When engines are run for automotive purpose,a simple carburettor can't supply the correct air-fuel mixture for all conditions of speeds and loads at which engine required to run.To correct mixture strength according to demand of engine,some compensation methods are used in carburettor for providing additional fuel or reducing the fuel.
Following are the compensation methods adopted in simple carburettor.
01)Extra Air Valve Compensation:-
As throttle valve is opened more and more,an extra air valve,which is mounted on carburettor,opens against the force of a spring and supplies extra air to mixture.Thus throughout the economy range,the strength of mixture kept reasonably constant.
02)Restricted Air Bleed Compensation:-
A jet tube,which has opening at its periphery,is provided with carburettor in this type of compensation.A restricted air bleed opening connects main air passage to the outer enclosure of the jet tube.At starting time and at slow speed of engine,there is small pressure due to the effect of viscosity and surface tension of the fuel,the more quantity fuel flows into the venturi gives a rich mixture when throttle valve opens more at high speed.The effect of viscosity considerably diminishes and there is a higher pressure drop in the venturi due to which more fuel is to be drawn and sprayed by the nozzle but at this stage the air bubbles starts bleeding through the jet tube opening,making a lean mixture.
03)Compensating Jet Compensation:-
This method consists of main jet and compensating jet.The main jet is directly connected to the float chamber while compensating jet is connected to the float chamber through a tube,which top end is open to atmosphere.Both the jet supply fuel in venturi when throttle valve is slightly opened .As the throttle valve is gradually opened the fuel supply from the main jet increases but that from compensating jet decreases due to falling level of fuel in the tube,as atmospheric pressure acts on the tube.Some air is drawn in,through this tube,thus the richness of the mixture decreases.This method is also called as "Unrestricted air bleed compensation".
04)Economiser Needle In Metering Jet:-
The flow of fuel is restricted by changing the area of the metering nozzle supplying the fuel from the float chamber to the main jet.The area is changed by means of a needle operated with linkage from accelerator pedal.
Day by day,technology is changing and modifications are done frequently for proper functioning of the device,there by increasing the overall results of the automobile engines.
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Various Parts And Its Function In Internal Combustion Engine.
Working Principle Of Simple Carburettor Used In Petrol Engine.
Valves And Valve Mechanism used in Internal Combustion Engine.
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Various Parts And Its Function In Internal Combustion Engine.
Internal combustion engines are made from various parts.Each part has its own location and function for proper working of engine.Some important parts and its function is as described below.
01) Cylinder Block:-
Function- In the bore of cylinder the fresh charge of air-fuel mixture is ignited,compressed by piston and expanded to give power to piston.
02) Cylinder Head:-
Function-It carries inlet and exhaust valve.Fresh charge is admitted through inlet valve and burnt gases are exhausted from exhaust valve.In case of petrol engine,a spark plug and in case of diesel engine,a injector is also mounted on cylinder head.
03) Piston:-
Function-During suction stroke,it sucks the fresh charge of air-fuel mixture through inlet valve and compresses during the compression stroke inside the cylinder.This way piston receives power from the expanding gases after ignition in cylinder.Also forces the burnt exhaust gases out of the cylinder through exhaust valve.
04) Piston Rings:-
Function-It prevents the compressed charge of fuel-air mixture from leaking to the other side of the piston.Oil rings,is used for removing lubricating oil from the cylinder after lubrication.This ring prevents the excess oil to mix with charge.
05) Connecting Rod:-
Function-It changes the reciprocating motion of piston into rotary motion at crankshaft.This way connecting rod transmits the power produced at piston to crankshaft.
06) Gudgeon Pin:-
Function-Connects the piston with small end of connecting rod.
07) Crank Pin:-
Function-hand over the power and motion to the crank shaft which come from piston through connecting rod.
08) Crank Shaft:-
Function-Receives oscillating motion from connecting rod and gives a rotary motion to the main shaft.It also drives the camshaft which actuate the valves of the engine.
09) Cam Shaft:-
Function-It takes driving force from crankshaft through gear train or chain and operates the inlet valve as well as exhaust valve with the help of cam followers,push rod and rocker arms.
10) Inlet Valve & Exhaust Valve:-
Function-Inlet valve allow the fresh charge of air-fuel mixture to enter the cylinder bore.Exhaust valve permits the burnt gases to escape from the cylinder bore at proper timing.
11) Governor:-
Function-It controls the speed of engine at a different load by regulating fuel supply in diesel engine.In petrol engine,supplying the mixture of air-petrol and controlling the speed at various load condition.
12) Carburettor:-
Function-It converts petrol in fine spray and mixes with air in proper ratio as per requirement of the engine.
13) Fuel Pump:-
Function-This device supply the petrol to the carburettor sucking from the fuel tank.
14) Spark Plug:-
Function-This device is used in petrol engine only and ignite the charge of fuel for combustion.
15) Fuel Injector:-
Function-This device is used in diesel engine only and delivers fuel in fine spray under pressure.
I hope,above information will help you something about your vehicle's engine.
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Working Principle Of Simple Carburettor Used In Petrol Engine.
Valves And Valve Mechanism used in Internal Combustion Engine.
01) Cylinder Block:-
Function- In the bore of cylinder the fresh charge of air-fuel mixture is ignited,compressed by piston and expanded to give power to piston.
02) Cylinder Head:-
Function-It carries inlet and exhaust valve.Fresh charge is admitted through inlet valve and burnt gases are exhausted from exhaust valve.In case of petrol engine,a spark plug and in case of diesel engine,a injector is also mounted on cylinder head.
03) Piston:-
Function-During suction stroke,it sucks the fresh charge of air-fuel mixture through inlet valve and compresses during the compression stroke inside the cylinder.This way piston receives power from the expanding gases after ignition in cylinder.Also forces the burnt exhaust gases out of the cylinder through exhaust valve.
04) Piston Rings:-
Function-It prevents the compressed charge of fuel-air mixture from leaking to the other side of the piston.Oil rings,is used for removing lubricating oil from the cylinder after lubrication.This ring prevents the excess oil to mix with charge.
05) Connecting Rod:-
Function-It changes the reciprocating motion of piston into rotary motion at crankshaft.This way connecting rod transmits the power produced at piston to crankshaft.
06) Gudgeon Pin:-
Function-Connects the piston with small end of connecting rod.
07) Crank Pin:-
Function-hand over the power and motion to the crank shaft which come from piston through connecting rod.
08) Crank Shaft:-
Function-Receives oscillating motion from connecting rod and gives a rotary motion to the main shaft.It also drives the camshaft which actuate the valves of the engine.
09) Cam Shaft:-
Function-It takes driving force from crankshaft through gear train or chain and operates the inlet valve as well as exhaust valve with the help of cam followers,push rod and rocker arms.
10) Inlet Valve & Exhaust Valve:-
Function-Inlet valve allow the fresh charge of air-fuel mixture to enter the cylinder bore.Exhaust valve permits the burnt gases to escape from the cylinder bore at proper timing.
11) Governor:-
Function-It controls the speed of engine at a different load by regulating fuel supply in diesel engine.In petrol engine,supplying the mixture of air-petrol and controlling the speed at various load condition.
12) Carburettor:-
Function-It converts petrol in fine spray and mixes with air in proper ratio as per requirement of the engine.
13) Fuel Pump:-
Function-This device supply the petrol to the carburettor sucking from the fuel tank.
14) Spark Plug:-
Function-This device is used in petrol engine only and ignite the charge of fuel for combustion.
15) Fuel Injector:-
Function-This device is used in diesel engine only and delivers fuel in fine spray under pressure.
I hope,above information will help you something about your vehicle's engine.
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Working Principle Of Simple Carburettor Used In Petrol Engine.
Valves And Valve Mechanism used in Internal Combustion Engine.
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Working Principle Of Simple Carburettor Used In Petrol Engine.
This is most important to supply proper air-fuel ratio in inlet manifold of the internal combustion engine.The process of breaking up the fuel into minute particles and mixing it with air is known as carburation.
As internal combustion engine have very low compression ratio and which use highly volatile liquid fuel such as petrol,paraffin etc.,the carburation process is must required.
In carburettor,the fuel is completely broken into the minute particles,vaporized and mixed with the air in a proper ratio.The homogeneous mixture of fuel and air thus obtained,is supplied to the engine cylinder during the suction stroke of engine.
Carburettors:-
This device is used in petrol or similar liquid fuel engines by means of which the fuel mixed with air is supplied into the induction manifold of the engine.The carburettor controls the required quantity of fuel and breaks it up into minute globules for being mixed with the correct quantity of air.
