This document discusses the diesel cycle, which is an important thermodynamic cycle that diesel engines use. It consists of four processes: (1) isentropic compression, (2) constant pressure heat addition, (3) isentropic expansion, and (4) constant volume heat rejection. Diesel engines have higher efficiency than gasoline engines due to their high compression ratio. They are used widely in vehicles, power generation, ships and more. The document provides details on the p-v and T-s diagrams and explanations of each process in the diesel cycle.

1. Engineering Thermodynamics
Diesel cycle
Composed by:-
Singh Roshan
(Student)

2. Details
• Topic:-Diesel Cycle
• Branch:-Mechanical Department

3. Introduction to Diesel Cycle
• Diesel Cycle was derived by Dr. Rudolph Diesel in 1893, with an idea to attain a
higher thermal efficiency, with a high compression ratio.
• This is an important cycle on which all the diesel engines work.
• It is also known as constant pressure cycle as heat is received at a constant
pressure.
• The ideal diesel cycle consists of two reversible adiabatic or isentropic, a constant
pressure and a constant volume processes.
• Diesel engines are used in aircrafts,automobiles,power generation,diesel
electromotives, and both surface ships and submarines.

4. Classification of Diesel Engines
Two Stroke
Diesel
Engine
Four Stroke
Diesel
Engines

5. Working of Diesel Cycle
• Process 1-2:- Isentropic compression
• Process 2-3:-Constant Pressure (Isobaric)heat
addition process
• Process 3-4:-Isentropic Expansion
• Process 4-1:-Constant Volume (Isochoric)heat
rejection process

6. Diagram
p-v Diagram T-S Diagram

7. Process 1-2
Isentropic Compression
In this process,the piston moves from BDC to TDC and compression of air
takes place isentropically.It means that during compression the entropy remains
constant and there is no flow of heat out of the cylinder walls happens.Here
the air is compressed so the process increases from P1 to P2,Volume decreases
from V1 to V2,Temperature increases from T2 to T2 and entropy remains
constant (i.e.s1=s2)

8. Process 2-3
Constant Pressure heat addition process:-
• In this process the, the hot body is kept in contact with the cylinder and heat
addition to the air takes place at constant pressure. During this process, the
piston rest for a moment at TDC. The pressure remains constant (i.e. P2 =
P3), volume increases from V2 to V3, temperature increases from T2 to T3,
entropy increases from S2 to S3.

9. Process 3 -4
Isentropic Expansion
• In this process, after heat addition, the expansion of air takes place
isentropically and work is obtained from the system. The piston moves
downward during this process and reaches to BDC. The pressure falls from
P3 to P4, Volume increases from V3 to V4, the temperature falls from T3 to
T4 and entropy remains constant (i.e. S3=S4).

10. Process 4-1
Constant Volume heat rejection process:-
• In this process, the piston rest at BDC for a moment and the cold body is
brought in contact with the cylinder and the heat rejection takes place at
constant volume. The pressure decreases from P4 to P1, temperature
decreases from T4 to T1, entropy decreases from S4 to S1 and volume
remains constant (i.e.V4 = V1).

11. Thermal
Efficency

13. DIESEL ENGINES: PROS & CONS
Advantages
• Highly efficient
• Greater torque
• Durable
• Good resale value
Disadvantages
• More expensive to purchase
• Fuel is pricey
• Less accessible
• Higher maintenance cost

14. Applications:-
• Diesel generators
• Locomotives
• Farming equipment
• In construction
equipment
• In cargo and cruise ships
• In buses and trucks

15. Thanks for viewing.
🙏