MAN ES BOOSTS ME-GA ENGINE PERFORMANCE

MAN Energy Solutions has rolled out an optimisation programme to improve the performance of its dual-fuel, low-pressure ME-GA engine before the first reference for its new two-stroke off

Ering Enters Service

MAN Energy Solutions announced that it is introducing an optimisation programme to improve the performance of its new dual-fuel, low-pressure ME-GA engine during a customer webinar held in mid-February 2023.

The optimisation programme addresses higher-thanexpected fuel consumption in gas mode, which was detected during prototype tests at HHI and HSD in the first half of 2022, representatives of two-stroke promotion and customer support told the audience.

The prototype testing was otherwise a success, and confirmed the basic design of the Otto Cycle based ME-GA engine. It demonstrated that the engine could operate at full load in both gas and diesel mode, and all failure modes.

modifications were required to increase the volume and pressure of air scavenged from the cylinder, potentially including the diffuser, nozzle ring or rotor.

Verification Step

MAN identified a number of different solutions for each of the root cause issues. These were then trialled on a 1-cylinder test engine at HHI-EMD for a fortnight in October, and subsequently on a full-scale engine test at HSD in November 2022 for three weeks.

Outcome

The successful development of the optimisation solutions means that new MAN B&W 5G70ME-C10.5-GA version will achieve lower specific fuel consumption (SFC) in gas mode than the original design. It is also expected to permit improved performance optimisation, due to improved mixing and scavenging.

The issues were related to excessive heat loss from the cylinder, as well as issues relating to early combustion in gas mode. MAN ES noted that the development of solutions to control the air volume and scavenging pressure, and combining it with the normal controls of engine tuning, meant that MAN was able to improve the operation of the cylinder, particularly at part load.

Problem Diagnosis

MAN ES has an established procedure for rectifying errors identified during the commercial production stage. This requires the identification of the origin (or root cause) of faults, and the development of solutions, which are then subsequently verified.

The investigation identified that the higher-than-expected fuel consumption was the being caused by two separate issues: excessive cooling losses in the combustion chamber, and insufficient performance optimisation.

The cooling losses were addressed by modifications to the design of the cylinder liner, reducing the cooling bores in the cylinder cover, as well as the introduction of a recirculation loop and insulating pipes in the cylinder liner helped to reduce heat losses.

MAN ES previously implemented a similar cylinder liner design concept on its conventional engines around 2012 in response to concerns about cold corrosion. The Load Dependent Cylinder Liner cooling (LDCL) solution is in service on many hundreds of engines with good results.

The performance optimisation issues were the result of a tendency to pre-ignition as well as excessively fast heat release, which were in turn the result of uneven air and fuel mixing.

The early heat release meant that a significant proportion of the energy was being released before top dead centre (TDC). MAN identified that optimising the geometry of the safe gas admission valve (SGAV) would improve the flow of gas into the cylinder. However, other turbocharger specific

The solution meant that MAN ES would be able to increase the maximum pressure within the cylinder and increase the compression pressure which improved the gas consumption.

The solution would also allow the ME-GA to be operated with the exhaust gas bypass closed at all loads, which should help to reduce energy losses.

FIRST DELIVERY OF ME-GA LNGC IN MAY

The optimisation configuration has been applied to the “two dozen” of the engines that have already been delivered by MAN Energy Solutions’ licensees, and they are already being updated before the first vessels to be powered by ME-GA engines undertake sea trials, Thomas Hansen, head of twostroke promotion and customer support at MAN Energy Solutions told a group of customers in February 2023.

The first LNG carrier to be powered by a ME-GA engine was expected to undergo sea trials in April 2023, with the first deliveries to customers expected in May.

The optimisation solution will be introduced to all 242 of the engines on order.

First Chinese ME-GA engine contracts

MAN Energy Solutions has won a number of contracts to supply its dual-fuel low-pressure ME-GA engine to six LNG tankers currently under construction in two different shipyards in China.

Thomas Hansen did not specify where the engines would be built. He noted that the majority of the 242 orders placed for the ME-GA engines had been received from the South Korean shipyards, HHI, SHI and DSME.