## 3 Results and Discussion
### Finite Element Analysis Results
Figure 6: (**a**) Temperature distribution of NC assembly model, (**b**) FC assembly model, (**c**) PC-5 assembly model, and (**d**) PC-10 assembly model. Figure 7b shows fluctuations in the piston surface temperature as a function of incylinder temperature at the end of 0.08 s. In each cycle, there was an increase and decrease in temperature depending on the increase and decrease in the hA and TA values of the gas acting on the upper surface. While the maximum temperature was observed in the FC piston, the difference in the temperature change on the piston surface for each cycle was greater than for the other pistons. Similar trends in maximum temperature change were observed for the PC-5 and PC-10 pistons. Minimum temperature variation was observed on the NC piston for each cycle. Fluctuations in the piston surface temperature relative to the in-cylinder temperature between 59.88 and 60 s are given Figure 7c. The temperature rise for each cycle in the pistons decreased with time because the surface temperatures of the pistons increased as the number of cycles increased. In Figure 8b, the transient temperature change in the normalized distance on the coating surface is given for the FC piston. At 0.44 normalized distance, the temperature at the piston crown was 574.31 \({}^{\circ}\)C at 60 s, 554.33 \({}^{\circ}\)C at 45 s, 525.68 \({}^{\circ}\)C at 30 s, and 488.55 \({}^{\circ}\)C at 15 s. At 0.44 normalized distance, the temperature at the piston crown was 511.93 \({}^{\circ}\)C at 60 s, 488.54 \({}^{\circ}\)C at 45 s, 453.94 \({}^{\circ}\)C at 30 s, and 413.32 \({}^{\circ}\)C at 15 s in the lining layer of the FC piston. In Figure 8d, the transient temperature change in the normalized distance on the crown of the FC piston surface is given. At 0.44 normalized distance, the temperature at the piston crown was 512.26 \({}^{\circ}\)C at 60 s, 485.85 \({}^{\circ}\)C at 45 s, 454.23 \({}^{\circ}\)C at 30 s, and 413.59 \({}^{\circ}\)C at 15 s. Along the path normalized from 1 to 2, the temperature values for the lining and the crown layer were determined to be very close to each other at 15, 30, 45, and 60 s. As in this study, [PERSON] et al. in their study [19] determined that the temperature distribution curves at the normalized distance on the lining layer and the piston upper surface were very close to each other, and the temperature values in the temperature distribution curve at the normalized distance on the coating surface were higher. Figure 7: **(a)** Temperature distribution of NC, FC, PC-5, and PC-10 pistons for 60 s. **(b)** Temperature distribution in the range of 59.88 to 60 s; **(c)** temperature distribution for the first 0.08 s; **(d)** temperature distribution for the first 5 s.  
In Figure 9a, the change in total heat fluxes for NC, FC, PC-5, and PC-10 are given. After 1500 cycles, the highest heat flux in the NC piston was 0.71462 W/mm\({}^{2}\) at the bottom of the piston crown; in the FC piston, 0.65372 W/mm\({}^{2}\) at the bottom of the piston crown; and in the in PC-5 piston, 0.70343 W/mm\({}^{2}\) at the bottom of the piston crown. The highest heat flux in the PC-10 piston was 0.73154 W/mm\({}^{2}\) in the lower regions of the piston crown inside the combustion chamber. When 1500 cycles were completed, the highest heat flux values for the four piston models were determined in the same region. Figure 8: (**a**) Temperature distribution of FC piston layers along the path from 1 to 2: (**b**) coated surfaces, (**c**) bond-coated surfaces, (**d**) substrate surfaces. Figure 9: (**a**) Total heat flux change; (**b**) total heat flux change for the first cycle; (**c**) total heat flux change for the last two cycles. In Figure 9b, the change in total heat flux for the first cycle in 0.04 s is given. The highest heat flux in the first cycle was 0.9496 W/mm\({}^{2}\) in the NC piston, 0.7563 W/mm\({}^{2}\) in the FC piston, 2.8073 W/mm\({}^{2}\) in the PC-5 piston, and 3.9357 W/mm\({}^{2}\) in the PC-10 piston. The driving force in the transfer of heat is the temperature difference.