In previous papers [1, 2], the authors proposed a hybrid combustion model able to predict the behavior of a small spark-ignition, multivalve, multipoint injection engine, at different operating points.
The combustion model proposed was implemented in the KIVA-3V [3] code for a closed valve simulation of engine operation. The results obtained for pressure cycles showed good agreement to the measured data and the characteristic constant of the model resulted less sensitive to the engine operating conditions such as rotational speed. Since the present research activity is aimed to investigate the potential for the adoption of alternate fuels, the latter point was considered of interest in modeling such off-design operation as a change in engine fueling. In this paper, the simulation results obtained by using the KIVA-3V code are compared to those provided by a different multidimensional code: AVL FIRE 72b [4]. The same computing mesh, reproducing the combustion chamber of the engine under study, has been utilized in both multidimensional codes and their different modeling capabilities have been analyzed. In particular, the two codes utilize different combustion models (Eddy-Breakup, PDF, CFM) and different turbulence models (k-ε, RSM). Thus, in order to evaluate the AVL FIRE code capability in providing sound engine information for engineering applications, the simulation results are compared. Furthermore, the results provided by the two codes, mainly in terms of indicated mean effective pressure, are compared to the experimental data obtained at the Cassino University Laboratory.