Experimental Investigation and Modeling of Cycle by Cycle Variations in a Gas Fuelled S.I. Engine

Experiments were conducted on a single cylinder, four stroke S.I. engine fuelled with biogas to characterize the nature of cycle by cycle variations (CCV) at different equivalence ratios. A full cycle simulation program using a two zone model with the capability to study the effects of fluctuations in equivalence ratio on hydrocarbon emissions was developed. CCV have been modeled using the Monte Carlo simulation scheme. The scheme has the capability to account for the deterministic and stochastic effects on the inputs. The model was validated using steady state experimental data and then applied to predict UBHC (Un Burned Hydro Carbon) emissions under conditions of low to high CCV. The predictions agreed fairly well with experimental results. The model can be used to determine the influence of adjusting spark ignition timings of cycles based on individual cycle equivalence ratios.