Design And Experiment Of Pressure Balance Device For Pneumatic Seeding System

With the acceleration of urbanization and land intensification,large-scale management in China,pneumatic conveying seeder is the development trend of large-scale seeder.As the pneumatic seeding system is the key component of the pneumatic conveying seeder,an in-depth study on seeding tube of the pneumatic seeding system is conducted to explore the effect mechanism of seed tube lengths on seeding performances.According to the effect mechanism,a grooved wheel pressure balancing device is designed to solve the problem of uneven seed metering in tubes,which is caused by unequal lengths of tubes.The main research contents and conclusions are as follows:1.Physical tests was conducted to measure the physical and mechanical parameters of alfalfa seeds and wheat seeds,which provided a basis for the experiment and study and the parameter design of a grooved wheel pressure balancing device.2.According to theoretical analysis of the variation regulation of average airflow velocity in the tube with different seed tube lengths,it was concluded that different seed tube length leads to various average airflow velocity,which affects seed metering speed in the tube and thus affects the amount of metered.With the increase of seed tube length,the average flow velocity decreases,and the seed metering speed in the tube decreases,resulting in the decrease of seed distribution.3.Computational fluid dynamics(CFD)simulation was conducted to get the map of speed flow field in tubes in different lengths.Moreover,tests with different tube lengths as dependent factor and variation coefficient of each row displacement consistency,variation coefficient of total displacement stability and average airflow velocity in the seed tube as independent factors were studied in the experiment platform.Simulation analysis and test results showed that when seed tube length increased,the average airflow velocity,the seed metering speed and the corresponding seed quantity distribution decreased.And the influence with seed tube length less than 2.75m was significant.When seed tube length was between 2.75m and 6.25m,both the decrease of average flow velocity and the decline of the seed velocity slowed down,and the seeding amount changed smoothly.In addition,the variation coefficient of each row displacement consistency was 1.58%,and the variation coefficient of total displacement stability was 0.90%,which could meet the related.4.Aiming at avoiding the effects of seeding tube length on seeding performances,a grooved wheel pressure balancing device was designed,and its reliability and feasibility were verified by experiment platform tests.Test results showed that the average airflow velocity in each tube was basically same after installing the grooved wheel pressure balancing device.The variation coefficient of each row displacement consistency of alfalfa seed decreased from 12.79%to 2.12%,the variation coefficient of total displacement stability of alfalfa seed was 0.56%,and the damage rate of alfalfa seed was 0.38%.The variation coefficient of each row displacement consistency of wheat seed decreased from Il3.08%to 0.58%,and the variation coefficient of total displacement stability of wheat seed was 0.41%,and the damage rate of wheat seed was 0.42%,which met the related requirements and standards of seeding tube.It proved that the grooved wheel pressure balancing device could ensure each row displacement consistency.