## 3 Results and Discussion
### Validation of the E10 Simulations
Nonetheless, this does not affect the validity of the comparison. In the following, the HC, CO, CO\({}_{2}\), and NO\({}_{x}\) pollutant emissions are compared. Figure 4 illustrates the comparison of HC emissions between the E10 simulations and the test bench measurements. It is clearly visible that the discrepancies are extremely large and not consistent at all. The possible reasons for this are as follows: the simulation overpredicts the combustion efficiency, which results in significantly lower HC emissions in the simulation; however, in this case, the cylinder pressure should also be noticeably higher compared to the test bench measurements, which is not the case. The second possible reason could be the difference in the H/C ratio between the real and the surrogate fuel, but this 2%  
Figure 2: Comparison of simulated cylinder pressure against experimental data with E10 fuel at operating point 1 (**a**), operating point 2 (**b**), operating point 3 (**c**), and operating point 4 (**d**); dashed line represents difference between experimental and numerical values. difference should not cause such a large discrepancy in emissions. Additionally, these large deviations may also result from the reaction mechanism used in the simulations not being sufficiently detailed, which leads to an inadequate modeling of HC emissions. Another possible reason for the discrepancies is that the experminetal and simulation HC calculation methods differ. Additionally, since the amount of injected fuel was determined through simulation, there may also be slight differences in that, which could cause variations in HC emissions However, it was not possible to examine the impact of these methodological differences during the course of the study. Figure 5 compares CO emissions between the simulation and the test bench measurements. In this case, significant discrepancies are clearly visible, and except for the last operating point, the CO values in the simulation are higher at every other operating point. The reason for this is that CO emissions are closely linked to HC emissions. Since HC emissions are much lower in the simulation, it can be inferred that the differences in HC emissions will manifest oppositely in CO emissions. An exception to this is the high-load OP4 operating point, where this relationship does not hold. Figure 4: Comparison of simulated HC emissions against experimental data with E10 fuel. Figure 3: Comparison of simulated IMEP against experimental data with E10 fuel. Regarding CO2 emissions, compared to the previous two components, the magnitude of the discrepancies is much smaller, and the direction of the deviations is consistent across all operating points. The simulation underpredicts the values as shown in Figure 6, which the higher CO emissions in the simulation can explain. Figure 7 illustrates the comparison of NOx emissions. In this case, no clear trend can be observed in the pattern of the discrepancies. Based on maximum cylinder pressure, OP1 and OP3 were the closest to the test bench measurements, which is also reflected in the NOx emissions, as temperature has a strong influence on their formation. The largest deviation in maximum cylinder pressure occurred at OP2, which is similarly evident in the NOx emissions. Except for OP2, there is a good correlation between the simulation and the measurements. Figure 5: Comparison of simulated CO emissions against experimental data with E10 fuel. Figure 6: Comparison of simulated CO2 emissions against experimental data with E10 fuel.