The aim of the project presented here is the development and research of a "dual-fuel" engine that can be operated completely with so-called e-fuels.  Gas (preferably synthetically produced methane, alternatively natural gas with a high methane content) is to be used as the main fuel. A small amount of a second, liquid fuel is used to trigger the ignition, for which oxymethylene ether (OME3-5) is used here as a synthetically produced fuel. Since both fuels can be produced from renewable electric power, a quasi-CO2-neutral operation is possible. In the project, the achievable efficiencies as well as the exhaust emissions of the new aggregate will be investigated and optimised. In addition, a variable valve drive developed at the Institute of Vehicle Propulsion Systems will be used, which should enable a further reduction in exhaust emissions through targeted residual gas control. The result should be a low-emission combustion process with regard to both CO2 and exhaust emissions.

Shown on the left is a natural gas engine with spark-ignition combustion. The homogeneous stoichiometric mixture is ignited by a spark plug. The diesel combustion process is shown on the right. Ignition takes place as autoignition at the rim of the injection spray - the mixture is inhomogeneous. The dual-fuel combustion process (see centre) uses renewable methane as the main fuel and oxymethylene ether (OME) as the ignition source. Ignition also takes place as self-ignition at the rim of the (OME) injection spray, which subsequently also ignites the methane-air mixture. Due to the special properties of the fuels and the strong leaning of the homogeneous mixture, combustion is particularly low in emissions and at the same time efficient.

The basic diesel engine is modified to methane gas operation by an intake manifold injection and operated with a CNG-OME dual-fuel concept as described above. The tests are carried out on a modified 4.5 litre four-cylinder engine from John Deere. The engine was equipped with a mechanical fully variable valve train with two overhead camshafts.