| As one of the indispensable device in the processing of gas exploitation, the high-pressure throttle plays an important role in safety production. In order to balance the differential pressure between the high pressure of the bottom of the well and the allowable pressure of the piping, a special device-the throttle valve (commonly known as the "choke") is often used on the oilfield for throttling and reducing pressure. It determines that the throttle should have a high-performance, high security, high efficiency and other characteristics. But in the process of gas exploitation, there will cause the vibration of spool valve and the erosion of cage apertures because of the high differential pressure, high velocity airflow turbulence disturbance and thus associated with varying degrees of high energy solid particles and other impurities. These are seriously restricting the gas production safety, affecting productivity, and increasing production costs. The structure of the cage throttle valve that this paper designed and studied is mainly made of the material for Carbide. Through the finite element analysis of continuous single-phase flow and solid-gas flow in the different structures, it studied its effect on the throttle inside turbulent flow, erosion rate and the throttle effect, etc. And then based on the results, improved and optimized the analysis of valve structure, to weaken the turbulent flow, reduce erosion rate of the purpose of improving the life of the valve body.This paper mainly carry out research work from the following aspects:(1) On the basis of the theory of fluid mechanics and advanced thermodynamics, applied Orifice restriction theory to establish a one-dimensional unsteady compressible flow equation in a single small orifice, discuss the relationship between pressure and the compressible fluid density, velocity and the cross-sectional area, analyze the effect of the relationship between the throttle differential pressure and orifice diameter, length and the aperture adiabatic throttling process and the energy loss process. Then design the layout of orifices and the structure of valve body.(2)Through the finite element analysis of continuous single-phase flow simulation in the different structures, it studied the effect of the throttle valve inside turbulent flow, pressure, velocity, density, Mach number, shock wave and finally throttling impact by the installation azimuth of cage orifice, valve opening, the number, the diameter and length of holes in the throttle valve.(3) Based on the results of continuous single-phase flow simulation and the flow characteristics of gas-particle, using Lagrangian discrete phase model and erosion model, it studied the influence rule of particle trajectory and erosion rate under different cage structure, acquired the severe erosion area of the spool.(4) In accordance with the velocity distribution and turbulent flow of continuous single-phase flow and the particle erosion wear of gas-solid flow, it improved and optimized the valve structure. Applying curve fitting technique to analyze the relationship between the rate of erosion and the structure of the spool. Then proposed the solution of 45° chamfering of the entrance of the orifice.(5) The design and application of two degrees throttle structure. Through the comparison of numerical results of the two kinds of base valve orifice structure, it proved that the smaller secondary base hole is better, and weaken the turbulence fluctuations of the valve chamber. It transformed the radial supersonic flow of the valve orifice into the axial supersonic flow of the hole in base, and transformed the local erosion wear of the valve orifice into the surface wear of base, which improved the safety of the use of valve performance and extended service life. |
PDF Full Text Request