Diesel Power Plant

•1
SNIST (JNTUH)
UNIT:III
DIESEL POWER PLANT
Dr. S. VIJAYA BHASKAR
M.Tech (Mech)., Ph.D(Mech)., Ph.D (Mgmt)
Professor in Mechanical Engineering

UNIT – III: Syllabus
INTERNAL COMBUSTION ENGINE PLANT
DIESEL POWER PLANT:
Introduction
– IC Engines, types, construction
– Plant layout with auxiliaries
– fuel supply system, air starting equipment,
lubrication and cooling system
– super charging.
•2

INTRODUCTION
•3
Diesel power plants are installed in the following situations.
Supply of coal and water is not available in sufficient quantity
Power is to be generated in small quantity.
Stand by sets are required for emergency purposes in hospitals,
telephone exchanges, radio stations and cinemas.
Diesel power plants in the range of 2 to 50 MW capacities are
used.
Short time and temporary power production. Long term
planning required for the development of hydro and thermal
plants.
 Demands for diesel power plants are increased for electric
power generation because of difficulties in construction of new
hydro power plants and enlargement of old hydro plants
Diesel power plants used for electric generation are more
reliable and long lived piece of equipment compared with other
types of plants.

•6
IC Engines Parts
 Cylinder
 Cylinder Head
 Piston.
 Piston Rings
 Gudgeon Pin
 Connecting Rod
 Crank Shaft:
 Crank
 Engine Bearing
 Crankcase
 Flywheel
 Governor
 Valves
 Fuel Pump
 Fuel Injector
 Combustion chamber

The four-stroke cycle
•7
 Suction Stroke: With the
movement of the piston
from TDC to BDC during
the stroke the inlet valve
opens and air at
atmosphere pressure is
drawn inside the engine
cylinder. The exhaust valve
is closed and represented
by the line 5-1 in the P-V
diagram.

The four-stroke cycle Diesel Engine
•8
 Compression Stroke: The air drawn at atmospheric pressure during the
suction stroke is compressed to high pressure and temperature (35 bars & 600
C) as the piston moves from BDC to TDC. This operation is represented by 1-
2 in the diagram. Both inlet and exhaust vales do not open during this stroke.
 Working/Expansion Stroke: As the piston
going to reach TDC a metered quantity
of fuel is injected into the hot compressed air
in the fine sprays by the fuel injector and the
fuel starts burning at constant pressure shown
by the line 2-3 in the diagram. The hot gases
of the cylinder expand adiabatically to the
point 4, thus doing work on the piston shown
as 3-4 in the diagram.
 Exhaust Stroke: The piston moves BDC to TDC then exhaust gases escape
to the atmosphere through the exhaust valve. When the piston reaches the
TDC the exhaust valve closes and the cycle is completed and this is
represented by the line 1-5 in the diagram.

Two Stroke Diesel Engine - Basics
Two stroke engines operate on the same principles as a four
stroke engine.
 Intake- Fuel mixture is drawn into crankcase during upstroke
 Compression- mixture is compressed in the crankcase during
downstroke and again during upstroke before combustion
 Combustion-fuel is recompressed and ignited in cylinder during
upstroke
 Exhaust- burned mixture is forced out by fresh mixture being
forced in during downstroke
Piston fires once every revolution. No traditional valves like a four-
stroke. Piston serves as a “valve” by covering the ports.

Upstroke (compression)
One-way valve opens and fuel mixture is drawn into
crankcase
Transfer port is covered
Fuel mixture is compressed (again) and ignited
Piston covers exhaust port during compression

Downstroke (Combustion)
Combustion forces piston down compressing fuel
mixture in crankcase
Intake port is covered and valve is forced to close
Transfer port is uncovered forcing fuel mixture into
cylinder
This fuel mixture pushes the exhaust out the exhaust
port

The two-stroke cycle Diesel Engine
•13
• The cylinder L is connected to the closed crank chamber
C.C. During the upward stroke of the piston M, The gases
in L are compressed and at the same time fresh air enters
the crank chamber through the valve V.

