Gas Turbine Performance
Gas Turbine Performance
Gas Turbine Performance
Performance
Inlet Air System
Outline
Gas turbines are steady-flow power machines in which a gas (usually air) is
compressed, heated, and expanded for the purpose of generating power.
The term turbine is the component which delivers power from the gas as it
expands; it is also called an expander.
The basic thermodynamic cycle on which the gas turbine is based is known as
the Brayton cycle.
The most efficient power generation systems in commercial service are gas
turbine combined cycle plants.
1 oC
Refrigeration Systems.
Mechanical Chillers
Absorption Chillers.
Evaporative Methods.
Evaporative Coolers.
Inlet Fogging.
Mechanical Chillers
Other options such a steam driven compression are also used in industry.
Mechanical Chillers
Mechanical Chillers
Advantage
Disadvantage
Expertise is needed to
Absorption Chillers
Disadvantage
Cooling systems based on latent heat as the water evaporates are preferred in
dry/desert climates not near the sea where the relative humidity is low, and where
the system can boost the turbine output by nearly 12%.The problem is that for a
desert climate, a large amount of water is a limiting factor. For warm and humid
climates the evaporative-kind of air cooling system may not increase the turbine
output by more than 2-3%.
Evaporative Cooler
Advantage
Disadvantage
Fogging
This cooling system is based on fogging nozzles and a high pressure pump system. Fogging
reduces inlet air temperature by evaporating a spray of water after the filter stage but early
enough that moisture cannot reach turbine compressor blades. Usually moisture eliminators
are installed before the compressor stage to reduce the possibility of moisture carrying-over,
which could produce serious damage in the turbine. Cooling capacity is limited by ambient
conditions, and wet bulb temperature is theoretically the lowest limit. Typical fog system
performance is around 80-95%, and its effectiveness is limited by the difference between dry
bulb and wet bulb temperatures that depends on the relative humidity in the area.
This technology is a low-cost solution, with simple operation and low maintenance. However,
this technology also presents some disadvantages: cooling beyond wet bulb temperature is
impossible; performance is highly dependent on relative humidity changes; de-mineralized
water usage is necessary; there is some risk of erosion to blades of the first stages in the
compressor; corrosion may occur due to incomplete atomisation of injected water.
Fogging
Fogging
Advantage
Disadvantage
Limitation on capacity
improvement
Highly influenced by the
site wet bulb