The Research On The Design Of The Compressing Elements Of An Oil-gas Multi-phase Pump Based On Numerical Simulation Of Stage By Stage

The helical axial multiphase pump has advantages of compact structure,and insensitivity to solid particles,and has broad application prospects as the core element of production system.Due to the compressibility of gas,when the fluid is crossing in the multiphase and the compressibility results in the flow parameters’ changes of the gas volume flow,volume flow and liquid flow angle and so on.Nevertheless,the structure parameters of stage by stage of multiphase pump used in our country remain same,and the change of flow parameters would definitely lead to the phenomenon that the flow parameters do not match the structural parameters.In order to reduce the hydraulic loss caused by the mismatch between the structural parameters and state parameters,the performance of multiphase pump is improves by adjusting the geometric structure of compressing units of stage by stage.The paper takes the helical flow multiphase pump as the research object.Commercial software CFX is used to do the numerical simulation of the model.And the research on the flow parameters in multiphase pump is conducted first,and studies the process of change of flow parameters in compressing elements.The conclusion is as follows: the volume flow and flow angle both decrease while the fluid is flowing in the compression elements,and the value tends to decrease gradually.And then the diameter and the blade placement angle of each impeller are adjusted according to the change value of volume flow and flow angle.Secondly,the paper uses three theoretical research methods to determine the diameter of impeller hub,including flow coefficient and speed at the entrance and empirical value,and the hydraulic performance of the multiphase pump with different hub diameters determined by each method is compared to select the excellent structural parameters.Eventually,the hub diameters of impellers determined by the flow coefficient method had the best performance of the multiphase pump.As for the installing angles of the impellers,adjusting the installing angles of the impellers based on the change value of impacting angle to reduce the loss of impacting and improve the hydraulic performance.Finally,the model was re-established and simulated according to the hub diameters determined by the flow coefficient method and compared with the results of the unadjusted model to verify the enhancement of performance on the basis of the changes of structural parameters.The results show that at high gas volume flows and high rotational velocity,the hydraulic efficient of the multiphase pump increased by 4%.Therefore,under the premise that the gas in the multiphase pump is compressible,the hub diameter and blade placement angle need to be reduced according to the actual flow parameters in the multiphase pump,and improving the hydraulic performance of the multiphase pump.