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Pressure compounding is the method in which pressure in a
Pressure compounding is the method in which pressure in a steam turbine
A steam turbine is a machine 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 Charles Parsons in 1884. Fabrication of a modern steam turbin ...
is made to drop in a number of stages rather than in a single nozzle
A nozzle is a device designed to control the direction or characteristics of a fluid flow (specially to increase velocity) as it exits (or enters) an enclosed chamber or pipe.
A nozzle is often a pipe or tube of varying cross sectional area, a ...
. This method of compounding is used in Rateau and Zoelly
Heinrich Zoelly (1862–1937) was a Mexican-Swiss engineer. He developed steam turbines and turbine-driven locomotives and patented the geothermal heat pump in 1912.
Life and work
Heinrich Zoelly was the fifth child of Franz Xaver Zoelly. His fa ...
turbines.
Construction
The arrangement consists of a number of simple impulse turbines in series mounted on a common shaft. The exit steam from one turbine is made to enter the nozzle of the succeeding turbine. Each of the simple impulse turbines would then be termed a "stage" of the turbine. Each stage comprises its ring of nozzle and blades. The steam from theboiler
A boiler is a closed vessel in which fluid (generally water) is heated. The fluid does not necessarily boil. The heated or vaporized fluid exits the boiler for use in various processes or heating applications, including water heating, central h ...
passes through the first nozzle ring where its pressure
Pressure (symbol: ''p'' or ''P'') is the force applied perpendicular to the surface of an object per unit area over which that force is distributed. Gauge pressure (also spelled ''gage'' pressure)The preferred spelling varies by country and e ...
drops and velocity
Velocity is the directional speed of an object in motion as an indication of its rate of change in position as observed from a particular frame of reference and as measured by a particular standard of time (e.g. northbound). Velocity is a ...
increases. The high velocity jet steam is directed onto the first moving blades wherein nearly all of its velocity is absorbed. The steam pressure remains unaltered. The steam from the first ring of moving blades enters the second ring of nozzles where its pressure is further reduced and velocity increased again. The next ring of moving blades absorbs the velocity obtained from this second ring nozzle. The process is repeated in the remaining rings until the whole of the pressure has been absorbed.
Effect
The total pressure drop of the steam does not take place in the first nozzle, but is split equally between all the nozzle rings in the arrangement. The effect of absorbing the pressure drop in stages is to reduce the velocity of the steam entering the moving blades.See also
*Compound turbine A compound turbine is a steam turbine in which there are two casings, a high-pressure casing and a low-pressure casing, operating in concert to extract work from a single source of steam. The steam is partially expanded in the high-pressure casing, ...
*Impulse turbine
A turbine ( or ) (from the Greek , ''tyrbē'', or Latin ''turbo'', meaning vortex) is a rotary mechanical device that extracts energy from a fluid flow and converts it into useful work. The work produced by a turbine can be used for generating ...
*Steam turbine
A steam turbine is a machine 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 Charles Parsons in 1884. Fabrication of a modern steam turbin ...
*Compounding of steam turbines
Compounding of steam turbines is the strategies in which energy from the steam is extracted in a number of stages rather than a single stage in a turbine. A compounded steam turbine has multiple stages e.g it has more than one set of nozzles and ...
References
Steam turbines {{Mech-engineering-stub