In the pursuit of environmentally friendly transportation, there is a critical need to rapidly transition the engines in the transportation sector away from fossil fuels while simultaneously reducing their emissions. An attractive solution to achieve this goal, particularly in heavy-duty applications with demanding energy and power requirements, is the utilization of methanol. Methanol stands out as a promising alternative fuel, owing to its potential carbon-neutral production process, liquid form resulting in high energy density and easy handling, and favorable combustion properties, as well as its clean-burning characteristics.
The high octane number of methanol makes it exceptionally resistant to knock, making it an ideal fuel for spark-ignited (SI) engines. Therefore, methanol was predominantly explored for use in SI passenger car engines, while heavy-duty engines, with their high power demands, still primarily rely on compression-ignition (CI) engines running on diesel. The limitations in size, efficiency and power of fossil gasoline SI engines, constrained by knocking phenomena, resulted in the prevalence of CI engines in heavy-duty applications.
This paper explores the potential of leveraging methanol's remarkable knock-resistant properties to facilitate SI operation in heavy-duty, high-speed marine engines. The study involves retrofitting an original 6-cylinder 7.15L CI diesel engine with six spark plugs and port injection of methanol to enable SI operation. Notably, efforts were made to minimize adaptations to the existing diesel engine, maintaining the compression ratio at 19:1 and retaining the same turbocharging pressure. This research aims to assess the feasibility of retrofitting conventional diesel engines for SI operation on methanol, with a focus on optimizing engine performance while preserving key characteristics for heavy-duty applications.