Combined gas and steam (COGAS) is the name given to
marine
Marine is an adjective meaning of or pertaining to the sea or ocean.
Marine or marines may refer to:
Ocean
* Maritime (disambiguation)
* Marine art
* Marine biology
* Marine debris
* Marine habitats
* Marine life
* Marine pollution
Military
* ...
compound powerplants comprising
gas and
steam turbine
A steam turbine is a machine that extracts thermal energy from pressurized steam and uses it to do mechanical work on a rotating output shaft. Its modern manifestation was invented by Charles Parsons in 1884. Fabrication of a modern steam turbin ...
s, the latter being driven by steam generated using the heat from the exhaust of the gas turbines. In this way, some of the otherwise lost energy can be reclaimed and the
specific fuel consumption of the plant can be decreased. Large (land-based) electric powerplants built using this combined cycle can reach conversion efficiencies of over 60%.
If the turbines do not drive a
propeller shafts directly and instead a
turbo-electric
A turbo-electric transmission uses electric generators to convert the mechanical energy of a turbine (steam or gas) into electric energy, which then powers electric motors and converts back into mechanical energy that power the driveshafts.
Tur ...
transmission is used, the system is also known as COGES.
COGAS differs from many other combined marine propulsion systems in that it is not intended to operate on one system alone. While this is possible, it will not operate efficiently this way, as with
Combined diesel and gas
Combined diesel and gas (CODAG) is a type of propulsion system for ships that need a maximum speed that is considerably faster than their cruise speed, particularly warships like modern frigates or corvettes.
Pioneered by Germany with the , ...
systems when run solely on diesel engines. Especially COGAS should not be confused with
Combined steam and gas (COSAG) power plants, which employ traditional, oil-fired boilers for steam turbine propulsion for normal cruising, and supplement this with gas turbines for faster reaction times and higher dash speed.
COGAS has been proposed as upgrade for ships that use gas turbines as their main (or only) engines, e.g. in
COGOG or
COGAG mode, such as the s, but currently no
naval ship uses this concept. However some modern
cruise ships are equipped with COGES. E.g.
Celebrity Cruises
Celebrity Cruises is a cruise line headquartered in Miami, Florida and a wholly owned subsidiary of Royal Caribbean Group. Celebrity Cruises was founded in 1988 by the Greece-based Chandris Group, and merged with Royal Caribbean Cruise Line in 19 ...
' ''
Millennium'' and other ships of her class use turbo-electric plants with two
General Electric LM2500+ gas turbines and one steam-turbine.
BMW is currently researching combined gas and steam for automotive use, using their
turbosteamer system. This uses the
waste heat of combustion from the exhaust and turns it into steam to produce torque which is input into the
crankshaft
A crankshaft is a mechanical component used in a piston engine to convert the reciprocating motion into rotational motion. The crankshaft is a rotating shaft containing one or more crankpins, that are driven by the pistons via the connecting ...
.
See also
*
Cogeneration
*
Combined cycle
A combined cycle power plant is an assembly of heat engines that work in tandem from the same source of heat, converting it into mechanical energy. On land, when used to make electricity the most common type is called a combined cycle gas turb ...
References
External links
Gizmag article discussing BMW's turbosteamerArticle on BMW's alternative Combined Cycle Hybrid technology
{{DEFAULTSORT:Combined Gas And Steam
Marine propulsion
Steam power
de:Gas-und-Dampf-Kombikraftwerk