Responding to demands for a low-pressure, dual-fuel engine, MAN Energy Solutions’ new Otto-cycle, two-stroke ME-GA will be delivered to shipyards by the end of 2021
“For certain ship types, the low-pressure engine provides a lower capex,” said MAN Energy Solutions director, head of promotion and customer support, two-stroke marine Thomas S Hansen. Presenting during an exclusive webinar MAN B&W ME-GA – lower the pressure on your capital cost, Mr Hansen said the ME-GA was well suited for LNG carriers, since the vessels use boil-off gas, which can be fed directly into the engine via a low-pressure compressor. Similar in price to the company’s two-stroke, dual-fuel Diesel-cycle ME-GI engine, Mr Hansen said the ME-GA reduces the need for certain additional surrounding equipment, lowering the capex for shipowners.
This stems from the relative high cost of the fuel gas supply system (FGSS), including the high-pressure compressor, for boosting the pressure of the boil-off gas to the 300-bar injection pressure needed for the ME-GI – an investment only used for the LNG tanker application.
Mr Hansen said some 600 tests were conducted at the company’s research centre in Copenhagen in the development of the ME-GA to gather as much knowledge as possible about the Otto-cycle engine technology and refine the engine’s design.
One of the interesting aspects of the ME-GA is the design of the gas valve unit (GVU), which can be placed either inside or outside the engineroom, providing flexibility for shipbuilders and lower installation costs. Two versions of the GVU, one wall-mounted and another skid-mounted, are currently available, but other solutions from outside vendors may be considered.
EGR use yields environmental benefits
The ME-GA basic design is IMO Tier III compliant from day one when operating in gas mode, but in its research, MAN Energy Solutions found that using an exhaust gas recirculation (EGR) could yield significant operational and environmental performance benefits. Using an EGR can improve specific gas consumption (SGC) by about 3% and specific fuel oil consumption (SFOC) by about 5%, said Mr Hansen. The engine also becomes Tier III compliant when it operates on fuel oil. Additionally, methane slip – the bugbear for Otto-cycle low-pressure engines – was significantly reduced.
“The Diesel-cycle, two-stroke engine has low methane slip, between 0.2 and 0.4 g/kWh,” said Mr Hansen. “A low-pressure, Otto-cycle two-stroke engine inherently has a larger methane slip, between 2 and 4 g/kWh. With the EGR we will be able to reduce that (level of methane slip); we can’t say exactly by how much, but it will be significant.”
The high-pressure EGR unit is also integrated into the engine, limiting space requirements and lowering installation costs.
MAN Energy Solutions introduced its own EGR solution in 2012 and has over 211 engines with EGR on order, and another 33 in commercial operation. EGR has been used as a Tier III compliance measure on several ME-GI engines in service, said Mr Hansen.
Mr Hansen said the introduction of the ME-GA should not be seen as MAN Energy Solutions “shifting to low-pressure engines. It is about filling a gap in our portfolio.” MAN Energy Solutions is ‘full steam ahead’ on the development of the Mark II version of its popular Diesel-cycle, high-pressure dual-fuel engine ME-GI.
Building on the ME-GI’s success, the new ME-GA is seen as a complement to its existing (and growing) dual-fuel engine portfolio, as shipowners and shipping look to various fuel alternatives to comply with stricter emissions regulations. The Copenhagen-based engine designer’s dual-fuel portfolio now has engines that can burn LNG, ethane, methanol, ammonia and liquefied petroleum gas (LPG), reflecting shipping’s changing fuels landscape as the industry moves away from carbon-intensive fossil fuels.
MAN Energy Solutions will begin taking orders for the 70-bore MAN B&W G70ME-C10.5-GA version of the engine, with the first deliveries to shipowners and shipyards in Q4 2021.
Shipowners in the LNG carrier sector have shown a preference for an Otto-cycle, low-pressure dual-fuel engine, with competitor Winterthur Gas & Diesel (WinGD) securing a spate of orders for its WinGD X-DF propulsion unit for newbuilds. MAN Energy Solutions’ development of the ME-GA engine is the company’s ‘shot across the bow’, indicating that it is not willing to cede any territory in the two-stroke, dual-fuel engine battle – whether it is low-pressure, Otto-cycle or high-pressure, Diesel-cycle engines.
Shipowners will be the real beneficiaries of the competition between the two engine builders, reaping the rewards of intensive testing, R&D and engineering efforts by both parties.