Combined gas and gas
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.
| Combined marine propulsion |
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CODOG |
Using one or two gas turbines has the advantage of having two different power settings. Since the fuel efficiency of a gas turbine is best near its maximum power level, a small gas turbine running at its full power is more efficient compared to a twice as powerful turbine running at half power, allowing more-economical transit at cruise speeds.
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.
List of COGAG ships
- Kolkata-class guided-missile destroyer (Indian Navy)
- Type 22 frigate (Batch 3) (Royal Navy)
- Invincible-class aircraft carrier (Royal Navy)
- Cavour-class aircraft carrier (Italian Navy)
- Asagiri-class destroyer (Japan Maritime Self-Defense Force), and subsequent destroyer classes
- Hyūga-class helicopter destroyer (Japan Maritime Self-Defense Force), helicopter carrier
- Izumo-class helicopter destroyer (Japan Maritime Self-Defense Force), helicopter carrier
- Neustrashimyy-class frigate (Russian Navy)
- Sejong the Great-class destroyer (Republic of Korea Navy)
- Skjold-class corvette (Royal Norwegian Navy)
- Arleigh Burke-class destroyer (United States Navy)
- Ticonderoga-class cruiser (United States Navy)
- Wasp-class amphibious assault ship (United States Navy)