Design And Analysis Of Lifting Device Of Bucket Elevator Type Ship Unloader For Bulk Grain

In this thesis,a new type of bulk grain ship unloader with belt-type bucket elevator is taken as the research object,the lifting device of which will be designed and analyzed as well.The belt-type bucket elevator's bucket is using double rows,and it will be applied to ship unloader.According to the key technology of applying bucket elevator to ship unloader,the following research works are mainly carried out,and the conclusions are obtained:1.The structural layout of the new ship unloader is designed,which is divided into six parts: screw feeder,bucket elevator,belt conveyor,rotary/pitching mechanism,walkable gantry and discharger.Combined with the size of 7,6000 ton DWT panama-class bulk grain ship,the lifting height,pitching angle and other sizes of the ship unloader are ascertained.The double row bucket type bucket elevator is designed to meet the output requirement of ship unloader.And a new tensioning mechanism is designed to solve the problem caused by the traditional bucket elevator that the bottom bucket and the feeding device are dislocated due to excessive tension.2.Owing to the stacking angle and fluidity of the bulk grain,a three-screws feeding device was designed,which ensured that the bulk grain in the working range could be transported smoothly.Based on the empirical formula of screw conveyor's output,the theoretical formula of the output of an opening and moving screw conveyor is derived.Four factors including opening angle,moving speed,spiral diameter and spiral speed were selected,and four-factors and three-levels orthogonal tests were carried out with EDEM software to obtain the curve of the quality of the screw conveyor transporting bulk grains in each group.The result shows that the curve of mass changing with time approximates a straight line,which can satisfy the characteristics of uniform feeding of the bucket lifter,and the slope of the straight line indicates the output of the screw conveyor.At the same time,the theoretical formula of the output of the opening and the moving screw conveyor is verified.From the comparison of the theoretical results and the simulation results,the maximum,minimum and mean values of the absolute error of the two are 5.4809 kg/s,-0.3198 kg/s and 1.9006kg/s respectively.The absolute error of the output between 5~30 kg/s is 0.2377 kg/s,and the average error of the nine tests is 2.631%.Analyze the significance of four factors on the output of the screw conveyor by using Taguchi test.Through the SNR analysis,it is concluded that the moving speed,the spiral diameter and the spiral speed all contribute to the output of the screw conveyor.As the opening angle increases,the output of the screw conveyor tend to raise first and then fall.Simulation results and theoretical results are basically consistent.Through the analysis of the matching coefficient(?)with the output,the optimal combination of the screw's parameters matching the designed output is obtained: the screw's diameter is 200 mm,the screw's speed is 500 r/min,the moving speed is 0.1m/s,and the opening angle of the casing is 210°.3.For the cantilever state of the lifting device,the bending stiffness of the lifting section and the deflection equation when subjected to the wind load are calculated.The ANSYS software was used to analyze the stress and displacement of the bending deformation of the lifting device under wind load.The result shows that when the lifting device is subjected to the wind class of 6,7 and 8,the maximum deformation of the lifting section are 12.790 mm,14.7717 mm,17.303 mm accordingly.It can work normally under eight wind force and meet the requirements stipulated in safety management.According to the force distribution,the maximum stress occurs in the head connecting piece,which is 243.32 MPa,and the stress in the lifting section is small.Therefore,the original material Q235 of the head connecting piece is replaced with Q345.4.Create the cantilever beam mode1 of the lifting device,then establish the dynamic equation of the bending vibration of the lifting section by differential element method.Through the mechanical analysis of the end mass,the boundary condition of the bending vibration is determined,and the frequency equation of the bending vibration is deduced.Use MATLAB to solve the frequency equation,and the first four natural frequencies of the bending vibration of the 1ifting device are obtained.Using ANSYS,the moda1 simulation of the lifting device was performed to obtain the first four natural frequencies and formations.From the comparison between theoretical results and simulation results,the error values of the first four frequencies are below 5%,thus the theoretical results are reliable.The screw rotation frequency of the feeding device is analyzed to avoid resonance.The response of the lifting device under the excitation of the bottom wheel is analyzed,and the curve and function relationship between the total deformation and the deformation in X,Y and Z directions with time are obtained.It provides reference basis for the design of lifting device of ship unloader.