Experimental Assessment of Sustainable Lignin Fuels for Marine Engines

In the maritime sector, the development of cost-effective alternative fuels that eliminate the need for pilot injection is urgently required. Cold-processed lignin ethanol oils (CLEO) as a part of the CLEO project were developed as a potential fuel for large-scale two-stroke compression ignition (CI) engines, which are widely used in the marine industry. This PhD project evaluates the potential of CLEO as an alternative fuel for them by conducting experiments using a small compression ignition (CI) engine. The primary challenges in applying CLEO to CI engines are the formation of sticky sludge and hard adhesive deposits caused by solvent evaporation. These issues lead to clogging of the fuel system and seizing of piston rings in their grooves. To address these challenges, the small CI engine was extensively modified, drawing inspiration from large-scale two-stroke marine engines, and stable operation with CLEO was achieved. The ignition
quality of CLEO was then investigated by measuring ignition delays of CLEO, ethanolbased alternative fuel, methanol-based alternative fuels, and diesel reference fuel across a wide range of chamber pressures and temperatures using the small engine. The ignition delay data were correlated with the Arrhenius equation to predict ignition delay behavior under the representative chamber condition of large-scale two-stroke marine engines. The results confirmed CLEO’s ability to auto-ignite without the need for pilot injection. Additionally, the relationship between unburned hydrocarbon emission and spray penetration to the cylinder wall, which is a major cause of piston ring malfunction, was investigated using a fast-response flame ionization detector (FID). This PhD project identifies the general challenges and proposes approaches necessary for the application of CLEO, or more widely lignin-based fuels, to CI engines. Furthermore, the engine setup and testing methods established during this PhD project can be applied for evaluating other alternative fuels that cannot be adapted in conventional CI engines, enabling the assessment of their potential for marine engines.