The planter plate is the most important component of the pneumatic hill-drop seed metering system for rapeseed. The structural parameters of the planter plate are the primary determinants of rape planting. The key structural and operational parameters, such as the layout of the suction hole, its diameter, and its shape, were determined through theoretical analysis. Fluent is used to simulate the flow field of various types of suction holes, and the effect of suction hole shape on the change in the flow field of the suction chamber shell is analyzed. Under the same boundary conditions, the results indicate that the maximum velocity of the end face of the horn hole and the average pressure of the section are the highest. Using a high-speed camera, the effects of suction hole diameter and shape on seed filling performance were studied, and the results of Fluent simulation analysis were validated. The optimal seed metering device operating parameters were as follows: planter plate speed of 30–70 r/min and negative pressure of −2.5–−1.5 kPa. The influence of working negative pressure and the rotational speed of the planter plate on seed arrangement performance was studied within the optimal operating parameter range. In order to improve the performance of rational close planting in the seed planter, the multi-objective optimization design of working parameters and the verification test were also conducted. The results showed that with the best combination of working parameters, the empty broadcast rate does not go above 3%, the hole number qualified rate does not go below 96%, and the difference between them and the theoretical optimization result does not go above 5.5%.

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.