middle of the blade.Numerical calculation is carried out for the models under 5 schemes of different gap width coefficients.It is found that the blade gap width coefficient has a critical value for the improvement of the hydraulic performance of the multiphase pump.After analyzing the pressure field,velocity field and vortex strength distribution,it is found that the optimal hydraulic performance of multiphase pump is when the blade gap width coefficient ξ is 28.6%.(3)After the optimal gap width was determined,five models with different gap deflection angles were designed.After numerical calculation,it was found that with the change of the gap drainage angle,the head efficiency curve shows a "hump" trend with the change of gas volume fraction.With the change of gap deflection Angle,the flow separation area and vortex strength distribution at the gap change obviously.With the increase of gap deflection angle,the flow separation at the gap inlet at the hub side is suppressed,but a larger flow separation area at the gap outlet is also caused.After comprehensive analysis,it is determined that the multiphase pump has the best performance when the deflection degree is 0.8.