Engine-out Gaseous Emissions in a Diesel Engine using Methanol as a Low-carbon Fuel under Dual-fuel Operation

In this study, engine-out gaseous emissions are reviewed using the Fourier Transform Infrared (FTIR) spectroscopy measurement of methanol diesel dual fuel combustion experiments performed in a heavy-duty diesel engine. Comparison to the baseline diesel-only condition shows that methanol-diesel dual fuel combustion leads to higher regulated carbon monoxide (CO) emissions and unburned hydrocarbons (UHC). However, NO_X emissions were reduced effectively with increasing methanol substitution rate (MSR). Under dual-fuel operation with methanol, emissions of nitrogen oxides (NO_X), including nitric oxide (NO), nitrogen dioxide (NO₂), and nitrous oxide (N₂O), indicate the potential to reduce the burden of NO_X on diesel after-treatment devices such as selective catalytic reduction (SCR). Other unregulated gaseous emissions, such as formaldehyde (CH₂O) methane (CH₄), increased with higher MSR, but their emissions can be mitigated if advanced injection timing or increased intake temperature is used as reported in our separate study. In summary, this study suggests the potential use of methanol as a low-carbon fuel (LCF) to meet emissions regulations but indicates a slight increase in emissions of unregulated species.