CVA 002 aircraft carrier - Propulsion
As is well known, China is deficient in marine propulsion technology, and has not produced significant steam turbine or gas turbine marine propulsion plants. Only a few PLAN warships are equipped with such propulsion plants, which are standard in navies around the world, and the few Chinese installations involve plants of foreign manufacture. China's commercial and military surface vessels are uniformly outfitted with marine diesel engines.
The full integrated electric propulsion for the new aircraft carrier might use gas turbine, diesel engine and the like for flexible power distribution and advanced propulsion. Three main prime movers exist; internal combustion engines, gas turbines and steam turbines. Nuclear powered or oil fired boiler powered steam cycles are used with steam turbines according to the vessel type.
The marine power plant is that part of the ship responsible for generating both mechanical and electrical power for the ship propulsion and various electric consumers. Usually, these two operations are achieved separately, but in some configurations both are performed together. The power plant may be of the electric type, where propulsion is done via electric motors, or the conventional type, where mechanical power from the prime mover drives the propulsion either directly or through a gearbox.
The diesel engines give good flexibility for the naval architect to achieve the required speed for a given ship with the best fuel economy. A ship propulsion system can consist of only one diesel engine and in some cases up to 12 engines - only for propulsion - especially in naval vessels requiring large propulsion flexibility and high redundancy. For the electric generation, the diesel engine is almost the only engine type used, even with other types of prime movers used for propulsion. Also the diesel engines have the best efficiency levels of all other means of propulsion with a range of 35% to 55%.
Since the year 2000, many vessels around the world were powered by gas turbines, but most of them use the gas turbine in a combined configuration to achieve a more feasible and flexible propulsion solution due to the high fuel consumption of gas turbines, these combined configurations include the combined diesel and gas (CODAG) where the required power is produced by both diesel engines and gas turbines at the same time and at part load only one type of engines is operated according to the required power. In the combined gas and steam (COGAS), the exhaust of the gas turbine is used to provide enough heat for steam generation.
China Shipbuilding Industry Corp said its Wuhan Institute of Marine Electric Propulsion finalized its Integrated Electric Propulsion technology in mid-July 2013. It said the in-house development will help the nation wean itself off the longstanding dependence on imported parts in manufacturing ships. Most surface vessels in China use mechanical transmissions and are propelled by a motor or an engine spinning a propeller. Many Western countries have adopted integrated electric propulsion, in which gas turbines or diesel generators produce electricity that powers electric motors.
The development of integrated electric propulsion may resolve engine problems that have long haunted the nation and its navy. One of the major issues has been a lack of domestic companies who can make gas turbine engines to support long distance voyages. Without domestically developed gas turbine engines, the Chinese navy had been forced to import foreign engines for its ships.
Steam power was used in old large surface warships. The Anshan class of the Soviet period had 2 steam turbines with a total of 48000 horsepower. The type 051 Luda-class guided missile destroyer was steam turbine powered with two Type 453 steam turbines, four sets of type 454 boilers [some sources report two sets], with a total power of 72,000 horsepower. The Type 051B/C destroyers had steam turbine power of Type 453B, with 2 units providing a total of 94,000 horsepower. The ex-Soviet Sovremenny class destroyers had steam turbine power, with 2 GTZA-674 units providing a total of 100,000-104,000 horsepower.
System evolution went from the Soviet TB-8 (on the Kotlin using 2 units, each with 36,000 horsepower), to the TB-12 (subsequent models used on the Varyag / Liaoning, with 4 units each providing 45,000 horsepower) to the TB-12 improved GTZA-674 (Sovremenny level using 2, each with 50,000 horsepower). China's Type 453 (imitation TB-8 051 using two units, a single 36000 HP) and Type 453B (453 development type 051C/051B using two single 47,000 horsepower).
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