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How Gas Turbine Power Plants Work 

The combustion (gas) turbines used in many of today's natural-gas-fueled power plants are complex machinery, but they are comprised of three major sections:

At hundreds of miles per hour, the compressor takes air into the engine, pressurises it, and feeds it to the combustion chamber. The combustion system, which is normally composed of a ring of fuel injectors that deliver a steady stream of fuel into combustion chambers where it mixes with the air. The combination is burned at temperatures exceeding 2000 degrees Fahrenheit. The combustion process generates a high-temperature, high-pressure gas stream, which enters and expands through the turbine portion.

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The whirling blades are spun as hot combustion gas expands through the turbine. The whirling blades have two purposes: they drive the compressor, which draws more pressured air into the combustion area, and they spin a generator, which generates energy.

There are two types of land-based gas turbines: (1) heavy frame engines and (2) aeroderivative engines. Heavy frame engines have lower pressure ratios (usually less than 20) and are physically huge. The pressure ratio is the ratio of the discharge pressure of the compressor to the incoming air pressure. Aeroderivative engines, as the name implies, are adapted from jet engines and run at extremely high compression ratios (typically in excess of 30). Aeroderivative engines are often highly compact and useful where lesser power outputs are required. Because large frame turbines have higher power outputs, they can produce more emissions and must be engineered to emit minimal levels of pollutants such as NOx.

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The temperature at which a turbine works is an important factor in its fuel-to-power efficiency. Improved temperatures often result in higher efficiency, which can lead to more cost-effective operation. The gas moving through a typical power plant turbine can reach temperatures of 2300 degrees Fahrenheit, yet some of the key metals in the turbine can only endure temperatures of 1500 to 1700 degrees Fahrenheit. As a result, air from the compressor may be used to cool important turbine components, lowering overall thermal efficiency.

One of the Department of Energy's advanced turbine program's significant accomplishments was breaking through prior constraints on turbine temperatures by combining revolutionary cooling systems and improved materials. The advanced turbines developed by the Department of Energy's research programme were capable of increasing turbine intake temperatures to as high as 2600 degrees Fahrenheit - about 300 degrees hotter than prior turbines.

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Installing a recuperator or heat recovery steam generator (HRSG) to collect energy from the turbine's exhaust is another approach to improve efficiency. A recuperator is a device that recovers waste heat from the turbine exhaust system and uses it to pre-heat compressor discharge air before it enters the combustion chamber. A heat recovery steam generator (HRSG) creates steam by recovering heat from the turbine exhaust. Heat recovery steam generators are another name for these boilers. The high-pressure steam generated by these boilers can be utilised to generate extra electric power via steam turbines, a combination known as a combined cycle.

Energy conversion efficiency for a single cycle gas turbine can range between 20 and 35 percent. Because of the higher temperatures obtained in the Department of Energy's turbine programme, future hydrogen and syngas fueled gas turbine combined cycle plants are expected to achieve efficiencies of 60 percent or higher.

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