Straight League On Grid 1000 Francis Turbine Generator

High Efficiency Low Noise Francis Water Turbine Electric Generator On Grid

Francis turbines may be designed for a wide range of heads and flows. This, along with their high efficiency, has made them the most widely used turbine in the world. In contrast to the Pelton turbine, the Francis turbine operates at its best completely filled with water at all times. The turbine and the outlet channel may be placed lower than the lake or sea level outside, breducing the tendency for cavitation.

Francis turbine includes volute, seat ring, water guide mechanism, top cover, runner, main shaft, guide bearing, bottom ring, draft tube, etc. The volute is a water diversion component, which is shaped like a snail shell, and is generally made of metal material and has a circular cross section. The seat ring is placed between the volute and the guide vane, and is composed of an upper ring, a lower ring and a number of upright posts, which are directly connected to the volute; the upright post is wing-shaped and cannot be rotated, and is also called a fixed guide vane.

The water guide mechanism is composed of movable guide vane, speed control ring, boom, connecting rod and other components. The runner is directly connected to the main shaft and is the rotating part of this type of turbine. The runner is composed of an upper crown, a lower ring, a drain cone and a number of fixed blades. Its shape and the matching dimensions of each component are different according to the water head used. It's different. The draft tube is a water turbine drain component that directs the water flow from the runner outlet to the downstream

Francis Turbine Components

1. Spiral Casing
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 mean the water striking the turbines blades should flow in the circular axis for efficient striking. So the spiral casing is used, but due to circular movement of the water, it looses its pressure.

2. Stay Vanes
Stay vanes and guide vanes guides 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 turbine more efficient.

3. 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.

4. Runner Blades
The performance and efficiency of the turbine is dependent on the design of the runner blades. In a Francis turbine, runner blades are divided into 2 parts. The lower half is made in the shape of small bucket so that it uses the impulse action of water to rotate the turbine.

The upper part of the blades use the reaction force of water flowing through it. These two forces together makes the runner to rotate.

5. Draft Tube
The pressure at the exit of the runner of Reaction Turbine is generally less than atmospheric pressure. The water at exit cannot be directly discharged to the tail race. A tube or pipe of gradually increasing area is used for discharging water from the exit of turbine to the tail race.

This tube of increasing area is called Draft Tube. One end of the tube is connected to the outlet of runner while the other end is sub-merged below the level of water in the tail-race.

Francis Water Turbine Electric Generator On Grid Technical Parameter