Structural Strength And Stirring Flow Field Analysis Of Large Glutamate Fermenters

Fermenters are key equipment in the fermentation process.With the development of the relevant industries,more and more large fermenters are used.In this thesis,a large glutamate fermenter is studied,and the structural strength analysis,internal fluid analysis,agitator and fermentation liquid fluid-solid coupling analysis and agitator vibration analysis were carried out using finite element methods.The main works and results are as follows:(1)The finite element model of the large glutamate fermenter was established by applying ANSYS Workbench software,and the static analysis was carried out under the combined load conditions involving internal pressure,self-weight,equivalent receiver force and liquid column static pressure.The stress and deformation distribution on the large fermenter was calculated,and the location of the maximum stress intensity was found.Based on JB4732-1995 Steel Pressure Vessel-Design by Analysis,the stress classification method was applied and the structural strength safety assessment was conducted.(2)Fluent software was applied to simulate the gas-liquid two-phase flow in the large glutamate fermenter based on the multiple reference system method,and the fluid flow pattern,velocity field,oxygen distribution and stirring power in the large fermenter were calculated.The results showed that a stable circulating flow field was formed in the original design fermenter,and the overall oxygen distribution was relatively uniform,but the gas content rate was low on the upper side of the bottom paddle disc,near the upper paddle and at the bottom of the fermenter.(3)The local structure of the large glutamate fermenter was improved to address the problem of low local gas content,and the local gas content was effectively improved by opening holes in the bottom paddle disc,appropriately reducing the diameter of the upper paddle,and setting a baffle plate at a certain inclination angle at the bottom.(4)The unidirectional fluid-solid coupling analysis of the stirrer and fermentation liquid inside this fermenter was carried out,and the force,deformation and stress distribution of the stirrer under the steady-state flow field and the stress change during the rotation of the stirrer under the transient flow field were calculated.The results show that the force on the stirrer blade in the flow field is circumferentially symmetric,the force at the end of the stirrer blade is the largest and the deformation is the largest,and the stress is constantly fluctuating during the rotation of the stirrer.(5)The modal analysis of the stirrer was carried out under the restrained state,the pre-stressed state and the damped state of the stirring medium.The results show that the inherent frequency and vibration pattern of the structure before and after the application of pre-stress do not change significantly;the vibration pattern of the structure changes after considering the damping of the stirring medium,and the inherent frequency decreases significantly,which indicates that the damping of the stirring medium has an effect on the modal state,which implies the fluid damping needs to be considered when conducting vibration analysis of a structure subjected to significant fluid action.