Basic knowledge about Francis Turbine:
Francis turbine is a type of water turbine that was developed by American
engineer James B. Francis in the mid-1800s. It is a reaction turbine, which
means that it uses both the weight and velocity of the water to generate power.
Francis turbine is commonly used in hydroelectric power plants to generate
electricity from the energy of falling water. The turbine consists of a spiral
casing, a runner with curved blades, and a shaft that connects the runner to a
generator. Water enters the casing and flows through the blades of the runner,
causing the runner to rotate. The rotation of the runner is transferred to the
generator, which then produces electricity.
turbines are efficient and can be used in a wide range of water conditions.
They can generate power from low head (drop) installations to high head
installations, making them a versatile choice for hydroelectric power
generation. They are also commonly used in pumped storage power plants, which
store energy by pumping water uphill during off-peak hours and then releasing
it through the turbines during peak demand.
Overall, the Francis turbine has played an important role in the development of hydroelectric power and continues to be a widely used technology for generating clean and renewable energy.
The main part of Francis Turbines
Francis turbine consists of several main parts that work together to generate
power from water:
- Spiral Casing: The spiral
casing is a stationary, spiral-shaped housing that surrounds the runner.
It directs water from the penstock (pipe) towards the runner, while also
converting the water's pressure into kinetic energy.
- Runner: The runner is the
rotating part of the turbine and consists of a hub and curved blades.
Water enters the runner and is directed by the blades towards the shaft.
As the water flows through the runner, it transfers its kinetic energy to
the runner, causing it to rotate.
- Shaft: The shaft is a
component that connects the runner to the generator. As the runner
rotates, it turns the shaft, which in turn rotates the generator.
- Guide Vanes: Guide vanes are
adjustable blades located in the spiral casing that regulate the flow of
water into the runner. By adjusting the angle of the guide vanes, the
operator can control the turbine's output and efficiency.
- Draft Tube: The draft tube is
a cone-shaped tube located below the runner that helps to increase the
efficiency of the turbine. As the water exits the runner, it flows through
the draft tube, which reduces the velocity of the water and converts its
kinetic energy into pressure energy. This pressure energy is then used to
help drive the turbine.
Overall, these main parts work together to convert the potential energy of falling water into mechanical energy, which is then converted into electrical energy by the generator.
Types of Francis Turbine:
several different types of Francis turbines, which are classified based on
their design and specific application. Some common types include:
- High Head Francis Turbine:
This type of Francis turbine is designed to operate at high head (or drop)
installations, typically over 100 meters. High head Francis turbines have
a smaller runner diameter and more curved blades to maximize efficiency at
- Medium Head Francis Turbine:
Medium head Francis turbines are designed for installations with head
ranges between 30 and 100 meters. They have a larger runner diameter and
fewer blades than high head turbines, allowing them to operate at lower
speeds and higher flow rates.
- Low Head Francis Turbine: Low
head Francis turbines are designed for installations with head ranges
below 30 meters. They have a larger runner diameter and fewer blades than
medium head turbines, allowing them to operate at even lower speeds and
higher flow rates.
- Reversible Francis Turbine:
Reversible Francis turbines are designed for use in pumped storage power
plants, which can store energy by pumping water uphill during off-peak
hours and then releasing it through the turbine during peak demand.
Reversible Francis turbines can operate in both directions, allowing them
to both generate and pump water.
- Compact Francis Turbine:
Compact Francis turbines are designed for small-scale hydropower
applications, such as in rural areas or remote locations. They have a
small footprint and are often installed in existing irrigation canals or
the type of Francis turbine used in a particular installation will depend on
factors such as the head and flow rate of the water, as well as the specific
requirements of the application.
Working principle of Francis Turbine:
working principle of a Francis turbine is based on the conversion of the
potential energy of falling water into mechanical energy, which is then
converted into electrical energy through a generator. The main components of a
Francis turbine include the runner, the wicket gates, and the draft tube.
Here is a
step-by-step overview of how a Francis turbine works:
- Water enters the turbine
through the intake and passes through the wicket gates, which are
adjustable vanes that control the flow of water into the turbine.
- The water then flows into the
runner, which is a series of curved blades attached to a central shaft.
The shape and curvature of the blades are designed to efficiently capture
the energy of the flowing water and transfer it to the central shaft.
- As the water flows over the
curved blades of the runner, it causes the runner and central shaft to
rotate at high speeds.
