**3. Results and Discussion**

### *3.1. Conveying Performance Test Analysis*

#### 3.1.1. Regression Analysis

The experimental results are shown in Table 4. Using Design-Expert 8.0.6 software to regress and fit the experimental results, we obtained the regression mathematical model of conveying time *Y*:

$$\begin{array}{l} Y = 0.212A^2 + 5.463 \times 10^{-6}B^2 + 1.057 \times 10^{-4}C^2 + 6.25 \times 10^{-4}AB - 1.65 \times 10^{-3}AC \\ \ -1.75 \times 10^{-5}BC - 2.181A + 9.5 \times 10^{-4}B - 0.0983C + 41.932 \end{array} \tag{9}$$

The determination coefficient *R*<sup>2</sup> of the regression equation was 0.998, indicating a high degree of fitting; the regression model was analyzed by variance, and the results are shown in Table 5. It can be observed that the model had a value of *p* < 0.0001, indicating that the regression equation is significant and can describe the relationship between each factor and response value; the lack of fit was*p* = 0.1882 > 0.05, showing that the residual item is not significant, and there are no other main factors affecting the results, so the regression model was established. *p* < 0.01 was set for *A*, *B*, *C*, *BC*, *A2*,*B2*, and *C2*, which have a very significant effect on the results; *p* < 0.05 was set for *AB* and *AC*, indicating that they have a significant effect on the results; and *p* > 0.05 was set for factors and interaction terms, which have no significant effect on the results. The order of significance of each factor on the screening efficiency, from large to small, was feed rate, feed length of the stalk, and speed of the tangential threshing rotor.


**Table 4.** Results of the conveying performance test.

**Table 5.** Variance analysis of the conveying time.


Note: *p* < 0.01 (extremely significant, \*\*); *p* < 0.05 (significant, \*).

According to the regression equation, the influence of the interaction of factors on the results is shown in Figure 11. When the speed of the tangential threshing rotor is low, the conveying time decreases with the shorter feed length of the stalk. The shorter the length of the stalk, the better the passing performance in the transition area between the tangential threshing rotor and the longitudinal axial flow rotor, and the shorter the conveying time. When the speed of the tangential threshing rotor is high, the conveying time decreases first and then increases with the shortening of the feed length of the stalk. The conveying time

decreases first and then increases with the increasing speed of the tangential threshing. This is because the conveying capacity increases when the rotating speed of the cutting drum increases; if the speed of the tangential threshing rotor is too high, the stalks are not fed in time by the axial threshing rotor, and there is congestion in the transition between the axial flow rotor and the tangential threshing rotor, causing the conveying time to increase.

**Figure 11.** Effect of the interaction of factors on the conveying time.
