| The objective was to improve the quality and effect of shell breaking on pecan after the first-time breaking.In order to make up for the shortage of the first shell breaking of pecan and ensure the more effective separation of shell and walnut kernel.After analyzing the properties of the pecan material and the various mechanical characteristics required for the secondary shell breaking,a secondary shell breaking method based on centrifugal force impact was proposed for pecan with unsatisfactory shell breaking effect,and a secondary shell breaking machine was developed.Solved the mistake of pecan in the process of secondary shell breaking due to different quality,Improve the effective shell breaking rate while reducing the nucleolar damage rate.It provides effective equipment support for the development of mechanization in the pecan processing industry.The main research contents of the thesis are as follows:(1)Review the equipment and production line information of walnut shells at home and abroad in recent years,and provide reference for the feasibility of this design.To define the pecans after the completion of a broken shell,and use the pecan mechanical test platform to determine the mechanical parameters required for the secondary shell breaking of the pecans at various levels.According to the measurement results,compare and analyze various shell breaking methods to determine The core shattering mechanism of the pecan secondary shelling machine is designed based on the centrifugal force and the impact type,and the overall three-dimensional model is established.(2)According to the trajectory of the pecan granules in the secondary shell-breaking machine,analyze the contact force,velocity and energy between the pecan and the structure,and calculate some core keys such as the centrifugal rotating device and the cone-shaped cylinder collision wall.Component geometry.Due to the difference in the secondary shelled pecan itself,it is impossible to obtain structural components of a specific size,such as the rotational speed of the centrifugal rotating device,the horizontal spacing of the edge of the centrifugal rotating device and the collision wall of the tapered cylinder,etc.,and the appropriate range of values is calculated.(3)Introducing the three-dimensional model of the secondary shell-breaking structure into the EDEM software for kinematics simulation,simulating the movement of the pecan granules into the secondary shell-breaking mechanism,and for the four factors that can only be used to obtain the appropriate range of values.Individual single factor simulation tests.According to the test results,while verifying the rationality of the previous literary design,the appropriate range of values of each influencing factor is narrowed,the number of subsequent orthogonal tests is reduced,and the test cost and time are saved.(4)According to the results of EDEM simulation analysis,select the horizontal parameters within the appropriate range of values,and design a four-factor and three-level hybrid orthogonal test.According to the analysis of the test results,determine the influence of each factor on the primary and secondary relationships,combined with actual needs.Determine the optimal combination of parameters and complete the trial production of the final prototype.The experiment of the sample machine showed that when the water content of pecan was 14.55%～16.35%,and the diameter was 18～22 mm(along the seam line direction),the speed of the centrifugal rotating device was 410 r/min,the distance between the edge of centrifugal rotating device and the collision wall of conical cylinder was 80 mm,and the feeding speed was 250 g/s,the effective rate of breakage was larger than 86.07%,the rate of damage to walnut kernel was less than 10.0%and the rate of production exceeded 540 kg/h。The accuracy and stability of each sample machine were verified,which met the actual requirements of the current pecan processing industry. |
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