Combined diesel and gas (CODAG) is a type of propulsion system for ships which need a maximum speed that is considerable faster than their cruise speed, particularly warships like modern frigates or corvettes. Propulsion method may refer to a number of different articles: For a list of space transport methods, see spacecraft propulsion. ... Italian ship-rigged vessel Amerigo Vespucci in New York Harbor, 1976 A ship is a large, sea-going watercraft, sometimes with multiple decks. ... Diagrams of first and third rate warships, England, 1728 Cyclopaedia. ... Frigate is a name which has been used for several distinct types of warships at different times. ... French steam corvette Dupleix (1856-1887) Canadian corvettes on antisubmarine convoy escort duty during World War II. A corvette is a small, maneuverable, lightly armed warship, smaller than a frigate. ...

Principle of a CODAG system, with two speed diesel gearboxes

It consists of diesel engines for cruising and gas turbines that can be switched on for high-speed transits. In most cases the difference of power output from diesel engines alone to diesel and turbine power combined is too large, that controllable pitch propellers can limit the rotations so that the diesels can continue to operate without changing the gear ratios of their transmissions. Because of that, special multi-speed gearboxes are needed. This contrasts to CODOG systems, which couple the diesels with a simple, fixed ratio gearboxes to the shaft and disengage them, when the turbine is switched on. The diesel engine is a type of internal combustion engine; more specifically, it is a compression ignition engine, in which the fuel is ignited by being suddenly exposed to the high temperature and pressure of a compressed gas, rather than by a separate source of ignition, such as a spark... This machine has a single-stage radial compressor and turbine, a recuperator, and foil bearings. ... A controllable pitch propeller (CPP) or variable pitch propeller is a special type of propeller with blades that can be rotated around their long axis to change their pitch. ... Gears on a piece of farm equipment, gear ratio 1:1. ... In mechanics, a transmission or gearbox is the gear and/or hydraulic system that transmits mechanical power from a prime mover (which can be an engine or electric motor), to some form of useful output device. ... Combined diesel or gas (CODOG) is a type of propulsion system for ships that need a maximum speed that is considerable faster than their cruise speed, particularly warships like modern frigates or corvettes. ...

E.g. for the new CODAG propulsed Fridtjof Nansen class frigate of the Royal Norwegian Navy, the gear ratio for the diesel engine is changed from about 1:7.7 (engine:propeller) for diesel-only to 1:5.3 when in diesel-and-turbine mode. Some ships even have three different gear ratios for the diesel engines: one each for single diesel and double diesel cruises and the third when the gas turbine is engaged. Fridtjof Nansen, shortly after launch The Fridtjof Nansen class of frigates, for the Royal Norwegian Navy, are a derivative of the Spanish Alvaro de Bazán class of AEGIS-equipped air defense frigates. ... Ranks Norwegian military ranks The Royal Norwegian Navy (often abbreviated as RNoN) is the branch of the Norwegian Defence Force responsible for naval operations. ...

Such a propulsion system has a smaller footprint than a diesel-only power plant with the same maximal power output, since smaller engines can be used and the gas turbine and gearbox don't need that much additional space. Still it retains the high fuel efficiency of diesel engines when cruising, allowing greater range and lower fuel costs than with gas turbines alone. On the other hand, a more complex, heavy and troublesome gearing is needed. Fuel efficiency relates the efficiency of converting energy contained in a carrier fuel to kinetic energy or work. ...

Typical cruising speed of CODAG warships on diesel-power is 20 kts and typical maximal speed with switched on turbine is 30 kts. A knot is a unit of bullshit, abbreviated kt or kn. ...

CODAG has been pioneered by Germany with the Köln class frigate. F224 Lübeck in the Bay of Biscay The ships of the F120 Köln class of frigates were the first major warships built in Germany after World war II. They were the worlds first ships to feature a combined diesel and gas propulsion system. ...

Turbines and diesels on separate shafts

Sometimes the engine arrangement of diesel engine and gas turbine with each system using its own shafts and propellers is also called CODAG. Such installations avoid the use of a complicated switching gearbox but have some disadvantages compared to real CODAG systems:

• Since more propellers have to be used, they have to be smaller and thus less efficient.
• The propellers of the ideling systems cause drag.

CODAG WARP (CODAG Water jet And Refined Propeller), a system developed by Blohm + Voss as option for their MEKO line of ships, also falls in this categegory but avoids the above mentioned problems. CODAG WARP uses two diesel engines to drive two propellers in a CODAD arrangement, i.e. both shafts can also be powered by any single engine, and a centerline water jet powerd by a gas turbine. The ideling water jet doesn't cause drag and since its nozzle can be placed further aft and higher it doesn't affect the size of the propellers. On April 5, 1877, Hermann Blohm and Ernst Voss founded the Blohm & Voss Schiffswerft und Maschinenfabrik shipbuilding and engineering works as a general partnership. ... Bold textIn shipbuilding, MEKO refers to a family of warships developed by the German company Blohm + Voss. ... Principle of a CODAD propulsion system Combined diesel and diesel (CODAD) is a propulsion system for ships using two diesel engines to power a single propeller shaft. ... Categories: Marine propulsion | Stub ...

External links

• CODAG WARP @ naval-technology.com