The gas turbine can be classified as follows:
1) According to types of combustion process
I. Constant volume or explosion type gas turbine
II. Constant pressure or continuous combustion type gas turbine
2) According to direction of flow
I. Axial flow gas turbine
II. Radial flow gas turbine.
3) According to action of expanding gases
I. Impulse gas turbine
II. Impulse- Reaction gas turbine
4) According to path of working substance
I. Open cycle gas turbine plants: In the open cycle gas turbine, ambient air enters at the compressor and after the compression of air, fuel is burned in the air itself to raise it to a high temperature and then product of combustion is passed on to the turbine for expansion and which after delivering the work are finally ejected to atmosphere. In the open cycle the working medium is continuously replaced by fresh air and fuel.
II. Closed cycle gas turbine plants: In the closed cycle gas turbine power plant, the same air or the working fluid is circulated over and over again. The working medium is not mixed with fuel, but it is heated by the burning of fuel in separate supply of air in the combustion chamber and transferring this heat to the working fluid which passes through tubes fitted in the combustion chamber. The working fluid does not come into direct constant with product of combustion.
III. Semi-closed cycle gas turbine plants: Semi-closed cycle gas turbine plant is combination of open and closed cycle, in which some part of working fluid is recirculated to the plant and another part of working fluid flows into and from the atmospheric air.
5) According to thermodynamic cycle
I. Simple cycle
II. Simple cycle with intercooling: in which the air is cooled between stages of compression.
III. Simple cycle with regeneration: in which the air after compression is heated with help of exhaust gases coming from turbine.
IV. Simple cycle with reheating: in which combustion products (gases) after part of expansion in high pressure turbine is reheated in second combustion chamber and then it is expanded in the low pressure turbine.
V. Simple cycle with intercooling, regeneration and reheating.
6) According to shaft configuration
I. Single shaft engine: - Examples: Turbojet engine, Turboshaft engine.
II. Multi-shaft engine: - Example: Two shaft engine with power turbine, Turbojet engine, industrial slit shaft engine, Twin-spool engine.
7) According to applications
I. Power or industrial gas turbines
II. Aviation or aircraft turbines