The diesel injection process is one of the most critical aspects of diesel engine operation. Diesel injection pressures have been increased in recent years in order to reduce smoke levels and improve combustion. This has occurred together with multiple injections and a decoupling of the process from the engine rotation. In this paper, an overview of the UNSW program is given where the amplifying injector is described and some experimental results of engine tests referenced. Then, fundamental experiments carried out in a specially designed single shot apparatus are presented. They cover a pressure range providing velocities from low to high supersonic, the attenuation and the effect of different fuels including diesel oil, gasoline and bio-diesel. This paper examines even higher pressure injection possibilities from both a practical and fundamental viewpoint. The first of these describes an amplifying single fluid injector that has been tested in a single cylinder test engine to 230 MPa and on bench tests to 260 MPa. Even higher pressures are possible using it and these will give initial injection velocities that reach sonic velocity or more at diesel engine conditions. This has stimulated an accompanying fundamental research program that explores diesel injection well into the supersonic range. The shock wave development, pulsing and attenuation of the spray have been studied with diesel as well as other fuels. The basics of the fuel injection is explained and the effects on the surrounding air is shown. High pressure diesel injection has made a significant impact on reducing smoke and improving combustion. Flexible timing when the injection process is decoupled from the engine rotation can also reduce NOx. Injectors capable of even higher pressures are being developed and an important member of this group is the amplifying injector. The EDS-HEUI single fluid type being developed between the EDS (a company) and UNSW has great potential. Its test results to date are very promising. To further examine the influence of even higher injection pressures and hence greater jet velocities, fundamental studies have been carried out at UNSW in conjunction with Tohoku University, Japan and Ubon Ratchathani University, Thailand. These indicate that the shock wave system that develops as the jets move into the supersonic range influences the jet formation. As well as a direct modification due to the variation in pressure of the immediate, surrounding air, they increase the local air temperature due to the irreversibilities. Comparisons using four different fuels show that the fuel density and surface tension play the most significant role in the jet attenuation. In particular, the relatively low density gasoline has a much reduced penetration while the biodiesel has the greatest.


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    Title :

    Extreme pressure diesel injection


    Contributors:


    Publication date :

    2009


    Size :

    8 Seiten, 10 Bilder, 1 Tabelle, 6 Quellen



    Type of media :

    Conference paper


    Type of material :

    Print


    Language :

    English




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