Francis turbine

The correct answer is option 'A' - Francis turbine.

The Francis turbine is a type of water turbine that is widely used in hydroelectric power plants for generating electricity. It is a reaction turbine, which means that the turbine blades are fully submerged in the water flow and the energy conversion occurs through both pressure and velocity changes.

Design and Components

The Francis turbine consists of several key components, including the runner, guide vanes, and the turbine shaft.

1. Runner: The runner is the main rotating component of the turbine. It is composed of a series of curved blades that are attached to a central hub. The runner is responsible for extracting energy from the water flow and converting it into rotational motion.

2. Guide Vanes: The guide vanes are fixed to the hub of the turbine and are not adjustable. They are designed to direct the water flow onto the runner blades at a specific angle. The angle of the guide vanes determines the efficiency and power output of the turbine. In a Francis turbine, the guide vanes are typically arranged in a spiral or helical pattern, allowing for better control over the water flow.

3. Turbine Shaft: The turbine shaft is connected to the runner and transfers the rotational motion to the generator, which converts it into electrical energy. It is designed to withstand the high rotational speeds and torque generated by the turbine.

Working Principle

The working principle of a Francis turbine involves the following steps:

1. Water enters the turbine through a spiral casing, which directs the flow onto the guide vanes.

2. The guide vanes control the flow direction and angle, redirecting the water onto the runner blades.

3. As the water strikes the runner blades, it exerts a force on them, causing the runner to rotate.

4. The rotational motion of the runner is transferred to the turbine shaft, which is connected to a generator.

5. The generator converts the mechanical energy into electrical energy, which can be used to power homes, businesses, and industries.

Advantages of Francis Turbine

- High efficiency: The Francis turbine is known for its high efficiency, especially in medium to high head applications.
- Wide operating range: It can operate efficiently over a wide range of water flow rates and heads.
- Compact design: The turbine has a compact design, making it suitable for installations with limited space.
- Low maintenance: The fixed guide vanes require minimal maintenance compared to adjustable guide vanes.

In conclusion, the Francis turbine is a type of low head turbine where the guide vanes are fixed to the hub of the turbine and are not adjustable. It is a widely used turbine in hydroelectric power plants due to its high efficiency, wide operating range, and compact design.