| The world is facing a serious energy crisis and exploration of offshore oil,natural gas and other resources is imminent event.The transportation of related resources of equipment is particularly important while the traditional transportation equipment is lower efficient,higher malfunction rate.Helical axial flow oil-gas multiphase pump has stable performance and can transfer large flow of fluid with a strong conveying capacity for complex multi-media fluids and high gas volume fraction fluid.This article selects a set of complete multiphase pump model as the base model,using Advanced Computational Fluid Dynamics in the Eulerian multiphase flow model and RNG ?-? epsilon turbulence model for numerical simulation,then analysing the data of the results of numerical calculation of internal flow field of multiphase pump,at last summing up channel flow characteristics in the compression unit level flow channel and the bubble motion trajectory.This essay gives the define of Relative volume of gas as standard of evaluating levels of gas phase aggregation phenomenon,which fit in all operating condition for various of entrance gas volume fraction.After exploring the flow law of impeller channel,this paper put forward curved blade and twisted blade as two different remodel design which was proposed based on the translation and torsion of airfoil section,then gives the define of Torsion Degree as the coefficient to measure the degree of blade distortion,at last summing up the conclusion about the influence of different modification schemes on the gas phase flow characteristics of the multiphase pump through numerical simulation on the modification scheme.The main conclusions are as follows:(1)There are differences and similarities in the movement trajectory of bubbles on each flow surface in impeller channel while the movement trajectory of bubbles is similar to the path of a flat throwing ball;In the front section of the flow channel,the major influence factor of controlling the movement trajectory of bubbles is the extrusion effect between gas and liquid phase mainly caused by the radial pressure gradient force;Near the outlet of the flow channel,the main factor affecting the bubble trajectory is the adverse pressure gradient formed by the pressure side and suction side of the blade outlet.(2)While the curved blade formed by the translation of the hub wing section is bent to the suction side,this modification scheme can effectively reduced Relative volume of gas in impeller channel and resist the formation of backflow vortexes at the trailing edge of the back blade.In the process of that the curved blade is bent to the suction side from the pressure side with wing section translated from +3mm to-3mm,the reflux vortex near the impeller channel outlet gradually decreases until disappears.(3)While the twisted blade formed by the torsion of the hub wing section in the leading edge point of the hub wing section as the torsion center twisted towards to the direction of the pressure side,this modification scheme can alleviate the gas phase accumulation phenomenon at the trailing edge of the blade;In the process of that the twisted blade is distorted to the pressure side from the suction side with Torsion Degree changed from-0.214 to +0.214 linearly,the Relative volume of gas reduced to 0.15 from0.181 in the latter half of the impeller channel of the multiphase pump.(4)While the twisted blade formed by the torsion of the hub wing section in the center of the chord length of the hub wing section as the torsion center twisted in the counterclockwise direction,this modification scheme has helpful functions on reducing the Relative volume of gas;In the process of that the tailing of the twisted blade distorted to the pressure side from the suction side and the head of the twisted blade distorted to the suction side from the pressure side with Torsion Degree changed from-0.214 to+0.214 linearly,the Relative volume of gas reduced to 0.145 from 0.179 in the latter half of the impeller channel of the multiphase pump.(5)While the twisted blade formed by the torsion of the hub wing section in the trailing edge point of the hub wing section as the torsion center twisted towards to the direction of the suction side,this modification scheme has the helpful functions on accelerating the movement of the gas-liquid mixture at the trailing edge of the back blade,and further reducing the low-speed zone on the back of twisted blade.In the process of that the twisted blade is distorted to the suction side from the pressure side with Torsion Degree changed from-0.214 to +0.214 linearly,the Relative volume of gas reduced to0.129 from 0.175 in the latter half of the impeller channel of the multiphase pump with disappearing the backflow vortex at the trailing edge of the back blade basicallyInnovation points of this paper:This paper get the date of radial velocity and axial surface speed in the flow stream surface meshing through the finite volume method;then using the method of summation to deal with radial velocity and axial surface speed in each meshing node and using the method of average to get the correspondingly average radial velocity and average axial surface speed in single meshing;using integral thoughts on channel flow surface radial velocity and axial surface velocity of the cumulative sum,ultimately getting bubble trajectory diagram and mathematical expression of motion trajectory. |
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