Ice Load Impact on the Power Train of Azimuth Propulsion Systems

Abstract

This thesis seeks to investigate the advantages of using multibody simulation to develop proper models for power train analyses of azimuth propulsion systems. Azimuth thrusters are commonly installed on ice classed offshore vessels and icebreakers, and are hence exposed to extreme ice loads. This poses a risk for safe operation. It is therefore of great interest to study in detail how these impulse loads affect the system components.A multibody simulation model of a Rolls-Royce Azipull thruster has been developed in SIMPACK version 9.6, comprising the electrical motor, shafts, bearings, bevel gear transmissions and the propeller. It is a decoupled analysis, i.e. the propulsion system is assumed to have no feedback to the environmental load or the electrical motor. The ice load is based on the IACS Polar Class code.The results reveal that multibody simulation in SIMPACK is well suited for dynamic analyses of azimuth propulsion systems. It is an efficient tool for developing detailed models and comprises strong solver capabilities. Furthermore, it can be concluded that all components of the propulsion line are to some extent, experiencing the ice load. The gear contact forces increase significantly during the ice-propeller interaction, and the gear forces cause the load on the surrounding bearings to increase accordingly. The bearing closest to the propeller is by far most prone to the extreme ice load.Verification of the model parameters and further improvement of the global analysis will increase the validity of the results.