Numerical Analysis of Emissions from Marine Engines Using Alternative Fuels

The current restrictions on emissions from marine engines, particularly sulphur oxides (SO_x ), nitrogen oxides (NO_x ) and carbon dioxide (CO₂ ), are compelling the shipping industry to a change of tendency. In the recent years, many primary and secondary reduction techniques have been proposed and employed in marine engines. Nevertheless, the increasingly restrictive legislation makes it very difficult to continue developing efficient reduction procedures at competitive prices. According to this, the paper presents the possibility to employ alternative fuels. A numerical model was developed to analyze the combustion process and emissions using oil fuel, natural gas and hydrogen. A commercial marine engine was studied, the Wärtsilä 6L 46. It was found, that hydrogen is the cleanest fuel regarding CO₂ , hydrocarbons (HC) and carbon monoxide (CO). Nevertheless, it is very expensive for marine applications. Natural gas is cheaper and cleaner than fuel oil regarding CO₂ and CO emissions. Still, natural gas emits more NO_x and HC than oil fuel. SO_x depends basically on the sulphur content of each particular fuel.