Study On Design And Damage Law Of Sweet Potato Combine Harvester

Sweet potato can be used as food crops,breeding feed,industrial raw materials and so on.It is one of the important economic income in economically backward areas.At present,the technology level of sweet potato harvester in China is relatively backward,and it is in urgent need of technological innovation.In the process of sweet potato harvesting,it is inevitable that mechanical damage will occur due to friction,collision and extrusion,which will affect the appearance quality of sweet potato.At the same time,it is easy to be infected with pathogens and not easy to store,which will cause economic losses to farmers,especially in the self-propelled sweet potato combine harvester,because of its complex structure,the damage is particularly serious.Therefore,under the condition of ensuring the efficiency and quality of mechanized harvest of sweet potato,reducing the mechanical damage of sweet potato is also an urgent problem to be solved.In order to solve the above problems,a two-stage potato soil transportation and separation device was designed in this paper.By combining theoretical analysis,simulation and bench test,the collision rules of sweet potato tubers under different parameters were studied,and the structure and working parameters of the device were optimized to reduce the harvest damage of sweet potato.The main contents are as follows:(1)Combined with the development status of sweet potato combine harvester at home and abroad,the structure design scheme of conveying device is determined as two-stage conveying separation device.It includes the configuration form of bar and shift lever,conveying performance and selection of shaker,and analyzes the force of shaker.(2)The basic physical parameters and mechanical properties of sweet potato were studied.The results showed that about 48%of the short axis size of sweet potato was concentrated in 60～70mm,and about 52%of the long axis size was concentrated in 130～150mm.The moisture content of sweet potato tuber was 79.17%,and there was no linear correlation between the moisture content at maturity and growth time.The tuber density,elastic modulus,Poisson’s ratio,shear modulus,static friction coefficient,dynamic friction coefficient and impact recovery coefficient of sweet potato steel plate were measured.The average critical load and yield stress of sweet potato skin puncture were 75.15n and 1.313mpa,respectively.Soil water content,particle size distribution and density were measured.(3)The movement separation process of sweet potato soil mixture was simulated by edem software,and the key parameter surface energy of soil particle JKR contact model was determined to be 7J/m~2.Through the movement analysis and collision theory analysis of sweet potato tuber in the transportation process,it was determined that the main influencing factors of mechanical damage of sweet potato in the transportation separation process were transportation speed,amplitude,frequency,inclination and drop Height difference.(4)Through the discrete element simulation test,taking the maximum stress and collision times of sweet potato tuber as the evaluation index,the collision law of sweet potato under different potato soil ratio,the influence law of different potato soil ratio and transportation speed on sweet potato collision,and the influence law of different potato soil ratio and vibration amplitude on sweet potato collision were studied.The higher the proportion of sweet potato to soil,the faster the conveying speed,the greater the amplitude,and the more serious the sweet potato collision.(5)Through the discrete element simulation test,taking the soil loss rate,the maximum force of sweet potato and the number of collisions as the evaluation indexes,the effects of different conveying speeds and different lifting chain angles on the change of potato soil ratio,the effects of different amplitudes and frequencies on the potato soil ratio and the collision rules of sweet potato were studied respectively;the collision process of sweet potato and rod was simulated by ANSYS display dynamics,and the results were obtained When the impact velocity is 2.21m/s,the impact stress reaches 1.3953mpa,which has reached the critical stress of impact damage.(6)In this paper,a two-stage conveying device for sweet potato impact damage test-bed was designed.Three factors and three levels of central composite test method were adopted.Taking conveying speed,amplitude and frequency as test factors,and the rate of damaged potato and separation efficiency as evaluation indexes,orthogonal test was carried out.The optimal combination of parameters was obtained as follows:conveying speed was 0.55m/s,amplitude was 18.2mm,and frequency was 6.1hz The separation efficiency was 96.28%.