Fluid Structure Coupling And Fatigue Analysis Of Metal Bellows

Mechanical seal,also known as end face seal,plays the role of axial end face seal by preloading elastic elements and compensating the end face seal pair.Mechanical seal can effectively reduce the internal leakage,external leakage and leakage of the machine;reduce friction loss;improve the reliability of the machine and save raw materials,safety and environmental protection,so it is widely used in rotating machinery such as pump valve,reaction kettle,centrifuge,etc.In the petrochemical industry,the use of mechanical seal is developing to high temperature,high speed,high pressure,large diameter and other high parameter working condition media.As an elastic element in mechanical seal device,bellows should overcome the inertia of auxiliary seal,friction of transmission parts and moving ring,so as to ensure good sealing performance.In order to ensure the normal and safe operation of the equipment,it is necessary to study the bellows.Taking S-type metal welded bellows as the research object,aiming at the problem of bellows fatigue failure caused by resonance frequency and radial vibration of rotating bellows under fluid structure coupling,the flow field models of bellows and seal cavity are established respectively,and the radial displacement signals of bellows rotation are collected.The K-ε turbulence model and discrete DPM model are used to simulate and analyze the solid-liquid mixed flow field;the dynamic modal equilibrium equation and vibration fatigue analysis are carried out for bellows;the frequency domain quadratic differential and short-time Fourier transform are used to edit the radial vibration displacement signal.Through the analysis of the flow field,the pressure field distribution of the medium in the sealing cavity to the wall of the sealing cavity and the outer surface of the bellows is obtained;the erosion rate distribution of the solid particles to the inner wall of the sealing cavity and the outer surface of the bellows under different working conditions;the movement track of the solid particles in the flow field and the change of the escape amount and movement state of the solid particles in the flow field before and after the mechanical seal.The internal pressure of the flow field is applied to the outer surface of the bellows,and the natural frequency and equivalent effect change of the bellows under the action of pre-stressed and flow field are analyzed.It is shown that the mode of the bellows changes obviously under the action of the external flow field,and the pre-stressed hardly changes the fixed frequency of the bellows;when the flow field pressure is constant,the speed and pre-stressed increase,and the effect of the bellows decreases;With the increase of inlet pressure,the maximum equivalent strain and stress of bellows increase.Processing the radial displacement vibration signal,loading the edit signal and the original signal to the radial direction of the bellows respectively,obtaining the damage effect of the edit signal and the original signal on the fatigue damage of the bellows;the damage distribution cloud chart;the number of stress cycles in different ranges under different rotating speeds of the bellows,the results show that the edit signal obtained by the short-time Fourier transform effectively retains the With the increase of rotating speed,the number of large radial stress cycles on the bellows decreases.