The main purpose of carburettor is to supply the required quantity of petrol and air mixture,of the correct strength as per requirement of load conditions of the engine.The ratio should not be more than 20 : 1 and not less than 8 : 1.The ideal ratio is 15 : 1
Construction and working of simple carburettor:-
Simple carburettor consist of a venturi and a fuel jet located therein.For maintaining the level of fuel in the jet,a float chamber is usually required.A throttle valve in the form of a flat circular metal disc mounted on spindle is provided for controlling the flow of air-fuel mixture to the induction manifold.A rotary type valve also can be used instead of disc type.
The level of fuel is just kept slightly below the top of the jet to prevent the leakage when not in operation.Usually 1.5 mm difference is kept between the top of the jet and the surface of the fuel in float chamber.A needle valve controls the passage of fuel from the fuel pump,when the air begins to flow past the jet,a low pressure zone is created in the venturi because of the increased velocity of air.
The fuel begins to rise because of the difference in the air pressure on the fuel which is equal to the pressure of the atmosphere and on the fuel in the jet at the venturi and issue out from the jet in the form of fine spray.A minute petrol particles present a large surface area being exposed to the air stream.The fuel is not completely vaporized in carburettor and some globules of fuel still enter the induction manifold and are vaporized during the compression stroke in engine cylinder.A chock valve controls the flow of air into the carburettor.A gas tight connection is provided between the carburettor and the induction manifold.
When two concentric venturies are provided,the discharge end of the inner venturi called "Primary Venturi",which lies just at the throat of the main venturi.A higher velocity of air which aids in the atomization of the fuel,is obtained at the throat of primary venturi due to lower pressure comparing to main venturi.
The main advantages of multiple venturies are,these keep the fuel away from the carburettor walls and there is considerable reduction in fuel consumption.
The Simple Carburettor may be of following three types.
01)Updraft Type:-In this,the air enters the carburettor at the bottom and leaves at the top.
02)Downdraft Type:-In this,air enters the carburettor at the top and leaves at the bottom.This used most passenger cars because it can be installed at a higher level in the engine which makes it more accessible for the purpose of inspection and repair.
03)Side draft Type:-It has more width and mounting of oil bath air filter is clumsy.
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Air-Fuel Ratio In Internal Combustion Engine.
Fuel supply System In Internal Combustion Engine.
Valves And Valve Mechanism used in Internal Combustion Engine.
As internal combustion engine have very low compression ratio and which use highly volatile liquid fuel such as petrol,paraffin etc.,the carburation process is must required.
In carburettor,the fuel is completely broken into the minute particles,vaporized and mixed with the air in a proper ratio.The homogeneous mixture of fuel and air thus obtained,is supplied to the engine cylinder during the suction stroke of engine.
Carburettors:-
This device is used in petrol or similar liquid fuel engines by means of which the fuel mixed with air is supplied into the induction manifold of the engine.The carburettor controls the required quantity of fuel and breaks it up into minute globules for being mixed with the correct quantity of air.
The main purpose of carburettor is to supply the required quantity of petrol and air mixture,of the correct strength as per requirement of load conditions of the engine.The ratio should not be more than 20 : 1 and not less than 8 : 1.The ideal ratio is 15 : 1
Construction and working of simple carburettor:-
Simple carburettor consist of a venturi and a fuel jet located therein.For maintaining the level of fuel in the jet,a float chamber is usually required.A throttle valve in the form of a flat circular metal disc mounted on spindle is provided for controlling the flow of air-fuel mixture to the induction manifold.A rotary type valve also can be used instead of disc type.
The level of fuel is just kept slightly below the top of the jet to prevent the leakage when not in operation.Usually 1.5 mm difference is kept between the top of the jet and the surface of the fuel in float chamber.A needle valve controls the passage of fuel from the fuel pump,when the air begins to flow past the jet,a low pressure zone is created in the venturi because of the increased velocity of air.
The fuel begins to rise because of the difference in the air pressure on the fuel which is equal to the pressure of the atmosphere and on the fuel in the jet at the venturi and issue out from the jet in the form of fine spray.A minute petrol particles present a large surface area being exposed to the air stream.The fuel is not completely vaporized in carburettor and some globules of fuel still enter the induction manifold and are vaporized during the compression stroke in engine cylinder.A chock valve controls the flow of air into the carburettor.A gas tight connection is provided between the carburettor and the induction manifold.
When two concentric venturies are provided,the discharge end of the inner venturi called "Primary Venturi",which lies just at the throat of the main venturi.A higher velocity of air which aids in the atomization of the fuel,is obtained at the throat of primary venturi due to lower pressure comparing to main venturi.
The main advantages of multiple venturies are,these keep the fuel away from the carburettor walls and there is considerable reduction in fuel consumption.
The Simple Carburettor may be of following three types.
01)Updraft Type:-In this,the air enters the carburettor at the bottom and leaves at the top.
02)Downdraft Type:-In this,air enters the carburettor at the top and leaves at the bottom.This used most passenger cars because it can be installed at a higher level in the engine which makes it more accessible for the purpose of inspection and repair.
03)Side draft Type:-It has more width and mounting of oil bath air filter is clumsy.
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Air-Fuel Ratio In Internal Combustion Engine.
Fuel supply System In Internal Combustion Engine.
Valves And Valve Mechanism used in Internal Combustion Engine.
Air-Fuel Ratio In Internal Combustion Engine.
In internal combustion engine,atmospheric air is essentially required to burn the fuel.The Oxygen in air,helps for proper burning of fuel.To obtain excellent combustion result from fuel,the air and the fuel must be mixed in proper ratio.For complete combustion,the air-fuel ratio is approximately 15 : 1 by weight.This ratio is known as Chemically correct air-fuel ratio.This ideal ration in any internal combustion engine.
However,the air-fuel ratio can be range from 20 : 1 to 8 : 1,in this range also combustion of fuel can occur.Any ratio outside of this range is either too rich or too lean to sustain flame propagation.
As per requirement of engine,the carburettor provide an air-fuel ratio,which must be within combustion range.Engine is cold at the time of starting so,very rich mixture is required.Rich mixture is also required at time of idling and producing maximum power.During the normal running,a comparatively lean mixture can be used.
For petrol engine,different air-fuel ratios are required under various conditions of load.These are as discussed below.
01)Air-Fuel Ratio For Starting:-
Very rich mixture ( 10 : 1 ) is required at starting of engine.During starting very small amount of fuel is vaporises and rest of it stay in the liquid state so as to give an ignitable mixture.
02)Air-Fuel Ratio For Idling:-
An idling,engine demands a rich mixture,which can be made leaner as the throttle is gradually opened.During idling,the pressure in the inlet manifold is about 20 to 25% of atmospheric pressure.At suction stroke,inlet valve opens and the product of combustion trapped in the clearance volume,expands in the inlet manifold.Latter when the piston moves downwards,the gases along with the fresh charges go into the cylinder.A rich mixture must be supplied during idling,to counteract the tendency of dilution and to get an ignitable mixture.
03)Air-Fuel Ratio For Medium Load:-
Most of the time,engine is running in medium load condition,therefore,it is desirable that the running should be most economical in this condition.So a lean mixture can be supplied,as engine has low fuel consumption at medium load.For multi cylinder engine,slightly more fuel is required due to maldistribution of fuel.
04)Air-Fuel Ratio For Maximum Power Range:-
When maximum power is required,the engine must be supplied with rich mixture as the economy is of no consideration.As the engine enters in the power range,the spark must be retarded otherwise knocking would occur.A lean mixture burns at latter part of working stroke.As the exhaust valve expose to high temperature gases and have very less time to cool down.Moreover,the excess air in the lean mixture may cause an oxidising action on the hot exhaust valve and leads to failure.
05)Air-Fuel Ratio For Acceleration:-
Even during normal running,sometimes more power is required for a short period such as to accelerate the vehicle for overtaking etc.During this period rich mixture is required.
I hope,this will help you to understand something about combustion of fuel at different running conditions of the engine.
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Fuel supply System In Internal Combustion Engine.
Valves And Valve Mechanism used in Internal Combustion Engine.
However,the air-fuel ratio can be range from 20 : 1 to 8 : 1,in this range also combustion of fuel can occur.Any ratio outside of this range is either too rich or too lean to sustain flame propagation.
