CYCLE LEVEL COMBUSTION CONTROL SYSTEM PILOT

Wärtsilä is working with the European Union and other partners to develop a new system that combines flapping bow foils and engine combustion control technology to reduce fuel consumption

The EU-funded SeaTech project began in 2019 with the expectation that the team could combine bow-mounted foils with new, sophisticated control systems for Wärtsilä dual-fuel 31 engines to allow the engines to work in tandem with the foils. This would reduce fuel consumption by up to 30% under ideal conditions – for example, crossing the waves straight on and with the ideal ratio of wavelength versus vessel size - as well as reduce NOx, particulate matter, CO2 and methane emissions.

The pair of bow-mounted foils designed as part of the project exhibit flapping behaviour so that they remain angled to reduce the heave and pitch of a ship as it sails through waves. The energy for that thrust would normally be lostinstead, it is used to provide transient energy to the ship’s power system, reducing engine load.

After first model testing and in-water testing on a small vessel, Jonas Åkerman, Director of Research and Technology Development at Wärtsilä, says the SeaTech Consortium is very pleased with the results and is now evaluating the business cases that could see the combined technology in commercial operation by 2025.

Ultimately, the design will be developed so that the steel foils are retractable. Their size will depend on the vessel’s size, but they will not significantly extend beyond the body of the hull.

The project is initially aimed at short-sea shipping looking to boost efficiency and enhance performance in line with regulations, such as the IMO’s Carbon Intensity Index (CII). Åkerman notes that deep-sea sailing can offer greater potential due to the heavier sea states - for example as experienced In the Atlantic Ocean.

Transient Engine Control

The flapping foil is only one part of the innovation being developed by the SeaTech Consortium partners. A crucial parallel development, which enabled the project to achieve 30% fuel reductions, is the precise combustion control that the researchers have achieved in a Wärtsilä’s four-stroke, dual-fuel engines - the cycle-level optimisation for the transient power changes required to take advantage of the dynamic thrust provided by the foils.

“Due to the constant load variations, our engine optimisation is more efficient than conventional engine controls which are typically rather slow, so you always have non-optimised performance in transient conditions,” says Åkerman. “To achieve the results we have, we have gone further than optimising the engine overall. From a power management point of view, we have gone deeper into the engine, and the resulting optimisation could only be achieved because of the advanced engine concepts we already employ.”

The results achieved through the combined system of foils and optimised engine timing and combustion control will vary depending on the size of the vessel in relation to the waves. If the vessel is over-sized or under-sized compared to the waves, it is more difficult to make use of the energy released through the motion dampening to reduce fuel consumption.

Åkerman is initially targeting the short-sea and offshore support vessel markets – ones he sees as fast and flexible in their uptake of new technologies. However, he is keen to see the benefits adopted across the commercial fleet. With the three-year project drawing to a close, the business cases are still being finalised.

Meanwhile, Wärtsilä is pushing ahead with a pilot installation for the new engine control system before a commercial launch. While the Wärtsilä 31 engine model has been the initial focus, Åkerman expects it to be rolled out successfully to others.

Foil Concept History

The concept of bow-mounted foils dates back to 1858. Early experimentation included both bow and stern foils, with fullscale trials commencing in the 1970s. Some attempts suffered from structural problems; in others the trial results did not match theoretical expectations.

In 2009, Liquid Robotics developed a commercial, wavepropelled autonomous surface vessel using a set of tethered, submerged foils driven by wave-induced heave motion. A full-scale trail of composite bow foils was conducted on a 45-metre ferry by Wavefoil AS in 2019 with EU funding. Wavefoil’s solution has been installed on several vessels, and the company claims 5-15% fuel reduction, with higher reductions in optimal conditions. The non-flapping foils are retracted during very heavy and very calm conditions. In December 2022, Wavefoil received a grant from the Research Council of Norway to develop a new bow foil solution for ocean-going vessels sailing at low speed.