Feature 2 | PROPELLERS & THRUSTERS
Azipod design reflects unerring drive for efficiency gains
Since the market introduction of the Azipod concept during the late 1980s, the propulsion’s hydrodynamic efficiency has been continually improved, and the unerring drive for further gains in performance is reflected in new refinements involving both pod design and operating systems.
ships Elation and Paradise commissioned in 1998, effectively the start point for the system’s widespread adoption in large, luxury cruise vessel newbuilds, drew on favourable technical comparisons. From full-scale measurements with earlier sisterships incorporating traditional shaſtlines and propellers, it was demonstrated that the Azipod-fitted Elation and Paradise offered an increase of some 9% in propulsion efficiency. “Since then, we have improved the
T
system by another 9%,” said Jukka Varis, ABB Marine’s vice-president for product management propulsion products, in charge of Azipod R&D. This enhancement has been achieved
over time through modifications to the design, including the use of a fin under the pod, changes in the shape of the unit, and by hydrodynamic optimisation of the positioning and angular placement of the pods once integrated with the hull. The improvement process has most recently been encapsulated in the Next Generation Azipod, launched in 2008 under the Azipod XO brand, which achieves a 1.5%-2% rise in hydrodynamic efficiency relative to the most highly optimised models of the first generation. Te technical evolution of Azipod has
thereby delivered an overall progression of some 18% in propulsion efficiency in relation to conventional shaftlines at the time when the first systems were ordered for Elation and Paradise in the mid 1990s. However, acknowledging that shaſtline electrical propulsion systems have also increased in efficacy over this period, ABB has reviewed the basis for its calculations.
36
Azipod’s new-generation XO series of electric podded propulsion systems signals an advance in efficiency.
“Missing in our equation was the
improvement in shaftlines during this time. We obtained some results from our clients, but we decided also to compare shaftlines with Azipod propulsion ourselves, tests,”
explained Mr Varis.
through model “These
tests, conducted last year by Marin, in Te Netherlands, showed that Azipod propulsion, compared to the latest fixed shaftline propulsion designs, still has a 6%-8% lead as regards propulsion efficiency,” he said. Te improved hydrodynamic efficiency
displayed by Azipod-equipped ships compared with vessels equipped with traditional shaftline propulsion stems from several factors. The elimination of long shaftlines, brackets and stern thrusters, and simplification of
the
associated hull design, makes for reduced hull resistance. As a ‘pulling’ unit, the Azipod propeller functions in an optimum environment, where the water inflow to the propeller is undisturbed, due to the absence of any shaſt support appendages in front of the propeller. Moreover, the flexibility afforded
by the Azipod units allows the ship designer freedom and precision as to the location of the propulsors on the hull so as to achieve maximum hydrodynamic efficiency. A new initiative by the Finnish group
has been to enter into a joint research and development study with compatriot company Eniram to optimise the energy efficiency of Azipod installations. Te result is a product known as the Azipod Dynamic Optimizer(ADO), designed to
The Naval Architect July/August 2011
he seminal installation of Azipod azimuthing podded electric propulsors on the Carnival cruise
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68