Development and Assessment of a Multizone Combustion Simulation Code for SI Engines Based on a Novel Fractal Model

Numerical Simulation Techniques for the Prediction of Fluid-Dynamics, Combustion and Performance in IC Engines Fuelled by CNG

“…(4-5) for each chemical species, by means of polynomial functions of the gas temperature. JANAF tables can be used for this purpose (Baratta et al, 2006;Catania et al, 2003Catania et al, , 2004. The unburnedgas enthalpy includes the contribution of the fuel chemical energy which is released during combustion.…”

“…The conservation of the chamber volume can be used to derive an equation that links the pressure at a given crank angle to T u , T b , and x b (Baratta et al, 2006):…”

“…The temperature is considered uniform in the gas exchange phase and in the high-pressure cycle prior to the start of combustion, whereas a two-zone (burnedunburned) methodology is followed after the start of combustion and prior to the opening of the exhaust valve (see, for example, Gamma Technologies, 2009). Sometimes a multizone approach is followed, in order to accurately describe the burned-gas temperature distribution and the pollutant formation mechanisms (Baratta et al, 2006(Baratta et al, , 2008Onorati et al, 2003). …”

“…(12) or (13), involves the evaluation of the laminar burning speed, S L , of the in-cylinder turbulence generation, as well as of the turbulence-flame interaction (Baratta et al, 2006). As will be shown later on, each of these aspects can exert a remarkable influence on the indicated cycle prediction.…”

“…In fact, a sub-model for the flame deformation by the in-cylinder flow would need detailed information on the flow motion characteristics, which is not compatible with the thermo-dynamic nature of the overall model. The evolution equation for the burned-gas mass fraction x b can be derived adopting two different approaches (Baratta et al ., 2006). a. the 'prompt burning' approach: the mixture that is entrained through the flame front burns promptly.…”