W31 engine – properties, some technical details and first experiences

Risto Lejon, Wärtsilä, Finnland

One of the strongest drivers today is environmental sustainability with emissions and efficiency being the key contributors in energy production. In future, engines will be used in combinations with new technologies in different kind of applications and changing the overall landscape on how the power is produced. There are clear indications in both marine and energy market to turn more and more using alternatives fuels e.g. gas. Also hybrid solutions with engines and batteries will become more increasingly used in short and fixed route operations and in larger installations the internal combustion engine will still be there for decades to come as the most efficient source of power. Uptime and people safety remains to be high on agenda for all segments which translates to system availability at all times. This will have cost implications for owners and operators as there is no substitute for high reliability of the equipment on-board of the vessel or at the power-plant. This trend is also expected to continue when unmanned operation of ships will become reality. Engines of tomorrow must be self-tuning, they must share data with on-shore offices and they cannot have a lot of short time maintenance needs. As for power-plant installations, this is already more or less standard setup.  

At 1960 internal combustion engines produced firing pressures of just above 50 bar, with break mean effective pressures of 7 bar having shaft efficiencies around 30%. In 2020 the internal combustion engine will still be one of the most energy efficient energy conversion machines having power density (BMEP) over 30 bar which is close to 500 % increase during 60 years of development and showing shaft efficiencies close and above 50%. Flexibility of an engine operation translates to capability to run with different type of fuels, operation with different load areas and to cope with ambient conditions like hot or cold, dry or humid and many other aspects. Flexibility however requires quite a lot from the engine design and also proper automation system to react on changing conditions. The variation of oil price is naturally perhaps the strongest driver of all for total cost of ownership. The choices are many, how much operation takes place in NOx Emission Controlled Areas (NECA’s) and how much in other areas. What fuel to use; HFO, ULSFO, Gas (LNG, LEG, LPG) or other alternative fuels. However, the better engine efficiency there is on board or at plant level, the better gain at the operator, owner side there is. 

The Wärtsilä 31 is setting a new standard for energy efficiency, delivering the lowest level of fuel consumption of any four-stroke engine. It also offers operational flexibility and can easily be adapted to different fuel types and operating profiles. The Wärtsilä 31 is not one single engine, but rather a platform consisting of three different products – a diesel engine, a gas engine and a dual-fuel engine. The brand-new Wärtsilä 31 not only complies with the existing IMO Tier II emission standard, it also meets the IMO Tier III legislation. With the dual-fuel version, it can operate on diesel in a Tier II area and easily switch to gas when entering e.g. Emission Control Area. The switch is instantaneous – there’s no need to wait for the change-over – the vessel can carry on sailing at the same speed. Wärtsilä 31 exceptional fuel efficiency is made possible through the use of new technologies, such as two-stage turbocharging, a high-pressure fuel injection system and adjustable valve actuation, in combination with the next-generation engine control system. The internal combustion engine technology for the Wärtsilä 31 enables you to take technology leaps and gain three-to-five percent better efficiency than the previous generation of engines, and even more than that at part loads. Wärtsilä 31 is making its entrance in to operation when today there are around 30 engines ordered for the marine side. With the Wärtsilä 31 our focus is also on offshore, when it returns to its heyday, the Wärtsilä 31 will be a key product driving it. Not only we have seen marine market showing their interest but also land based, where the first power plant was sold in January 2018 with more interesting projects following that deal.