Characterization of Gaseous and Particle Emissions of a Direct Injection Hydrogen Engine at Various Operating Conditions

This paper investigates the gaseous and particulate emissions of a hydrogen powered direct injection spark ignition engine. Experiments were performed over different engine speeds and loads and with varying air- fuel ratio, start of injection and intake manifold pressure. An IAG FTIR system was used to detect and measure a variety of gaseous emissions, which include standard emissions such as NOX and unburned hydrocarbons as well as some non-standard emissions such as formaldehyde, formic acid, and ammonia. The particle number concentration and size distribution were measured using a DMS 500 fast particle analyzer from Cambustion. Particle composition was investigated using ICP analysis as well as a Sunset OC/EC analyzer to determine the soot content and the presence of any unburned engine oil. The results show that NOX emissions range between 0.1 g/kWh for a λ of 2.5 and 10 g/kWh λ of 1.5. The highest particle concentration was found for low loads and low intake pressures, with peaks values as high as 5*10⁸ n/cc. ICP analysis confirmed that the particles contained traces of engine oil, while the OC/EC analysis showed that 99% of particle matter collected on filters was organic carbon, and <1% soot. The emissions of N2O as well as several other species measured with FTIR was found to be in the single ppm range, and thus not significant.