P-V and T-s Diagram for the Otto Cycle.
An Otto cycle is an idealized thermodynamic cycle which describes the functioning of a typical spark ignition reciprocating piston engine.The Otto cycle is constructed out of:
TOP and BOTTOM of the loop:a pair of quasi-parallel adiabatic processes
LEFT and RIGHT sides of the loop: a pair of parallel isomorphic processes
The processes are described by:
1. Process 1-2 is an is entropic compression of the air as the piston moves bottom dead center to top center.
2. Process 2-3 is a constant-volume heat transfer to the air from an external source while the piston is at top center. This process is intended to represent the ignition of the fuel-air mixture and the subsequent burning.
3. Process 3-4 is an is entropic expansion (power stroke).
4. Process 4-1 completes the cycle by a constant-volume in which heat is rejected from the air while the piston is a bottom dead center.
Cycle Analysis :
Processes 1-2 and 3-4 do work on the system but no heat transfer occurs during adiabatic expansion and compression . Processes 2-3and 4-1 are isomorphic therefore heat transfer occurs but no work in done.No work is produced by the system. Four different equations can be derived by neglecting kinetic energy and considering the first law of thermodynamics (energy conservation).
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