The document provides an overview of diesel power plant engineering. It discusses the key components of a diesel power plant including the diesel engine, starting system, fuel supply system, air intake system, lubrication system, cooling system, exhaust system, and governing system. It describes the basic four-stroke operating cycle of a diesel engine and highlights advantages such as simple design and ability to handle varying loads, as well as disadvantages like high operating costs.

1. POWER PLANT ENGINEERING
Diesel power plant
Suryakanth L G
Asst. Prof Mechanical Dept
NMREC, Hyderabad

2. TOPICS INCLUDE….
 Introduction about IC engines
 Types of IC engines
 Plant layout of Diesel power plant
 Fuel supply system
 Air starting equipment
 Lubrication system
 Cooling system
 Super charging

3. Introduction
 Diesel power plants produce power in the range of 2 to 50
MW, are used as central stations for supply authorities and
work.
 They are used as standby sets for continuity of supply such as
hospitals, telephone exchanges, radio stations, cinema theatres
and industries.
 They are suitable for mobile power generation and widely used
in railways and ships.
 Used as Peak Load Plants, Mobile Plants, Stand By Units,
Emergency Plants, Starting Stations, Central Stations,
Industries where power requirement is small 500kW.

4. Advantages of Diesel power plant :
Design and installation are very simple.
It can respond to varying loads without any difficulty.
It occupies less space.
For the same capacity diesel power plant is compact and
smaller than a thermal power plant.
Require less quantity of water for cooling purposes.
No problem of ash handling system.
Disadvantages of Diesel power plant :
 High operating cost.
 High maintenance and lubrication cost.
 The capacity of a diesel plant is limited. They cannot be constructed
in large sizes.
 In a diesel plant noise is a serious problem.
 Diesel power plants cannot supply over loads continuously where
as steam power plants can work under 25% overload continuously.

5. List of Diesel Power Plants in INDIA

6. Heat Engine
Any type of engine or device that derives heat energy from
combustion of fuel and converts to mechanical energy.
 In an Internal combustion engine, combustion takes
place within working fluid of the engine, thus fluid gets
contaminated with combustion products.
 Petrol engine is an example of internal combustion
engine, where the working fluid is a mixture of air and
fuel .
 In an External combustion engine, working fluid gets
energy using boilers by burning fossil fuels or any other
fuel, thus the working fluid does not come in contact
with combustion products.
 Steam engine is an example of external combustion
engine, where the working fluid is steam.

7. Classification of IC Engines
1. According to cycle of operation
 Two Stroke Engine
 Four Stroke Engine
2. According to cycle of combustion
 Otto Cycle Engine(combustion at constant volume)
 Diesel Cycle Engine(combustion at constant pressure)
 Dual Combustion or semi – diesel cycle engine.
3. According to arrangement of Cylinder.
 Horizontal Engine
 Vertical Engine
 V-Type Engine
 Radial Engine
4. According to their Uses
 Stationary Engine
 Portable Engine
 Marine Engine
 Automobile Engine
 Aero Engine

8. 5. According to fuel employed and
method of fuel supply to engine.
 Oil Engine
 Petrol Engine
 Gas Engine
6. According to method of ignition
 Spark ignition
 Compression ignition
7. According to speed of the engine
 Low speed
 Medium Speed
 High Speed
8. According to method of cooling
 Air Cooled
 Water Cooled
9. According to number of cylinders
 Single cylinder
 Multi Cylinder

10. Air Cooled IC Engine

11. Terms Relating to IC Engine

12.  Bore: The inside diameter of the cylinder.
 Stroke: The linear distance along the cylinder axis between
two limiting positions.
 Top dead centre(TDC): The top most position of the piston
towards cover end side of the cylinder.
 Bottom dead centre(BDC): The lowest position of the piston
towards the crank end side of the cylinder.
 Clearance volume(Vc): The volume contained in the cylinder
above the top of the piston, when the piston is at TDC.
 Swept volume(Vs): The volume swept through by the piston in
moving between TDC and BDC.
Total volume = Swept volume + clearance volume
 Compression ratio (r): ratio of total cylinder volume to
clearance volume.
# 5:1 to 9:1 for Petrol engines
#14:1 to 22:1 for Diesel engines

13. Four Stroke Diesel Cycle Engine
Intake or Suction Stroke
Piston moves from TDC to BDC
creating vacuum in the cylinder
Intake valve opens allowing only air to
enter the cylinder and exhaust valve
remains closed.

14. Compression Stroke
•Both valves stay closed
•Piston moves from BDC to TDC,
compressing air to 22:1
•Compressing the air to this extent
increases the temperature inside the
cylinder to above 600 degree
centigrade.

