FACTOID #151: The five countries with the highest coffee consumption are also the five countries whose citizens trust one another the most. Coincidence? Probably.
CODOG CODAG CODLAG CODAD COSAG COGOG COGAG COGAS 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. ... Combined diesel and gas, usually abbreviated CODAG is a type of propulsion system for ships, particularly warships. ... COmbined Diesel-eLectric And Gas (CODLAG) is a modification of the combined diesel and gas propulsion system for ships. ... 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. ... 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 turbo-electric COGAS power-plant Combined gas and steam (COGAS) is the name given to marine compound powerplants of gas and steam turbines, the latter are fed with steam generated with the heat from the hot exhaust of the gas turbines. ...
Principle of a COGOG propulsion system
Combined gas or gas (COGOG) is a propulsion system for ships using gas turbine engines. A high efficiency, low output turbine is used for cruising speeds with a high output turbine being used for high-speed operations. A clutch allows either turbine to be selected, but there is no gearbox to allow operation of both turbines at once. This has the advantage of not requiring heavy, expensive and potentially unreliable gearboxes. 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. ... This machine has a single-stage radial compressor and turbine, a recuperator, and foil bearings. ... A clutch is a subcomponent of an engines transmission designed to allow engagement or disengagement of the engine to the gearbox or whatever apparatus is being driven. ... 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. ...
Combinedgas turbine and gas turbine (COGAG) is a type of propulsion system for ships using two gas turbines connected to a single propeller shaft.
Since the fuel efficiency of a gas turbine is best near its maximum power level, a small gas turbine running at its full speed is more efficient compared to a twice as powerful turbine running at half speed, allowing more economic 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 its also somewhat lower for high speed dashes.
The gas turbine has the inherent disadvantage that reduced air density with high ambient temperature or high elevation causes a significant reduction in power output and efficiency, because the mass flow through the gas turbine is reduced.
The gas turbine, steam turbine, and generator may be arranged as a single-shaft design, or a multishaft arrangement may be used with each gas turbine driving a generator and exhausting into its heat recovery boiler with all boilers supplying a separate steam turbine and generator.
Another point favoring staging a combined-cycle unit is that the gas turbine (or combined-cycle) per kilowatt cost does not seem to increase significantly for smaller units, as is the case for steam units due partly to the high cost of the substantial civil works necessary for steam plants regardless of steam unit size.
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