Effect of Intake Conditions (Temperature, Pressure and EGR) on the Operation of a Dual-Fuel Marine Engine with Methanol 2023-24-0046

In the upcoming decade sustainable powertrain technologies will seek for market entrance in the transport sector. One promising solution is the utilization of dual-fuel engines using renewable methanol ignited by a pilot diesel fuel. This approach allows the displacement of a significant portion of fossil diesel, thereby reducing greenhouse gas emissions. Additionally, this technology is, next to newbuilds, suited for retrofitting existing engines, while maintaining high efficiencies and lowering engine-out emissions. Various researchers have experimentally tested the effects of replacing diesel by methanol and have reported different boundaries for substituting diesel by methanol, including misfire, partial burn, knock and pre-ignition. However, little research has been conducted to explore ways to extend these substitution limits. Therefore, this study aims to investigate the effects of intake conditions, such as intake air temperature and pressure, and exhaust gas recirculation (EGR), on these limits, and, moreover, on several other engine performance parameters. It was found that higher intake air temperatures can extend misfire limits slightly, and with a trade-off as the possibility for pre-ignition increases. However, the gains in maximum substitution of diesel by methanol were minimal compared to the effort required to install a temperature control system. A reduction in intake air pressure was tested to mitigate knock but failed to do so, while EGR was able to increase the substitution limit. Brake thermal efficiency increased at high substitution limits with higher intake air temperature, but decreased with lower intake air pressure and with EGR. NOx emissions increased with higher intake air temperature and pressure, but decreased with EGR.