To improve the problem of low seeding efficiency facing the single-row planting mode traditionally used in China, this study aimed to design a novel three-row pneumatic precision metering device. The working principle and main structure were introduced in the paper. The three main factors affecting the seeding performance comprised of vacuum pressure, angular velocity of the metering tray, and taper angle of the sucking hole. A Box-Behnken experiment design having the qualified index and missed seeding index as the experimental index was used, and the results indicated that optimal performance of the metering device was achieved when the vacuum pressure was 2.16 kPa, the angular velocity of the metering tray was 29.43 rpm, and the taper angle of the sucking hole was 61.51°. The qualified index of the inner, middle, and outer ring was 95.12%, 94.68% and 94.24% respectively, while the missed seeding index of the inner, middle, and outer ring was 3.67%, 3.12% and 2.58% respectively under the optimal combination of parameters. The bench test results were basically consistent with the optimized results. This paper can provide support for the design of a three-row pneumatic precision metering device for Brassica chinensis.

In view of the low seeding efficiency and precision of seeders used for Brassica chinensis in China, a new double-row pneumatic precision metering device for Brassica chinensis was designed, fabricated, and evaluated. With the characteristics of small size and high sphericity of Brassica chinensis seeds in mind, the structure and key dimensions of the metering plate were determined, and a force analysis of the seed-filling process was carried out. The negative pressure (NP), angular velocity (AV) of the metering plate, and cone angle (CA) of the suction hole were selected as the main influencing factors of the experiment. In order to explore the influence of each single factor and the interaction between factors on the seeding performance, a single factor experiment and a central composite design (CCD) experiment were designed, respectively, and the experimental results were analyzed by analysis of variance (ANOVA). After optimizing the main influencing factors such that the target of the qualified index (QI) was greater than 94% and the miss index (MI) was less than 2.5%, it was found that when CA was 60°, NP was 1.55–1.72 kPa, and AV was 1.1–1.9 rad/s, the seeding performance was excellent. The bench verification results of seeding performance (94% ≤ Q ≤ 100%, 0 ≤ M ≤ 2.5%) and the coefficient of variation (CV) of seed mass (CV of seed mass in outer and inner circle: 5.15%; CV of total seed mass: 8.60%) under the condition of parameter optimization were analyzed; as a result, the accuracy of the parameter optimization was confirmed.

Highlights A novel pneumatic disc-type garlic precision seed-metering device was designed. Numerical simulations of the airflow field inside the seed-metering device were carried out with FLUENT Software. The diameter of the suction hole, the rotational speed of the seed plate, and negative pressure were used to evaluate the performance of the seed-metering device. The reasonableness of the optimal combination of parameters was verified by a bench experiment. Abstract. To solve the problem of high seed damage rate and low transplanting efficiency on traditional mechanical garlic seed-metering devices, this article designed and experimented with a novel pneumatic disc-type garlic precision seed-metering device by using theoretical calculations and orthogonal experiments. The overall structure of the device and the basic principles of each working stage were described. Numerical simulations of the airflow field inside the seed-metering device were conducted with FLUENT software to determine the optimal location of the negative pressure outlet and the number of suction holes. A three-factor, three-level Box-Behnken quadratic rotation orthogonal combination experiment was carried out to evaluate the performance of the seed-metering device in terms of the qualified index, miss index, and multiple index. The results showed that the optimal combination of parameters was a suction hole diameter of 10.03 mm, a rotational speed of 11.70 rpm, and a negative pressure of 7.02 kPa. With the optimal combination of parameters, the seeding qualified index was 88.04%, the miss index was 8.65%, and the multiple index was 3.31%, which met the design requirements. The results of the bench experiment were basically consistent with the results under the optimal combination of parameters. This design can provide a theoretical basis for garlic’s precision transplanting. Keywords: Airflow field, FLUENT, Garlic’s precision transplanting, Orthogonal combination experiment, Seed-metering device.

Optimization of a three-row air-suction Brassica chinensis precision metering device based on CFD-DEM coupling simulation