- The rotating shaft is
connected to a generator, which converts the mechanical energy of the
turbine into electrical energy.
- After passing through the
runner, the water flows out of the turbine and into the draft tube. The
draft tube is a large, tapered pipe that is designed to slow down the
velocity of the water and convert the remaining kinetic energy into
- The water then exits the draft
tube and flows back into the river or reservoir at a lower level.
Overall, the Francis turbine operates on the principle of converting the kinetic energy of flowing water into mechanical energy through the use of curved blades and a central shaft. The rotating shaft is then used to generate electrical energy through a connected generator, and the water is returned to the environment through a draft tube.
Advantages of Francis Turbine:
several advantages to using Francis turbines for hydroelectric power
- High Efficiency: Francis
turbines are highly efficient, typically operating at efficiencies of 90%
or higher. This means that they can convert a large percentage of the
energy in falling water into mechanical energy, which can then be
converted into electricity.
- Wide Range of Applications:
Francis turbines can be used in a wide range of head and flow conditions,
making them a versatile choice for hydroelectric power generation. They
can generate power from low head (drop) installations to high head
installations, and can be used in both small-scale and large-scale power
- Low Maintenance: Francis
turbines are relatively simple in design and have few moving parts, which
makes them easy to maintain and repair. They also have a long lifespan,
with some turbines still in operation after 50 years or more.
- Environmentally Friendly:
Hydroelectric power generation using Francis turbines is a clean and
renewable source of energy that produces no greenhouse gas emissions or
air pollution. It also has a minimal impact on aquatic ecosystems when
compared to other forms of power generation, such as fossil fuel power
- Reliable: Francis turbines
have a high level of reliability, with a proven track record of consistent
performance over many years of operation. This makes them a dependable
source of power for both grid-connected and off-grid applications.
Overall, the high efficiency, versatility, low maintenance, environmental friendliness, and reliability of Francis turbines make them an attractive choice for hydroelectric power generation.
Disadvantages of Francis Turbine:
turbines have many advantages for hydroelectric power generation, there are
also some disadvantages to consider, including:
- Limited Availability of
Suitable Sites: Francis turbines require a sufficient amount of flowing
water with a high enough head to operate efficiently. Suitable sites for
hydroelectric power generation using Francis turbines may be limited in
certain regions, which can make them less practical in those areas.
- High Capital Costs: The
initial capital costs of installing a Francis turbine can be high,
particularly for large-scale installations. This can make hydroelectric
power generation using Francis turbines less financially feasible for some
- Impact on Aquatic Ecosystems:
While hydroelectric power generation using Francis turbines is generally
considered to be environmentally friendly, the construction and operation
of hydroelectric facilities can still have some negative impacts on
aquatic ecosystems. These impacts can include changes in water flow and
temperature, and disturbance of aquatic habitats.
- Maintenance Requirements:
While Francis turbines are relatively simple in design and have few moving
parts, they still require regular maintenance to ensure optimal
performance. This maintenance can include tasks such as inspecting and
replacing bearings, lubricating moving parts, and cleaning debris from the
- Regulatory Requirements:
Hydroelectric facilities using Francis turbines are subject to a range of
regulatory requirements related to environmental impacts, public safety,
and operational standards. Compliance with these regulations can add
additional costs and complexity to hydroelectric power generation
Overall, while Francis turbines have many advantages for hydroelectric power generation, they also have some limitations and potential drawbacks that need to be carefully considered when evaluating their suitability for a particular project.
Application of Francis Turbine
turbines are used in a variety of hydroelectric power generation applications,
- Large-scale power plants:
Francis turbines are commonly used in large-scale hydroelectric power
plants that generate electricity for transmission to the grid. These
turbines can generate significant amounts of power and are often used in
conjunction with dams or other large water reservoirs.
- Run-of-river power plants:
Francis turbines are also used in run-of-river power plants, which
generate electricity from flowing water without the need for a dam or
reservoir. These turbines can operate efficiently at lower heads and flow
rates, making them ideal for smaller-scale hydroelectric projects.
- Pumped storage power plants:
Francis turbines are also used in pumped storage power plants, which
generate electricity by pumping water from a lower reservoir to a higher
reservoir during periods of low demand, and then releasing the water to
generate electricity during periods of high demand.
- Industrial applications:
Francis turbines can also be used for industrial applications such as
water supply systems, irrigation systems, and process cooling systems.
