Stroke

Swedish College of Engineering & TechnologyLab Incharge : Engr.Shah Nawaz

Department : Mechanical

Semester : 3rd

Topic : 2 Stroke Petrol Engine

Subject Name : Thermodynamics-2Active Learning assignment

Prepared by:NameShahzaib AkhtarHassan Abbas Niazi Abdullah SaddiqEnrollment no.14F-UET-ME-01314F-UET-ME-01414F-UET-ME-012

Presentation Topic-Two Stroke Engine

StrokeReciprocating motion used in reciprocating engines and other mechanisms is back and fourth motion .Each cycle of reciprocation consists of two opposite motions , there is a motion in one direction and then a motion back in the opposite direction . Each of this motion is called stroke.

2 stroke A two-stroke petrol engine is an internal combustion engine that completes the process cycle in one revolution of the crankshaft . Thus one power stroke is obtained in each revolution of the crank shaft.

Basic parts of 2-stroke petrol engine

Piston Piston RingSpark plugConnecting rodCrankshaft

Spark PlugElectronic match is used to begun the combustion process of burning air and petrol to create heat.It provides the means of ignition when the petrol engines piston is at the end of compression stroke close to Top Dead Central (TDC)

Connecting rod Connects the piston and piston point to the crankshaft

Piston A sliding plug that harness the force of the burning gases in the cylinder

Crankshaft Along the piston pin and the connecting rod is converts the up and down motion ( reciprocating ) of the engine to spinning (rotary) motion

Working & parts of 2-StrokeAs the name itself implies, all the processes in the two stroke cycle engine are completed in two strokes. These engine have 1 power stroke per revolution of the crankshaft.

In the two stroke engine there is a two opening called ports are provided in place of valve of four stroke engines.

These ports are opened and closed by reciprocating motion of the piston in the cylinder.

One port known as a inlet port and another port is known as a exhaust port.

Two stroke engine consist of a cylinder with one end fitted with a cylinder head and other end fitted with a hermitically sealed crankcase which enables it to function as a pump in conjuction with the piston.Transfer portCrank caseExhaust port

Working Principle of 2 stroke Here suction and exhaust strokes are eliminated . Instead of valves , ports are used.The exhaust gases are driven out of the cylinder by the fresh fuel entering the cylinder.The intake & exhaust are controlled by movement of piston.The fresh fuel enter to cylinder due to difference of pressure.The fuel is compressed by the pumping action of the piston due to the design of crankcase.As the piston continues to move upward , exhaust and transfer port get closed and the compression is continued.In the end of the compression the spark is created which ignites the fuel & in result of combustion thrust the piston moves from TDC to BDC.

This cycle is repeated continuously

Video clips.

Advantages The power developed will be nearly twice that of four stroke engine of same dimension and operating at the same speedThe work required to overcome the friction of the exhaust and suction strokes is saved Low weight Construction is simple Low thermal efficiency.Can run at higher speeds (5000 rpm)Low maintenance cost

Disadvantages As working on otto-cycle , a part of the fresh mixture is lost through exhaust portPart of the piston stroke is lostHeavy consumption of lubricating oil Two-stroke engines are not fuel efficient, so we would get fewer miles per gallon.

Use of 2-stroke engineDirt Bike Lawn mowersOutboard enginesChain sawsLine TrimmersJet SkisSnowmobilesModel Air PlanesLight MotorcyclesGo KartsUltra lightsScooters

Go-Karts

Example picture-

Dirt Bike Jet SkisChain sawsLawn mowers