Application of Azipod Propulsion on Cruise Liner
Table of Contents
Abstract 3
Manoeuvrability 3
Dynamics 5
Lateral Stability 7
Electric Drive 7
Redundancy 8
Vibrations and noise 8
Conclusion 9
References 10
Abstract
The report examines the key features of Azipod propulsors and estimates its application on a cruise liner. Regarding the experience of large cruise liners operated with fully-steerable podded propulsors, the report discusses possible impact on the ship performance and further improvement. Even though the concept of podded ship powerplants is relatively new and has little empirical data collected, it has already proven its efficiency for large vessels. As it will be shown further on, regardless few concept pitfalls, this type of powerplant is the most preferable for application on a modern cruise liner.
The first installation of Azipod unit (see Picture 1) took place on the arctic tanker by ABB. Its operation shown improvement of manoeuvring and efficiency.
Picture 1. Azipod propulsion (courtesy of ABB)
Operators also appreciate new operating modes that the concept provided. Today, the newest large ships are primarily equipped with Azipods. Fully-steerable podded propulsion system has the following peculiarities to discuss:
Manoeuvrability
Cruise liners are becoming larger, while ports and harbors remains the same. Therefore, the main reason of Azipod introduction to the market of cruise liners was the need for better manoeuvring performance and control in confined area. This type of propulsors provides excellent control in any direction and improves the crash stop performance.
After being equipped with Azipod engines, Elation’s full-speed turning circle became 30 percent smaller, as reported by ABB.
However, the bigger a vessel becomes, the larger is its side area, which makes a ship highly susceptible to influence of side winds. Even though all-turnable pod propulsors are highly versatile, the report of Van Terwisga et al. (2001) states that in order to overcome the wind load, it may be necessary that powerful bow and stern thrusters be installed.
Azipods provide better manoeuvring even in confined area operations with fast and precise control, which eliminates the need for tugboats.
Dynamics
Since the installation of Azipod requires a very flat aft ship, the dynamic performance differs from the one of conventional propulsion arrangement (see Picture 2).
Picture 2. Comparison of aft ship shape (courtesy of MARIN)
This shape is more favourable from the standpoint of hydrodynamic drag, because the less the cross section change is abrupt, the lower the pressure gradient along the hull is. In addition, the flat aft ship results in non-turbulent flow on propellers, which increases their efficiency and delays cavitation.
Aside from that, the flat shape of aft ship gives the freedom to install multiple propulsors. An example here is the Queen Mary II, equipped with four podded Rolls-Royce Mermaid propulsors.
As reported by Van Terwisga et al. (2001), the increment of dynamics efficiency relative to …
