Particle emissions of direct injection internal combustion engine fed with a hydrogen-rich reformate

Abstract

Thermochemical Recuperation is a promising waste heat recovery method that enables utilization of the engine waste heat together with onboard hydrogen production resulting in a significant improvement in thermal efficiency and a massive reduction in gaseous pollutants emission. However, an unexpectedly high particle emission level as compared to the gasoline-fed engine was measured despite the combustion of a hydrocarbon-free hydrogen-rich methanol steam reforming (MSR) products, containing 75% mol. H2 and 25% mol. CO2. In the existing literature, this phenomenon has not described yet.In this reported study, experiments are performed to investigate reasons of the elevated particle emissions by a direct injection spark ignition engine fed with MSR reformate, and results are compared with a baseline engine fed with gasoline at the same engine loads and speeds. Results of particle number concentration and size distribution measurements show that the total particle number concentration emission of engine fed with MSR reformate is 170% higher compared to gasoline. A direct experimental comparison between the port and the direct reformate injection performed on the same engine shows an increase in particles formation with a direct injection method. Based on these findings, several hypotheses are presented attributing to excessive lubricant involvement in the combustion process. The peculiarities specific for direct reformate injection that could result to the enhanced particles formation are jet – lubricated wall interaction, lubricant vapor entrainment into the reformate jet and shorter flame quenching distance of hydrogen compared to gasoline.