Constant Volume & Constant Pressure Gas Turbine

Today I am going to discuss Constant volume & constant pressure gas turbines.

If you are looking to know about this gas turbine, then stay with me and let me take you on the knowledgeable journey of this gas turbine.

So, welcome to Engineers Rail, come with me while I start the engine of this knowledgeable journey.

So, without taking too much of your time, Let’s dive into the mainstream of this session.

First, Let’s start with some basics, What do you say?

What is Gas Turbine?

A gas turbine is a combustion engine that can convert natural gas or other liquid fuels to mechanical energy. This energy then drives fuels to mechanical energy. The gas turbine is used to produce an electric current.

Gas turbines which mainly used in automobile engines. Gas turbines are also used in aircraft as of now.

You can check out the classification of turbines to know more about various turbines. 

After knowing the basics of gas turbine, Let’s move to the Constant volume gas turbine first.

gas turbine

Constant Volume Gas Turbine-

The working of the gas turbine at the constant volume is known as the constant gas turbine and the constant volume gas turbine works on an open cycle.

Now, Let’s see the construction of a constant volume gas turbine.

Construction of Constant volume Gas Turbine-

 Parts of constant volume gas turbine

  • Generator
  • Motor
  • Turbine
  • Compressor
  • Inlet valve for air
  • Outlet valve for gas
  • Spark plug
  • Fuel pump nozzle
  • Connecting pipes

Firstly, the Motor is connected to the generator, turbine and compressor to give them initial torque to initially rotate these components. Then, the Inlet valve is situated at the top to draw atmospheric air to the compressor.

The spark plug is used to fire the compressed gases and fuel coming from the compressor and fuel pump nozzle itself. Here outlet valve sucks the high-pressure gas and throws it directly into the turbine to further rotate the turbine wheel.

This was the short and sweet construction of this turbine. Now, Let’s move to the working of the same.

Working of Constant volume Gas Turbine-

When atmospheric air will enter in the compressor, here compressor will increase the temperature and pressure of the air and it goes to the inlet valve to enter the combustion chamber.

Otherside, the fuel pump nozzle will supply the fuel. When compressed air and fuel mix with each other, then spark plug sparks inside the combustion chamber to fire up the fuel-air mixer.

then generated gas born from the air-fuel mixer, goes to the turbine itself via connecting pipes from combustion chamber to turbine.

The used gas coming from the turbine will throw out through the chimney into the atmosphere.

Again, the generator is connected to the turbine which will rotate the generator shaft and further generate electricity.

This is how this turbine works.

Constant Pressure Gas Turbine-

The working of the gas turbine at the constant pressure is known as the constant pressure gas turbine and the constant pressure gas turbine works on an open cycle.

Now, Let’s see the construction of a constant pressure gas turbine.

Construction of Constant volume Gas Turbine-

 Parts of constant pressure gas turbine

  • Starting motor
  • Compressor
  • Air inlet valve
  • Fuel inlet
  • Combustion chamber
  • Burner
  • Turbine
  • Generator
  • Exhaust gas outlet

Construction of this turbine is just the same as constant volume gas turbine. Here burner is used instead of the spark plug to fire the air-fuel mixer in the combustion chamber and used or the exhaust gas will go out from the exhaust gas outlet.

Now, Let’s see the working of this turbine.

Working of Constant pressure Gas Turbine-

Once the starting motor starts to give initial torque to the compressor and further to the turbine, both connect through the connecting shaft.

As the compressor rotates, it sucks the air from the atmosphere and then it compresses the air to increase the temperature and pressure of the air.

Further, Compressed air will transfer to the combustion chamber. Here fuel is injected through the fuel inlet valve and compressed air and fuel will be mixed together inside the combustion chamber, making the air-fuel mixer ready to burn.

Then, burner lite-up and fire the combustion chamber, firing the air-fuel mixer.

Further, Due to the combustion of the air-fuel mixer, a huge amount of gas produces and this constant high-pressure gas is directed to the turbine and thus the turbine will rotate and further turbine rotates the generator to produce electricity.

This is how this turbine works.


Basically, a Constant volume gas turbine and a Constant pressure gas turbine are the same in working but volume and pressure are constant in both of the turbines respectively. As I mentioned above in detail.

That’s it for now. I hope you grasped the knowledge shared and further added some value to you.

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Before you go, Here are some MCQ of the turbine, you should never miss-


In a gas turbine cycle, the turbine output is 600kJ/kg, the compressor work is 400kJ/kg and the heta supplied is 1000kJ/kg. The thermal efficiency of this cycle is-
A. 80%
B. 60%
C. 40%
D. 20%

Answer- D. 20%

Brayton cycle is reversed-
A. Carnot cycle
B. Rankine cycle
C. Joule cycle
D. Dual cycle

Answer- D. Dual cycle

The compressors used in gas turbines are typical of which type-
A. Centrifugal
B. Centripetal
C. Reciprocating
D. Axial

Answer- D. Axial

The constant pressure gas turbine works on the-
A. Rankie cycle
B. Bell Coleman cycle
C. Carnot cycle
D. Brayton cycle

Answer- D. Brayton cycle

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