| Progessing Cavity Pumps (PCP) are positive displacement pumps. The main working elements of PCP are eccentric screw and stator, they are suited for tough, nasty, multiphase fluids. In petroleum industry, PCPs are mostly used as boost devices and artificial lift devices. Its working performance is closely related to the operating conditions and structural parameters. Studing on the performance of PCP and optimization of its structure parameters have great significance on keeping PCP safe and efficient working. Based on Computational Fluid Dynamics (CFD) methods, analysis of the flow field and performance of PCP were studied. The main research works and conclusions are show as follows:(1) Make research of PCP flow field numerical simulations, structural parameters optimization, fault diagnosis and performance testing technology at home and abroad. Summarize the previous studies such as calculation model of flow field, structure optimization goal setting design of fault diagnosis and performance testing device, find out the defects in the researchs.(2) The 3D-transient numerical calculation model of PCP flow field was established, the fluid domain was extracted and the structural mesh was built, turbulence model is K-Epsilon, pressure velocity coupling method is Simple, numeric scheme is second order upwind, and the boundary conditions are import and export pressure. The dynamic mesh model is constructed, that the moving boundary is the surface of screw rotor, the motion mode is determined based on the rotor kinematics theory, three dimensional flow field transient analysis of PCP can be achieved.(3) The flow field Numerical simulations of PCP under different working conditions were completed, and the detailed information about the pressure, velocity fields and leakage position inside the PCP was obtained. The variation of leakage loss, displacement, rotor torque, power, volumetric efficiency and total efficiency with fluid viscosity, gas rate, speed and the pressure difference was studied. PCP operating conditions optimization methods were given.(4) Based on the optimal structure parameters of PCP, under the condition of invariable rotor diameter, the range of eccentricity and the stator lead wre defined. The detailed information about the pressure and velocity fields inside the PCP with different structure parameters was obtained, and the influence of eccentricity and stator lead parameters on the performance of the pump was analyzed. Optimization of PCP’s structure parameters was studied, the results shows that the better ratio range of eccentricity and rotor diameter is 0.125-0.2, the better ratio range of stator lead and rotor diameter is 3-4.(5) Four structural parameters of PCP improved schemes were given under the condition of small change in theoretical displacement. By comparing with the original PCP in flow and work performance, the best improved scheme was elected.(6) The fault diagnosis model of PCP was constructed, which based on three layer BP artificial neural network. Tan-Sigmoid was selected as the implicit layer transfer function, and Log-Sigmoid was used as the output layer transfer function. The Levenberg-Marquart algorithm was used to train the network model. The fault such as serious leakage, pump temperature is too high, rotor misalignment and stuck pump can be diagnosed by the model.(7) The fault diagnosis and performance testing device was designed, which have operating parameters of PCP monitoring, fault diagnosis, maintenance strategy making, online performance testing and other functions. The device is mainly composed of remote terminal equipmen and monitoring center, the data communication mode of the device is ZigBee/GPRS wireless network. Running parameters acquisition, operating mode switching, and operating condition regulation can be completed by the normal production monitoring station and performance testing statio which set in terminal equipmen. The control center is composed of fault diagnosis module and performance testing module. |
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