## 3 Results and Discussions
### Gaseous Emissions
The light-saturated HC (methane and ethane) and the unsaturated HC (acetylene, ethylene, and propylene) species, shown in Figure 4, have been separately analyzed from the heavy HC in order to provide an in-depth analysis of the THC. The heavy hydrocarbons solely correspond to approximately 88%, 85%, and 78% of THC for diesel, E15B35D50, and E15B35 FTD50, respectively. The decrease in the heavy HC (seen in Figure 3) follows the same trend for the blends as with the THC. On the other hand, higher emissions of the light HC species (saturated and unsaturated) were measured for the E15B35 FTD50 and E15B35D50 as compared to diesel fuel. This result could be attributed to the thermal decomposition of the alcohol component of the blends into shorter molecules of HC (i.e., light HC species) and CO, as discussed by [PERSON] et al. [28]. Nevertheless, the combustion of diesel is likely to produce heavier HC, which supports the reduction of the THC for the blends. It was observed that the NO emissions have decreased around 2% and 8% respectively for E15B35 FTD50 and E15B35D50 blends in comparison to diesel fuel. However, the NO\({}_{2}\) emissions increased for these blends, which resulted in a similar or slight increase in the NO\({}_{\text{x}}\). The NO\({}_{\text{x}}\) emissions are directly dependent on high combustion temperatures, and thus ethanol could reduce the NO\({}_{\text{x}}\) formation as a result of its high heat of evaporation  
Figure 4: HC speciation for diesel, E15B35D50, and E15B35 FTD50. that reduces the in-cylinder temperatures. Besides, it has been previously reported by [PERSON] et al. [60] that F-T diesel decreases NOx emissions in comparison with diesel fuel. However, the present work results have shown a slight increase in NOx emissions (4-5%) with the use of the E15B35 FTD50 blend in comparison with diesel and E15B35D50 blend (Figure 3). This is probably due to the biodiesel addition, which increased the oxygen content of the blend and may contribute to increasing the combustion temperature and thereby providing additional oxygen for NOx formation. Similar results with oxygenated biofuels (ethanol and biodiesel) have been reported in the literature [61; 62]. In addition to the oxygen content of the blend, the lower cetane number of the ethanol leads to an increase in the ignition delay, which increases the heat release rate during the combustion process because of the higher fuel amount in the combustion chamber [63]. Hence the NOx emission increases, as previously discussed by [PERSON] and [PERSON] [11]. The N2O, which is not usually taken into account in the NOx emissions, was also measured. The emissions of N2O have decreased around 13% for both E15B35 FTD50 and E15B35D50 blends when compared to diesel fuel. It is known that N2O is a harmful greenhouse gas promoter and also one of those responsible for ozone destruction [64]. The exhaust emissions result also includes NH3, another nitrogen compound. It was observed that the NH3 emissions reduced nearly 60% in the combustion of E15B35 FTD60 and E15B35D50 with respect to diesel. NH3 is a precursor to secondary inorganic PM formation and secondary inorganic aerosol (i.e., NH4 NO3, ammonium nitrate, and, (NH4)2 SO4, ammonia sulfate) [65].