As per requirement of engine,the carburettor provide an air-fuel ratio,which must be within combustion range.Engine is cold at the time of starting so,very rich mixture is required.Rich mixture is also required at time of idling and producing maximum power.During the normal running,a comparatively lean mixture can be used.
For petrol engine,different air-fuel ratios are required under various conditions of load.These are as discussed below.
01)Air-Fuel Ratio For Starting:-
Very rich mixture ( 10 : 1 ) is required at starting of engine.During starting very small amount of fuel is vaporises and rest of it stay in the liquid state so as to give an ignitable mixture.
02)Air-Fuel Ratio For Idling:-
An idling,engine demands a rich mixture,which can be made leaner as the throttle is gradually opened.During idling,the pressure in the inlet manifold is about 20 to 25% of atmospheric pressure.At suction stroke,inlet valve opens and the product of combustion trapped in the clearance volume,expands in the inlet manifold.Latter when the piston moves downwards,the gases along with the fresh charges go into the cylinder.A rich mixture must be supplied during idling,to counteract the tendency of dilution and to get an ignitable mixture.
03)Air-Fuel Ratio For Medium Load:-
Most of the time,engine is running in medium load condition,therefore,it is desirable that the running should be most economical in this condition.So a lean mixture can be supplied,as engine has low fuel consumption at medium load.For multi cylinder engine,slightly more fuel is required due to maldistribution of fuel.
04)Air-Fuel Ratio For Maximum Power Range:-
When maximum power is required,the engine must be supplied with rich mixture as the economy is of no consideration.As the engine enters in the power range,the spark must be retarded otherwise knocking would occur.A lean mixture burns at latter part of working stroke.As the exhaust valve expose to high temperature gases and have very less time to cool down.Moreover,the excess air in the lean mixture may cause an oxidising action on the hot exhaust valve and leads to failure.
05)Air-Fuel Ratio For Acceleration:-
Even during normal running,sometimes more power is required for a short period such as to accelerate the vehicle for overtaking etc.During this period rich mixture is required.
I hope,this will help you to understand something about combustion of fuel at different running conditions of the engine.
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Fuel supply System In Internal Combustion Engine.
Valves And Valve Mechanism used in Internal Combustion Engine.
Saturday
Fuel supply System In Internal Combustion Engine.
An internal combustion engine is operated by liquid or gaseous fuel.Actually gaseous fuel is most useful due to high octane rating,less deposit trouble and clean operation but the use of this type of fuel is mostly restricted to those areas where gas is available.It is also quite difficult to carry gas for automobile purpose.However in many metro cities compressed natural gas (CNG) is available and many vehicles are running on it.
Still today liquid fuels,obtained from petroleum (Crude Oil) are used to the largest extent primarily because large quantities of energy per unit volume and the ease in handling,storing and transportation.This type of fuel has some disadvantages as like,vaporisation,atomized or at least partly vaporised during the process of mixing.
What is the fuel supply system in petrol engine?
This system mainly consists of below parts,
01) Fuel Storage Tank
02) Fuel Pump
03) Fuel Filter
04) Carburettor
05) Inlet manifold
06) Inlet Valve
The fuel can be supplied to the engine under gravity or under pressure.
In gravity system,the fuel flows to the engine under gravitational force as the fuel storage tank is placed at a higher level than cylinder head.In this system fuel pump is not required.
In pressure system,the fuel from the fuel tank is forced by the fuel pump through the filter to the carburettor.In this case,the fuel tank is placed at lower level than the engine head and some times away from the engine.For example,motor cars,trucks etc.By keeping the fuel tank away from the hot engine,we can avoid the chances of catching fire in the event of an accident.
In a fuel system for a petrol engine,the fuel storage tank is located well below the carburettor.The fuel is supplied by the fuel pump to the carburettor through the fuel filter which removes the dirt and other foreign particles from the petrol.This system is extensively used for motor cars.
Description of some parts used in petrol engine.
01)Fuel Pump:-
A diaphragm type fuel pump is used in petrol engines as there is no need of extra high pressure of fuel.This fuel pump is extensively used to pump the fuel from fuel tank to the carburettor in the automotive engines.A flexible diaphragm is moved down against the force of the diaphragm spring by the diaphragm lever and the operating arm which is actuated by the camshaft eccentrically.
The pressure falls in the pump chamber and so the fuel from the fuel tank flows through the fuel inlet valve.Fuel inlet valve closes at the return stroke as diaphragm spring forces the diaphragm upwards,same time fuel outlet valve opens and thus the fuel starts flowing from the pump to the carburettor.
02)Fuel Filter:-
To get rid of unwanted dirt,filters are used.A filter used to clean the air is known as air filter,to clean fuel,is known as fuel filter,to clean lubricating oil,is known as oil filter.In filters,paper elements,cloth elements,felt elements and the combination of felt and cloth elements are used.Basically there are two types of fuel filters used
a) Preliminary fuel filter
b) Secondary fuel filter.
03)Carburettor:-
This is the device which mixes the fuel with air and supply this mixture to induction manifold of the engine.The carburettor controls the required quantity of fuel and breaks up into minute globules for being mixed with the correct quantity of air.Types of carburettor are
a) Zenith carburettor
b) Solex carburettor
c) Amal carburettor.
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Still today liquid fuels,obtained from petroleum (Crude Oil) are used to the largest extent primarily because large quantities of energy per unit volume and the ease in handling,storing and transportation.This type of fuel has some disadvantages as like,vaporisation,atomized or at least partly vaporised during the process of mixing.
What is the fuel supply system in petrol engine?
This system mainly consists of below parts,
01) Fuel Storage Tank
02) Fuel Pump
03) Fuel Filter
04) Carburettor
05) Inlet manifold
06) Inlet Valve
The fuel can be supplied to the engine under gravity or under pressure.
In gravity system,the fuel flows to the engine under gravitational force as the fuel storage tank is placed at a higher level than cylinder head.In this system fuel pump is not required.
In pressure system,the fuel from the fuel tank is forced by the fuel pump through the filter to the carburettor.In this case,the fuel tank is placed at lower level than the engine head and some times away from the engine.For example,motor cars,trucks etc.By keeping the fuel tank away from the hot engine,we can avoid the chances of catching fire in the event of an accident.
In a fuel system for a petrol engine,the fuel storage tank is located well below the carburettor.The fuel is supplied by the fuel pump to the carburettor through the fuel filter which removes the dirt and other foreign particles from the petrol.This system is extensively used for motor cars.
Description of some parts used in petrol engine.
01)Fuel Pump:-
A diaphragm type fuel pump is used in petrol engines as there is no need of extra high pressure of fuel.This fuel pump is extensively used to pump the fuel from fuel tank to the carburettor in the automotive engines.A flexible diaphragm is moved down against the force of the diaphragm spring by the diaphragm lever and the operating arm which is actuated by the camshaft eccentrically.
The pressure falls in the pump chamber and so the fuel from the fuel tank flows through the fuel inlet valve.Fuel inlet valve closes at the return stroke as diaphragm spring forces the diaphragm upwards,same time fuel outlet valve opens and thus the fuel starts flowing from the pump to the carburettor.
02)Fuel Filter:-
To get rid of unwanted dirt,filters are used.A filter used to clean the air is known as air filter,to clean fuel,is known as fuel filter,to clean lubricating oil,is known as oil filter.In filters,paper elements,cloth elements,felt elements and the combination of felt and cloth elements are used.Basically there are two types of fuel filters used
a) Preliminary fuel filter
b) Secondary fuel filter.
03)Carburettor:-
This is the device which mixes the fuel with air and supply this mixture to induction manifold of the engine.The carburettor controls the required quantity of fuel and breaks up into minute globules for being mixed with the correct quantity of air.Types of carburettor are
a) Zenith carburettor
b) Solex carburettor
c) Amal carburettor.
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Valves And Valve Mechanism used in Internal Combustion Engine.
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Friday
Valves And Valve Mechanism used in Internal Combustion Engine.
In four stroke internal combustion engine,the "Poppet Valve" performed the opening of the cylinder to inlet or exhaust manifold at the correct moment.Generally the face of valve is ground at 45 degree but in same cases it is ground at 30 degree also.It is not important to have a same angle of face in inlet and exhaust valve of same engines.To make it in right order,the valve may be reground after some use.There is some margin provided to avoid sharp edges.The groove,retain the valve spring which aids in keeping the valve pressed against the seat when closed and thus seal the combustion space tightly.In close position,the valve face,fits the accurately matched ground seat in the cylinder block.Generally replaceable ring inserts are used for exhaust valve seat.
