gearboxes
Hybrid gear solutions benefit variable operating patterns
With complex propulsion arrangements becoming commonplace and overall ship power requirements more integrated, gear manufacturers are offering hybrid solutions to meet all onboard power needs
by Dick Amos battery package control system
n 2011, Kumera AS of Sandefjord, Norway, introduced its Norgear Hybrid gear propulsion concept. This system is particularly suited to tug and workboat applications where operating patterns are highly variable and the adoption of hybrid drives can result in significant fuel savings for the operator. This is particularly so with vessels such as harbour tugs, which have operating profiles varying from low to high power and also spend a proportion of time at idle or in transit. Flexibility of power use, through the Norgear hybrid gearbox, assists operators in meeting environmental targets and, at the same time, reduces fuel costs and emissions. All power sources on board the vessel can also be accessed and modes of driver operation can be adapted to best meet demands. Propulsion options are: • main diesel engine drive only • electric drive from combined motor generator powered from generating sets • diesel engine and electric drive for maximum power demands • further electrical power enhancement from battery capacity. Auxiliary options available allow ship electrical supplies and auxiliary drives to be powered through the gearbox, from either generating sets or the main engines. These gear drives are available for duties
I such as
hydraulic and cargo drive pumps or for fire- fighting pumps. For controlled operation, soft engagement is provided for auxiliary drives through integral multi-disc hydraulic clutches. The major benefits of geared hybrid propulsion systems are in the flexibility of operation and the ability to balance driver operation with load requirements, minimising fuel consumption and emissions. With the opportunity to also access power from generator sets for propulsion, the size of main engines can be reduced as electrical power boost can be gained when maximum pull
www.mpropulsion.com
combined alternators/motors
propulsion drives: - CPP drive - z-drive - voith drive - azimuth drive
generating set
Fi-Fi, hydraulics or cargo pump
main engine (diesel) drive generating set
main engine (diesel) drive
Fi-Fi, hydraulics or cargo pump
Kumera Norgear Hybrid gear systems offer a range of auxiliary power options
is required. Hybrid systems also satisfy emission control area requirements, allowing wider scope for operation in more sensitive environmental areas. Safety is also enhanced as propulsion power can be provided through use of installed generator capacity, in the event of a main drive engine failure.
Similar hybrid systems are offered by the Wärtsilä Corp of Finland, with the company having provided propulsion packages
for applications
including the Vik-Sandvik design type VS491 CD. Drive system packages were delivered to these high powered anchor handling tug supply vessels (AHTS) between 2007 and 2011. The AHTS concept requires efficient and flexible propulsion to cope with highly variable operational cycles. Central to the power system are two Wärtsilä SCH105-SDC63 reduction gear units each transmitting power from a main 8,000kW Wärtsilä 16V32 engine and a motor-generator rated at 3,000kW. These SCH105 gearboxes are rated at a maximum over 12MW but the SCH range provides for powers of up to 24MW. Wärtsilä has a large portfolio of gear products and can supply single and twin input reduction gearboxes for single or dual diesel engine propulsion drives. These come with a range of power take-off and clutch options for
flexibility of use. Twin input gearboxes
offer higher propulsive power transmission but with the option to use only one engine when power demands are lower, thus providing overall efficiency benefits.
Amongst the most demanding requirements
for gear systems are the higher powers and higher speeds of gas turbine drivers. Although these have been seen in commercial vessels, newbuild naval applications are a popular application, due to high power-to-weight and power-to-size ratios. The US Navy Littoral Combat Ships (LCS) will feature gears supplied by Renk AG, an Augsburg- based subsidiary of MAN SE. Propulsive power for the 115m-long Freedom Class monohull vessels is provided by two Rolls-Royce MT30 36MW gas turbines and two Colt-Pielstick diesel engines. These drive four Rolls-Royce waterjets giving a top speed of approximately 47 knots. The Independence Class trimarans are powered by two General Electric LM2500 gas turbines and two MTU Friedrichshafen 20V 8000 series diesel engines, also driving four Wärtsilä waterjets. In addition, the trimarans are equipped with a retractable bow-mounted azimuth thruster. Despite its significantly broader beam, the Independence Class vessels can still achieved speeds of 44 knots. The first build LCS-2 trimaran was equipped
Marine Propulsion I February/March 2012 I 57
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