Dual-fuel gas injection marine diesel engines gain popularity with LNG carrier operators
Dual-fuel gas injection marine diesel engines gain popularity with LNG carrier operators, confirmed, say MAN Diesel & Turbo (MDT) by a recent order from Teekay Corporation for two 173,400 cubic metre capacity LNG carriers to be powered by ‘M’-type, electronically controlled, gas injection (ME-GI) 5G70 engines. A contract option with builders, Daewoo Shipbuilding & Marine Engineering (DSME) of South Korea, allows for three more of the same large ships.
Unveiled at a major event at MDT’s Copenhagen Diesel Research Centre last year, the ME-GI engine represents the culmination of many years’ work that began in the 1990s with the company’s prototype MC-GI dual-fuel engine that entered service at a power plant in Chiba, near Tokyo, Japan in 1994.
A full-scale test on the 4T50ME-GI research engine in Copenhagen demonstrated that the engine, operating on high-pressure gas delivered from a fuel gas supply system comprising an LNG pump and a vaporizer, was able to fulfill Tier II and, later on, Tier III emission standards in combination with the MDT developed EGR system.
Fuel Flexibility: Main Advantage to LNG Carriers
One of the advantages of the ME-GI engine is its fuel flexibility, which is a major benefit to operators of LNG carriers; ships where an abundant gas supply from cargo (boil-off gas) serves as fuel, which despite its variation in heat value nevertheless perfectly suits the diesel working principle.
There is variation in that heat value when, for instance, at the start of a laden voyage, the natural boil-off gas holds a large amount of nitrogen, and the heat value is low. Later on when boil-off gas is forced, it can consist of both ethane and propane, and the heat value could be high. A two-stroke, high-pressure gas injection engine can burn those different fuels without seeing a drop in the thermal efficiency of the engine. To achieve this efficiently the control concept comprises three different fuel modes:
Fuel-oil-only mode
The fuel-oil-only mode is well known from the ME engine. Operating the engine in this mode can only be done on fuel oil. In this mode, the engine is considered ‘gas safe’; if a failure in the gas system occurs it will result in a gas shutdown and a return to the fuel-oil-only mode.
Minimum-fuel mode
The minimum-fuel mode is developed for gas operation, and it can only be started manually by an operator on the Gas Main Operating Panel in the control room. In this mode, the control system will allow any ratio between fuel oil and gas fuel, with a minimum pre-set amount of fuel oil to be used.
Mixed gas mode
The mixed gas mode is offered to give the operator full fuel flexibility and the option to inject a fixed amount of gas fuel. The ME control system will add up with the fuel oil until the required load for operation is reached.
These Teekay LNG engines are based on MDT’s new ultra-long-stroke G-type concept to deliver an even higher overall propulsion plant efficiency. ) 5G70 engine. A contract option with builders, Daewoo Shipbuilding & Marine Engineering (DSME) of South Korea, allows for three more of the same.
Source: Maritime Propulsion
