Four stroke engineFour stroke engine

projectproject

(2009-2010)(2009-2010)

TEAM WORKTEAM WORK

عبدالعزيز- 1111سكشن سكشن منصور جمال عبدالعزيز- احمد منصور جمال احمد

ابوالغيط- 1122سكشن سكشن حسن احمد السيد ابوالغيط- احمد حسن احمد السيد احمد

احمد- 1133سكشن سكشن محمد السيد احمد- احمد محمد السيد احمد

عبدالحميد- 1144سكشن سكشن محمد السيد عبدالحميد- احمد محمد السيد احمد

السعدني- 1155سكشن سكشن سعيد السعدني- احمد سعيد احمد

حسن- 1166سكشن سكشن عادل حسن- احمد عادل احمد

فرحات- 1177سكشن سكشن عنتر عبداللطيف فرحات- احمد عنتر عبداللطيف احمد

SUPERVISORSUPERVISOR

Prof.DrProf.Dr//

Four Stroke EngineFour Stroke Engine

Basic 4 Cycle TheoryBasic 4 Cycle Theory

Intake StrokeIntake Stroke

Compression StrokeCompression Stroke

Power StrokePower Stroke

Exhaust StrokeExhaust Stroke

Intake StrokeIntake Stroke

Rotation of the crankshaft pulls the piston downRotation of the crankshaft pulls the piston down.. At this time, the intake valve is opened, allowingAt this time, the intake valve is opened, allowing the piston to draw an air the piston to draw an air//fuel charge into the fuel charge into the combustion chambercombustion chamber. . As the piston nears the As the piston nears the bottom of the stroke, the intake valve closes, bottom of the stroke, the intake valve closes, sealing the charge in the combustion chambersealing the charge in the combustion chamber..

Compression StrokeCompression Stroke As the crankshaft rotation continues, the piston is pushed As the crankshaft rotation continues, the piston is pushed

up towards the top of the cylinder, compressing the up towards the top of the cylinder, compressing the airair//fuel mixturefuel mixture. . In modern engines the 'compression In modern engines the 'compression ratio' is about 8 to 1, meaning the entire contents of the ratio' is about 8 to 1, meaning the entire contents of the combustion chamber is compressed into an area of about combustion chamber is compressed into an area of about one eighth of its original sizeone eighth of its original size. . The older stationary engines The older stationary engines had compression ratios in the neighborhood of 4 or 5 to 1had compression ratios in the neighborhood of 4 or 5 to 1. . Generally, the higher the compression ratio, the more Generally, the higher the compression ratio, the more power is obtained from the engine, that is until poor power is obtained from the engine, that is until poor quality andquality and//or low octane values of the fuel begins to have or low octane values of the fuel begins to have an adverse effect on the combustionan adverse effect on the combustion. . This usually causes This usually causes the fuel to the fuel to ""dieseldiesel" " or combust uncontrollably, sometimes or combust uncontrollably, sometimes called Detonationcalled Detonation..

Power StrokePower Stroke Typically, just before the piston reaches its top most position Typically, just before the piston reaches its top most position ((Top Top

Dead Center or TDCDead Center or TDC) ) , the ignition system ignites the now , the ignition system ignites the now compressed aircompressed air//fuel chargefuel charge. . Though, in human terms, this burning Though, in human terms, this burning of the fuel seems more like an instantaneous explosion, it is of the fuel seems more like an instantaneous explosion, it is actually, in a properly running engine, a smooth, rapid flame front actually, in a properly running engine, a smooth, rapid flame front that moves from the source of the ignition that moves from the source of the ignition ((spark plug, ignitor, spark plug, ignitor, etcetc.) .) to all points within the combustion chamberto all points within the combustion chamber. . If the fuel is If the fuel is ignited from several different points due to deposits in the ignited from several different points due to deposits in the combustion chamber, poor quality fuel or engine problems, several combustion chamber, poor quality fuel or engine problems, several flame fronts can be generated and will collide with each other flame fronts can be generated and will collide with each other making what is heard as the common making what is heard as the common ""pingingpinging" " sound, sometimes sound, sometimes called Preignitioncalled Preignition. . The pressure inside the cylinder increases The pressure inside the cylinder increases dramatically because of the combustion taking place and this dramatically because of the combustion taking place and this pressure forces the piston down, which causes the crankshaft to pressure forces the piston down, which causes the crankshaft to rotate providing usable power outputrotate providing usable power output..

Exhaust StrokeExhaust Stroke By the time the piston is forced most of the way By the time the piston is forced most of the way

down the cylinder, nearly all of the usable energy down the cylinder, nearly all of the usable energy created from the burning fuel has been usedcreated from the burning fuel has been used. . At At this point, the exhaust valve begins to open and as this point, the exhaust valve begins to open and as the crankshaft rotation continues, the rising piston the crankshaft rotation continues, the rising piston forces the spent gases out of the cylinder and into forces the spent gases out of the cylinder and into the exhaust systemthe exhaust system. . Just prior to the piston Just prior to the piston reaching TDC, the exhaust valve closes and reaching TDC, the exhaust valve closes and shortly thereafter, the intake valve reopens to start shortly thereafter, the intake valve reopens to start the process overthe process over..

