Among the alternative Diesel fuels, Dimethylether (DME) is one of the most promising fuels to substitute Diesel. DME is produced from H2 and CO in a simple synthesis process. The resources needed for DME production are also readily available; such as coal, natural gas, coalbed methane, biomass,waste residual feedstock, etc.  DME is suitable fuel for compression ignition engines due to a relatively high Cetane number.However, DME has specific fuel properties that have some manageable negative effects for the fuel injection system which impacts the combustion process. To understand the injection process in greater detail, experiments on a transparent throttle were conducted and simulated by CFD to understand the onset of cavitation which limits the mass-flow rate. Thehigher vapour pressure and lower boiling point of DME leads to afaster vaporization than that which is achieved with diesel fuel. Due to DME's oxygen content and chemical structure of single C-bonds, a soot-free combustion is achievable. That emissions potential is demonstrated in this study on a single-cylinder engine where, EGR is applied for the lowest NOx levels close to the emissions target of 0.4 g/kWh.  However, such conditions suffer from an increase of CO emissions. A DME fuel injection system which is capable of producing injection pressure of up to 1000bar has been developed. Here the usage of elevated rail pressures up to 1000bar can enhance the mixing process of the injected DME fuel with the charged gas to reduce the CO emissions. First, the Diesel combustion is compared with the DME fuel in this paper. Second, four different nozzle configurations of straight and tapered holes are studied to identify the most suitable nozzle specification for DME from an emissions and fuel consumption point of view. The potential of emissions and fuel consumption reduction is estimated on a JE05 and WHSC simplified cycle to address various scenarios of NOx levels and consequences for the after-treatment.

Investigation of injection and combustion of dimethylether using high pressure injection system

248th National Meeting (2014)

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