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Ebook Power plant engineering (3e): Part 2

(BQ) Part 2 book "Power plant engineering" has contents: Steam turbines, condenser, feed water and circulating water systems, nuclear power plants, hydroelectric power plant, diesel engine and gas turbines power plants, energy storage, non conventional power generation, environmental degradation and use of renewable energy. | Steam Turbines 7.1 I INTRODUCTION A steam turbine is a prime mover which continuously converts the energy of high-pressure high temperature steam supplied by a steam generator into shaft work with the low temperature steam exhausted to a condenser. This energy conversion essentially occurs in two steps 1. The high-pressure high-temperature steam first expands in nozzles and comes out at a high velocity. 2. The high velocity jets of steam coming out of the nozzles impinge on the blades mounted on a wheel get deflected by an angle and suffer a loss of momentum which is absorbed by the rotating wheel in producing torque. X steam turbine is basically an assemblage of nozzles and blades. The Greek inventor Hero of Alexandria built the first prototype of a steam turbine in 120 BC which operated on the reaction principles. A simple closed spherical vessel mounted on bearings carrying steam from a cauldron or boiler with four tangential pipes discharging steam is driven around by the reaction of the steam jets Fig. 7.1 a . Many centuries later Giovanni Branca made the prototype of the impulse steam turbine in 1629 which is often referred to as the Branca s wheel. In 1878 a Swedish engineer Carl Gustav Patrik de Laval 1845-1913 developed a simple impulse turbine to separate cream from milk using a convergent-divergent supersonic nozzle which ran the turbine to a maximum speed of 100 000 rpm. He constructed in 1897 a velocity-compounded impulse turbine a two-row axial turbine with a row of guide vane stators between them all fed by a single set of high velocity nozzles . In France Auguste Rateau 1863-1930 experimented with a de Laval turbine in 1894 and developed the pressure compounded impulse turbine by 1900. Copyrighted material Steam Turbines Fig. 7.1 a Hero s turbine In the USA Charles G. Curtis 1860-1953 patented in 1896 the velocity-compounded turbine similar to a two-stage de Laval turbine but after further development he sold all his rights to General Electric in .