four stroke gas engines
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DEPARTMENT OF MECHANICAL ENGINEERINGDEPARTMENT OF MECHANICAL ENGINEERING MUTHAYAMMAL ENGINEERING MUTHAYAMMAL ENGINEERING
COLLEGE,RASIPURAM.COLLEGE,RASIPURAM. Presented byPresented by
A.KALAIYARASAN A.KALAIYARASANAssistant Professor ,MEC –Rasipuram Assistant Professor ,MEC –Rasipuram
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Four Stroke Gas EnginesFour Stroke Gas EnginesThe four strokes of a internal combustion engine are:
•Intake•Compression
•Power•Exhaust
Each cycle requires two revolutions of the crankshaft (720˚ rotation), and one revolution of the camshaft to complete(360˚ rotation).
Each stroke = 180˚ of crankshaft revolution.
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Intake StrokeIntake StrokeFirst Stroke
The piston moves down the cylinderfrom TDC (Top Dead Center) to BDC (Bottom Dead Center).
This movement of piston causes low air pressure in the cylinder (vacuum)
Mixture of Air and Fuel in the ratioof 14.7 : 1 (air : fuel) is drawn intothe cylinder.
Intake valve stays open and theExhaust valve stays closed duringthis stroke.
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Compression strokeCompression strokeSecond stroke
The piston moves from BDC to TDC
Intake and exhaust valves stay closed
Air and fuel mixture is compressed8:1 to 12:1
The pressure in the cylinder is raised
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Power strokePower strokeThird stroke
At the end of compression strokethe sparkplug fires, igniting the air/fuelmixture.
Both the valves stay closed in this stroke.
The expanding gases from the combustion in the cylinder(with no escape) push the pistondown.
The piston travels from TDC to BDC.
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Exhaust strokeExhaust strokeFourth and last stroke
The momentum created by the Counter-weights on the crankshaft,move the piston from BDC to TDC.
The exhaust valve opens and the burned gases escape into theexhaust system.
Intake valve remains closed.
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Four strokesFour strokes
All four strokes
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Four Cylinder EngineFour Cylinder Engine
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Valve TimingValve Timing
The ratio of cam to crank sprocket is 2:1
For every two revolutions of Crankshaft, the Camshaft turns once.
Belt driven
Chain driven
Gear driven
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Carburetor Carburetor The job of the carburetor is to accurately meter extremely tiny quantities of fuel and mix it with the air entering the engine, so thatthe engine runs properly.
It works on the principle of High and low pressure
High and low pressure is created with the help of Venture
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Ignition systemIgnition systemProvides high voltage surges – as high as 47,000 volts to the spark plug
Parts• permanent magnet. • armature assembly. • breaker points. • condenser. • spark plug.
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LubricationLubricationIn the engine, dippers on the connecting-rod bearing caps enter the oil pan with each crankshaft revolution to produce the oil splash.A passage is drilled in each connecting rod from the dipper to the bearing to ensure lubrication.(used only on 4-stroke small engines)
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CoolingCoolingAir cooledFins are used to dissipate heat
Liquid cooledCoolant is used to dissipate heat.