| Rice and wheat are China’s two main food crops,and their traditional harvesting methods rely mainly on human labor,which is inefficient and susceptible to weather.Therefore,the rice and wheat harvest system can greatly improve the harvest and harvest yield,which is an important factor in boosting China’s food quality.Through theoretical calculation and analysis,computer-aided design combined with the latest computer simulation technology,it is proposed to design a threshing and sorting device with a feeding capacity of 4kg/s,which can meet the agronomic requirements of rice and wheat crops in southern China.To this end,on the basis of integrating the technical characteristics of the existing rice-wheat combine harvester and the adaptability to the environment,the key structure of the key structure is innovatively designed.The main work and innovations are as follows:(1)Design and simulation analysis of threshing separation device.In addition to the required national standard combine harvester,threshing sorting device design scheme and the spatial layout of the threshing sorting device were formulated,and the power transmission route was determined based on its working principle.By nx12.0 software 3D modeling of the main components of the threshing separation unit,including threshing drum,threshing elements,concave sifies and top covers.Considering the correlation between the strong stiffness and dynamic performance of the threshing drum and the use effect of the threshing separation device,the static and modal analysis of the threshing drum shows that the maximum stress of the threshing drum reaches 16.948 MPa,which has a good strength reserve,and its first-order inherent mode is 38.683 Hz,which can avoid damage caused by resonance.(2)Design of sorting device.According to the distribution law of the extraction,the design scheme of the cleaning device is determined as a combination structure of double duct four-blade centrifugal fan +reciprocating vibrating screen,the overall structure of the designed vibrating screen can be simplified into a common crank slider mechanism model,the vibrating screen is designed into two layers,the upper layer is composed of corrugated plate,shutter sieve and tail screen,and the opening degree of the shutter sieve screen can be adjusted with the amount of detachment to improve the cleaning efficiency.Meanwhile,the auger structure and the amount of nutrient crops are matched to ensure the push efficiency of the grain during the threshing sorting device.(3)Rack optimization design.Under the constraint of ensuring the dynamic characteristics of the threshing sorting device frame,a multiobjective optimization method based on response surface is proposed to realize the lightweight of the threshing sorting device frame.The 1～6 order mode of the threshing sorting unit frame of the natural frequency range is optimized to be 17.84～53.42 Hz,and the mass is 179.01 kg,duo to the firstorder natural frequency is near the external other frequency,so the natural frequency of the threshing sorting unit frame should be adjusted.The multi-objective optimization method based on the response surface will be selected to optimize the design of threshing sorting unit frame structure to reduce the mass of the threshing sorting unit frame.The established multiobjective optimization mathematical model uses the sensitivity analysis method to screen out the thickness of the beam structure with strong correlation to the optimization target as the design variable,and takes the modal results of the 1st,2nd and 6th orders and the thickness range of each supporting beam as the constraint conditions.On the basis of increasing the natural frequency of structure of the threshing sorting unit frame to achieve the purpose of minimizing the weight of the frame.The optimizing consequence show that the proposed method can take into account its good dynamic characteristics and the achievement of lightweight goals.(4)Orthogonal experimental design.For the shutter screen opening,fan deflector angle and fan speed in the cleaning device.According to the design requirements of the orthogonal design table to direct the simulation experiment of the Fluent software.The analysis results showed that the shutter screen opening had the greatest influence on the change of air velocity above the cleaning room,and the centrifugal fan speed had the least impact.When the optimal level parameters of the three factors are found,the optimal level parameters are 30 mm,the angle of the deflector is0°(horizontal),and the fan speed is 1700r/min,and the airflow distribution in the cleaning room A and B is the most in line with the cleaning of crops.(5)Field experiments show that the total grain loss rate of the designed crawler full-fed grain combine harvester is only 0.6%,while the impurity content and crushing rate are 0.8% and 0.7%,respectively,and the experimental index parameters meet the specification requirements of rice-wheat combined harvesting machinery and are better than the industry average. |
