Combined gas and steam ( COGAS ) is a type of marine compound powerplant comprising gas and steam turbines , the latter being driven by steam generated using the heat from the exhaust of the gas turbines.
20-459: Combined diesel or gas (CODOG) Combined diesel and gas (CODAG) Combined diesel-electric and diesel (CODLAD) Combined diesel–electric and gas (CODLAG) Combined diesel and diesel (CODAD) Combined steam and gas (COSAG) Combined gas or gas (COGOG) Combined gas and gas (COGAG) Combined gas and steam (COGAS) Combined nuclear and steam propulsion (CONAS) Integrated electric propulsion (IEP or IFEP) In this way, some of
40-401: A fixed-gear or two-speed transmission with no reverse gear ratio. The simplest transmissions used a fixed ratio to provide either a gear reduction or increase in speed, sometimes in conjunction with a change in the orientation of the output shaft. Examples of such transmissions are used in helicopters and wind turbines . In the case of a wind turbine, the first stage of the gearbox is usually
60-437: A planetary gear, to minimize the size while withstanding the high torque inputs from the turbine. Many transmissions – especially for transportation applications – have multiple gears that are used to change the ratio of input speed (e.g. engine rpm) to the output speed (e.g. the speed of a car) as required for a given situation. Gear (ratio) selection can be manual, semi-automatic, or automatic. A manual transmission requires
80-449: A range of approximately 600–7000 rpm, while the vehicle's speeds requires the wheels to rotate in the range of 0–1800 rpm. In the early mass-produced automobiles, the standard transmission design was manual : the combination of gears was selected by the driver through a lever (the gear stick ) that displaced gears and gear groups along their axes. Starting in 1939, cars using various types of automatic transmission became available in
100-537: A single fixed-gear ratio, multiple distinct gear ratios , or continuously variable ratios. Variable-ratio transmissions are used in all sorts of machinery, especially vehicles. Early transmissions included the right-angle drives and other gearing in windmills , horse -powered devices, and steam -powered devices. Applications of these devices included pumps , mills and hoists . Bicycles traditionally have used hub gear or Derailleur gear transmissions, but there are other more recent design innovations. Since
120-475: Is connected to the engine via a torque converter (or a fluid coupling prior to the 1960s), instead of the friction clutch used by most manual transmissions and dual-clutch transmissions. A dual-clutch transmission (DCT) uses two separate clutches for odd and even gear sets . The design is often similar to two separate manual transmissions with their respective clutches contained within one housing, and working as one unit. In car and truck applications,
140-548: Is essentially a conventional manual transmission that uses automatic actuation to operate the clutch and/or shift between gears. Many early versions of these transmissions were semi-automatic in operation, such as Autostick , which automatically control only the clutch , but still require the driver's input to initiate gear changes. Some of these systems are also referred to as clutchless manual systems. Modern versions of these systems that are fully automatic in operation, such as Selespeed and Easytronic , can control both
160-653: 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 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
180-422: Is one diesel engine for cruising speed and one geared gas turbine for high speed dashes. Both are connected to the shaft with clutches ; only one system is driving the ship, in contrast to combined diesel and gas (CODAG) systems that can use the combined power output of both. The advantage of CODOG is a simpler gearing compared to CODAG, but it needs either more powerful or additional gas turbines to achieve
200-494: The Arleigh Burke -class destroyers , but currently no naval ship uses this concept. However some modern cruise ships are equipped with COGES. E.g. Celebrity Cruises ' 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
220-431: The torque and power output of an internal combustion engine varies with its rpm , automobiles powered by ICEs require multiple gear ratios to keep the engine within its power band to produce optimal power, fuel efficiency , and smooth operation. Multiple gear ratios are also needed to provide sufficient acceleration and velocity for safe & reliable operation at modern highway speeds. ICEs typically operate over
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#1732851777320240-862: The waste heat of combustion from the exhaust and turns it into steam to produce torque which is input into the crankshaft . Combined diesel or gas Combined diesel or gas ( CODOG ) 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 . Combined diesel or gas (CODOG) Combined diesel and gas (CODAG) Combined diesel-electric and diesel (CODLAD) Combined diesel–electric and gas (CODLAG) Combined diesel and diesel (CODAD) Combined steam and gas (COSAG) Combined gas or gas (COGOG) Combined gas and gas (COGAG) Combined gas and steam (COGAS) Combined nuclear and steam propulsion (CONAS) Integrated electric propulsion (IEP or IFEP) For every propeller shaft there
260-454: The DCT functions as an automatic transmission, requiring no driver input to change gears. A continuously variable transmission (CVT) can change seamlessly through a continuous range of gear ratios . This contrasts with other transmissions that provide a limited number of gear ratios in fixed steps. The flexibility of a CVT with suitable control may allow the engine to operate at a constant RPM while
280-544: The US market. These vehicles used the engine's own power to change the effective gear ratio depending on the load so as to keep the engine running close to its optimal rotation speed. Automatic transmissions now are used in more than 2/3 of cars globally, and on almost all new cars in the US. Most currently-produced passenger cars with gasoline or diesel engines use transmissions with 4–10 forward gear ratios (also called speeds) and one reverse gear ratio. Electric vehicles typically use
300-401: The clutch operation and the gear shifts automatically, without any input from the driver. An automatic transmission does not require any input from the driver to change forward gears under normal driving conditions. The most common design of automatic transmissions is the hydraulic automatic, which typically uses planetary gearsets that are operated using hydraulics . The transmission
320-545: The driver to manually select the gears by operating a gear stick and clutch (which is usually a foot pedal for cars or a hand lever for motorcycles). Most transmissions in modern cars use synchromesh to synchronise the speeds of the input and output shafts. However, prior to the 1950s, most cars used non-synchronous transmissions . A sequential manual transmission is a type of non-synchronous transmission used mostly for motorcycles and racing cars. It produces faster shift times than synchronized manual transmissions, through
340-493: 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 shaft directly and instead a turbo-electric transmission is used, the system is known as COGES (combined gas turbine-electric and steam). COGAS differs from many other combined marine propulsion systems in that it
360-414: The same maximum power output. The disadvantage of CODOG is that the fuel consumption at high speed is poor compared to CODAG. Transmission (mechanics) A transmission (also called a gearbox ) is a mechanical device which uses a gear set —two or more gears working together—to change the speed, direction of rotation, or torque multiplication/reduction in a machine . Transmissions can have
380-419: The use of dog clutches rather than synchromesh. Sequential manual transmissions also restrict the driver to selecting either the next or previous gear, in a successive order. A semi-automatic transmission is where some of the operation is automated (often the actuation of the clutch), but the driver's input is required to move off from a standstill or to change gears. An automated manual transmission (AMT)
400-452: The vehicle moves at varying speeds. CVTs are used in cars, tractors, side-by-sides , motor scooters, snowmobiles , bicycles, and earthmoving equipment . The most common type of CVT uses two pulleys connected by a belt or chain ; however, several other designs have also been used at times. Gearboxes are often a major source of noise and vibration in vehicles and stationary machinery. Higher sound levels are generally emitted when
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