Internal Combustion Engine

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 byEr. Uttam Raj Timilsina(MSc.Engineering,IIT Roorkee)

Professor of Agricultural Engineering,,AFU

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,steamautomobiles etc.

• Internal Combustion Engine: It is the engine in which the fuel is burned and the power is generated within a closed cylinder.Allcommon oil burning engines are the examples.

History of IC engines(1892-1901)

Internal Combustion Engines

Internal Combustion EnginesClassification 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 orCarburettor type(Petrol engine) or Diesel engine

7.

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

Component of IC Engines and their functions

Two stroke single cylinder Diesel engine

Four stroke single cylinder petrol Engine

Multi cylinder diesel Engine

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

Four stroke petrol engine

Four stroke petrol engine

Multi cylinder four stroke Engines

Two stroke cycle Engine,principle of operation

Live action of multicylinder petrol engine

Engine Terminology

• Stroke-Bore-Ratio: It is expressed as L/D ratio whereL=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 TDCr=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.

• 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)

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 rpmPiston 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

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

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

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

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

Comparison contd…..

Diesel Engine

• Thermal Efficiency varies between 32-38 %

• Diesel engine develops more torque when it is heavelyloaded

• 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

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

External combustion Steam engine tractor

Modern Farm Tractor

Power tiller

Farm Tractor

Live action of multicylinder petrol engine

Engine

Tractor engine

Big and multi use Tractoe

Tractor Engine

Two wheel Tractor

Fram Tractor

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.

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

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

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

Contd…

• Fuel Injection PumpConnected to engine camshaft for auto

functioning when engine startSupply 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.

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

Air cleaning System

• Pre-cleaner,Air cleanerAir 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 useOil soaked element type-used in crankcase

ventilation system and in small stationary engine where less dusty condition is existed

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 entrapedby 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

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,pressuregauge, 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

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

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.

Showing lubrication system

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

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

Cooling system contd…

• Forced circulation cooling system/pressurized cooling system

Consist of radiator,fan,fan belt,water jacket,waterpump,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

Live action of multicylinder petrol engine