Kaplan turbines are a kind of propeller hydro turbine often seen in hydroelectric power facilities. The water flows axially into and out of the turbine in this design. This turbine is most efficient when operating with a large quantity of water and a small vertical distance. The Kaplan turbine differs from other types of turbines in that its blades may move to various positions depending on the available water. This is a response turbine because the water loses pressure as it runs through it. The Kaplan turbine, invented by Austrian scientist Viktor Kaplan in 1913, combines propeller blades with wicket gates that could be automatically changed to maximise efficiency over a broad range of flow and water levels.
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Kaplan turbine: Design
It is crucial that these turbines be built to withstand high water pressure. Kaplan turbines are built significantly differently than standard turbines. This turbine has fewer moving parts. Water is introduced to the turbine by a radial flow path, and then suddenly turned axially by guiding vanes, which are stationary blades. There are a number of rotor blades on the turbine, all of which are fastened directly to the turbine’s central shaft. The angle of these blades may be adjusted thanks to the moveable joints, allowing for optimal performance at any given flow rate and water head. The blades of this turbine are not perfectly flat; instead, they twist ever-so-slightly because the outer section of the blade rotates at a faster rate than the inner part.
Kaplan turbine: Functioning theory
Kaplan turbine makes use of the concept of axial flow response in its operation. In axial flow turbines, the water flows through the runner at right angles to the runner’s axis of rotation. The water entering the turbine in a hydroelectric plant has the momentum and pressure to turn the blades efficiently. It’s a kind of turbine that gets its name from its rotating blades and has its roots in the Francis turbine. In contrast to the Francis turbine, it functions well even at low head and high flow rates.
Water in the penstock is the first step in the turbine’s operation. The pressure is then distributed uniformly when it enters the scroll casing. The guiding vanes then direct the water toward the runner blades. The pressure and flow rate needs may automatically modify these vanes. At this point, the water is redirected across a 90-degree angle, making it axial with respect to the runner blades. The shaft of the generator is turned by the spinning of the turbine to generate power. To keep the water being moved by the Kaplan turbine from becoming too similar to the water being moved by other turbines, this is done.
Kaplan turbine: Construction
These turbines have a somewhat different design than conventional turbines. These turbines have a central shaft that is directly linked to the rotor blades. The major parts of a Kaplan turbine are the runner or impeller, hub, daft tube, runner blades, shaft, and guide blades.
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Runners Blades
This turbine, which resembles a propeller, relies heavily on its runner blades. Instead of having flat blades like conventional axial flow turbines, they are twisted so that water may flow from the input to the outlet.
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Hub
The shaft of this turbine stands upright, and its bottom end is widened to form a hub.
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Shaft
The blades’ rotation causes the runner to revolve, which in turn spins the shaft and, ultimately, the generator coil. Due to its high rotational speed (between 1800 and 3600 rpm), the turbine shaft has to be heat-resistant.
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Guide Vane
Guide Vane uses a very specific angular rotation, directing the flow of water.
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Runner
A turbine can’t function without its runner, also known as the impeller. It’s a revolving part that aids in the production of electrical power.
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Blade Steering Mechanism
An adjustable axis is located at the pivot point of the turbine blade. Due to the blade connection’s mobility, the attack angle at which water strikes the blade may be adjusted.
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Volute Casing / Scroll Casing
A whole turbine may have its cross-sectional area reduced by using a scroll casing. The water flows from the penstock into the volute casing, and then into the guiding vane region.
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Draft Tube
The available force at the runner’s departure is often lower than the force of the surrounding air. Because of this, the water near the exit cannot simply flow into the tailrace.
Kaplan turbine: Applications
- There is the widespread use of Kaplan turbines in the generation of power across the globe.
- They are superior to other turbine designs in terms of efficiency under low water heads and high flow rates.
Kaplan turbine: Advantages
- It folds up neatly and can be assembled in minutes.
- Kaplan turbines are very efficient compared to other types of hydraulic turbines.
- Inexpensive microturbines may be produced all around the globe with only two feet of head space, making them ideal for individual power generation.
- These turbines’ efficiency is often around 90% since they are custom-made for each location.
Kaplan turbine: Disadvantages
- One potential drawback of the Kaplan turbine is cavitation.
- The turbine shaft can only be oriented vertically inside the unit.
- This kind of turbine is intended for high flow rates and will not operate at lower flows.
FAQs
What is a Kaplan turbine used for?
Most of the time, Kaplan turbines are used to make electricity all over the world. When there is a low head and a high flow, these turbines are used.
How exactly does a Kaplan turbine work?
The axial flow reaction principle is how the Kaplan Turbine works. In axial flow turbines, water flows through the runner in the same direction as the runner's turning axis. In a hydropower plant, the water that flows into the turbine has the speed and pressure energy it needs to turn the blades.
