Development of a homogeneous charge pre-chamber torch ignition system for an SI engine fuelled with hydrous ethanol

Energy is the key to wellbeing and sustainability of modern civilization and its demand continues to increase. With the end of oil availability perspectives and the world energy crisis, technological solutions are needed from the scientific community to promote the reduction of fossil fuel consumption, the maximization of fuel conversion efficiency and the reduction of emission levels in internal combustion engines. Aiming at reaching these needs, the use of a pre-chamber ignition system in spark-ignition (SI) engines is a potential alternative enabling such engines to operate with lean mixtures and with a wide variety of fuels. In this study, a methodology was developed to design and characterize experimentally a homogeneous charge pre-chamber torch ignition system fuelled with hydrous ethanol (with 6-7% in mass of water content) and using lean burn mixtures (excess air ratio (lambda) > 1.0). The methodology, which has not been reported previously in other works, consisted of a one-dimensional mathematical model, that allowed for the definition of pre-chamber geometrical parameters. The device was manufactured and adapted to an SI engine, requiring no additional work to the cylinder head, as the pre-chamber was mounted in the original spark-plug screw thread. The prototype was experimentally characterized on an active dynamometer, and performance, combustion, emission and combustion visualization were studied. The pre-chamber ignition engine expanded the flammability limit in comparison with the baseline engine. For lambda = 1.4, engine fuel conversion efficiency was increased by 5.4%, specific fuel consumption decreased by 22% and nitrogen oxides (NOx) emissions reduced by 52%, but total hydrocarbons (THC) emissions increased. Improvements achieved were due to the faster burn rates characterized by the reduced MBF 0-10%, combustion duration and combustion instability, and also the increased thermodynamic efficiency and the lower combustion temperatures achieved with lean burn technology. From the conclusions obtained in this research, the homogeneous pre-chamber torch ignition system developed for hydrous ethanol has potential for application and marketability integration, as an alternative technology able to help meet energy demands in a sustainable manner.