Research On Mechanical Seal Performance Of Stepped Convergent Groove Based On Cavitation Model

As a commonly used sealing device,mechanical seals are widely used in mining,petroleum,chemical,aerospace,nuclear power and other industrial fields.Non-contact mechanical seals have become the preferred shaft end seals for rotary fluid machinery due to their excellent performance.Wavy-Tilt-Dam(WTD for short)mechanical seal is a kind of non-contact mechanical seal.It has the advantages of low leakage rate and low wear.It has been widely used in the main pump shaft seal of nuclear power plants,but due to the sealing ring High hardness material requirements,complex surface requirements and high-precision machining requirements make precision machining difficult.Therefore,based on the lower leakage and higher hydrostatic pressure effect of the convergent groove,this paper proposes a The mechanical seal structure of the stepped convergent groove is derived from the mechanical seal structure of the end face,and the groove type presents a convergence gap in both the plane direction and the thickness direction.The 3D geometric model of the liquid film in the computational domain is established and structured mesh is divided.Considering the phenomenon of liquid film cavitation,numerical simulation of the lubricating liquid film in the seal gap was carried out by CFD,and the flow characteristics of the liquid film were analyzed through the liquid film pressure distribution.According to different working conditions and structural parameters,the parametric analysis of the liquid film cavitation effect was carried out.The membrane cavitation effect is mainly affected by the fluid viscous shear effect.As the membrane thickness increases,the liquid membrane cavitation effect weakens;as the rotational speed increases,the liquid membrane cavitation effect becomes stronger;as the sealing pressure increases,the liquid membrane cavitation effect becomes stronger.The membrane cavitation effect is weakened;as the groove depth increases,the liquid membrane cavitation effect weakens.The parametric analysis of the sealing performance was carried out,considering the cavitation effect of the liquid film,and the influence of working conditions and structural parameters on the sealing performance was studied.The results showed that with the increase of groove depth,groove number,groove opening and sealing pressure,Both the bearing capacity and leakage of the membrane increased;with the increase of the rotational speed,the bearing capacity increased and the leakage decreased;with the increase of the membrane thickness,the bearing capacity decreased and the leakage increased.Under the working conditions of small film thickness,high speed and low sealing pressure,liquid film cavitation is more likely to occur,and the fluid leakage is reduced;a smaller groove depth will enhance the fluid shearing effect,enhance the cavitation effect,and reduce leakage.The amount is reduced to achieve the purpose of reducing leakage.The fluid film temperature distribution was obtained by coupling the solution of the flow field and the temperature field,and the temperature variation law was studied.As the thickness increases,the maximum temperature of the liquid film gradually decreases;with the increase of the rotational speed,the maximum temperature of the liquid film increases;with the increase of the sealing pressure,the maximum temperature of the liquid film increases,but the effect of the sealing pressure on the temperature of the liquid film is very small,its working pressure should be determined mainly according to the sealing performance.