Friday, November 14, 2008
Four processes occur in gas turbine engines, as illustrated above. These processes, first
described by George Brayton and called the Brayton cycle, occur in all internal combustion
engines. The Brayton steps are as follows:
> Compression occurs between the intake and the outlet of the compressor (Line A-B).
During this process, pressure and temperature of the air increases.
> Combustion occurs in the combustion chamber where fuel and air are mixed to explosive proportions and ignited. The addition of heat causes a sharp increase in volume (Line B-C)
> Expansion occurs as hot gas accelerates from the combustion chamber. The gases at constant pressure and increased volume enter the turbine and expand through it. The sharp decrease in pressure and temperature (Line C-D).
> Exhaust occurs at the engine exhaust stack with a large drop in volume and at a constant pressure (Line D-A).
The number of stages of compression and the arrangement of turbines that convert the energy of accelerating hot gas into mechanical energy are design variables. However, the basic operation of all gas turbines is the same.