Pádraig Kelleher, MAN Energy Solutions, Denmark, details the technology behind a new, low-speed, dual-fuel engine designed for LNG carriers.
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AN Energy Solutions demonstrated its latest low-speed, dual-fuel engine – a MAN B&W ME-GA type designed for LNG/fuel oil running – at a ceremony live-streamed from the company’s Copenhagen Research Centre, Denmark, in March 2021. The new engine is an Otto-cycle variant of the company’s successful ME-GI engine. The ME-GA engine has already been specified in several LNG carrier new-building projects with the first order imminent, according to the company. Testing of the first, commercial ME-GA design is expected to begin by the end of 2021, with the first engine delivery following in early 2022. The MAN B&W ME-GA engine is aimed at vessel types and applications where low capital outlay is a priority, such as Aframax tankers. Furthermore, the engine will be Tier III compliant in gas mode without emissions-abatement equipment. The ME-GA engine features the following concepts: z The well-proven MAN B&W dual-fuel platform. z Unique gas admission concept with minimal installation and operating costs. z Well-known engine room design similar to ME-C/ME-GI engines.
Engine philosophy The ME-GA engine is a pre-mixed, dual-fuel engine type, where methane is admitted during the compression stroke (Figure 1). This allows for a low gas-supply pressure, which is advantageous for vessels with larger amounts of boil-off gas (BOG), such as LNG carriers. The ME-GA version features some of the most successful concept ideas from ME-GI and ME-GI Mk. II platforms.
Gas admission concept The simple supply and purging concept minimises installation costs. The gas admission system is designed to enable a safe and reliable operation at the lowest possible costs.
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Supply and purging concept The safety and purge concept from ME-GI Mk. II has been adapted to the ME-GA version with the introduction of beneficial features. Rather than injecting nitrogen from the gas valve unit (GVU), the nitrogen is applied at the engine end, and the purged volume carried along existing piping. This simplified solution reduces the amount of pipework and components, and significantly lowers the volume, reducing nitrogen consumption.
Safe gas admission valve The safe gas admission valve (SGAV) placed in the cylinder liner has been developed as a unique and simple component, which provides both the ultimate safety against gas leakage into the cylinder and secures optimal conditions for gas admission. Since the SGAV contains a gas admission as well as a window valve in one unit, the safety against gas leakage into the cylinder is doubled. Basically, the improved safety eliminates additional requirements for complex monitoring as a safety precaution, as opposed to other low-pressure, dual-fuel, two-stroke engines. The SGAV design gives room for easy overhaul of the valve itself, along with maximum space for overhaul on the engine top.
Gas regulating valve In order to achieve a simple and easy installation of the ME-GA engine and the
