Kaplan Turbine

By Mohit Uniyal|Updated : August 26th, 2022

The Kaplan Turbine is an adjustable-bladed axial reaction flow turbine. The axial flow turbine is defined as one in which the water flows parallel to the shaft's rotating axis. The turbine is known as a reaction turbine if the head of the inlet of the turbine is the sum of pressure energy and kinetic energy during the flow of water via a runner, and a portion of the pressure energy is converted into kinetic energy. The turbine shaft is vertical in an axial flow reaction turbine. The bottom end of the shaft is thickened, forming a hub or boss.

The hub functions as the axial flow reaction turbine's runner because the vanes are attached to it. The Francis turbine evolved into the Kaplan turbine. Its invention enabled efficient power generation in low-head applications, which the Francis turbine could not do. The Kaplan turbine is currently widely employed for high-flow, low-head power generation all over the world. Because the water flows in an axial direction, the Kaplan turbine is an axial flow reaction turbine.

What is the Kaplan Turbine?

In 1913, Austrian professor Viktor Kaplan developed the Kaplan turbine that combined automatically adjusted propeller blades with automatically adjusted wicket gates to achieve efficiency over a wide range of flow and water levels. A special type of propeller turbine is the Kaplan turbine, in which the runner blades may be adjusted during operation to respond to changes in load.

Kaplan Turbine Design

Kaplan Turbine Design

Axial flow runner consists of three to eight blades of the airfoil shape. Kaplan turbines are called double regulated because the flow rate is controlled in two ways: by turning the wicket gates and by adjusting the pitch on the runner blades. Kaplan turbines are particularly useful where enormous amounts of water flow can be employed even in dams with a low head due to their vast area. This is especially noteworthy because, before the development of the Kaplan turbine, most turbines were only suitable for huge water heads.

Working Principle of Kaplan Turbine

Kaplan Turbine operates on the axial flow reaction principle. Axial flow turbines have water that travels through the runner in a direction parallel to the runner's axis of rotation. In a hydropower plant, the water entering the turbine has the kinetic and pressure energy needed to effectively rotate the blades.

In order to attain efficiency over a wide range of flow and water levels, an Austrian scientist named Viktor Kaplan invented this turbine in 1913 by combining automatically adjustable wicket gates with automatically adjusted propeller blades. It originated from the Francis Turbine and is also known as a propeller turbine. It can operate at low head and high flow rates very effectively, which the Francis turbine cannot.

Kaplan Turbine Parts

Large amounts of water should be able to flow through these turbines without causing damage. Kaplan turbines are designed in a somewhat different way than other turbines. The Kaplan turbine is a lot smaller. A flow tube injects water in a radial direction, while functional guide vanes permanent blades direct the water abruptly into the turbine in an axial orientation. Let's have a look at the key parts of a Kaplan turbine, which are given below. A Kaplan Turbine is made up of the following components:

  • Scroll casing
  • Guide vanes/ wicket gates
  • Runner blades
  • Draft tube

Scroll Casing

It's a spiral-shaped casing with a smaller cross-section area. The major goal of the steady reduction in area is for the runner to see constant water velocity at each point of entrance. In a Kaplan turbine, the spiral casing and the guide blades are similar to those in a Francis turbine.

Guide Vanes/ Wicket Gates

It is the only controlling part of the whole turbine, which opens and closes the passage depending upon the demand of power requirement. If guide vanes are absent then the turbine can not work efficiently and its efficiency decreases.

Runner Blades

The runner blades are the heart of the Kaplan turbine components. The runner's blades can be adjusted to the best angle of attack for maximum power output. A governor servo mechanism adjusts the blades automatically as they rotate around pivots.

Draft Tube

Water is discharged from the turbine exit to the tail race through a tube or pipe with a gradually increasing area.

Advantages, Disadvantages, and Application of Kaplan Turbine

The Kaplan turbine is an axial flow water turbine with propellers. It features blades that can be adjusted. Adjustable blades are available for turbines and can help achieve high efficiency in a variety of heads. It's ideal for applications with low heads and strong flow. This is a Francis turbine that has been improved. Unlike the Francis turbine, which cannot work with a lower head, it is designed to operate with a lower head. The advantages, disadvantages, and applications of the Kaplan Turbine are as follows

Applications of Kaplan Turbine

  • Kaplan turbines are frequently employed to generate electricity all over the world.
  • When compared to other types of turbines, they can perform more efficiently at low water heads and high flow rates.

Advantages of Kaplan Turbine

  • It's compact and simple to put together.
  • When compared to other hydraulic turbines, the Kaplan turbine has very high efficiency.
  • At any load, the Kaplan turbine may operate at maximum efficiency.

Disadvantages of Kaplan Turbine

  • The Kaplan turbine's only downside is cavitation.
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FAQs on Kaplan Turbine

  • The Kaplan turbine is a reaction turbine with axial flow. As the working fluid passes across the turbine, it changes the pressure and generates energy. The hydrostatic head, as well as the kinetic energy of the water, are both recapitulated in power.

  • The Kaplan turbine has better efficiency than the Francis turbine. In comparison to the Francis turbine, the Kaplan turbine has a smaller cross-section and a lower rotating speed. Water flows axially in and axially out in a Kaplan turbine, but radially in and axially out in a Francis turbine.

  • The Propeller Turbine is another name for the Kaplan Turbine. It features blades that look like propellers. Instead of employing shaft power to axially displace the water and generate axial thrust, the axial force of water acts on the Kaplan Turbine blades and generates shaft power.

  • The Kaplan turbine can operate effectively at low head and high flow rates. Kaplan turbines operate on the axial flow reaction principle. In these turbines, water flows parallel to the runner's rotating axis within the runner.

  • The Kaplan turbine is an axial flow reaction turbine, which means that the water flows parallel to the shaft's axis of rotation. Both kinetic and potential energy are accessible at the inlet for Kaplan. The Kaplan turbine is also known as a variable pitch propeller turbine because its rotating blades may be adjusted.

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