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 a generator that produces electrical energy.

Gas turbine applications


Main three Industrial applications are:

  • Electric power generation

  • Natural Gas plant

  • Gas booster, pipeline and re-injection

 

The use of gas turbines for generating electricity dates back to 1939. Today, gas turbines are one of the most widely-used power generating technologies. Gas turbines are a type of internal combustion (IC) engine in which burning of an air-fuel mixture produces hot gases that spin a turbine to produce power.

Working principle
 

A simple gas turbine is comprised of three main sections a compressor, a combustor, and a power turbine. The gas-turbine operates on the principle of the Brayton cycle, where compressed air is mixed with fuel, and burned under constant pressure conditions.

The blades spin at high speed and compress or squeeze the air. The compressed air is then sprayed with fuel and an electric spark lights the mixture. The burning gases expand and blast out through the nozzle, at the back of the engine. As the jets of gas shoot backward, the engine and the aircraft are thrust forward

An aeroderivative gas turbine
The aeroderivative gas turbine is a lighter weight variation of a gas turbine. Despite being classified as a gas turbine, the fuel source for the aeroderivative turbine is not really gas. Actually, they are designed so that fuel and air are mixed and then ignited to achieve the desired output.

Fuel
One further advantage of gas turbines is their fuel flexibility. They can be adapted to use almost any flammable gas or light distillate petroleum products such as gasoline (petrol), diesel and kerosene (paraffin) which happen to be available locally, though natural gas is the most commonly used fuel.

Main components
The gas turbine is made up of the following components:
An air compressor.
A combustor.
A power turbine, which produces the power to drive the air compressor and the output shaft.

 

Efficient
Each has a combined-cycle output of 500 MW, 59.1% efficiency (simple cycle, 39.5%), a 1500°C turbine inlet temperature, an exhaust temperature of 587°C. ... It is a 1-on-1 combined-cycle arrangement. According to Koeneke, it has reached 59.2% efficiency

An Open cycle
In gas-turbine engine: Idealized simple open-cycle gas-turbine engine. Most gas turbines operate on an open cycle in which air is taken from the atmosphere, compressed in a centrifugal or axial-flow compressor, and then fed into a combustion chamber.

 

Closed cycle
A closed-cycle gas turbine is a turbine that uses a gas (e.g. air, nitrogen, helium, argon, etc.) for the working fluid as part of a closed thermodynamic system. Heat is supplied from an external source. Such recirculating turbines follow the Brayton cycle.

Types
There are 3 main types of impulse turbine in use: the Pelton, the Turgo, and the Crossflow turbine.
The two main types of reaction turbine are the propeller turbine (with Kaplan variant) and the Francis turbine.
The reverse Archimedes Screw and the overshot waterwheel are both gravity turbines.

Impulse turbine
Impulse turbines change the direction of flow of a high velocity fluid or gas jet. Reaction turbines develop torque by reacting to the gas or fluid's pressure or mass. The pressure of the gas or fluid changes as it passes through the turbine rotor blades.