Simulation of operation and control of LNG and diesel dual fuel engine for marine application

The use of Liquefied Natural Gas (LNG) as fuel for marine engines is being considered favourably as LNG provides a few advantages. LNG is a cleaner fuel than diesel because being a simpler hydrocarbon and the fact that it is gaseous when introduced into the intake or cylinder results in a more complete combustion and no particulate emissions. Another advantage of LNG (i.e., mostly methane) is that it has a lower carbon content than diesel thus producing less CO2 for the same power. Other than environmental considerations, LNG can also provide the possibility of lower fuel cost and also diversification of fuel supply. However, the mix ratio between LNG and diesel is a challenge as the operation has to avoid knock (due to too high LNG portion) and misfire (due to too low LNG portion). This paper provides simulation results of operation and control of dual fuel (LNG and diesel) operation for a ferry application. The subject ferry is the ferry operating between Malta and Gozo. The ferry power demand over a round trip was measured. The CO2 emission predictions from dual fuel operation using a fixed quantity of pilot diesel and a percentage share of pilot diesel are presented and compared to that from diesel only operation.