Transient torsional vibration analysis of Polar-Class propulsion shafting systems under ice-propeller interaction loads

• Main Author: Zambon, Alessandro
• Format: Thesis
• Language: English
• Published: Memorial University of Newfoundland 2022
• Subjects: Icebreaker; Sea ice
• Online Access: https://research.library.mun.ca/15518/; https://research.library.mun.ca/15518/1/thesis.pdf

The design of propulsion plants for Polar-Class vessels has to ensure the safety and preservation of ship operations in sea ice environments. In particular, the effects of ice-propeller interaction on shafting segments constitute a potential hazard for the integrity of the entire propulsion system. Collisions of ice blocks with propeller blades induce high torsional vibrations along shaft lines and cause the prime mover’s output torque to fluctuate abruptly. These processes also undermine ships’ propulsion efficiency and manoeuvring capability during ice breaking expeditions, as well as during ice navigation of commercial vessels and offshore operations. Consequently, the development of effective design methods dedicated to the dynamics of ship propulsion systems is fundamental to simulate the effects of ice-induced loads correctly. To this end, full-scale measurements have proven essential to support the evolution of robust design criteria and updated regulatory guidelines. The research activity presented in this doctoral thesis aims to accomplish two objectives: firstly, delivering a modelling methodology to simulate the propulsion shaft lines of Polar-Class vessels, or the analysis of the torsional dynamic response caused by ice- propeller interaction processes; secondly, providing indications about the mathematical characterization of the ice-propeller torque pattern. The research project includes full-scale measurements conducted aboard the two Canadian Coast Guard icebreakers Henry Larsen and Terry Fox. Torsional vibration data acquired from CCGS Terry Fox’s shaft lines validate an original mathematical model to simulate the dynamic torque delivered by Diesel engines. Besides, an innovative integrated measurement system is installed aboard CCGS Henry Larsen icebreaker to achieve concurrent monitoring of the shafts’ dynamic response, sea ice conditions, and propulsive performance. The experimental measures obtained in open-water navigation are employed to validate the numerical models of both vessels’ shaft ...