Page 68: of Maritime Reporter Magazine (September 1997)

MARINE PROPULSION TECHNOLOGY — JETS, THRUSTERS AND AZIPODS

More Than Just A Propeller •••

Modern methods of propulsion offer ship operators a wide variety of efficient systems to move a ves- sel through the water. High levels of maneuverability and enhanced propeller geometry allow higher speeds to be achieved at the same fuel consumption, while side thrusters eliminate tug require- ments when berthing — helping to reduce port costs and enhancing turnaround times.

The first of two new double- ended train and car ferries for DSB

Rederi, the Danish state railways ferry operator, entered service between Rodby, Denmark and

Puttgarden, Germany, in June.

Built at Christian 0rskov

Shipyard in Frederikshavn,

Denmark, the two ships are oper- ated on behalf of the owner by

Scandlines. The second vessel is due to enter service this month.

The ships are powered by four

Kamewa/Aquamaster main propulsion units, powered by ABB

Sami Megastar pulse width modu- lated (PWM) propulsion drives.

The Contaz propulsors use new- generation azimuthing, contra- rotating thruster propeller tech- nology that has been developed to provide low noise and vibration levels.

Each of the double-bow vessels has two 3,000-kW propulsors at each end, giving the ferries a nor- mal service speed of 16.5 knots with a maximum of 18.5 knots, and allowing the vessels to operate in all weather conditions.

Using this system, it has been possible to provide a bulbous bow and streamlined body which, reportedly, provides higher effi- ciency and speed compared to tra- ditional propulsion systems. Two similar vessels using Contaz propulsors are currently building at van der Giessen de Noord in the

Netherlands for German owner

DFO.

Kamewa, Aquamaster's parent company, has supplied S112 water- jets to the SuperSeaCat class of high-speed monohulls, the first of which has been delivered by

Fincantieri to its operator,

Bermuda-based Sea Containers.

Entering service on the route from

Dover, England, to Calais, France, four Ruston 20RK270 engines, each rated at 6,875 kW are used to drive the four waterjets, giving the craft a fully laden service speed of 37.8 knots.

Ulstein Propeller of Norway is currently supplying thirteen model 250TV tunnel thrusters for a series of 2,500-TEU containerships build- ing at Flender Werft and MTW in

Germany for domestic owners.

Each of the thrusters is fitted with a 1.9-m diameter CP pro- peller with an output of 1,100 kW.

The units are powered by an AC electric motor and Ulstein is also supplying the remote controls for the thrusters.

The contract for the thrusters includes an option for seven addi- tional units.

In the Netherlands, Lips BV con- tinues to supply a wide range of propulsion systems, including thrusters and waterjets — the lat- ter for high-speed craft. Wateijets are used when a vessel's speed requirement exceeds that which can be generated by a propeller driven system.

In general, waterjets have a very high propulsive efficiency over a wide speed range, and without underwater protuberances, can operate in shallow waters. It allows reduced hull drag with good acceleration and crash-stop perfor- mance.

The system also allows for con- siderable weight reduction onboard — a pre-requisite for high-speed craft — as gearing in direct drive installations and shaft lines are not required.

A number of Lips waterjets have been supplied to Incat, an

Australia-based fast ferry builder, for craft including Stena Line's

Lynx fleet. Powered by Ruston 16RK270 series diesel engines, the LJ135D waterjets allow speeds in excess of 40 knots to be achieved.

Among thruster installations, three Lips steerable thrusters with 3.2-m diameter FP propellers — each driven by a 3,500-kW elec- tric motor — were fitted to an

FPSO delivered earlier this year to Rasmussen Management AS of

Norway by Mitsui Engineering of

Japan.

The thrusters will be used for propulsion and for positioning the vessel when on station.

Schottel Werft of Germany has developed the twin propeller (STP) which seeks to significantly reduce efficiency loss due to vortices around the propeller. In trials, the system reportedly provided an effi- ciency increase of approximately 12 percent, with the use of tip-vor- tex-vane (TW) propellers and hub-vortex-vane (HW) propellers, over the more conventional rudder propellers.

The STP is a 360-degree steer- able propulsion unit which has two similarly-sized propellers, both mounted on a single shaft and rotate in the same direction. Both propellers are driven via a bevel gear system through the underwa- ter gearbox arrangement.

The forward unit operates as a pulling propeller and attains a very high efficiency level.

The water flow from this is deflected by two guide fins and the housing stem so that as it passes the second and pushing propeller, it is free from the swirling motion created by the first unit. This "clean" water also allows the sec- ond propeller to work at a high effi- ciency level at low loadings.

Since the introduction of the

Azipod in 1990 by Kvaerner Masa-

Yards (KMY) and ABB Marine of

Finland, podded drives have cap- tured the interest of two other con- sortia.

In Germany, Siemens and

Schottel Werft have developed their version of the concept, the

Siemens-Schottel Propulsor (SSP).

In France, Cegelec has teamed with Kamewa of Sweden and Delta

Marine of Finland to develop the

Kamewa-Cegelec Pod (KCP).

Podded drives are complete propulsion and steering units sus- pended below the ship, in place of conventional rudders or propellers.

The pod contains an electric motor, the drive end of which is attached to an FP propeller.

Power and data transmission to the motor is delivered from the vessel's alternators via electric cables and a slip ring unit. The slip ring unit allows 360-degree rotation of the pod for steering pur- poses.

KMY's Azipod systems are presently fitted to a waterways vessel, a river icebreaker and two icebreaking tankers.

Two 14-MW units have been fit- ted to Carnival Cruise Line's 70,400-gt Elation, with two similar units to be installed on Paradise.

The podded drive system gives naval architects greater freedom in designing hull form, as well as eliminates weight and space as no steering gear, reduction gearing or shaftlines are required. It is suit- able for most types of vessels and offshore installations, particularly in the dynamic positioning mode.

Pictured are

Kvaerner Masa-

Yards Azipod propulsion units, as fitted on Carnival o

Cruise Line's

Elation. 68 Maritime Reporter/Engineering News