A small spark-ignition engine, in wide spread commercial usage since numerous years, is at present under study with the aim of improving its performance, in terms of a reduction of both fuel consumption and pollutant emissions.
In previous papers, the influence of piston geometry [1] and intake system [2] on the combustion process has been evaluated by means of a 3-D computational model. In this paper, a more extensive analysis of the parameters affecting the combustion rate, hence thermal efficiency, pollutant formation and engine stability, has been carried out.
In particular, at ELASIS Research Center, three prototypes featuring different combustion chambers have been realized and analyzed to the aim of assessing the influence of the squish area percentage on the flame front propagating in a quiescent charge.
Furthermore, the AVL FIRE computer code has been utilized in order to simulate the engine behavior at full load operation. The intake, compression and combustion processes have been modeled. The performance of different squish areas have been evaluated varying the flow field at the end of the intake stroke. In this way, a more realistic engine behavior can be investigated and useful information on matching the charge motion generated during induction and during compression can be achieved.
The model results have been validated comparing them to the measured data.
At the end, the purpose of both modeling and experimental activity is to provide guidelines for the development of optimal solutions aimed to improve the combustion process quality and the consequent engine performance.