diesel engine and cycle .thermodynamics . IT WILL BE VERY USEFUL FOR MECHANICAL ENGINEERING STUDENTS .

1. Active learning assignment
of EME
BY ANANT VYAS
ROLLNO::16BELR003
BRANCH::ELECTRICAL.

2. Introduction
• In July 1878, 19-year-old Rudolf Diesel sat in a classroom at the
Polytechnic High School of Germany, the nation’s top engineering
college, while Professor Carl von Linde lectured on thermodynamics.
Von Linde, one of the school’s most distinguished scholars, was
talking about steam engines, and the young Diesel was disturbed by
the professor’s statement that steam engines utilized only 10% of
the fuel to perform useful work—the rest of the fuel produced
useless heat. In the margin of his notebook, Diesel wrote: “Study
the possibility of development of the isotherm.” These words were
the seed that germinated into one of the great inventions of our
times ,the diesel cycle and engine.

3. What is diesel cycle??
• The Diesel cycle is a combustion process of a reciprocating internal
combustion engine. In it, fuel is ignited by heat generated during the
compression of air in the combustion chamber, into which fuel is then
injected. This is in contrast to igniting the fuel-air mixture with a spark
plug as in the Otto cycle (four-stroke/petrol) engine. Diesel engines
are used in aircraft, automobiles, power generation, diesel-
electric locomotives, and both surface ships and submarines.

4. The image on the left
shows a p-V diagram for
the ideal Diesel cycle.
where P is pressure
and V the volume
or the specific volume .
if the process is placed
on a unit mass basis.
The ideal Diesel cycle
follows the following four
distinct processes:
he

5. The four cycles of diesel cycle.
• The ideal Diesel cycle follows the following four distinct
processes:
• Process 1 to 2 is isentropic compression of the fluid (blue)
• Process 2 to 3 is reversible constant pressure heating (red)
• Process 3 to 4 is isentropic expansion (yellow)
• Process 4 to 1 is reversible constant volume cooling
(green).

6. Diesel cycle
• .
• Work is done by the piston compressing the air
(system)=W(in)
• Heat in is done by the combustion of the fuel=Q(in)
• Work out is done by the working fluid expanding
and pushing a piston (this produces usable
work)=W(out)
• Heat out is done by venting the air=Q(out)
• NET WORK PRODUCED=Q(in)-Q(out).

7. DIESEL CYCLE.
The net work produced is also represented by the area
enclosed by the cycle on the P-V diagram. The net work is
produced per cycle and is also called the useful work, as it can
be turned to other useful types of energy and propel a vehicle
(kinetic energy) or produce electrical energy.
 The summation of many such cycles per unit of time is called
the developed power. This also called the gross work, some of
which is used in the next cycle of the engine to compress the
next charge of air.
• .

8. Diesel cycle continued
• The Diesel cycle is assumed to have constant
pressure during the initial part of the combustion
phase in the diagram. This is an idealized
mathematical model: real physical diesels do have an
increase in pressure during this period, but it is less
pronounced than in the Otto cycle.

9. Diesel engine
• Comparing the two formulae it can be seen that for a given
compression ratio (r), However, a diesel engine will be more efficient
overall since it will have the ability to operate at higher compression
ratios. If a petrol engine were to have the same compression ratio,
then knocking (self-ignition) would occur and this would severely
reduce the efficiency, whereas in a diesel engine, the self ignition is
the desired behavior. Additionally, both of these cycles are only
idealizations, and the actual behavior does not divide as clearly or
sharply. Furthermore, the ideal Otto cycle formula stated above does
not include throttling losses, which do not apply to diesel engines.

10. Thermal efficiency
• Maximum thermal efficiency
• The maximum thermal efficiency of a Diesel cycle is dependent on the
compression ratio and the cut-off ratio. It has the following formula
under cold air standard analysis:

11. Diesel Engine .
• The Diesel engine is a heat engine: it converts heat into work.
During the bottom isentropic processes (blue), energy is transferred
into the system in the form of work , but by definition (isentropic)
no energy is transferred into or out of the system in the form of
heat.
• During the constant pressure (red, isobaric) process, energy enters
the system as heat. During the top isentropic processes (yellow),
energy is transferred out of the system in the form of , but by
definition (isentropic) no energy is transferred into or out of the
system in the form of heat. (refer to fig ).

12. Diesel cycle continued
• During the constant volume (green, isochoric) process, some of
energy flows out of the system as heat through the right
depressurizing process . The work that leaves the system is equal to
the work that enters the system plus the difference between the
heat added to the system and the heat that leaves the system.

13. Diesel engine continued
• Diesel engines have the lowest specific fuel consumption of any large
internal combustion engine employing a single cycle, 0.16 kg/kWh for
very large marine engines (combined cycle power plants are more
efficient, but employ two engines rather than one). Two-stroke diesels
with high pressure forced induction, particularly turbocharging, make up
a large percentage of the very largest diesel engines.
• In North America, diesel engines are primarily used in large trucks, where
the low-stress, high-efficiency cycle leads to much longer engine life and
lower operational costs. These advantages also make the diesel engine
ideal for use in the heavy-haul railroad environment.

14. DERIVATION OF
THERMAL EFFICIECY