Exhaust Emission Analysis of a Spark Ignition Engine Operating with Hydrogen Injection in a Pre-Combustion Chamber

Due to the large negative impact of combustion gas emissions on air quality and the more stringent environmental legislation, research on internal combustion engines (ICE) are being developed to reduce emissions of pollutant gases to the atmosphere. One of the research fronts is the use of lean mixtures with the pre-chamber ignition system (PCIS). This system consists of a pre-chamber (PC) connected to the main chamber by one or more interconnecting holes. A spark plug initiates combustion of the mixture present in the pre-chamber, which is propagated as gas jet into the main chamber, igniting the lean mixture present therein. The gas jets have high thermal and kinetic energy, which promote faster combustion duration, making the system less prone to knock and with lower cyclic variability of the IMEP, enabling the lean limit extension. The pre-chamber system can be assisted with a supplementary liquid or gaseous fuel injection, enabling the charge stratification. In this context, this paper aims to evaluate the reduction in exhaust emissions from an ICE adapted with a stratified PCIS operating with lean mixture (ethanol-air) in the main chamber and hydrogen injected directly into the pre-chamber. The tests were carried out on a Ford Sigma 1.6L engine operating at 2250 rpm and under an indicated effective mean pressure of 5bar. It was possible to identify that with the use of the pre-chamber ignition system, the lean limit of the mixture was extended to lambda 1.7 with low cyclic variability of the IMEP. If compared to the baseline engine, the PCIS prototype operating with lambda 1.7 showed reduction in volumetric exhaust emissions of 98.4% for NO_x, 35.3% for HC, 69.9% for CO and 46.2% for CO₂. These results allow to conclude that the use of PCIS to burn lean mixtures can promote significant reductions in exhaust gases emissions to the atmosphere.