The inlet valves are made from plain nickel,nickel chrome or chrome molybdenum.Where as exhaust valves are made from nickel chrome,silicon chrome steel,high speed steel,stainless steel,high nickel chrome,tungsten steel and cobalt chrome steel.
Valve Mechanism of a Side Valve:-
Poppet valve has following main parts,
01) Cam Shaft
02) Cam
03) Cam Follower
04) Tappet
05) Adjusting Screw
06) Washer
07) Valve Spring
08) Valve Stem
09) Valve Stem Guide
10) Valve Face
With the help of these parts,valve performs it's operation very accurately in internal combustion engine.
The cam actuates the movement of the valve through the tappet.The replaceable valve stem moves up and down in the valve stem guide.This movement is obtained by rotation of camshaft and cam,which generally runs at the half the engine speed.
The valve spring,keeps the valve pressed against its seat and ensure a leakage proof operation and also bring back the valve very quickly during its closing.
When the engine is started,it gets heated up gradually there by causing the valve stem to expands.A valve tappet clearance is always provided to allow the expansion of valve stem and other parts.This clearance value depends upon the length of the valve,its material and the operating temperature of the engine.The tappet valve clearance can be adjusted by rotating the adjusting screw.
Where adjusting screw is not provided to vary the clearance,it can be increased by grinding the bottom of the valve stem and face or by using longer valve.Due care must be taken because even a slightly insufficient clearance may lead to the valve not properly resting against its seat as the engine gets heated causing increased noise level and loss of power.
The clearance provided in exhaust valve is slightly more than that of inlet valve.This is due to slightly more expansion in exhaust valve because of higher temperature of hot exhaust gases produced during combustion.
Valve Mechanism Of Overhead Valve:-
In this mechanism,a push rod and a rocker arm,to push the valve against the spring pressure is required.The rocker arm rotates about the rocker arm shaft under the force exerted by the push rod.The clearance in this case is kept between the rocker arm and the valve stem and can be adjusted by the screw adjuster.A suitable gear train or chain is provided to convert the drive from crankshaft to camshaft.
In high speed engines,the frequency of vibration of the valve spring coincides with normal operating frequency of the valve which leads to resonance and increasing the surging effect.To overcome this problem,now a days compound spring are used.Compound spring means "One spring within the other of different natural frequencies".
Valves are the most important part of every engines,So due care must be taken in selection and maintenance of valve.
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The inlet valves are made from plain nickel,nickel chrome or chrome molybdenum.Where as exhaust valves are made from nickel chrome,silicon chrome steel,high speed steel,stainless steel,high nickel chrome,tungsten steel and cobalt chrome steel.
Valve Mechanism of a Side Valve:-
Poppet valve has following main parts,
01) Cam Shaft
02) Cam
03) Cam Follower
04) Tappet
05) Adjusting Screw
06) Washer
07) Valve Spring
08) Valve Stem
09) Valve Stem Guide
10) Valve Face
With the help of these parts,valve performs it's operation very accurately in internal combustion engine.
The cam actuates the movement of the valve through the tappet.The replaceable valve stem moves up and down in the valve stem guide.This movement is obtained by rotation of camshaft and cam,which generally runs at the half the engine speed.
The valve spring,keeps the valve pressed against its seat and ensure a leakage proof operation and also bring back the valve very quickly during its closing.
When the engine is started,it gets heated up gradually there by causing the valve stem to expands.A valve tappet clearance is always provided to allow the expansion of valve stem and other parts.This clearance value depends upon the length of the valve,its material and the operating temperature of the engine.The tappet valve clearance can be adjusted by rotating the adjusting screw.
Where adjusting screw is not provided to vary the clearance,it can be increased by grinding the bottom of the valve stem and face or by using longer valve.Due care must be taken because even a slightly insufficient clearance may lead to the valve not properly resting against its seat as the engine gets heated causing increased noise level and loss of power.
The clearance provided in exhaust valve is slightly more than that of inlet valve.This is due to slightly more expansion in exhaust valve because of higher temperature of hot exhaust gases produced during combustion.
Valve Mechanism Of Overhead Valve:-
In this mechanism,a push rod and a rocker arm,to push the valve against the spring pressure is required.The rocker arm rotates about the rocker arm shaft under the force exerted by the push rod.The clearance in this case is kept between the rocker arm and the valve stem and can be adjusted by the screw adjuster.A suitable gear train or chain is provided to convert the drive from crankshaft to camshaft.
In high speed engines,the frequency of vibration of the valve spring coincides with normal operating frequency of the valve which leads to resonance and increasing the surging effect.To overcome this problem,now a days compound spring are used.Compound spring means "One spring within the other of different natural frequencies".
Valves are the most important part of every engines,So due care must be taken in selection and maintenance of valve.
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Details About Connecting Rod And Gudgeon Pin Of I.C.Engine.
Details About Piston Rings Of Internal Combustion Engine.
Information Of Piston Used In Internal Combustion Engine.
Thursday
Details About Connecting Rod And Gudgeon Pin Of I.C.Engine.
In every internal combustion engine,there are various parts,connected to each other.To convert reciprocating motion of piston into rotary motion of crankshaft,we have to connect,piston to crankshaft with the help of connecting rod and gudgeon pin.Below you will find details about these two parts.
01) Connecting Rod:-
The load on the piston due to combustion of fuel in the combustion chamber is transmitted to crankshaft through the connecting rod.One end of connecting rod known as small end and is connected to the piston through gudgeon pin while the other end known as big end and is connected to crankshaft through crank pin.
Connecting rods are usually made up of drop forged I section.In large size internal combustion engine,the connecting rods of rectangular section have been employed.In such cases,the larger dimensions are kept in the plane of rotation.
In petrol engine,the connecting rod's big end is generally split to enable its clamping around the crankshaft.Suitable diameter holes are provided to accommodate connecting rod bolts for clamping.The big end of connecting rod is clamped with crankshaft with the help of connecting rod bolt,nut and split pin or cotter pin.
Generally,plain carbon steel is used as material to manufacture connecting rod but where low weight is most important factor,aluminium alloys are most suitable.Nickel alloy steel are also used for heavy duty engine's connecting rod.
02)Gudgeon Pin:-
This pin connects the piston with small end of the connecting rod,and also known as piston pin.It is made up of case hardened steel and accurately ground to the required diameters.Gudgeon pins are made hollow to reduce its weight,resulting low inertia effect of reciprocating parts.
This pin is also known as "Fully Floating" as this is free to turn or oscillate both in the piston bosses as well as the small end of the connecting rod.There are very less chances of seizure in this case but the end movement of the pin must be restricted to score the cylinder walls.This can be achieved by using any one of the following three methods,
A) One spring circlip at each end is fitted into the groove in the piston bosses.
B) On spring circlip is provided in the middle.
C) Bronze or Aluminium pads are fitted at both ends of the pin,which
prevents the cylinder walls from being damaged.
The gudgeon pin may also be semi-floating type,in which either the pin is free to turn or oscillate in the small end bearing but secured in the piston bosses or it may secured in the small end bearing and allowed a free oscillating movement in the piston bosses.This method provides more bearing area at the bosses and hence no need for providing bushes there in,is preferred.
Do you have any doubt,please put it by comments.
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Details About Piston Rings Of Internal Combustion Engine.
Information Of Piston Used In Internal Combustion Engine.
01) Connecting Rod:-
The load on the piston due to combustion of fuel in the combustion chamber is transmitted to crankshaft through the connecting rod.One end of connecting rod known as small end and is connected to the piston through gudgeon pin while the other end known as big end and is connected to crankshaft through crank pin.
Connecting rods are usually made up of drop forged I section.In large size internal combustion engine,the connecting rods of rectangular section have been employed.In such cases,the larger dimensions are kept in the plane of rotation.
In petrol engine,the connecting rod's big end is generally split to enable its clamping around the crankshaft.Suitable diameter holes are provided to accommodate connecting rod bolts for clamping.The big end of connecting rod is clamped with crankshaft with the help of connecting rod bolt,nut and split pin or cotter pin.
Generally,plain carbon steel is used as material to manufacture connecting rod but where low weight is most important factor,aluminium alloys are most suitable.Nickel alloy steel are also used for heavy duty engine's connecting rod.
02)Gudgeon Pin:-
This pin connects the piston with small end of the connecting rod,and also known as piston pin.It is made up of case hardened steel and accurately ground to the required diameters.Gudgeon pins are made hollow to reduce its weight,resulting low inertia effect of reciprocating parts.
