Mitsubishi Heavy to develop low-speed, 2-stroke, dual-fuel marine diesel capable of using natural gas
Mitsubishi Heavy Industries, Ltd. (MHI) will begin developing UEC-LSGi: low-speed, dual-fuel, marine diesel engines capable of using not only conventional heavy oil but also natural gas for their fuel. The new engine will be added to the lineup of the Mitsubishi UEC Engine Series, the company’s 2-stroke, low-speed marine diesel engine brand.
Scheduled to be launched onto the market in 2015, MHI aims to reduce the economic and environmental burden on ship operators.
For the new engine, MHI develop new components requisite for dual-fuel use, including a new direct fuel injection system, a gas-fuel supply system and control system, targeting to complete preliminary testing by a single cylinder testing machine within fiscal year 2013 (by the end of March 2014). The company will then conduct verification tests for full-scale engines with dual-fuel use capability and bring an 11,000–18,000 kW class power output UEC-LSGi engine with a cylinder bore of 600mm onto the market.
The price of heavy oil used as fuel for low-speed, 2-stroke marine diesel is expected to rise in the future. In contrast, the price of natural gas fluctuates in a relatively narrow range, and the supply of shale gas, a non-conventional type gas, has stabilized due to the advances and sophistication of production technology. Under these conditions, the interest and expectation of concerned parties in the development of natural-gas firing low-speed, 2-stroke marine diesel engines has been increasing, MHI notes.
In addition, the IMO (International Maritime Organization) is progressively strengthening regulations on sulfur content in fuel oil aiming to reduce SOx (sulfur oxides) contained in gas emitted from ships. Ultimately, the sulfur content in the fuel used for marine ships will be required to be less than 0.5% in 2020, considerably lower than the current figure of under 3.5%.
Operators of ships using heavy oil fuel are required either to use the costly low sulfur content fuel or install sulfur removal exhaust gas treatment systems to engines. If a low-speed marine diesel engine that is capable of using natural gas for its fuel is developed, those measures will become unnecessary as natural gas does not contain sulfur.
For the UEC-LSGi engine, MHI will use a diffusional combustion method, in which high-pressure gas (~300 bar), is injected in the air compressed by the cylinder stroke and ignited by the pilot flame by a very small amount of fuel oil. The method delivers responsiveness for changes in gas fuel composition and sudden changes in engine load, compared with the pre-mixed combustion method, in which low-pressure gas is mixed with air and then compressed. Leveraging this feature, MHI says it will develop the engine with high combustion stability.
The UEC-LSGi will also be designed to be capable to operate with heavy fuel only to 100% engine load, which enables it to meet various operational needs. For NOx (nitrogen oxide), natural gas is slightly advantageous compared with conventionally used heavy oil. MHI will apply its EGR (exhaust gas recirculation) technology, currently in development, and others for the new engine to comply with IMO rules.
MHI is the only licensor of the low-speed, 2-stroke marine diesels in Japan.