Effect Of Trailing Edge Flap On Performance Of Helical Axial Flow Multiphase Pump

The efficient development of deep-sea oil and gas resources is of great strategic significance to the safe supply of energy.The multi-phase mixed transportation technology with multiphase pump as the core can be more low-carbon,energy saving and efficient for the development of deep-sea oil and gas fields.Among them,the helico axial flow multiphase pump has become the preferred pump type for its advantages of simple structure,large conveying flow and insensitivity to solid particles.However,when it is transporting multi-phase fluid medium with high gas content in the process,there is obvious phenomenon of gas pocket in the impeller passage,which further affects the transport efficiency.Therefore,improving the transport efficiency of multiphase pump with high gas volume fraction has become an urgent problem to be solved in the industry.Based on Euler multiphase flow model and SST k-ωturbulence model,numerical calculation of multiphase pump under different inlet gas volume fraction conditions is carried out in this paper.Through the analysis of its characteristic curve and internal flow characteristics,the influence of different inlet gas volume fraction on the performance of the multiphase pump and the cause of gas blocking phenomenon are explored.Using the idea of trailing edge flaps for reference,the separation trailing edge flaps were designed for multiphase pump blades.After exploring the optimal deflection Angle and length,the mechanism of improving gas pocket was analyzed.On this basis,the design of segmental trailing edge flaps can further improve the hydraulic performance of the multiphase pump.The main conclusions are as follows:（1）When the multiphase pump is transporting the multiphase fluid medium with high gas content,the phenomenon of gas blockage in the impeller passage occurs,and with the increase of the inlet gas volume fraction,the gas blockage is more serious;through the study of the original multiphase pump model,it is found that the internal cause of gas blockage is the difference in the density of the gas-liquid two-phase fluid medium,and the external cause is the generation of gas-liquid separation and gas retention in the impeller channel.（2）Referring to the trailing edge flap of the aerofoil and wind turbine blades,combined with the internal flow state of the multiphase pump,the separated trailing edge flap is established based on the 791 aerofoil;the characteristic curve and internal flow characteristics of 25 schemes of the multiphase pump were analyzed from two aspects of variable trailing edge flap deflection angle and variable trailing edge flap length.It was found that when the separated trailing edge flap length was 25%l₀ and the deflection angle was 5°,the transportation efficiency of the multiphase pump was the highest,which was 3.40%higher than that of the original model under the condition of 50%inlet gas volume fraction.（3）By analyzing the pressure field of different schemes of separated trailing edge flaps,it is found that the mechanism of improving the gas blocking phenomenon in the impeller passage is as follows:reducing the radial pressure gradient to reduce the degree of gas-liquid separation and reducing the inverse pressure gradient to reduce the degree of gas retention,which can comprehensively improve the gas blocking phenomenon in the impeller passage.（4）The improved design of the separated trailing edge flap with flap length of 25%l₀was carried out to establish the segmental trailing edge flap.The analysis of 10 schemes from two aspects of variable flap 2 length and deflection Angle showed that:when the length of flap 2 is 15%l₀ and the deflection Angleθ₂ is 4°,the transport efficiency is the highest,which is 3.52%higher than that of the original model under the condition of 50%inlet gas volume fraction.In addition,the loss of pressurization capacity is minimal and the gas blockage phenomenon is fully improved.Compared with the optimal scheme,the head of separated trailing edge flaps is improved by 3.91%.