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Combined gas turbine and gas turbine (COGAG) is a type of propulsion system for ships using two gas turbines connected to a single propeller shaft. A gearbox and clutches 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.[1]

Principle of a COGAG propulsion system

Description

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Combined
marine
propulsion

CODOG
CODAG
CODLAD
CODLAG
CODAD
COSAG
COGOG
COGAG
COGAS
CONAS
IEP or IFEP

A COGAG system consists of two gas turbines, 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.[2]

Advantages and disadvantages

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Advantages of the system include a large degree of automation along with quick startup time, they are easier to silence and protect from shock.[3] 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.[4] Issues with COGAG systems include their complexity and gearbox issues and high fuel use.[5]

List of COGAG ships

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Citations

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  1. ^ Soares 2015, pp. 10, 27.
  2. ^ Plaff 2021, p. 95.
  3. ^ Graves & Carleton 1963, p. 12.
  4. ^ Soares 2015, p. 31.
  5. ^ Plaff 2021, p. 92.

References

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  • Graves, G. L.; Carleton, R. S. (September 1963). "Gas Turbines for Unconventional Craft". Bureau of Ships Journal. 12 (9): 7–12.
  • Plaff, Manfred (2021). Ship Operation Technology: Reference Book and Guidebook. Wiesbaden, Germany: Springer Fachmedien. ISBN 978-3-658-32729-3.
  • Soares, Claire (2015) [2008]. Gas Turbines: A Handbook of Air, Land and Sea Applications (Second ed.). Kidlington, Oxford: Elsevier. ISBN 978-0-12-410461-7.