Thermodynamic Cycles
A hot air engine thermodynamic cycle can (ideally) be made out of 3 or more processes (typical 4). The processes can be any of these:
- isothermal process (at constant temperature, maintained with heat added or removed from a heat source or sink)
- isobaric process (at constant pressure)
- isometric / isochoric process (at constant volume)
- adiabatic process (no heat is added or removed from the working fluid)
- isentropic process, reversible adiabatic process (no heat is added or removed from the working fluid - and the entropy is constant)
- isenthalpic process (the enthalpy is constant)
Some examples (not all hot air cycles, as defined above) are as follows:
| Cycle | Process 1-2 (Compression) |
Process 2-3 (Heat Addition) |
Process 3-4 (Expansion) |
Process 4-1 (Heat Rejection) |
Notes |
|---|---|---|---|---|---|
| Power cycles normally with external combustion - or heat pump cycles: | |||||
| Bell Coleman | adiabatic | isobaric | adiabatic | isobaric | A reversed Brayton cycle |
| Carnot | isentropic | isothermal | isentropic | isothermal | |
| Ericsson | isothermal | isobaric | isothermal | isobaric | the second Ericsson cycle from 1853 |
| Rankine | adiabatic | isobaric | adiabatic | isobaric | Steam engine |
| Scuderi | adiabatic | variable pressure and volume |
adiabatic | isochoric | |
| Stirling | isothermal | isochoric | isothermal | isochoric | |
| Stoddard | adiabatic | isobaric | adiabatic | isobaric | |
| Power cycles normally with internal combustion: | |||||
| Brayton | adiabatic | isobaric | adiabatic | isobaric | Jet engines the external combustion version of this cycle is known as first Ericsson cycle from 1833 |
| Diesel | adiabatic | isobaric | adiabatic | isochoric | |
| Lenoir | isobaric | isochoric | adiabatic | Pulse jets (Note: Process 1-2 accomplishes both the heat rejection and the compression) |
|
| Otto | adiabatic | isochoric | adiabatic | isochoric | Gasoline / petrol engines |
Yet another example is the Vuilleumier cycle.
Read more about this topic: Hot Air Engines
Famous quotes containing the word cycles:
“The stars which shone over Babylon and the stable in Bethlehem still shine as brightly over the Empire State Building and your front yard today. They perform their cycles with the same mathematical precision, and they will continue to affect each thing on earth, including man, as long as the earth exists.”
—Linda Goodman (b. 1929)