The document discusses internal combustion (I.C.) engines. It begins by outlining the objective of identifying types of I.C. engines, their parts, and how each part works. It then provides classifications of I.C. engines and lists their major components. The working principles of four-stroke and two-stroke engines are explained, including diagrams of their cycles. Key aspects covered are intake, compression, combustion, power and exhaust strokes in four-stroke engines and the use of crankcases and ports to enable intake and exhaust in two strokes.

1. Saif al-din ali Madhi
Department of Mechanical Engineering/ College of Engineering/ University of Baghdad
25/6/2020 1 | P a g e
[heat lap 4]
University of Baghdad
Name: - Saif Al-din Ali

2. Saif al-din ali Madhi
Department of Mechanical Engineering/ College of Engineering/ University of Baghdad
25/6/2020 2 | P a g e
TABLE OF CONTENTS
1. Objective
2. I.C Engine
3. The Types of I.C Engine
4. Engine Components
5.THE WORKING PRINCIPLE OF ENGINES
5.1.Four-Stroke Spark-Ignition Engine
5.2.Two-Stroke Engine
6.Discussion

3. Saif al-din ali Madhi
Department of Mechanical Engineering/ College of Engineering/ University of Baghdad
25/6/2020 3 | P a g e
Experiment Name
Introduction about I.C Engine
1. Objective: Identify the types of internal combustion engines
and parts and how work each part.
2. I.C Engine: The purpose of internal combustion engines is the
production of mechanical power from the chemical energy
contained in the fuel.
3. The Types of I.C Engine:
I C classified
Application
Basic engine
design
Working
cycle
Valveor port
design and location
Method of mixture
preparationFuel
Method of ignition
Combustion
chamber design
Method of load
control
Method of cooling
Fig(1) The Types of I.C Engine

4. Saif al-din ali Madhi
Department of Mechanical Engineering/ College of Engineering/ University of Baghdad
25/6/2020 4 | P a g e
1. Application: Automobile, truck, locomotive, light aircraft, marine,
portable power system, power generation.
2. Basic engine design: Reciprocating engines (in turn subdivided by
arrangement of cylinders: e.g., in-line, V, radial, opposed), rotary
engines (Wankel and other geometries).
3. Working cycle: Otto cycle: Four-stroke cycle; naturally aspirated
(admitting atmospheric air), supercharged (admitting
precompressed fresh mixture), and turbocharged (admitting fresh
mixture compressed in a compressor driven by an exhaust turbine),
two-stroke cycle: crankcase scavenged, supercharged, and
turbocharged. Diesel cycle: naturally aspirated, supercharger,
turbocharger.
4. Valve or port design and location: Overhead (or I-head) valves,
underhead (or L-head) valves, rotary valves, cross-scavenged
porting (inlet and exhaust ports on opposite sides of cylinder at one
end), loop-scavenged porting (inlet and exhaust ports on same side
of cylinder at one end), through-or uniflow-scavenged (inlet and
exhaust ports or valves at different ends of cylinder).
5. Fuel: Gasoline (or petrol), fuel oil (or diesel fuel), natural gas, liquid
petroleum gas, alcohols (methanol, ethanol), hydrogen, dual fuel.
6. Method of mixture preparation: Carburetion, fuel injection into
the intake ports or intake manifold, fuel injection into the engine
cylinder.
7. Method of ignition: Spark Ignition SI (in conventional gas and
petrol engines where the mixture is uniform and in stratified-charge
engines where the mixture is non-uniform), compression ignition CI
(in conventional diesels, as well as ignition in gas engines by pilot
injection of fuel oil).
8. Combustion chamber design: Open chamber (many designs: e.g.,
disc, wedge, hemisphere, bowl-in-piston), divided chamber (small
and large auxiliary chambers; many designs: e.g., swirl chambers,
prechambers).
9. Method of load control: Throttling of fuel and air flow together so
mixture composition is essentially unchanged, control of fuel flow
alone, a combination of these.
10.Method of cooling: Water cooled, air cooled, (other than by natural
convection and radiation)

5. Saif al-din ali Madhi
Department of Mechanical Engineering/ College of Engineering/ University of Baghdad
25/6/2020 5 | P a g e
Fig. 2 Classification of heat engines
4. Engine Components:
A cross section of a single cylinder spark-ignition engine with overhead
valves is shown in Fig.2. The major components of the engine and their
functions are briefly described below
Fig.3. Cross-section of a spark-ignition engine

