| With the large-scale and intensive development of livestock and poultry breeding in my country,the pollution of livestock and poultry waste has become more and more serious.Livestock and poultry manure can be biotransformed by black soldier fly and high-protein black soldier fly larvae and high-efficiency organic fertilizer can be obtained,which has become a research hotspot in the utilization of livestock manure resources.However,the mechanized operation equipment of targeted collection,transfer and transportation are seriously inadequate,poor working conditions,high labor intensity and low operating efficiency,which affects the biotransformation efficiency of black soldier fly and resource utilization,directly.Hence,to solve above problems,in combination with black soldier fly biotransformation pig process characteristics,taking the black soldier fly sand as the research object,and the feeding and conveying mechanism of black soldier fly sand was studied.Through theoretical research and experimental verification,it is of great practical significance to explore the operation performance of key mechanisms and improve the mechanization degree and resource utilization rate in the biotransformation of pig manure by black soldier fly.The main research contents and conclusions of this paper are as follows:（1）Parameter calibration of discrete element simulation model for pig manure organic fertilizer treated with Hermetia illucen,and flow properties of black soldier fly larvae biotransformation pig manure organic fertilizer with different moisture contents.To obtain the contact parameters of organic fertilizer accurately and quickly,this work combine the method of a cylindrical lifting physical test with discrete element method,and simulation parameters of organic fertilizer of Hermetia illucen treated with pig manure with moisture content of 43.6%was calibrated.The repose angle of organic fertilizer of Hermetia illucen treated with pig manure was taken as response value based on the Design Expert software8.0.6,and Plackett-Burman Design test was used to screen parameters.Then,significant influencing factors was determined by the steepest climbing test,Box-Behnken Design test was used to fit the test results using regression analysis,and the accumulation angle regression model was obtained.the regression model was optimized,and the optimal values of three significant factors were obtained:organic fertilizer of Hermetia illucen treated with pig manure poisson ratio was 0.11,organic fertilizer of Hermetia illucen treated with pig manure particle density was 1703 kg/m3,and the coefficient of rolling friction of organic fertilizer of Hermetia illucen treated with pig manure was 0.13.the simulation analysis was performed by the optimal parameter combination.The average repose angle was 38.61o,and the relative error between the repose angle and the experiment was 1.88%.which meant that the calibration parameters were accurate.In order to provide the quantized flow parameters of organic fertilizer for mechanization,in this study,black soldier fly biotransformation pig manure was used.The experiments were undertaken in condition of different moisture contents,changing from41.21%-60.52%.The results of experiment indicated that the internal friction angle between the organic fertilizer particles gradually decrease with the moisture content increases,the surface energy and the cohesion force were increased,which would restrict the flow movement of organic fertilizer to some extent.The study is expected to provide numerical parameter reference for the black soldier fly biotransformation pig manure organic fertilizer application and development of mechanization.（2）Parameter calibration of discrete element simulation model for black soldier fly,and measurement of restitution coefficient of black soldier fly in collision models based on the hertz contact theory.The“Hertz-Mindlin with JKR”contact model in the system was selected and the angle of repose was taken as the evaluation index to calibrate the parameters for the discrete element simulation model of the black soldier fly.It was found that not all discrete element model parameters of black soldier fly had significant impact on the angle of repose,only three parameters（shear modulus,static friction coefficient and rolling friction coefficient of the black soldier fly）that have significant influence on the accumulation of the black soldier fly were selected by Plackett-Burman design test.Then,the best range of three significant influencing factors was determined by the steepest climbing test,the other seven factors in this test were the intermediate values of the initial range,the accumulation angle of black soldier fly was taken as the response value,quadratic regression orthogonal rotation combination test was used to regression fit the test results,and the repose angle regression model was obtained.The regression model was optimized,and the optimal values of three significant factors were obtained:black soldier fly shear modulus was 8.67MPa,static friction coefficient was 0.43,black soldier rolling friction coefficient was 0.32.By using the optimal parameter combination for simulation analysis,the mean value of the accumulation angle was 35.84o,the physical test was 34.66o.the relative error between them was 3.40%.A restitution coefficient measuring device based on biological nature of black soldier fly larvae and kinematics was designed in this paper,and the restitution coefficient of black soldier fly larvae was measured and analyzed by experiment.Research on the collision materials,the