What is a Kaplan Turbine?
Kaplan Turbine is generally a water turbine with propeller having some adjustable blades. It was invented and developed and by Viktor Kaplan, and so the name Kaplan Turbine is given to it. It also has the capability to automatically adjust the propeller blades to achieve high efficiency. It makes easy to achieve high efficiency. Certain water flows have certain position or angle of blades to achieve high efficiency and this automatically does that.
Kaplan Turbine is an advanced version of Francis turbine. Francis turbine never produced high efficiency at lower head levels. This Kaplan Turbine produced high efficiencies even with lower head levels. Kaplan Turbines can be used even when the head levels are too high and also too low. So Kaplan Turbines are being used throughout the world mostly in high flow and low head power production.
Usually, Kaplan Turbine is employed after a dam. A dam has a penstock and through which the water from penstock enter to the draft tube is the Kaplan Turbine. So now we can see the parts and operating of Kaplan Turbine. Water enters to the Kaplan Turbine from the penstock. It has a circular casing to provide the circular movement of flow of water in the turbine. It also has Guide vanes inside of the casing. The working of guide vanes is simple. The name itself represents that it helps to guide the water with the help of vanes. Vanes are nothing but wings of the fan. Wings of a fan guide the air to flow as the wings rotate. The same way, vanes in the Kaplan Turbine helps to move water into the hub. The hub has a runner which makes the turbine to power up. The flow of water towards the rotor is also in the radial direction in the beginning and then the velocity starts increasing. The best thing about the Kaplan Turbine is that the inlet vanes can be opened or closed which helps to regulate the amount of water flow into the turbine.
The turbine need not be at the lowest point of water as long as there is sufficient amount of water in the draft tube. Even when the turbine is located at higher altitudes, it increases the suction that is imparted on the turbine blades and the sudden pressure drop or eventual pressure drop can lead to cavitation. The efficiency of Kaplan Turbine usually ranges fro 70 to 90 percent but when at the times of low heads, the efficiency may still go down to 50.
Kaplan Turbines are used throughout the world for electrical power supply. Kaplan Turbines are especially suited for high flow conditions. It is good to know that micro turbines pricing at very low costs is manufactured for individual power supplies which can be installed at a level as low as 0.3 meters of head. The nasty thing about the Kaplan Turbines is that they are expensive to design and install but when once installed, they operate for over years and years.