Four stroke petrol engine,,,,WAHLA

PRESENTATION OF COMMUNICATION SKILLS

Presentation of Thermodynamics

Group leader: M.Bilal YousafGroup Member:1. M. Danish 2. Jahanzaib Afzal3. M. Bilal Yousaf4. M.sanan

Four stroke petrol engine

Four stroke petrol engine

Contents:

1. Introduction of four stroke petrol engine

2. Construction of four stroke petrol engine

3. Working of four stroke petrol engine

4. Applicatio,lubricationof four stroke petrol engine

Introduction of four stroke petrol engine

Engine: An engine is motor

which converts chemical energy into mechanical energy

Fuel/petrol engine: A petrol engine (known

as a gasoline engine in North America) is an internal combustion engine with spark-ignition, designed to run on petrol (gasoline) and similar volatile fuels.

Introduction of four stroke petrol engine

Four stroke engine: A four-stroke

engine (also known as four-cycle) is an internal combustion engine in which the piston completes four separate strokes which comprise a single thermodynamic cycle. A stroke refers to the full travel of the piston along the cylinder, in either direction

Introduction of four stroke petrol engine

Invention: Inventor: Nikolaus Otto Four-stroke engine, Inventor Nikolaus August Otto was the German inventor of the first

internal-combustion engine to efficiently burn fuel directly in a piston chamber.

It was invented in 1876 in Germany by German inventor  Nikolaus August Otto.  In most petrol engines, the fuel and air are usually pre-mixed before compression . The pre-mixing was formerly done in a carburetor, but now it is done by electronically controlled fuel injection, except in small engines where the cost/complication of electronics does not justify the added engine efficiency. it consist of 4 stroke, one cycle complete in 4 stroke of piston and two revolution of crank shaft

Introduction of four stroke petrol engine

Four stroke petrol engine: The cycle of operation in a

four stroke petrol engine is completed in two revolutions of crank shaft or four strokes of piston. Stroke is defined as the distance traveled by the piston from one of the dead centers to the other dead centre. It is also equal to two times the crank radius. Hence in a four stroke engine work is obtained only during one stroke out of the four strokes of the piston required to complete one cycle. This engine works on Otto or constant volume cycle.

Introduction of four stroke petrol engine

Four stroke petrol engine: Working cycle Otto Cycle Fuel used Petrol Fuel Supply Carburetor Ignition Spark plug is required Vibration & noise Less Field of application Light duty work

Construction of four stroke petrol engine

Construction of four stroke petrol engineVarious parts of four stroke petrol engine:

Inlet valve & exhaust valve Piston Piston ring cylinder Connecting rod Crank shaft Crank pin Crank case Spark plug carborator

Various parts of four stroke petrol engine

Inlet valve & exhaust valve

Inlet valve: its function is to

intake the fresh air-fuel mixture into the cylinder

Exhaust valve: its function is to

exhaust is the burnt gases by the force of piston

Various parts of four stroke petrol engine

Piston: Piston is a

connected to the crankshaft through the connecting rod when piston moves downward sucks fresh air and fuel mixture in suction stroke and ignited inside the cylinder due to the high temperature and pressure generated thus the expand force down the piston.

Various parts of four stroke petrol engine

Piston ring: A piston

ring is an open ended ring that fits into a grove or a groove our outer diameter of the cylinder. Piston ring have three major functions which are seal the expansion chamber support heat transfer and finally regulate the engine oil consumption.

Various parts of four stroke petrol engine

Connecting rod: A small end of connecting

rod is connecting to the piston and other end is connecting to the crankshaft. Its function is to transmit reciprocating motion of piston to the rotary motion of crankshaft .gudgeon pin is used to connect the piston and connecting rod

Various parts of four stroke petrol engine

Crank pin: Crank case

In a reciprocating engine, the crankpins, also known as crank journals are the journals of the big end bearings, at the ends of theconnecting rods opposite to the pistons.

In an internal combustion engine of the reciprocating type, the crankcase is the housing for the crankshaft.

Various parts of four stroke petrol engine

Carborator: Spark plug:

is a device that blends air and fuel for an internal combustion engine.

Is used in petrol engine only which is help to ignite the air-fuel mixture for combustion.

Working principle four Stroke Engine

Following are the four strokes1 – Intake/Suction stroke2 – Compression stroke3 – Expansion stroke4 – Exhaust stroke

1 – Intake stroke

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In suction stroke piston starts at Top Dead Center (TDC) of the cylinder and moves to the Bottom Dead Center (BDC). Outlet valve will be closedand inlet valve will be open to allowing the fresh charge of mixed fuel & air into the cylinder.

2 – Compression stroke

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In compression stroke,Once piston reaches BDC & moves back TDC,inlet valve will be closed,As the piston moves towards TDC,It compress air fuel mixture inside the cylinder & compression takes place,Hence it is called compression stroke.

3 – Expansion stroke

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In expansion stroke,Both the valves are closed,When piston reaches top of its stroke the fuel mixture is ignited by spark plug due to spark high temperature & pressure generated inside the cylinder & push down the piston to BDC,Hence it is known as expansion stroke.

4 – Exhaust stroke

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In this stroke exhaust valve is opened,when piston reaches to BDC & moves to upward.Piston pushes out the burnt gases to the atmosphere through the exhaust valve. Hence called exhaust stroke & the engine is ready to begin the cycle again.

Working principal of four stroke petrol engine

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The four stroke version is generally used for larger applications and is the most common type of engine used in automobiles today.

This type of engine is an ingenious and practical design that has powered millions of vehicles. It produces a large amount of power in an efficient and effective manner. It also generally produces less pollution and lasts longer than a two stroke engine. The engine was created by Nikolas Otto in the mid 1800s, and in his honor, it's sometimes known as the Otto Engine. The four main strokes or steps that make up the cycle are intake, compression, combustion, and exhaust, which is sometimes called the Otto cycle.

Applications of Four stroke engine:-

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Four-Stroke lubricationFour-stroke engines are lubricated by oil held in an oil sump. The oil is distributed through the engine by splash lubrication or a pressurized lubrication pump system; these systems may be used alone or together.

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SPLASH LUBRICATION:-

Splash lubrication is achieved by partly submerging the crankshaft in the oil sump. The momentum of the rotating crankshaft splashes oil to other engine components such as the cam lobes, wrist pins and cylinder walls.

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PRESSURIZED LUBRICATION:-

Pressurized lubrication uses an oil pump to provide a pressurized film of lubricant between moving parts such as the main bearings, rod bearings and cam bearings. It also pumps oil to the engine’s valve guides and rocker arms.

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Difference between4-Stroke Engine & 2-Stroke Engine

• One cycle completed in every 2 revolution of crankshaft

• More moving parts

• More maintenance

• Heavy in weight• More expensive

• One cycle completed in every revolution of crankshaft

• Less moving parts

• Less maintenance

• Light in weight• Less expensive

4-Stroke Engine

2-Stroke Engine

Difference between4-Stroke Engine & 2-Stroke

Engine

• Produce more pollution

• Long engine life• Not required

• Complex design

• Less pollution

• Short engine life• Required a mix of

oil to lubricate the crankshaft

• Simpler design

4-Stroke Engine

2-Stroke Engine