| Since 1990 s,the swine industry in China has developed rapidly,and it has become one of the pillar industries of agriculture.Over the years,China is the world's largest pork consumer.However,China is not a strong country in swine feeding,and more than 60% of small and medium-sized swine farms lack necessary equipment.With the development of large-scale swine breeding and the automation and intellectualization of swine feeding process,it is necessar y to carry out in-depth research on breeding machinery.Feeding operation is a heavy work in swine farms,mechanization is the key to its large-scale development,the feeder is the necessary terminal equipment for swine feeding,it is a important equipment in feeding operation,and its discharging performance seriously affects the feeding quality of swine,therefore,the research on feeders for swine is extremely important and needs to be deepened.Aiming at the problems of easy arch formation and metering error of discharge rate in the operation of the intelligent feeding equipment used in the important stages of conservation,pregnancy and lactation,there is no theoretical innovation and mechanism research of the unloading paddle and the screw accurate feeding device.According to the analysis of the development status of swine feeding device at home and abroad,in this paper,the pellets are selected as the research materials.The unloading paddle feeding device and the screw feeding device are respectively studied by the theoretical analysis,virtual simulation,high speed camera and test measurements,and the mechanism of the unloading paddle and screw feeding device developed is deeply studied,the flow characteristics of pellets in the hopper and discharging performance is investigated.The main contents are as follows:(1)Material properties measurement pelletsThe pellets used for swine were selected as research materials,then the test bench for measuring friction and mechanical properties was designed and built,the physical characteristic parameter and the mechanical characteristic parameter were obtained through a series of basic test methods.The physical characteristic parameters mentioned above include geometry,density and bulk density of pellets,and the mechanical characteristic parameters mentioned above include static friction coefficient,rolling friction coefficient,repose angle,internal friction angle,shear modulus and restitution coefficient between pellets and various materials.On this basis,contrast verification test of repose angle was conducted through virtual calibration method to verify the accuracy and reliability material characteristic parameter.This section could provide an important reference for the subsequent optimization design of key structure and virtual discharging test.(2)Modeling and analysis of accurate feeding device for swine feederIn this section,the overall structure and working principle of the feeding device were expounded respectively.In addition,the unloading paddle feeding device and the screw feeding device were initially designed for the stage of nursery and sows.Then the kinematics and dynamics models in the discharging was established,and the discharging mechanism of feeding ope ration was analyzed.Meanwhile,the key structure such as the storage device for pellets(hopper and rectangular hopper)and the unloading unit was optimized respectively,so as to effectively improve the operation quality of the feeding device for swine.This section could provide a theoretical basis and important reference for numerical simulation of discharging process and performance experiment.(3)Numerical simulation and analysis on discharging performance and flow characteristics of pellets in the hopper of the unloading paddle feeding deviceIn this section,the discrete element method simulation software EDEM was used to carry out virtual discharging test of feeding device in combination with numerical simulation technology and single factor test method,and the unloading paddle feeding device used for nursery was selected as the research carrier.At the same time,flow mechanism of pellets in the hopper with unloading paddle was explored and investigated,moreover,the influence of the hopper half angle,outlet diameter and shaft rotation speed on the flow characteristics of pellets in the hopper during discharging was analyzed,and the various law of discharging performance of feeding device under the different combinations of parameters was discussed,which can determine the reasonable range of above parameters affecting the working performance of the feeding device,and complete the processing of physical prototype of the feeding device,then the high speed camera technology was used to track the pellets trajectory in order to verify the correctness of the simulation analysis and optimize the reasonable influence range of the above parameters.This section could provide important reference for the subsequent discharging performance experiment,so a s to obtain the best combination of parameters(4)Numerical simulation and analysis on discharging performance and flow characteristics of pellets in the rectangular hopper of the screw feeding deviceIn this section,the screw feeding device used for sow was selected as the research carrier,mechanism analysis on flow process of pellets in the screw casing was carried out in order to verify the correctness of the previous theory analysis.Furthermore,the hopper half angle,screw blade diameter and screw shaft rotation speed was selected as the test factors,the relative standard deviation(RSD)and the relative deviation between the set point and the theoretical value were used as criteria,and single factor virtual simulation test was carrie d out by the above factors and indicators.Meanwhile,the influence law of different factors on the flow characteristics of pellets and discharging performance index was obtained respectively by using the data derived from the post-processing module of EDEM software,then,the experimental prototype of feeding device was completed.With the help of high speed camera technology,the movement behaviour of pellets during discharging was analyzed,and reasonable influence range of the above parameters was optimized.(5)Performance experiment and parameter optimization of the unloading paddle feeding deviceIn this section,the unloading paddle feeding device used for nursery was selected as the research carrier,the performance experiment was carried out through the self-built test bench designed for discharging performance experiment.In addition,the hopper half angle,outlet diameter and shaft rotation speed were selected as the experimental factors,the mass flow rate and variation coefficient were selected as the evaluation indexes,the discharging performance optimization experiment was carried out based on the single factor and multiple factors methods.At the same time,multi-objective optimization of mass flow rate and coefficient of variation was carried out based on the Design-Expert8.0.10 software.Moreover,when the hopper half angle,outlet diameter and shaft rotation speed was 70°,110 mm and 30r/min respectively,the coefficient of variation and mass flow rate is 3.64% and 152.98g/s respectively,and the optimal combination of the above parameters was used for the verification experiment.The results showed that the pellets were evenly transported to the feeding trough layer by layer by the unloading paddle,and the highly efficiency was realized,at this moment,the relative error of the coefficient of variation and the relative error of the mass flow rate were 3.12% and 4.14% respectively,which is beneficial to evenly discharg e for pellets and verified the rationality of the parameters design of the unloading paddle feeding device.(6)Performance experiment and parameter optimization of the screw feeding deviceIn this section,the screw feeding device used for sow was selected as the research carrier,the performance experiment was carried out through the self-built test bench designed for discharging performance experiment.In addition,the hopper half angle,screw blade diameter and screw shaft rotation speed were selected as the experimental factors,the relative error and variation coefficient were selected as the evaluation indexes,the discharging performance optimization experiment was carried out based on the single factor and multiple factors methods.At the same time,mul tiobjective optimization of relative error and coefficient of variation was carried out based on the Design-Expert8.0.10 software.Moreover,when the hopper half angle,screw blade diameter and screw shaft rotation speed was 55°,48 mm and 60r/min respectively,pellets in the rectangular hopper were evenly transported to the feeding trough during discharging process,and the mass flow rate per unit time through the screw casing was little different from the theoretical value,the coefficient of variation and relative error was 2.62% and 5.1% respectively,then the optimal combination of the above parameters was used for the verification experiment.The results showed that the screw feeding device has high discharging stability and accuracy.At this moment,t he error of the coefficient of variation and the error of the relative error were 3.60% and 2.24%respectively,which verified the rationality of the optimization design parameters of the screw feeding device. |
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