Mathematical Modeling Of The Rotary Valve Structure And Simulation Analysis On The Drilling Fluid Pressure Signals

The research on the information transmission from the underground to the ground is a hotspot in the field of drilling engineering.Measure while drilling(MWD)is a kind of modern drilling engineering supporting technology,of which drilling fluid pressure wave generator is the core device.In this paper,application fundamental researches on relevant theories was conducted,aiming to provide theoretical guidance and technical support for the engineering design of the drilling fluid continuous pressure wave generator.According to the non-steady flow water hammer theory of hydromechanics the mechanism of drilling fluid pressure waves are being analyzed and researched.A mathematical model of drilling fluid continuous pressure wave signals was built based on the analyses of fluid pressure inertia.The design criterion of the rotary valve is proposed by mathematical analyses,which can provide a certain construction of rotary valve.The characteristics of drilling fluid pressure signal generated by the valve port have been studied by CFD simulation.The research shows that the waveform of drilling fluid pressure signal is close to the sine wave,and the distortion is lower when the rotor rotates at constant speed.The variation of pressure signal amplitude with the drilling fluid flow rate,density,and the rotational speed of the rotor is consistent with the mathematical description of the fluid inertia pressure,showing that it can provides a theoretical guide for the engineering design of the structure of the rotary valve by combining mechanism modeling and mathematical analysis.Based on the theories of hydromechanics,theoretical analysis and CFD simulation are being used to valve the force of rotary rotor,showing that the torque of the rotary valve rotor is mainly composed of the rotating friction torque and the fluid drive torque,a mathematical model of rotating friction torque was built based on analyses of the axial force acting on the rotor by drilling fluid.By numerical calculation and simulation analysis,the rotating friction torque is nonlinear monotonic with the rotor rotation angle.Fluid drive torque changes periodically with the rotor rotation angle,and the density of drilling fluid and drilling fluid flow square were linear.It provides theoretical basis for the speed control of rotary valve by mathematical modeling and characteristics analysis of rotary valve rotor torque.