OTTO CYCLEOTTO CYCLE

Otto cycle is the typical cycle for most of the Otto cycle is the typical cycle for most of the cars internal combustion engines, that work cars internal combustion engines, that work using gasoline as a fuelusing gasoline as a fuel. . Otto cycle is exactly Otto cycle is exactly the same one that was described for the fourthe same one that was described for the four--stroke enginestroke engine. . It consists of the same four It consists of the same four major stepsmajor steps: : Intake, compression, ignition and Intake, compression, ignition and exhaustexhaust. .

PV diagram for Otto cyclePV diagram for Otto cycle

v

p

s=c

s=cv=c

v=c

12

3

4

On the PVOn the PV--diagramdiagram, , 1-2 Isentropic Compression stroke1-2 Isentropic Compression stroke . .2-3 Heat addition stroke2-3 Heat addition stroke . .

3-43-4 Isentropic expansion process.Isentropic expansion process.

4-14-1 Heat rejection.Heat rejection. The distance between points 1-2 is the stroke of the The distance between points 1-2 is the stroke of the engineengine. . By dividing V1/V2, we getBy dividing V1/V2, we get: : r=v1/v2r=v1/v2

where r is called the compression ratio of the where r is called the compression ratio of the engineengine. . The efficiency is taken to beThe efficiency is taken to be: :

= 1 – 1

r ( – 1 )K =

CP

CV

Components of 4-stroke engineComponents of 4-stroke engine

11--CYLINDERCYLINDER

The core of the engine is the cylinder, with the The core of the engine is the cylinder, with the piston moving up and down inside the piston moving up and down inside the cylindercylinder. . The engine described above has one The engine described above has one cylindercylinder. .

CYLINDER is made CYLINDER is made from gray cost iron.from gray cost iron.

CYLINDER ARRANGEMENTCYLINDER ARRANGEMENT

In line.In line. V.V. Flat.Flat. Radial.Radial.

((AA ) )Inline -The cylinders are Inline -The cylinders are arranged in a line in a single arranged in a line in a single

bankbank

((BB ) )V V - - The cylinders are The cylinders are arranged in two banks set at an arranged in two banks set at an

angle to one anotherangle to one another

. .((CC ) )Flat Flat - - The cylinders are The cylinders are arranged in two banks on arranged in two banks on

opposite sides of the engineopposite sides of the engine

((DD ) )RadialRadial

ValvesValves -2-2

The intake and exhaust valves open at the The intake and exhaust valves open at the proper time to let in air and fuel and to let out proper time to let in air and fuel and to let out exhaustexhaust. . Note that both valves are closed Note that both valves are closed during compression and combustion so that the during compression and combustion so that the combustion chamber is sealedcombustion chamber is sealed

VALAE is VALAE is made frommade fromalloy steelalloy steel. .

ARRANGEMENT OF VALVESARRANGEMENT OF VALVES

1.1. L-HEADL-HEAD..

2.2. I-HEADI-HEAD..

3.3. F-HEADF-HEAD..

4.4. T-HEADT-HEAD..

L-HEADL-HEAD

The intake and the exhaust valves are The intake and the exhaust valves are both located on the same side of the both located on the same side of the piston and cylinder. piston and cylinder.

I-HEADI-HEAD

The intake and the exhaust valves are The intake and the exhaust valves are both mounted in a cylinder head directly both mounted in a cylinder head directly above the cylinder.above the cylinder.

F-HEADF-HEAD

The intake valves are normally in the head, The intake valves are normally in the head, while the exhaust valves are located in the while the exhaust valves are located in the

engine blockengine block

T-HEADT-HEAD

The intake and the exhaust valves are The intake and the exhaust valves are located on opposite sides of the cylinder located on opposite sides of the cylinder in the engine block, each requires their in the engine block, each requires their own camshaft.own camshaft.

TIMINGTIMING

PistonPiston -3-3

A piston is a cylindrical piece of metal that A piston is a cylindrical piece of metal that moves up and down inside the cylinder.moves up and down inside the cylinder.

The PistonThe Piston is made from cost iron.is made from cost iron.

Piston ringsPiston rings -4-4 Piston rings provide a sliding seal between the outer Piston rings provide a sliding seal between the outer

edge of the piston and the inner edge of the edge of the piston and the inner edge of the cylindercylinder. . The rings serve two purposesThe rings serve two purposes::

They prevent the fuelThey prevent the fuel//air mixture and exhaust in air mixture and exhaust in the combustion chamber from leaking into the the combustion chamber from leaking into the sump during compression and combustionsump during compression and combustion. .

They keepThey keep oiloil in the sump from leaking into the in the sump from leaking into the combustion area, where it would be burned and combustion area, where it would be burned and lostlost. .

Most cars that Most cars that ""burn oilburn oil" " and have to have a quart and have to have a quart added every 1,000 miles are burning it because the added every 1,000 miles are burning it because the engine is old and the rings no longer seal things engine is old and the rings no longer seal things properlyproperly..