15. Expansion or Power Stroke
• Both valves stay closed.
•When the piston is at the end of
compression stroke(TDC) the injector
sprays a mist of diesel fuel into the
cylinder.
• When hot air mixes with diesel fuel
an explosion takes place in the cylinder.
• Expanding gases push the piston
from TDC to BDC.

16. Exhaust Stroke
• Piston moves from BDC to
TDC
• Exhaust valve opens and the
exhaust gases escape
• Intake valve remains closed

17. 17
2-STROKE DIESEL ENGINE

18. Layout of a Diesel power plant

19. Essential elements of Diesel
Power Plant
Engine System
Starting System
Lubrication System
Fuel System
Air filter and Supercharge
Cooling System
Exhaust System
Governing System

20. 1. Diesel engine :
• Diesel engine is a compression ignition(CI) engine.
• The two –stroke cycle engine is more favored for diesel power
plants.
• The air required for the diesel engine is drawn through the air filter
from the atmosphere and compressed inside the cylinder.
• The fuel(diesel) from the diesel engine is drawn through a filter
from the all day tank and injected into the cylinder through fuel
injectors.
• Because of the high temperature and pressure of the compressed air,
the fuel ignites.
• The fuel burns and the burnt gases expand to do work on the moving part
inside the cylinder called piston.
• This movement of the piston rotates a flywheel and the engine is directly
coupled to electric generator.
• The gases after expansion inside the cylinder is exhausted into the
atmosphere and passes through a silencer in order to reduce the noise.

21. 2. Starting system
• Diesel engine used in diesel power plants is not self starting. The
engine is started from cold condition with the help of an air
compressor.
3. Fuel supply system
• Fuel from the storage tank is pumped through a filter into a
smaller tank called all day tank. This tank supplies the daily
requirements of the diesel engine.
• The all day tank is placed high so that the fuel flows to the engine
under gravity with sufficient pressure.
4. Air intake system
• The air required for the combustion of fuel inside the diesel
engine cylinder is drawn through the air filter. The purpose of the
filter is to remove dust from the incoming air.
• The dry filter may be made of felt, wood or cloth.
• In wet filter, oil bath is used. In this the air passes over a bath of
oil where the dust particles get coated on the oil.

22. 5. Exhaust system:
• The exhaust gases coming out of the engine is very noisy. In
order to reduce the noise a silencer(muffler) is used.
6. Lubricating System:
• This circuit includes lubricating oil tank, oil pump and oil
cooler.
• The purpose of the lubrication system is to reduce the wear of
the engine moving parts. Part of the cylinder such as piston,
shafts, valves must be lubricated.
• Lubrication also helps to cool the engine.
• In the lubrication system the oil is pumped from the
lubricating oil tank through the oil cooler where the oil is
cooled by the cold water entering the engine.
• The hot oil after cooling the moving parts return to the
lubricating oil tank

23. 7. Cooling system
• The temperature of the burning fuel inside the engine
cylinder is in the order of 1500 to 2000 degree Centigrade.
In order to lower this temperature water is circulated
around the engine.
• The water envelopes(water jacket) the engine. The heat
from the cylinder, piston, combustion chamber etc., is
carried by the circulating water.
• The hot water leaving the jacket is passed through the heat
exchanger.
• The heat from the heat exchanger is carried away by the
raw water circulated through the heat exchanger and is
cooled in the cooling tower.

24. FOR GOOD PERFORMANCE OF DIESEL POWER PLANT
 Necessary to maintain the cooling temp within prescribed
limits.
 Lubricating system should work effectively and required
temp and pressure should be maintained.
 The engine should be periodically run even when not
required, should not stand idle for more than 7 days.
 Air filters, oil filters and fuel filters should be periodically
serviced.
 Periodic checking of engine compression and firing
pressure and exhaust temp.

25. Air intake system
 The air intake system conveys fresh air through pipes or ducts
to the 4-stroke engine, scavenging pump & to the supercharger.
 A large diesel engine requires 0.076 to 0.114 m3 of air
/min/KW of power developed. Air is first drawn through a filter
to catch dirt or particles that may cause excessive wear in
cylinders. Filters may be of following types:
a. Dry type (paper, cloth, felt, glass wool etc)
b. Wet type (oil impingement type, oil bath type where oil helps
to catch particles)
Air intake system

26. Following precautions should be taken
while designing air intake systems
Air intake should be located outside the engine room.
Air intake should not be located in confined places to
avoid undesirable acoustic vibrations.
Pressure drop in the air intake line should be
minimum to avoid engine starvation
Air filters should be accessible for periodic cleaning.
In some cases a muffler may be introduced to prevent
engine noise from reaching outside air.

27. Lubrication system
It includes the oil pumps, oil tanks, filters, coolers and
connecting pipes.
The purpose of the lubrication system is to reduce the
wear of the engine moving parts
Part of the cylinder such as piston , shafts , valves
must be lubricated. The lubricant is cooled before
recirculation.
Lubrication also helps to cool the engine.

