Study On Vibration Characteristics Of Flexible-Blade Rushton Impeller

Stirred reactors were widely used in industries such as biology,pharmaceuticals and petroleum.The vibration of the mixing equipment affected the working performance of the parts,increased the mixing power consumption,and reduced the mixing efficiency.If resonance occured,the working life of the equipment was shortened,and safety accidents might occur in serious cases.Therefore,the vibration characteristics of the flexible-blade Rushton impeller developed by the research group in the early stage were studied.A combination of numerical simulation and experimental measurement was used to study the vibration characteristics of the propeller shaft system,and further analyze the influence of the rotational speed and the stirring medium on the vibration characteristics.The CFD numerical simulation method was used to analyze the flow field characteristics of the mixing system,and the fluid-structure interaction method was used to analyze the force characteristics of the propeller shaft system.The results shown that the maximum pressure appeared at the tail end of the stirring blade's front,and the maximum speed appeared around the blade.The maximum stress of the propeller shaft system was located at the connection between the flexible blade and the rigid blade,and the maximum deformation was located at the tail end of the flexible blade.The connection was the most likely part of the propeller shaft system to fail.The safety factor decreased as the rotational speed or viscosity of the stirring medium increased.Use numerical simulation method to analyze the vibration characteristics of the propeller shaft system,and mainly solve the natural frequency and vibration mode of each order without prestress and with prestress.The results shown that the prestress reduced the natural frequency of each order,but the reduction ratios were all below 3%.The number of deformed blades decreased,and the amount of blade deformation increased to varying degrees under prestress.In order to avoid a large response from the propeller shaft system,206 Hz and 255 Hz should be avoided.The critical rotational speed of the stirring shaft was calculated to be 1452.6 r·min-1.The vibration characteristics of the propeller shaft system was studied by experimental measurement,and use BK vibration tester and DH mini-tester to measure the vibration characteristics of static and rotational state respectively.The results shown that the damping ratio is 5.11%in the static state,and the damping ratio was 7.07%in the rotational state.Compared with the experiment,the 1st?12th order natural frequencies of the unprestressed modal analysis and the prestressed modal analysis all increased,and the increase ratios were all below 6%.The method of prestressed modal analysis was used to study the influence of different rotational speeds or stirring media on vibration characteristics.The 1st?12th order natural frequencies all decreased with the increase of the rotational speed.And with the viscosity of the stirring medium increasing,The 1st?12th order natural frequencies all increased.The influence of high rotational speed on the natural frequency of each order was greater than that of low rotational speed,and the influence of rotational speed or the viscosity of the stirring medium on the low-order natural frequencies was greater than that of the high-order as a whole.