# Oxygenated Diesel Fuels and Their Effect on PM Emissions
## 4 Tests Results and Discussion
It can be seen that at the 10% content, there are no significant differences in reducing PM emissions for glycol ethers and carbonates that were so characteristic at the lower content (5%). Thus, with a content of 10%, the effectiveness of the best components from all tested chemical groups was similar, i.e., PM reduction by 30-40%. The last part of the authors' research concerned the influence of the test cycle conditions on the obtained effects in PM emission reduction. Figure 7 shows a comparison of the impact on PM emissions of fuels containing 10% of individual oxygenated compounds obtained under the conditions of the NEDC and FTP-75 (US Environmental Protection Agency Federal Test Procedure) test cycles. The American cycle (FTP-75) is a more dynamic, non-stationary cycle, while in the European cycle there is a higher maximum speed. Ultimately, based on the measurement results, it can be concluded that, for the same fuels, a greater reduction of PM emissions occurs under the NEDC cycle conditions. The use of glycol ethers as fuel components for diesel engines also in studies presented by other authors led to a reduction in the emission of particulate matter (soot). In Zannis  
Figure 6: Reduction of PM emissions as a function of type and content of oxygenated compound in relation to fueling with conventional diesel fuel. Figure 7: Percentage changes in PM emissions over the NEDC and FTP-75 cycles when the test car’s fuels contained 10% of various oxygenated compounds compared to running on conventional diesel fuel. et al. [61], soot emissions from a single-cylinder direct-injection diesel engine using city diesel fuel and two blends of this fuel and glycol ethers were tested. Each blend contained diethylene glycol dimethyl ether (so-called diglyme) and diethylene glycol dibutyl ether (so-called butyl diglyme) in approximately equal proportions. The first blend (named GLY10) contained about 10% glymes and the second (named GLY30) about 30%. This corresponded to 3% and 9% \(m/m\) oxygen content in the fuel mixture, respectively. The soot emissions were measured under conditions of constant speed (2500 rpm) and variable load. The emission of soot for the fuel containing 3% oxygen was higher than for neat diesel fuel; however, for the fuel containing 9% oxygen, it decreased on average by about 20%. It is worth noting that GLY 30 fuel had a very high cetane number (73). The study by [PERSON] et al. [62] on diesel passenger car emissions over the NEDC showed a moderate effectiveness of glycol ethers in reducing PM emissions compared to other oxygenates. [PERSON] et al. [63] also showed the PM reducing effect of glycol ethers under the conditions of dynamic tests on a chassis dynamometer. The beneficial effect of glycol ethers on PM emissions is also described in [64]. [PERSON] and [PERSON] [60] also showed that glycol ethers reduce PM emissions. In addition, it has been found that oxygenates mainly reduce the insoluble fraction (soot) while the soluble organic fraction (SOF) decreases slightly. The high efficiency of diethylene glycol dimethyl ether in reducing PM emissions was demonstrated in [65]. At the brake mean effective pressure (BMEP) of 0.65 MPa, the 5% addition reduced PM emission by nearly a half. With the addition of 25%, the reduction in PM emissions was nearly four times. Moreover, it was noticed that with an increase in the content of the oxygenated compound, the SOF fraction in the emitted PM increased and the soot fraction decreased. The effective reduction of PM emissions from heavy-duty diesel engines using diethylene glycol dimethyl ether is described in [66]. The efficiency increased with the increase of the oxygen content in the fuel and was slightly higher in hot start-up conditions than in a cold start-up.