28. The following are the important
functions of a lubrication system
 LUBRICATION: To keep parts sliding freely past each
other, reducing friction and wear.
 COOLING: To keep surfaces cool by taking away part
of the heat caused by friction.
 CLEANING: To keep the bearings and piston rings
clean.
 SEALING: To form a good seal B/W the piston rings
and cylinder walls.
 REDUCING NOISE: to reduce the noise of the engine
by absorbing vibration.

29. oil tank

30. Exhaust system
The purpose of the exhaust
system is to discharge the
engine exhaust to the atm.
outside the building.
This includes the silencers
and connecting ducts.
The exhaust gases coming
out of the engine is very
noisy.
silencer (muffler) is provide
to reduce the noise.

31. Exhaust pipe leading out of the building should be
short in length with minimum number of bends to
provide as low a pressure loss as possible.
Flexible tubing may be added in exhaust pipe to take
care of misalignments and expansion/contraction and
also to isolate the system from engine vibrations.
Each engine should have its independent exhaust
system.
Where possible, exhaust heat recovery should be made
to improve plant thermal efficiency. E.g., air heating,
low pressure steam generation in diesel-steam power
plant etc

32. Fuel system
 It includes the storage tank, fuel pump, fuel transfer pump, strainers
and heater.
 Pump draws diesel from storage tank to day tank through the filter
 The day tank is usually placed high so that diesel flows to engine
under gravity.
 Diesel is filtered before being injected into the engine by the fuel
injection pump.
strainers

33. The fuel injection system performs
the following functions
 Filter the fuel
 Meter the correct quantity of the fuel to be injected
 Time the injection process
 Regulate the fuel supply
 Secure fine atomization of fuel oil
 Distribute the atomized fuel properly in the combustion
chamber
 Oil is atomized either by blast or pressure jet.
In pressure jet atomization oil is forced to flow
through spray nozzles at pressure above 100 bar. It is
known as solid injection

34. Classification of solid injection systems
Common rail injection system: The system is named
after the shared high-pressure (100 to 200
bars)reservoir (common rail) that supplies all the
cylinders with fuel. With conventional diesel injection
systems, the fuel pressure has to be generated
individually for each injection. With the common rail
system, however, pressure generation and injection are
separate, meaning that the fuel is constantly available
at the required pressure for injection.
Individual pump injection system
Distributor system

35. Common rail injection system
The system is named after the
shared high-pressure (100 to
200 bars)reservoir (common
rail) that supplies all the
cylinders with fuel. With
conventional diesel injection
systems, the fuel pressure has
to be generated individually
for each injection. With the
common rail system, however,
pressure generation and
injection are separate,
meaning that the fuel is
constantly available at the
required pressure for
injection.

36. Individual pump Injection System
 The schematic is
shown in fig.
 An individual pump or
pump cylinder
connects directly to
each fuel nozzle.
 Metering and injection
timing controlled by
individual pumps.
 Nozzle contains a
delivery valve actuated
by the fuel pressure.

37. Distributor System
 The schematic is
shown here.
 The fuel is metered
at a central point.
 A pump meters,
pressurizes and
times the fuel
injection.
 Fuel is distributed to
cylinders in correct
firing order by cam
operated poppet
valves which admit
fuel to nozzles.

38. Cooling system
The cooling system consists of a water source, pump
and cooling towers. The pump circulates water
through cylinder and head jacket. The water takes
away heat form the engine and it becomes hot. The
hot water is cooled by cooling towers and re circulated
for cooling.
There are two systems to circulate the water through
the jacket,
@Gravity system
@Forced circulation system

39. Cooling system
 The temperature of the hot gases inside the cylinder may
be as high as 2750 c . If there is no external cooling, the
cylinder walls and piston will tend to assume the average
temp. of the gases.
 Cooling is necessary because:
 To avoid deterioration or burning of lubricating oil.
 The strength of the materials used for various engine parts
decreases with increase in temperature. Local thermal
stress can develop due to uneven expansion of various
parts.
 Increase in pre-ignition and knocking
 Due to high cylinder head temp. the volumetric efficiency
and hence power output of the engine are reduced.

40. cooling system

41. Elements of cooling system

42. There are two methods of cooling I.C. engines
 Air cooling: Heat is carried
away by the air flowing
over and around the
engine cylinder. It is used
in scooters , motorcycles
etc.
 Liquid cooling: the
cylinder walls and heads
are provided with jackets
through which the cooling
liquid can circulate.

43. Air cooling :
 In this method, heat is
carried away by the air
flowing over and around
the engine cylinder.
 Fins are added on the
cylinder which provide
additional mass of material
for conduction as well as
additional area for
convection and radiating
modes of heat transfer.

