L2 - Thermodynamic cycle efficiency Flashcards
What is Entropy?
The measure of a system’s thermal energy per unit temperature that is unavailable for doing useful work
What is Enthalpy?
A thermodynamic quantity equivalent to the total heat content of a system. Internal energy + Pressure*Volume
What are the 4 stages of the Brayton Cycle?
1 - Isentropic compression in compressor
2 - Heat Supplied at constant pressure
3 - Isentropic expansion through turbine
4 - Heat rejected at constant pressure
What does isentropic mean?
Adiabatic and Ideal
What does adiabatic mean?
No heat is transferred
What is the term for constant pressure?
Isobaric
What is created using the Brayton cycle?
Excess enthalpy after driving compressor (line 3/4 bigger than 1/2). Used to accelerate flow (thrust)
What does a hogher pressure ratio mean?
Higher efficiency
What are the effects of reality on the Brayton Cycle?
More work is required by the compressor and less work is produced by the turbine.
What are the casues of inefficiencies?
Fluid friction
Frictional losses in hardware
Fluid mixing
What does a prime dash signify?
The isentropic process
What is the slight benefit in a unideal compression process?
The temperature is higher and so less fuel is required in the combustion phase.
