Gas Turbine Cycle and Working Principle

Gas Turbine
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In this article, we will discuss one of the most important turbines that use gas to perform the required task efficiently: Gas Turbines! And we primarily concentrate on the gas turbine cycle so that you can better understand the gas turbine working principle and how it operates.
So, stay with us in this article and keep reading to learn everything there is to know about the gas turbine cycle and its components.

What is a gas turbine?

Gas turbines are considered a type of continuous internal combustion engine. This turbine uses rotary motion rather than reciprocating motion.

Components of a gas turbine.

There are three major design elements that are shared by all gas turbine engines. These components are the compressor, the combustion engine, and the power turbine. The downstream power turbine is connected to the compressor via the same shaft. Some turbines include a fourth element to improve efficiency, increase thrust-to-weight ratio, and convert power into other forms (mechanical or electric.)

Gas turbine control system

The gas turbine control system puts an emphasis on and safeguards the gas turbines. Superior performance for a power plant may be obtained with integrated control system solutions. It easily scales and adapts to changing demands in thermal and renewable energy generation, oil and gas, and safety applications. IS220UCSAH1A, IS220PPDAH1A, are some examples of GE control system parts.

Gas Turbine Working Principle

Gas turbine’s basic operation is based on the gas turbine cycle, also known as the Brayton cycle. The gas turbine cycle works as follows:

Though this cycle is not ideal for open-circle gas turbines, it is still used for them with minor modifications. They are ideal for use in a closed-cycle gas turbine. This cycle consists of four steps:

  • Isentropic compression in the compressor
  • pressure heat-addition in the combustion chamber of the combustor
  • Isentropic expansion in the power turbine
  • pressure heat rejection

The gas turbine’s compressor has been designed in such a way that it receives flowing atmospheric air, increasing pressure. This process compresses the air up to 30 times more than the ambient pressure. Fuel will be sprayed into the air as it passes through this element. Then, by igniting this fuel with air, energy is added, and the combustion produces a high-temperature flow.

The gas turbine cycle employs either silo, annular, or can-annular combustion. The annular combustors’ combustion chambers are doughnut-shaped, whereas the can-annular combustion chambers are can-shaped, and unlike the annular, it has several combustion chambers. Silo combustors are larger in size than the other two and can have one or more combustion chambers. The silos are used for large-scale operations, whereas the other two are for small-scale applications. The combustion chamber’s output, a high-temperature pressurized gas, will enter a turbine to produce shaft work output, which will drive the compressor. The extra energy will be expelled in the exhaust gases and used for external work or repurposed for other purposes, such as spinning a second power turbine. The fourth step of the gas turbine cycle (Brayton cycle) is omitted in an open cycle gas turbine with open systems because these gas turbines do not reuse the same air for cooling the working fluid (this cooling is the last step of the mentioned cycle.) This fourth cycle is also present in closed-cycle ones.

These elements are all linked together by one or more shafts and are collectively referred to as gas turbines or gas generators.

Gas Turbine Cycle Application

The gas turbine cycle allows these turbines to power various systems such as generators, gas compressors, pumps, aircraft, ships, tanks, and trains.

Difference between an open-cycle and a closed-cycle gas turbine

The main distinction between these two gas turbines is that the open cycle one discharges the exhaust gases that exit the turbine into the atmosphere rather than recirculating them. As previously stated in the steps of the gas turbine cycle, the fourth step occurs only in closed-cycle gas turbines that reuse the same air for cooling the working fluid.

Gas turbine advantages and disadvantages

One of the most significant advantages of gas turbine engines is that they are smaller than many reciprocating engines with comparable power ratings. They also have fewer moving parts than reciprocating engines, resulting in lower maintenance requirements and costs.

Gas turbines also have some drawbacks. The core engine of a gas turbine can be costly because it uses expensive exotic materials. Another disadvantage of gas turbines is that they are less responsive to changes in power demand than reciprocating engines. One of the most important differences is that reciprocating engines are far more efficient than gas turbines at idle speed. However, keep in mind that they can run on a variety of fuels and have lower peak combustion pressures than these engines.

Gas turbines are extremely dependable in applications requiring continuous high power output. Another thing to keep in mind about gas turbines is that they have a very high power-to-weight ratio when compared to reciprocating engines. Furthermore, waste heat from the gas turbine cycle almost entirely dissipates in the exhaust. Not to mention that the gas turbine has less vibration than a reciprocating engine due to the smooth rotation of the main shaft.

Overall, it is highly dependent on your application and the location of the turbine to determine whether the fourth step of the gas turbine cycle is required and which engine to select when purchasing a turbine.

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