Takamasa Yokota

Potential of Dimethylether as an alternative Diesel fuel for a CO 2 sustainable powertrain solution

Worldwide, combustion engines will remain as major power unit for vehicle propulsion in long-term. Consequently, immediate measures are claimed to reduce the current CO2 production from combustion engines which are accomplished by three approaches: (1) an increase of the thermal efficiency, (2) the application of fuels with low carbon content and (3) the production of fuels from renewable feedstocks. The first aspect clearly emphasizes compression ignition (CI) engines, the second aspect draws the attention to hydrogen and single C-bonded fuels and the third aspect has initiated sensitive discussions about renewable resources which lead to the commitments of first/ second/ third generation biofuels. In this context, the use of Ethers as neat or blended fuels for combustion engines has been discussed for more than 20 years. Among these, the simplest compound, Dimethylether CH3-O-CH3 (DME), has an exceptional position as a neat fuel for compression ignition (CI) engines due to its excellent ignition and combustion properties which have been well investigated published by many authors.

An Investigation of Flow in Nozzle Hole of Dimethyl Ether

For over twenty years, DME has shown itself to be a most promising fuel for diesel combustion. DME is produced by simple synthesis of such common sources as coal, natural gas, biomass, and waste feedstock. DME is a flammable, thermally-stable liquid similar to liquefied petroleum gas (LPG) and can be handled like LPG. However, the physical properties of DME such as its low viscosity, lubricity and bulk modulus have negative effects for the fuel injection system, which have both limited the achievable injection pressures to about 500 bar and DMEs introduction into the market. To overcome some of these effects, a common rail fuel injection system was adapted to operate with DME and produce injection pressures of up to 1000 bar. To understand the effect of the high injection pressure, tests were carried out using 2D optically accessed nozzles. This allowed the impact of the high vapour pressure of DME on the onset of cavitation in the nozzle hole to be assessed and improve the flow characteristics.