The influence of volume variation in a homogeneous prechamber ignition system in combustion characteristics and exhaust emissions

Abstract

Research on prechamber ignition systems has become increasingly frequent as they promote significant reductions in engine-out emissions with low cost of implementation. In these systems, the combustion starts in an auxiliary chamber and flows through the interconnecting holes, in form of jets, to the main chamber, where it ignites the air–fuel mixture contained therein. Besides the air–fuel ratio, the geometry of the prechamber presents fundamental parameters that influence combustion characteristics and, consequently, the exhaust emissions. This paper aims to evaluate the effects of prechamber volume variation in combustion and emissions of a commercial engine equipped with a homogeneous charge prechamber ignition system. For this, three volumes were considered in stationary tests of a multi-cylinder engine operating under stoichiometric conditions in 1500 rpm and 3.3 bar of IMEP. The results indicated that the increase in volume within the limits considered present increase in the energy released and, hence, in the burning speed, reducing the combustion duration. Comparing to the baseline spark plug system, the prechamber with 3.8% of the main combustion chamber volume presented the best configuration among the evaluated volumes, with an increase in the evolution of pressure traces and reductions in around 13% in unburned hydrocarbons (HC) and nitrogen oxides (NOx) engine-out emissions.