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CFD Simulation and Experiments of Pneumatic Centralized Cylinder Metering Device Cavity and Airflow Distributor

The distribution of airflow field in the pneumatic centralized cylinder metering device cavity, airstream distributor and different angle seed feeding tubes was investigated based on the pneumatic centralized cylinder direct-seeding metering device to study the effect on the movement law of rice seed. In total, three suction hole sizes (1.5 mm, 2 mm and 2.0 mm 45° wedge) were used for CFD simulation. The results showed that under the same inlet vacuum, the pressure at the 1.5 mm hole is higher than the other two types of holes, and the five measurement points of the 2 mm hole are more stable than the other two types of holes. At the positive pressure seed feeding area, the inlet pressure was set as 1.5 kPa, and the outlet pressure was set as 0 Pa. The pressure distribution at different measuring points showed that the 2 mm 45° wedge had the most uneven positive pressure distribution, and the 1.5 mm hole had higher positive pressure distribution than the 2 mm hole in general. Three different structured airflow distributors were designed. CFD simulation experiments showed that the arc transition type presented better uniformity than the other two types. The uniformity experiments at the ends of the seed-feeding tubes indicated that the airflow velocity had the trend of large in the middle and small at two sides. Finally, the movement law of the rice seeds in seed feeding tubes at different angles was obtained by using high-speed photography. The results showed that the rice seeds in tube C (maximum angle) presented a movement posture of falling sector a and kept falling after colliding in sector b; the rice seeds in tube B (the second angle) presented a movement posture of falling in sector a and kept falling after colliding in sector b. The above research provides a reference for the optimal design of a pneumatic centralized cylinder metering device.