Investigation of Liquid Lignin-Methanol Blends under Realistic Two-Stroke Marine Engines Conditions

With a view to reducing the environmental impact of fossil fuels, advanced lignin-based biofuels could provide a valuable contribute, since lignin is the most abundant biopolymer on earth after cellulose. However, its thermophysical properties would hamper its use as a pure fuel. In this work we investigated the combustion behavior of sprays of a liquid lignin-methanol blend and evaluated its potential as a low-carbon marine fuel for large two-stroke engines. To this end, an experimental campaign was conducted in an optically accessible combustion chamber whose main dimensions correspond to those of a single cylinder for large two-stroke engines. The chamber is provided with optical accesses for optical diagnostics of the combustion process. The combustion of the mixture was ignited using a diesel pilot jet as the ignition source. Two marine injectors are mounted in the chamber, namely “main” and “pilot” injectors. The tests were performed in environmental conditions around 40 bar and 500°C. The lignin-methanol blend was injected at pressure of 500 and 700 bar, whilst the injection pressure of the pilot diesel was kept at 500 bar. Two different relative orientations of the main and pilot sprays were investigated. The results showed that this type of fuel is suitable for durability trials for the assessment of its final use in a marine internal combustion engine.