Design and optimization for smashed straw guide device of wheat clean area planter under full straw field

The rice-wheat alternate planting system is the main grain production model in most areas of China which has a great significance to ensure food security in China. The wheat sowing season after the rice harvest is relatively short, combined with the complexity of the traditional wheat planting process, which not only result in the higher sowing costs, but also fails to complete all works during the wheat sowing season.. Seeding directly in the field without straw treatment is an effective way to avoid the aforementioned problems. However, the following issues often occur during the application: for example, the soil-buried parts of the machine are blocked by grass which can't guarantee the steady operation; a large amount of straw is mixed into the soil which will take the seeds outside the soil and lead to the seeds exposed. To handle the above problems, this paper provided a new sowing method and an efficient guiding device, which adopted the planting technology in the full amount of straw and root stubble field. After the straw was pulverized, all the smashed straw could be placed on inter-rows by using the guiding device to form a sown strip containing few stalks, and the subsequent sowing operations could be completed on the strip. Through the theoretical analysis of the motion of the smashed straw, length of the diversion, radial distance and width of the diversion as key parameters affect the performance of the equipment were verified. The discrete element platform for simulating the operation of the device was established, and the platform mainly was composed of a pellet factory, a crushing device cover, a smashed straw guiding device and a soil trough. Based on the Box-Benhnken central composite test method and EDEM technique, the three-factor and three-level orthogonal rotating quadratic combination experiment was carried out with straw cleaned rate and variable coefficient of the strip width as the evaluation indexes. The influence of the three key parameters was analyzed. Furthermore, the regression equations were established to describe the relationships between the various factors and each assessment index by using the regression analysis and response surface analysis by software Design-Expert 8.0.6. The optimum combination of the selected parameters was obtained, and it was verified by numerical simulations and field trials. The experiment results indicated that various factors had a significant impact on straw cleaned rate and variable coefficient of the strip width. Depending on the order of significance of the impacts, the factors affecting straw cleaned rate were arranged as follows: width of the diversion, length of the diversion, radial distance. Likewise, the factors affecting variable coefficient of the strip width were arranged as follows: length of the diversion, radial distance and width of the diversion. The combination result of parameter optimum design was presented as follows: length of the diversion is 300 mm, radial distance is 19 mm and width of the diversion is 298 mm. The straw cleaned rate and the variable coefficient of the strip width were (91.83%, 10.36%) and (90.75%, 10.94%), which were determined through simulation experiment and field experiment respectively. Hence, the results of the two verification tests were basically consistent. The study should provide technical and equipment reference for no-tillage seeding of wheat after the rice harvest in the rice-wheat alternate season in China. © 2019, Editorial Department of the Transactions of the Chinese Society of Agricultural Engineering. All right reserved.