Polyoxymethylene dimethyl ethers (OME) are promising substitutes for fossil diesel fuel. Besides the possibility of closing the carbon cycle, OME also feature soot-free combustion. Although this has been demonstrated sufficiently, nanoparticle emission in OME exhaust is mainly unknown. Many studies provide information about the particle size distribution (PSD) in the exhaust of OME-fueled diesel engines, but lack a distinction between solid particles and particles of a volatile nature. This distinction is necessary in order to evaluate the potential of OME regarding Euro VI and the Euro VII exhaust gas legislation being discussed. This study investigates the PSD of fossil diesel and the OME exhaust of a heavy-duty engine with and without removal of the volatile fraction via a catalytic stripper, by means of a purpose-built sampling system based on proposals from the Particle Measurement Programme (PMP). The experiments showed that most of the nuclei mode investigated in OME operation is of a volatile nature and that the solid particle number (PN) emission is below that of Euro VI diesel operation. Moreover, the results indicate that a state-of-the-art aftertreatment system removes most of the particle emission, regardless of whether it is volatile or solid. Selective catalytic reduction using aqueous urea dosing increases solid particle emission, especially in the sub-23 nm range. However, a PMP-conformant measurement of PN₂₃ and PN₁₀ during WHSC and WHTC runs demonstrated that the PN emission of an OME-fueled engine falls below the average immission level of urban and regional background in Germany.

Polyoxymethylene dimethyl ethers (OME) are promising candidates as substitutes for fossil diesel fuel. A regenerative electricity-based production, using captured airborne carbon dioxide (CO₂) and hydrogen (H₂) from water electrolysis as reactants, provides a valuable contribution to the energy transition in mobile applications. Besides the possibility of carbon-neutral production, OME offer the advantage of a sootless combustion, which resolves the trade-off between soot and nitrogen oxides (NO_x) emissions, and supports the efforts of air pollution control. While the emission behaviour of OME-powered diesel engines in raw exhaust has been studied extensively, interactions between this exhaust and components of the after-treatment system are mainly unknown. This study contains investigations conducted using a urea dosing variation (alpha titration) on a heavy-duty engine in combination with a system for selective catalytic reduction (SCR). These investigations showed a lower NO_x reduction efficiency in OME operation in partial load operation compared with the one in fossil diesel operation. This can be attributed, among other reasons, to lower exhaust temperatures in OME operation. However, the high tolerance of OME to exhaust gas recirculation (EGR) compensates for this disadvantage because of the reduction of the raw NO_x emission level. The difference in SCR efficiency disappeared at a high load operation point. Additionally, the alpha titration revealed, that urea dosing decreases formaldehyde emission in the SCR system. A pre-conditioned WHSC and WHTC cycle demonstrated the potential of an OME engine with after-treatment in the form of a twin-dosing SCR system for ultra-low emissions. For the specific evaluation of the emissions during these test cycles, this study contains the detailed calculation of the required factors – so-called ‘ u-values’– for OME exhaust according to the technical standard UN/ECE R49.

Cold-start emissions of the sustainable alternative diesel fuel OME are predominantly NO _x , formaldehyde, formic acid and unburned OME. Electrical heating in combination with fuel dosing is an effective method for after-treatment system heating.

In an effort to mitigate the impact of climate change, e.g., by reducing the emission of greenhouse gases, hydrogen is becoming an increasingly attractive alternative energy source, replacing conventional long-chain hydrocarbon fuels in the energy and transport sector. While there is a shift in individual transport towards battery-electric applications, the maritime and energy production sectors rely on a high energy density and time- and location-independent availability of the energy carrier. Therefore, large-bore engines powered by renewable fuels have the potential to shift the industry towards a climate-neutral operation. Besides the emission of greenhouse gases, internal combustion engines are known for emitting pollutant emissions, harming human health and the environment. Research on particle emissions of natural gas and hydrogen engines has mainly focused on automotive and heavy-duty applications. Hence, this study investigates particle emissions of a large-bore single-cylinder research engine powered by hydrogen, compared to natural gas, for the first time. Investigations on particles with a diameter as low as 10 nm showed particle numbers of 10⁴ to 10⁵ # cm⁻³, unexpectedly achieving slightly higher particle numbers in hydrogen than in natural gas operations. This is due to particles from lubricant oil and a stronger fuel interaction with the liner oil film in hydrogen operation, demonstrated within a 3D-CFD simulation. The concentrations are still lower by several orders of magnitude than in long-chain hydrocarbon fuel operations of identical engines. An extended emissions analysis based on the gaseous components THC, CO, and CO₂ shows the negligible carbonaceous emissions induced by these oil-based particles.

Internal combustion engine vehicles and electric vehicles share many similarities in the event of a vehicle fire but also differ in certain aspects. While both vehicle types release pollutants typical of vehicle fires, fires involving electric vehicles also emit battery-specific emissions. To investigate hazardous-substance exposure of emergency responders, two fire tests were carried out on identical electric vehicles. In each test, one battery cell was mechanically short-circuited, resulting in thermal runaway and propagation within the battery. Gas and time-resolved aerosol measurements, wipe samples, extinguishing agent samples, and urine samples were analyzed. A primary finding was the pronounced variability between the two fire events: despite comparable test conditions, the two vehicle fires exhibited markedly different development patterns, highlighting the inherent variability of electric vehicle fire behavior. Wipe samples showed increased metal concentrations after the tests, with maximum post-extinguishing surface concentrations of 7.4 mg/m² nickel, 17.45 mg/m² cobalt, and 14.25 mg/m² lithium. Extinguishing agent samples showed increased concentrations of inorganic contaminants and polycyclic aromatic hydrocarbons. Urine samples showed no indication of a systematic increase in creatinine-adjusted metal concentrations among protected participants. Toxic gases were released immediately after cell short-circuiting, with hydrogen fluoride, hydrogen cyanide, and acetylene reaching approximately 500 ppm before visible flames occurred. Aerosol measurements identified transiently elevated particle number concentrations in the exterior near-field environment and, in one test, inside the passenger compartment, where a shift towards smaller particle diameters was observed. The findings demonstrate multiple responder-relevant exposure pathways and substantial variability in electric vehicle fire events.