Dryness fraction of steam pdf

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A steam turbine is a device 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 Sir Charles Parsons in 1884. United States in the year 1996 was by use of steam turbines. The first device that may be classified as a reaction steam turbine was little more than a toy, the classic Aeolipile, described in the 1st century by Hero dryness fraction of steam pdf Alexandria in Roman Egypt.

The modern steam turbine was invented in 1884 by Sir Charles Parsons, whose first model was connected to a dynamo that generated 7. A number of other variations of turbines have been developed that work effectively with steam. De Laval’s impulse turbine is simpler, less expensive and does not need to be pressure-proof. The Brown-Curtis turbine, an impulse type, which had been originally developed and patented by the U. It was used in John Brown-engined merchant ships and warships, including liners and Royal Navy warships.

The present-day manufacturing industry for steam turbines is dominated by Chinese power equipment makers. Turbine blades are of two basic types, blades and nozzles. Blades move entirely due to the impact of steam on them and their profiles do not converge. This results in a steam velocity drop and essentially no pressure drop as steam moves through the blades. Nozzles appear similar to blades, but their profiles converge near the exit.

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This results in a steam pressure drop and velocity increase as steam moves through the nozzles. Nozzles move due to both the impact of steam on them and the reaction due to the high-velocity steam at the exit. Except for low-power applications, turbine blades are arranged in multiple stages in series, called compounding, which greatly improves efficiency at low speeds. A reaction stage is a row of fixed nozzles followed by a row of moving nozzles. A major challenge facing turbine design was reducing the creep experienced by the blades. Because of the high temperatures and high stresses of operation, steam turbine materials become damaged through these mechanisms. As temperatures are increased in an effort to improve turbine efficiency, creep becomes significant.