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Steam Turbines
Objectives To illustrate the role of a steam turbine in a power plant To compare the two types of steam turbines To explain compounding & three methods adopted for compounding
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The General James M Gavin Steam Power Plant ,Ohio full capacity: 2,600,000kW
Well simplify the power plant3 BOILER 2 TURBINE
qin4 CONDENSER 1 PUMP
wout
qout8
win
Steam Turbine in a steam power plant
The two types !!!!!!!!
Impulse Turbine
Reaction Turbine
Pressure & Velocity Variation
Blade profileImpulse (Symmetric) Reaction (Non-symmetric)
Simple Impulse Turbine
Reaction Turbine
Reaction turbine
Rotor of a Reaction Turbine (Simulation)
Real World Turbines
Drawbacks of simple impulse turbine Whole expansion in one nozzle resulting in very high rotational speeds of the turbine rotor (upto 30,000 rpm) High exit (lost) velocity of steam - - - - - Compounding of Impulse Turbines
Compounded Steam Turbines Compounded steam turbine means multistage turbine. Compounding is needed when large enthalpy drop is available. Compounding can be achieved either by velocity compounded turbine or pressure compounded turbine.
Velocity Compounded Impulse Turbine The velocity compounded turbine was first proposed by C.G Curtis. It is composed of one stage of nozzles, as the single stage turbine, followed by two rows of moving blades instead of one. These two rows are separated by one row of fixed blades which has the function of redirecting the steam leaving the first row of the moving blades to the second row of moving blades.
Velocity Compounded Impulse Turbine (Contd.) In Curtis turbine steam leaving the nozzle is utilized in both rows of moving blades instead of single raw as in the de-Laval turbine. The velocity remain almost constant across the fixed blades. Although the Curtis stage is composed of two rows of moving blades, a velocity compounded turbine can be composed of any number of such rows. All these rows are sharing in the same kinetic energy of
Velocity Compounded Impulse Turbine
Pressure Compounding Impulse Turbine Pressure compounding impulse turbine is a multistage impulse turbine where expansion in the fixed blades (nozzles) is achieved equally among the stages. This type of turbines is usually called as Rateau turbine
Pressure Compounded Impulse Turbine
Rateau turbine
Comparison Between Velocity and Pressure Compounding Impulse TurbinesVelocity CompoundingNot equal velocity drop for each stage No pressure drop per stage Non equal power per stage High friction losses due to high velocities Not recommended for more than two stages No problem with steam leak
Pressure CompoundingEqual velocity drop for each stage Not equal pressure drop per stage Equal power per stage Low friction losses due to reduced steam velocity Recommended for multistage Larger steam leak
Suitable for small turbines as well as only Suitable for large turbines for the first stage in large turbine
Pressure - Velocity Compounded Impulse Turbine