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
5. According to fuel employed and method of fuel
supply to the 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. According to method of Governing:
i) Hit and Miss Governed Engine ii) Quality Governed
Engine iii) Quantity Governed Engine
11.According to Valve Arrangement:
i) Over Head Valve Engine ii) L-Head Valve Engine
iii) T-Head Valve Engine iv) F-Head Valve Engine

1. According to cycle of operation:
i) Two stroke ii) Four stroke
2. According to cycle of combustion:
i) Otto cycle ii) Diesel cycle iii) Dual combustion cycle
3. According to arrangement of cylinders:
i) Horizontal Engine ii) Vertical Engine
iii) V-type Engine iv) Radial Engine
4. According to their use :
i) Stationary Engine ii) Portable Engine
iii) Marine Engine
iv) Automobile Engine v) Aero Engine
5. According to fuel used:
i) Oil Engine ii) Petrol Engine
iii) Gas Engine iv) Kerosene Engine
6. According to the speed of the engine used:
i) Low Speed Engine ii) Medium Speed iii) High Speed Engine
•18

7. According to method of Ignition:
i) Spark Ignition Engine ii) Compression Ignition Engine
8. According to method of Cooling:
i) Air Cooled Engine ii) Water Cooled Engine
9. According to method of Governing:
i) Hit and Miss Governed Engine ii) Quality Governed Engine
iii) Quantity Governed Engine
10. According to Valve Arrangement:
i) Over Head Valve Engine ii) L-Head Valve Engine
iii) T-Head Valve Engineiv) F-Head Valve Engine
11. According to Number of Cylinders:
i) Single Cylinder Engine ii) Multi Cylinder Engine
•19

Diesel Plant Layout with Auxiliaries
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Diesel Power Plant Layout
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•25
Diesel Plant Auxiliaries
A. Engine : This is main component of the plant which
develops required power. The engine is generally
coupled to the generator.
B. Air Intake System: The function of the air filter is to
remove the dust from the air which is taken by the
engine.
C. Exhaust System: This system includes silencer and
connecting ducts. The temperature of the exhaust
gases are high, so the heat of the exhaust gases may be
used for heating the oil or air supplied to the engine.

•26
D. Fuel System: It includes the storage tank, fuel pump,
strainer and heater. The fuel is supplied according to
the load on the plant.
E. Cooling System: This system includes water
circulating pumps, cooling towers or spray ponds and
water filtration plant. The purpose of the cooling
system is to carry the heat from engine cylinder to
keep the temperature of the cylinder in the safe range
and extends the life.

Diesel Plant Auxiliaries
•27
F. Lubrication System: It includes the oil pumps, oil
tanks, filters, coolers and connecting pipes. The
function of the lubricating system is to reduce the
friction of moving parts and reduce the wear and tear
of the engine.
G. Engine Starting System: This includes compressed
air tanks. The function of this system is to start the
engine from cold by supplying the compressed air.
H. Governing System: The function of the governing
system is to maintain the speed of the engine constant
irrespective of load on the plant. This is done by
varying the fuel supply to the engine according to load.

Air Intake System
•28
• Fresh air through pipes
•Filters used (dry/wet)
•Silencer b/w engine and
intake (Vibrations)

Air Intake System
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 The air intake system conveys fresh air through pipes or ducts
to the engine.
 Filters used to catch dirt particles in the air.
 Filters are of dry or oil bath types are used.
 Silencer is provided in between the engine and intake.
Some of the precautions while constructing an air intake system.
 Air intakes may not be located inside the engine room
 Air should not be taken from a confined space otherwise air
pulsation causes serious vibration problem.
 Diameter of the air intake lines should not be too small or
too big, but be relevant size related to the engine power.
 Air intake filters may not be located close to the roof of the
engine.

Exhaust System
•30
• Function of this exhaust system
is to discharge the engine flue
gases into atmosphere.
• Exhaust manifold connects the
engine cylinder exhaust outlets
to the exhaust pipe which is
provided with a muffler to
reduce the pressure in the
exhaust line and eliminate noise.
• The exhaust gases are used by
providing the waste heat
recovery devices to preheat the
oil and air supplied to the
engine.

Fuel System
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Main flow is made workable and arranging of piping equipment with
heaters, bypasses, shut offs, drain lines, relief valves, strainers and
filters, flow meters and temperature indicators.
The flow plans depends on type of fuel, engine equipment and size of
the plant.
The main storage tank contains manholes for repairs, fill lines to
receive oil, vent lines to discharge vapour, overflow return lines for
controlling oil flow and suction line to withdraw oil.
Day tanks supply the daily fuel needs of the engine i.e. for 8 hrs.
These tanks are placed high because oil may flow to the engine under
gravity.
The fuel oil supply system has to consider the following points.
 Provisions for cleanliness and for changing over of lines during
emergencies.
 All suction lines pipe joints should be tested under pressure and joints
tested with soap solution.
 Cleanliness in handling the bulk oil tanks.