This pin is also known as "Fully Floating" as this is free to turn or oscillate both in the piston bosses as well as the small end of the connecting rod.There are very less chances of seizure in this case but the end movement of the pin must be restricted to score the cylinder walls.This can be achieved by using any one of the following three methods,
A) One spring circlip at each end is fitted into the groove in the piston bosses.
B) On spring circlip is provided in the middle.
C) Bronze or Aluminium pads are fitted at both ends of the pin,which
prevents the cylinder walls from being damaged.
The gudgeon pin may also be semi-floating type,in which either the pin is free to turn or oscillate in the small end bearing but secured in the piston bosses or it may secured in the small end bearing and allowed a free oscillating movement in the piston bosses.This method provides more bearing area at the bosses and hence no need for providing bushes there in,is preferred.
Do you have any doubt,please put it by comments.
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Details About Piston Rings Of Internal Combustion Engine.
Information Of Piston Used In Internal Combustion Engine.
Wednesday
Details About Piston Rings Of Internal Combustion Engine.
You may know,in order to reduce wear and increase the life of piston grooves in high speed engines,a ferrous metal rings are inserted into the grooves.Below,you will find detail description of piston ring used in Internal Combustion Engine.This information is useful and valuable for every mechanical or automobile engineer or automobile owner.
The piston rings,which are also called as compression rings are fit closely in the grooves provided in the piston.These rings are worn out before the wearing of the piston and cylinder wall.Hence by replacing the same,we can avoid replacement of piston or cylinder.
The leakage of the high temperature gases produced during power stroke in the combustion chamber are prevented by piston rings.The piston rings form an effective seal and at the same time transmit heat from crown to the cylinder walls and hence keep the temperature within the workable limit.
There should be at least two piston rings in each piston of internal combustion engine.For the higher capacity engines,there are four or even six piston rings have been used.The number of rings are depend upon the capacity and size of the I.C.Engine.
In order to achieve the effective seal against lubricating oil and high pressure gases leakage,a great pressure must be exerted ,by each ring on the cylinder walls.To produce this effect,the rings are made slightly larger in the diameter than that of cylinder bore and cutting small gap which is partly narrowed when the ring is fitted.The end gap in the piston ring provides flexibility to the ring and the same time allowing for thermal expansion.
There are another rings used in piston grooves,called as, Oil Scraper Rings.The function of these rings are,only as much quantity of the oil as it just sufficient to maintain proper lubrication is allowed to reach the skit.The excess oil which would have leaked in the combustion chamber without serving any useful purpose and rather leading to carbonization,is scraped off by the oil scraper ring.
While mounting the piston rings over the piston,a great care should be taken to ensure that the gaps of various rings should not fall in the same vertical line.
The piston rings of internal combustion engines are made in various section such as,standard,tapered,grooved,wedge and L shape.Where as oil scraper rings are made as,narrow,wide,tapered and six segment cord section.
The cast iron along with 2.5% silicon will provide a good wear Resistance to piston ring.In case of passenger cars,the piston rings are usually plated with Chromium Tin or Cadmium.The plating reduces the rate of cylinder wear and hence increase the life of internal combustion engine.
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The piston rings,which are also called as compression rings are fit closely in the grooves provided in the piston.These rings are worn out before the wearing of the piston and cylinder wall.Hence by replacing the same,we can avoid replacement of piston or cylinder.
The leakage of the high temperature gases produced during power stroke in the combustion chamber are prevented by piston rings.The piston rings form an effective seal and at the same time transmit heat from crown to the cylinder walls and hence keep the temperature within the workable limit.
There should be at least two piston rings in each piston of internal combustion engine.For the higher capacity engines,there are four or even six piston rings have been used.The number of rings are depend upon the capacity and size of the I.C.Engine.
In order to achieve the effective seal against lubricating oil and high pressure gases leakage,a great pressure must be exerted ,by each ring on the cylinder walls.To produce this effect,the rings are made slightly larger in the diameter than that of cylinder bore and cutting small gap which is partly narrowed when the ring is fitted.The end gap in the piston ring provides flexibility to the ring and the same time allowing for thermal expansion.
There are another rings used in piston grooves,called as, Oil Scraper Rings.The function of these rings are,only as much quantity of the oil as it just sufficient to maintain proper lubrication is allowed to reach the skit.The excess oil which would have leaked in the combustion chamber without serving any useful purpose and rather leading to carbonization,is scraped off by the oil scraper ring.
While mounting the piston rings over the piston,a great care should be taken to ensure that the gaps of various rings should not fall in the same vertical line.
The piston rings of internal combustion engines are made in various section such as,standard,tapered,grooved,wedge and L shape.Where as oil scraper rings are made as,narrow,wide,tapered and six segment cord section.
The cast iron along with 2.5% silicon will provide a good wear Resistance to piston ring.In case of passenger cars,the piston rings are usually plated with Chromium Tin or Cadmium.The plating reduces the rate of cylinder wear and hence increase the life of internal combustion engine.
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Information Of Piston Used In Internal Combustion Engine.
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Working Principle Of Four Stroke Diesel Engine.
Information Of Piston Used In Internal Combustion Engine.
In every engine piston plays an important role in working and producing results.Piston forms a guide and bearing for the small end of connecting rod and also transmits the force of explosion in the cylinder,to the crank shaft through connecting rod.
Construction Of Piston:-
Its top known by many names such as crown,head or ceiling and thicker than bottom portion.Bottom portion is known as skirt.There are grooves made to accommodate the compression rings and oil rings.the groove,made for oil ring,is wider and deeper than the grooves made for compression ring.The oil ring scraps the excess oil which flows into the piston interior through the oil return holes and thus avoiding to reach the combustion chamber but helps to lubricate the gudgeon pin to some extent.In some designs the oil ring is provided below the gudgeon pin boss .The space between the grooves are called as lands.
The diameter of piston always kept smaller than that of cylinder because the piston reaches a temperature higher than cylinder wall and expands during engine operation.The space between the cylinder wall and piston is known as piston clearance.The diameter of the piston at crown is slightly less than at the skirt due to variation in the operating temperatures.Again the skirt itself is also slightly tapered to allow for unequal expansion due to temperature difference as we move vertically along the skirt the working temperature is not uniform but slightly decrease.
Which Material Is Most Suitable For Piston?
Cast Iron,Aluminium Alloy and Cast Steel etc. are the common materials used for piston of an Internal Combustion Engine.Cast Iron piston are not suitable for high speed engines due its more weight.these piston has greater strength and resistance to wear.
The Aluminium Alloy Piston is lighter in weight and enables much lower running temperatures due to its higher thermal conductivity.The coefficient of expansion of this type of piston is about 20% less than that of pure aluminum piston but higher than that of cast iron piston and cylinder wall.To avoid seizure because of higher expansion than cylinder wall,more piston clearance required to be provided.It results in piston slap after the engine is started but still warming up and tends to separate the crown from the skirt of the piston.
Cutting a vertical slot will avoid this disadvantage.this slot helps in taking up thermal expansion and so the overall diameter of the piston is not required to be so reduced as to obstruct the safe operation between the cylinder walls and the pistons.
To increase the life of grooves and to reduce the wear,a ferrous metal rings are inserted in the grooves of high speed engines.
I hope,this information will help you to select proper piston.The details about other parts of Internal Combustion Engine will be cover in coming posts.
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Different Types Of Scavenging Methods Used In Internal Combustion Engine.
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Details Of Crankshaft Used In Internal Combustion Engine.
Construction Of Piston:-
Its top known by many names such as crown,head or ceiling and thicker than bottom portion.Bottom portion is known as skirt.There are grooves made to accommodate the compression rings and oil rings.the groove,made for oil ring,is wider and deeper than the grooves made for compression ring.The oil ring scraps the excess oil which flows into the piston interior through the oil return holes and thus avoiding to reach the combustion chamber but helps to lubricate the gudgeon pin to some extent.In some designs the oil ring is provided below the gudgeon pin boss .The space between the grooves are called as lands.
The diameter of piston always kept smaller than that of cylinder because the piston reaches a temperature higher than cylinder wall and expands during engine operation.The space between the cylinder wall and piston is known as piston clearance.The diameter of the piston at crown is slightly less than at the skirt due to variation in the operating temperatures.Again the skirt itself is also slightly tapered to allow for unequal expansion due to temperature difference as we move vertically along the skirt the working temperature is not uniform but slightly decrease.
