Research On The Longitude Axial Flow Threshing And Separating Unit Of Rape Combine Harvester

As the main oil crop, rape has the largest plant area in China. Aiming to the problems of the rape combine harvesting technique development with complicated structure and worse performance, especially great loss ratio and low purity, a new threshing and separating system was designed by combining the functions of cutting, conveying and threshing on the traditional header. The integrated roller was designed by virtual prototype technology, and the testing device was manufactured to do the experiment; the dynamic model of conveying on rape was established to analyze on MATLAB software for researching the rape conveying mechanization; The force issue and motion law of rape in threshing cavity were analyzed by discrete element method to reveal the rape threshing mechanization; The threshing effect of the integrated roller were conducted on bench test. So the main researches of my subject listed as below:(1) The basic mechanical characteristic experiments for the rape stalk and capsule were introduced on the sheared and compressed characteristic, the results showed that shear force and compressing force of rape stalk were not significant changing with the time, while the shear force of rape stalk near the harvesting time was not the maximum value in the experiment, so the power consumption of cutting should not be considered as the influence factor on the harvesting time; The compressing force of capsules was related with the time. With the promotion of maturity, the moisture content of capsule decreased, the biomass structure of capsule easily became to deform and crack, and it was beneficial to thresh.(2) The effects on different threshing methods for rape capsule with rubbing, rolling and impact were conducted. The results showed that the threshing rate had a logarithm relation with the power consumption. When the power consumption of threshing was very low, the threshing rate would greatly increase with the power consumption increasing, and then reach the maximum; meanwhile the percentage of broken capsule and seeds would increase with the power consumption increasing, thus the difficulty of separating and cleaning would appear and the quality of seeds on harvesting process would be worse, so it is not reasonable to enlarge power consumption for improving the threshing rate. The results showed that the threshing rate of rubbing was99%, the threshing rate of rolling was lower than86%, the threshing rate of impact was less than66%; and the threshing effect of rubbing was better than the other methods when the power consumption per unit rape seed was more than0.5J/g. It was recommended for rape threshing mechanism that rubbing method combined with impact method. So the technologies of thresh tooth combined with the woven screen and materials flowing up along with the axial direction were used in the threshing and separating system.(3) A new combined threshing system was designed. The thresh teeth and cutting knives were installed in the header roller to make the conventional header roller have new functions of threshing and cutting; the chain rake conveyor in conventional style was abandoned, and the feeding device of longitude axial threshing roller was connected directly back to the telescopic tooth unit of head roller, thus it would shorten the stage of conveying and simplified the structure of threshing system. In order to conduct the experiments, the longitude axial threshing device and combine threshing device were manufactured to test.(4) The process that the materials enter the longitude axial threshing system and move in it was observed and analyzed through the high-speed photography technique and the discrete element analysis method. The results showed that rape was pushed into the threshing system as the parabolic trajectory and take an irregular spiral motion in the threshing system; the axial velocity of rape revealed the approximate pulsating feature, the forces affected on rape came from the intermittent impact between the threshing teeth and the spiral guide plate. The axial speed of rape seed was faster than rape stalk, and the screw pitch of spiral trajectory was longer than rape stalk’s as well. The velocities of rape seed and rape stalk were higher in the periods of falling down and impacting than the period of rising up.(5)The longitude axial threshing roller was used to conduct the threshing test of ripe rape. Single factor experimental results showed that all factors such as roller speed, spike tooth space, roller screen gap and threshing drum axis tilt angle affect the grain prolapsed ratio. The grain prolapsed ratios has a parabolic relationship with the roller speed, in whi ch the ratio reach the maximum value when the roller speed is771rpm. It has a high valu e when the spike tooth space is100mm,225mm or200mm for front half of it and100mm for back half. It also has a good performance when roller screen gap is25mm or the thres hing drum axis tilt angle is25degree. The distribution of all of the ingredients prolapsed have a regularity that most of the small size extractions such as rapeseeds are in front of the area along the axis of roller while most of the large size extractions such as stem are i n the back area.