WATER TURBINES.
Turbines:-
They are the mechanical powerhouses driving various industries and generating energy, stand as pivotal
components in modern engineering. They harness the kinetic energy from various sources, water turbines, steam
turbines, gas turbines, and wind turbines play instrumental roles in converting this energy into useful forms like
electricity or mechanical power.
They consist of blades or a rotor that spins when exposed to a moving fluid. Turbines are widely used in various
applications, like generating electricity in power plants, powering aircraft engines, producing propulsion for
ships, and even extracting energy from wind.
Water Turbine
A water turbine is a machine that converts the energy of flowing water into mechanical energy, which is then
used to generate electricity.
Turbines operate on the principle of energy conversion of a moving fluid or gas into rotational mechanical
energy.
Water
turbine
How it works Converts the kinetic and potential energy of water into mechanical work
Uses Primarily used in power plants to generate electricity
History Developed in the 19th century, and were widely used for industrial power before
electrical grids
Types The two main types are reaction and impulse
Disadvantages Can be expensive to install, require a lot of infrastructure, and can be damaged by debris
How they work
Water turbines are similar to windmills, but use falling water instead of wind. The water's gravitational potential
energy is converted into kinetic energy, and then the momentum of the water is used to create a peripheral force.
CLASSIFICATION OF WATER TURBINES.
Water turbines are classified by their type of operation, which is either IMPULSE or REACTION, and the type
of turbine used depends on the flow and height of water at the site.
(1) IMPULSE TURBINES
In hydroelectric power plants, impulse turbines are a type of water turbine that use the energy of moving water
to make electricity. They operate based on the principle of converting the kinetic energy of water into
mechanical energy, which is then transformed into electrical energy.
Impulse turbines come in two categories:
A: Pelton turbine
The Pelton wheel or Pelton Turbine is an impulse-type water turbine invented by American inventor Lester
Allan Pelton in the 1870s. It is used in high-head, low-flow power plants. On the runner of the turbine, there is
a spoon-shaped bucket that directs the strong, fast water from the nozzle to turn the drive wheel against the
rotating series. When the high-speed water strikes the bucket blades, they begin to move anticlockwise. The
Pelton wheel performs best when the drop height is 50–2000 m and the flow rate is 4–15 m3/s.
Application of Pelton Turbine
Pelton turbine is used in the hydroelectric power plant where the water available at high head i.e. 150 m to 2000
m or even more. In a hydroelectric power plant, it is used to drive the generator attached to it and the generator
generates the mechanical energy of the turbine into electrical energy.
Advantages of Pelton Turbine
• It is easy to maintain.
• There is no cavitation problem in the Pelton turbine.
• Pelton turbine has a simple construction.
• It can work on the high head and low discharge.
• It is very easy to assemble.
• The overall efficiency of this turbine is very high.
Disadvantages of Pelton Turbine
• Pelton Turbine requires a very high head for operation.
• The efficiency decreases quickly with time.
• Its turbine size is generally large and hence requires a large space.
• As it only works in the high head, it is difficult to control vibrations in the operating head.
B: Cross-flow turbine
Anthony Michel invented the Crossflow turbine in 1903, and it is used in low heads of 10-70 meters with a
power output of 5-100 kW. The cross-flow turbine is a low-speed machine that is well suited for locations with
a low head but high flow. This turbine obtains energy by reducing water velocity while maintaining pressure,
which is why cross-flow turbines are a good example of impulse turbines. It's also known as a Bánki-Michell
turbine or Ossberger turbine.
Unlike most water turbines, which have axial or radial flows, in a cross-flow turbine the water passes through
the turbine transversely, or across the turbine blades.
(2) REACTION TURBINES
Reaction turbines produce torque by responding to pressure or by accelerating water flow.
A reaction turbine, as the name implies, operates on the principle of reaction force, which is felt by the turbine
blades when water flows over them.
The first set of blades in the reaction turbine is fixed and convert water pressure energy into kinetic energy.
Water then flows through the runner blades. The moving blades are shaped like an aerofoil.
Reaction turbines fall into two categories:
A: Francis Turbine
Francis turbines are the most common water turbine in use today, and can achieve over 95% efficiency.[ The
main components of the Francis turbine are:
• Volute casing
• Runner blades
• Guide vanes
• Draft tube
Water flows from the cashing through the guide vanes, which are arranged on the periphery to direct the water
to the runner blades.
Water enters the rotor blades radially through the guide vanes. The Francis turbine’s runner is unique in design.
Because of the pressure difference created by the aerofoil structure, water begins to rotate as it enters radially.
The entire pressure energy of the water is converted into kinetic energy during the process, so the water, after
passing through the runner process, is at low pressure.
When the water flows over the blades, the kinetic energy is converted as well. The energy from the turbine is
determined by the net pressure difference from the inlet to the outlet.
B: Kaplan Turbine
Water enters the Kaplan turbine through the casing and flows through the guide blade.
In the axial portion, water enters the runner blades. The runner blades are designed for specific aerofoil
structures, such as those used in the Francis turbine.
Wind Turbine
Wind power generation, as the name suggests, is a device that converts kinetic energy from the wind into
electrical power.
Wind energy works on a simple principle: a series of sails and blades mounted around a rotor catch the wind
and convert its kinetic energy into rotational energy, producing electricity.
Wind turbines have two categories
1. Horizontal axis machines
2. Vertical-axis machines
(1) Horizontal axis machines
Horizontal-axis machines typically refer to turbines or windmills where the main rotor shaft and electrical
generator are aligned horizontally. In the context of wind turbines, horizontal-axis wind turbines (HAWTs) are
the most commonly used type today.
(2) Vertical-axis machines
Vertical-axis machines refer to a type of wind turbine where the main rotor shaft is arranged vertically. Unlike
horizontal-axis wind turbines, which have blades rotating around a horizontal axis, vertical-axis turbines have
blades that spin around a vertical axis.
Advantages of wind energy
1. Wind is a type of clean energy
2. Wind is a renewable energy source
3. Wind power has a low operating cost
4. Wind turbines save space
Disadvantages of Wind Energy
1. Wind turbines can be dangerous to some wildlife
2. Wind turbines can be noisy
3. Wind power is limited by location
