## 4 Conclusions  
1. The thrreshing efficiency increased with the increase in the roller's rotational speed and feed rate up to a feed rate level of 800 kg/h. The maximum threshing efficiency (97.64%) was recorded at a roller rotational speed of 300 rpm and a feed rate of 800 kg/h. The power requirements and machine productivity increased with the increases of both the roller's rotational speed and the feed rate. The maximum power consumption value (3.51 kW) and maximum machine productivity value (880.45 kg/h) were recorded at a 300 rpm roller rotational speed and a 900 kg/h feed rate.
2. Because it recorded the highest threshing efficiency (97.64%) and the closest value of the lowest consumed specific energy (3.80 kW.h/ton), the operational condition of 300 rpm roller rotational speed with 800 kg/h feed rate was considered as the optimal operation condition.  
\begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**Source of Variation**} & \multirow{2}{*}{**df**} & \multicolumn{6}{c}{**F Value**} & \\ \cline{2-6}  & & **Damaged** & **Unthreshold** & **Threshing** & **Productivity** & **Power Re-** & **Specific** \\  & & **Seed** & **Seed** & **Efficiency** & & **quirement** & **Energy** \\ \hline Replication & 3 & & & & & & \\ Roller speed A & 3 & 189.192  & 218.947  & 99.361  & 21.734  & 142.358  & 15.666  \\ Feed rate B & 3 & 237.355  & 101.616  & 37.474  & 325.654  & 365.822  & 1.092  \\ A \(\times\) B & 9 & 1.407  & 1.877  & 1.625  & 0.032  & 1.26  & 0.414  \\ Error & 32 & & & & & & \\ \hline \hline \end{tabular}  
* **Significant at a level of 1%.
* Significant at a level of 5%.  
\end{table}
Table 1: Analysis of variance for the effectiveness of the study parameters on the performance of the sunflower threshing machine.  
Figure 10: The relationship between the observed and predicted threshing efficiencies (%).  
3. The equation of \(\eta=0.00015\big{(}\frac{v\Gamma}{\Gamma}\big{)}+(-753.08\big{(}\frac{F_{\rm B}T}{ \Gamma^{3}\rho}\big{)}^{2}+21.165\big{(}\frac{F_{\rm B}T}{\Gamma^{3}\rho}\big{)} +0.8124\) can be used to predict the threshing efficiency of the machine under examination with a correlation coefficient of 0.9309.
4. With better threshing efficiency, the newly designed sunflower threshing machine with the new add-on of a screw conveyer to avoid blockage problems, compared with the rice and soya bean threshing machines used in threshing sunflower crops, is considered suitable threshing equipment for farmers who have small- and medium-sized sunflower cultivation areas.  
Conceptualization, W.Z. and K.A.M.A.; methodology, K.A.M.A.; software, L.Y.; validation, W.Z., L.M. and K.A.M.A.; formal analysis, K.A.M.A.; investigation, W.Z.; resources, L.Y.; data curation, K.A.M.A.; writing--original draft preparation, K.A.M.A.; writing--review and editing, H.M.-T; visualization, L.M.; supervision, W.Z.; project administration, W.Z.; funding acquisition, W.Z. All authors have read and agreed to the published version of the manuscript.  
This research was funded by the National Key Research and Development, grant number 2016 YFD0702104.  
Not applicable.  
The data presented in this study are available on demand from the first author at ([EMAIL_ADDRESS]).  
The authors declare no conflict of interest.