Mechanical Basics

What is Francis Turbine?

Francis Turbine is a type of water turbine that is used for hydroelectric power generation. It is Invented by James B. Francis in the mid-19th century, it consists of curved blades mounted on a rotating shaft. Water flows radially inward, and the blades efficiently convert the kinetic energy of the water into mechanical energy, which drives a generator to produce electricity.

What is Francis Turbine

Francis Turbines are versatile and suitable for a wide range of water flow and head conditions. Their ability to operate effectively with both high and low head variations makes them a popular choice in hydropower plants around the world.

Also Read:

  1. Kaplan Turbine
  2. Pelton Turbine

History of Francis Turbine

  • Francis Turbine is invented by James B. Francis in the 19th century.
  • Its design, introduced in the 1840s, featured curved blades for optimal water-to-mechanical energy conversion.
  • Widely adopted globally, it remains a key technology in hydropower, providing sustainable electricity through efficient water flow utilization.

Parts of Francis Turbine

The parts of Francis Turbine are

Spiral Casing:

Also known as the scroll casing, it guides the water from the penstock to the runner blades.

Runner:

The central rotating element with curved blades that convert the kinetic energy of water into mechanical energy is called as the Runner.

Guide Vanes:

Guide Vanes are positioned in the spiral casing, these adjustable vanes control and regulate the flow of water before it reaches the runner, optimizing turbine performance.

Shaft:

Shaft connects the runner to the generator, transmitting the mechanical energy generated by the turbine to produce electricity.

Bearings:

Bearings support the shaft, allowing it to rotate smoothly.

Draft Tube:

The draft tube is positioned below the runner that helps in efficiently redirecting water as it exits the turbine, reducing energy losses.

Wicket Gates:

Adjustable gates located at the entrance of the runner, controlling the amount of water that flows through the turbine and thus regulating its speed and power output.

Working of Francis Turbine

The Francis Turbine operates on the principle of converting the kinetic energy of flowing water into mechanical energy, which is then used to generate electricity. The working of Francis Turbine is as follows

Water Intake:

The process begins with water being diverted from a river or reservoir through a penstock (a pipe) to the turbine’s spiral casing.

Spiral Casing: 

The spiral casing or scroll casing directs the water tangentially into the runner. The shape of the casing helps in ensuring a uniform flow of water into the runner.

Guide Vanes:

As water enters the runner, it encounters adjustable guide vanes. The position of these vanes can be altered to control the flow of water and regulate the speed of the turbine. This is crucial for maintaining optimal efficiency across varying water flow conditions.

Runner Blades:

The water flows onto the runner, a central element with curved blades. The shape of the blades is designed to efficiently capture the kinetic energy of the water. The pressure of the water causes the runner to rotate.

Shaft Rotation:

The rotating runner is connected to a shaft, and as the runner spins, it imparts rotational motion to the shaft.

Generator Connection:

The rotating shaft is connected to a generator, usually through a gearbox, which increases the rotational speed to match the generator’s requirements. The generator converts the mechanical energy into electrical energy.

Draft Tube:

After passing through the runner, the water exits the turbine through a draft tube. The draft tube helps in smoothly redirecting the water downward, reducing the exit velocity and minimizing energy losses.

Power Generation:

The rotation of the generator produces electrical energy, which can then be transmitted to the power grid for distribution and use.

Also Read:

  1. Thermocouples and its types
  2. Reciprocating Pump

Advantages of Francis Turbine

The Francis Tubine has the ability to operate effectively with both high and low head variations, which makes them a popular choice in hydropower plants around the world. The advantages of francis turbines includes

  • Cost Effectivity Top of Form
  • Regulation of flow
  • Easy to maintain
  • Efficiency
  • Stability
  • Adopts the variable loads easily

Disadvantages of Francis Turbine

The Disadvantages of Francis turbine includes

  • Initial cost is high
  • Environmental impacts
  • Sedimentation Issues
  • Limited turndown ratio

Applications of Francis Turbine

The applications of Francis turbine are

  • Hydroelectric power plants
  • River based hydropower
  • Renewable energy integration projects
  • Municipal water supply
  • Irrigation systems

Conclusion

The Francis Turbine is well-suited for a wide range of water flow and head conditions, making it a versatile choice for hydroelectric power generation. The adjustable guide vanes and wicket gates allow for efficient operation across varying water flow rates, contributing to the turbine’s widespread use in hydropower plants worldwide.