)1(Compresssion ring (plain

section)

)2(Compresssion ring(taper

faced)

)3 (Oil control ring steel rail multi piece

Connecting rodConnecting rod--44

The connecting rod connects the piston to the The connecting rod connects the piston to the crankshaftcrankshaft. . It can rotate at both ends so that its It can rotate at both ends so that its angle can change as the piston moves and the angle can change as the piston moves and the crankshaft rotates. The connecting rod is made crankshaft rotates. The connecting rod is made from forged steel or aluminum.from forged steel or aluminum.

55--PISTON PINPISTON PIN

It is used to connect the piston with the It is used to connect the piston with the connecting rod.connecting rod.

Spark plugSpark plug 66--

TheThe spark plugspark plug supplies the spark that ignites supplies the spark that ignites the airthe air//fuel mixture so that combustion can fuel mixture so that combustion can occuroccur. . The spark must happen at just the right The spark must happen at just the right moment for things to work properlymoment for things to work properly

CrankshaftCrankshaft 77--

The crankshaft turns the piston's up and down The crankshaft turns the piston's up and down motion into circular motion just like a crank on motion into circular motion just like a crank on a jacka jack--inin--thethe--box doesbox does. .

BearingBearing is a device supporting a mechanical element and is a device supporting a mechanical element and providing its movement relatively to another element with providing its movement relatively to another element with minimum power lossminimum power loss..

The rotating components of internal combustion engines are The rotating components of internal combustion engines are equipped with sleeve type sliding bearingsequipped with sleeve type sliding bearings..The reciprocating engines are characterized by cycling The reciprocating engines are characterized by cycling loading of their parts including bearingsloading of their parts including bearings. . Such character of Such character of the loads is a result of alternating pressure of combustion the loads is a result of alternating pressure of combustion gases in the cylindersgases in the cylinders..Rolling bearings, in which a load is transmitted by rolls Rolling bearings, in which a load is transmitted by rolls ((ballsballs) ) to a relatively small area of the ring surface, can not to a relatively small area of the ring surface, can not withstand under the loading conditions of internal withstand under the loading conditions of internal combustion enginescombustion engines..Only sliding bearings providing a distribution of the applied Only sliding bearings providing a distribution of the applied load over a relatively wide area may work in internal load over a relatively wide area may work in internal combustion enginescombustion engines..

The sliding bearings used in internal The sliding bearings used in internal combustion enginescombustion engines::

Main crankshaft bearings.Main crankshaft bearings.

Connecting rod bearings.Connecting rod bearings.

Small end bushesSmall end bushes . .

Camshaft bearingsCamshaft bearings . .

1-Main crankshaft bearings.1-Main crankshaft bearings.

Main crankshaft bearingsMain crankshaft bearings support crankshaft providing its support crankshaft providing its rotation under inertia forces generated by the parts of the rotation under inertia forces generated by the parts of the shaft and oscillating forces transmitted by the connecting shaft and oscillating forces transmitted by the connecting rodsrods. . Main bearings are mounted in the crankcaseMain bearings are mounted in the crankcase. . A main A main bearing consists of two partsbearing consists of two parts: : upper and lowerupper and lower. . The upper The upper part of a main bearing commonly has an oil groove on the part of a main bearing commonly has an oil groove on the inner surfaceinner surface. . A main bearing has a hole for passing oil to A main bearing has a hole for passing oil to the feed holes in the crankshaftthe feed holes in the crankshaft. . Some of main bearings may Some of main bearings may have thrust bearing elements supporting axial loads and have thrust bearing elements supporting axial loads and preventing movements along the crankshaft axispreventing movements along the crankshaft axis. . Main Main bearings of such type are calledbearings of such type are called flange main bearingsflange main bearings. .

2-Connecting rod bearings.2-Connecting rod bearings.

Connecting rod bearingsConnecting rod bearings provide rotating provide rotating motion of the crank pin within the connecting motion of the crank pin within the connecting rod, which transmits cycling loads applied to rod, which transmits cycling loads applied to the pistonthe piston. . Connecting rod bearings are Connecting rod bearings are mounted in the Big end of the connecting rodmounted in the Big end of the connecting rod. . A bearing consists of two parts A bearing consists of two parts ((commonly commonly interchangeableinterchangeable((

3-Small end bushes3-Small end bushes

Small end bushesSmall end bushes provide relative motion of provide relative motion of the piston relatively to the connecting rod the piston relatively to the connecting rod joined to the piston by the piston pin joined to the piston by the piston pin ((gudgeon gudgeon pinpin). ). End bushes are mounted in the Small end End bushes are mounted in the Small end of the connecting rodof the connecting rod. . Small end bushes are Small end bushes are cycling loaded by the piston pushed by the cycling loaded by the piston pushed by the alternating pressure of the combustion gasesalternating pressure of the combustion gases. .

Camshaft bearingsCamshaft bearings . .-4-4

Camshaft bearingsCamshaft bearings support camshaft and support camshaft and provide its rotationprovide its rotation

Team work