Evaluation on the Performance of Airflow Distribution Device of Pneumatic Seeder for Rapeseed through CFD Simulations

The seeding performance of a pneumatic seed-metering equipment for rapeseed has a significant bearing on the sowing effect. When the negative pressure falls abruptly, the pneumatic system experiences a significant loss of negative pressure. This will prevent rapeseed from being entirely absorbed by the seed plate, resulting in inconsistent seeding quantities along each row. In this study, CFD simulations were used to analyze the airflow field affecting the airflow transmission of an airflow distribution device. The essential structural characteristics of a conical cylinder conical-arranged kind of airflow distribution device were found, and the causes of negative pressure loss were analyzed from the standpoint of fluid kinematics. The optimal structural type of airflow distribution device was determined using fluid simulation. In addition, an orthogonal examination of the ideal type’s essential structural characteristics was conducted to minimize negative pressure loss during airflow transmission. Then, the influence of the negative pressure loss rate of the airflow distribution device on the variation coefficient of seeding quantity in each row of the seed-metering device was investigated using a bench test involving three factors: seed plate rotational speed, working negative pressure, and structure type. It was discovered that three parameters have highly substantial impacts on the negative pressure loss rate and the variation coefficient of seeding quantity in each row, and that the negative pressure loss rate correlates positively with the variation coefficient of the seeding quantity in each row. When negative pressure fell to 500 Pa, the negative pressure loss rate of the optimal structure type and the variation coefficient of seeding amount in each row of the seed-metering device fell by 6.25% and 3.45%, respectively. Field experiments reveal that the negative pressure loss rate of an airflow distribution device was below 20% and that the variation coefficient of seeding amount in each row of seed-metering devices was below 3.5%. The results can be used to analyze the construction of the pneumatic system and enhance the performance of the seed-metering equipment.