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For years, diesel Common Rail Systems (CRS) have utilized 2-way valves and orifices for needle control in the injectors. Although this approach has been quite successful, challenges to improving injection performance still remain. The design of a reliable 3-way high pressure control valve is challenging, but its implementation for needle control could represent a natural path to further improvements in injection performance. The rational is that a 3-way valve would provide more independent control of needle opening and closing rates than the 2-way design. An efficient way of comparing 2-way and 3-way needle control methods is through a numerical simulation study. To that end, numerical simulation models of injectors with both needle control concepts were built.

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.

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.