Study On The Structure And Performance Of The Upstream Pumping Mechanical Seal Under Variable Conditions

As a newly developed sealing technology in recent years,upstream pumping mechanical seal has low leakage and non-contact characteristics are widely used in medium sealing in the petrochemical industry.Practice has proved that they have achieved good results.However,in actual production,due to the change of the working environment and the phase change of the sealing medium,the mechanical seal deviates from the normal design and operation,the life span of the seal ring will be affected,and the seal may lose efficacy in severe cases.In response to these problems,this paper analyzes the reasons for the seal loses efficacy of pump equipment under variable working conditions,and combines mechanical seal mechanism and fluid film characteristics,and proposes a two-way connected groove suitable for variable working conditions.The fluid film model was established using Solid Works,and the fluid film was numerically simulated using Fluent.By changing the speed and pressure to study the sealing performance of the two-way connected groove,and optimize the structure parameters of the groove.The results show that: pumping through the dynamic pressure groove,the pressure reaches the maximum at the top of the moving ring groove.With the increase of speed and pressure,the opening force and leakage of the equipment show an increasing trend.When the speed exceeds 3000r/min and the pressure exceeds 0.5MPa,the leakage between the sealing end faces increases significantly.By comparing the sealing performance of spiral grooves and tree-shaped grooves,the leakage of two-way connected grooves is lower than that of spiral grooves and tree-shaped grooves under equipment low-speed and reverse working conditions,which verifies the feasibility.Through the optimization analysis of structural parameters,it can be concluded that when the groove depth is less than 6μm,the groove number is between 10-12,and the table width ratio is less than 0.4,the two-way connected groove mechanical seal has good sealing performance.In this paper,the thermodynamic performance of the sealing ring is analyzed by the thermo-fluid-solid coupling method,the thermo-mechanical coupling calculation equation and the heat conduction boundary conditions are established,and the fluid domain calculation results are imported to the surface of the dynamic and static sealing ring to solve the stress,strain and thermal deformation of the sealing ring,and obtain the thermodynamic performance change law of the sealing ring.The results show that under the action of fluid viscous shearing force,the maximum temperature of the sealing ring is located at the sealing dam,and the minimum temperature is located in the groove area.The temperature of the moving ring is higher than the static ring as a whole,and the rotation speed has a greater influence on the temperature of the sealing ring.Under the action of the heat-fluid-solid coupling force,the stress concentration area of the moving ring is located at the inner diameter and the sealing dam.The stress value of the moving ring is larger than the static ring stress value as a whole,and the stress value shows a gradual decrease trend along the axial direction.The rotation speed is the main factor that affects the stress and strain changes of the seal ring.During the operation of the mechanical seal,the end face of the seal is the main force-bearing part,and the force and deformation of the moving ring are greater than those of the static ring.Therefore,when selecting the friction pair material,an alloy material with good wear resistance and thermal conductivity should be selected as the moving ring.When the equipment is running,the outer diameter of the seal ring is deformed greatly,the graphite material with better self-lubricating property can be selected as the static ring to reduce the friction of the seal end face.