The document discusses three thermodynamic cycles: 1) The Carnot cycle consists of two reversible isothermal and two reversible adiabatic processes. It establishes the theoretical maximum efficiency possible for a heat engine. 2) The Joule cycle consists of two constant pressure and two reversible adiabatic processes. It models the air engine proposed by Joule and is used in refrigeration. 3) The dual combustion cycle combines aspects of the Otto and Diesel cycles, with heat absorbed partly at constant volume and partly at constant pressure. It describes internal combustion engines.

1. CARNOT CYCLE, JOULE CYCLE,
DUAL COMBUSTION CYCLE
Imran Sattar 2017-BT-Mech-759
Muhammad Imtiaz 2017-BT-Mech-760
Jamshed Khan 2017-BT-Mech-761
Hafiz Arsalan Hassan 2017-BT-Mech-762

2. DEFINATION
 This cycle devised by Francis Engineer Nicolas Leonard Sadi Carnot.
 In a Carnot cycle, the following substance is subjected to a cyclic
operation consisting of two isothermal and two reversible adiabatic or
isentropic operations.
 It is obvious that it is impossible to realize Carnot’s engine in actual
practice.

3. DIAGRAM

4. THEORY
1. A reversible isothermal gas expansion process. In this process, the ideal gas
in the system absorbs qin amount heat from a heat source at a high
temperature Th, expands and does work on surroundings.
2. A reversible adiabatic gas expansion process. In this process, the system is
thermally insulated. The gas continues to expand and do work on
surroundings, which causes the system to cool to a lower temperature, Tl.
3. A reversible isothermal gas compression process. In this process,
surroundings do work to the gas at Tl, and causes a loss of heat, qout.
4. A reversible adiabatic gas compression process. In this process, the system is
thermally insulated. Surroundings continue to do work to the gas, which
causes the temperature to rise back to Th.

5. ANIMATION

6. NUMERICAL

7. JOULE CYCLE DEFINATION
 The cycle for the air engine proposed by Joule.
 It consist of two constant pressure and two reversible adiabatic or
isentropic processes.
 This cycle, reversed, is used in refrigeration machines.

8. DIAGRAM

9. THEORY
1)-First stage (Constant Pressure Process). The air is heated at a constant pressure
from initial temperature T1 to a temperature T2 represented by the curve 1-2 in fig.
 Heat supplied to the air ,
Q 1-2 = m cp (T2 – T1)
2)-Second stage (Reversible Adiabatic or Isentropic Expansion). The air is allowed
to expand reversibly and adiabatically from v2 to v3. The reversible adiabatic
expansion is represented by the curve 2-3 in fig. The temperature of the air falls
from T2 to T3. In this process, no heat is absorbed or rejected by the air.

10. THEORY
3)-Third stage (Constant Pressure Cooling). The air is now cooled at constant
pressure from temperature T3 to a temperature T4 represented by 3-4 in fig.
4)-Fourth stage (Reversible Adiabatic or Isentropic Compression). The air is now
compressed reversibly and adiabatically from v4 to v1. The reversible adiabatic
compression is represented by the curve 4-1 in fig. The temperature of the air
increases from T4 to T1. Again no heat, is absorbed or rejected by the air.
 Work done = Heat supplied – Heat rejected
 = m cp (T2 – T1) – m cp (T3 – T4)
 And efficiency, η = m cp (T2 – T1) – m cp (T3 – T4)
 m cp (T2 – T1)

11. NUMERICAL

12. DUAL COMBUSTION CYCLE
 This cycle is a combination of Otto and Diesel cycles. It is sometimes called
semi-diesel cycle, because semi-diesel engines work on this cycle.
 In this cycle, heat is absorbed partly at a constant volume and partly at a
constant pressure.
 The ideal dual combustion cycle consist of two reversible adiabatic or
isentropic, two constant volume and a constant pressure processes.
 It can be used to describe internal combustion engines.

13. DIAGRAM

14. THEORY
 1)-First stage (Constant Pressure Heating). The air is heated at constant
pressure from initial temperature T1 to a temperature T2 represented by
the curve 1-2 in fig.
 Heat absorbed by the air, Q1-2 = m cp (T2-T1)
 2)-Second stage (Reversible Adiabatic or isentropic expansion). The air is
expended reversibly and adiabatically from temperature T2 to a
temperature T3 as shown by the curve 2-3 in fig. In this process, no heat is
absorbed or rejected by the air.
 3)-Third stage (Constant Volume Cooling). The air is now cooled at
constant volume from temperature T3 to temperature T4 as shown by the
curve 3-4 in fig.
 Heat rejected by the air, Q3-4 = m cv (T3-T4)

15. THEORY
 4)-Fourth stage (Reversible Adiabatic or Isentropic Compression). The air is
compressed reversibly and adiabatically from temperature T4 to a
temperature T5 as shown by the curve 4-5in fig. In this process, no heat is
absorbed or rejected by the air.
 5)-Fifth stage (Constant Volume Heating). The air is finally heated at constant
volume from temperature T5 to a temperature T1 as shown by the curve 5-1 in
fig.
 Heat absorbed by the air, Q5-1 = m cv (T1- T5)
 We see that air has been brought back to its original conditions of pressure,
volume and temperature, thus completing the cycle. We know that,
 Work done = Heat absorbed – Heat rejected
 = [m cp (T2 – T1) + m cv (T1 – T5)] – m cv (T3 – T4)

16. ANIMATION

17. NUMERICAL