Ultra-low emissions of a heavy-duty engine powered with oxymethylene ethers (OME) under stationary and transient driving conditions

Abstract

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 (NOx) 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 NOx 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 NOx 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.

Gaseous emissions of a heavy-duty engine fueled with polyoxymethylene dimethyl ethers (OME) in transient cold-start operation and methods for after-treatment system heating

“…14,15 Table 2 illustrates the properties of the test engine used. The engine application was the same as in the previous study, 19 with a focus on a higher dynamic of the exhaust gas recirculation (EGR) valve.…”

“…The differences in the design of the two SCR stages resulted from the application to achieve the ultra-low NO x emissions demonstrated in the previous study. 19 Urea dosing was active in both SCR stages during the test cycles and considered the same starting temperatures as in standard diesel operation. The dosing strategy was based on ideal distribution between both stages in consideration of the temperature, the ammonia storage capacity, and the determined NO x concentrations in the exhaust, which was similar to the experiments in the previous study.…”

“…The results of Gelner et al did not show any tailpipe emission of HCN with a hot ATS. 19 They assumed a combination of oxidative catalysts upstream and downstream of the SCR stage to be essential for avoiding the tailpipe emission of HCN because of the prior oxidation of CH 2 O and the downstream oxidation of eventually formed HCN.…”

Introduction to the current and future use of H2 and H2-based e-fuels in combustion engines and fuel cells Special Issue

“…Life cycle analysis, including end-of-life disposal, is a critical topic that requires attention, but it is considered outside the scope of this special issue. The papers in this category include studies of: the use of anode off-gas of a methane-fueled solid oxide fuel cell system in an internal combustion engine, 7,8 the effect of compression ratio and bore/stroke ratio on methanol-fueled spark-ignition engine operation, 9,10 the role of hydrogen enrichment for diesel-pilot combustion in a high-speed compression ignition engine and in a spark-ignited large-bore engine, 11,12 the effect of oxymethylene ether on emissions and aftertreatment system design for ultra-low emission compression-ignition engine concepts, 13 the potential of Miller cycle in combination with synthetic fuels for heavy-duty engine applications 14 and the potential of hydrogen/diesel compared to gasoline/diesel reactivity-controlled compression ignition combustion utilizing a second law analysis. 15 The Editors hope you find this issue interesting and that the papers can spark a dialog on the important topic of hydrogen utilization in engines and fuel cells in the field of mobile and stationary applications.…”

“…the effect of oxymethylene ether on emissions and aftertreatment system design for ultra-low emission compression-ignition engine concepts, 13…”