propulsors
Further advances in Azipod propulsive efficiency
Recent refinements to the Azipod propulsor frame design have improved hydrodynamic efficiency by more than two per cent, ABB Marine reports
by Doug Woodyard N the
ewly introduced modifications to the Azipod propulsor frame include an optimised Azipod fin shape and a new pod cap structure (termed X-tail). The revised fin structure receives water flow from the propeller at a less acute angle than before, and its new curved design redirects the flow more efficiently. The X-tail installed on the pod cap straightens water flow on ejection from the propulsor, minimising water swirling. Royal Caribbean’s Radiance of the Seas was first
cruise ship to benefit from the
new fin shape and X-tail, the modifications to the existing Azipod completed during a drydocking last May. Subsequent voyages demonstrated the merits over a sistership installation and over previous sailings. An improvement of more than two per cent in hydrodynamic efficiency was achieved. Positive results from the test have encouraged ABB to incorporate the features in new Azipod XO units as well as offering retrofits to tonnage equipped with older Azipod VO and XO installations.
Early in 2011 ABB co-operated with Finnish company Eniram to introduce the
Azipod Dynamic Optimiser (ADO), a software tool which optimises the propulsor’s toe angle. The tool has further improved unit efficiency, with initial results from a trial installation on Holland America Line’s cruise vessel Noordam indicating that 1.5 per cent savings may be achievable in that application. “Azipod propulsion has been on the market for around 20 years and a lot of hydrodynamic improvements have
been made during
that time,” notes Tomi Veikonheimo, ABB Marine’s chief hydrodynamist. “However, from the hydrodynamic viewpoint the system still has considerable potential. More new ideas will be studied, tested and applied to improve fuel efficiency.” When first introduced to the cruise ship
market in the 1990s, Azipod propulsion recorded around an eight per cent rise in shaftline efficiency compared with existing
vessels. Subsequent step-by-step advances in the Azipod shape resulted in another efficiency improvement of around seven per cent. Two years ago, when the next-generation
Azipod XO units were launched, a further two per cent improvement was delivered. Combining this with the other recent advances, therefore, Azipod hydrodynamic efficiency has been improved in total by more than 12 per cent over the first cruise ship application. “The
fuel efficiency improvements
An ABB Azipod featuring an X-tail and optimised fin shape for enhanced propulsive efficiency
Pods tailored for ice class propulsion
An ice-strengthened version of its azimuthing Mermaid podded electric propulsor is offered by Rolls-Royce for ice class propulsion applications. The modular Mermaid ICE pod programme embraces models with power ratings from 5,000kW to 15MW for ice classes up to PC4; higher powers or ice classes can be considered for special demands. The
pods will be built to customer
specifications and adapted to the specific hull and projected deployment duty to ensure optimum performance in open sea and ice
www.mpropulsion.com
conditions, yielding fuel savings in mixed operational profiles. Developed by Rolls-Royce in conjunction
ROLLS-ROYCE MERMAID ICE PODS Model
210 Rating, MW
Propeller diameter, m
Bollard pull thrust, kN
5-11 232 10.5-13
Shaft speed, rpm 105-150 100-143 3.7-5
4.5-5.6
600- 1,200
1,000- 1,500
250
12.5-15 95-135 4.9-6
1,200- 1,650
with electric motor, drive and automation partner Converteam, Mermaid ICE pods are based on the standard pod design but with strengthening for operation in ice. Rolls-Royce tapped long experience with ice-strengthened propellers
and thrusters in numerous
applications. Units are rotatable through 360 degrees for manoeuvring or +/- 35 degrees in transit by hydraulic steering gear. Reliability
is promised from a heavy duty
induction propulsion motor incorporating a robust rotor to withstand dynamic loads when
Marine Propulsion I February/March 2012 I 69
measured on Radiance of the Seas are a welcome reprieve from higher fuel prices,” says Anders Aasen, associate vice president/technical services for Royal Caribbean International and Azamara Cruises. “Any improvements we can make in fuel efficiency will serve us well for future operational costs.” By November last year over 100 ships had been equipped with Azipod propulsion and more than 240 units had been delivered or were on order. Some seven million operating hours had been logged in demanding applications, such as icebreakers, cruise ships, research vessels, offshore supply tonnage, drilling rigs, ferries and megayachts. • Cargo ship applications are targeted by ABB with a fixed, non-turning version of the Azipod mounted just behind a vessel’s conventional fixed pitch direct-drive propeller; a separate rudder is arranged for steering. This new contra-rotating system, Rudderpod CRP, is expected to yield an improvement in propulsive efficiency of some seven per cent, promising significant fuel savings and reduced emissions from a large container ship installation.
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 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76 |
Page 77 |
Page 78 |
Page 79 |
Page 80 |
Page 81 |
Page 82 |
Page 83 |
Page 84 |
Page 85 |
Page 86 |
Page 87 |
Page 88 |
Page 89 |
Page 90 |
Page 91 |
Page 92 |
Page 93 |
Page 94 |
Page 95 |
Page 96 |
Page 97 |
Page 98 |
Page 99 |
Page 100 |
Page 101 |
Page 102 |
Page 103 |
Page 104 |
Page 105 |
Page 106 |
Page 107 |
Page 108 |
Page 109 |
Page 110 |
Page 111 |
Page 112 |
Page 113 |
Page 114 |
Page 115 |
Page 116 |
Page 117 |
Page 118 |
Page 119 |
Page 120 |
Page 121 |
Page 122 |
Page 123 |
Page 124 |
Page 125 |
Page 126 |
Page 127 |
Page 128 |
Page 129 |
Page 130 |
Page 131 |
Page 132