Back to search

MAROFF-2-Maritim virksomhet og offsh-2

Low energy ships by combining innovative air-lubrication solutions with environmentally friendly anti-fouling coating

Alternative title: Kombinere luftsmøring og miljøvennlig begroingshindrende maling for å redusere skipets energiforbruk

Awarded: NOK 15.0 mill.

Project Number:

317869

Project Period:

2021 - 2024

Organisation:

Air-lubrication with its high potential for decreasing the drag of ships has been getting more and more in focus recently. An air-lubrication system injects air underneath the hull, reducing the density of the fluid and reducing the friction. Passive air-lubrication system can be used for small ships at higher speed (>20 knots) while active air-lubrication compressing air before injecting are used for large vessels. The main goal is to optimize the air-lubrication system coating interaction to increase the air-lubrication system efficiency. The project will combine phenomenological studies using experimental equipment of SINTEF Ocean with full-scale studies on ferries with a controlled voyage factor, equipped with air-lubrication systems. Two main topics will be addressed and investigated in an interactive way. (1) Air-lubrication is changing the condition under the hull from wet to partially dry. This also changes the target properties of an anti-fouling paint surface. Fouling might be reduced, and the target property of the paint should be redirected towards the active support of the air-layer formation and reduce the necessary air-injection rate. Hydrodynamic measurements are needed, as well as full scale application to study fouling development and performance. The research will help in targeting essential surface properties to enable a paint development for this special condition. (2) Different air-lubrication systems will be evaluated and studied; Micro-bubble systems and full air-layer systems, passive and active. An existing passive air lubrication system will be optimised based on the phenomenological insights gained in the experiments. In addition, the effect of waves and ship motion on the system will be investigated. The interaction of an air lubrication system with the propeller, radiated noise and vibrations will be studied. A projection will be made for possible savings by the world fleet if air lubrication and custom coatings are used. Full-scale trials were performed with a candidate vessel equipped with a passive air lubrication system. Underwater videos from these trials provide valuable insight in working principle of the system. At the same time potential for further development become clear. Numerical simulations of the vessel (without air lubrication) show pressure and flow characteristics around the vessel that are important for optimal functioning of the system. Laboratory tests in the SINTEF Ocean cavitation tunnel with air lubricated plates show good agreement with full scale observations.

The project is based on the increasing interest in air-lubrication systems and the high potential for optimisation to decrease further skin-friction and consequently greenhouse gas GHG-emission. To reach the goal of an optimization of the air-lubrication system and coating interaction, a better understanding of the air-bubble surface interaction is needed. Therefore, the project combines phenomenological studies in the cavitation tunnel at SINTEF Ocean with full-scale studies of ferries equipped with an air lubrication system with a steady and controlled voyage factor. Two main topics will be addressed and executed in an interactive way. (1) Air-lubrication is changing the condition under the hull from wet to partially dry. This changes also the target properties of an anti-fouling paint surface. Fouling might be reduced, and the target property of the paint should be redirected towards the active support of the air-layer formation and reduce the necessary air-injection rate. Hydrodynamic measurements under air-lubrication are needed as well as full scale application to study fouling development and full scale data. The research will help in targeting essential surface properties to enable a paint development for this special condition. (2) Different air-lubrication systems will be evaluated and studied, from micro-bubble systems to full air-layer systems, passive and active. An existing passive air lubrication system will be optimised based on the phenomenological insights gained in the cavitation tunnel. Effect of waves and ship motion on the system will be investigated. Interaction of air lubrication system with the propeller and radiated noise and vibrations will be studied. Projection will be made for possible savings of world fleet if air lubrication and custom coatings are used.

Funding scheme:

MAROFF-2-Maritim virksomhet og offsh-2