*3.1. Ignition Delay Verification of DX-NB-NOx Skeleton Mechanism*

The ignition delay data come from the simulation results of fuel in CHEMKIN closed internal combustion on engine simulator under different equivalence ratios. Figures 1–3 show the comparison of n-dodecane ignition delay time between the mixed fuel skeleton mechanism and the experimental value [42]. It can be seen that the study selects three different equivalence ratios (0.5, 1.0 and 1.5) for comparison at 8 atm and 15 atm respectively. The simulation results are in good agreement with the experimental values in the hightemperature stage, and there are some differences in the low-temperature stage. This is because the experimental data of fuel ignition delay are obtained from the shock tube experiment, while the simulated ignition delay results come from diesel engine combustion. There are some differences in the working mode between two styles. Therefore, there is a certain difference between the diesel engine combustion simulation results and the shock tube experimental data. The overall trend of two modes is consistent, and the error is within a reasonable range. So, the reliability of the combustion simulation of n-dodecane in the newly constructed combustion reaction mechanism can be guaranteed.

**Figure 1.** (**a**) Comparison of simulated and experimental ignition delay time of n-dodecane at Φ = 0.5, 8 atm; (**b**) Comparison of simulated and experimental ignition delay time of n-dodecane at Φ = 0.5, 15 atm.

**Figure 2.** (**a**) Comparison of simulated and experimental ignition delay time of n-dodecane at Φ = 1.0, 8 atm; (**b**) Comparison of simulated and experimental ignition delay time of n-dodecane at Φ = 1.0, 15 atm.

**Figure 3.** (**a**) Comparison of simulated and experimental ignition delay time of n-dodecane at Φ = 1.5, 8 atm; (**b**) Comparison of simulated and experimental ignition delay time of n-dodecane at Φ = 1.5, 15 atm.

Figure 4 shows the comparison of n-butanol ignition delay time between the newly constructed fuel mechanism and the experimental value [43]. It can be seen that the ignition delay times of n-butanol at three different pressures of 1.5, 3, and 42 atm are compared with the experimental values at the equivalent ratio of 1.0. The results show that the ignition delay time of n-butanol in the newly constructed mechanism was consistent with the experimental value, which ensured the reliability of the combustion simulation of n-butanol in the newly constructed combustion reaction mechanism.

**Figure 4.** (**a**) Comparison of simulated and experimental ignition delay time of n-butanol at Φ = 1.0, 1.5 atm; (**b**) Comparison of simulated and experimental ignition delay time of n-butanol at Φ = 1.0, 3 atm; (**c**) Comparison of simulated and experimental ignition delay time of n-butanol at Φ = 1.0, 42 atm.
