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Francis turbine design parameters
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The design parameters for a Francis turbine include:
Flow rate: The amount of water flowing through the turbine.
Head: The height difference between the water source and the turbine's outlet.
Runner diameter: The size of the turbine's rotating component.
Blade angles: Angles of the blades relative to the direction of water flow.
Efficiency: The ratio of output power to input power, important for maximizing energy conversion.
Speed: Rotation speed of the turbine, usually determined by the generator it's connected to.
Materials: Selection of materials for durability and performance under varying conditions.
Cavitation: Preventing the formation of cavitation bubbles to avoid damage to the turbine.
These parameters are optimized based on factors like site conditions, energy output requirements, and economic considerations.
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Runner diameter in Francis turbine
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The runner diameter in a Francis turbine typically ranges from a few meters to over 10 meters, depending on the specific application and design requirements. Smaller turbines may have runner diameters in the range of 1 to 3 meters, while larger turbines for hydropower plants can have diameters exceeding 10 meters. The diameter is chosen to optimize the turbine's performance based on factors such as flow rate, head, and efficiency.
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Blade angles in Francis turbine
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The blade angles in a Francis turbine are crucial for efficient energy conversion. There are two primary angles:
Guide vane angle: Also known as the wicket gate angle, it controls the flow of water entering the turbine. Adjusting this angle regulates the amount of water flow, optimizing turbine performance under different operating conditions.
Runner blade angle: These angles determine how efficiently the turbine extracts energy from the water flow. The runner blade angle affects the interaction between the water and the turbine blades, influencing both the turbine's power output and its efficiency.
Both angles are carefully designed and optimized to maximize the turbine's efficiency across its operating range, balancing factors such as flow velocity, pressure distribution, and hydraulic losses.
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Francis turbine
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The Francis turbine is a type of water turbine used for generating electricity in hydroelectric power plants. It's a reaction turbine, meaning it operates by both impulse and reaction forces.
Here's how it works:
Water enters the turbine through the spiral casing and flows into the runner.
The runner consists of a series of curved blades that are shaped to efficiently capture the kinetic energy of the flowing water.
As the water flows over the curved blades, it changes direction and creates a reaction force that causes the runner to rotate.
The rotating runner is connected to a shaft, which is in turn connected to an electric generator.
As the runner rotates, it drives the generator, producing electricity.
Francis turbines are v
FRANCIS TURBINE WORKING PRINCIPLES AND APPLICATION
1. ARUSHA TECHNICAL COLLEGE
GROUP PRESENTATION ON FRANCIS TURBINE
GROUP 03 MEMBERS
S.NO STUDENT NAME ADMISSION NUMBER
1. SELEMANI SAKALLAH 22062213022
2. GODLISTEN JOHN NYARI 22062213018
3. MWINYI MOHAMEDI 22062213021
4. HENDRICH MUNISI 22062213045
5. AMOSI MMINZA 22062213012
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2. FRANCIS TURBINE
Qn.No 3: Francis turbine
a) Velocity triangle
b) Work done
c) Efficiency
d) Max efficiency
e) design parameters
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3. FRANCIS TURBINE
Francis turbine is an inward flow reaction turbine and used for medium heads.
The Francis turbine operates under medium heads (45-400 meters) and also
which are guiding types and it is employed to have medium discharge (10-700
cube meters per second).
Francis Turbine Main Parts or Construction:
The following main parts or Construction of Francis turbine are:
• Penstock
• Casing
• Guide Vanes
• Governing Mechanism
• Runner and Runner Blades
• Draft tube
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5. Penstock:
The penstock is also known as the Input pipe. The diameter lies between 1
to 10 meters. The penstock is a large size conduit that conveys water from
the upstream of the dam or reservoir to the turbine runner.
Casing:
The casing has a passage that is the closed type and has a cross-sectional
area gradually decreasing along the direction of the flow area and it
becomes maximum at the inlet and zeroes at the exit.
Guide Vanes:
These vanes direct the water onto the runner at an angle appropriate to the
design. The motion to them is given by means of a handwheel or
automatically by a governor.
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6. Governing Mechanism:
It changes the position of the guide blades/vanes to affect a variation in water
flow rate when the load conditions on the turbine changes.
Runner and Runner blades:
The driving force on the runner is both due to impulsive and reaction effects.
The number of runner blades will be around 16 to 24.
The modern Francis turbine is an inward mixed Flow reaction turbine. Water
comes to the turbine via penstock and it will hit on no. of stationary blades.
These stationary orifices are commonly called as guide vanes or wicket gates.
The head acting on the turbine is partly transformed into kinetic energy and the
rest remains as pressure head. Due to this pressure difference, it is called a
reaction turbine and is responsible for the motion of the runner that is why a
Francis turbine is also known as a reaction turbine.
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7. The Francis turbine the pressure at the inlet is more than at the outlet.
After doing the work the water is discharged to the tailrace through a
closed of gradually enlarging section like a tube. This is known as the
draft tube.
Draft Tube:
It is an expanding tube used to discharge water through the runner and to
the tail race. The main function of the tube is to reduce the velocity of
(water flowing) at the time of discharge.
There are 3 types of draft tube:
• Conical Draft tube
• Elbow Draft Tube
• Moody Spreading Draft Tube
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9. Theory of operation
The Francis turbine is a type of reaction turbine, a category of turbine in
which the working fluid comes to the turbine under immense pressure and
the energy is extracted by the turbine blades from the working fluid. A
part of the energy is given up by the fluid because of pressure changes
occurring in the blades of the turbine, quantified by the expression of
degree of reaction, while the remaining part of the energy is extracted by
the volute casing of the turbine. At the exit, water acts on the spinning
cup-shaped runner features, leaving at low velocity and low swirl with
very little kinetic or potential energy left. The turbine's exit tube is shaped
to help decelerate the water flow and recover the pressure.
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11. Application:
Francis turbines may be designed for a wide range of heads and flows.
This, along with their high efficiency, has made them the most widely
used turbine in the world. Francis type units cover a head range from 40
to 600 m (130 to 2,000 ft), and their connected generator output power
varies from just a few kilowatts up to 800 MW. Large Francis turbines
are individually designed for each site to operate with the given water
supply and water head at the highest possible efficiency, typically over
90%.
In contrast to the Pelton turbine, the Francis turbine operates at its best
completely filled with water at all times. The turbine and the outlet
channel may be placed lower than the lake or sea level outside,
reducing the tendency for cavitation.
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12. In addition to electrical production, they may also be used for pumped
storage, where a reservoir is filled by the turbine (acting as a pump)
driven by the generator acting as a large electrical motor during periods
of low power demand, and then reversed and used to generate power
during peak demand. These pump storage reservoirs act as large energy
storage sources to store "excess" electrical energy in the form of water
in elevated reservoirs. This is one of a few methods that allow
temporary excess electrical capacity to be stored for later utilization.
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20. FRANCIS TURBINE- EFFICIENCY
There are 3 main efficiency of Francis turbine:
1. Mechanical
2. Hydraulic and
3. Overall Efficiency
Lets study the definition and formula,
Mechanical Efficiency:
This can be defined as the ratio of shaft power available at the turbine to the power
developed by the runner.
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