Pneumatic wheat seed-metering device often has a poor seed-filling state under the high-speed working condition, which adversely affects precision seeding. This paper describes a wheat seed-metering device that employs a combined mechanical–pneumatic seed-filling method. The orifice structure and seed-filling space at the nozzle are optimized to improve the seed-filling efficiency and seed-carrying stability. The working process of the wheat seed-metering device was analyzed, the principles of the seed-filling and seed-cleaning processes were elucidated, the factors influencing the seed-filling performance and seed-carrying stability were investigated, and the discrete element method–computational fluid dynamics (DEM-CFD) simulation method was employed to simulate the working process. The nozzle-orifice diameter, seed-filling-space angle, and rotation speed were determined as the simulation influence factors, and the trends of the nozzle void fraction, resistance to clearing, and initial dropping position were analyzed on a microscopic scale. On a macroscopic scale, the seed-leakage rate, reseeding rate, and grain-spacing qualification rate as performance-evaluation metrics were analyzed, and the significant order of impacts for these influencing factors and their interaction effects was obtained. Through secondary optimization experiments, the optimal parameter combination was determined to be a nozzle-orifice diameter of 1.7 mm, a seed-filling-space angle of 39.3°, and a rotation speed of 657.4 r/min. Static bench-validation tests and indoor vibration-environment simulation experiments were conducted, and the results were compared with a control group. The findings reveal that when the seed-metering plate rotation speed varies between 400 r/min and 1000 r/min, the optimized seed-metering plate exhibits a seed-leakage rate below 7.6% and superior performance in all indicators compared to the original seed-metering plate, indicating a significant improvement in seed-filling efficiency and seed-carrying stability.

The Huang-Huai-Hai region has a large area of cultivated land under the wheat-maize rotation system. With the large-scale promotion of conservation tillage technology in this region, a large amount of straw and stubble remain in the field after wheat harvest. Aiming at the problem that the large amount of wheat straw and stubble in this region leads to easy blockage during maize no-till sowing and restricts the improvement of machine operating speed, this study proposes a combined seedbed stubble cleaning method of "cutting, shifting, loosening, guidingand pressing", and designs a cutting-shifting combined seedbed stubble cleaning strip-till unit suitable for summer maize no-till sowing. By means of furrow opener discs for rolling cutting and stubble breaking, stubble shifting discs for shifting and separating stubble, and stubble pressing discs for guiding and pressing stubble, the unit solves the problem of seedbed straw cleaning under the condition of high speed summer maize sowing. The unit innovatively adopts front-mounted three point straw cutting structure, which can quickly cut the straw in the seedbed at first during operation. Through the staggered outward turning stubble cleaning wheel structure, efficient removal of straw in the seedbed is realized. Symmetrically arranged deflector wheels with adjustable opening closing angles on both sides of the subsoiling shovel effectively control the disturbance range of cultivated soil during operation, and at the same time can effectively crush the turned soil to form fine soil backfilling. The unique tooth profile design of the deflector wheels can press the straw at the edge of the seedbed into the soil to form a straw barrier around the seedbed, thus effectively reducing straw backfill into the seedbed.This study analyzes the influence of parameters such as the included angle of stubble cleaning wheels and the opening closing angle of deflector wheels on the straw cleaning effect, and determines the value ranges of each key parameter. EDEM-ADAMS simulation tests were carried out to analyze the straw movement trajectory, soil turnover characteristics and straw removal rate during the operation of the stubble cleaning unit under different toothed disc combinations. The results show that the order of the influence of each test factor on the field straw removal rate from largest to smallest is the radial included angle of stubble cleaning wheels, forward speed, and opening angle of guide wheels. When the machine forward speed is 12 km/h, the opening angle of guide wheels is 6.3°, and the radial included angle of stubble cleaning wheels is 47.26°, the maximum straw removal rate reaches 95.1%. Restricted by the preparation accuracy of the sample mechanism, accuracy adaptation treatment was carried out on the high precision parameters obtained from simulation analysis. A parameter combination with machine forward speed of 12 km/h, deflector wheel opening-closing angle of 6° and stubble cleaning wheel included angle of 47° was selected for simulation tests. Under this condition, the straw clearance rate reaches 95.08%, and all indicators meet the design requirements. Field tests on the combined operation performance of each component of the seedbed stubble cleaning strip-tillage machine were conducted. The field test results show that the strip-tillage machine has good performance in various environments, and the prepared seedbed meets the growth needs of maize. At an operating speed of 12 km/h, the seedbed stubble cleaning width of the strip-till machine is 30 cm, and the straw clearance rate reaches 95.02, which is basically consistent with the simulation results. The test results indicate that under high speed operation conditions, sowing in the seedbed treated by the seedbed stubble cleaning device can effectively ensure the uniformity of sowing depth, keep the sowing depth basically consistent,improve land flatness, and provide favorable conditions for maize growth. This paper provides new ideas and methods for the design of stubble cleaning mechanisms for no-till sowing, which is of great significance for field management in the Huang-Huai-Hai region and has ecological value for cultivated land protection.