Gas Turbine Efficiency
For a simple cycle gas turbine the efficiency is determined by the pressure ratio of the compressor.
r = pressure ratio
γ = ratio of heat capacities (=1.4 for air)
Simple cycle gas turbine efficiency versus pressure ratio.
There are a number of ways of increasing the engine efficiency other than just increasing the pressure ratio:
- Regeneration - waste heat from the exhaust gas is used to preheat the compressed air before it enters the combustion chamber
- Intercooling - the compressed air is cooled between stages
- Reheating - a second combustor is added between turbine stages to add more energy to the gas stream
- Combined cycle - a gas turbine is used as the first stage with a steam turbine as the second stage being driven by steam generated by waste heat in the gas turbine exhaust.
H Cohen, G F C Rogers and H I H Saravanamuttoo, "Gas Turbine Theory", 3rd Ed., Longman Scientific & Technical.
See also: Gas Turbine.