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<div class="section abstract"><div class="htmlview paragraph">In this study a mixture of dimethyl carbonate (DMC) and methyl formate (MeFo) was used as a synthetic gasoline replacement. These synthetic fuels offer CO₂-neutral mobility if the fuels are produced in a closed CO₂-cycle and they reduce harmful emissions like particulates and NO_X. For base potential investigations, a single-cylinder research engine (SCE) was used. An in-depth analysis of real driving cycles in a series 4-cylinder engine (4CE) confirmed the high potential for emission reduction as well as efficiency benefits.</div><div class="htmlview paragraph">Beside the benefit of lower exhaust emissions, especially NO_X and particle number (PN) emissions, some additional potential was observed in the SCE. During a start of injection (SOI) variation it could be detected that a late SOI of DMC/MeFo has less influence on combustion stability and ignitability. With this widened range for the SOI the engine application can be improved for example by catalyst heating or stratified mode. Furthermore, until λ = 0.8 no significant PN increase was noted in contrast to gasoline. This is also a positive capability for combustion modes with local rich areas in the mixture. From the experience of previous investigations, the synthetic fuels’ high knock-resistance potential enabled an increase in the compression ratio (CR) from epsilon ~ 11 to ~ 15 to enhance the indicated efficiency.</div><div class="htmlview paragraph">In general, in the 4CE the positive effects of DMC/MeFo on harmful emissions were confirmed. Even in the series configuration, the brake efficiency increased by 16 % at maximum low-end torque compared to gasoline. The increased in-cylinder cooling and the lower laminar flame temperature by the DMC/MeFo implies lower maximum exhaust temperatures. Therefore, a stoichiometric mixture could be used over the whole engine map. During the legislative driving cycles, for example WLTC, the PN, NO_X, CO and CH₄ emissions decreased by 50 % or more.</div><div class="htmlview paragraph">In summary, oxygenated fuel opens great opportunities for replacing fossil fuel in gasoline engine applications.</div></div>

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<div class="section abstract"><div class="htmlview paragraph">In the near future, pollutant and GHG emission regulations in the transport sector will become increasingly stringent. For this reason, there are many studies in the field of internal combustion research that investigate alternative fuels, one example being oxygenated fuels. Additionally, the design of engine components needs to be optimized to improve the thresholds of clean combustion and thus reduce particulates. Simulations based on PRiME 3D® for dynamic behaviors inside the piston ring group provide a guideline for experimental investigation. Gas flows into the combustion chamber are controlled by adjusting the piston ring design. A direct comparison of regular and synthetic fuels enables to separate the emissions caused by oil and fuel. This study employed a mixture of dimethyl carbonate (DMC) and methyl formate (MeFo). These two components have no C-C bonds, and the mixture displayed extremely good performance in terms of the particle number (PN) emissions on an ambient level published in previous studies. This fuel property is employed in this study to identify oil induced, engine-out PN-emissions, while the combustion process remains almost identical to that of conventional gasoline. The PN-emissions are measured and subdivided into two ranges: larger than 10 nm and larger than 23 nm.</div><div class="htmlview paragraph">It was demonstrated that merely changing the piston ring design has an impact on raw PN engine emissions and gas flow behavior in the piston assembly. An increase in PN-emissions and lower blow-by level could only be detected by changing the piston ring design. With reduced, predicted fluid flows into the combustion chamber, lower VOC emissions could be observed during motored runs. The adaptations in the tested piston ring design demonstrate that it is possible to improve particulate emissions by modifying the piston ring group.</div></div>

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