Experimentally Supported Modeling of Cycle-to-Cycle Variations of SI Engine Using Cycle-Simulation Model

Modelling of early flame kernel growth towards a better understanding of cyclic combustion variability in SI engines

“…But, the results shown in Fig. 8 and in [29] show that the structure of combustion variation is not the same when only turbulence is varied. With the variation of turbulence only, the combustion progress is simple, i.e.…”

“…Without the variation of mean flow and turbulence level the CCV is reduced by up to 66%. On the other hand, if the CCV is produced only by the variation of mean flow and turbulence, up to 93% of overall CCV is obtained, but in that case there is a strong correlation between start of combustion and combustion duration which results in almost linear dependence [29]. The variation of the air equivalence ratio stratification is the second most important factor in producing CCV of combustion.…”

“…The cyclic variability of the in-cylinder turbulence level is produced by a predefined perturbation of the intake turbulence production constant S 10 , as described in [29,38]. The perturbation of the constant S 10 follows a normal (Gaussian) distribution around the mean value.…”

“…The early flame kernel growth is modelled by a newly [28] commonly used in 3D-CFD simulations. The developed cycle-simulation model is already used in [29] for the modelling of cyclic combustion variability, but the cyclic combustion variability was produced only by the variation of in-cylinder turbulence from cycle-to-cycle. Also, the analysis presented in [29] was performed on 4 operating points.…”

“…The developed cycle-simulation model is already used in [29] for the modelling of cyclic combustion variability, but the cyclic combustion variability was produced only by the variation of in-cylinder turbulence from cycle-to-cycle. Also, the analysis presented in [29] was performed on 4 operating points. In this study, the cyclic variability of combustion in SI engines is produced by a predefined perturbation of the turbulence intake production parameter, by a perturbation of the flow direction at the spark plug and by a perturbation of the stratification of air equivalence ratio from cycle-to-cycle, simulating the fluctuations of in-cylinder turbulence level, fluid motion and stratification of fuel, respectively.…”