The present contribution predicts the onset of knock and associated performance of a spark ignition engine fuelled with gaseous fuels such as methane. A two-zone predictive combustion model was developed based on an estimate of the effective duration of the combustion period and the mass burning rate for any set of operating conditions. The unburned end gas preignition chemical reaction activity is described by a detailed chemical reaction kinetic scheme. The variation with time of the value of a formulated dimensionless knockparameter K is calculated. This parameter relates the total energy released within the end gas due to autoignition reaction activity per unit of the corresponding instanteneous volume relative to the total energy release per cylinder volume that would take place normally due to regular flame propagation. When knocking is encountered the value of K builds up to a sufficiently high value that exceeds an acceptable limit. Under normal operating conditions, the value remains throughout the combustion period at comparatively low levels. Extension of the model to consider fuel mixtures and provide optimum procedures for getting out of a knocking conditions are also outlined.
A predictive approach to spark ignition engine performance fuelled with common gaseous fuels and their mixtures
Prädikative Betrachtung über die Leistung von Ottomotoren, die mit gängigen gasförmigen Kraftstoffen und ihren Gemischen betrieben werden
1995
6 Seiten, 6 Bilder, 15 Quellen
Conference paper
English
Otto-Motor , Gasgemisch , Methan , Gas , Kraftstoff , Motorleistung , Klopfen , Verbrennung (Oxidation)
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