# Numerical Simulation and Optimization of the Airflow Field of a Forage Drum Mower
## 6 Conclusions  
In this paper, the airflow field around the double-drum cutter equipped with twisted blades, tilting discs, and guide plates was studied. Orthogonal experiments were carried out using the CFD numerical simulation model, with the structure and operating parameters optimized to generate a better airflow field. The main conclusions of this paper are presented as follows:  
1. A theoretical analysis of the airflow field around the double-drum cutter was conducted to construct a numerical simulation model of the airflow field of the double-drum cutter for analysis of the distribution of the airflow field and its impact on the process of forage cutting. 2. A four-factor, three-level orthogonal simulation experiment was performed using a numerical simulation model of the airflow field of the double-drum cutter. Also, the optimal structure and operating parameters of the cutter were determined by using the integrated balance method as follows: a disc speed of \(2000\) r/min, a blade twist angle of \(8^{\circ}\), a disc tilt angle of \(4^{\circ}\), and \(2\) grass guide plates. Under these conditions, the numerical simulation of the airflow field was conducted to find out that the velocity of the lifting airflow was \(7.5814\) m/s, that of the feeding airflow was \(11.4379\) m/s and that of the gathering airflow was \(4.1857\) m/s. All of them are larger in terms of airflow speed, and the airflow field formed is expected to promote the feeding of forage and the reduction of recutting. 3. The model of airflow field characteristics parameters prediction was constructed, and a test bench was built according to the optimal structure parameters of the cutter. According to the results of verification experiments, the average error of the prediction model was \(-5.83\%\) for the velocity of the gathering airflow, \(2.37\%\) for the lifting airflow, and \(4.20\%\) for the feeding airflow, which confirms the validity of the simulation results and the prediction model. The results of the study provide a practical reference for the optimal design of the double-drum cutter. \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Indexes**} & **Disc Speed** & **Model Predicted Values** & **Measured Value** & \multirow{2}{*}{**Error (\%)**} \\  & **(m/s)** & **(m/s)** & **(m/s)** & \\ \hline \multirow{3}{*}{Gathering airflow velocity \(v_{g}\)} & \(1480\) & \(2.62\) & \(2.88\) & \(-9.03\) \\  & \(1780\) & \(3.26\) & \(3.38\) & \(-3.55\) \\  & \(1960\) & \(4.25\) & \(4.47\) & \(-4.92\) \\ \hline \multirow{3}{*}{Lifting airflow velocity \(v_{l}\)} & \(1480\) & \(4.76\) & \(4.53\) & \(5.08\) \\  & \(1780\) & \(5.84\) & \(5.69\) & \(2.64\) \\  & \(1960\) & \(6.5\) & \(6.54\) & \(-0.61\) \\ \hline \multirow{3}{*}{Feeding airflow velocity \(v_{l}\)} & \(1480\) & \(7.46\) & \(7.21\) & \(3.47\) \\  & \(1780\) & \(9.17\) & \(8.64\) & \(6.13\) \\ \cline{1-1}  & \(1960\) & \(10.63\) & \(10.32\) & \(3.00\) \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Results of the verification experiments. **Author Contributions:** Conceptualization, B.W. and Y.X. ; methodology, B.W. ; software, B.W., T.Z. and H.Q. ; validation, T.Z. and Z.L. ; H.Q. and T.H. ; formal analysis, B.W. and T.Z. ; investigation, B.W., T.Z. and T.H. ; resources, B.W. ; data curation, B.W. and T.Z. ; writing--original draft preparation, B.W. and T.Z. ; writing--review and editing, B.W. ; visualization, B.W. and T.Z. ; supervision, B.W. ; funding acquisition, B.W. and Y.X. All authors have read and agreed to the published version of the manuscript. **Funding:** This research was funded by the Scientific Research Fund of the Hunan Provincial Education Department (grant number 19B261), The Science and Technology Innovation Program of Hunan Province (grant number 2021 NK1050-1) and Changsha Municipal Natural Science Foundation (grant number kq2208071). **Institutional Review Board Statement:** Not applicable. **Informed Consent Statement:** Not applicable.