# Optimization of Screen-Hole-Clearing Devices for Mechanized Residual Film-Impurity Separation
## 4 Conclusions  
(1) This study engaged in a theoretical analysis and a numerical simulation of a tremmel-sieve-type residual film-impurity wind separator and screen-hole-clearing device. The simulation results indicated that the distance from the nozzle to the screen surface should be between 97.1 and 114.4 mm, the fan wind speed should be greater than 23.03 m/s, and the number of airflow pipes should be as small as possible. The limitation of the fan was accounted for. Accordingly, the distance from the nozzle to the screen surface was set as 95-115 mm, the fan wind speed was set as 23-25 m/s, and the number of airflow pipes was set as 1-5. The results of the force analysis of the blockage at the screen hole can provide theoretical support for solving the problems of small airflow speeds and the poor cleaning effect of some nozzles of various cleaning devices. (2) A Box-Behnken test was designed. Furthermore, a three-factor, three-level response surface analysis method was performed. The screen-hole-clearing device was tested for the clog-clearing performance. The analysis of the response surface revealed that the factors influencing the rate of impurities in the residual film in the descending order were the number of airflow pipes, air speed of the fan, and distance from the nozzle to the screen surface. The factors influencing the blockage rate of screen holes in the descending order were the air speed of the fan, number of airflow pipes, and distance from the nozzle to the screen surface. (3) After the optimization of the screen-hole-clearing device, the distance from the nozzle to the screen surface was 102 mm, the optimal number of airflow pipes was four, and the optimal fan air speed was 24 m/s. The actual machine verification test revealed that the minimum airflow velocity at each nozzle position in such a structure and for such working parameters was 15.8 m/s, which was greater than the theoretically calculated airflow velocity required for screen-hole clearing. The ratio of impurities in the residual film was 5.86%. Furthermore, blockage was observed in 5.41% of the screen holes. The ratios of impurities in the residual film and that of the blockage of the screen holes were 2.42% and 1.92% lower, respectively, than those before optimization. The clearing performance was significantly improved after optimization compared with that before optimization. The relative error between the experimental results and the predicted values was less than 19.7%, which indicated the accuracy of the model. \begin{table}
\begin{tabular}{c c c c c} \hline \hline \begin{tabular}{c} **Projects** \\ \end{tabular} & \begin{tabular}{c} **Distance from Nozzle to** \\ **Screen Surface/mm** \\ \end{tabular} & \begin{tabular}{c} **Fan Wind** \\ **Speed/(m s\({}^{-1}\))** \\ \end{tabular} & \begin{tabular}{c} **Number of** \\ **Air Pipes** \\ \end{tabular} & \begin{tabular}{c} **Impurity Rate in the** \\ **Residual Film \%** \\ \end{tabular} & \begin{tabular}{c} **Blockage Rate of the** \\ **Screen Holes \%** \\ \end{tabular} \\ \hline \
\begin{tabular}{c} Predicted value \\ Actual value 1 \\ Actual value 2 \\ Actual value 3 \\ \end{tabular} & 102 & 24 & 4 & 6.27 & 5.97 \\ \hline
\begin{tabular}{c} Pre-optimization values \\ \end{tabular} & & & & 5.38 & 4.75 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Comparison of optimization results with actual values. (4) The key factors affecting the blockage-clearing effect of the screen-hole-clearing device were determined. The results indicate that the device should be enabled to process more details. For example, a more energy-efficient, high-efficiency, and low-noise fan should be selected; the manufacturing materials should be replaced with low-cost materials that also satisfy the strength requirements. Furthermore, more efficient and stable feeding methods should be developed to ensure the good working performance of the original device. This can help achieve low power consumption and low costs and can promote further research. Conceptualization, C.X. and J.K.; methodology, C.X.