Q4 - Comparison of Turbines Flashcards
Explain the operation and performance of a Kaplan turbine. Including design and performance parameters
Kaplan Turbine:
Operation: The Kaplan turbine is a propeller-type turbine with adjustable blades. It is designed to operate in low to medium head conditions and is particularly suitable for sites with varying water flow. The blades can be adjusted to optimize performance under different flow rates and head conditions.
Performance: Kaplan turbines are known for their high efficiency over a wide range of flow rates. They are suitable for low head (fall) conditions and are commonly used in hydroelectric power plants where the water flow is variable.
Pelton Turbine:
Head Range -
Low to medium head conditions. 2 -25m
At high flow rate (70-800 m3/s)
Blade Type -
Kaplan turbines have adjustable blades to optimize performance under varying flow conditions.
They are known for their ability to
maintain high efficiency over a wide range of flow rates and heads due to their adjustable runner blades
Application -
Kaplan turbines are commonly used in river-based hydroelectric plants with variable flow.
Explain the operation and performance of a Francis turbine. Including design and performance parameters
Francis Turbine:
Operation: The Francis turbine is a reaction turbine that combines both impulse and reaction principles. Water enters the turbine through spiral scroll casing, and the blades are designed to operate in both the impulse and reaction zones. This makes the Francis turbine versatile and suitable for a wide range of head and flow conditions.
Performance: Francis turbines are adaptable to medium to high head conditions and are widely used in hydroelectric power plants. They offer good efficiency across a range of operating conditions and are commonly employed in locations where both head and flow vary.
Head Range-
Francis turbines cover a broad range of head conditions, from medium to high.
Blade Type-
Francis turbines have blades that operate in both the impulse and reaction zones.
They have an efficiency range of 85%–95%. Such efficiency is highly dependent on both the flow rate and net head.
Application -
Francis turbines are versatile and widely used in various hydroelectric power plants with medium to high head conditions.
Explain the operation and performance of a Pelton turbine. Including design and performance parameters
Pelton Turbine:
Operation: The Pelton turbine is an impulse turbine that uses the kinetic energy of high-velocity water jets. It consists of a runner with spoon-shaped buckets. Water is directed onto the buckets, and the impulse of the water causes the runner to rotate.
Performance: Pelton turbines are most effective in high head conditions. They are well-suited for mountainous regions with high altitude where there is a significant drop in elevation. Pelton turbines are known for their high efficiency in converting the energy of high-velocity water jets into mechanical energy.
Head Range
Pelton turbines are suitable for high head conditions. (300-400m)
At Low Flow Rate
Blade Type
Pelton turbines have spoon-shaped buckets to capture the kinetic energy of high-velocity jets.
However, efficiency can decrease significantly if the
number of nozzles or the flow rate deviates too far from the optimal design point.
Application -
Pelton turbines are preferred for high-head installations in mountainous areas.
Use the comparison table to confirm the suitable type of turbine that operate at certain water velocities and head heights.
Draw a graph comparing the three turbines relationship with operating efficiency and Ns (specific speed)
Draw a velocity triangle of a francis turbine
Steps
1 - Determine direction of rotatation
2- Connect Point 1 to the centre of direction. Do same for point 2.
Draw a perpendicular line from the centre point in the direction of the flow
label this line U1 and U2
3- Draw a line tangent to the direction of the blades. Label each line W1 and W2
W2 must be longer than w1
4 - Using these new lines, form a parellogram. Connect two opposite corners and label C1 and C2
