1. Thermo-Economic Analysis of Otto Cycle
P M V Subbarao
Professor
Mechanical Engineering Department
Compact & Efficient Description forStructure of an Engine…

2. Simplified Thermodynamic Cycles
Air-standard analysis is used to perform elementary analyses of IC engine cycles.
Simplifications to the real cycle include:
1) Intake and exhaust processes not considered
2) Fixed amount of air (ideal gas) for working fluid
3) Combustion process not considered
4) Engine friction and heat losses not considered
5) Specific heats independent of temperature

3. Otto’s Model for Engine cycle
Process 1 2 Isentropic compression
Process 2  3 Constant volume heat addition
Process 3  4 Isentropic expansion
Process 4  1 Constant volume heat rejection
Compression ratio: v2 TC v1 BC
Qout
Qin

4. First Law Analysis of Otto Cycle
12 Isentropic Compression
AIR

7. First Law Analysis of Otto Cycle
23 Constant Volume Heat Addition
AIR
Qin TC

8. 3  4 Isentropic Expansion
AIR
3  4 Isentropic Expansion

9. 4  1 Constant Volume Heat Removal
Qout
AIR BC

10. First Law Analysis of Cycle
Net cycle work:
Cycle thermal efficiency:

11. Clue to Achieve Higher Efficiency