Study of Cyclic Variation in an SI Engine Using Quasi-Dimensional Combustion Model

The paper is concerned with the effects of cyclic variation in turbulence (expressed in terms of rms turbulent velocity) on the burn rate and subsequent cyclic variation in in-cylinder pressure derived parameters. The task has been addressed by applying a thermodynamic engine modelling approach for simulations of two very different engines; a single cylinder research engine in which sources of cyclic variation other than turbulence had been minimised and a multi-cylinder production engine. The cyclic variability in the two engines had a number of similar features; the effects of turbulence variation cycle-to-cycle proved dominant in the production engine, mixture strength secondary and prior-cycle residual concentration feedback marginal.