In this study, the particle emissions of a single-cylinder research engine with a large displacement fuelled by hydrogen are investigated in comparison with natural gas. Particle count measurements with sensitivity for particle sizes from 10 nm resulted in relatively low values of 10^4 to 10^5 1/cm^3, whereby unexpectedly slightly higher values were found in hydrogen than in natural gas operation. However, the concentrations are still considerably lower than with conventional liquid fuels.
This is due to particles containing lubricating oil and a stronger interaction of the fuel with the oil film in hydrogen operation, as accompanying 3D CFD simulations showed. When developing improved H2 combustion processes, care can now be taken, for example, to limit the fuel concentration near the combustion chamber wall in order to avoid the observed effect. [https://doi.org/10.1039/D4VA00200H]