Dynamic Analysis Of The Power End Of The Seven-cylinder Pump And Optimization Of Its Critical Components

With the progress of China's reform and opening up,China's energy demand for oil and other energy is also growing.The most important equipment for oil and gas exploitation is the fracturing pump that can pressurize the liquid.The seven-cylinder pump with better performance has been developed abroad,and the domestic oil and gas development has been gradually promoted to areas with deeper formation and lower permeability.Therefore,the research and development of fracturing pumps in our country is very urgent to develop to seven-cylinder fracturing pumps with higher power and displacement,in order to improve the efficiency of production and reduce its cost.In this paper,we review the relevant literatures on the design and performance of the fracturing pump power end at home and abroad,and clarify the main research contents and research methods of scholars and engineers,as well as the problems encountered in the actual oil and gas development of fracturing pumps designed and manufactured in China,it is applied to the dynamic analysis of the power end of the seven-cylinder pump and the research of the key optimization papers.In order to improve the pumping and discharging performance and stress of the pump,this paper proposes the crank angle configuration of the crankshaft of the seven-cylinder pump,and designs the Crank slider mechanism.The geometric and physical parameters are determined by three-dimensional modeling design,which provides data support for the dynamic analysis of the power end of the seven-cylinder pump,so that the variation of the force of each component during the rotation of the crankshaft is obtained.Secondly,the length of the crankshaft increases correspondingly due to the increase of the number of cylinders.To satisfy the bearing strength of the crankshaft,it is necessary to increase the number of main bearings of the crankshaft,so that it is necessary to double the machining accuracy and cost.In order to reduce the number of main bearings of the crankshaft to reduce the machining accuracy and cost,an optimization method for the number of main bearings of the crankshaft is proposed.The main research contents and research methods are as follows:1)The crank initial phase angle arrangement of the seven-cylinder pump crankshaft is preferably: In order to improve the problems of shutoff and sedimentation,flow fluctuations,and cavitation during suction and extrusion.Based on the three aspects of current interruption time,flow fluctuation and crankshaft force,the optimal design scheme for the crank arrangement of the seven-cylinder reciprocating pump is proposed.Through the suction pipe flow analysis,the crank initial phase angle combination scheme with short zero instantaneous flow duration is determined;the crank arrangement is optimized by analyzing the bending moment of the crankshaft.Finally,four layout schemes with small flow pulsation amplitude,small inertia head loss and good crank force are obtained,thereby:(1).Effectively improve the problem of cutoff sediment and cavitation;(2).Reduced The flow pulsation amplitude of the seven-cylinder reciprocating pump reduces the inertia head loss;(3).Improves the stress of the crankshaft,thereby improving the service life and reliability of the seven-cylinder reciprocating pump.2)Structural design of the crank slider mechanism: According to the API standard and the reciprocating pump design manual,referring to the design specifications of the five-cylinder pump,according to the general principles of crank structure design,the relevant parameters are selected and the maximum connecting rod load is determined;according to the empirical formula of the reciprocating pump design,the crankshaft,The main dimensions of the connecting rod and crosshead are checked for strength.3)Dynamic analysis of the power end of the seven-cylinder pump: According to the structural dimensions and material parameters obtained from the design of the crank-slider mechanism,the three-dimensional design of the UG three-dimensional modeling software is used to determine the geometric parameters to determine its quality.First,the power of the seven-cylinder pump is determined.The end link and the crosshead mechanism are analyzed for motion to obtain the relevant motion characteristics of the connecting rod and the crosshead as the crankshaft rotates.Secondly,the crosshead and the connecting rod are subjected to force analysis,and the dynamic equilibrium equations are established and solved to obtain the joint.The various forces that the rod and the crosshead are subjected to;the final analysis results in the force of the crankshaft.4)Optimization of the number of main bearings of the crankshaft and the structure of the connecting rod body: The finite element software ANSYS workbench is used to simulate and optimize the number of main bearings of the crankshaft.The main supporting scheme is determined by discussing the number of main supports and their arrangement;then the crankshaft of different schemes is determined.The analysis of stress and deformation,through the theoretical analysis of the combination of the stress and bending moment of the crankshaft and the structural simulation of the crankshaft,optimizes the main support quantity scheme;In order to obtain the shape of the connecting rod that meets the requirements of strength and stiffness,light weight and reasonable structure the section size,the structure of the connecting rod is optimized by means of ANSYS workbench.The main conclusions of this paper are:(1)Four kinds of crank initial phase angle layout schemes with better suction performance and minimum bending moment of crankshaft are obtained;(2)The movement law of the speed and acceleration of the connecting rod and the crosshead with the phase angle of the crankshaft,the role of the crankshaft slider mechanism and the crankshaft are obtained.The law of force changes with the increase of the phase angle of the crankshaft;(3)Under the premise of satisfying the design requirements of crankshaft strength and stiffness,a six-point support scheme with relatively low requirements on crankshaft material and machining accuracy and minimum number of supports is obtained;(4)From stress relief and weight reduction The structure of the rod body is optimized,and finally the outer shape of the connecting rod body with the smallest stress peak and light weight is obtained.