Which Material Is Most Suitable For Piston?
Cast Iron,Aluminium Alloy and Cast Steel etc. are the common materials used for piston of an Internal Combustion Engine.Cast Iron piston are not suitable for high speed engines due its more weight.these piston has greater strength and resistance to wear.
The Aluminium Alloy Piston is lighter in weight and enables much lower running temperatures due to its higher thermal conductivity.The coefficient of expansion of this type of piston is about 20% less than that of pure aluminum piston but higher than that of cast iron piston and cylinder wall.To avoid seizure because of higher expansion than cylinder wall,more piston clearance required to be provided.It results in piston slap after the engine is started but still warming up and tends to separate the crown from the skirt of the piston.
Cutting a vertical slot will avoid this disadvantage.this slot helps in taking up thermal expansion and so the overall diameter of the piston is not required to be so reduced as to obstruct the safe operation between the cylinder walls and the pistons.
To increase the life of grooves and to reduce the wear,a ferrous metal rings are inserted in the grooves of high speed engines.
I hope,this information will help you to select proper piston.The details about other parts of Internal Combustion Engine will be cover in coming posts.
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Sunday
Comparison Of Petrol Engine And Diesel Engine.
In mechanical or automobile field petrol engine or diesel engine is used for any particular job.So,it is most important to know which type of engine is most suitable for selection.For the proper selection of engine,we must compare these engines with each other.By this way we come to know the advantages and disadvantages of particular engine.Here i am comparing petrol engine and diesel engine which is widely used in one or another purpose.
01)In petrol engine a charge of petrol and air is taken inside the cylinder during suction stroke which is further compressed during compression stroke.Pre-ignition can be achieved in petrol engine as there is increase in temperature due to compression above the ignition point of petrol.In diesel engine,only air is compressed during compression stroke and fuel is injected afterwards.That's why no pre-ignition achieved in diesel engine.
02)The diesel engine is more difficult to start due to greater cranking efforts required to overcome the higher compression ratio.
03)Petrol engines has more chances of fire hazards as compared to diesel engine.
04)A carburettor is used in petrol engine,which supplies the mixture of air and petrol in the proper portion according to requirement but in diesel engine,an injector or auto miser is used to inject the fuel at the end of compression stroke.
05)No external source of heat is required to burn the fuel in diesel engine as it burns by the heat of compressed air.In petrol engine,a spark plug is required to ignite the charge with an electric spark.
06)The diesel engine is heavier and stronger than petrol engine.As a result,diesel engine is more expensive in initial cost and repairing cost.A higher grade of material and workmanship is required in diesel engine due to high compression ratio.
07)Though initial cost of diesel engine is more but it will run almost double than petrol engine for same quantity of fuel.The cost of diesel is less than petrol,hence running cost is lower than petrol engine.For all sort of heavy work diesel engine gets more preference than petrol engine.
08)On reduced load,the the petrol engine is superior to the diesel engine because of better mixing of fuel and air.
09)The thermal efficiency of diesel engine is higher than petrol engine because of high compression ratio used.
10)The petrol engine works on Otto cycle where as diesel engine works on Diesel cycle.
From the above comparison we can see that both engines have certain advantages and disadvantages.The determination of the type selected for a particular job must be based on these relative advantages and disadvantages in relation to the requirement of the task to be performed.
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01)In petrol engine a charge of petrol and air is taken inside the cylinder during suction stroke which is further compressed during compression stroke.Pre-ignition can be achieved in petrol engine as there is increase in temperature due to compression above the ignition point of petrol.In diesel engine,only air is compressed during compression stroke and fuel is injected afterwards.That's why no pre-ignition achieved in diesel engine.
02)The diesel engine is more difficult to start due to greater cranking efforts required to overcome the higher compression ratio.
03)Petrol engines has more chances of fire hazards as compared to diesel engine.
04)A carburettor is used in petrol engine,which supplies the mixture of air and petrol in the proper portion according to requirement but in diesel engine,an injector or auto miser is used to inject the fuel at the end of compression stroke.
05)No external source of heat is required to burn the fuel in diesel engine as it burns by the heat of compressed air.In petrol engine,a spark plug is required to ignite the charge with an electric spark.
06)The diesel engine is heavier and stronger than petrol engine.As a result,diesel engine is more expensive in initial cost and repairing cost.A higher grade of material and workmanship is required in diesel engine due to high compression ratio.
07)Though initial cost of diesel engine is more but it will run almost double than petrol engine for same quantity of fuel.The cost of diesel is less than petrol,hence running cost is lower than petrol engine.For all sort of heavy work diesel engine gets more preference than petrol engine.
08)On reduced load,the the petrol engine is superior to the diesel engine because of better mixing of fuel and air.
09)The thermal efficiency of diesel engine is higher than petrol engine because of high compression ratio used.
10)The petrol engine works on Otto cycle where as diesel engine works on Diesel cycle.
From the above comparison we can see that both engines have certain advantages and disadvantages.The determination of the type selected for a particular job must be based on these relative advantages and disadvantages in relation to the requirement of the task to be performed.
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Saturday
Advantages And Disadvantages Of Two Stroke Cycle Engine.
Many of us uses motor bike or car for travelling purpose.How much you know about the engine and how it works? I bet,most people don't know anything about this.Those who are in mechanical field,must be familiar about working principle of two stroke or four cycle engine but common person don't.That is why I am giving here,the advantages and disadvantages of two stroke cycle engine over four stroke cycle engine.
First we will see the advantages.
01)Two stroke cycle engine is more compact,requires less space and lighter in weight than four stroke cycle engine for same output or power.Power developed per kilogram of engine weight is higher in two stroke cycle engine.That's why it is more suitable for motor bike and scooters.
02)The two stroke cycle engine gives one working stroke for each revolution of crankshaft.Hence theoretically the power developed for the same engine speed and cylinder volume is twice is that of four stroke cycle engine which gives one working stroke for every two revolution of the crankshaft.
03)We can use lighter flywheel in two stroke cycle engine as their is one working stroke for each revolution of crankshaft.
04)The design and construction is much simpler than four stroke engine that's why it is easy to manufacture and cost effective.
05)As there is no suction and exhaust valve used in two stroke cycle engine hence no need of cams,camshaft and rockers etc. of the valve gear.Resulting in higher mechanical efficiency.
06)Due two suction and exhaust ports only,there is work saved avoiding friction.
07)Two stroke cycle engine gives less torsional oscillations.
08)This type of engine requires less spare parts.
09)A two stroke cycle engine can be easily reversed if it is of valveless type.
10)Due to simplicity in construction and fewer parts,two stroke cycle engine is easy for maintenance.Hence reduce the initial and maintenance cost also.
From above description you may prefer two stroke engine,but wait,there are some disadvantages also.They are as below.
01)The fuel consumption is higher in case of two stroke engine working on Otto cycle.This happens due to some of the fuel or unburnt gas likely to be wasted by escaping through the exhaust port.
02)Since the ports remains open during up word stroke,the actual compression starts only after both inlet and exhaust ports have been closed.So actual compression ratio and the thermal efficiency of the two stroke cycle engine is less than that of four stroke engine of the same dimension.
03)The dilution of charges takes place due to incomplete scavenging.
04)Two stroke engine consumes more lubricating oil.
05)There is greater wear and tear of moving parts hence it gives loud noise.
So,choice is yours,you know the advantages and disadvantages of two stroke cycle engine.
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First we will see the advantages.
01)Two stroke cycle engine is more compact,requires less space and lighter in weight than four stroke cycle engine for same output or power.Power developed per kilogram of engine weight is higher in two stroke cycle engine.That's why it is more suitable for motor bike and scooters.
02)The two stroke cycle engine gives one working stroke for each revolution of crankshaft.Hence theoretically the power developed for the same engine speed and cylinder volume is twice is that of four stroke cycle engine which gives one working stroke for every two revolution of the crankshaft.
03)We can use lighter flywheel in two stroke cycle engine as their is one working stroke for each revolution of crankshaft.
04)The design and construction is much simpler than four stroke engine that's why it is easy to manufacture and cost effective.
05)As there is no suction and exhaust valve used in two stroke cycle engine hence no need of cams,camshaft and rockers etc. of the valve gear.Resulting in higher mechanical efficiency.
06)Due two suction and exhaust ports only,there is work saved avoiding friction.
07)Two stroke cycle engine gives less torsional oscillations.
