Experimental study on engine and emissions performance of renewable diesel methanol dual fuel (RMDF) combustion

Methanol (MeOH) and renewable diesel (RD) are being considered promising alternative fuels for the de-fossilization of internal combustion engines (ICE). This study provides an experimental investigation on the use of both fuels under dual-fuel combustion mode: port fuel injection (PFI) of MeOH and direct injection (DI) of RD. The combustion mode is labeled as RMDF (renewable diesel methanol dual fuel). The experiment was performed in a heavy-duty single-cylinder engine (SCE) equipped with combustion and emissions measurements and analysis for engine efficiency and emissions of soot and NOX (oxides of nitrogen). MeOH substitution rate, which is the mass ratio of injected MeOH fuel to total injected fuels of both MeOH and RD, was varied to study its effect on engine efficiency and emissions. Different MeOH substitutions were tested from low (6.9 bar gIMEP) to full (23.5 bar gIMEP) engine load conditions at a fixed engine speed of 1200 RPM. Test results showed that higher MeOH substitution rates can reduce NOX emissions effectively while improving engine thermal efficiency. However, a higher MeOH substitute rate can result in longer ignition delay at low load, and increased emissions of carbon monoxide (CO) and unburned hydrocarbon (UHC). Increased maximum pressure rise rate (MPRR) at high load condition was observed as the MeOH substitution rate increased. MPRR is not sensitive to the change in MeOH at low load condition. While ignition delay became longer at low load, it was shorter at high load as MeOH substitution rate increased. Overall, the results from this study suggest that RMDF can be considered as an option to achieve a cleaner and more efficient engine. However, further optimization of combustion designs and engine operating strategy need to be considered to improve combustion loss from RMDF emissions, possibly due to the lower reactivity of MeOH.