Alternative Energy Hydroelectric Generator 500KW Francis Turbine Generator in Uzbekistan

Francis turbine definition is a combination of both impulse and reaction turbine, where the blades rotate using both reaction and impulse force of water flowing through them producing electricity more efficiently. Francis turbine is used for the production of electricity most frequently in medium or large-scale hydropower stations.
These turbines can be used for heads as low as 2 meters and as high as 300 meters. Additionally, these turbines are beneficial as they work equally well when positioned horizontally as they do when they are oriented vertically. The water going through a Francis turbine loses pressure, but stays at more or less the same speed, so it would be considered a reaction turbine.

The description of each Francis turbine’s main component diagram is as follows.

Spiral Casing
The spiral casing is the inlet medium of water to the turbine. The water flowing from the reservoir or dam is made to pass through this pipe with high pressure. The blades of the turbines are circularly placed, which means the water striking the turbine’s blades should flow in the circular axis for efficient striking. So the spiral casing is used, but due to the circular movement of the water, it loses its pressure.
To maintain the same pressure the diameter of the casing is gradually reduced, thus, uniform momentum or velocity striking the runner blades.

Stay Vanes
Stay and guide vanes guide the water to the runner blades. Stay vanes remain stationary at their position and reduces the swirling of water due to radial flow, as it enters the runner blades, thus, making the turbine more efficient.

Guide Vanes
Guide vanes are not stationary, they change their angle as per the requirement to control the angle of striking of water to turbine blades to increase the efficiency. They also regulate the flow rate of water into the runner blades thus controlling the power output of a turbine according to the load on the turbine.

Runner Blades
Runner blades are the heart of any Francis turbine. These are the centers where the fluid strikes and the tangential force of the impact causes the shaft of the turbine to rotate, producing torque. Close attention to the design of blade angles at inlet and outlet is necessary, as these are major parameters affecting power production.
The runner blades have two parts. The lower half is made in the shape of a small bucket to rotate the turbine by using the impulse action of water. While the upper part of the blades uses the reaction force of water flowing through it. The runner rotates through these two forces.

Draft Tube
The pressure at the exit of the runner of the reaction turbine is generally less than atmospheric pressure. The water at the exit, cannot be directly discharged to the tailrace. A tube or pipe of the gradually increasing area is used for discharging water from the exit of the turbine to the tailrace.
This tube of the increasing area is called Draft Tube. One end of the tube is connected to the outlet of the runner. However, the other end is submerged below the level of water in the tail-race.