Design and experiment on cylinder sieve with different rotational speed in cleaning system for rape combine harvesters

Abstract: Combine harvesters and windrowers were conventional machines for rape harvesting. Rape combine harvesters could simultaneously complete cutting, threshing, separation and cleaning at high production efficiencies. Cleaning systems played an important role in rape combine harvesters. The conventional rape combine harvesters were modified based on grain combine harvesters. The majority of cleaning system of combine harvesters was vibrating screen working with fan. Some changes like increasing the depth of header, adjusting reel position and transmission ratio, increasing active divider and so on were made to adapt to the rape plant in the field and there were still some problems like blocking of screen and the structure remained to be optimized. In conclusion, there were some problems like excessive vibration and relatively complicated structures due to vibration sieves in traditional combine harvesters. Cyclone separation was based on the principle of airflow cleaning. It was widely applied to grain processing, industrial dust removal and other fields. It could be used in rape combine harvesters taking the advantages of simple structures. However, short stems and pods made it hard for cyclone separation cleaning system to make the seeds clean. Adding a cylinder sieve was a solution to reduce the burden of cyclone separation cleaning system. The main limitation of the development of cylinder sieve was its relatively low efficiency. To reduce the burden of cyclone separation cleaning system and improve the efficiency of preliminary screening, a kind of cylinder sieve with promoting device in different rotational speed for rape combine harvesters based on EDEM was designed and relative experiments were carried out. As the primary process to separate the stems for the cleaning system, the cylinder sieve with promoting device in different rotational speed was mainly consist of the cylinder sieve, promoting device, the cover shell and the transmission device. The sieve was bent and shaped based on annular plane screen. The promoting device was mounted inside the cylinder sieve. Both of them were rotating around the same center axis. The hydraulic motor to provide power to the promoting device and to the cylinder sieve though the transition gear on transmission shaft. The rotation direction of cylinder sieve was changed by the gear transmission to realize the different rotational speed and direction of cylinder sieve and promoting device. Analysis and calculation of the rotational speed range of promoting device and cylinder sieve were carried out. Orthogonal experiments based on EDEM was obtained. The loss ratio and cleaning ratio of cylinder sieve was taken as the indexes while the rotational speed of sieve and the rotational speed and tooth number of promoting device were the factors. The optimal parameter combination was obtained. Test-bed and field experiments were carried out to verify the results of simulation. The simulation results show that the optimum combination of the parameters was 35 r/min and 80 r/min of rotational speed of sieve and promoting device respectively and 6 of the saw teeth in the projection plane of the promoting device. In addition, the loss ratio and cleaning ratio of cyclone separation cleaning system working with the cylinder sieve were 4.83% and 85.7% respectively while the rotational speed of the fan could be reduced by 36.9% under the condition of best combination of parameters. Field experiments were carried out in the experimental field of Huazhong Agricultural University in May 2017. The materials of experiments were rape planted by direct rapeseed planter. The average planting density was 40 plants/m2, and the water content of rapeseed, stems and pod shells were 23.47%, 20.9% and 33.98%, respectively. The working speed of 4LYZ-1.8 type rape combine harvester was 2.9-3.6 km/h and the working efficiency was 0.52-0.65 hm2/h. The average loss rate of rapeseed was 5.9% and the average cleaning rate of rapeseed was 84.4%. The average power consumption of the cleaning system was 3.48 kW. This research provided a reference for the improvement and optimization of cleaning system for rape combined harvesters.