Azimuthing Propulsion in Ice Management

Year-round operations in ice covered areas result in increasing need for specially designed icebreaking vessels. An important characteristic of these vessels is their ice management capabilities. Azimuth thruster propeller wake can be effectively used in ice management (IM) both in stationary Dynamic Positioning (DP) operation and icebreaking. The ice management performance depends on the thrust of the propeller, propeller wake angle and thickness of the ice. Various ice management experiments have been done both in full-scale and model tests to study and demonstrate IM capabilities. Recent tests were carried out with icebreaker “Polaris”, a Finnish icebreaker with ice class PC4. The novel diesel-electric propulsion system consists of three powerful azimuth propellers, two at the stern and one at the bow. This paper will present results of propeller wake effect on ice management and ice clearing. Ice clearing area depends on the ice thickness, power, heel of the ship and wake angle. This paper will also discuss the characteristics of azimuth propulsion as well as full-scale test results from the use of Azipod units in ice management operations. These results will show how Azimuth propulsion offers improved ice management performance and greater vessel design flexibility. They will also offer further insight into different possibilities, for example, selection of most suitable azimuth angles for various tasks.