Study On The Gas-liquid Flow Of Helical Axial Oil-Gas Pump

With the development of petrochemical industry,a large number of oil-gas mixed transportation equipment are needed in oil exploitation,transportation and oil refining fields.Traditional centrifugal pump is hard to realize the oil-gas mixed transportation,and screw pumps are mostly widely used for oil-gas multiphase pumps.Screw pump as a displacement pump,has lower rotation speed and larger size.Its hydraulic performance is highly sensitive to the solid particles in mixed multiphase flow.The helical axial oil-gas pump now has become the focus of researchers due to its high rotation speed,and the hydraulic performance isn't sensitive to the solid particle.The complex gas-liquid two phase flow in helical axial oil-gas pump,and the complicated relation between the geometry of blade passage,internal flow and hydraulic characteristics would result in the difficulty for optimization design of helical axial oil-gas pump.In this research,the gas liquid flow in helical axial oil-gas pump was numerical simulated,and the Influence of guide vane structure on flow field were analyzed.The major research content and results are as follows:1.The gas-liquid flow in helical axial oil-gas pump was simulated with Euler twofluid multiphase models and k-? SST turbulence model.The reliability of the numerical simulation was verified by using Verification and Validation method(V&V)with three different grid number.The hydraulic performances of the simulation results and the experiment results were compared.The simulated hydraulic performances basically agree well with the experimental results.2.The distribution of gas void fraction increases gradually with the increasing of span from hub to rim in helical axial oil-gas pump,and there is obvious wake flow at the outlet of impeller blade.The distribution of gas void fraction in guide vane tends to be uniform.The pressure distribution also increases gradually with the increase of span.the pressure increases gradually from the inlet to the outlet of impeller,and tends to be uniform at the outlet of guide vane.With the increase of flow rate,the pressure at each span of blade decreases gradually.The velocity of the gas-liquid mixture in the guide vane decreases,and the kinetic energy is converted into pressure energy.With the increase of the flow rate,the impact velocity at the inlet of the impeller blade increases,and with the increase of the blade height,the impact velocity gradually decreases,and the velocity field wake at the outlet of the impeller vane is obvious.3.The inner flow structure and hydraulic performance of the guide vanes with or without short blades under different air contents were analyzed.With the increase of pump inlet gas content,the efficiency and head curve of the oil-gas pump move downward gradually.4.Compared with the hydraulic performance of the helical axial oil-gas pump with different guide vanes and different pump inlet air contents,we can see that the head of the helical axial oil-gas pump with short guide vanes decreased under different air contents,the head decreased significantly under 30% GVF,the efficiency curve increased under 40% GVF,and the efficiency decreased significantly under 30% GVF.5.The flow field in guide vanes with or without short blades was compared and analyzed,and we can see that gas and liquid are mixed more evenly in guide vane with short blade,and there is a local high gas content region in each flow passage of guide vane without short blade.With the increase of flow rate,the phenomenon of gas-liquid separation in guide vane without short blade becomes more and more serious.6.The unsteady characteristics of the flow field at the guide vane outlet of the helical axial-flow oil-gas pump with different guide vane are analyzed,and we can see that the amplitude of the pressure fluctuation dominant frequency is increases with the increase of the span value from the hub to shroud for both kinds of guide vane.The amplitude of pressure fluctuation for the guide with short blades is reduced obviously with respect to the guide without short blade.