What Is a Water Turbine?
A water turbine is used for hydraulic power generation at dams and other facilities. It is typically installed where large amounts of water fall from high locations, such as waterfalls and dams, or where water is moving at high velocities, such as in rapids. The turbine is rotated by this flow, converting the energy into electricity.
Water turbines are classified as either impulse turbines or reaction turbines, based on how the falling water causes the blades to rotate. Impulse turbines, like the Pelton turbine, use the velocity of falling and accelerated water, while reaction turbines, like Francis and propeller turbines, use both the velocity and pressure of the water.
Types and Structure of Water Turbine
Modern water turbines convert the potential energy of water into velocity energy, applying high-speed water to the blades. There are two main types: impulse turbines and reaction turbines. The Pelton turbine is an example of an impulse turbine, while Francis and propeller turbines are examples of reaction turbines.
These turbines have a significant generating capacity, and even a 1% change in efficiency can greatly impact output. Optimal design is necessary based on the power plant size and the height of the waterfall.
Impulse Turbine
The Pelton turbine, a common type of impulse turbine, is used in power plants with large drop-offs and high water velocities. It directs a strong jet of water against turbine blades to rotate the turbine. Pelton turbines are known for their use in high-drop locations like the Boudron power plant in Switzerland.
Reaction Turbine
Francis and propeller turbines are reaction turbines. The Francis turbine uses both the velocity and pressure of falling water, with water entering a spiral-shaped casing and flowing through guide vanes before contacting the runners. Francis turbines are versatile, suitable for a range of drop-offs, and are widely used in Japan.
Propeller turbines, similar in principle to Francis turbines but differing in runner shape, are often used in power plants with smaller water drops and high flow rates. They are increasingly popular in micro-hydroelectric power generation.
Water Turbine and Hydropower Generation
Water turbines are connected to generators, and their rotation generates electricity. The rotation speed varies with water volume and level drop, necessitating measures to stabilize electricity output, such as adding air or water to the casing’s vortex center.