## 4 Conclusions  
The findings obtained from the experiments and analyses are presented below:  
* Through the conducted analyses, it was determined that at the end of 1500 cycles, the highest temperature was observed in the FC piston model due to the complete coating  
Figure 16: Cylinder internal temperature distribution according to different piston models and crank angles.  
Figure 17: The effect of TBC on efficiency.  
of the entire surface. The temperature values for the partially coated piston models and the uncoated piston were found to be close to each other.
* In the conducted transient thermal analysis, the highest heat flux value was determined at the bottom of the piston crown in the combustion chamber for all four piston models. The lowest heat flux value was observed in the FC piston due to the effect of the thermal barrier coating, and the highest heat flux value was observed in the NC piston.
* An increase in the surface area of the coatings resulted in an increase in the cylinder pressure. The highest cylinder pressure value was observed in the piston model with full surface coating. The cylinder pressure values for the partial coating models were determined to be close to each other.
* The highest cylinder pressure and temperature values were observed for the piston model with the full surface coating, while the lowest values were observed with the uncoated piston model. The cylinder temperature and pressure values for the PC-5 and PC-10 partial coating models were determined to be close to each other.
* The lowest HRR rate was observed with the FC piston model. The fully coated piston model exhibited higher internal temperatures, which led to early combustion and a shorter ignition delay compared to the other piston models. The temperature distribution in the combustion chamber differed for the fully and partially coated piston models compared to the uncoated piston model.
* For the four piston models, the NOx value was found to be the highest with the fully coated piston model based on experimental and simulation results. As the surface area of the coatings increased, an increase in NOx emissions and a decrease in carbon monoxide (CO) and hydrocarbon (HC) emissions were observed.
* The highest combustion efficiency was observed with the FC piston model, while the lowest combustion efficiency was observed with the NC piston model. An increase in combustion efficiency was observed as the surface area of the coatings increased. The coating's effect resulted in a decrease in the amount of heat loss and an increase in the internal temperature of the piston, which improved the combustion process.  
Conceptualization, H.T. and H.A.; Methodology, H.T. and H.A.; Software, H.T.; Investigation, H.T. and H.A.; Writing--original draft preparation, H.T., H.A. and M.Q.B.; Writing--review and editing, H.T., H.A. and M.Q.B.; Supervision, M.Q.B. and H.A.; Project administration, H.A. All authors have read and agreed to the published version of the manuscript.  
This research was funded by the Scientific and Technological Research Council of Turkey (TUBITAK) grant number 1059B142000589.  
Data Availability Statement: Data will be made available on request.  
[PERSON] acknowledges financial support from the Scientific and Technological Research Council of Turkey (TUBITAK) 2214-A-International Research Fellowship Programme for PhD Students (app. no: 1059B142000589) during her visit to the Department of mechanical science and engineering at the University of Illinois.  
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.