A reaction turbine has a gradual pressure drop over fixed and moving blades, utilizing both impulse and reactive forces. Steam expands through multiple stages of stationary and rotating blades, gradually increasing in volume and decreasing in pressure. More stages are needed compared to impulse turbines of the same capacity due to the pressure drops at each stage. Compounding methods like velocity, pressure, and pressure-velocity compounding are used to reduce the rotor speed to an optimum value by absorbing steam pressure or velocity in stages.
A turbine is a rotary mechanical device that extracts energy from a fast moving flow of water, steam, gas, air, or other fluid and converts it into useful work. Also a turbine is a turbo-machine with at least one moving part called a rotor assembly, which is a shaft or drum with blades attached. Moving fluid acts on the blades so that they move and impart rotational energy to the rotor. According to the fluid used:
• Water Turbine
• Steam Turbine
• Gas Turbine
• Wind Turbine
Although the same principles apply to all turbines, their specific designs differ sufficiently to merit separate descriptions.
Working Principle Water Turbine
• When the fluid strikes the blades of the turbine, the blades are displaced, which produces rotational energy.
• When the turbine shaft is directly coupled to an electric generator mechanical energy is converted into electrical energy.
• This electrical power is known as hydroelectric power.
In a hydraulic turbine, water is used as the source of energy. Water or hydraulic turbines convert kinetic and potential energies of the water into mechanical power. Water turbines are mostly found in dams to generate electric power from water kinetic energy.
Classification
Based on hydraulic action of water
Based on direction of flow
Based on head of water and quantity of flow
Based on specific speed
Based on disposition of turbine shaft
Based on name of originator (commonly used turbines)
A turbine is a rotary mechanical device that extracts energy from a fast moving flow of water, steam, gas, air, or other fluid and converts it into useful work. Also a turbine is a turbo-machine with at least one moving part called a rotor assembly, which is a shaft or drum with blades attached. Moving fluid acts on the blades so that they move and impart rotational energy to the rotor. According to the fluid used:
• Water Turbine
• Steam Turbine
• Gas Turbine
• Wind Turbine
Although the same principles apply to all turbines, their specific designs differ sufficiently to merit separate descriptions.
Working Principle Water Turbine
• When the fluid strikes the blades of the turbine, the blades are displaced, which produces rotational energy.
• When the turbine shaft is directly coupled to an electric generator mechanical energy is converted into electrical energy.
• This electrical power is known as hydroelectric power.
In a hydraulic turbine, water is used as the source of energy. Water or hydraulic turbines convert kinetic and potential energies of the water into mechanical power. Water turbines are mostly found in dams to generate electric power from water kinetic energy.
Classification
Based on hydraulic action of water
Based on direction of flow
Based on head of water and quantity of flow
Based on specific speed
Based on disposition of turbine shaft
Based on name of originator (commonly used turbines)
A steam turbine is a prime mover in which the potential energy of the steam is transformed into kinetic energy and later in its turn is transformed into the mechanical energy of rotation of the turbine shaft
2. Reaction Turbine
In this type of turbine, there is a
gradual pressure drop and takes place
continuously over the fixed and moving
blades. The rotation of the shaft and drum,
which carrying the blades is the result of
both impulse and reactive force in the
steam. The reaction turbine consist of a
row of stationary blades and the following
row of moving blades
2
3. The fixed blades act as a nozzle which
are attached inside the cylinder and the
moving blades are fixed with the rotor as
shown in figure
When the steam expands over the
blades there is gradual increase in
volume and decrease in pressure. But
the velocity decrease in the moving
blades and increases in fixed blades with
change of direction.
3
4. Because of the pressure drops in each
stage, the number of stages required in a
reaction turbine is much greater than in a
impulse turbine of same capacity.
It also concluded that as the volume
of steam increases at lower pressures
therefore the diameter of the turbine must
increase after each group of blade rings.
4
7. PRESSURE-VELOCITY DIAGRAM FOR
A MOVING REACTION BLADE
TURBINE
SHAFT
DIRECTION OF SPIN
ENTRANCE
HIGH PRESSURE
HIGH VELOCITY
STEAM INLET
REPRESENTS MOVING
REACTION BLADES
EXIT
LOW PRESSURE
LOW VELOCITY
STEAM EXHAUST
PRESSURE
VELOCITY
2
8. .Compounding in Steam Turbine.
The compounding is the way of
reducing the wheel or rotor speed of the
turbine to optimum value. It may be
defined as the process of arranging the
expansion of steam or the utilization of
kinetic energy or both in several rings.
9. There are several methods of reducing the
speed of rotor to lower value. All these
methods utilize a multiple system of rotors
in series keyed on a common shaft, and
the seam pressure or jet velocity is
absorbed in stages as the steam flower
over the blades.
10. Different methods of compounding are:
1.Velocity Compounding
2.Pressure Compounding
3.Pressure Velocity Compounding.
These are explained in detail as given
below:
