Er. Uttam Raj Timilsina(MSc.Engineering,IIT Roorkee) Professor of Agricultural Engineering,Agriculture and Forestry University (AFU), Rampur, Chitwan, Nepal uttamrajtimilsina@gmail.com *All Right Reserved** Uploaded and Shared by AgriYouthNepal

1. AEN-301,Farm Power and Machinery
• Internal Combustion Engine(Two
Lectures)
 Eengine types
 Components of IC engines and their
functions
 Principles of operation of two stroke
and four stroke cycle Diesel
andpetrol engines
 Systems in two wheel and fou
 cleaining, cooling and lubrication
systems
Prepared by
Er. Uttam Raj Timilsina(MSc.Engineering,IIT Roorkee)
Professor of Agricultural Engineering,,AFU

2. Engines
• External Combustion Engine: It is the engine in
which the fuel is burned outside the cylinder to
boil water and generate steam which was fed
into the top and bottom of cylinder through
sliding valves for the downward and then
upward movement of piston to rotate the
crankshaft.
 Examples of EC Engines are - steam traction
engines,railroad locomotives,steam
automobiles etc.
• Internal Combustion Engine: It is the engine in
which the fuel is burned and the power is
generated within a closed cylinder.All
common oil burning engines are the
examples.

3. History of IC engines(1892-1901)

4. Internal Combustion Engines

8. Internal Combustion Engines
Classification of IC Engines
1. Stationary or Automotivetypes.
2. Single or multiple cylinder types
3. Slow,Medium or High speed types: Slow speed:
below 350 rpm, Medium speed:350-1000 rpm,
High speed: Greater than 1000 rpm
4. Horizontal or vertical types
5. Two or four stroke cycle types
6. Spark ignition or compression ignition types or
Carburettor type(Petrol engine) or Diesel engine
7.

9. Components or parts of IC engines
• Cylinder Head
• Cylinder liner
• Engine Block
• Piston with piston Rings and piston Pin
• Connecting Rod
• Bearings
• Crankcase
• Crankshaft,Camshaft,Timing gears,
• Engine Valves with valves springs,push rod
• Fly wheel
• Gaskets,etc

10. Component of IC Engines and
their functions

13. Two stroke single cylinder Diesel
engine

14. Four stroke single cylinder petrol
Engine

15. Multi cylinder diesel Engine

16. Principle of operation of four stroke
cycle engine
• Intake stroke: Downward movement of piston.Suction of air in
case of diesel engine takes place and suction of air plus fuel
mixed from carburettor takes place in case of petrol engine
• Compression stroke:Upward movement of
piston.compression takes place under a high pressure of 105
kg per square cm or above
• Power stroke: Downward movement of piston.Burning or
explosion of fuel takes place pussing down the piston
• Exhaust stroke: Upward movement of piston with
Exahaustion of burned air out from combustion chamber

17. Four stroke petrol engine

18. Four stroke petrol engine

19. Multi cylinder four stroke Engines

22. Two stroke cycle Engine,principle of
operation

23. Live action of multicylinder petrol engine

24. Engine Terminology
• Stroke-Bore-Ratio: It is expressed as L/D ratio where
L=length of the piston stroke(mm)
D=Diameter of the Cylinder(mm)
This ratio for Tractor Engine is about 1.25 and it varies between
1.00-1.45
• Compression Ratio: Compression Ratio of an engine is expressed as
the total cylinder volume at BDC divided by the clearance volume or
compressed volume at TDC
r=vt/vc,where r=compression ratio, vt=total cylinder
volume(c.c),vc=clearance volume(c.c)
In petrol engine it ranges between 4:1 and 8:1 whereas
compression ratio of diesel engines are in the order of 14:1 and
20:1.Efficiency increase with higher compression ratio in petrol
engine.

25. • Piston Displacement: It is the volume
displaced by the piston during one stroke
usually expressed in cubic centimeter and also
known as Swept volume and can be computed
as Pd=A*L,where Pd=piston
volume(cubic.cm),A=piston
area(sq.cm),L=length of the piston travel or
piston stroke(cm)

26. Engine Terminology contd…
• Displacement volume:The displacement volume of an engine is the total
swept volume of all the pistons during power stroke occuring in a period
of one minute.It may be expressed as:
Vd=A*L*n
Where, Vd=Displacement volume,c.c/min
A=piston area(sq.cm)
L=piston stroke(cm)
n=Number of power stroke /min of the all cylinders
• Piston Speed :The piston speed of an engine is the total travel of the
piston in a cylinder during a period of one minute and expressed as:
Sp=2LN,where,Sp=piston speed,(metre/minute)
L=Piston stroke(metre),N=Engine rpm
Piston speed of the high speed Tractor Engine ranges between 300-500
metres/min
• Horse Power:It is the rate of doing work equivalent to 75 kg metre/sce

27. Contd…
• Engine Cycle: A cycle consist of the events taking place in each
cylinder of an engine between two successive explosions or
two power strokes in that cylinder
• Indicated Mean Effective Pressure(IMEP): It is an average net
pressure in kg/sq.cm on the piston during the power stroke
only
• Indicated Horse Power(IHP): It is the total horse power
developed by all cylinders and received by pistons disregarding
friction and losses within the engine.It can be calculated as
IHP=P*L*A*n/75*60
where,P=indicated mean effective pressure(kg/sq.cm)
L=Piston stroke(cm),A=piston area(sq.cm),n=Total
number of power stroke/min for all cylinders

28. Terminology contd…
• Brake Horse Power: It is the horse power available at the
crankshaft and measured by a suitable dynamometer.
• Mechanical Efficiency: It is the ratio of the brake horse
power to the indicated horse power and is expressed as:
Mechanical Efficiency=BHP/IHP*100
• Specific Fuel Consumption: It is the quantity of fuel
consumed by an oil engine on the basis of per hp- hour.It is
expressed as kg per metric hp-hour
• Thermal Efficiency: It is the ratio of the horse power output
of an engine to the fuel horse power

29. Comparison between Two stroke and four
stroke cycle Engines
Two Stroke Engine
• One power impulse for every tow
stroke of the piston
• For the same size of engine it gives
twice the power of four stroke engine
• Size of the fly wheel is comparatively
smaller
• Thermal efficiency is low
• Weight per HP is low
• Only high speed type engines are
available
• Engine can be operated in both
direction(clockwise, and anti
clockwise)
• Valves are not required for intake and
exhaust operation.
Four Stroke Engine
• One power impulse for every four stroke of
the piston
• For the same size of engine it gives only
half the power of two stroke engine.
• Size of the fly wheel is comparatively larger
• Thermal efficiency is higher
• Weight per HP is comparatively high
• All types.low, medium and high speed
engines are available
• Engine can be operated in only one
direction
• Valves are required to let the gases in or out

30. Comparison between Diesel and Petrol Engine
Diesel Engine
• Diesel fuels are used.
• Filtered air is taken during intake
stroke
• Compression ignition takes place
with injected fule
• Air fuel ratio is not constant
because of constant air inlet
• Compression ratio varies
between 14-20:1 with high
compression pressure and
temperature
• Specific fuel consumption is
about 0.2 kg /bhp/hr
• 4.5 litres of fuel produce 20 hp-hr
Carburettor(Petrol)Engine
• Petrol,Kerosene are used
• Mixture of air and fuel is taken
during intake stroke
• Spark ignition with electric spark
plug takes place with compressed
mixture
• Air fuel ratio is constant as 15:1
• Compression ratio varies between
4.5-8:1 with low compression
pressure and temperature
• Specific fuel consumption is
about 0.29kg/bhp/hr
• 4.5 litres of fuel produce 12hp-hr

31. Comparison contd…..
Diesel Engine
• Thermal Efficiency varies
between 32-38 %
• Diesel engine develops more
torque when it is heavely
loaded
• It runs at lower combustion
gas temperature on part load
• Engine weight per horse
power is high
• Initial cost is high
• Operating cost is low
Petrol Engine
• Thermal Efficiency varies
between 25-32 %
• This characteristic is not
present in petrol engine
• Combustion gas temperature
is slightly higher under part
load
• Engine weight per horse
power is comparatively low
• Initial cost is low
• Operating cost is
comparatively high

32. Systems in Tractor Engines
• Fuel Supply and Circulation System
• Air Cleaning and supplySystem
• Lubrication System
• Engine cooling System
• Ignition System-compression ignition as well
spark ignition system
• Electrical System
• Engine governing System for constant engine
speed under varying loads
• Power Transmission System

33. External combustion Steam engine
tractor

34. Modern Farm Tractor

35. Power tiller

36. Farm Tractor

37. Live action of multicylinder petrol engine

38. Engine

39. Tractor engine

40. Big and multi use Tractoe

41. Tractor Engine

42. Two wheel Tractor

43. Fram Tractor

44. Fuel Supply and circulation System
• Components and their function of Fuel supply and circulation
system
• Fuel Tank
• Fuel supply pipes
• Fuel Filters
• Carburettor only in case of petrol engine to mix the air and fuel in a
predetermined air fuel ratio of 15:1.
• Fuel feed pump or fuel supply pump
• Priming pump-hand operated pump to take air out from the fuel
supply system by bleeding action with air bubbles
• Pressure pump with pressure gauge
• Fuel Injection pump
• Fuel control,regulation valve or check valve,bleeding valve etc
• Fuel injection nozzle or fuel injector.

45. Fuel supply System contd…
• Fuel Tank-
 Used to store the fuel in a safety manner
Protect the stored fuel from dirt, water,or any
other unlike materials.
Should be cleaned throughly after every 200
working hours by draining out all the fuel.
Should be filled with fuel after days works and
keep air tight

46. Contd…
• Fuel pipes
 Conncet fuel tank with fuel filters,fuel pump,fuel injection
pump and injection nozzles to supply and circulate fuel in
case of single cylinder as well as multi cylinder engines
• Fuel feed or fuel supply pump.
 Lies between primary filter and fuel injection pump
 Supply and circulate fuel from fuel tank via primary filter to
fuel injection pump at a lower pressure of 2 kg/sq.cm
 Plunger typed- driven by camshaft as connected by push
rod with camshaft
 When engine starts it gets power to self working condition

47. Contd..
• Fuel Filters-
 Primary fuel filter- located between fuel tank and fuei supply pump
 Secondary fuel filters-located between fuel pump and fuel injection
pump
 Consists of fine graded filter elements made of special treated
paper of different qualities,filter bowl,drain plug ,air bleeding
serews,inlet outlet points for pipe fiting etc
 Clean the fuel by filtering action not allowing the derts,vapors,
particles air bubbles etc of size greater than 0.25-1mm dia (nozzle
hole size) into the system
 Filter the dirt of size of 5-2 micron not allowing to fuel injection
pump
 Replace the filter and filter elements after each 125 working hour

48. Contd…
• Fuel Injection Pump
Connected to engine camshaft for auto
functioning when engine start
Supply the fuel to the injection nozzle with
predetermined time under the pressure of 126-
175 kg/sq.cm or more
Circulate the fuel equally to all nozzle of multi
cylinder engines as well as single cylinder engines
Re-circulate the excess fuel not utilized by
injection nozzle to fuel tank.

49. Contd…
• Fuel injection nozzles or fuel injectors
 Located at engine head or cylinder head
 Spray the fuel with high pressure into combustion chamber
 Multiple nozzle hole are more effective than single one to
spray fuel
 Leak off pipe from injectors access the overflow fule to fuel
tank
 Fuel is sprayed in predetermined time and pressure with
compression stroke.
 Nozzle valve is active to regulate the fuel spray to
combustion chamber

50. Air cleaning System
• Pre-cleaner,Air cleaner
Air cleaners in all farm tractors are equipped with
pre cleaners as air intake system to remove larger
particles of dirt and foreign materials like
straw,chaff,leaves etc
Averege tractor uses 9000 liter of air for each liter
of diesel consumed under normal condition
• Two types of air cleaner are in use
Oil soaked element type-used in crankcase
ventilation system and in small stationary engine
where less dusty condition is existed

51. Air cleaning contd…
 Oil bath type-used in most commonly in farm tractors.
 Consist of oil bowl,filter screens,precleaner,air inlet
and out let pipe system
 Dusty air is allowed through the center pipe dipped
into oil to pass the air from oil as an oil bath then
allow upward to filtering element where oil is entraped
by filtering element ,drops back to oil bowl and fresh
air goes to the engine.
 Oil might need a change between 8-60 working hour
when dust sedimentation exceed 5mm at the bottom
of the bowl

52. Lubricating Systems
• Lubraction is the oiling and greasing of different
moving parts and systems of IC engines or tractors
• Consist of oil chamber,oil pump,oil filter,pressure
gauge, regulating valve,bypass relief valves,drain plug
etc
• Essential for all moving parts of tractor engine to
performs the following functions
 Reduce wear and tear of moving parts
 Reduce power needed to overcome frictional
resistances between two relatively moving parts such
as shaft bearings gears,etc
 Removes or absorbs heat from piston and other parts

53. Lubrication contd..
• It is accomplished by two systems
 Splash system-lubricating oil is splashed or
sprayed in moving parts periodically with self
functioning when engine starts
Force feed system by oil pump-oil is supplied
under pressure to reach to all moving parts
Gear pump driven by camshaft forces engine
oil from crankcase(oil chamber) to all moving
parts automatically when engine start to run

54. Contd..
• The daily and periodic lubrication of all system is
explained in the Operator’s Mannual of the
Tractors to ensure trouble free operation and
long life of tractor, given by Tractor
Manufacturers
• Recommended grade of lubricants like
grease,mobil,gear oil etc is essential to use as
given in operational mannual
• Grade of lubricants and changing of lubricants-
mobile, Castrol oil ,grease is also periodic as given
in operational mannual by the manufracturers.

55. Showing lubrication system

57. Cooling System
• As it is the requirement that engine should be run at an
optimum temperature to ensure the best performance
• The purpose of cooling system is to maintain the correct
engine operating temperature and dissipate surplus heat
resulting from cumbustion of fuel in engine cylinder
• The cooling system of IC engine should maintain the engine
temperature at 71-80 degree C for petrol engine and 88-90
degree C for diesel engine
• Types of cooling system
 Water cooling system-used for bigger engine
 Air cooling system-used for smaller engine

58. Cooling system….
• Types of water cooling system
 Thermosiphon cooling system-
-Used in tractors and stationary engines
-Consists of a radiator,water jacket,fan, temperature gauge and
hose pipe connection
-It works on the principle that heated air surrounding the engine
cylinder gets lighter in weight and rises up
-Hot water goes to radiator where it passes through tubes
surrended by air
-Since water jacket and radiator are connected at the top and
bottom a circulation of water takes place.
-A fan driven by a pully mounted on crankshaft is located between
radiator and engine sucks air through radiator tub thus cooling
the radiator water

59. Cooling system contd…
• Forced circulation cooling system/pressurized
cooling system
Consist of radiator,fan,fan belt,water jacket,water
pump,thermostat,temperature gauge and hose
pipe to complete the cooling system
Water is pumped to radiator where it loose heat
by radiation to the air outside
Water circulation between engine chamber and
radiater is controlled by thermostat valve placed
at cylinder head to maintain the temperature of
74-80 degree Centigrate

61. Live action of multicylinder petrol engine