European companies combine efforts on gas-fuelled two-stroke project

31 Jan 2014
The research engine at MAN’s diesel research centre in Copenhagen

The research engine at MAN’s diesel research centre in Copenhagen

In November 2013, MAN Diesel & Turbo hosted a one-day conference at its PrimeServ Academy in Copenhagen, Denmark, to announce results so far of the EU-assisted Helios project, for which MAN has responsibility for coordination.

Helios is a research project within the EU´s 7th Framework programme for Research and Technical Development/Transportation, with the general objective of developing a range of gas-fuelled electronically controlled two-stroke low speed marine diesel engines. The project is concentrating primarily on large engines fuelled by methane gas, in either liquefied natural gas (LNG) or compressed natural gas (CNG) forms. The gas system is based on the MAN ME-GI engine, which uses high pressure. The project began with a meeting in February 2011 and is scheduled to last for three years, so the results presented at the conference were near to final for this phase of the research.

There are nine partners in the project, including MAN Diesel & Turbo. Other well known names from the industry include Germanischer Lloyd, Kistler Instruments. TGE, Sandvik and the line-up is completed by four universities, Erlanger, Jonkoping, Lund and Uppsala. The decision was made at the outset to base the project around Diesel cycle operation, rather than the Otto cycle of most four-stroke gas engines and low-pressure two strokes, to allow the flexibility to operate on all grades of gas as well as liquid fuels. This requires a gas injection system working at around 300dpi, with direct gas injection at a pressure higher than that of the combustion pressure, and a small amount of pilot fuel. The system is additionally believed to offer safety benefits, with only a small amount of gas in the engine room.

Introducing the project, Lars Juliussen, senior manager at MAN’s research centre, said that the concept was originally thought to appeal initially to propulsion of gas tankers, although it could apply to any type of ship. It was somewhat surprising that the first orders received for the engine were for container ships, from North American operators, no doubt driven by the anticipated low cost and plentiful supply of shale gas in the US. He explained that Helios, which benefited from around €3million of EU funding, was divided into 10 elements: the test engine, the onboard gas system, the drive for zero emissions, development of high temperature components, gas engine tuning, cylinder pressure, emissions compliance, optical diagnosis, piston rings and gas sensors.

As well as MAN’s own four-cylinder 50cm bore research engine, which had been fitted with gas equipment to ME-GI specification, further tests and demonstrations have been carried out at licensees Hyundai and Mitsui on actual S70ME-C-GI engines. One of the aims of the project was that existing engines could be comparatively simply retrofitted with the gas systems and gas injection equipment, and as well as the on-engine equipment and the associated control and safety systems, the project looked at – on the ship itself - safety criteria for placing of gas tanks, and – on shore – the bunkering, infrastructure and political considerations of encouraging the adoption of LNG as fuel..

MAN research engineer Michael Johnsen Kryger outlined the practical experience gained on the test bed with the first gas-fitted engines. MAN’s experience of gas-fuelled engines dates back to the 1990s, he said, including the 12K80MC-GI-S low speed engine at the Chiba power plant, which operated for some 20,000 hours. For the latest generation, safety was of paramount consideration and the high-pressure gas installation employs double-wall piping with ventilation system, a sealing oil system, and hydraulic application of all valves within the gas block. The fuel gas system is based on that developed by DSME. It is currently running on less than 5% pilot fuel, with the ability to run on gas at loads of under 10% MCR, and offers very low methane slip and transient response has been confirmed as very close to that of an engine running on diesel fuel alone.

Although the engine has been proven to meet IMO Tier II as it stands, it has been found to exceed Tier III limits with the addition of exhaust gas recirculation (EGR). With further research into reducing the amount of pilot fuel – close to 1% is considered feasible - and with customer experience, it may be possible to achieve Tier III figures without EGR, but this is likely to incur a small penalty in fuel consumption.

Uppsala University was tasked with investigations into anticipated piston ring wear problems with virtually sulphur-free fuel. Various scuffing tests were set up and although no firm conclusions could be drawn it seemed that both high velocity oxy-fuel (HVOF) Cermet and stellite materials were highly suitable for gas fuelled engines. The most important factor was to maintain lubrication, with an oil film of as little as 1μm proving sufficient to prevent scuffing.

