CHARACTERISTCS OF FLUID FILM IN OPTIMIZED SPIRAL GROOVE MECHANICAL SEAL

In order to investigate the sealing performance variation resulted from the thermal deformation of the end faces, the equations to calculate the fluid film pressure distribution, the bearing force and the leakage rate are derived, for the fluid film both in parallel gap and in wedgy gap. The geometrical parameters of the sealing members are optimized by means of heat transfer analysis and complex method. The analysis results indicate that the shallow spiral grooves can generate hydrodynamic pressure while the rotating ring rotates and the bearing force of the fluid film in spiral groove end faces is much larger than that in the flat end faces. The deformation increases the bearing force of the fluid film in flat end faces, but it decreases the hydrodynamic pressure of the fluid film in spiral groove end faces. The gap dimensions which determine the characteristics of the fluid film is obtained by coupling analysis of the frictional heat and the thermal deformation in consideration of the equilibrium condition of the bearing force and the closing force. For different gap dimensions, the relation- ship between the closing force and the leakage rate is also investigated, based on which the leakage rate can be controlled by adjusting the closing force.

3D TRANSIENT COUPLED THERMOELASTIC-PLASTIC CONTACT SEALING ANALYSIS OF REACTOR PRESSURE VESSEL

Sealing analysis of sealing system in reactor pressure vessels is relevant with multiple nonlinear coupled-field effects, so even large-scale commercial finite element software cannot finish the complicated analysis. A finite element method of 3D transient coupled thermo-elastic-plastic contact sealing analysis for reactor pressure vessels is presented, in which the surface nonlinearity, material nonlinearity, transient heat transfer nonlinearity and multiple coupled effect are taken into account and the sealing equation is coupling solved in iterative procedure. At the same time, a computational analysis program is developed, which is applied in the sealing analysis of experimental reactor pressure vessel, and the numerical results are in good coincidence with the experimental resuits. This program is also successful in analyzing the practical problem in engineering.

Transient Simulation on Dynamic Response of Liquid Annular Seals

Transient change of the operating parameters has a serious influence on the stability of liquid annular seals.Take the liquid annular seals as a research object,a numerical method based on six-degree-of-freedom(6DOF)to analyze the dynamic response of liquid annular seals under gravity impact load.The variations of the force of liquid seal and pressure as well as the axis trajectory in time history are investigated.The influence of different sealing clearance,different liquid viscosity and different rotor speed is also studied.The results show that the maximum sealing pressure and sealing force of gravity direction will increase greatly in a very short time and then reduce rapidly.When sealing clearance increases,the displacement response amplitudes of axis trajectory,the maximum sealing force of gravity direction and maximum sealing pressure also increase.When liquid viscosity increases,the displacement response amplitudes of axis trajectory,the maximum sealing force of gravity direction and maximum sealing pressure decrease.We also found that different rotor speed has almost no influence on the maximum sealing force of gravity direction and maximum sealing pressure.

Three-dimensional numerical solution and stress cage analysis of high conductive fractures pressure sealing

Aiming at the main problems in the design and analysis of well wall strengthening for fractured formations,a three-dimensional(3D)numerical simulation scheme is proposed.The three-dimensional finite element software is used to analyze the mechanical behavior of fractures and the pressure sealing process,and evaluate the stress cage effect.The main features of the model are as follows:(1)The equivalent fractures in the analytical model represent the function sum of the mechanical behavior of all fractures on the well wall,which is a functionally equivalent crack.(2)When evaluating the stress cage effect,the shape of the crack wedge filled with the plugging agent particles is formed by simulating the fractures opening process under the injection pressure,not a given regular shape.(3)In the model of calculating bull heading of block agent,the liquid pressure on the well wall is the injection pressure,which is a variation increased with time.The fluid pressure on the well wall in the stress cage calculation model is generated by the initial pore pressure.(4)The numerical evaluation of the stress cage effect is achieved by calculating the increase amplitude FX of the minimum hoop stress on the well wall.Using this model,several sets of injection pressure design values can be used for pressure plugging numerical simulation and stress cage effect evaluation calculation,and then the optimal and accurate quantitative value of“injection pressure,block agent particle size,safe mud window upper bound”are found through comparison.Finally,through an engineering example of horizontal well drilling pressure sealing in a shale gas reservoir developed by a fracture,we use the above theoretical tools to introduce the process and results of the numerical analysis of the extended mud window drilled in the shale gas fissure reservoir.