Two-stroke engine designer is expanding its portfolio of dual-fuel engines, to offer LNG carrier shipowners another option
In April 2019, the two-stroke business unit of MAN Energy Solutions announced it had begun developing the ME-GA dual-fuel engine, a new Otto-cycle, low-pressure gas engine as a complement to its existing dual-fuel ME-GI engine.
“We have been running tests on a single cylinder in our research centre and will have a commercial engine ready for delivery by Q3 or Q4 2021,” MAN Energy Solutions director, head of promotion and customer support, two-stroke marine Thomas S Hansen told LNG World Shipping.
High-pressure engines continue to dominate the two-stroke sector, and MAN Energy Solutions’ ME-GI series has about 112 dual-fuel ME-GI engines in service, with another 161 on order.
Mr Hansen said the reason for introducing the new low-pressure, Otto-cycle, dual-fuel engine is that there is a segment of the market, especially in LNG carrier tonnage, where shipowners have shown a recent preference for this option. Mr Hansen pointed out that when initial capex is considered over opex, shipowners have selected low-pressure, Otto-cycle engines.
This stems from the relative high cost of the fuel gas supply system, including the high-pressure compressor, for boosting up 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.
With its low-pressure, dual-fuel engine, competitor Winterthur Gas & Diesel (WinGD) has captured a significant portion of the LNG carrier newbuild orders.
MAN Energy Solutions sees the introduction of the low-pressure engine in terms of filling a gap within its portfolio, much akin to how its ME-LGIP engine – introduced in 2018 – added LPG to its roster, further broadening the list of liquid fuels its ME-LGI (liquid gas injection) engine can exploit.
Introducing the ME-GA dual-fuel engine does not mean MAN Energy Solutions is abandoning its high-pressure, diesel principle ME-GI engine. Far from it. “We are full steam ahead on our ME-GI Mark II development,” said Mr Hansen. “We are learning from the 550,000 operating hours accumulated on gas to make the system even more reliable, simpler and more cost efficient. In markets other than LNG tankers, the opex benefits of the ME-GI are undeniable and compelling,” he said.
Among the modifications in the ME-GI Mark II will be a simplified double-walled piping system that brings the LNG to the engine. The current design has inlet and outlet pipes. MAN Energy Solutions has engineered a system that will use a single pipe for both purposes. Besides reducing the use of expensive double-walled, high-pressure piping, “it will have the added benefit of making the system easier to purge with nitrogen, using the natural flow of gas,” said Mr Hansen.
In the latest ME-GI engine, MAN Energy Solutions is also lowering pilot oil consumption and reducing the lowest possible load on the engine in which you can operate on gas to 5%.
An added benefit and built in redundancy in the ME-GI Mark II will be gas cylinder cut out – the ability to continue to operate a multiple-cylinder engine when one cylinder has a failure. “If one cylinder fails, you continue operating that cylinder on fuel oil, while continuing to operate the remaining cylinders on gas,” said Mr Hansen. “In this way you can continue operating the engine unrestricted load.”
He said, “Shipowners have told us that they are operating on gas 97% to 98% of the time. An option such as this will increase that availability even further.”
While MAN Energy Solutions has produced engines that operate on LNG, LPG, ethane, and methanol, Mr Hansen emphasised that MAN Energy Solutions is not in the business of dictating what type of fuel shipowners should be using. “We are an engineering company. We act on market demands. We are here to assist the maritime industry in its energy transition by providing different solutions.”