Computational exploration of bio-oil blend effects on large two-stroke marine engines

Abstract

Maritime shipping is an essential and growing component of international trade, with over 90% of all the world’s goods being transported on large ocean-going vessels. The sector is also among the last to reduce criteria pollutants and is responsible for up to 3% of global CO2 emissions. For the first time, the maritime sector is facing regulatory action on multiple fronts: reductions in fuel sulfur content, CO2 emissions, and NOx emissions, as well as expected upcoming limits on black carbon emissions. Decarbonizing the maritime sector requires the development of new fuel sources that do not compete with other transportation fuels in the global market. Because of the extremely large physical size of the internal combustion engines present in shipping vessels, experimental development of the engine-fuel system is often cost prohibitive. This work aims to develop a computational model of a scaled marine engine. The scaled model is representative of a custom-built 1:10 scale research engine commissioned for lubricant research at Oak Ridge National Laboratory. Reduced chemical mechanisms are developed for diesel, biodiesel, bio-oil, and polycyclic aromatic hydrocarbons (PAH). The mechanisms are combined, and the impact of these fuel blends on the emissions of NOx and PAHs (as a surrogate for soot) is assessed. The model is validated against experimental data, and details of the differences in the combustion process between the different fuels are discussed.