Difference Between Impulse and Reaction Turbine

Are you looking to know about the Differences between Impulse and Reaction turbines?

Then you came to the right place, Here you learn working principles and comparisons between both of the turbines in a simple and digestible manner.

Surprisingly, you can download this whole article as a pdf and ppt at the end, So don’t forget to take it away with you.

So, let’s get started the journey of difference between impulse and reaction turbine with examples.

Firstly, I will start with the impulse turbine, so here I go…

Working Principle of Impulse turbine-

The impulse turbine works on the principle of Newton’s second law, the resulting motive force is due to the change in momentum that gives rotation to the turbine shaft.


In general, When high-velocity fluid is thrown on the rotor moving blade via a fixed nozzle, due to impulse force rotor start to rotate depending on the mass and velocity of the fluid.

impulse turbine

Construction of Impulse Turbine-

Water is stored at the height and passes through a nozzle situated at almost ground level to provide high-velocity transmission of fluid.

When fluid strikes the bucket connected to the runner, it forces the runner to rotate at its own axis by converting the high-speed jet energy into rotational energy to produce electricity through the generator.

Here are some main components used in the Impulse turbine-

Spear– To regulate the flow of water according to turbine loads, the spear is moved in and out inside the nozzle.

NozzleTo pressurize the flow of fluid and provide a suitable angle of strike, the fixed nozzle is used in the impulse turbine and it is one of the essential components of this turbine which is usually made of tungsten carbide.

Generally, multiple nozzles are used to ensure maximum efficiency because to obtain maximum efficiency, the flow of fluid should be twice as high as the rotating runner shaft.

Bucket– A bucket is installed at the runner shaft, providing a bucket-shaped blade facing the nozzle to absorb the maximum amount of high-energy fluid coming from the nozzle, as you would have seen in the diagram above.

Penstock– Penstock is basically used to drive water from a reservoir or dam in high-speed flow to the turbine and it is usually made of steel.

Casing– Casing is the outer shield of the turbine and it is used to control the water flow and give it direction to go out from the turbine and also to protect the equipment inside the turbine.

RunnerRunner is used to mount the bucket and it is attached to the shaft which further converts water energy into mechanical energy.

TailraceThe tailrace is the place where used water is exited from there.

This was the construction and working of an impulse turbine. Now, I am going to head toward the types or impulse turbine example.

Types of Impulse turbine

Here are some types or examples of the Impulse turbine according to head load in descending order-

  • Pelton
  • Turgo
  • Crossflow
  • Multi-jet Pelton
  • Undershot waterwheel

To know about more of these turbines, Recommend going to Classification of turbines.

Application of Impulse Turbine

Here are some applications of the impulse steam turbine

  • Reverse osmosis plant
  • Supply drinking water
  • Electric power generation

Now, let’s move on to the reaction turbine and further you will learn a comparison between these two turbines. So, here we go…

Working Principle of Reaction turbine-

60% of the hydro-power plants are used to efficiently generate electricity through reaction turbines all around the globe. A reaction turbine is a type of turbine that develops torque by reacting to the pressure or weight of the fluid.

Here, the reaction turbine works on the principle of Newton’s third law of motion, which states that action will be equal and opposite to reaction, in general.

Reaction turbines are those which operate under hydraulic pressure energy and part of kinetic energy.

In this case, the water reacts with the vanes as it moves through the vanes and transfers its pressure energy to the vanes moving, in turn, rotating the runner on which they are mounted.

Firstly, water enters from the penstock and goes to the movable guide vanes and then moves to the fixed guide vanes, which creates the pressure difference in water due to these sets of blades, which is further called reaction force and this force is caused to rotate the runner blades and further turbine.

reaction turbine

Construction of Reaction turbine-

There are many components used in a reaction turbine but the main components of this turbine are-

  • Spiral Casing
  • Guide mechanism
  • Runner
  • Draft tube
  • Penstock

Spiral casingThe casing is made with uniformly decreasing cross-sectional area along the circumference and here due to decreasing cross-sectional area provides the uniform velocity to the water, when water strikes the runner blades and thus this design of casing provides the uniform momentum and uniform velocity to the water to further strike the runner blades.

The material used to manufacture spiral casing is- Concrete and steel.

Guide mechanism– To provide the direction to the water, a guide mechanism is used, where the Guide mechanism is actually installed inside the spiral casing.

Here, the modern turbines come with adjustable guide vanes where the rate of water flow can be adjusted by varying the angle of the guide vanes, according to the turbine’s load.

Runner– Runner blades use water’s pressure energy to run the turbine and this runner counts as an important component of the reaction turbine.

Here, in modern turbines, the runner blades can vary the pressure force acting on them according to the turbine’s loads and available pressure.

Draft tube– It generally connects the runner’s exit to the tail race which has a uniformly increasing cross-section area which further helps to recover the pressure of water.

Penstock– Penstock is usually used to drive water from the water reservoir or dam directly into the turbine.

This was the construction and working of the reaction turbine, now let’s discuss the example of this turbine.

Examples of Reaction turbine-

There are two examples of this turbine-

You can further read about these turbines in the Classification of turbine

Application of Reaction Turbine

Here are some applications of this turbine-

  • Used in wind power mills to generate electricity.
  • Mostly used in hydropower plants to generate electricity.
  • The only turbine which gives maximum power out from a low available water head & high velocity.

After sharing most of the information about these impulse and reaction turbines, let’s head on to our last headline of this session, So, here we go…

Difference between Impulse and Reaction turbine-

Here are 10 major impulse and reaction turbine differences

Impulse TurbineReaction Turbine
An example of an impulse turbine is the Pelton turbineAn example of a reaction turbine is the Francis and Kaplan turbine
The energy at the inlet to the moving blade is only kinetic energy.The energy at the inlet to moving blades is kinetic energy and pressure energy.
The entire fluid energy of the water is first converted into kinetic energy in the nozzle.The available energy of the water is partly converted into kinetic energy in the fixed blades.
The pressure of the flowing water remains constant and equal to atmospheric pressure.The pressure and velocity both are changes while passing through the runner.
Water flows through the nozzle and strikes the moving blades mounted on the wheel.The water first enters the fixed blades and then the runner.
Water may be admitted over a part of the circumference.Water must be admitted over the whole circumference of the wheel.
It is not required that the wheel should run inside the water.It is required that the wheel should be always inside the water.
It is possible to regulate the flow without loss.It is not possible to regulate the flow without loss.
Governing by needle valve fitted into the nozzle.By the guide mechanism assembly.
The highest efficiency is 80%.The highest efficiency is 95%.


That’s it for now for comparison between impulse and reaction turbine, Hopefully, you got the information regarding the Difference between impulse and reaction turbine and its various aspects, which are possibly discussed above.

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