## 3 Results  
### Analysis of Simulation Results  
Four cross sections are selected, as shown in Figure 9, and the flow field inside the device is analyzed from the simulation results of the cross sections. Compared with the velocity vector diagram of cross sections 1-3, there is no vortex or inward backflow in the volute tongue area of the device, so the residual film is not affected by the vortex when it moves to this area and is even sucked into the diversion shell again. By comparing Figures 10b, 11b and 12b, it can be seen that: Under the action of the centrifugal force, the gas obtains kinetic energy, and the air velocity increases gradually from the inside to the outside of the blade. At the film conveying port, the air velocity on the right side is lower than that on the left side, and the velocity gradient changes obviously. In the simulation results of cross section 3 and cross section 2, the gas molecular flow and gas velocity are the same because the structure of the film removal device is symmetric about cross section 1. Figure 11a shows that a part of the gas is discharged outwards along the surface of the film removal area on the central section. However, due to the high speed of the blade, when the  
\begin{table}
\begin{tabular}{c c} \hline \hline
**Parameters** & **Value** \\ \hline The average firmness of the soil (depth: 0–100 mm) & 171 kPa \\ The average moisture content of the soil (depth: 0–100 mm) & 13\% \\ Residual film content in soil (depth: 0–100 mm, area: 1 m\({}^{2}\)) & 7 g \\ \hline \hline \end{tabular}
\end{table}
Table 2: The parameter settings of the test field.  
Moreover, in Figure 13, the maximum velocity is 28.06 m/s, and the average velocity is 12.34 m/s. It is known that there is a small amount of cotton stalks on the surface of residual film, and the suspension velocities of residual film and cotton stalks are approximately 3 m/s and 10 m/s, respectively [45], so the gas velocity at the film conveying port meets the requirements of film removal.  
However, Figure 14 shows that there is a vortex region (including a small amount of inward air supply area) near the position of the cross section near the plates on both sides of the diversion shell, and the vortex region accounts for a large proportion of the effective region (the effective region is defined as the rectangular region away from the film delivery port when the film removal blade moves to the lowest point, and there is no vortex outside the effective region). The existence of the vortex region makes part of the residual film and its mixture churn and rotate violently in the diversion shell and cannot enter the residual film recovery box through the film conveying port under the action of airflow, which easily causes blockage. In severe cases, the residual film that has been removed is entangled with the blade again because of the effect of the vortex. The vortex region not only hinders the transport of residual film in the diversion shell, but also leads to a decrease in the film removal rate.  
Figure 12: Velocity vector diagram of cross section 2 (**a**) and velocity nephogram of cross section 2 (**b**).  
Figure 13: Velocity nephogram of film conveying port surface.