## 4 Conclusions  
This study focused on the structural design and optimization of the air-assisted seeding system's pressurized tubes (or diffusers). By examining the influence of pressurized tube structure on the uniformity of seed distribution within the seeding system, we employed a coupled simulation approach to investigate the motion behavior and characteristics of wheat seeds inside the pressurized tubes. Our analysis unveiled the underlying mechanisms affecting the uniformity and distribution consistency of the gas-solid two-phase flow. Through orthogonal experimental analysis, we evaluated the effects of different pressurized tube structures on seed distribution uniformity, pressure loss, and the coefficient of variation in discharge rates for various rows. Key findings and conclusions are as follows. In response to the challenge of inadequate seed distribution uniformity within the air-assisted seeding system, a pressurized tube structural optimization was carried out using an orthogonal experimental design. Theoretical analysis was employed to investigate the mechanisms behind pressure loss within the pressurized tubes. The optimization of the pressurized tube structure via coupled simulation resulted in minimized variations in gas flow velocity and reduced turbulence effects. Furthermore, the pressure loss was effectively reduced. Under various inlet gas flow rates and seeding quantities, the coefficient of variation in discharge rates for all rows was limited to a maximum of 3.12%, meeting standard requirements. The results from the analysis indicated that the primary and secondary factors affecting pressure differences were the pressurized tube length, corrugation quantity, corrugation width, and corrugation depth. Regarding the coefficient of variation in distribution uniformity, the dominant influencing factors were  
\begin{table}
\begin{tabular}{c c c c} \hline \multirow{2}{*}{**Experimental Design**} & **Inlet Airflow** & **Seeding Quantity** & \multirow{2}{*}{**Pressure Loss/Pa**} \\  & **Velocity**\(\mathbf{v}\)/\(\mathbf{\cdot}\mathbf{\  
corrugation depth, corrugation width, corrugation quantity, and pressurized tube length. Based on the combination of variance analysis and single-factor mean analysis, the optimal parameters for the pressurized tubes were determined to be a pressurized tube length of 800 mm, corrugation depth of 8 mm, corrugation quantity of 6, and corrugation width of 50 mm. The coupled simulation analysis revealed that, under identical seeding quantities and within a certain range of inlet gas flow rates, an increase in inlet gas flow velocity led to initial reductions in both the coefficient of variation for seed distribution uniformity and pressure loss. This suggests that the choice of inlet gas flow velocity plays a significant role in the seeding system's performance, offering valuable insights for the design of air-assisted seeding systems. Validation through simulation experiments confirmed that the optimized pressurized tube structure consistently met the requirements for the coefficient of variation in discharge rates under varying inlet gas flow rates and seeding quantities. This optimization effectively reduced turbulence, minimized pressure loss, and improved the uniformity of seed distribution within the seeding system. These findings serve as a theoretical foundation for the design of subsequent components in air-assisted seeding systems. Conceptualization, J.Z. and Y.L. ; methodology, J.Z. ; software, L.L. ; validation, Z.L. ; formal analysis, Y.L. ; investigation, L.L. ; resources, Z.L. and Y.L. ; data curation, J.Z. and Y.L. ; writing original draft preparation, J.Z. ; writing review and editing, Z.L. ; visualization, Z.L. ; supervision, L.L. ; project administration, L.L. ; funding acquisition, L.L. All authors have read and agreed to the published version of the manuscript.