Use of Multizone Combustion Models to Analyze and Predict the Effect of Cyclic Variations on SI Engines

In this paper, a parameter to quantify the cyclic variability in first stages of combustion is presented, as an evolution of the parameter proposed by Hill and Kapil. This parameter relates the mean time necessary for the initial flame to reach the periphery of a turbulence eddy structure moving from the flame kernel position.

This parameter is used in combination with quasi-dimensional models in order to predict and analyze small-scale turbulence contribution to cyclic variations. The cyclic dispersion parameter could be introduced in the predictive models as a delay in the combustion beginning.

The parameter is compared with the experimental standard deviations in mass burned fraction at spark time obtained from others researchers works and own experimental data. A satisfying agreement between predictions and measurements is achieved. In addition, some predictive studies have been carried out to get, as a final goal, the establishment of a methodology to identify the importance of different factors causing cycle to cycle variations.