Gas turbines: operation, types, applications

The first attempts to create a gas turbine (combustion turbine) are attributed to Leonardo Da Vinci, who designed a chimney with a structure of internal windmills, moved by rising exhaust gases. However, the first engine, which was a gas turbine, was finally patented almost 400 years later, at the end of the 18th century, during the industrial revolution. Today, gas turbines are an increasingly popular solution, widely used in the power generation, aerospace and military industries. In this entry, we will tell you a bit about the basic design of this type of engine, the principle of its operation, and how gas turbines are classified in practice.

Gas turbines: design and construction

The construction of a gas turbine is an individual issue, depending on the specific device. However, it is possible to distinguish a few basic elements that are generally found in engines of this type. These include:

• air intake;
• compressor;
• combustion chamber;
• turbine – a shaft with profiled blades.

In terms of design, the gas turbine is therefore a very simple device that largely resembles the turboshaft engine used in helicopters.

However, when analysing the design of a turbine, one should also not forget about the solutions that are fundamental to improving the quality of the air drawn in through the intake. But what for? Turbine operation requires large amounts of such air. Unfortunately, the air can be contaminated with dust, moisture, etc., which negatively affects the energy efficiency of the device and shortens the life of the filter, increasing maintenance costs. As a result, some turbines use evaporative cooling systems – pre-coolers often allow the air to be effectively filtered, so that it is the cooler, rather than the first air filter, that removes much of the impurities, extending its durability.

Gas turbine: principle of operation

If you wonder how a gas turbine works, we have good news for you – the mechanism of this type of engine is not complicated.

• The primary task of the turbine is to convert the energy of the exhaust gas, which is produced as a result of fuel combustion, into mechanical energy.
• Importantly, after the gas turbine has done its work, you not only get mechanical power in the form of shaft rotation but also thermal energy, i.e. hot exhaust gas, which can be used to generate steam or hot water.
• To explain the characteristics of gas turbines most simply: air combines with natural gas or other fuels to create a mixture that allows the turbine to be set in motion. The turbine, in turn, by turning the shaft of the generator, generates electricity.

Gas turbine – principle of operation step-by-step The conversion of chemical energy into mechanical energy is possible primarily through the process of air compression and expansion.

• In the air intake, the absorptive atmospheric air is sucked into the compressor.
• In a compressor, as the name implies, the sucked air is compressed. The gas molecules are compressed, thus raising the pressure and temperature of the gas.
• The gas then “passes” into the combustion chamber, where the compressed air burns with the fuel.
• The hot gas is forced into the turbine, which is a special shaft with blades that it passes through as it begins to expand. The expansion process allows the shaft to be set in motion.

Nowadays, gas turbines become increasingly popular in Poland and around the world, so engine manufacturers face many challenges. Among the most important are the search for new, more effective cooling solutions for turbine nodes and the development of technologies to extend the service life of key structural components.

Types of gas turbines

Today, gas turbines are used primarily in the power generation industry in the broad sense. High efficiency is one of the main advantages of this type of turbines, so they could be an interesting response to the growing demand that the world is currently showing for electricity. This is especially true for gas turbines in cogeneration projects based on natural gas.

Also not insignificant to the popularity of gas turbines is the possibility of using various types of liquid and renewable fuels and gases, which, in the era of diversification of energy sources, is of crucial importance. A single unit can be adapted to run on multiple types of liquid and gaseous fuels

Gas turbines are very popular in the energy-intensive industry, where they are used as generators of electricity, steam and other types of process heat. However, it doesn’t stop there. Frequently used solutions also include gas turbines in power plants and CHP plants.

What makes their popularity grow?

• One of the reasons is environmental factors – gas turbines are the CHP units with the lowest levels of NO_x, CO₂ or UHC emissions.
• They are the simplest and cheapest devices that can replace large coal or oil units.
• They fit perfectly with the EU’s decarbonization plans, the transition to hydrogen is seamless and does not require a technology change.

These are the devices with the highest annual availability, capable of operating all year round without interruption (with annual inspection).

• In addition,  strictly economic issues are also important. Gas turbine operating costs are significantly lower for > 6MWe generating capacity compared to competing technologies. Their lightweight design and high power density enable very low-cost, low-investment development. The oldest units in Poland have been in operation for more than 30 years, which is unattainable for other generation solutions.

The price of a gas turbine calculated per kW of installed capacity decreases with the size of the unit. The higher the installed power, the cheaper the installation.

mail: jbigoszewski@eneria.pl

Written by: Jakub BIGOSZEWSKI

Gas Turbines Manager & Expert