thickness of collision materials,the falling height,the collision angle,the drop direction and the moisture content of black soldier fly larvae’s effect on the restitution coefficient of the‘the fifth age’black soldier fly larvae was conducted by a mixed orthogonal experiment based on the scheme of L16（44×23）.Then,single factor tests for factors including the collision materials,the thickness of collision materials,the falling height,the collision angle,the drop direction were carried out and the corresponding regression equations were obtained by analysis.Results of orthogonal experiments showed that the order of significance of restitution coefficient influencing factors was collision material>falling height>collision angle>drop direction>material thickness>moisture content.The influence of falling height and drop direction were the extremely significant（P<0.01）,and the influence of material thickness,material thickness and collision angle were significant（P<0.05）,and the moisture content was not significant.（3）Design and experiment on shoveling device of pig manure organic fertilizer by Hermetia illucen transforming based on bucket-wheel mechanism.A bucket-wheel shoveling device was designed,to improve the mean mass shoveled by hopper and reduce the coefficient of variation between each hopper,single-factor test was used to get the best form of the bucket-wheel mechanism.The Box-Behnken central composite experimental design principle was adopted on the basis of single factor experiment to research the working parameters of the shoveling device.The moving speed of bucket-wheel,rotation speed of hopper,and number of the hopper were taken as the influencing factors,the mean mass of organic fertilizer shoveled by the hopper and coefficient of variation were selected as the responsive variables.The results showed that the mean mass of organic fertilizer shoveled by the hopper and coefficient of variation could be fitted with two regression polynomials.According to the rate of factors contribution,the results indicated that the rotation speed of hopper had the greatest effect on the mean mass of organic fertilizer shoveled by the hopper and coefficient of variation among the three selected main factors followed by counterweight position,and moving speed of bucket-wheel had the minimum effect.Taking the maximum average mass of organic fertilizer shoveled by the hopper and the smallest coefficient of variation as the optimization goal,the optimal operating parameters of the machine was obtained:the moving speed of bucket-wheel was 65mm/s,the rotation speed of hopper was 8.25 r/min and number of the hopper was 3.At this time,the theoretical values of mean mass of organic fertilizer shoveled by the hopper and coefficient of variation were 4.008 kg and 3.19%,respectively.Based on the optimization result,the physical prototype was processed.The test results showed that the mean mass of organic fertilizer shoveled by the hopper and coefficient of variation were 4.236 kg and 3.37%,respectively.The relative errors between the experimental and predicted values of average mass of organic fertilizer shoveled by the hopper and coefficient of variation were 5.38%and 5.34%,respectively.The results indicated that the multivariate regression model was reliable.（4）Parameters Optimization of bucket feeding and conveying and bench test verification.Aiming to improve the load factor and reduce the residual rate of the Hermetia illucens L.feeding bucket.the single factor experiment was conducted to compare the effect of pig-manure bulking thickness on the biotransformation efficiency of Hermetia illucens L.The results demonstrated that when the thickness of pig manure was 0.10～0.15 m,the biotransformation efficiency of Hermetia illucens L.was relatively high.Meanwhile,a mechanics and kinematics analysis was conducted for the stress of the horizontal and vertical directions,the mass of materials in the bucket,and the leakage area of the bucket to reveal the mechanism of feeding filling conveying and leakage bucket.Additionally,the main factors influencing the bucket material feeding transport efficiency were comprehensively determined,including feed speed,bucket rotating speed,and feeding depth.The test indicators such as bucket load factor,variation coefficient,and residual rate were established.Besides,a three-factor three-level orthogonal combination experiment was conducted by combining with the Box-Behnken test method.Then,the regression mathematical model between the indexes and factors was set up to analyze the influence law of various factors on the evaluation indicators.The parameters were optimized with the regression model.Under the condition of the optimization parameters,the bench test equipment was established,and the experiment was performed.With the mixture of Hermetia illucens L.insect sand as the experimental material,its load factor,variation coefficient,sand retention rate,and larvae loss rate were 81.23%,1.48%,1.85%,and3.75%,the test results suggested that the bucket rotating speed was 6.5r/min and the feed speed was 45mm/s when the feeding depth was 15cm,the experimental values of the load factor,variation coefficient,and residual rate were consistent with the theoretical optimization values,with the relative errors of 1.39%,4.96%,and 6.32%,respectively.which met the experimental and actual production requirements.The research results provided a theoretical reference for the design and optimization of the bucket shape feeding conveying machinery of Hermetia illucens L.insect sand. |
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