Brayton Cycle

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The Brayton Cycle is the theoretical cycle used to describe the internal workings of a basic (Shet U., Sundararajan T., & Mallikarjuna J., n.d.) gas turbine engine.

This model was first developed by George Brayton in 1872 as the basis for his "Ready Motor", a piston engine that consisted of a compressor and expander (Wikipedia, 2011). Later, the same principles were applied to produce modern turbine engines.

The Brayton Model

A basic turbine engine consists of a compressor, a mixing chamber (a burner) and a turbine section. The Brayton cycle is characterized by two constant-pressure processes and two isentropic processes:

1. Adiabatic process - Air is drawn in and compressed in the compressor (volume decreases, pressure increases).
2. Isobaric process - Heat is added in the burner (volume increases, pressure constant).
3. Adiabatic process - Expansion of the gas takes place across the turbine section (volume increase, pressure decreases).
4. Isobaric process - Further heat loss as gas is returned to the atmosphere (volume decreases, pressure constant).

745px-Brayton_cycle.svg.png
Idealised Brayton Cycle (Wikipedia, 2011)

Unfortunately, due to inefficiencies in the engine, some power is lost in the compressor and turbine sections of the engine and so the represented model can never be fully achieved. By increasing the compression ratio, total power is able to be increased, hence the significant size of the compressor sections of today's engines.

References
1. full reference in the following format AUTHOR (date work). Title. Reference location, date publication.
2. Shet U., Sundararajan T., & Mallikarjuna J. (n.d.). Brayton Cycle (Simple Gas Turbine). http://nptel.iitm.ac.in/courses/IIT-MADRAS/Applied_Thermodynamics/Module_4/11_Brayton_Cycle.pdf, n.d.

Want to know more?

Wikipedia
Brayton Cycle
Massachusetts Institute of Technology
Thermodynamics and Propulsion - Brayton Cycle
Aviation Knowledge
Turbojet Engines

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