1. What is a Hydraulic Turbine?
A hydraulic turbine is a rotary machine that converts the energy of flowing or falling water into mechanical energy, which is then usually converted into electrical energy using a generator.
It is one of the most important components in a hydroelectric power plant.
2. Working Principle of Hydraulic Turbine
Hydraulic turbines work on the principle of conservation of energy and Newton’s laws of motion.
- Water at a certain head (height) possesses potential energy
- When it flows, it gains kinetic energy
- This energy is transferred to the turbine runner blades
- The runner rotates, producing mechanical energy
In simple words:
Water energy → Mechanical energy → Electrical energy
3. Energy Conversion in Turbine
The energy transformation in a hydraulic turbine involves:
- Potential Energy → due to height of water
- Kinetic Energy → due to velocity of water
- Mechanical Energy → rotation of turbine shaft
- Electrical Energy → via generator
4. Main Components of Hydraulic Turbine
A hydraulic turbine mainly consists of:
(a) Runner
- Rotating part of the turbine
- Contains blades or buckets
- Converts water energy into mechanical energy
(b) Guide Vanes / Nozzle
- Directs water onto the runner
- Controls flow rate and direction
(c) Casing
- Encloses the turbine
- Prevents water leakage
- Ensures smooth flow
(d) Shaft
- Connects runner to generator
- Transmits mechanical power
(e) Draft Tube
- Located at the outlet
- Converts kinetic energy into pressure energy
- Improves efficiency
5. Classification of Hydraulic Turbines
Hydraulic turbines can be classified based on different criteria:
(1) Based on Energy at Inlet
- Impulse Turbine
- Uses only kinetic energy
- Example: Pelton wheel
- Reaction Turbine
- Uses both pressure and kinetic energy
- Example: Francis turbine, Kaplan turbine
(2) Based on Direction of Flow
- Tangential Flow Turbine (Pelton)
- Radial Flow Turbine (Francis – inward/outward)
- Axial Flow Turbine (Kaplan)
- Mixed Flow Turbine (Francis)
(3) Based on Head
- High Head Turbine (>250 m)
- Medium Head Turbine (60–250 m)
- Low Head Turbine (<60 m)
(4) Based on Specific Speed
- Low specific speed → Pelton
- Medium → Francis
- High → Kaplan
6. Types of Hydraulic Turbines
(a) Pelton Turbine (Impulse)
4
- Used for high head, low flow
- Water jet strikes buckets
- Simple design, high efficiency
(b) Francis Turbine (Reaction)
4
- Used for medium head
- Water flows radially then axially
- Most widely used turbine
(c) Kaplan Turbine (Reaction)
4
- Used for low head, high flow
- Propeller-type blades (adjustable)
- High efficiency for varying loads
7. Important Terminology
- Head (H): Height of water above turbine
- Discharge (Q): Flow rate of water
- Efficiency (η): Ratio of output power to input power
- Specific Speed (Ns): Determines type of turbine suitable
8. Applications of Hydraulic Turbines
- Hydroelectric power generation
- Irrigation systems
- Pumped storage plants
- Renewable energy systems
9. Advantages
- Renewable and eco-friendly
- High efficiency (up to 90%)
- Low operating cost
- Long service life
10. Disadvantages
- High initial cost
- Depends on water availability
- Environmental impact (ecosystem disturbance)
- Requires large infrastructure (dams)