6. Saif al-din ali Madhi
Department of Mechanical Engineering/ College of Engineering/ University of Baghdad
25/6/2020 6 | P a g e
1. Cylinder Block : The cylinder block is the main supporting structure
for the various components. The cylinder of a multi cylinder engine are
cast as a single unit, called cylinder block. The cylinder head is mounted
on the cylinder block. The cylinder head and cylinder block are provided
with water jackets in the case of water cooling or with cooling fins in the
case of air cooling. Cylinder head gasket is incorporated between the
cylinder block and cylinder head. The cylinder head is held tight to the
cylinder block by number of bolts or studs. The bottom portion of the
cylinder block is called crankcase. A cover called crankcase which
becomes a sump for lubricating oil is fastened to the bottom of the
crankcase. The inner surface of the cylinder block which is machined and
finished accurately to cylindrical shape is called bore or face
2. Cylinder : As the name implies it is a cylindrical vessel or space in
which the piston makes a reciprocating motion. The varying volume
created in the cylinder during the operation of the engine is filled with the
working fluid and subjected to different thermodynamic processes. The
cylinder is supported in the cylinder block.
3. Piston : It is a cylindrical component fitted into the cylinder forming
the moving boundary of the combustion system. It fits perfectly (snugly)
into the cylinder providing a gas-tight space with the piston rings and the
lubricant. It forms the first link in transmitting the gas forces to the output
shaft
4. Combustion Chamber : The space enclosed in the upper part of the
cylinder, by the cylinder head and the piston top during the combustion
process, is called the combustion chamber. The combustion of fuel and the
consequent release of thermal energy results in the building up of pressure
in this part of the cylinder.
5. Inlet Manifold : The pipe which connects the intake system to the inlet
valve of the engine and through which air or air-fuel mixture is drawn into
the cylinder is called the inlet manifold.
6. Exhaust Manifold : The pipe which connects the exhaust system to the
exhaust valve of the engine and through which the products of combustion
escape into the atmosphere is called the exhaust manifold.

7. Saif al-din ali Madhi
Department of Mechanical Engineering/ College of Engineering/ University of Baghdad
25/6/2020 7 | P a g e
7. Inlet and Exhaust Valves : Valves are commonly mushroom shaped
poppet type. They are provided either on the cylinder head or on the side
of the cylinder for regulating the charge coming into the cylinder (inlet
valve) and for discharging the products of combustion (exhaust valve) from
the cylinder.
8. Spark Plug : It is a component to initiate the combustion process in
Spark Ignition (SI) engines and is usually located on the cylinder head.
9.Connecting Rod : It interconnects the piston and the crankshaft and
transmits the gas forces from the piston to the crankshaft. The two ends of
the connecting rod are called as small end and the big end . Small end I
connected to the piston by gudgeon pin and the big end is connected to the
crankshaft by crankpin.
Fig. 4 Top and bottom dead centres
10. Crankshaft : It converts the reciprocating motion of the piston into
useful rotary motion of the output shaft. In the crankshaft of a single
cylinder engine there are a pair of crank arms and balance weights. The
balance weights are provided for static and dynamic balancing of the
rotating system. The crankshaft is enclosed in a crankcase.
11.Piston Rings : Piston rings, fitted into the slots around the piston,
provide a tight seal between the piston and the cylinder wall thus
preventing leakage of combustion gases .

8. Saif al-din ali Madhi
Department of Mechanical Engineering/ College of Engineering/ University of Baghdad
25/6/2020 8 | P a g e
12. Gudgeon Pin : It links the small end of the connecting rod and the
piston.
13. Camshaft : The camshaft (not shown in the figure) and its associated
parts control the opening and closing of the two valves. The associated
parts are push rods, rocker arms, valve springs and tappets. This shaft also
provides the drive to the ignition system. The camshaft is driven by the
crankshaft through timing gears.
14. Cams : These are made as integral parts of the camshaft and are so
designed to open the valves at the correct timing and to keep them open for
the necessary duration (not shown in the figure).
15. Fly Wheel : The net torque imparted to the crankshaft during one
complete cycle of operation of the engine fluctuates causing a change in
the angular
5. THE WORKING PRINCIPLE OF ENGINES
If an engine is to work successfully then it has to follow a cycle of
operations in a sequential manner. The sequence is quite rigid and cannot
be changed.
5.1 Four-Stroke Spark-Ignition Engine
In a four-stroke engine, the cycle of operations is completed in four strokes
of the piston or two revolutions of the crankshaft. During the four strokes,
there are five events to be completed, viz., suction, compression,
combustion, expansion and exhaust. Each stroke consists of 180◦ of
crankshaft rotation and hence a four-stroke cycle is completed through
720◦ of crank rotation. The cycle of operation for an ideal four-stroke SI
engine consists of the following four strokes : (1) suction or intake stroke;
(2) compression stroke; (3) expansion or power stroke and (4) exhaust
stroke. The details of various processes of a four-stroke spark-ignition
engine with overhead valves are shown in Fig.3 (a-d). When the engine
completes all the five events under ideal cycle mode, the pressure-volume
(p-V ) diagram will be as shown in Fig..4.

