In most cases hydrogen internal combustion engines so far have been designed as naturally aspirated engines using ambient external mixture formation (PFI). However, the applicability of this concept is limited: Phenomena such as pre-ignition, knocking and the air-displacement effect of hydrogen result in low power output and low volumetric efficiency. Advanced hydrogen injection techniques such as high pressure direct injection (DI) or cryogenic port fuel injection (cryo PFI) may overcome these disadvantages. In the present work the potentials of hydrogen high pressure direct injection are outlined and compared to PFI with ambient hydrogen. Various test series and simulations have shown the high potential of the ICE employing hydrogen direct injection. Hydrogen high-pressure direct injection systems involve various engine and injection parameters which may be applied taking influence on the combustion process in a significant way. The direct injection of hydrogen avoids air-displacement as present in conjunction with external mixture formation due to the low density of hydrogen. For DI, the achievable full load IMEP is about 45 % higher with respect to PFI. Idling operation with an excellent cycle-to- cycle stability at high injection pressures is possible through optimised charge stratification. Injecting small amounts of fuel mass requires an injector which allows a part lift of the injector needle or a stable ballistic operation mode. In addition, it could be demonstrated that the high potential of direct injection, indicated by a theoretically increased mixture calorific value in comparison to PFI, may be realised in the real engine. In aspirated mode, an increase in full load IMEP of 45 % with respect to ambient port fuel injection was observed using direct injection. Additionally, the area of maximum efficiency (etai>=42 %) was significantly increased. The power output at epsilon = 13.5 in naturally aspirated operation is higher than at lower compression ratios. A rise in efficiency also could be shown with optimised nozzle geometries due to a reduction of wall heat losses caused by improved fuel allocation in the stratified case. Supercharged investigations have shown a high potential in terms of power output, a specific power density close to 100 kW per litre displacement has been reached. However, an increased knocking tendency for higher compression ratios is noticed, which gives rise for an improvement of combustion chamber design and gas exchange in order to avoid combustion anomalies.


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    Title :

    Optimisation of a hydrogen internal combustion engine with inner mixture formation


    Additional title:

    Optimierung eines Wasserstoff-Verbrennungsmotors mit innerer Gemischbildung


    Contributors:
    Grabner, P. (author) / Eichlseder, H. (author) / Gerbig, F. (author) / Gerke, U. (author)


    Publication date :

    2006


    Size :

    12 Seiten, 15 Bilder, 2 Tabellen, 7 Quellen



    Type of media :

    Conference paper


    Type of material :

    Print


    Language :

    English





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