Benjamin Scholz of GL (now DNV GL of course) explained the background to the use of LNG and the criteria relating to safety of the high pressure onboard gas supply system. The critical point is to avoid release of HP gas in the case of a shut down or fault. Although the individual system components are all proven, this is the first time they have been used together in such a safety-critical application. Because of the importance of avoiding cavitation, LP priming pumps are vital and these could advantageously be housed within the storage tanks. Extensive studies and simulations had been undertaken to investigate and avoid cavitation. Similarly, it was important that the effect of damage to pipes, and the effectiveness of the double-wall containment system, was fully assessed. The conclusion was that LNG fuel is financially and technically viable, and technology exists to ensure that it can be applied safely.

Mette Dybkjær of the Danish Maritime Authority gave the results of the project’s investigation into setting up the LNG supply infrastructure, both in Northern Europe, where the DMA had already instigated a project, which included the Fjord Line ferries, and subsequently in the rest of Europe, under the EU framework. Driven by the 2015 ECA sulphur limits, LNG is a viable solution, as long as the supply and bunkering system is in place and owners can be persuaded to adopt it. Ms Dybkjær said that most owners were, understandably, adopting the ‘wait and see’ approach, but practical moves are in place to ensure that LNG can be provided at the right cost and in the right places when the owners need it.

Those attending the conference had the opportunity to visit the MAN Diesel Research Centre to see the ME-GI research engine, and its gas system, in the flesh. It is clear that as far as the engine itself is concerned, it can be adapted to run on gas comparatively simply, but the fuel and safety systems add a lot to the complexity, and hence the upfront cost.

MAN’s ME-GI promotion manager, René Sejer Laursen, presented the company’s view on the market for gas fuelled ships, driven by demand from the market for more efficient and cleaner ships with lower overall costs. LNG occupies a strong position in the future market, and is gaining ground overall, alongside other low flashpoint alternative fuels, and its adoption will be dependent on ship type, area of operation, and operating pattern. Experience so far suggests that the ME-GI technology will offer the expected commercial and environmental benefits while remaining fully flexible in the type of fuel – i.e. high or low methane number gas as well as liquid fuel oils – that it is capable of burning.

According to Per-Magne Einang, research director at Norwegian research organisation Marintek, Norway has assumed a leading position in marine gas and dual fuel engines, with most of the gas-fuelled ships currently afloat. Norwegian ship design has a leading position in the gas fuelled ship market. Although there is potential for lower fuel costs using LNG, gas fuelled ships do cost significantly more to build. In Norway this has been offset by official incentives, such as the NOx fund which has contributed to most of the projects so far.

The conference was rounded off by an owner’s view of the challenges and possibilities of LNG as ship fuel, in a presentation by Stavros Hatzigrigoris, MD of Greek company Maran Tankers. As an owner, there was little incentive for change unless alternative fuels become more attractive on grounds of cost and necessary to meet legislation. On both of these counts LNG is the most attractive alternative fuel.

Currently, there is a lack of standardisation in bunkering requirements, but these are said to be on their way, in terms of EU standards and a forthcoming ISO specification developed with OGP (the international oil & gas producers). LNG looks attractive from a cost point of view, certainly less than MGO and in some areas on a par with, or even cheaper than, HFO. But there are large geographical variations in price, and costs have been variable, due to the lack of commercialisation of LNG at the scale dictated by likely bunkering requirements. Availability in European ports is either assured or in developments, so there is no great problem there. With firm plans or well-advanced studies covering Korea, Singapore, the UAE and the US then LNG prospects look promising worldwide. And although the technology can be regarded as mature, there are still health and safety issues and crew training and competence is likely to emerge as a major issue. Although a lot of work is involved, then retrofitting existing ships to operate on LNG is possible.

So, concluded Mr Hatzigrigoris, LNG is definitely worth considering, particularly if a ship spends more than about 20% of its time in ECAs. It is not the only answer, bunkering needs further development and consideration, and getting the costs at a sustainable, stable, level will be the key to its adoption.

The final remarks from Mr Juliussen emphasised that a lot has been achieved over the three year period in terms of knowledge and experience, proving not only the basic concept but the scope for further development and improvement.

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