9. Saif al-din ali Madhi
Department of Mechanical Engineering/ College of Engineering/ University of Baghdad
25/6/2020 9 | P a g e
Fig. 5 Working principle of a four-stroke SI engine
Fig. 6 Ideal p-V diagram of a four-stroke SI engine
1. Suction or intake stroke
0→1 (p-V diagram) Fig4 & a Fig 3 , the inlet valve is open and the
exhaust valve is closed. Starts with the movement of the piston from
TDC to BDC, while drawing fresh charge (air + fuel mixture) into
the cylinder through the open inlet valve. To increase the mass
inducted, inlet valve opens for a period of 220 – 260 O CA
2. Compression stroke The charge taken into the cylinder during the
suction stroke is compressed by the return stroke of the piston 1→2
(p-V diagram), during this stroke both valves are closed. The
mixture which fills the entire cylinder volume is compressed into
clearance volume. At the end of the compression stroke the mixture
is ignited with the help of a spark plug located on the cylinder head.
In ideal gas it is assumed that burning gas takes place
instantaneously when the piston is at the top dead center and hence
the burning process can be approximated as heat addition at constant
volume. During the burning process the chemical energy of the fuel
is converted into heat energy producing a temperature rise of about
2000 oC 2→3 (p-V diagram). The pressure at the end of the

10. Saif al-din ali Madhi
Department of Mechanical Engineering/ College of Engineering/ University of Baghdad
25/6/2020 10 | P a g e
combustion process is considerably increased due to the heat release
from the fuel.
3. Expansion or power stroke The high pressure of the burnt gases
forces the piston towards the BDC 3→4 (p-V diagram). Both the
valves are in closed position. Of the four-strokes only during this
stroke power is produced. Both pressure and temperature decrease
during expansion
4. Exhaust strokeAt the end of the expansion stroke the exhaust valve
opens and the inlet valve remains closed. The pressure falls to
atmospheric level a part of the burnt gases escape 4→1 (p-V
diagram). The burned gases exit the cylinder through the open
exhaust valve, due to the pressure difference at first and then swept
by the piston movement from BDC to TDC 5→0 (p-V diagram).
Exhaust valve closes when the piston reaches TDC at the end of the
exhaust stroke and some residual gases trapped in the clearance
volume remain in the cylinder
These residual gases mix with the fresh charge coming in during the
following cycle, forming its working fluid. Each cylinder of a four
stroke engine completes the above four operation in two engine
revolutions, one revolution of the crankshaft occurs during the
suction and compression strokes and the second revolution during
the power and exhaust strokes. Thus, for one complete cycle there is
only one power stroke while the crankshaft turns by two revolutions.
For getting higher output from the engine the heat release (process
2→3 in pV diagram) should be as high as possible and the heat
rejection (process 3→4 in p-V diagram) should be as small as
possible. So, one should be careful in drawing the ideal pV diagram.
5.2 Two-Stroke Engine
if the two unproductive strokes, viz., the suction and exhaust could be
served by an alternative arrangement, especially without the movement of
the piston then there will be a power stroke for each revolution of the
crankshaft. In such an arrangement, theoretically the power output of the
engine can be doubled for the same speed compared to a four-stroke
engine. Based on this concept, Dugald Clark (1878) invented the two-
stroke engine.

