# Gas Turbine:
A gas turbine, also called a combustion turbine, is a type of internal combustion engine. It has an upstream rotating compressor coupled to a downstream turbine, and a combustion chamber in-between.
The basic operation of the gas turbine is similar to the of the steam power plant except that air is used instead of water. Fresh atmospheric air flows through a compressor that brings it to higher pressure. Energy is then added by spraying fuel into the air and igniting it so the combustion generates a high-temperature flow. This high-temperature, high-pressure gas enters a turbine, where it expands down to the exhaust pressure, producing a shaft work output in the process. The turbine shaft work is used to drive the compressor and other devices such as an electric generator that may be coupled to the shaft. The energy that is not used for shaft work comes out in the exhaust gases, so these have either a high temperature or a high velocity. The purpose of the gas turbine determines the design so that the most desirable energy form is maximized.
Operation
Gases passing through an ideal gas turbine undergo three thermodynamic processes. These are,
Isentropic compression,
Isobaric (constant pressure) combustion and
Isentropic expansion.
Together, these make up the Brayton cycle.
In a practical gas turbine, gases are first accelerated in either a centrifugal or axial compressor. These gases are then slowed using a diverging nozzle known as a diffuser; these processes increase the pressure and temperature of the flow. In an ideal system, this is isentropic. Gases then pass from the diffuser to a combustion chamber, or similar device, where heat is added. In an ideal system, this occurs at constant pressure (isobaric heat addition). As there is no change in pressure the specific volume of the gases increases. Finally, this larger volume of gases is expanded and accelerated by nozzle guide vanes before energy is extracted by a turbine. In an ideal system, these gases are expanded isentropically and leave the turbine at their original pressure.
Gases passing through an ideal gas turbine undergo three thermodynamic processes. These are,
Isentropic compression,
Isobaric (constant pressure) combustion and
Isentropic expansion.
Together, these make up the Brayton cycle.
In a practical gas turbine, gases are first accelerated in either a centrifugal or axial compressor. These gases are then slowed using a diverging nozzle known as a diffuser; these processes increase the pressure and temperature of the flow. In an ideal system, this is isentropic. Gases then pass from the diffuser to a combustion chamber, or similar device, where heat is added. In an ideal system, this occurs at constant pressure (isobaric heat addition). As there is no change in pressure the specific volume of the gases increases. Finally, this larger volume of gases is expanded and accelerated by nozzle guide vanes before energy is extracted by a turbine. In an ideal system, these gases are expanded isentropically and leave the turbine at their original pressure.
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Table of Contents:
- What Is Gas Turbine?
- Operating Principles of Gas Turbine Engine
- Thermodynamic Processes of Gas Turbine Engine
- Types of Gas Turbines Based On Structure and Function
Turbo Jet Engine
Turbo Fan Engine
Single-Shaft Gas Turbine Engine
Double-Shaft Gas Turbine Engine - Advantages of Gas Turbine Engine
- Disadvantages of Gas Turbine Engine