Combined gas turbine and gas turbine (COGAG) is a type of propulsion system for ships using two

gas turbine A gas turbine or gas turbine engine is a type of Internal combustion engine#Continuous combustion, continuous flow internal combustion engine. The main parts common to all gas turbine engines form the power-producing part (known as the gas gene ...

s connected to a single

propeller shaft A drive shaft, driveshaft, driving shaft, tailshaft (Australian English), propeller shaft (prop shaft), or Cardan shaft (after Girolamo Cardano) is a component for transmitting mechanical power, torque, and rotation, usually used to connect o ...

. A

gearbox A transmission (also called a gearbox) is a mechanical device invented by Louis Renault (who founded Renault) which uses a gear set—two or more gears working together—to change the speed, direction of rotation, or torque multiplication/r ...

and

clutch A clutch is a mechanical device that allows an output shaft to be disconnected from a rotating input shaft. The clutch's input shaft is typically attached to a motor, while the clutch's output shaft is connected to the mechanism that does th ...

es allow either of the turbines to drive the shaft or both of them combined. Marine usage of COGAG systems are similar to those found ashore.

Description

A COGAG system consists of two

s, each connected to a reduction gearbox. These are each attached to a coupling with both connected to larger gearbox and then to the ship's propeller.

Advantages and disadvantages

Advantages of the system include a large degree of automation along with quick startup time, they are easier to silence and protect from shock. Compared to combined diesel and gas (CODAG) or combined diesel or gas (CODOG), COGAG systems have a smaller footprint but a much lower fuel efficiency at cruise speed and for CODAG systems it is also somewhat lower for high speed dashes. Issues with COGAG systems include their complexity and gearbox issues and high fuel use.

List of COGAG ships

guided-missile destroyer A guided-missile destroyer (DDG) is a destroyer whose primary armament is guided missiles so they can provide anti-aircraft warfare screening for the fleet. The NATO standard designation for these vessels is DDG, while destroyers which have a pr ...

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Indian Navy The Indian Navy (IN) (ISO 15919, ISO: ) is the Navy, maritime and Amphibious warfare, amphibious branch of the Indian Armed Forces. The President of India is the Supreme Commander of the Indian Navy. The Chief of the Naval Staff (India), Chief ...

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Type 22 frigate The Type 22 frigate also known as the ''Broadsword'' class was a ship class, class of frigates built for the British Royal Navy. Fourteen were built in total, with production divided into three batches. Initially intended to be anti-submarine ...

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Royal Navy The Royal Navy (RN) is the naval warfare force of the United Kingdom. It is a component of His Majesty's Naval Service, and its officers hold their commissions from the King of the United Kingdom, King. Although warships were used by Kingdom ...

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Italian Navy The Italian Navy (; abbreviated as MM) is one of the four branches of Italian Armed Forces and was formed in 1946 from what remained of the ''Regia Marina'' (Royal Navy) after World War II. , the Italian Navy had a strength of 30,923 active per ...

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Japan Maritime Self-Defense Force The , abbreviated , also simply known as the Japanese Navy, is the maritime warfare branch of the Japan Self-Defense Forces, tasked with the naval defense of Japan. The JMSDF was formed following the dissolution of the Imperial Japanese Navy ( ...

), and subsequent destroyer classes * (Japan Maritime Self-Defense Force), helicopter carrier * (Japan Maritime Self-Defense Force), helicopter carrier *

Type 055 destroyer The Type 055 destroyer (NATO/ OSD designation Renhai-class cruiser) is a class of stealth guided-missile destroyers (rated as guided-missile cruisers per NATO/OSD standard parlance) constructed for the Chinese People's Liberation Army Navy (P ...

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People's Liberation Army Navy The People's Liberation Army Navy, also known as the People's Navy, PLA Navy or simply Chinese Navy, is the naval warfare military branch, branch of the People's Liberation Army, the national military of the People's Republic of China. It i ...

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Russian Navy The Russian Navy is the Navy, naval arm of the Russian Armed Forces. It has existed in various forms since 1696. Its present iteration was formed in January 1992 when it succeeded the Navy of the Commonwealth of Independent States (which had i ...

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Republic of Korea Navy The Republic of Korea Navy (ROKN; ), also known as the ROK Navy is the naval warfare service branch of the Republic of Korea Armed Forces, South Korean armed forces, responsible for naval and Amphibious warfare, amphibious operations. The South ...

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Royal Norwegian Navy The Royal Norwegian Navy () is the branch of the Norwegian Armed Forces responsible for navy, naval operations of Norway, including those of the Norwegian Coast Guard. , the Royal Norwegian Navy consists of approximately 3,700 personnel (9,450 i ...

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United States Navy The United States Navy (USN) is the naval warfare, maritime military branch, service branch of the United States Department of Defense. It is the world's most powerful navy with the largest Displacement (ship), displacement, at 4.5 millio ...

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Citations

References

* * * {{cite book , last=Soares , first=Claire , date=2015 , orig-year=2008 , title=Gas Turbines: A Handbook of Air, Land and Sea Applications , edition=Second , publisher=Elsevier , location=Kidlington, Oxford , isbn=978-0-12-410461-7 Marine propulsion