The main difference between impulse and reaction turbine is that in the impulse turbine the pressure of working fluid is completely converted into kinetic energy before it hits the turbine blades while in the case of reaction turbine the pressure is gradually converted into kinetic energy in multiple numbers of stages.
The purpose of the turbine is to convert fluid energy into mechanical work. This turbine is generally classified into impulse and reaction turbines.
It is also classified on the basis of type of fluid example:- Steam and water. In this article, we have provided separate differences for hydraulic and steam turbine
1) Steam turbine:
In a steam turbine, the working fluid is steam. The pressure of steam is converted into the mechanical work of the shaft.
This turbine is classified as:
A) Impulse turbine:-
In an impulse turbine the total pressure energy of the fluid is completely converted into kinetic energy before it strikes rotor blades.
The impulse turbine is based on the principle of impulse. The speed of this turbine is faster hence compounding is required in this type of turbine to regulate speed.
Examples:- DA-Laval turbine.
B) Reaction turbine:-
The flow of steam glides onto the rotor blades and the reaction force generated drives the rotor blades. In a reaction turbine, the pressure gradually decreases in multiple stages. The speed of this turbine is less hence it doesn’t require compounding.
Example:- Parson’s turbine.
2) Hydraulic turbine:
In this type of turbine, the working fluid is water. The water at a higher head is used to rotate the shaft of the turbine.
It is generally used for power generation in power plants. It requires a large volume of water at a higher head.
The turbine is classified as,
A) Impulse:-
In this type of turbine, the jet of water impinges on the turbine bucket to rotate the rotor. So the water enters in the tangential direction.
It requires less discharge of water at the higher head. The turbine works at atmospheric pressure. The casing is generally used for the enclosure. it doesn’t have any hydraulic function.
Eg. Pelton wheel turbine.
B) Reaction:-
In a reaction turbine, the flow of water is guided by guide vanes which rotate the turbine. This type of turbine requires a higher flow rate of water and the casing completely filled with water while running.
The casing performs a major role in this type of turbine as it guides the flow of water. The turbine works at higher pressure.
Examples:- Francis, Kaplan.
Difference between impulse and reaction turbine (Steam turbine):
| Sr. No. | Impulse | Reaction |
|---|---|---|
| 1 | In this type of turbine, all the pressure energy is converted into kinetic energy before passing through the rotor blade. | In this turbine, the Pressure energy is gradually converted into kinetic energy in a number of stages. |
| 2 | The steam strike on a blade surface. | The steam glides over the surface of the blade. |
| 3 | The rotor blades experience only kinetic energy. | The rotor blades experience Kinetic as well as pressure energy. |
| 4 | In a turbine expansion of steam takes place through the nozzle. | In a reaction turbine, the stationary blades act as like a nozzle. |
| 5 | The passage area between rotor blades remains constant throughout the blade. | The passage area between rotor blades increases from start to end of the blade. |
| 6 | The pressure of steam while passing through rotor blades remains constant. | In this type of turbine pressure gradually decreases while passing through rotor blades. |
| 7 | This turbine runs at a higher speed. | The speed of the reaction turbine is less in comparison to the impulse turbine. |
| 8 | The relative velocity of steam remains the same while passing through the rotor blades. | The relative velocity of steam increases while passing through rotor blades. |
| 9 | This turbine is smaller in size as total pressure is suddenly decreased at the first stage. | The reaction turbine is larger in size as the pressure is gradually decreased in multiple stages. |
| 10 | The compounding is required in this turbine to reduce uncontrolled speed. | The reaction turbine doesn’t require compounding. |
| 11 | The overall efficiency of this turbine is low. | The overall efficiency of the reaction turbine is higher. |
| 12 | The maintenance cost is less. | The maintenance cost for this turbine is more. |
| 13 | The turbine has a few stages. | It requires more number of stages. |
| 14 | The manufacturing of blades is easier. | It is difficult to manufacture the aerofoil shape of the blade. |
| 15 | It is used in ships and refineries. | It is generally used in high-capacity power plants. |
| 16 | Example:- DA-Laval turbine. | Example:- Parson’s Turbine. |
Impulse and Reaction turbine (Hydraulic turbine):
| Sr. No. | Impulse | Reaction |
|---|---|---|
| 1 | The turbine works on the principle of impulse. | This type of turbine works on the principle of reaction. |
| 2 | The jet of water strikes on the bucket. | In this turbine flow of water is guided through guide blades. |
| 3 | The water flows in the tangential direction. | In this type of turbine, water flows in the radial or axial directions. |
| 4 | The turbine is operated at a high head about 150 m to 2000 m. | This type of turbine is operated at a low head about 30 m to 500 m. |
| 5 | It works at atmospheric pressure. | This type of turbine works at higher pressure. |
| 6 | The turbine is installed above the tailrace. | This type of turbine is installed below the tailrace. |
| 7 | The degree of reaction is zero. | The degree of reaction is from 0 to 1. |
| 8 | The draft tube is not required. | The draft tube is necessary. |
| 9 | The casing has no hydraulic function. | The casing is necessary because it works at a higher pressure and guides the flow of water. |
| 10 | The flow is controlled by a needle valve. | The flow is controlled by guide vanes. |
| 11 | Water is not field throughout the turbine. | Water is completely filled in the casing of the turbine. |
| 12 | It is not necessary to fill the casing completely. | It is necessary that the casing should run full. |
| 13 | It requires less discharge of water. | In this case, the water discharge is higher. |
| 14 | The turbine has more hydraulic efficiency. | The hydraulic efficiency is less. |
| 15 | Example:- Pelton wheel turbine. | Example:- Francis, Kaplan. |
