Simulation Analysis Of Leakage Characteristics Of Elliptic Type Single Progressive Cavity Pump

Progressive cavity pump has excellent mechanical properties,suction performance and low cost,which makes it widely used in gas-bearing,sand-bearing and low-yield oil wells.Because the rubber stator is deformed under the pressure difference in the cavity,Leakage occurs when the differential pressure value is greater than the critical contact pressure of the stator and rotor,reducing the volumetric efficiency of the progressive cavity pump.In this paper,the leakage characteristics of the elliptic type single progressive cavity pump are studied.Based on the bidirectional fluid-solid coupling method,the influence of structural parameters,working parameters and other parameters of the progressive cavity pump on the leakage of the elliptic type single progressive cavity pump is explored,which provide a theoretical basis for the design,optimization and application of this type of progressive cavity pump.In this paper,based on the gap flow theory,according to the linear theory of the stator rotor of the elliptic type single progressive cavity pump and the leakage mechanism of the progressive cavity pump,the stator rotor is located at the specific division when it produces leakage,and simplifies the model to divide the progressive cavity pump leakage into two types.Through the linear contact lubrication theory,the parameters of the above two simplified models are solved,and the theoretical calculation formula of the total leakage of the elliptic type single progressive cavity pump in two different flow States is obtained.The simulation model of the elliptic type single progressive cavity pump is established to check the grid quality,including the grid quality coefficient and skewness,and to verify the irrelevance of the grid number and time step.According to the requirements of bidirectional fluid-solid coupling,the simulation conditions of fluid domain and solid domain were set respectively.Finally,the data connection is established in the system coupling module,and the same time step is set to solve the problem.For the simulation model of the elliptic type single progressive cavity pump with small clearance,a small clearance and small viscosity bidirectional fluid-solid coupling simulation calculation method is given.The simulation method is used to fit the simulation results numerically and to solve the equation of leakage as a function of gap variation for the actual viscosity of the elliptic type single progressive cavity pump.Based on the simulation model of the elliptic type single progressive cavity pump,the influence of different parameters on the flow field of the elliptic type single progressive cavity pump and the change rule of leakage were studied by controlling a single variable based on the bidirectional fluid-solid coupling method.By changing the structural parameters such as initial clearance,eccentricity and lead,it is concluded that the leakage increases with the increase of clearance.Leakage is positively correlated with eccentricity;The leakage increases with the increase of stator lead,and the increasing trend of leakage changes approximately linearly.By changing the inlet and outlet pressure,the pressure difference between chambers and the rotating speed and other working parameters,it is concluded that the inlet and outlet pressure changes have a great influence on the leakage.The leakage increases gradually with the increase of pressure difference,and it is approximately multiple to the pressure difference.The increase of leakage is proportional to the rotating speed.By changing the parameters such as viscosity of fluid medium and Poisson’s ratio of rubber,it is concluded that with the gradual increase of oil viscosity,the leakage shows a downward trend.The relationship between leakage and Poisson’s ratio of rubber is linear.