Propulsion Machinery Operating In Ice - A Modelling And Simulation Approach

Shipping activity and offshore operations in Arctic areas are increasing as a result of more effective transportation routes and oil/gas exploration. Vessels navigating in ice covered areas are exposed to additional loads from different ice conditions. In this paper the dynamic loads on propellers are investigated to better understand the impact on propeller, power transmission elements and engine. An ice-propeller interaction model is implemented with a full propulsion machinery to simulate the systems response to ice loads. The ice load models are developed based on the DNV and IACS rules for ice-propellers. Modelling and simulation of interactive multi body systems is a rather complex task, involving hydrodynamics, mechanics, electronics and control systems. This paper describes an approach to link the different models to simulate the overall system response and the interactions between the sub-systems. Therein, the rule-based ice loads are implemented in two ways for comparison: a) a coupled and b) an uncoupled treatment of the ice load and system response. The simulation results show that the dynamic peak loads are 10-20% lower than the maximum peaks predicted by the uncoupled simulation, i.e. conventional rule-based. Simulations also show that the peak loads are damped through the transmission elements, and therefore reducing the load on critical machinery components.