Combined gas and steam
Encyclopedia
Ship transport
Ship transport is watercraft carrying people or goods . Sea transport has been the largest carrier of freight throughout recorded history. Although the importance of sea travel for passengers has decreased due to aviation, it is effective for short trips and pleasure cruises...
compound powerplants comprising gas
Gas turbine
A gas turbine, also called a combustion turbine, is a type of internal combustion engine. It has an upstream rotating compressor coupled to a downstream turbine, and a combustion chamber in-between....
and steam turbine
Steam turbine
A steam turbine is a mechanical device that extracts thermal energy from pressurized steam, and converts it into rotary motion. Its modern manifestation was invented by Sir Charles Parsons in 1884....
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 58%.
If the turbines do not drive a propeller shafts directly and instead a turbo-electric
Turbo-electric
A turbo-electric transmission uses electric generators to convert the mechanical energy of a turbine into electric energy and electric motors to convert it back into mechanical energy to power the driveshafts....
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
Combined diesel and gas ' is a type of propulsion system for ships which need a maximum speed that is considerably faster than their cruise speed, particularly warships like modern frigates or corvettes....
systems when run solely on diesel engines. Especially COGAS should not be confused with Combined steam and gas
Combined steam and gas
Combined steam and gas is a propulsion system for ships using a combination of steam turbines and gas turbines to power the shafts. A gearbox and clutches enable either of the engines or both of them together to drive the shaft. It has the advantage of the cruising efficiency and reliability of...
(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
Combined gas or gas
Combined gas or gas 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...
or COGAG
Combined gas and gas
Combined gas turbine and gas turbine 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....
mode, like the Arleigh Burke class destroyer
Arleigh Burke class destroyer
The Arleigh Burke class of guided missile destroyers is the United States Navy's first class of destroyer built around the Aegis combat system and the SPY-1D multi-function phased array radar. The class is named for Admiral Arleigh "31-Knot" Burke, the most famous American destroyer officer of...
s, but currently no naval ship
Naval ship
A naval ship is a ship used for combat purposes, commonly by a navy. Naval ships are differentiated from civilian ships by construction and purpose...
uses this concept. However some modern cruise ship
Cruise ship
A cruise ship or cruise liner is a passenger ship used for pleasure voyages, where the voyage itself and the ship's amenities are part of the experience, as well as the different destinations along the way...
s are equipped with COGES. E.g. Celebrity Cruises
Celebrity Cruises
Celebrity Cruises is a cruise line founded in 1988 by the Greek Chandris Group. In 1997, Celebrity Cruises Ltd. merged with Royal Caribbean International to become Royal Caribbean Cruises Ltd., which operates Celebrity, Royal Caribbean International, Azamara Club Cruises, Pullmantur Cruises and CDF...
' Millennium
Millennium (ship)
GTS Millennium is the flagship of the Millennium Class of cruise ships, operated by the Celebrity Cruises line. Her sister ships are Constellation, Infinity, and Summit.She was built at Chantiers de l'Atlantique in St. Nazaire, France...
and other ships of her class use turbo-electric plants with two General Electric LM2500
General Electric LM2500
-External links:* .* *...
+ gas turbines and one steam-turbine.
BMW
BMW
Bayerische Motoren Werke AG is a German automobile, motorcycle and engine manufacturing company founded in 1916. It also owns and produces the Mini marque, and is the parent company of Rolls-Royce Motor Cars. BMW produces motorcycles under BMW Motorrad and Husqvarna brands...
is currently researching combined gas and steam for automotive use, using their turbosteamer
Turbosteamer
A turbosteamer is a term used by BMW to describe a combined cycle engine. It uses a steam engine to convert waste heat energy from an internal combustion engine into supplemental power for the vehicle. The turbosteamer device is affixed to the exhaust and cooling system...
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
Crankshaft
The crankshaft, sometimes casually abbreviated to crank, is the part of an engine which translates reciprocating linear piston motion into rotation...
.