Calculator · Thermal Engineering
Otto Cycle
The ideal spark-ignition cycle: isentropic compression and expansion with constant-volume heat addition and rejection. Set the compression ratio and γ for the efficiency; state 1 and the peak temperature fix the four corner states.
Inputs
Ideal cycle limits: reversible Carnot models between two reservoirs, and ideal air-standard Otto, Diesel and Brayton cycles with constant specific heats. Real machines fall below these values.
Results
Thermal efficiency η
Ideal air-standard limit with constant specific heats.
| Heat added q_in | 796.99 kJ/kg |
|---|---|
| Heat rejected q_out | 346.91 kJ/kg |
| Net work w_net | 450.08 kJ/kg |
| Thermal efficiency η | 56.47 % |
| State | p | v | T |
|---|---|---|---|
| 1 | 100 kPa | 0.861 m³/kg | 300 K |
| 2 | 1.8379 MPa | 0.10762 m³/kg | 689.219 K |
| 3 | 4.8 MPa | 0.10762 m³/kg | 1800 K |
| 4 | 261.165 kPa | 0.861 m³/kg | 783.496 K |
Assumptions
- · ideal air-standard cycle
- · constant specific heats
- · ideal isentropic compression/expansion
- · constant-volume heat addition and rejection
Explore in the Lab
The full cycle state travels; the Lab adds the state diagram and the comparison view.
Technical reference
η = 1 − r^(1−γ)
T2 = T1·r^(γ−1)
q_in = cv(T3 − T2)
- T_H
- hot reservoir temperature (absolute)[K]
- T_C
- cold reservoir temperature (absolute)[K]
- r
- compression ratio[—]
- r_c
- cutoff ratio[—]
- r_p
- pressure ratio[—]
- γ
- heat-capacity ratio cp/cv[—]
Air-standard cycle with constant specific heats and ideal isentropic compression and expansion.
Heat is added and rejected at constant volume.
The peak temperature T3 must exceed the post-compression temperature T2.