Pollutant Formation in SI Engine

The main focus of this paper is to study and investigate the cyclic emissions and pollutant formation in a typical SI engine. The main ingredient of pollutants formation in a typical SI engine is Nitric Oxide (NO) and nitrogen oxide (NO2) collectively known as NOx. The other components are carbon monoxide (CO) and unburnt hydrocarbons (HC). The following paper is based on the experiments performed on an optical single cylinder SI research engine under different conditions. High - speed natural light photography is done to maintain records of in cylinder pressure, temperature and other parameters of the combustion chamber. The experiments included the investigation of the effect of various engine parameters such as ignition timing and mixture air-fuel equivalence ratio on knocking combustion and pollutant formation. The investigations are done to keep a check on the formation of pollutants from the gasoline engines which affects the environment adversely. As a result of the investigation, at stoichiometric conditions, by advancing spark timing from MBT to knock intensity equal to 6 bar, instantaneous NO and HC emissions are increased up to 60% as compared to the MBT operating conditions. A further increase of knock intensity at the limits of pre-ignition region was observed to significantly drop NO emissions. It was found that when knocking combustion occurs at lean conditions, NO emissions are increased.