Design And Experiment Of Air-suction Pepper Precision Hole Direct Seeding Machine

In order to solve the problems of irregular seed shape and poor seed fluidity of hot pepper,it is difficult to achieve precision sowing.According to the agronomic requirements of pepper planting,a kind of air-suction pepper precision hole direct seeding machine was developed.The seed suction,seed carrying and seed metering process and core structure parameters of the air suction pepper precision seed metering device were studied.The seed accumulation process during seed addition and the disturbance process of seed stirring round table were simulated by EDEM simulation software,and the rationality of seed feeding box,stirring round table and seed disturbance trough was verified.The flow field in the air chamber was simulated by FLUENT software,the diameter and shape of the suction hole were determined,and the bench test was carried out.The prototype of the air-suction pepper precision hole seeder was designed and trial-manufactured,and the field experiments were carried out to verify the reliability and rationality of the core components and the whole machine design.The main results are as follows:(1)The physical characteristic parameters of different pepper varieties were measured,including the geometric characteristics of seeds,1000-grain weight,natural rest angle,sliding friction angle and bulk density,etc.,which provided the basic data for the structure design and simulation of air-suction pepper precision seed metering device.(2)A kind of air-suction precision seed metering device for hot pepper was designed.The force and movement of the seed metering device in the stages of seed suction,seed carrying and seed metering were analyzed,and the dynamic and kinematic models of the related working process were established.The structural parameters such as the diameter of seed metering plate,the shape and number of seed suction holes,the position and size of seed suction holes were determined,and the critical vacuum degree of seed filling and seed carrying was determined to be-139 pa,the rotation speed of seed metering shaft was10～50r/min and the diameter of seed suction hole was 1.5mm to 2.0mm,which provided a basis for the design and parameter optimization of seed metering device.(3)The seed accumulation process and seed mixing circle disturbance process are simulated by EDEM software,the accumulation process of seed flow in seed metering device is analyzed,and the movement trend of seed population and the motion law of seed pile under seed mixing circle disturbance are obtained,which provides a basis for the design of seed feeding box and seed mixing circle.The flow field in the negative pressure chamber is simulated by using FLUENT software,the effects of different suction hole diameter,different hole shape pressure and air flow velocity on the internal flow field are analyzed,and the chamfer shape with 45 °suction hole structure is determined.(4)Single factor test and quadratic orthogonal rotation combination test were carried out with different seed suction hole,seed metering shaft speed and vacuum degree of negative pressure chamber,and the optimum range and combination of test factors were determined.The single factor test results show that the chamfered suction hole is more suitable for pepper sowing,which verifies the simulation results,and determines the best range of suction hole diameter,rotation speed of seed metering shaft and vacuum degree of negative pressure chamber: 1.6～2.0mm,20～40r/min and 250～450pa.The results of quadratic regression orthogonal rotation combination test showed that when the diameter of seed suction hole was 1.8mm,the rotation speed of seed metering shaft was 29 rmax min,and the vacuum degree of negative pressure chamber was 350 Pa,the qualified rate of seed metering was 91.9%,the reseeding rate was 3.1%,and the missing sowing rate was 5%.A confirmatory test was carried out on the best combination of test factors,and the results showed that under the best combination of test factors,the qualified rate of planting was90.2%,the missing sowing rate was 3.5%,and the reseeding rate was 6.3%,which could meet the requirements of pepper sowing.(5)A kind of air suction pepper precision hole direct seeder is developed,and the structure and basic dimensions of the working parts such as frame,transmission system,trenching device and pressing device are determined.The field test results of the prototype show that the qualified rate of each hole of the sowing rate is 91.16%,the missing sowing rate is 0.18%,and the reseeding rate is 8.66%.The qualified index of hole distance is more than 89.10%,the replay index is less than 4.85%,the miss index is less than 10.90%,the coefficient of variation of hole distance is less than 23.76%,and the qualified rate of sowing depth is 86%.All the indexes reached the standard of JB/T 10293-2013 "Technical conditions of single seed(Precision)seeder" and met the agronomic requirements of pepper direct seeding production.