Study On The Working Mechanism Of Hydraulic End Of Model 200 Vehicle Fracturing Pump

With wide application of fracturing technology in the exploitation of world oil and gas resources, the demand of fracturing equipment is rising and how to improve the performance of existing fracturing equipment has been one of the problems which need to be solved in the filed of oil and gas exploitation at present. Fracturing pump is the core of fracturing equipment, whose performance directly determines the quality of fracturing equipment. The working mechanism research on fluid end of fracturing pump is carried out so as to increase the service life of fluid end and increase the volumetric efficiency and performance of fracturing equipment. Based on the wide investigation on Dagang oilfield, downhole service company of Chuanqing drilling &exploration company and SJ petroleum machinery factory of Jianghan petroleum administration, the working mechanism on fluid end of 2000 vehicle-mounted fracturing pump is studied by using fluid mechanics, FEA and experimental verification according to existing problems.On the basis of some assumptions, second order nonlinear differential equation which describes the movement rule of the pump valve is derived and corresponding optimization is finished according to the influence of different spring rate and mass on the movement rule of pump valve.Based on the working mechanism research on fluid end, the finite element model of fluid end of fracturing pump is built and the simulation research is done by using fluid and structure interaction method. The contact status of pump valve, sealing washer and valve seat in different impact speeds is simulated and the causes resulting in the damage of sealing washer are found. The mathematical model and simulation are verified through experiment. Theoretical support is provided to improve the structure of existing fluid end and overall property of domestic fracturing pump.The details of the research are as follows:(1) The shortcomings of existing products and the direction of further development are pointed out according to the requirement of fracturing acidification construction situation and construction technology through the document searching at home and abroad and the site investigation in oilfields and factories. The further research on the problems such as the shorter service life of vulnerable part and lower volumetric efficiency is carried out.(2) Based on the fluid mechanics, the mathematical model which describes the movement rule of pump valve is derived and the influence of different spring rate and mass on the time lag and opening resistance of pump valve is studied. The reasons that volumetric efficiency loss is come about are analyzed and appropriate spring stiffness is found out to make volumetric efficiency better and opening resistance appropriate and improve the overall property of fracturing pump.(3) Based on the theoretical research, simulation on fluid end of fracturing pump is done by using fluid and structure interaction method and FSI module of ADINA software. Displacement and speed curves of pump valve in liquid medium in different spring stiffness and different valve mass and the positions where whirlpool produces in flow field are obtained. Corresponding speed change of fluid between valve and seat with the increase of valve spring stiffness is calculated and the positions where erosion and pierce are easily produced are found out. Theoretical basis and method are provided to improve the structure of fluid end components.(4) Combined with the fluid and structure interaction analysis of fluid end, contact analysis of pump valve, sealing washer and valve seat is finished by ABAQUS. According to different falling speeds, the positions and changes where stress and strain of these three parts produce are calculated and the influence of falling speed on stress and strain of these three parts is obtained. Comparing the contact status of these three parts in 50Mpa pressure, it is concluded that falling speed change which caused by the spring stiffness change of pump valve has no influence on the service life of fluid end and the main reason of valves damage is that the fluid speed between valve and seat is very fast and erodes the sealing washer.(5) According to the relative standards, the laboratory experiment program is designed with the consideration of the actual working conditions of fluid end and the content of theoretical research. Combining the experiment program and existing experimental conditions of our school, the testing experiment is carried out and the influence of different spring stiffness and mass of pump valve and different motor speed on the movement rule of pump valve is analyzed. The experiment results further verified that the mathematical model built in this paper and finite element simulation are correct.