## 3 Result
### Dependence of Exhaust Gas Temperature and Amount of Remaining PM  
Figure 9 illustrates the relationship between exhaust gas temperature and the remaining amount of PM. The conditions for this analysis include an activation energy of 100 kJ/mol; an exhaust flow rate (GA) of 30 g/s; and PM deposition amounts of 1 g, 10 g, 20 g, and 30 g, with temperatures set at 600, 650, 700, 750, and 800 \({}^{\circ}\)C. When the exhaust gas temperature is 600 \({}^{\circ}\)C, a substantial amount of PM remains trapped in the DPF. When 30 g of PM is initially deposited, the unburned PM amount is 10.29 g. Conversely, for an initial PM deposit of 1 g, only 0.35 g remains unburned. As the temperature increases, the extent of PM combustion also improves. For instance, at 650 \({}^{\circ}\)C, even when 30 g of PM is accumulated, the remaining unburned PM is reduced to 2.7 g.  
Figure 8: The right-hand side of (**a**–**d**) shows the activation energy on the vertical axis and the temperature of the exhaust gas on the horizontal axis. The remaining amount of PM according to each condition is shown in the field; when the remaining amount of PM is large, it is shown in red; when the remaining amount is small, it is in blue. The PM sedimentation quantities showing the relationships of the remaining amounts are (**a**,**b**,**c**,**d**) 1 g, 10 g, 20 g, and 30 g.  
Figure 10 depicts the relationship between pressure drop and elapsed time for PM deposition amounts of 1 g and 30 g. In the case where the PM deposit is 1 g, at an exhaust gas temperature of 600 \({}^{\circ}\)C, the unburned PM amount is 0.35 g, and the pressure drop is relatively low at 11.21 kPa. At 800 \({}^{\circ}\)C, despite the PM being almost entirely combusted, the pressure drop reaches 12.77 kPa, which can be attributed to thermal expansion effects. Maintaining lower exhaust gas temperatures can help regulate pressure drop, making low-temperature combustion a desirable approach.  
Figure 10: Pressure drop over time for PM deposition amounts of 1 g and 30 g. Dashed lines represent 1 g of PM, and solid lines indicate 30 g under different exhaust gas temperatures (600–800 \({}^{\circ}\)C).  
Figure 9: Relationship between exhaust gas temperature and the amount of remaining PM after 5400 s of regeneration. The red, blue, green, and yellow lines represent PM deposition amounts of 1 g, 10 g, 20 g, and 30 g, respectively. The results highlight the effect of temperature on PM oxidation efficiency.  
For a PM deposition amount of 30 g, a sharp rise in pressure drop occurs within the first 100 s of the regeneration process. At an exhaust temperature of 800 \({}^{\circ}\)C, the pressure drop reaches 107 kPa. After approximately 300 s, the pressure drop decreases and remains relatively stable until 5400 s. However, at 600 \({}^{\circ}\)C, the PM does not significantly decrease. Under this condition, both the remaining PM amount and the pressure drop are significantly high at 10.29 g and 33.12 kPa, respectively. When the exhaust temperature is raised to 800 \({}^{\circ}\)C, the residual PM is nearly eliminated, and the pressure drop reduces to 12.77 kPa. At 700 \({}^{\circ}\)C, even with 0.61 g of residual PM, the pressure drop remains low at 12.72 kPa. Furthermore, at 750 \({}^{\circ}\)C, the lowest pressure drop, 12.30 kPa, is observed with only 0.04 g of remaining PM.  
These findings indicate that, at lower exhaust gas temperatures, gas-phase reactions play a more dominant role compared to direct contact with the catalyst. Additionally, when the PM deposition is high, the pressure drop tends to rise irrespective of activation energy. To mitigate excessive pressure drops while handling large PM accumulations, an exhaust temperature range of approximately 700 to 750 \({}^{\circ}\)C is considered optimal.