Overall, Francis turbines are a versatile and efficient technology for generating electricity from flowing water, and are widely used in a variety of hydroelectric power generation applications.
Difference between Francis Turbine and Kaplan Turbine
and Kaplan turbines are both types of hydroelectric turbines used to generate
electricity from flowing water, but there are several key differences between
- Blade Design: The blades of a
Francis turbine are fixed and have a curved shape, while the blades of a
Kaplan turbine are adjustable and have a variable pitch angle. This allows
the angle of the blades to be adjusted to optimize the turbine's
efficiency for different flow conditions.
- Water Head: Francis turbines
are designed to operate with a medium to high head of water, typically
ranging from 20 to 600 meters. In contrast, Kaplan turbines are designed
to operate with a lower head of water, typically ranging from 2 to 60
- Water Flow: Francis turbines
are more efficient at high head and low flow rates, while Kaplan turbines
are more efficient at low head and high flow rates.
- Turbine Orientation: Francis
turbines have a vertical axis and are typically larger than Kaplan
turbines, which have a horizontal axis.
- Cost: The cost of a Francis
turbine is generally higher than that of a Kaplan turbine due to their
larger size and more complex design.
Overall, the choice between a Francis or Kaplan turbine will depend on factors such as the available water resources, the size and capacity of the hydroelectric power generation project, and the specific needs of the application. While Francis turbines are better suited for high head applications, Kaplan turbines are more suitable for low head applications.
Type of Francis Turbine
several types of Francis turbines, including:
- Spiral casing Francis turbine:
This is the most common type of Francis turbine, and it features a
spiral-shaped casing that guides the water to the turbine blades. The
spiral casing is designed to reduce the water velocity and direct the flow
of water towards the blades, improving the efficiency of the turbine.
- Draft tube Francis turbine: In
this type of Francis turbine, a draft tube is added to the turbine outlet
to increase the pressure at the turbine exit and reduce the losses due to
swirling and turbulence. This type of Francis turbine is particularly
effective at low head applications.
- Open flume Francis turbine:
This type of Francis turbine is used in low head, high flow applications,
and features an open flume that allows the water to flow freely through
the turbine. The open flume design reduces the pressure drop across the
turbine, improving efficiency.
- Vertical Francis turbine: In
this type of Francis turbine, the axis of rotation is vertical, and the
water flows from the top of the turbine to the bottom. Vertical Francis
turbines are commonly used in low head applications, and they offer a
compact and space-saving design.
- Reverse Francis turbine: This
type of Francis turbine is used in pumped storage power plants, where
water is pumped from a lower reservoir to a higher reservoir during
periods of low demand, and then released to generate electricity during
periods of high demand. The reverse Francis turbine is designed to operate
in both directions, allowing it to function effectively as both a turbine
and a pump.
Each type of Francis turbine is designed to optimize performance under specific operating conditions, and the selection of a particular type depends on factors such as the head, flow rate, and power output of the hydroelectric power generation system.
Francis Turbine Formula
formula for calculating the power output of a Francis turbine is:
P = (ρQHη)/ 1000
- P is the power output in
is the density of water in kilograms per cubic meter (kg/m³)
- Q is the volumetric flow rate
of water in cubic meters per second (m³/s)
- H is the net head of water in
is the efficiency of the turbine (expressed as a decimal, not a
This formula can be used to calculate the power output of a Francis turbine under various operating conditions. Note that other factors such as the specific speed, blade angle, and number of blades can also impact the performance of the turbine, but these are not included in the basic formula.
Francis Turbine Efficiency
efficiency of a Francis turbine depends on a number of factors, including the
design of the turbine, the operating conditions, and the efficiency of the
generator. Generally speaking, Francis turbines have efficiencies ranging from
85% to 95%, with the highest efficiencies typically achieved at or near the
turbine's rated capacity.
that can impact the efficiency of a Francis turbine include the specific speed
of the turbine, the blade design, the number of blades, and the size and shape
of the turbine's draft tube. Additionally, factors such as cavitation, blade
erosion, and water quality can also impact the efficiency of the turbine over
maximize the efficiency of a Francis turbine, it is important to design the
turbine to match the specific operating conditions and to maintain the turbine
and associated equipment regularly. Additionally, modern turbine designs often
include advanced features such as computerized control systems, adjustable
blades, and optimized blade shapes to further improve efficiency and