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Diesel is far from dead17 Mar 2014Wärtsilä low-pressure two stroke gas engine, using both Diesel and Otto cyclesWärtsilä low-pressure two stroke gas engine, using both Diesel and Otto cyclesAlthough alternatives are looking increasingly attractive, Lloyd’s Register believes that the trusted traditional two-stroke diesel engine will continue to be the first choice in large ship propulsion for many years to come.Despite environmental influences and a growing range of alternative power options, the traditional diesel engine will continue to be the industry mainstay for many years to come, says Ed Fort, Lloyd’s Register’s Head of Marine Engineering ServicesOther fuels and engine configurations may offer solutions to the ‘Diesel dilemma’, but classification society Lloyd’s Register sees the industry’s workhorse, the low-speed marine diesel engine, continuing to be specified for future generations. The Diesel dilemma - rigorous environmental legislation and ever-increasing fuel costs - has focused attentions on the alternatives, and perhaps lost sight of the large two-stroke diesel’s main advantages, which have brought it to the forefront of its field. Its inherent simplicity masks an underlying ingenuity in its capability to converting the leftovers of today’s oil refining industry into highly reliable propulsion power. The fact that its does this more efficiently than any other internal combustion engine currently operating should not be forgotten.Applying current and future environmental legislation to this traditional technology is not without its difficulties. Attempts to reduce NOx emissions lead to an increase in fuel consumption, and with it a corresponding increase in greenhouse gases. Exhaust gas recirculation (EGR), and after-treatment, such as selective catalytic reduction (SCR), offer potential solutions, says Ed Fort, head of marine engineering services at Lloyd’s Register, but according to Mr Fort: “Our simple, reliable and highly efficient workhorse is beginning to look like a very different animal now; one that is much more temperamental and demanding.”Among the promising alternatives, according to Lloyd’s Register, are low flashpoint fuels. These can offer reductions in SOx and CO2 in engines that differ little from traditional diesel technology, Combining these fuels with lean-burn technology will cut NOx emissions too. As long as these fuels can be safely managed, they could play a significant role in meeting the challenges of sustainable shipping. The way is now open for using these fuels in large two-strokes, with MAN Diesel & Turbo’s ME-LGI (liquid gas injection) technology, which can be retrofitted to existing ME series engines. Orders have been received for the first such engines, which will run on methanol (MeOH). The engines can additionally use liquefied petroleum gas (LPG), dimethylether (DME) and ethanol. Lloyd’s Register granted AIP (approval in principle) for the ME-LGI operating on LPG early in 2013 and has recently granted AIP for operation on ethane.LNG-fuelled and dual fuel four-stroke engines have become established in the industry, with type approval from class societies including Lloyd’s Register, and many examples in successful operation in class-approved vessels. Development is continuing, as typified by Lloyd’s Register and Rolls-Royce cooperating in analysing the design of the Bergen B and C series gas engines, with the aim of demonstrating equivalent reliability to that provided by conventional oil-fuelled engines.Mr Fort points to the growing order book for dual-fuel two-stroke engines. MAN Diesel & Turbo’s ME-GI series diesel cycle engines operate on both high pressure natural gas and conventional fuel oils. He says that such developments will undoubtedly increase the uptake of LNG as a bunker fuel for environmentally sensitive areas and, with reducing global sulphur limits, worldwide trades. The ME-GI has already received AIP from Lloyd’s Register, and with the introduction of Wärtsilä’s dual fuel two-strokes operating on Otto and Diesel cycles, burning low pressure natural gas or conventional fuel oils respectively. Mr Fort expects the LNG propulsion market to continue to grow.Other low carbon fuels are under consideration. Wärtsilä, in cooperation with Stena Line and Lloyd’s Register, is currently engaged in the conversion of existing diesel engines onboard the Stena Germanica to allow operation on methanol when operating in the diesel cycle and using a pilot fuel for ignition.In the longer term, Lloyd’s Register sees a role for hydrogen, which Mr Fort describes as “the ultimate clean fuel”. This offers the prospect of true zero emission power. While the operation of internal combustion engines on hydrogen is possible – and indeed has been demonstrated – the class society sees it as unlikely that internal combustion technology will extend to operation on hydrogen. Instead, should cost and availability questions be resolved, it sees a role for hydrogen in fuel cells, a technology not constrained by the efficiency limits of the Otto and Diesel thermodynamic cycles and offering significantly higher efficiencies. Lloyd’s Register already has experience of fuel cell technology, from marine and other industries, and is actively evaluating onboard hydrogen generation and low temperature hydrogen fuel cell technology.Mr Fort asks if this wide range of options spells the end for traditional oil fuelled low speed marine diesels, burdened with the weight of emissions after-treatment technologies struggling to trade off emissions against efficiency?“Most definitely not,” he says. “Engineers worldwide are investigating advanced combustion technologies, in order to develop an in-cylinder approach to meeting emissions standards and thus avoiding the need for additional after-treatment systems or, at the very least, reducing the performance demands of the after-treatment systems, thus reducing their cost and complexity. The European Commission (EC) funded Hercules R&D programme aims to reduce fuel consumption of marine diesel engines by 10%; improve efficiency of marine diesel propulsion systems to more than 60%, with a corresponding reduction in CO2 emissions; reduce NOx by 70% and particulate matter (PM) by 50% by 2020. In order to meet such aims, the programme will equip the marine industry with the tools necessary to model and validate in-cylinder combustion processes for various arrangements and advanced low temperature combustion (LTC) concepts.”Lloyd’s Register is a partner in Hercules, and considers that LTC concepts will lead to advanced fuel injection systems, providing injection pressures as high as 3000 bar, and multi-stage turbo chargers to achieve the necessary boost pressures. Which points to a secure future for the simple, efficient, and proven Diesel engine.