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DiMethyl Ether (DME) has been shown to be a very promising alternative fuel, which offers low emissions and good economy when directly injected into the cylinder of diesel cycle engines. However, as it is a liquified gas, it poses special demands in terms of storage and handling. Over the last few years, AVL has been developing fuel injection and handling systems for DME so that its full potential can be realised. This paper describes the choice of fuel injection system, describes its function and control as well as present test results. In addition, the future outlook for DME as a fuel in transportation will be discussed.

DiMethyl Ether (DME) has been shown to be a very attractive fuel for low emission direct injection compression ignition (DICI) engines. It combines the advantages of the high efficiencies of diesel cycle engines with soot free combustion. However, its greatest drawback is the need to develop new fuel injection and handling systems. Previous approaches have been common rail type injection systems which have shown great potential in reducing harmful exhaust emissions and achieving good engine performance and efficiency due to good control of both the fuel injection characteristics and temperature. The concept also has proven benefits with respect to convenient and safe fuel handling. The logical evolution of this concept simplifies the fuel system and avoids special components for DME handling such as high pressure rail pumps while retaining all the benefits of the common rail principle.

Over the last few years there has been much interest in DiMethyl Ether (DME) as an alternative fuel for diesel cycle engines. It combines the advantages of a high cetane number with soot free combustion, which makes it eminently suitable for compression ignition engines. However, due to the fact that it is a gas under ambient conditions, it requires special fuel handling and a specially designed fuel injection system, which until recently, was not available. The use of the digital hydraulic operating system (DHOS), combined with a fuel handling system designed to cope with the properties of DME, enables the fuel to be safely and conveniently handled, In addition, the flexibility of the injection system enables injection pressures to be chosen according to the needs of the combustion.

The paper describes basic investigations towards identifying optimum specifications of fuel injection and combustion system parameters for a new alternative fuel, Dimethylether (DME), allowing liquid direct injection, compression ignition and smokeless combustion. Special emphasis is drawn on fuel injection equipment (FIE) parameter optimization using new development tools such as simulation techniques of the fuel system hydraulics and numerical identification methods to determine sofar unknown fuel data and flow phenomena of the new alternative fuel. Combustion system parameters are analyzed on a single cylinder test engine with respect to efficiency, gaseous emissions, and noise. Due to the particular properties of the fuel the engine parameter optimization was concentrated on new directions of system development thus allowing new solutions for FIE and combustion system, as described in this paper.