44. Liquid cooling
 In this method, the
cylinder walls and head
are provided with
jackets through which
the cooling liquid can
circulate.
 The heat is transferred
from the cylinder walls
to the liquid by
convection and
conduction.
 The liquid gets heated
during its passage
through the cooling
jackets and is itself
cooled by means of an
air cooled radiator
system.

45. Types of Water Cooling System
Thermo Siphon S/m
In this system the
circulation of water is
due to difference in
temperature
(i.e. difference in
densities) of water. So
in this system pump is
not required
but water is circulated
because of density
difference only.

46. Phases in CI engine combustion
In the C.I. engine, combustion may be considered in
four distinct stages,
a. Ignition delay period
b. Period of rapid or uncontrolled combustion
c. Period of controlled combustion
d. After burning

47. Combustion phenomenon in CI engine

48. Ignition Delay
 The ignition delay in a diesel engine is defined as the
time interval between the start of injection and the
start of combustion. This delay period consists of
(a) physical delay, wherein atomization, vaporization
and mixing of air fuel occur and
(b) of chemical delay attributed to pre-combustion
reactions.
 Physical and chemical delays occur simultaneously.

49.  Due to the delay period the pressure reached during
second stage will depend up on the duration of delay
period.
 The longer delay will cause rough running and may
cause diesel knock.
 Delay period should be as short as possible both for
the sake of smooth running and in order to maintain
control over the pressure changes.
 But , some delay period should be necessary other wise
the droplets would not disappear in the air for
complete combustion.

50.  It is the second stage of combustion in C.I engine.
 This period is counted from end of the delay period to
the point of maximum pressure on the indicator
diagram.
 The rise of pressure is rapid because during the delay
period the droplets of fuel have had time to spread
themselves over a wide area and they have fresh air all
around them.
 About 1/3 of heat is evolved during this period
Period Of Rapid Or Uncontrolled
Combustion

51.  At the end of the second stage of combustion , the
temperature and pressure are so high that the fuel
droplets injected in third stage burn almost as they
enter and any further pressure rise can be controlled
by injection rate .
 The heat evolved at the end of the compression is
about 70 to 80 percent.
PERIOD OF CONTROLLED COMBUSTION

52. After burning
 The combustion continues even after the fuel injection
is over , because of poor distribution of particles
 This burning may be continue in the expansion stroke
up to 70 to 80(deg) of crank revolution from TDC.
 The total heat evolved by the entire combustion
process is 95 to 97%; 3 to 5% of heat goes as un burnt
fuel in exhaust.

53. Delay Period in CI engines
 It is the time immediately following injection of the fuel during
which the ignition process is being initiated and pressure does
not rise beyond the value it would have due o the compression of
the air.
 The delay period extend for about 13deg C, movement of the
crank.
Delay period depends upon following:
 Temperature and pressure in the cylinder at time of injection.
 Nature of the fuel mixture strength.
 Presence of residual gases.
 Rate of fuel injection.
 It should be as short as possible

54. Diesel Knock
 If the delay period of C.I. engine is long a large amount
of fuel will be injected and accumulated in he
chamber. The auto ignition of this large amount of fuel
may cause high rate of pressure rise and high
maximum pressure which may cause knocking in the
diesel engine.

55. Cetane number
 Cetane rating of a diesel fuel is the measure of its ability to auto
ignite quickly when it is injected into the compressed and
heated air in he engine.
 Reference mixture of cetane(C16H34)(high ignitability) and
alpha methyl napthalene(C11H10)(low ignitability) are used,
The mixture is made by volume and ignitability of the test fuel is
quoted as the percentage of cetane in the reference mixture
which has same ignitability.
 For higher speed engines: cetane number is 50
 For medium speed engines: cetane number is 40
 For slow speed engines: cetane number is 30
 Cetane number effect the following :
 Exhaust emissions: more if C.N is less
 Noise: More if C.N is less
 Start ability of diesel engine: lessens if C.N. is less

56. Supercharging
 The purpose of supercharging is to raise the volumetric
efficiency above that value which can be obtained by normal
aspiration.
 The engine is an air pump, increasing the air consumption
permits greater quantity of fuel to be added, and results in
greater potential output.
 The power output is almost directly prop. To the air
consumption.
 3 methods to increase the air consumption of an engine are:
1. Increasing the piston displacement: leads to more size and
weight, cooling problems
2. Running the engine at higher speeds leads to mechanical
wear and tear.
3. Increasing the density of the charge, so that greater mass
of charge is introduced in same volume. {Widely Used}

57. Effects of Supercharging
 The Power output of a supercharged engine is higher
than its naturally aspirated counterpart.
 The mechanical efficiencies are better than naturally
aspirated engines.
 It has higher specific fuel consumption that naturally
aspirated engines.