1. Ideal Diesel and Dual Cycles for I.C. Engines
P M V Subbarao
Professor
Mechanical Engineering Department
Rational Thermodynamic Structure of an Engine…

2. Fuel calorific value (kJ/kg)
Ford ECOSPORT
Details
1.5P Ambiente
1.5D Ambiente
Displacement (cc)
1499
1498
Max Power output(kW)
Max. Torque (Nm)
2750RPM
Compression Ratio
11:1
16:1
Fuel calorific value (kJ/kg)
48,000
44.800

3. Air-Standard Diesel cycle
Process 1 2 Isentropic compression
Process 2  3 Constant pressure heat addition
Process 3  4 Isentropic expansion
Process 4  1 Constant volume heat rejection
Qin
Qout v2 TC v1 BC
Cut-off ratio:

4. Higher efficiency is obtained by adding less heat per cycle, Qin,
Thermal Efficiency
rc=1
rc=2
Typical CI Engines
15 < r < 20
rc=3
When rc (= v3/v2)1 the Diesel cycle efficiency approaches the efficiency of the Otto cycle
Higher efficiency is obtained by adding less heat per cycle, Qin,
 run engine at higher speed to get the same power.

8. Isentropic Compression model with variable properties
For compression from 1 to 2:

10. Isentropic expansion model with variable properties
For expansion from 3 to 4:

13. Schematic of a diesel spray & flame with temperatures and chemistry

14. Dual Cycle Process 1  2 Isentropic compression
Process 2  2.5 Constant volume heat addition
Process 2.5  3 Constant pressure heat addition
Process 3  4 Isentropic expansion
Process 4  1 Constant volume heat rejection 3
Qin
2.5 3 2
Qin
2.5 4 2 4 1 1
Qout

15. Thermal Efficiency