A gas turbine is a type of internal combustion engine whose working fluid is the air itself. The engine is used to extract chemical energy from fuel and is also used to convert the chemical energy into mechanical energy by the use of gaseous energy as the working fluid to drive the engine and propeller, this, in turn, propels the aircraft.
Gas Turbine Components
1. Inlet
The air should be kept flowing unrestricted from the duct and the inlet duct should also remain neat and clean in order to keep the engine healthy. It is suggested to provide clean and undisturbed airflow at the inlet which when supplied to the engine increases its efficiency and protects the engine from erosion, corrosion, or any damage. It is also suggested that the fairings should be installed within the engine air inlet duct and the inlet duct to make sure that the airflow losses are minimum with respect to all the conditions of the airflow.
2. Compressor
The compressor is the one which is responsible for providing the turbine with the required amount of air which is needed to make it work in an efficient manner. In addition to this, it is required to supply the air at a very high static pressure. The commonly known ratio of pressure at the back compressor to pressure at the front compressor is 9:5
3. Diffuser
The air exits through the guide vanes of the compressor where the components of airflow get converted into a straight-line flow. After this, the air enters into the diffuser section which is a divergent duct. The basic function of a diffuser is aerodynamic.
4. Combustor
Once the air passes through the diffuser, it enters into the combustion section which is known as a combustor. The combustion section has a task that controls the burning of fuel and air. The heat which is released must be in a manner that the air gets expanded and accelerated in order to provide a smooth and stable stream for a uniformly heated gas at all conditions of operation. It is mandatory to accomplish the task with a minimum pressure loss and maximum heat release.
5. Turbine
A turbine engine has a four-stage turbine which is used to convert the gaseous energy of the air fuel into mechanical energy to move the compressor with the help of a reduction gear or the propeller. The turbine has a function wherein the gaseous energy gets converted into mechanical energy by expanding the hot and high-pressure gases into lower temperatures and pressure.
6. Exhaust
Once the gas passes through the turbine, it gets discharged through the exhaust. Mostly the gaseous energy gets converted into mechanical energy with the help of a turbine, a sufficient amount of power remains in the exhaust gas. This remaining gas is accelerated through the convergent duct of the exhaust to make it more useful as the airplane drives.
Gas Turbine Working Principle
The basic principle on which the gas turbine works is identical to all the engines which are used to extract energy from the chemical fuel. The most commonly known 4 steps for any internal combustion engine are as follows:
- Air Intake.
- Air Compression.
- Combustion, where the fuel is injected and made to convert to the stored energy.
- Expansion and extinction, where the converted energy is brought to use.
In the case of a piston engine like the engines used in the cars or as the airplane engine, the steps which are involved in the intake, compression, combustion, and exhaust in the cylinder head but at the different times as the piston continuously moves up and down.
In the case of a turbine engine, the same four steps occur that too at the same time but at different places. Due to this fundamental difference, the turbine has various engine sections which are known as:
- Inlet section
- Compressor section
- Combustion section
- Turbine and exhaust section.
The turbine section of the engine is responsible for producing the usable shaft power as an output which is used to drive the propeller. Other than this it must be provided with the power to drive the compressor and the engine accessories. This is done by exposure to the high temperature, pressure, velocity gas which is converted from the gaseous energy to mechanical energy in the form of shaft power.
Gas Turbine Components and Principle
The mass of the air supplied must be very high which is supposed to be supplied to the turbine in order to produce the required power. The air which is supplied is done with the help of the compressor which extracts the air and takes it into the engine where it gets squeezed to provide high-pressure air to the turbine. The role of the compressor is to convert mechanical energy from the turbine to gaseous energy in the form of pressure or temperature.
In case the compressor and the turbine were 100% efficient then the compressor would have supplied all the air which is needed by the turbine and at the same time, the turbine would have supplied the necessary power to which is required to drive the compressor. In this case, only a perpetual motion machine would exist as frictional losses and the inefficiencies of the mechanical system do not allow a perpetual motion machine to function properly.
