Analysis of Azipod Propulsion: Application on Cruise Liner
Table of Contents
Historical Background 3
Cruise Liner Powerplant Requirements 3
Advantages of Azipod Concept 4
Electric Motor Power Delivery 4
Enhanced Manoeuvring Capability 4
Design Simplicity 5
Easy Maintenance 6
High Efficiency 6
Increased Payload 7
Reduced Vibrations and Noise 7
Environmental Impact 7
Azipod (short for azimuthing electric podded drive) is a podded electric thruster with a fixed-pitch propeller. It can rotate 360 degrees about the vertical axis and thus provide propulsion in any direction. This paper gives an insight of the advantages provided by the concept of a fully-rotating, azimuthal independent electric-driven propulsion unit. In the beginning is given a short description of the reason why Azipod systems are widely used today for large ships and the development history of this concept. Based on the benefits of podded thrusters, the summary of the discussion is presented in the end.
The origin of Azipod systems is traced from icebreakers and thus comes from their operating problems. Electric motors have been preferred for severe icing conditions since the very beginning, because they ensure high propeller torque at low speeds of rotation, which is essential feature for icebreakers. Also, the podded propulsor unique feature is to provide thrust in any direction, which significantly improved the performance of icebreakers in confined iced area. Since 1983, ABB has supplied Azipod propulsion systems for total 40 icebreakers.
Gathered experience has proven the effectiveness of such drivetrains in various icebreaking operations. Then, this experience was translated into the development and optimization of the concept for other types of large vessels, such as cruise liners.
For modern cruise ships, this propulsion system has thus become omnipresent.
Cruise Liner Powerplant Requirements
The design goals for large cruise ships can be summarized by the following list:
Low environment impact
High manoeuvrability in confined area
Low noise and vibrations
Based on this list, the following paragraph depicts the advantages of Azipod system taking into account the most important of listed requirements.
Advantages of Azipod Concept
Electric Motor Power Delivery
A modern AC electric motor can be designed so that maximum torque can be directed to a propeller from the very first revolution of its rotor. As opposed to that, the torque of a stationary internal combustion engine is zero. There is no mechanical connection between the power plant and the electric motor driving the propeller. Thus, it is possible to have as many available power steps as necessary. In this case, the diesel engines can be run close to the point of their maximum efficiency. This reduces fuel consumption and improves the environmental behaviour of the powerplant.
Enhanced Manoeuvring Capability
One of the biggest problems with the conventional shaft line is the manoeuvrability in restricted area. Azipod system was created for the certain purpose to improve manoeuvring characteristics of icebreakers. A turning unit allowed the thrust to …