Classification of Hydraulic Turbine: Definition, Classification With Example

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This blog post is going to elaborate on- Classification of Hydraulic Turbines with its definition and types in a detailed manner with examples.

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Classification of Hydraulic Turbine

What is Hydraulic Turbine?

The conversation of fluid pressure energy or kinetic energy of fluid into the mechanical energy is done via a turbine, Known as a Hydraulic Turbine.

A French engineer Benoit Fourneyron was the inventor of the first hydraulic turbine in 1830.

Further, Hydraulic turbines were developed and improved by various engineers around the globe to improve their efficiency and working.

Conversion of hydraulic energy

Now, Let’s move to the next session where we will classify hydraulic turbines with examples.

Classification of hydraulic Turbine-

There are various types of turbines based on specific categories and they are-

  1. According to the types of energy at the inlet
  2. According to the direction of the flow of water on the runner
  3. According to the Head Available
  4. According to the specific speed of the turbine

1. According to the types of energy at the Inlet-.

  1. Impulse Turbine
  2. Reaction Turbine

I. Impulse Turbine-

Impulse turbines work with the help of fluid kinetic energy and here nozzle is used to extract kinetic energy from fluid or you can say water, known as an impulse turbine.

In an Impulse turbine, A fixed nozzle is installed to strike the water at the turbine bucket-shaped blade with a high velocity which further rotates the turbine wheel and hence generates electricity.

An example of impulse is- Pelton Wheel Turbine.

II. Reaction Turbine-

This turbine uses kinetic energy as well as pressure energy of the fluid(Or water) to rotate the bucket of the wheel, known as a reaction turbine.

This turbine works based on Newton’s third law where two movable nozzles are installed which rotate along its axis using the third law of motion and further rotate the runner blade and hence generate electricity.

Examples of reaction turbines are- Francis Turbine and Kaplan Turbine.

2. According to the direction of the flow of water on the runner-

  1. Tangential Flow turbine
  2. Radial flow turbine
  3. Axial Flow Turbine
  4. Mixed Flow

I. Tangential Flow Turbine-

When water strikes from the nozzle straight at the single point of the runner’s blade tangentially every time, known as a tangential flow turbine.

Consider runner is a circle and water flowing from the nozzle is a line. Here, you know that when a line touches the circle, that line is known as a tangential line.

The same thing happens here as the flow of water strikes tangentially at the runner blade and is called a tangential flow turbine.

Examples of Tangential Flow turbines is- Pelton Turbine and Turgo Turbine.

II. Radial flow turbine-

The flow of water enters into the runner in a radial direction or striking of the water happens at the radius of the runner, known as radial flow turbine.

In these turbines, water enters from the penstock usually and the flow of water is further guided by guide vanes into the center of the runner and this phenomenon further rotates the runner’s blades and hence generates electricity.

Example of Radial Flow turbine is- the Old Francis turbine and fourneyrone Turbine.

III. Axial flow turbine-

The direction of flow of the water is axial or just parallel to the axis of rotation or shaft, known as an axial flow turbine.

Water enters from the spiral cashing and further reaches to guide vanes, these guide vanes further direct the water to the runner’s blade and thus rotate the turbine.

Water enters axially in this turbine that’s why these types of turbines are called axial flow turbines.

Example of Axial Flow turbine is- the Kaplan turbine, Propeller Turbine, and Bulb Turbine.

IV. Mixed Flow Turbine-

The initial striking of water at the runner’s blade comes from the radial direction and water leaves in the axial direction, known as a mixed flow turbine.

Here, the Nozzle strikes the runner’s blade with high velocity, and this cause to rotate the runner and connected shaft, while water leaves the axial from the draught tube just beneath the turbine.

An example of a Mixed Flow turbine is- Modern Francis Turbine.

3. According to the Head Available-

  1. High Head Turbines
  2. Medium Head Turbines
  3. Low Head Turbines

I. High Head Turbine-

High-head turbines are those whose reservoirs have 250 meters and above of height from the turbine.

Low Head range- 250 Meters and above.

An example of the High head turbine is- Pelton Turbine.

II. Medium Head Turbine-

Medium-head turbines are those whose reservoirs have 60 to 250 meters of height from the turbine.

Medium Head range- 60-250 Meter

An example of the medium-head turbine is- Francis Turbine.

III. Low Head Turbine-

Low-head turbines are those whose reservoirs have 10 to 60 meters or below 60 meters of height from the turbine.

Low Head range- 10-60 Meters or below 60 meters

Example of the low head turbine is- Kaplan Turbine and propeller turbine.

4. According to the specific speed of the turbine-

Here is the classification of turbines based on specific speed

  1. Low-specific speed turbine
  2. Medium-specific speed turbine
  3. High-specific speed turbine

Specific Speed of Turbine– As you may know that generating one kilowatt of power in one meter of head available can be known as the specific speed of the turbine and it is denoted by Ns.

Now, Let’s get back into the mainstream-

I. Low specific speed turbine-

A turbine is having less than 60 specific speeds, known as a low specific speed.

In general, If a turbine is producing less than 60 kilowatts in less than 60-meter head available, then this turbine will count under the low specific speed turbine.

An example of the low specific speed turbine is- the Pelton wheel turbine.

II. Medium-specific speed turbine-

A turbine has having 60 to 400 specific speed, known as a medium specific speed.

In general, If a turbine is producing 60 to 400 kilowatts in 60 to 400-meter heads available, then this turbine will count under the medium-specific speed turbine.

An example of a medium-specific speed turbine is- the Francis turbine.

III. High-specific speed turbine-

A turbine is having above the 400 specific speed, which is known as a high specific speed.

In general, If a turbine is producing above 400 kilowatts in above 400-meter head available, then this turbine will count under the high specific speed turbine.

Example of medium-specific speed turbine is- Kaplan and propeller turbine.


Wrapping Up- 

This is all for the classification of hydraulic turbines for now. If something missing, don’t forget to mention it in the comment section below and I will try to add those.

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Here are some suggested articles, you should not miss-

Classification of Turbines

Constant Volume & Constant Pressure Gas Turbine

Difference Between Impulse and Reaction Turbine



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