08)This type of engine requires less spare parts.
09)A two stroke cycle engine can be easily reversed if it is of valveless type.
10)Due to simplicity in construction and fewer parts,two stroke cycle engine is easy for maintenance.Hence reduce the initial and maintenance cost also.
From above description you may prefer two stroke engine,but wait,there are some disadvantages also.They are as below.
01)The fuel consumption is higher in case of two stroke engine working on Otto cycle.This happens due to some of the fuel or unburnt gas likely to be wasted by escaping through the exhaust port.
02)Since the ports remains open during up word stroke,the actual compression starts only after both inlet and exhaust ports have been closed.So actual compression ratio and the thermal efficiency of the two stroke cycle engine is less than that of four stroke engine of the same dimension.
03)The dilution of charges takes place due to incomplete scavenging.
04)Two stroke engine consumes more lubricating oil.
05)There is greater wear and tear of moving parts hence it gives loud noise.
So,choice is yours,you know the advantages and disadvantages of two stroke cycle engine.
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Monday
Different Types Of Scavenging Methods Used In Internal Combustion Engine.
If the burnt exhaust gases,in an Internal Combustion Engine(whether it works on spark ignition or compression ignition principle),are made to remain inside the cylinder.These burnt gases,would mix up with the fresh incoming charge thus diluting latter and reducing its strength.
The process of removing burnt exhaust gases from the combustion chamber of the engine cylinder is known as Scavenging.
In four stroke cycle engine,the piston,during its exhaust stroke pushes the burnt gases into the exhaust manifold to escape to atmosphere through exhaust valve.But in two stroke cycle engine,a blast of fresh charge is made to enter at higher velocity into the combustion chamber at the end of working stroke of the piston and thus drives out the burnt exhaust gases.
In case of two stroke spark ignition engine there is a possibility of the fresh charge escaping out with the burnt exhaust gases because there is a small fraction of revolution of the crank during which the exhaust of the burnt gases and the entry of the fresh charge is taking place simultaneously.To overcome this difficulty,the piston crown is manufactured in a particular shape so that the fresh charge is deflected upward after entering the cylinder.
To carry out Scavenging,following are the three basic methods used.
01)Cross Flow Scavenging:-
In this method,the inlet or transfer ports are situated on one side of the cylinder while exhaust ports are situated on the opposite side.The piston crown is designed into a particular shape so that the fresh charge is deflected upward to push out the burnt exhaust gases.
02)Back Flow or Loop Scavenging:-
In this method,the inlet and exhaust ports are situated on the same side of the cylinder.A loop is formed as the fresh charge of air-fuel mixture or pure air enters the cylinder to push out the burnt exhaust gases.
03)Uniform Scavenging:-
In this method,both the fresh charge and the burnt exhaust gases moves in the same upward direction in the cylinder.The valve closes,as the piston moves upward during the compression stroke.Fresh charge is supplied from the side of the cylinder.
The compression of fresh charge can be achieved by the following way.
01)Separate Compressor:-
Sometimes a separate compressor is provided to compress the charge for being subsequently supplied to the combustion chamber.The compressor may be driven by engine crankshaft or by external power.
02)Cylinder Compression:-
In this,the charge is previously compressed by the other side of the piston sliding on the other side of cylinder,which is also closed.It has suction valve to admit the fresh charge.The partially compressed charge is then supplied to the combustion chamber as usual.
03)Crankcase Compression:-
This is discussed in "The History And Working Of Two Stroke Petrol Engine. "(Please refer)
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The process of removing burnt exhaust gases from the combustion chamber of the engine cylinder is known as Scavenging.
In four stroke cycle engine,the piston,during its exhaust stroke pushes the burnt gases into the exhaust manifold to escape to atmosphere through exhaust valve.But in two stroke cycle engine,a blast of fresh charge is made to enter at higher velocity into the combustion chamber at the end of working stroke of the piston and thus drives out the burnt exhaust gases.
In case of two stroke spark ignition engine there is a possibility of the fresh charge escaping out with the burnt exhaust gases because there is a small fraction of revolution of the crank during which the exhaust of the burnt gases and the entry of the fresh charge is taking place simultaneously.To overcome this difficulty,the piston crown is manufactured in a particular shape so that the fresh charge is deflected upward after entering the cylinder.
To carry out Scavenging,following are the three basic methods used.
01)Cross Flow Scavenging:-
In this method,the inlet or transfer ports are situated on one side of the cylinder while exhaust ports are situated on the opposite side.The piston crown is designed into a particular shape so that the fresh charge is deflected upward to push out the burnt exhaust gases.
02)Back Flow or Loop Scavenging:-
In this method,the inlet and exhaust ports are situated on the same side of the cylinder.A loop is formed as the fresh charge of air-fuel mixture or pure air enters the cylinder to push out the burnt exhaust gases.
03)Uniform Scavenging:-
In this method,both the fresh charge and the burnt exhaust gases moves in the same upward direction in the cylinder.The valve closes,as the piston moves upward during the compression stroke.Fresh charge is supplied from the side of the cylinder.
The compression of fresh charge can be achieved by the following way.
01)Separate Compressor:-
Sometimes a separate compressor is provided to compress the charge for being subsequently supplied to the combustion chamber.The compressor may be driven by engine crankshaft or by external power.
02)Cylinder Compression:-
In this,the charge is previously compressed by the other side of the piston sliding on the other side of cylinder,which is also closed.It has suction valve to admit the fresh charge.The partially compressed charge is then supplied to the combustion chamber as usual.
03)Crankcase Compression:-
This is discussed in "The History And Working Of Two Stroke Petrol Engine. "(Please refer)
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Thursday
The History And Working Of Two Stroke Petrol Engine.
In four stroke cycle engine,there is only one working stroke in each cycle.It means,two revolutions of crank-shaft are required to produce work in each cycle.The desire to have one working stroke per cylinder for every revolution of the crank-shaft has led to development of two stroke cycle engines.
In 1838,Barnett an Englishman describe the mechanism for supplying a charge to the cylinder by means of separate pumps,the fresh charge of fuel,displacing the product of the previous charge.Dugald Clerk also made a lot of contributions in this direction in 1878.
Two stroke cycle are very widely employed where small power required for motor cycle,auto rickshaw,scooters.This type of engines are compact in size,easy for manufacturing and simple in operations.One drawback is there,Specific Fuel Consumption (S.F.C) is more.(means fuel per Break Horse Power (b.h.p.) per hour is more).
There are no inlet and exhaust valves as in four stroke engine but we have inlet and exhaust ports only,due to which suction and exhaust stroke are eliminated in two stroke cycle engine.Here the burnt exhaust gases are forced out through the exhaust port by a fresh charge of fuel which enters the cylinder nearly at the end of working stroke through inlet port.This process is called as "Scavenging".Details about Scavenging will be covered in another post.
As I told above,it has no valves but consists of the inlet port(IP),exhaust port(EP) and transfer port(TP).The ignition starts due to the spark given by spark plug when the piston be nearing the completion of its compression stroke.As a result,piston is pushed down performing the working stroke and in doing so,the air-fuel mixture already drawn from the inlet port in the previous stroke is compressed to a pressure of about 1.4 kilogram/centimeter square.
When 80% of this stroke is completed the exhaust port is uncovered slightly and some of the charge of burnt gases escape to the atmosphere.As the exhaust port is uncovered by the further downward movement of the piston,the transfer port,which is slightly lower than exhaust port,is also uncovered and a charge of compressed air-fuel mixture enters the cylinder and further pushes out the burnt gases out of the exhaust port.
To facilitate the deflection of the fresh charge upward and to avoid its escape along with exhaust gases,the top of the piston is made of a particular shape.
From bottom dead centre,when the piston moves up,it first closes the transfer port and then exhaust port.The charge of fuel which previously entered in the cylinder is now compressed.When the piston is nearing the upward movement the inlet port opens and afresh charge of air-fuel mixture from the carburettor enters the crankcase.After the ignition of charge takes place the piston moves down for the power stroke and thus the cycle is repeated.
It can be fairly assumed that the crankcase and the bottom of the piston form a compressor assembly.In which the work used up in compressing the charge is negative.The top of the piston is considered as positive and crankcase is as negative.The difference between the positive and negative loop gives us the net work available from engine.
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In 1838,Barnett an Englishman describe the mechanism for supplying a charge to the cylinder by means of separate pumps,the fresh charge of fuel,displacing the product of the previous charge.Dugald Clerk also made a lot of contributions in this direction in 1878.
