Potentials to simplify the engine system using the alternative diesel fuels oxymethylene ether OME1 and OME3-6 on a heavy-duty engine

Polyoxymethylene dimethyl ether (POMDME or OME) is an emerging synthetic oxygenated fuel indicating high potential to meet the increasing challenges of CO2-neutrality and sustainability. The excellent ignitability and the sootless combustion of OME are ideal properties for its application in diesel engines. However, since other properties are fundamentally different compared to conventional diesel fuels, both its combustion behavior and necessary adaptations of standard diesel engine components and materials have to be studied in detail to realize all advantages of this fuel. In the present work, the combustion and emission characteristics have been compared between different neat OME fuels and a reference paraffinic diesel fuel (PDF) varying several operating parameters of a single cylinder heavy duty research engine. To evaluate the performance of unmodified nozzles, a variation of increasing load has been considered. Moreover, the NOx reducing potential of the sootless OME combustion has been investigated by increasing exhaust gas recirculation (EGR) up to stoichiometric conditions and evaluated considering thermal efficiency and different strategies for exhaust gas aftertreatment. Furthermore, it has been studied whether different OME fuels could realize a simplification of the fuel injection system by varying the rail pressure and injection pattern. Finally, in order to find an OME compatible sealing material the change in weight of several samples dipped in different OME fuels have been investigated. It is shown that ethylene propylene diene rubber (EPDM) is an alternative sealing material for an engine operation only with long-chained OME. In addition, it is proven that the particle emissions of the OME combustion are comparable to citys immission level regardless of significantly increased EGR rates or very low injection pressures. However, the emissions of methane rise drastically at stoichiometric conditions independent of molecules chain length of the used OME fuel. Moreover, it is demonstrated that an injection strategy using only a main injection could be possible, if the engine is operated with long-chained OME fuels.