Calculator · Thermal Engineering
Diesel Cycle
The ideal compression-ignition cycle: isentropic compression, constant-pressure heat addition up to the cutoff ratio, isentropic expansion and constant-volume rejection. State 1, r, r_c and γ fix the whole cycle.
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 | 692.32 kJ/kg |
|---|---|
| Heat rejected q_out | 352.8 kJ/kg |
| Net work w_net | 339.52 kJ/kg |
| Thermal efficiency η | 49.04 % |
| 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 | 1.8379 MPa | 0.21525 m³/kg | 1378.44 K |
| 4 | 263.902 kPa | 0.861 m³/kg | 791.705 K |
Assumptions
- · ideal air-standard cycle
- · constant specific heats
- · ideal isentropic compression/expansion
- · constant-pressure heat addition
- · constant-volume heat 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)·(r_cᵞ − 1)/(γ(r_c − 1))
v3 = r_c·v2
q_in = cp(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 at constant pressure and rejected at constant volume.
As r_c → 1 the result approaches the Otto efficiency at the same compression ratio.