Two stroke cycle are very widely employed where small power required for motor cycle,auto rickshaw,scooters.This type of engines are compact in size,easy for manufacturing and simple in operations.One drawback is there,Specific Fuel Consumption (S.F.C) is more.(means fuel per Break Horse Power (b.h.p.) per hour is more).
There are no inlet and exhaust valves as in four stroke engine but we have inlet and exhaust ports only,due to which suction and exhaust stroke are eliminated in two stroke cycle engine.Here the burnt exhaust gases are forced out through the exhaust port by a fresh charge of fuel which enters the cylinder nearly at the end of working stroke through inlet port.This process is called as "Scavenging".Details about Scavenging will be covered in another post.
As I told above,it has no valves but consists of the inlet port(IP),exhaust port(EP) and transfer port(TP).The ignition starts due to the spark given by spark plug when the piston be nearing the completion of its compression stroke.As a result,piston is pushed down performing the working stroke and in doing so,the air-fuel mixture already drawn from the inlet port in the previous stroke is compressed to a pressure of about 1.4 kilogram/centimeter square.
When 80% of this stroke is completed the exhaust port is uncovered slightly and some of the charge of burnt gases escape to the atmosphere.As the exhaust port is uncovered by the further downward movement of the piston,the transfer port,which is slightly lower than exhaust port,is also uncovered and a charge of compressed air-fuel mixture enters the cylinder and further pushes out the burnt gases out of the exhaust port.
To facilitate the deflection of the fresh charge upward and to avoid its escape along with exhaust gases,the top of the piston is made of a particular shape.
From bottom dead centre,when the piston moves up,it first closes the transfer port and then exhaust port.The charge of fuel which previously entered in the cylinder is now compressed.When the piston is nearing the upward movement the inlet port opens and afresh charge of air-fuel mixture from the carburettor enters the crankcase.After the ignition of charge takes place the piston moves down for the power stroke and thus the cycle is repeated.
It can be fairly assumed that the crankcase and the bottom of the piston form a compressor assembly.In which the work used up in compressing the charge is negative.The top of the piston is considered as positive and crankcase is as negative.The difference between the positive and negative loop gives us the net work available from engine.
You may also interested in following........
Working Principle Of Four Stroke Diesel Engine.
Working Principle Of Four Stroke Spark Ignition Engine.
10 Major Parts of Reciprocating Air Compressor.
Monday
Working Principle Of Four Stroke Diesel Engine.
There are different types cycles in thermodynamics.Such as Otto cycle,Carnot vapour cycle,Diesel cycle etc.Out of that cycle diesel engine works on diesel cycle.This cycle is also known as constant pressure cycle.Diesel engine is mostly employed in Stationary Power plants,Ships,Heavy Motor Vehicles.
In Petrol Engine,the air-fuel mixture after being compressed in the engine cylinder to a high pressure,is ignited by an electric spark from a spark plug.In diesel engine,diesel oil and light and heavy oil used as fuel.This fuel is ignited by being injected into the engine cylinder containing air compressed to a very high pressure,the temperature of this air is sufficiently high to ignite the fuel.That is why there is no spark plug used in diesel engine.This high temperature compressed air used in the form of very fine spray is injected at a controlled rate so that the combustion of fuel proceeds at constant pressure.
Diesel Engine is mainly worked on below strokes.
01)Suction Stroke:-
In this stroke,the piston moves down from the top dead centre.As a result,inlet valve opens and air is drawn into the cylinder.After sufficient quantity of air with pressure is drawn,suction valve closes at the end of the stroke.The exhaust valve remains closed during this stroke.
02)Compression Stroke:-
In this stroke,piston moves up from the bottom dead centre.During this stroke both inlet and exhaust valve are closed.The air drawn into the cylinder during suction stroke,is entrapped inside the cylinder and compressed due to upward movement of the piston.In diesel engine,the compression ratio used is very high as a result,the air is finally compressed to a very high pressure up to 40 kilogram per centimeter square,at this pressure,the temperature of the air is reached to 1000 degree centigrade which is enough to ignite the fuel.
03)Constant Pressure Stroke:-
In this stroke,the fuel is injected into the hot compressed air where it starts burning,maintaining the pressure constant.When the piston moves to its top dead centre,the supply of fuel is cut-off.It is to be said that the fuel is injected at the end of compression stroke and injection continues till the point of cut-off,but in actual practise,the ignition starts before the end of compression stroke to take care of ignition tag.
04)Working Or Power Stroke:-
In this stroke,both inlet and exhaust valve remain closed.The hot gases (which are produced due to ignition of fuel during compression stroke) and compressed air,now expand adiabatically,in the cylinder pushing the piston down and hence work is done.At the end of stroke,the piston finally reaches the bottom dead centre.
05)Exhaust Stroke:-
In this stroke,the piston again moves upward.The exhaust valve opens,while inlet and fuel valve are closed.A greater part of the burnt fuel gases escape due to their own expansion.The upward movement of the piston pushes the remaining gases out through the open exhaust valve.Only a small quantity of exhaust gases stay in the combustion chamber.At the end of exhaust stroke,the exhaust valve closes and the cycle is thus completed.
As there is some resistance while operating in inlet and exhaust valve and the some portion of burnt gases remains inside the cylinder during the cycle, resulting the pumping losses.This pumping losses are treated as negative work and therefore subtracted from actual work done during the cycle.This will give us net work done from the cycle.
I hope,this information will help you to increase knowledge about diesel engine.
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Working Principle Of Four Stroke Spark Ignition Engine.
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In Petrol Engine,the air-fuel mixture after being compressed in the engine cylinder to a high pressure,is ignited by an electric spark from a spark plug.In diesel engine,diesel oil and light and heavy oil used as fuel.This fuel is ignited by being injected into the engine cylinder containing air compressed to a very high pressure,the temperature of this air is sufficiently high to ignite the fuel.That is why there is no spark plug used in diesel engine.This high temperature compressed air used in the form of very fine spray is injected at a controlled rate so that the combustion of fuel proceeds at constant pressure.
Diesel Engine is mainly worked on below strokes.
01)Suction Stroke:-
In this stroke,the piston moves down from the top dead centre.As a result,inlet valve opens and air is drawn into the cylinder.After sufficient quantity of air with pressure is drawn,suction valve closes at the end of the stroke.The exhaust valve remains closed during this stroke.
02)Compression Stroke:-
In this stroke,piston moves up from the bottom dead centre.During this stroke both inlet and exhaust valve are closed.The air drawn into the cylinder during suction stroke,is entrapped inside the cylinder and compressed due to upward movement of the piston.In diesel engine,the compression ratio used is very high as a result,the air is finally compressed to a very high pressure up to 40 kilogram per centimeter square,at this pressure,the temperature of the air is reached to 1000 degree centigrade which is enough to ignite the fuel.
03)Constant Pressure Stroke:-
In this stroke,the fuel is injected into the hot compressed air where it starts burning,maintaining the pressure constant.When the piston moves to its top dead centre,the supply of fuel is cut-off.It is to be said that the fuel is injected at the end of compression stroke and injection continues till the point of cut-off,but in actual practise,the ignition starts before the end of compression stroke to take care of ignition tag.
04)Working Or Power Stroke:-
In this stroke,both inlet and exhaust valve remain closed.The hot gases (which are produced due to ignition of fuel during compression stroke) and compressed air,now expand adiabatically,in the cylinder pushing the piston down and hence work is done.At the end of stroke,the piston finally reaches the bottom dead centre.
05)Exhaust Stroke:-
In this stroke,the piston again moves upward.The exhaust valve opens,while inlet and fuel valve are closed.A greater part of the burnt fuel gases escape due to their own expansion.The upward movement of the piston pushes the remaining gases out through the open exhaust valve.Only a small quantity of exhaust gases stay in the combustion chamber.At the end of exhaust stroke,the exhaust valve closes and the cycle is thus completed.
As there is some resistance while operating in inlet and exhaust valve and the some portion of burnt gases remains inside the cylinder during the cycle, resulting the pumping losses.This pumping losses are treated as negative work and therefore subtracted from actual work done during the cycle.This will give us net work done from the cycle.
I hope,this information will help you to increase knowledge about diesel engine.
You may also interested in following...........
Working Principle Of Four Stroke Spark Ignition Engine.
The Effect Of Inter cooling And Reheating On Gas Turbine Plant.
Concept Of Terms Connected With Internal Combustion Engine.
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