Application of a Newly Developed Water Mixture Fuel Generator to IMO Regulations

Abstract

Within the IMO regulations, NO_x Tier II (from 2011), ECA (from 2016), and EEDI (from 2013) have been effective, and restriction of sulfur content in fuel oil (from 2020), expansion of the scope of restrictions of ECA (from 2021), and the restriction of black carbon (BC) are now being examined. Marine diesel engines that will be designed in the future must have performances that satisfy all these restrictions. Therefore, for the present study, a system that satisfies all of the restrictions relative to NO_x, EEDI, and BC was constructed by using newly developed water mixture fuel (WMF) technologies without additives. For this experiment, a small four-stroke high-speed marine diesel engine was used as a real engine model. To clarify the influence of WMF technologies on engine performance and exhaust emissions, the following experiments were performed. (1) Confirmation of the NO_x-SFOC (specific fuel oil consumption) trade-off: The variations in NO_x and SFOC when the fuel injection timing was advanced by 1 degree to 3 degree (crank angle) were clarified. (2) Influence of WMF technologies on the NO_x-SFOC trade-off: The variations in NO_x and SFOC when water was mixed with the fuel were clarified at each injection timing. (3) Influence of WMF technologies on BC: The ratio of PM when water was mixed with the fuel was measured by using a highly accurate PM measurement system, in addition to clarifying the ratio of BC in PM. (4) Combustion analysis: The cylinder pressure and fuel injection pressure obtained from each experiment were analyzed, clarifying the ignition period, highest pressure and its period, heat release rate, combustion speed, and combustion ratio. Analysis of the results revealed that (1) NO_x increases by about 25%, while SFOC is improved by 3%, when fuel injection timing is advanced by a 3 degree crank angle. (2) NO_x can be decreased without increasing SFOC by mixing water with the fuel. For instance, NO_x can be decreased by about 20% by mixing water with the fuel at a 20% W/FO ratio. (3) PM and BC can be decreased by mixing water with the fuel. For instance, PM and BC can be reduced by half by mixing water with the fuel at a 20% W/FO ratio. (4) NO_x, SFOC, and BC can be decreased at the same time by using WMF technologies and effectively combining the other results. Most importantly, WMF technologies allow most IMO regulations to be met.