Fuel Injection System
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A very small quantity of fuel must be measured out, injected,
atomized and mixed with combustion air.
The function of the fuel injection system are:
 Filter the fuel.
 Measure correct quantity of fuel to be injected.
 Time the fuel injection
 Control the rate of fuel injection
 Break up the fuel into fine particles
 Properly distribute the fuel in the combustion chamber.
Atomization of fuel oil has been done by air blast and pressure
spray.
Types of fuel injection systems are
 Common rail injection system
 Individual pump injection system
 Distributor system.

Common Rail Injection System
•34
A single pump supplies high
pressure fuel to header or
common rail, a relief valve
holds pressure constant.
The control wedge adjusts
the lift of mechanically
operated valve to set amount
and time of injection.

Common Rail Injection System
•35
A controlled pressure system
has pump which maintains set
head pressure.
Pressure relief and timing
valves regulated injection time
and amount of fuel.
Spring loaded spray valve acts
as a check.

Individual Fuel Pump Injection System
•36
Pump with an individual
cylinder directly connects to
each fuel nozzle.
Pump meters charge and control
injection timing.
Nozzle contain a delivery valve
actuated by the fuel oil
pressure.

Distributor Fuel Injection System
•37
In this system fuel is metered
at a central point.
A pump pressurizes, meters
the fuel and times the
injection.
Fuel is distributed to cylinders
in correct firing order by cam
operated poppet valves which
open to admit fuel to the
nozzles.

 The temperature of gases inside the engine cylinder may vary from 35 º to as
high as 2750 º C during the cycle.
 At this temperature range the cylinder walls, cylinder and piston metals will
loose their characteristics and piston seizes the liners.
 If the cylinder wall temperature rises above 65 º C the lubricating oil evaporates
and the piston and cylinders are damaged.
 In order to protect these parts from this heating effect proper cooling system is
required.
 The high temperature reduces the strength of piston and cylinder liners.
 Some times the overheating leads to pre ignition in spark ignition engines.
 There are two methods used in cooling the IC engines.
1. Air cooling and 2.liquid cooling.
•38

•39
• Heat is carried by the air flowing over and around the
engine cylinders.
• Fins are cast on the cylinder head and barrel to provide
the additional conductive and radiating surfaces.
• The fins connected to the right angles to the cylinder axis.
• Advantages:
•No water jackets are required
•Absence of cooling pipes, radiation makes system
simpler.
•No danger of coolant leakage.
•No problem of freezing troubles
•Weight per B.H.P of the air cooled engine is less than
water cooled engine.
•It is a self contained unit , no external components
•Installation is easier than water cooling.

•40
Disadvantages:
•Their movement is noisy, non uniform cooling and maintenance is not easy.
•Output of air cooled engine is less than that of water cooled engine.
•Smaller useful compression ratio.

 It is indirect method of cooling the engine.
 The cylinder walls and heads are provided with jackets through
which cooling liquid can be circulated.
 The heat is transferred from cylinder walls to the liquid by
conduction and convection.
 The liquid becomes heated as it is passing through jackets and
cooled by means of air cooled radiator system.
 The heat from liquid in turn is transferred to air.
 The stationary diesel engine plants uses this cooling system as open
and closed systems.
A. Open or Single circuit system:
◦ Pump draws the water from cooling pond and forces it into
the main engine jacket.
◦ Water after recirculation return to the cooling pond.
B. Close or Double circuit system:
 Water is made to flow though the heat exchanger when it takes up
the heat of jacket water and returns back to the cooling pond.
•41

 Advantages:
◦ Fuel consumption is less.
◦ Cooling water can be conveniently heated when ever
required.
◦ We can design any size of the cooling system for the engine.
◦ No problem of noise.
◦ Uniform heating takes place.
 Disadvantages:
◦ Water requirement depends on the system
◦ Power absorbed by pump for circulating water is higher than
that of cooling fans.
◦ Failure of water cooling system can damage the engine
◦ Cost of this system is high
◦ Additional maintenance required for water cooling system.
•42

