A new version of Wärtsilä’s 460-bore engine claims 52% efficiency.
A new version of the Wärtsilä 46 diesel engine has set “a new fuel economy record in the market for medium-speed engines”, according to Lars Anderson, the OEM’s Director, Product Management & Sales Support.
“Wärtsilä 46TS-DF is the latest addition to Wärtsilä’s portfolio of future proof engines and has been designed to set a new benchmark in efficiency and emissions performance.” “/ /
Wärtsilä 46TS-DF is the latest addition to Wärtsilä’s portfolio of future proof engines and has been designed to set a new benchmark in efficiency and emissions performance.
He was speaking during a webinar in April to launch its 46TS-DF engine, which is fitted with a new design of two-stage turbocharger that helps the engine deliver 52% efficiency in either gas or diesel modes. More important than that, he said, is that “this engine is substantially better over its whole operating range than any other benchmark [engine] in the market”.
In addition, it offers “the lowest CO2 emissions in the segment and a methane slip that is 20% below the market benchmark”, he added. Its efficiency minimises its fuel consumption – “one thing we are certain of is that future fuels will be expensive”, he said – which will improve its OPEX and total cost of ownership, he predicted.
Which fuel emerges as the preferred low-carbon fuel is irrelevant, suggested Stefan Nysjö, Wärtsilä’s Vice President, Power Supply. “We are fuel agnostic and … we will offer the technology owners need whichever fuel they choose”, he said.
The engine platform utilised a modular construction approach, which would simplify production and maintenance, and ease future conversion to alternative fuel types, he said.
It is an approach that Wärtsilä is adopting across its portfolio, he said, initiated by the launch a few weeks earlier of the Wärtsilä 32 methanol engine. He drew attention to the marketing slogan for the new engine, ‘the power to change’, “and with that comes the power to choose”.
Wärtsilä’s Director of R&D and engineering, Juha Kytölä, also stressed the importance of its modular strategy. It provides “consistent quality through less component variance and high commonality between engine versions”.
Valve timing
Stepless valve timing is another development introduced on this engine, on both inlet and exhaust valves. “This system is novel and has not been used in any marine engine in the past”, Mr Kytölä told The Motorship. In the past, valves have been controlled in steps “and for inlet valves only”, he added.
This innovation makes it possible to “adjust the timing of the inlet valve and exhaust valve whilst operating the engine, within a range, in a stepless manner, for each cylinder”, he explained. This optimises air supply and combustion which, together with its two-stage turbocharging (see box) “results in the engine’s superior efficiency”.
Cylinder-level control requires a huge amount of data to be collected and processed in real time, Mr Kytölä told the webinar, which is achieved through a complex automation system, which he described as “the brain of the engine”.
It provides “infinite possibilities to tune the engine”, he said, which not only yield higher efficiency but also optimise the engine’s operation to suit each fuel’s methane number “to optimise operations with variable gas qualities”.
This system is also modular, with each electronic module “software adaptive, which means that when an operator changes a module, it will automatically load software from the other modules”. This, he said, provides protection against cybersecurity threats to the engine.
New turbo boosts power density
For the 46TS-DF engine, Wärtsilä has developed “a completely new turbo charging system that is totally focused on large bore medium speed engines”, according to Wärtsilä’s Director of R&D and engineering, Juha Kytölä.
It is a two-stage arrangement – reflected in the engine’s ‘TS’ suffix – consisting of one low pressure and one high pressure turbocharger arranged in series, combined with two charge air coolers per cylinder bank. “This arrangement allows us to reach extremely high compression ratios and very high turbocharging efficiencies in a very compact design”, he said, which leads to a high power density for the engine.
Yet each turbocharger – made by Napier to a Wärtsilä design – has a relatively small compression ratio, which allows a very robust design and high efficiency across a wide operating field along with very stable performance, he went on. In addition, their rotational parts are relatively small, resulting in low rotor inertia, “which enables very fast load taking”, he said.
It would be technically possible to apply the same turbocharger technology to other engines, according to Federic Bottos, product manager for the 46TS engine family, who said that two stage turbocharging system also helps pure diesel engines reach extreme efficiency and power density, he said, such as the Wärtsilä 31 engine, which has two-stage turbocharging.
But the market at the moment is “focused strongly on dual fuel gas engines that guarantee the best fuel flexibility and the lowest CO2 footprint”, he said. So for now, resources are prioritised towards the dual-fuel version of the engine, “but we are also evaluating development of a pure diesel version of our 46TS as next engine type”, he said.
