Thermal-Mechanical Coupled Model And Face Deformation Control Of The Contacting Mechanical Seals

Mechanical seals are widely used in the deep-ocean facilities.The thermal and mechanical deformation of the end faces vary with the depth of the water due to the complex thermal-mechanical coupled effect.The resulting large deformation would affect sealing performance and reduce its service life and even,it may harm the safety of operation staffs and passengers.Therefore,it is important to effectively predict the deformation of the contacting mechanical seals by means of the thermal-mechanical coupled analysis.Furthermore,it is helpful to explore the method to control the face deformation and promote the development and application of mechanical seals for deep-ocean facilities.Focusing on the mechanical seals for deep-ocean facilities,taking into consideration the coupling relationship of the thermal and mechanical deformation of the rotor and the stator,the fluid film pressure distribution and the viscosity-temperature characteristics of the fluid film,an axial symmetry theoretical model of the contacting mechanical seals was established.The sealing performance in steady state and the evolution law in the transient operation were investigated.The control method of the deformation was studied too.The main works and results are as follows:Taking into the coupling relationship between the thermal deformation,mechanical deformation,the temperature and thickness of the fluid film,the thermal-mechanical coupled model was established.The deformation of the end faces was analyzed and the influence of sealed pressure and rotation speed on the sealing performance were investigated.The transient thermal-mechanical coupled model during start-up was established.The variation laws of the end faces deformation and sealing gap during the start-up operation were analyzed.The mathematical model,used to analyze the influence of the wear of the end faces during the running-in period,was established based on the steady-state thermal-mechanical coupled model.The variation laws of the sealing gap,the end face profile,the thermal-mechanical deformation,the film thickness and the leakage were investigated.The influence of the geometrical sizes on the end face deformation was discussed on the basis of the thermal-mechanical coupled deformation of the end faces.The relationship between the axial length of the “support” and the mechanical deformation of the rotor was explored.A method used to realize the relative zero deformation of the rotor and stator was proposed through the control of the mechanical deformation of the rotor.Results show that the thermal and mechanical deformation appears to be approximately linear along the radial direction,not a completely linear.The taper type of the rotor finally appears to be a convergent gap by the impact of the mechanical deformation and thermal deformation,which form a divergent taper and a convergent taper respectively.The sealing gap transforms from a divergent gap to a convergent gap during the start-up operation.However,the sealing gap gradually transforms from a convergent gap to a parallel gap during the running-in period because of the face wear-out.With consideration of the thermal-mechanical deformation,the geometrical morphology of the rotor is determined by the geometrical morphology of the stator thermal-mechanical deformation.The approximately parallel sealing gap could be obtained under steady state by means of the optimation of the rotor geometrical size which could control the mechanical deformation of the rotor.The mathematical model and the results presented in the paper could be used to conduct malfunction analysis and to guide the design of the seal rings' geometry.