# Bench Test and Analysis of Cleaning Parameter Optimization of 4 L-2.5 Wheat Combine Harvester
## 3 Results
### Impurity Rate
#### 3.2.3 Analysis of the Response Effect of Each Parameter to the Impurity Rate  
From the data provided in Tables 7 and 8, it can be seen that operation speed (A), throttle opening (C), and fan speed (D) had greater impacts on theimpurity rate than the chaffer (B) and crank speed of shale shaker E. From Figure 6, it can be seen that operation speed (A) had a positive correlation with the impurity rate. The operation speed of A and fan speed D influenced the impurity rate, with the former having a secondary effect, as it determined the feeding quantity, and an increase in feeding quantity leads to an increase in threshing mixture cleaning. The cleaning device was unable to separate the grains and impurities in a timely manner. As such, the number of grains and impurities passing through the vibrating screen increased, and the impurity rate increased accordingly. An increase of fan speed D increased the separation amount in the threshing mixture and the number of impurities blown out while reducing the impurity rate. As also shown in Figure 6, the opening of chaffer B had a positive correlation with the impurity rate, as with an increased distance between the adjacent parallel sieves of the chaffer, the sieve penetration of the threshing mixture increased, and the separation of the grain and the impurity decreased, thereby \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Source** & **Sum of Squares** & **df** & **F** & **_p_ \\ \hline Model & 25.96 & 20 & 56.24 & \textless{}0.0001 & significant \\ A & 21.3 & 1 & 922.99 & \textless{}0.0001 & \\ B & \(1.41\times 10^{-3}\) & 1 & 0.061 & 0.807 & \\ C & 0.9 & 1 & 39.11 & \textless{}0.0001 & \\ D & 2.37 & 1 & 102.78 & \textless{}0.0001 & \\ E & 0.072 & 1 & 3.1 & 0.0905 & \\ AB & \(2.50\times 10^{-5}\) & 1 & \(1.08\times 10^{-3}\) & 0.974 & \\ AC & \(9.00\times 10^{-4}\) & 1 & 0.039 & 0.845 & \\ AD & 0.36 & 1 & 15.6 & 0.0006 & \\ AE & \(5.63\times 10^{-3}\) & 1 & 0.24 & 0.6258 & \\ BC & \(2.25\times 10^{-4}\) & 1 & \(9.75\times 10^{-3}\) & 0.9221 & \\ BD & \(2.25\times 10^{-4}\) & 1 & \(9.75\times 10^{-3}\) & 0.9221 & \\ BE & \(3.55\times 10^{-15}\) & 1 & \(1.54\times 10^{-13}\) & 1 & \\ CD & \(4.00\times 10^{-4}\) & 1 & 0.017 & 0.8963 & \\ CE & \(2.50\times 10^{-5}\) & 1 & \(1.08\times 10^{-3}\) & 0.974 & \\ DE & \(2.50\times 10^{-5}\) & 1 & \(1.08\times 10^{-3}\) & 0.974 & \\ A\({}^{2}\) & 0.63 & 1 & 27.23 & \textless{}0.0001 & \\ B\({}^{2}\) & 0.027 & 1 & 1.18 & 0.2879 & \\ C\({}^{2}\) & \(7.01\times 10^{-3}\) & 1 & 0.3 & 0.5865 & \\ D\({}^{2}\) & 0.076 & 1 & 3.29 & 0.0815 & \\ E\({}^{2}\) & 0.016 & 1 & 0.68 & 0.4163 & \\ Residual & 0.58 & 25 & & & \\ Lack of Fit & 0.54 & 20 & 3.67 & 0.0772 & not significant \\ Pure Error & 0.037 & 5 & & & \\ Cor Total & 26.53 & 45 & & & \\ R\({}^{2}\) & 0.9783 & & & & \\ \hline \hline \end{tabular}
\end{table} 
Table 7: Analysis of variance according to impurity rate. \begin{table}
\begin{tabular}{c c} \hline \hline
**Name** & **Contribution Rate (\%)** \\ \hline Operation speed A & 2.4301 \\ Opening of chaffer B & 0.1525 \\ Throttle opening C & 0.9744 \\ Fan speed D & 2.1543 \\ Crank speed of shale shaker E & 0.6774 \\ \hline \hline \end{tabular}
\end{table} 
Table 8: Hierarchy of parameters relative to impurity rate. increasing the impurity rate. Additionally, throttle opening C had a negative correlation with the impurity rate, because this parameter determines the air inlet area of the fan; with a greater air inlet area and air volume of the air field in the cleaning room, the wind force on thethreshing mixture, the amount of separation between the threshing mixture and the impurities, and the number of impurities blown out all increase while the impurity rate decreases. Furthermore, fan speed D had a negative correlation with the impurity rate, as increasing the fan speed increased the wind field speed, thereby increasing the amount of separation of the threshing mixture grain and impurity, as well as the amount of impurity blown out, resulting in a decrease in the impurity rate.