A range of ULG/ethanol blends (EO to E85) have been tested under cold (20°C) and warm (80°C) coolant conditions. Spray and combustion characteristics have been investigated using high-speed imaging and the variability of pre-flame HC concentration at the spark plug was also measured using a Cambustion fFID. The main findings are: (1) An increase in ethanol addition led to an increase in both particle number and mass, due to the deleterious effect of ethanol on spray break-up and the evaporation efficiency as a result of its high vaporization enthalpy and low energy density. This trend is more pronounced in a cold engine than in a warm one. The ratios between maximum and minimum values in terms of particulate total number and mass are 16 and 11 under cold conditions and 7 and 8 under warm conditions. (2) Cold fuel spray plumes are more clearly defined and last longer than warm plumes for all the test fuels. Integrated pixel values of the plumes on each image have been calculated to indicate the amount of fuel present in the cylinder at a particular crank angle. As the ethanol content increases, the integrated pixel values remain high for longer (by about 50% in the cold engine) which implies that spray breaks-up and evaporates to a lesser extent for fuels with high ethanol proportions than with low ethanol proportions. (3) The IMEP and MFB durations exhibited less variability for a warm engine than a cold engine for all the test fuels. The warm engine also produced a higher maximum in-cylinder pressure and faster burning rate than a cold one. The effect of ethanol on combustion performance was to slightly reduce the burning velocity and reduce the maximum in-cylinder pressure. (4) The variability of the pre-flame HC concentrations (and by implication the mixture inhomogeneity) under cold conditions is normally higher compared with the warm conditions. This indicates that the increase in coolant temperature facilitates evaporation and hence stabilizes the subsequent combustion. For fuels with high ethanol blending ratios, the increase in ethanol content led to an increase in the mixture inhomogeneity at the spark plug. (5) For rich mixture operation (λ = 0.9) compared with stoichiometric, then E10 can lead to substantial reductions in PM emissions.


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    Title :

    Spray imaging, mixture preparation and particulate matter emissions using a GDI engine fuelled with stoichiometric gasoline/ethanol blends


    Contributors:
    Chen, L. (author) / Xu, F. (author) / Stone, R. (author) / Richardson, D. (author)


    Publication date :

    2011


    Size :

    10 Seiten, 6 Bilder, 4 Tabellen, 7 Quellen




    Type of media :

    Conference paper


    Type of material :

    Print


    Language :

    English




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