LUBRICATION SYSTEM
 Lubrication system required between two surfaces having relative
motion.
 The purpose of lubrication is as follows.
 Reduce the friction and wear between the parts having relative
motion.
 Cool the surfaces by carrying away the heat generated due to
friction.
 To seal a space adjoining surfaces such as piston rings and cylinder
liners.
 To clean the surface by carrying away the carbon and metal particles
caused by wear.
 To absorb shock between bearings and other parts to reduce noise.
The parts which requires the lubrication in the diesel engine are:
Main crank shaft bearing, big end bearing, small end or gudgeon pin
bearings, piston rings and cylinder walls, timing gears, cam shaft and
cam shaft bearings, valve mechanism, valve guides etc.
Various lubrication systems used in the diesel engine are
A. Wet sump lubrication system B. Dry sump lubrication system
C. Mist sump lubrication system
•43

A. WET SUMP LUBRICATION SYSTEM
 These systems employ a large capacity oil sump at the
base of crank chamber from which the oil is drawn by
a low pressure oil pump and delivered to various
parts.
 Oil then gradually returns back to the sump after
serving the purpose.
 Oil is always contained in the sump which is drawn
by pump though a strainer.
 In this system having three types
Splash system
Full pressure system
Semi pressure system
•44

SPLASH SYSTEM
 This system is used on some small four stroke
stationary engine.
 Caps on the big end bearings of connecting rods are
provided with scoops which, when the connecting rod
is in the lowest position, just dip into the oil troughs
and thus directs the oil through holes in the caps to the
big end bearings.
 Due to splash of oil it reaches the lower portion of the
cylinder walls, crank shaft and other parts requiring
lubrication.
 Oil level in the troughs is maintained by means of a
oil pump which takes oil from sump through a filter.
 This system is suitable for low and medium speed
engines having moderate bearing load pressures. •46

•48
•Holes drilled
through the main
crankshafts bearing
journals, communicate
oil to the big end bearing

FULL PRESSURE SYSTEM
 Oil is delivered by the pressure pump at pressure
ranging from 1.5 to 4 bars.
 Oil under pressure is supplied to main bearings of
crank shaft and cam shaft.
 Holes drilled through the main crankshafts bearing
journals, communicate oil to the big end bearing and
also small end bearings through holes drilled in
connecting rods.
 A pressure gauge is provided to confirm the
circulation of oil to the various parts.
 A pressure regulating valve also provided on the
delivery side of this pump to prevent excessive wear.
•49

SEMI PRESSURE SYSTEM
 This is the combination of splash and pressure system.
 Main supply of the oil is located in the base of crank chamber.
 Oil is drawn from the lower portion of the sump through a
filter and is delivered by means of a gear pump at pressure
above 1 bar to the main bearings.
 The big end bearings are lubricated by means of spray through
nozzle.
 Oil pressure gauge is provided to indicate satisfactory oil
supply.
 The system is less costly to install as compare to pressure
system.
 It enable higher bearing loads and engine speeds to be
employed as compared to splash system.
•50

B. DRY SUMP LUBRICATION SYSTEM
 In this system the oil from the sump is carried to a storage
tank out side the engine cylinder block.
 Oil from the sump is pumped by means of a sump pump
though filters to the storage tank.
 Oil from storage tank is pumped to the engine cylinder through
oil cooler.
 Oil pressure varies from 3 to 8 kgf/cm ².
 This system is generally adopted for high capacity engines.
•51

C. MIST LUBRICATION SYSTEM
 This system is used for two stroke engines.
 These engines are lubricated by adding 2 to 3 percent lubricating oil in the
fuel tank.
 The oil and fuel mixture is inducted through the carburetor.
 The gasoline is vapourised, oil in the form of mist goes via crankcase into
cylinder.
 The oil which impinges on the crank case walls lubricates the main and
connecting rod bearings and rest of the oil which passes to the cylinder
during charging and scavenging periods, lubricates piston, piston rings and
the cylinder.
 Advantages are simple system and low cost because of absence of pump.
 Disadvantages :
 lubricating oil invariably burns in the combustion chamber.
 Loses the anti corrosion properties which damage bearings.
 For effective mixing separate additives are required.
 High lubricant consumption
 Engine over- oiled most of the time because of no control over the
proportion of lubricating oil •53

1. Starting by an auxiliary engine:
 In this system the auxiliary unit is mounted close to the main engine
and drive through a clutch and gear.
 Clutch is first disengaged and the auxiliary engine started by hand or
self started motor.
 When it warms up and runs normally the drive gear is engaged through
clutch and main engine is cranked for starting.
2. Use of Electric motor or Self starter:
 These are employed for small diesel and gasoline engines.
 Storage battery (12 to 36v) is used to supply power to an electric motor
which is geared to flywheel with arrangement for automatic
disengagement after the engine started.
 Motor draws heavy current and designed to engage for 30 s, after
which is cooled off for a minute and then re engaged.
 When the engine is running a small dc generator on the engine serves
to charge the battery.
•54

