Presentation on theme: "Four Stroke Gas Engines"— Presentation transcript:
1Four Stroke Gas Engines The four strokes of a internal combustion engine are:IntakeCompressionPowerExhaustEach stroke = 180˚ ofcrankshaft revolution.Each cycle requires two revolutionsof the crankshaft (720˚ rotation), andone revolution of the camshaft to complete(360˚ rotation).
2Intake Stroke First Stroke The piston moves down the cylinder from TDC (Top Dead Center) to BDC(Bottom Dead Center).This movement of piston causes lowair 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.
3Compression stroke Second stroke The piston moves from BDC to TDC Intake and exhaust valves stay closedAir and fuel mixture is compressed8:1 to 12:1The pressure in the cylinder is raised
4Power stroke Third stroke At the end of compression stroke the sparkplug fires, igniting the air/fuelmixture.Both the valves stay closed inthis stroke.The expanding gases from thecombustion in the cylinder(with no escape) push the pistondown.The piston travels from TDC to BDC.
5Exhaust stroke Fourth and last stroke The momentum created by the Counter-weights on the crankshaft,move the piston from BDC to TDC.The exhaust valve opens andthe burned gases escape into theexhaust system.Intake valve remains closed.
8Valve Timing The ratio of cam to crank sprocket is 2:1 For every two revolutions ofCrankshaft, the Camshaft turns once.Chain drivenBelt drivenGear driven
9Carburetor The job of the carburetor is to accurately meter extremely tinyquantities of fuel and mix it withthe air entering the engine, so thatthe engine runs properly.It works on the principle ofHigh and low pressureHigh and low pressure is createdwith the help of Venture
10Ignition systemProvides high voltage surges – as high as 47,000 volts to the spark plugPartspermanent magnet.armature assembly.breaker points.condenser.spark plug.
11LubricationIn the engine, dippers on the connecting-rod bearing caps enterthe oil pan with each crankshaft revolution to produce the oil splash.A passage is drilled in each connecting rod from the dipper to thebearing to ensure lubrication.(used only on 4-stroke small engines)
12Cooling Air cooled Fins are used to dissipate heat Liquid cooled Coolant is used to dissipate heat.