E-fuels – a central module for future engine design?

Abstract

The ongoing development of the future spark-ignition internal combustion engine mainly focusses on a more efficient combustion process in combination with a further reduction of pollutant emissions to meet worldwide standards and customer demands. Conceivable measures of engine design are mainly associated with CO₂ emissions, costs and the complexity of the measures. A supplement to engine design measures is the use of e-fuels. With e-fuels it is possible to optimize fuel properties for increased engine efficiency and reduced raw emissions across the entire engine map and improve CO₂ reduction regarding a ‘well-to-wheel’ system.

Driving with high compression ratio and at lambda = 1 across a wide area in the engine map calls for technological measures that prevent knocking and hence avoid the need to enrich the mixture to protect engine components. The effective mechanism of several technologies is to reduce knock tendency, which moves the Mass Fuel Burned (MFB) towards ‘early’, where combustion is more efficient, thus reducing the exhaust temperature. Other approaches are the implementation of high temperature materials for the cylinder head and the turbocharger or faster burning rate due to higher charge motion (tumble) to lower both combustion and exhaust gas temperatures. An alternative to the aforementioned technologies is the use of a higher-octane fuel. The lower knock tendency allows advanced spark-ignition timing or a higher compression ratio for improved efficiency. This reduces the exhaust gas temperature and the need to enrich the mixture to protect components.