Research On The Propeller Strength Of Ice-going Ships

Nowadays,ice-going ships becoming more and more vital for the utilization of Arctic Passage as well as the oil and gas resources in Arctic. However,sea-ice is a hidden danger for the ships navigate in ice-infested waters. Therefore, researching about the strength of propeller under the affect of sea-ice is significant for the navigation safety of ice-going ships.This thesis analyzed the distribution of stress on propeller in different conditions including the factors influence propeller's stress. The results of the research also provide guidance for designing and structural strengthening of ice class propellers.Firstly, this thesis computed the design loads of an ice class propeller according to the ice class rules issued by International Association of Classification Societies,and analyzed the strength of the propeller under 5 load conditions.To further discuss the influencing factors of ice load, influential parametric study of the propeller-ice load in blockage, impact and milling conditions were conducted. With the fluid-structure interaction analyze function of Ansys Workbench, this thesis gives the propeller's performance in blockage condition.The result shows that the load of propeller presents periodical change. Surface pressure and stress of blade in wake flow of sea-ice changes obviously. The thrust force and torque of the propeller also change periodically. The blockage effect of sea-ice not only increases the thrust and torque of propeller, but also has effect on its fatigue strength.For the condition of impact and milling, fluid-structure interaction analyze with LS-DYNA was carried out. It revealed the extreme load act on blade during propeller-ice impact. The contact area is mainly around the leading edge of the blade, agreed with the result of result of IACS ice class rules. Meanwhile, there is stress concentration near the blade edge at contact area, which harms structural strength of the blade.When propeller is milling the ice, the contact zone is concentrated in the tip of the blade,same as the load area of condition 2 and condition 4 of ice class rules of IACS. The max von-mass stress of propeller during contact also occurred at the tip of propeller. For propeller ice contact conditions, the contact load is the majority part of the total load. As the load in milling conditions is larger than that in impact conditions, milling condition is the most dangerous condition of propeller-ice interaction.Besides, the analysis indicates the influence of different factors such as operating conditions and parameters of ice, providing references for the strength assessment of ice class propellers, which is instructive and meaningful to the design of ice class propellers.