Abstract:The pneumatic style straw deep burying and returning machine enjoys comprehensive functions in the aspect of stubble breaking, straw picking and crushing, ditching and crushing, inter-row deep loosening, deep-buried straw, soil covering, and finally buries the straw below 20cm between rows and at the same time constructs the furrow loose and ridge compaction plough layer structure. According to the technical requirements of reasonable tillage construction, the pneumatic conveying device was designed. The main structural parameters of the conveying device were as follows: the cross section of the conveying pipe was 0.2m×0.2m square pipe;the impeller diameter was 0.55m;the width of impeller was 0.17m; the inlet diameter was 0.26m;the width of fan shell was 0.2m;the outer diameter of screw blade was 0.25m;the diameter of the screw shaft was 0.09m;the screw pitch was 0.2m;the thickness of the screw blade was 0.003m;and the clearance between the outer diameter and the inner surface of the conveying pipe was 0.005m. According to the test of suspended velocity for corn, the suspended velocity of upper, middle and lower parts of 10cm corn stalk was 10.4m/s, 12.3m/s and 12.7m/s, respectively, with an average of 11.9m/s. The test results and simulation error was 7%. On the basis of gas-solid coupling theory, the CFD-DEM method was used to simulate the two-phase flow of gas-solid in the conveyor. When the angle was 30°and rotation speed was 1800r/min, the minimum velocity of straw in the conveying pipeline was 5.21m/s. And the corresponding velocity of air flow was 17~27m/s. At the outlet, the velocity of straw reached 6.06m/s, and 2~27m/s at the air flow rate. The number of straw inside the fan was 24 at 1.2s, and then it had the most effective delivery. The results of field experiment showed that the optimum combination of performance parameters of pneumatic conveyor was as follows: blade bending angle was 30°, straw coverage was 1.2kg/m2, fan speed was 1800r/min and the qualified rate of deep-buried was 93.2%. The research had effectively improved the deep-buried quality and also can provide reference on further study on performance improvement of pneumatic straw deep burying and returning machine as well as the promotion of agriculture mechanization level.
