Cavitation Effect And Fluid-Structure Coupling Analysis Of High Pressure Fluid Hybrid Mechanical Seal

Mechanical seals are widely used in aerospace,petrochemical,metallurgical power and other industrial fields because of their high reliability,good load-bearing performance and long life,etc.With the development of technology and consideration of the environment,the state has put forward higher requirements for industrial safety production,equipment efficiency,safety and leakage have become issues that must be considered.At present,mechanical equipment to large-scale and efficient development,sealing environment also changed,and gradually to high pressure,high temperature and other complex conditions,so the mechanical seal in a variety of complex operating conditions also maintain a smooth running state,and non-contact mechanical seal compared to contact mechanical seal,so that the seal end face to form a very thin layer of lubricating liquid film,reducing the friction between the scraping wear,to avoid seal failure.Under high pressure conditions,the phase state of the liquid film is unstable,and the higher the pressure the greater the leakage,the greater the deformation of the seal ring,and cavitation can effectively reduce leakage.Based on this,this paper proposes to open a hydrostatic step on the outer diameter side of the forward and reverse Rayleigh step-ring groove.The model combines the cavitation effect,the fluid dynamic pressure effect and the hydrostatic pressure effect,which can effectively reduce the leakage and the deformation of the seal ring.Firstly,a three-dimensional model of the liquid film is established,and the flow field of the mechanical seal liquid film is simulated based on the Mixture model and Zwart-Gerber-Belamri cavitation model using Fluent software for both forward and reverse Rayleigh step-annular groove and forward and reverse Rayleigh step-annular groove-hydrostatic step models,and the flow field cavitation is verified with classical literature to investigate the leakage rate,The variation law of cavitation area ratio and load carrying capacity under different pressure is investigated,and the seal mechanism is analysed in conjunction with the liquid film flow line distribution.The results show that the comprehensive performance of the forward and reverse Rayleigh stepannular groove-hydrostatic step is better than that of the forward and reverse Rayleigh step-annular groove.Next,the cavitation area ratio,gas phase volume fraction,leakage rate,bearing capacity and other performance parameters of the forward and reverse Rayleigh step-annular groove-hydrostatic step liquid film under different working conditions and structural parameters are analysed.The presence of the hydrostatic step increases its hydrostatic effect,which increases its loadbearing capacity and allows more fluid to flow into the seal chamber,causing it to cavitate at the reverse groove,increasing its cavitation area,reducing leakage,and changing from leakage to reflux as the speed increases.Finally,based on the cavitation effect,a unidirectional fluid-structure coupling analysis is carried out on the dynamic and static rings of the two models,and the stresses and deformations of the forward and reverse Rayleigh step-ring groove and forward and reverse Rayleigh step-ring groove-hydrostatic step seal rings are compared and analysed.The results show that the deformation of the forward and reverse Rayleigh step-ring groove-hydrostatic step seal ring is smaller,indicating that the existence of the hydrostatic step can reduce the deformation of the seal ring.The stresses and deformations of the forward and reverse Rayleigh step-ring groove-hydrostatic step seal ring with different working parameters are further explored.In this paper,the "hard-hard" mode was chosen for the friction sub-materials.The results show that the deformation and stresses increase with the increase of pressure and speed,and the maximum deformation and stresses appear at the root of the forward groove and the edge of the seal ring.As the modulus of elasticity of the material is larger,the stiffness of the material is larger and the elastic deformation of the material is smaller.