Design And Experiment Study On Cleaning Unit Of Rape Combine Harvester

Rape is one of the most important oil crops in the world, both its planting area and output in China have been in the first place. Rape harvesting should be timely, efficient, high quality, low consumption, which not only is related to the high yield and bumper harvest of rape, but also directly affects the timely sowing and transplanting of next-stubble crops. Meanwhile, owing to the differences in maturity of rape and complexity of the harvest characteristics, the degree of rape mechanized harvesting has been low in China. The problems of long retting time, hard sledding and large harvest losses are becoming increasingly prominent. The cleaning unit is a main working part of combine harvester, improving the cleaning performance is one of the major technical problems that await to solve for rape combine harvester, it is also an effective way to improve operation quality of the whole machine.In order to solve the practical problems of existing rape combine harvester including complex structure, low clean rate and high entrained loss rate, a new type of air-and-screen cleaning unit combined with centrifugal air flow cleaning and rotary screening was developed, based on researching the properties of rape extractions, and analyzing the present research status of rape combine harvester, the working principles and types of cleaning unit systematically. The research contents of this paper are as follows:(1) Properties measurement of extraction components for rape combine harvester. The agronomic morphological parameters and suspension velocities of rape extraction components were measured. The results showed that suspension velocities of rapeseed and stems were observed to be closer, higher than suspension velocities of pod shells and light debris. The stems were relatively coarse and large, and rapeseed was relatively small. The differences in material properties of each component could be applied for determining reasonable forms of cleaning technology and suitable cleaning parameters, such as the air flow cleaning method was suggested to separated light debris and pod shells, and the airflow velocity was4m/s-6m/s.(2) Design of air-and-screen cleaning unit test-bed for rape extractions. A new type of air-and-screen cleaning unit combined with centrifugal air flow cleaning and rotary screening was developed, its working principle and working process were introduced.The overall structure and key components were designed, the main structure and operation parameters of core working parts, such as airflow cleaning cylinder and screen, were determined by theory analysis. (3) Cleaning performance experiments on cleaning unit test-bed. The relationship between cleaning performance and main factors with rotation speed of centrifugal fan, rotation speed of screen, screen surface type, rotation speed of screw conveyor was studied in the experiments. The results showed the influencing order for cleaning performance was rotation speed of screen, rotation speed of centrifugal fan, screen surface type, rotation speed of screw conveyor through the orthogonal test and comprehensive analysis method, and the optimum parameters were determined.(4) Parameters optimization of cleaning unit test-bed with response surface method. Parameters affected cleaning performance more significantly, such as rotation speed of centrifugal fan and rotation speed of screen were selected as independent variables, which would influence cleaning rate and loss rate of rapeseed. The mathematical model between the two factors and cleaning performance indicators, were established by using rotational quadratic regression design and response surface analysis. The optimized operational parameters were obtained as follows:rotation speed of centrifugal fan was1973.4r/min, rotation speed of screen was64.5r/min, then the cleaning rate of98.38%and loss rate of1.85%were obtained.(5) Design of cleaning unit and experiment on rape combine harvester in the field. A new type of rape combine harvester was designed and trial manufactured, based on the structure design, performance experiment and parameters optimization of header, thresh-separating unit and cleaning unit. Rape harvesting experiment on rape combine harvester was carried out in the field.