| Based on the systematic analysis of existing rice direct seeding machines and pneumatic seeders at home and abroad,this paper analyzes the factors that affect the seeding performance of the seed metering device and found that there are few study of the structural parameters of whole pneumatic system effects on seeding performance from the system point of view.For this problem,this paper designed a king of pneumatic system including a air pressure source,with the gas distribution pipeline and sowing monomer,and analysis of the working principle of the pneumatic system.Through the bench test,the negative pressure characteristics of the pneumatic system are explored and the influence to the rule of seed is tested.CFD calculation fluid simulation software is used to simulation optimization analysis the airflow in the positive and negative pressure gas distribution pipeline of the pneumatic system.Through of direct seeding planter,the feasibility of the pneumatic system was verified and the performance of seeding after field test was analysized.The main contents of this paper are as follows:(1)A pneumatic system have been designed and produced which including power system,air pressure source,gas distribution pipeline,sowing monomer and frame,The pneumatic rice direct seeding planter was produced.The paper analyzes the power transmission route and working principle of the whole system.The reasonable air pressure source and pipeline arrangement are determined by theoretical analysis.A kind of monomer sowing device is designed and produced.(2)Based on the development of the pneumatic system of rice direct seeding planter,the test bench was built,and the factors such as fan speed,planting plate rotating speed and planting rows were tested by using the pneumatic system test platform.The mathematical data were used to sort out the experimental data,The influence of the above factors on the negative pressure of the seed metering device was studied and the influence degree was evaluated.The relationship model between the total negative pressure of the fan,the negative pressure of the seed metering device and the speed of the fan,planting plate rotating speed and planting rows,provided the combination area matched parameters that ensured the system's seeding performance.At the same time,the stability of the seeding capacity of the pneumatic system seed metering device is analyzed and the consistency of each row's seeding capacity is analyzed.The main conclusions are as follows:(1)The study concludes that the total negative pressure of HG-2200 fan is different with the speed of rotation under different planting rows.The negative pressure of the seed metering device increases with the increase of the fan speed and decreases with the increase of the number of the seed metering device.The negative pressure of the seed metering device resulting in periodic flucturations with planting plate spin,and with the increase of the speed of the planting plate,the frequency of the negative pressure fluctuation of the seed metering device increases,the effect of planting plate rotating speed on the average value of the negative pressure of the seed metering device was not significant.The bench test showed that the stability of seeding capacity of seed metering device was not satisfying at high rotational speed.The coefficient of variation of the consistency of each row's seeding capacity is from 2.10% to 5.04%.(2)The relationship model between the total negative pressure of the fan and the speed of the fan and the number of seed metering device(planting rows)was established.The coefficient of determination was 0.92,and the relative error of the experiment is from-15.92% to 12.12%.The reason is that there is a certain deviation in processing process between different kind of seed metering device.According to the number of planting rows,the relationship between negative pressure and fan speed was established,and the regression coefficients were 0.96,0.97 and 0.97 respectively.The relative error of the experiment is from-2.70% to 5.40%.This model can be used to calculate the fan speed when the seed metering device reaches the design average negative pressure when the rated power of the fan is 2200 W.(3)The negative pressure model of the seeder constructed by the bench test of the pneumatic system verifies the feasibility of the pneumatic system of the rice direect seeding planter,under different planting rows,the designed pneumatic system is able to distribute the airflow of the fan evenly to each row,it can ensure that the seed metering device on each row can work in a stable working pressure,it can provide guidance for determine the parameters of the pneumatic system and the actual production.(3)Based on the simulation analysis method of CFD(Computational fluid dynamics),ANSYS simulation software is used to model the designed pneumatic system.The simulation model is based on the air of the air flow field of the gas distribution pipeline.The physical model is established and simulated.Through the simulation test method,contrast the influence of the different diameter of the gas distribution pipeline,the different shape of the inlet and outlet and splite mode to the inlet and outlet pressure and the speed loss of the gas distribution pipeline,and the optimal piping structure parameters are obtained,and the gas distribution pipeline is optimized design.The main order of the factors influencing the pressure loss of the gas distribution pipeline is the angle ? between the main pipe and the branch pipe,the splite mode and the main pipe diameter.The main order of the factors influencing the speed loss of the gas distribution pipeline is the splite mode,the main pipe diameter and the angle ? between the main pipe and the branch pipe.The final determination of the optimal negative pressure distribution channel using ? type split way,the main diameter D = 50 mm,angle ? is determined to 100 degrees,the optimal positive pressure distribution pipeline with type ? split way,the main diameter D = 50 mm,angle ? is determined to 100 degrees.(4)On the basis of the development of rice direct seeding planter,the field experiment was carried out,and the seeding performance of rice seeding planter after field planting was analyzed by using the relevant test data processing method of mathematical statistics.The conclusions are as follows: The average pass rate was 72.36%,the average leakage rate was 16.93%,the average replay rate was 10.71%,the average hill distance was from 153.19 to 185.91 mm,and the variation coefficient of the hill distance was from 14.76 % to 21.18%.The rice direct seeding planter adopts the pneumatic system designed in the early stage.The field test results show that the designed pneumatic system can provide enough stable negative pressure for the seed metering device to ensure the seeding performance of the rice direct seeding planter. |
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