# Model Study on the Combination of Operating Parameters of Corn Kernel Harvesters
## 4 Results and Discussion
### Harvester Engine Speed in Relation to Threshing Cylinder Operating Parameters  
As shown in Figure 5a, there was a linear relationship between threshing cylinder speed and the engine speed, and the root mean square error of the linear fit was 0.8819. When the harvester was operating in the field, the engine operated at a constant speed, so the threshing cylinder speed was constant, which ensured the operating quality. Reducing fluctuations in the engine speed meant reducing fluctuations in the threshing cylinder speed, which would have reduced fluctuations in the operating quality of the harvester. Figure 5b shows that the engine load increased with an increase in the forward speed and feed rate. At a concave clearance of 20 mm, when the output power reached the maximum output power \(P_{\text{e,max}}\), the engine speed started to drop continuously from 2200 r/min; the cylinder speed dropped simultaneously. When the engine speed dropped around 1800 r/min, the cylinder was observed to have a tendency to clog. After dropping to 1700 r/min, the cylinder clogged, which subsequently reduced the feed rate. The engine load decreased, then the engine speed and cylinder speed rose back to the set value. The threshing cylinder speed and engine speed increased or decreased with the curve of the change in feed rate. With a concave clearance of 30 mm or 40 mm, when the output  
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline \multirow{2}{*}{**Levels**} & **Feed** & **Cylinder** & **Concave** & **Engine Speed** & **Crushing** & **Impurity** & **Kernel** & **Cylinder Speed** \\  & **Rate** & **Speed** & **Clearance** & **Variation Rate** & **Rate** & **Rate** & **Loss Rate** & **Variation Rate** \\ \cline{2-10}  & \(x_{1}\) & \(x_{2}\) & \(x_{3}\) & \(y_{1}\) & \(y_{2}\) & \(y_{3}\) & \(y_{4}\) & \(y_{5}\) \\ \hline
1 & 1 & 1 & 1 & 100 & 3.33 & 1.96 & 9.10 & 10  
power reached the maximum output power \(P_{\text{e,max}}\), the engine speed began to decline continuously from 2200 r/min, but the engine speed variation rate was less than 10%. The trend of change was close to that at 20 mm concave clearance, and it could still operate at a higher feed rate. Figure 5b,c shows that the engine speed of the test group with a 20 mm concave clearance fluctuated the most sharply when the feed rate increased. The fluctuation in the engine speed would lead to a decrease in harvest quality. This indicates that the concave clearance of 20 mm had a greater influence on the engine speed. The concave clearance could be chosen to be different from 20 mm; 30 mm to 40 mm could be selected. Meanwhile, the operating efficiency could be improved by increasing the feed rate. However, at different concave clearances, changes in the feed rate would cause changes in the engine speed \(n\) and the output power \(P_{\text{e}}\). Thus, to ensure operating quality, a suitable feed rate should be selected. In Figure 5, as the concave clearance increased, the fluctuation in engine and cylinder speed slowed down, even if the feed rate increased. The harvester's operating quality was improved by adjusting the feed rate, the concave clearance, and threshing cylinder speed; the concave clearance was not easy to adjust in real time and a concave clearance value was pre-selected before the operation, followed by adjustment of the threshing cylinder speed and finally the feed rate. When the engine speed was reduced by more than 10%, there was a tendency towards blockage and adjustment was required; when the harvester engine  
Figure 5: The relationship curve between engine speed and feed rate, cylinder speed, and concave clearance. (**a**) The relationship curve between the engine speed and threshing cylinder speed of the harvester. (**b**) Curve of engine speed change with the feed rate. (**c**) Curve of cylinder speed change with the feed rate. speed was reduced by 20%, both its speed \(n\) and output power \(P_{\text{e}}\) dropped rapidly and serious blockage occurred in the harvester.