Gas Gas TurbinesTurbines

By: Katie By: Katie SteddenbenzSteddenbenz

How they workHow they work Energy is added to the gas stream Energy is added to the gas stream Combustion increases the Combustion increases the

temperature, velocity, and volume temperature, velocity, and volume of the gas flowof the gas flow

Turbine rotates, powering the Turbine rotates, powering the compressorcompressor

Energy is then extracted in the Energy is then extracted in the form of shaft power, compressed form of shaft power, compressed air and thrust air and thrust

Brayton CycleBrayton Cycle

Gas turbines are described Gas turbines are described thermodynamically by the Brayton cyclethermodynamically by the Brayton cycle

In this cycle:In this cycle:1.1. air is compressed isentropically air is compressed isentropically 2.2. combustion occurs at constant pressure combustion occurs at constant pressure 3.3. heated air expands through the turbineheated air expands through the turbine4.4. heat is rejected into the atmosphereheat is rejected into the atmosphere

Advantages of gas Advantages of gas turbine enginesturbine engines Very high power-to-weight ratioVery high power-to-weight ratio More size efficientMore size efficient Moves in one direction only, with Moves in one direction only, with

fewer moving partsfewer moving parts Low operating pressuresLow operating pressures High operation speedsHigh operation speeds Low lubricating oil cost and Low lubricating oil cost and

consumptionconsumption

Disadvantages of gas Disadvantages of gas turbine enginesturbine engines More expensive compared to a More expensive compared to a

similar-sized reciprocating enginesimilar-sized reciprocating engine More complex machining operationsMore complex machining operations Usually less efficient than Usually less efficient than

reciprocating engines, especially at reciprocating engines, especially at idleidle

Delayed response to changes in Delayed response to changes in power settingspower settings

Questions?Questions?