3. Starting using Compressed Air system:
This system is commonly used for starting the large diesel
engines employed for stationary power plant service.
 Compressed air at about 17 bar supplied from an
air tank and admitted to the engine cylinders
making them work like reciprocating air motor to
run the engine shaft.
 The air tank is charged by a motor or gasoline
engine driven compressor.
 This system includes storage tank, safety valve and
interconnecting pipe work.
•55

 The purpose of supercharging is to raise the
volumetric efficiency above that value which can be
obtained by normal aspiration.
Volumetric Efficiency: It is the ratio of the actual volume
of the charge drawn in during the suction stroke to the swept
volume of the piston.
 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 proportional to the
air consumption.

 Three methods to increase the air consumption are
◦ 1. Increasing the piston displacement: but leads
to more size and weight, cooling problems
◦ 2. Running the engine at higher speeds: but 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}

 The apparatus used to increase the air density is
called supercharger. It is similar to a compressor
( centrifugal type), which provides greater mass of
charge with same piston displacement.
 The supercharger produces following effects:
1. Provides better mixing of air fuel mixture due to
turbulent effect of supercharger.
2. The temperature of charge is raised as it is
compressed, resulting in higher temperature within the
cylinder, so better vaporization of fuel, but dec in density
of charge.
3. Power required to run the supercharger is obtained from
engine

SUPERCHARGING
•59
Super charging is used to produce a higher power output in
diesel engine and other systems.
If we increase the air consumption essentially it permits
greater quantity of fuel to be added and results in greater
potential output.
The air consumption can be increased by three methods.
If we increase the piston displacement the size and weight
of the engine increases and results in cooling problem etc.
Running the engine at high speeds increases frictional
losses and induces inertia stresses on the engine.

•60
SUPERCHARGING
Last method which is generally used to increase
engine capacity and known as supercharging. Greater
air and fuel supplied to the engine there by drawing
greater engine powers.
Generally centrifugal compressors are generally used
as superchargers where the mixture enters the rotating
impeller in direction parallel to the shaft and leaves
the impeller radially and passes through the diffuser.

SUPERCHARGING
•61
The purpose of the supercharging is to increase the volumetric
efficiency.
Advantages of super charging:
 Power increase: Out put can be increased by 30 – 50 % at the same speed of the
engine.
 Fuel economy: The combustion in the super charged engine is better than as it
provides better mixing of air and fuel. SFC is less than general one and thermal
efficiency is also higher.
 Mechanical efficiency: It is better than natural one at the same speed. This is
because power increase due to supercharging increases faster than the rate of
increase in friction losses.
 Scavenging: Its scavenging action is better in two stroke super charged engine
than normal engine because the quantity of residual gases is reduced with
increase in super charged pressure.
 Knocking: Super charging reduces the possibility of knocking in diesel engine
because delay period is reduced with an increase in super charged pressure. This
super charging results in smooth running of the engine.

SUPER CHARGING IN SI ENGINE
•62
•Main difference
between two engines is
• Increase in
pressures over
normal engine
• Results in pumping
loop is positive one.

•63
SUPER CHARGING IN CI ENGINE
•Super charging in
CI engines: Improves
the combustion in
diesel engine.
•Increase in intake temperature reduces the volumetric efficiency and thermal
efficiency but increase in density due to pressure compensates for this and
inter cooling is not necessary except for highly superheated engines.
•Better mixing and
combustion in super
charged engine - has
better SFC

•64
• Effect of Supercharging on Power and Fuel

•65
PLANT MAINTENANCE IN DIESEL ENGINES
• Diesel engine power plant maintenance depends on the various
factors.
• Careful supervision of the equipment used for recording
temperature, pressure and electrical data are essential.
• The temperature inside the engine should not be allowed to exceed
the safe limit.
• The temperature, flow and quantity of fuel oil should be checked
from time to time.
• The fuel oil must cleaned from dist and other impurities by means
of filters.
• When filter elements becomes choke it should be replaced by a new
one.
• Dirt in fuel oil ruins the fine lap of fuel injection pumps and plugs
the injection nozzle orifice.
• Fuel tank cleaned thoroughly
• The temperature and flow of coolants, lubricating oil and exhaust
gases should be checked at regular intervals.

Diesel Power Plant

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