Developing a Knock Predictive Criterion in Spark Ignition Engines Fuelled with Gaseous Fuels

Consideration of the chemical reaction activity of the end gas in a spark ignition and operating conditions are combined to predict the onset of knock and associated performance in an engine fuelled with 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 for methane and air,The variation with time of the value of a formulated dimensionless knock parameter(k)is calcuated.It is shown that whenever knocking is encounteren.the value of “k” builds up to a sufficiently high value that exceeds a critical value.Under normal operating conditions,the value of “k” remains throughout the whole combustion period at comparatively very low levels.It is shown that the model and the use of this knock criterion“k” produce results that are in good agreement with experiment.

Consideration of the chemical reaction activity of the end gas in a spark ignition and operating conditions are combined to predict the onset of knock and associated performance in an engine fuelled with methane.A two-zone predictive combustion model was developed based on an estimate of the efiFective 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 for methane and air.The variation with time of the value of a formulated dimensionless knock parameter(k)is calculated.It is shown that whenever knocking is encountered,the value of'k' builds up to a sufficiently high value that exceeds a critical value.Under normal operating conditions, the value of'k'remains throughout the whole combustion period at comparatively very low levels. It is shown that the model and the use of this knock criterion'k'produce results that are in good agreement with experiment.