Investigating the size, morphology and composition of particulate matter released during transient and steady-state operation from a heavy-duty internal combustion engine running entirely on hydrogen

As hydrogen is explored for future propulsion, evaluating the morphology and chemical composition of lubricant oil-derived particles is crucial to understand the implications of our current path to decarbonisation, since existing data on such emissions is extremely limited. Particle size, count, morphology, and elemental composition were analysed from a spark-ignited hydrogen engine exhaust under two steady states (2400 rpm–50 Nm, 1300 rpm–150 Nm) and a 20-min transient cycle. Solid particle number was measured with a DMS500 and catalytic stripper; morphology and composition were analysed via transmission electron microscopy and EDX using graphene oxide and SiN grids with a novel particle collection method. At the high speed, particle concentration peaked at 3.14 × 10 7 /cm 3 , with 80 % under 10 nm. Low speed showed 2.31 × 10 5 /cm 3 . Particle size distribution nucleation modes were 7.5 nm (high speed), 8.66 nm (low speed) with most particles <23 nm. EDX analysis revealed C, Ca, Zn, P, and S from lubricant oil, while Cl, F, Na, and K originated from coolant. Fe and Ni indicated engine wear. Transient operation generated particles from 10 nm to >500 nm clusters, crystalline structures and agglomerates. A ring pack redesign reduced oil consumption, lowering emissions for high-speed case to 2.14 ± 1.29 × 10 5 /cm 3 . Compared to diesel, hydrogen cut particle number emissions by 98.8 %.