11. Saif al-din ali Madhi
Department of Mechanical Engineering/ College of Engineering/ University of Baghdad
25/6/2020 11 | P a g e
In two-stroke engines, the cycle is completed in one revolution of the
crankshaft. The main difference between two-stroke and four-stroke
engines is in the method of filling the fresh charge and removing the burnt
gases from the cylinder. In the four-stroke engine these operations are
performed by the engine piston during the suction and exhaust strokes
respectively. In a two-stroke engine, the filling process is accomplished by
the charge compressed in crankcase or by blower. The induction of the
compressed charge moves out the product of combustion through exhaust
ports. Therefore, no piston strokes are required for these two operations.
Two strokes are sufficient to complete the cycle, one for compressing the
fresh charge and the other for expansion or power stroke.
Fig. 7 Crankcase scavenged two-stroke SI engine
The above figure shows one of the simplest two-stroke engines, viz., the
crankcase scavenged engine. The figure below shows the ideal indicator
diagram of such an engine. The air or charge is indicated into the crankcase
through the spring-loaded inlet valve when the pressure in the crankcase is
reduced due to upward motion of the piston during compression stroke.
After the compression and ignition, expansion takes place in the usual way
Fig. 8 Ideal p-V diagram of a two-stroke SI engine

12. Saif al-din ali Madhi
Department of Mechanical Engineering/ College of Engineering/ University of Baghdad
25/6/2020 12 | P a g e
During the expansion stroke the charge in the crankcase is compressed. Near the
end of the expansion stroke, the piston uncovers the exhaust ports and the
cylinder pressure drops to atmospheric pressure as the combustion products
leave the cylinder. Further movement of the piston uncovers the transfer ports,
permitting the slightly compressed charge in the crankcase to enter the engine
cylinder. The top of the piston has usually a projection to deflect the fresh charge
towards the top of the cylinder before flowing to the exhaust ports. This serves
the double purpose of scavenging the upper part of the cylinder of the
combustion products and preventing the fresh charge from flowing directly to
the exhaust ports. The same objective can be achieved without piston deflector
by proper shaping of the transfer port. During the upward motion of the piston
from BDC the transfer ports close first and then the exhaust close when
compression of the charge begins and the cycle is repeated

13. Saif al-din ali Madhi
Department of Mechanical Engineering/ College of Engineering/ University of Baghdad
25/6/2020 13 | P a g e
6.Discussion:
1. Write a short report about I.C engines?
An internal combustion engine (ICE) is a heat engine in which
the combustion of a fuel occurs with an oxidizer (usually air) in a
combustion chamber that is an integral part of the working fluid
flow circuit. In an internal combustion engine, the expansion of
the high-temperature and high-pressure gases produced by
combustion applies direct force to some component of the engine.
The force is applied typically to pistons, turbine blades, rotor or a
nozzle. This force moves the component over a distance,
transforming chemical energy into useful work.
All details of the engine are covered in the above report
Engine classification by
cylinder arrangements
In-line U-cylinder
V-type Radial
X-type H-type
Opposed
cylinder
Opposed pistonDelta type
Fig. 9 Engine classification by cylinder arrangements

