Design And Research On Straw Crushing Device Of Profile Modeling Residual Film Recovery Machine

China is a big cotton planting country,and Xinjiang is the largest cotton planting area in China,which is rich in cotton straw resources.At present,the common treatment methods of cotton straw are burning on the spot and mechanical crushing and returning to the field.The former has high cost,high labor intensity and low efficiency,which wastes high-quality agricultural resources,and will destroy the land ecosystem and pollute the atmosphere.At the same time,the cotton field in Xinjiang is planted with plastic film,but the recovery rate of plastic film in farmland is low,and the long-term residual plastic film will destroy the physical structure of soil and cause serious white pollution.As a result,the straw crushing-plastic film recovery combined machine,a compound agricultural machine,was produced,which can simultaneously deal with the problems of cotton straw and surface plastic film.Although the combined operation of straw crushing and plastic film recycling can effectively save labor cost and time cost,the crushing performance and scattering performance of the straw crushing device of the current machines and tools are not good,which not only affects the quality of straw crushing and returning to the field,but also improves the difficulty of plastic film recycling to some extent.Aiming at the above problems,aiming at improving the qualified rate of straw crushing length and reducing the falling rate of broken straw at work,a straw crushing device suitable for the follow-up residual film recycling machine was designed.The main contents include:(1)Investigate the working environment of straw crushing device on the spot.The planting mode of cotton field in Xinjiang was determined,and the average diameter of cotton stalks and the average mass of straws per unit area were measured,and the average hourly delivery of straws was calculated.(2)According to the technical requirements that the stubble height of straw crushing device is not higher than 80 mm,the crushing length is not greater than 200 mm,the qualified rate of crushing length is not less than 90 %,and the work needs lateral scattering,the overall scheme is determined.Based on the theoretical analysis of the existing arrangement scheme of the smashing knife and the knife shaft,it is determined that the Y-shaped smashing knife is used as the moving knife,and a more targeted arrangement mode of the smashing knife is designed,and at the same time,a "air knife" structure is designed to improve the air conveying effect of the straw smashing device.The rotation speed and radius of the cutter shaft,the shape of the fixed cutter,the working parameters of the screw conveyor and the design of the throwing parts are determined.(3)Using 3D CAD software to establish the simulation model of the crushing chamber of machines and tools,and using CFD software Fluent to explore the air flow characteristics and pressure distribution in the working state of the crushing chamber,it is verified that the feeding of straw is assisted by the negative pressure generated at the entrance of the crushing chamber,and the high falling rate of broken straw is affected by the turbulent vortex in the crushing chamber to some extent.The effects of different structures and working parameters of machines and tools on straw feeding,flowing and throwing are analyzed.The results show that the design of air knife can effectively improve the airflow velocity and straw fluidity in the crushing room under the structural mode of the device.Increasing the rotating speed of the grinding cutter shaft can increase the inlet negative pressure and improve the feeding and picking effect of straw,but reduce the fluidity of straw;Increasing the forward speed of the machine will reduce the feeding and picking performance of straw,but improve the throwing performance of broken straw.(4)According to the design value and performance requirements of the device,taking the rotating speed of the grinding cutter shaft,the advancing speed of the machine and the height of the cutter end off the ground as test factors,and taking the qualified rate of the crushing length of straw and the falling rate of broken stalks as test indicators,the field experiment of orthogonal combination of three factors and three levels regression was carried out,and the response surface analysis of the test results was used to get the optimal combination of working parameters,which was compared with other existing machines and tools.The research results show that the performance of the machine meets the requirements of national standards,and at the same time,it can ensure a low rate of broken straw falling,which provides a reference for designing the straw crushing device supporting the residual film recycling machine.