Combined diesel-electric and gas
Encyclopedia
Combined diesel and gas
Combined diesel and gas ' is a type of propulsion system for ships which need a maximum speed that is considerably faster than their cruise speed, particularly warships like modern frigates or corvettes....
propulsion system for ship
Ship
Since the end of the age of sail a ship has been any large buoyant marine vessel. Ships are generally distinguished from boats based on size and cargo or passenger capacity. Ships are used on lakes, seas, and rivers for a variety of activities, such as the transport of people or goods, fishing,...
s.
A CODLAG system employs electric motor
Electric motor
An electric motor converts electrical energy into mechanical energy.Most electric motors operate through the interaction of magnetic fields and current-carrying conductors to generate force...
s which are connected to the propeller shafts (usually 2). The motors are powered by diesel generator
Diesel generator
A diesel generator is the combination of a diesel engine with an electrical generator to generate electrical energy....
s. For higher speeds, a gas turbine
Gas turbine
A gas turbine, also called a combustion turbine, is a type of internal combustion engine. It has an upstream rotating compressor coupled to a downstream turbine, and a combustion chamber in-between....
powers the shafts via a cross-connecting gearbox
Transmission (mechanics)
A machine consists of a power source and a power transmission system, which provides controlled application of the power. Merriam-Webster defines transmission as: an assembly of parts including the speed-changing gears and the propeller shaft by which the power is transmitted from an engine to a...
; for cruise speed, the drive train of the turbine is disengaged with clutch
Clutch
A clutch is a mechanical device which provides for the transmission of power from one component to another...
es.
This arrangement combines the diesel engines used for propulsion and for electric power generation, greatly reducing service cost, since it reduces the number of different diesel engines and electric motors, requiring considerably less maintenance. Also electric motors work efficiently over a wide range of revolutions and can be connected directly to the propeller shaft so that simpler gearboxes can be used to combine the mechanical output of turbine and diesel-electric systems.
Another advantage of the diesel-electric transmission is that without the need of a mechanical connection, the diesel generators can be decoupled acoustically from the hull of the ship, making it less noisy. This has been used extensively by military submarine
Submarine
A submarine is a watercraft capable of independent operation below the surface of the water. It differs from a submersible, which has more limited underwater capability...
s but surface naval vessels like anti-submarine
Anti-submarine warfare
Anti-submarine warfare is a branch of naval warfare that uses surface warships, aircraft, or other submarines to find, track and deter, damage or destroy enemy submarines....
vessels will benefit as well. Usually CODLAG ships are equipped with rechargeable batteries like diesel-electric submarines as well, allowing them to maneuver in silence without any heavy machinery running.
Integrated electric propulsion (IEP)
A system which uses both diesel engines and gas turbines to generate electricity for electric motors, where there is no mechanical transmission from either to the propellers, is not classified as CODLAG, but as integrated electric propulsion (IEP) or integrated full electric propulsion (IFEP). Such an arrangement is in use on passenger ships like RMS Queen Mary 2RMS Queen Mary 2
RMS Queen Mary 2 is a transatlantic ocean liner. She was the first major ocean liner built since in 1969, the vessel she succeeded as flagship of the Cunard Line....
, with a pool of diesel generators for the base load and turbo generators for peak power, and on warships such as the Royal Navy
Royal Navy
The Royal Navy is the naval warfare service branch of the British Armed Forces. Founded in the 16th century, it is the oldest service branch and is known as the Senior Service...
's Type 45 destroyer
Type 45 destroyer
The United Kingdom's Type 45 destroyer is an air defence destroyer programme of the Royal Navy which will replace its Type 42 destroyers. The first ship in the class, HMS Daring, was launched on 1 February 2006 and commissioned on 23 July 2009. The ships are now built by BAE Systems Surface Ships...
and the upcoming (DDG-1000/DD(X)).
List of CODLAG ships
- Type 23 frigateType 23 frigateThe Type 23 frigate is a class of frigate built for the Royal Navy of the United Kingdom. All the ships were first named after British Dukes, thus the class is also known as the Duke class. The first Type 23 was commissioned in 1989, and the sixteenth, was launched in May 2000 and commissioned in...
(Royal NavyRoyal NavyThe Royal Navy is the naval warfare service branch of the British Armed Forces. Founded in the 16th century, it is the oldest service branch and is known as the Senior Service...
) - F125 class frigateF125 class frigateF125 is the project name for the Type 125 Baden-Württemberg class of frigates, currently in development for the German Navy by ARGE F125, a joint-venture of Thyssen-Krupp and Lürssen...
(German NavyGerman NavyThe German Navy is the navy of Germany and is part of the unified Bundeswehr .The German Navy traces its roots back to the Imperial Fleet of the revolutionary era of 1848 – 52 and more directly to the Prussian Navy, which later evolved into the Northern German Federal Navy...
) - GTS FinnjetGTS FinnjetGTS Finnjet was a cruiseferry, built in 1977 by Wärtsilä Helsinki, Finland for Finnlines traffic between Finland and Germany. At the time of her delivery, Finnjet was the fastest, longest and largest car ferry in the world, and the only one powered by gas turbines...
(Finnish cruiseferryCruiseferryA cruiseferry is a ship that combines the features of a cruise ship with a Ro-Pax ferry. Many passengers travel with the ships for the cruise experience, staying only a few hours at the destination port or not leaving the ship at all, while others use the ships as means of...
)