# Oxygenated Diesel Fuels and Their Effect on PM Emissions
## 4 Tests Results and Discussion  
The authors' research on the influence of oxygenated compounds in fuel on PM emission from a diesel passenger car was implemented in several stages. Initial tests were performed at the content of 5% \(v/v\) of each of the oxygenated compounds [56]. The test results regarding changes in PM emissions are shown in Figure 4. The results regarding changes in gaseous exhaust components (i.e., CO, HC and NO\({}_{\text{x}}\)) are presented in Appendix A (Figures 11-13). The symbol OC stands for oxygenated compound, then its number (according to Table 1) and its percentage in the fuel are shown. The presented results show that all tested oxygenated compounds, used as components of diesel fuel in the concentration of 5% \(v/v\), lead to reductions in PM emissions. Omitting component number 12, i.e., n-butanol, it should be noted that the 5% addition of oxygenated compounds caused a significant change in PM emissions. It is easy to notice that for the same component  
Figure 3: Chassis dynamometer and schematic of exhaust emissions measurement system. \begin{table}
\begin{tabular}{c c} \hline \hline
**Vehicle Type** & **Passenger Car** \\ \hline Weight & 950 kg \\ \hline Engine type & Diesel, 4-cylinder in-line \\ \hline Engine capacity & 1.3 dm\({}^{3}\) \\ \hline Maximum power & 51 kW @ 4000 rpm \\ \hline Maximum torque & 145 Nm @ 1500 rpm \\ \hline Combustion type & Direct injection Common Rail, turbocharged (intercooled) \\ \hline Emission control & Oxidation catalyst, Exhaust gas recirculation \\ \hline Emissions level & Euro 4 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Characteristics of the test vehicle. content, the greatest reduction of PM emission was achieved for carbonates (about 30%). For glycol ethers, it was on average 15%, and for maleates about 20%. In the literature on the influence of oxygenated compounds on PM emissions from diesel engines, there are divergent opinions as to whether the reduction of PM emissions depends only on the amount of oxygen introduced into the fuel [24; 26; 57; 58], or also on the type of oxygenated compound which is used for this [28; 47; 59; 60]. This divergence of opinions is also due to the fact that only a few studies present the results of testing a wide range of oxygen compounds under identical measurement conditions. The comparison of the changes in PM emissions over the NEDC cycle presented in Figure 4 to the oxygen content in individual oxygenated fuels indicates that 1% of oxygen contained in the fuel most often reduces PM emissions (over NEDC) by 7-10% (Figure 5). It can therefore be concluded that the oxygen content in the fuel is a very important parameter, though not the only one, in determining the level of PM emission reduction. Further research concerned the influence of the oxygenated compound content on the change in PM emissions. For these studies, components from the group of ether glycols, maleates and carbonates were selected. The tests were performed under the conditions of the NEDC and with the same vehicle as before, but the concentrations of oxygenated compounds in fuel were increased to 10% \(v/v\). The results presented in Figure 6 show that  
Figure 4: Percentage changes of PM emissions over the NEDC from a test car with fuels containing individual oxygenates at a concentration of 5% \(v/v\) compared to running on conventional diesel fuel. Figure 5: Unit effect of oxygenate and oxygen content in fuel on PM emissions over the NEDC from a test car with fuels containing individual oxygenates at a concentration of 5% \(v/v\) compared to running on conventional diesel fuel. increasing oxygenates' content brings beneficial results, albeit to a different extent. For glycol ethers, doubling the fuel content also doubled the decrease in PM emissions. For maleate and carbonate, the benefit of increasing content was significantly smaller.