An attempt of exhaust gases composition prediction in si engines powered by petrol and gaseous fuels

Optimization procedure of the si engines feeding systems requires the application of newer and more sophisticated tools, as an addition to well known but expensive experimental methods. Numerical methods can be considered nowadays as once playing the most important role in the combustion process analysis. Paper describes the application of the dual zone model, allowing the analysis of the combustion process in an SI engine with the possibility of estimating 10 different exhaust gases i.e.: CO2, CO, H2O O2, NO, N2, H2, H, O and OH. The research has been carried on a 1.6 litr es four cylinder SI engine, fed with petrol and alternatively with LPG and CNG. In-cylinder pressure for the 4th cylinder of the tested engine has been acąuired for several engine speeds. registered in-cylinder pressure traces p=p((fi), together with the volume variation nii=nii((fi) infunction ofcrank angle, were used in the combustion process simulating calculations. Obtained results made it possible to compare selected parameters describing the combustion process. Obtained results do also prove recognized fact related to the higher temperature necessary to initiate gaseous fuel combustion.