14. Saif al-din ali Madhi
Department of Mechanical Engineering/ College of Engineering/ University of Baghdad
25/6/2020 14 | P a g e
2. A 1500 cm3 four stroke cycle CI engine operating at atmospheric
conditions 25°C and 100 kPa. Calorific Value of Fuel
42000(KJ/kg)Plot the relation between N-PB and N-ηb for the
following data:
Where: AFR = air fuel ratio
T = Torque (N.m)
PB = Break Power (kW)
N = Engine Speed (rpm)
QCV = Calorific Value of Fuel (KJ/kg)
Vs = Swept Volume (m3)
𝑚̇ 𝑎 = Air mass flow rate (kg/hr)
𝑚̇ 𝑓 = Fuel mass flow rate (kg/hr)
𝜌 𝑎= Air Density (kg/m3).
𝑇 𝑎 = Air Temperature (°C).
𝝆 𝒂 = 𝒑 𝒂 / 𝟎. 𝟐𝟖𝟕(𝑻 𝒂 + 𝟐𝟕𝟑)
𝒎̇ 𝒂 = )𝑵 / 𝟏𝟐𝟎( 𝝆 𝒂 𝑽 𝒔
𝒎̇ 𝒇 = 𝒎̇ 𝒂⁄𝑨𝑭𝑹
𝑷 𝑩 =𝟐𝝅𝑵𝑻 / 𝟔𝟎𝟎𝟎𝟎
𝜼 𝐛 = 𝑷 𝑩 × 𝟑𝟔𝟎𝟎 / 𝒎̇ 𝒇 × 𝑸 𝑪𝑽
Ans:-
Simple calculations;-
𝝆 𝒂 = 100000 / 𝟎. 𝟐𝟖𝟕(20 + 𝟐𝟕𝟑) =1170 kg/m^3
Vs=0.0015 m^3
Pa =100 kpa
1. 𝒎̇ 𝒂 = )2000 / 𝟏𝟐𝟎( 1170* 0.0015= 29.25 (kg/hr)
2. 𝒎̇ 𝒂 = )2500 / 𝟏𝟐𝟎( 1170* 0.0015= 36.5625 (kg/hr)
3. 𝒎̇ 𝒂 = )3000 / 𝟏𝟐𝟎( 1170*0.0015=43.875 (kg/hr)
4. 𝒎̇ 𝒂 = )3500 / 𝟏𝟐𝟎( 1170* 0.0015=51.1875 (kg/hr)
5. 𝒎̇ 𝒂 = )4000 / 𝟏𝟐𝟎( 1170* 0.0015=58.5 (kg/hr)
1. 𝒎̇ 𝒇 = 29.25⁄8= 3.65625 (kg/hr)
2. 𝒎̇ 𝒇 = 36.5625⁄7= 5.22321(kg/hr)
3. 𝒎̇ 𝒇 = 43.875⁄10= 4.3875 (kg/hr)
4. 𝒎̇ 𝒇 = 51.1875⁄16= 3.19921875 (kg/hr)
5. 𝒎̇ 𝒇 = 58.5⁄23= 2.543452(kg/hr)

15. Saif al-din ali Madhi
Department of Mechanical Engineering/ College of Engineering/ University of Baghdad
25/6/2020 15 | P a g e
𝑷𝑩 =𝟐𝝅*2000*8/ 𝟔𝟎𝟎𝟎𝟎 = 1.674666667 kW
𝑷𝑩 =𝟐𝝅*2500*9.2/ 𝟔𝟎𝟎𝟎𝟎 = 2.407333333 kW
𝑷𝑩 =𝟐𝝅*3000*10.5/𝟔𝟎𝟎𝟎𝟎 = 3.297 kW
𝑷𝑩 =𝟐𝝅*3500*11.6/𝟔𝟎𝟎𝟎𝟎 = 4.249466667 kW
𝑷𝑩 =𝟐𝝅*4000*10 / 𝟔𝟎𝟎𝟎𝟎 = 4.186666667 kW
𝜼 𝐛 = 1.674666667 × 𝟑𝟔𝟎𝟎 / 3.65625 × 42000 =4%
𝜼 𝐛 = 2.407333333 × 𝟑𝟔𝟎𝟎 / 5.22321× 42000 = 4%
𝜼 𝐛 = 3.297 × 𝟑𝟔𝟎𝟎 / 4.3875 × 42000 = 6%
𝜼 𝐛 = 4.249466667 × 𝟑𝟔𝟎𝟎 / 3.19921875 × 42000 = 11%
𝜼 𝐛 = 4.186666667 × 𝟑𝟔𝟎𝟎 / 2.543452× 42000 = 14%
N (
rpm)
T(
N.M)
AFR 𝒎̇ 𝒂 (kg/hr) 𝒎̇ 𝒇 (kg/hr) 𝑷𝑩 (kW) 𝜼𝐛
2000 8 8 29.25 3.65625 1.674666667 3.92595849
2500 9.2 7 36.5625 5.223214286 2.407333333 3.95049573
3000 10.5 10 43.875 4.3875 3.297 6.44102564
3500 11.6 16 51.1875 3.19921875 4.249466667 11.3852796
4000 10 23 58.5 2.543478261 4.186666667 14.1089133
We note that the relationship is direct
y = 0.0014x - 0.9567
R² = 0.9368
y = 0.0056x - 8.7181
R² = 0.9179
0
2
4
6
8
10
12
14
16
0 500 1000 1500 2000 2500 3000 3500 4000 4500
𝑷𝑩(kW)&𝜼𝐛
N rpm
Chart Title
𝑷𝑩 (kW) 𝜼𝐛 Linear (𝑷𝑩 (kW)) Linear (𝜼𝐛)