MAN UPGRADES 350MM BORE TWO-STROKE SERIES

An upgraded design of small, two-stroke propulsion engine in the 350mm-bore category has been released by MAN Energy Solutions to supersede the S35ME-B type.

The new S35ME-C9.7 version reinforces MAN ES’ competitiveness in the small bore low speed market, where its engines are used in smaller tankers, bulk carriers, and general purpose vessel segments.

The new S35ME-C9.7 version achieves a lower specific fuel oil consumption (SFOC) across-the-board than the current design, and also presages the introduction of a range of variants capable of running on alternative fuels.

With the update of the S35ME-B9.7 to the ME-C concept, the engine is now available with part-load optimised fuel consumption and exhaust gas recirculation (EGR) operation. Selective catalytic reduction (SCR) had been the recommended Tier III technology for the small-bore ME-B engines.

The enhanced SFOC performance reflects an increase in scavenge air pressure. For the engine at its top (L1) nominal maximum continuous rating, producing 870kW per cylinder at a crankshaft speed of 167rpm, scavenge pressure has been raised from 4.2 to 4.3 bar. At this rating point, SFOC is reduced from 170 to 169g/kWh.

The layout diagram is identical to that of the existing engine, offering a high degree of possibilities for specified power and running speed combinations, ranging from 495kW at 118rpm on the L4 rating line, up to 870kW at 167rpm. The difference is the lowered fuel consumption throughout the load range, optimised at part-load.

The upgraded engine retains the 4.43:1 stroke/bore ratio adopted in the previous S35ME-9 along with an unchanged mean effective pressure of 21 bar.

The retention of the engine outline and footprint will also minimise difficulties for licensee engine manufacturers to deliver the upgraded design. The decision to maintain engine dimensions constant also ensures compatibility with existing ship designs that utilise MAN S35ME-B engines.

In its various permutations and five- to eight-cylinder configurations, the engine spans a power band from 2,775kW to 6,960kW.

Although the 350mm-bore family in its S35ME-CR9.7 common-rail version provides for dual-fuel applications, the S35ME-B9.7 is purely a diesel engine, whereas the S35ME-C9.7 offers scope for substantially extending the fuelling options obtainable at this lower end of MAN’s two-stroke power portfolio. The plan is to make the engine available for diesel (DI), gas (GI) and liquefied petroleum gas (LGIP) operation, and to later expand the portfolio with a methanol-capable variant.

In ME-C engines, the timing of the fuel injection and exhaust valve actuation are electronically-controlled, conferring full flexibility for the opening and closing time of the valves at all engine loads. By contrast, only the fuel injection is electronically-controlled in the ME-B series, which retain cam-actuated exhaust valves. For a standard, high-load optimised engine, the lowest SFOC for the ME-C engines is obtained at about 70% of maximum continuous rating, rather than at 80% in the ME-B type.

The LGIP model is expected to be ready for production by the end of 2020, and subsequent manufacture of the GI and LGIM types will take place in accordance with market requirements, according to the company.

The Motorship notes that the extension of MAN ES’ LPG-fuelled portfolio to encompass 350mm bore vessels, such as general purpose vessels, smaller bulkers and smaller tankers is particularly interesting given the focus on developing solutions for ‘hard to decarbonise’ tramp segments of the deep sea fleet.

The heritage and continuing popularity of MAN’s 350mm-bore two-stroke family date back to 1982 when the L35MC engine arrived with a rating of 500kW per cylinder at 200rpm. After a succession of design revisions, including a longer stroke and upratings at lower revolutions, the first production model of the electronically-controlled S35ME-B was rolled out of the Frederikshavn plant in Denmark during 2008.

PRINCIPAL PARTICULARS – MAN S35ME-C9.7 engine