Design strategy for propellers for sailing freighters developed
Wind-powered freighters must be able to be driven by machinery to varying degrees. This requires a completely new type of propeller. Within the Swedish Transport Administration's program Sustainable shipping, which Lighthouse runs, an optimization method has been developed which will be used in Kongsberg's design of propellers.
Two years ago, Wallenius Wilhelmsen presented Orcelle Wind – a wind-powered car carrier to be built and in service in 2027. The ship is based on the Oceanbird concept, which was developed with the support of the Swedish Transport Administration by Lighthouse members Wallenius Marine, KTH and RISE.
At SSPA, Sofia Werner is one of several researchers working with Oceanbird. Among other things, she has worked with the three-year innovation project SAILPROP - even sailing cargo ships need an energy-efficient propeller, the final report of which has just been completed.
“Even if the RoRo ships with wing sails mostly sail, they will still need an engine on days with too little wind, when you have to enter a port or if you need to quickly maneuver away from something, e.g. bad weather or a foundation”, she says.
It requires a propeller that, unlike ordinary propellers, works optimally in several different loads – from low power to help when the wind is not sufficient to high power when there is no wind at all. How it works best has never been investigated before.
“ Its a challenge. Because if you optimize the propeller in one position, it will be worse in another. So the question is how do you find the right compromise so that it works best all-round? To achieve that, we have taken into account new parameters, for example how the wind usually is and how the wing sail will work on the route the ship is intended for.”
The "innovation" developed in the project is an interactive design and optimization methodology that Kongsberg will use in the manufacture of the propellers. On wind-sailing ships, they will have rotatable blades, making them more flexible and adaptable to different loads.
Within the project, tests have also been carried out on an already existing tanker with six Flettner rotor sails, a so-called wind-assisted vessel where the wind supports the engine and saves 5-10 percent fuel consumption. But it was concluded that replacing and optimizing the propeller would not yield any major gains.
Sailprop - Even sailing vessels need an efficient propeller was written by:
Ioli Gypa (Chalmers), Sofia Werner (RISE) and Rickard Bensow (Chalmers) in collaboration with Robert Gustafsson and Marcus Jansson (Kongsberg Maritime) and Carl Fagergren (Wallenius Marine).