INTRODUCTION OF FOUR STROKE 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.

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.

FOUR STROKE ENGINE

Four stroke cycle engine s is working at completed four stroke of thepiston or two revoluation of the crank shaft it is called as four strokeengine

It is two types of valves is presented these are

Inlet valve

Exhaust valve

Four stroke petrol engine working at the four types of stroke

Suction stroke

Compression stroke

Power stroke or expansion stroke

Exhaust stroke

OTTO CYCLEIn 1862 a German engineer NikolausAugustus Otto began experimenting with different kinds of engines.

His first experiment was conducted on a 4-stroke engine. 10 years later he introduced to the world the Otto engine.

The 4-stroke engine consists of a 4-stroke cycle better known as the Otto cycle.

OTTO CYCLE PROCESS

OTTO CYCLEEach movement of the cylinder up or down the cylinder is one stroke of the four stroke combustion cycle or Otto cycle.

The four stroke cycle consists of

- induction stroke - compression stroke - ignition/power stroke - exhaust stroke

A single cycle requires two revolutions of the crankshaft to complete.

SUCTION STROKE

Suction Stroke (Intake) : During a suction stroke the piston moves downward by the engine crankshaft either by the momentum of flywheel and or the electric motor or the starter motor. During this stroke piston moves downward and creates a vaccum inside the combustion chamber. Inlet valve (Intake valve) opens during this stoke allowing the air fuel mixture to enter the combustion chamber. Here the fuel is petrol mixed with air broken up into a mist and partially vaporized in the carburettor

COMPRESSION STROKE

Compression Stroke : During this stroke piston moves upward and compresses the charge. The heat produced by the compression makes more homogeneous mixture of air and petrol inside the cylinder. This heat makes it easier to burn. During this stroke both valves remain closed.

POWER OR EXHAUST STROKE

During this stroke the mixture under compression is ignited by the spark that is produced by a spark plug. The expansion of the gases due to heat of the combustion creates a pressure on the piston and the cylinder walls. During this stroke piston moves downward. Both valves remain closed during this stroke.

EXHAUST STROKE

During this stroke the inlet valve remains closed and the exhaust valve remains open. During this stroke piston moves upward and pushes the burnt gases out through exhaust valve. Only a small amount of exhaust gases remain in the clearance space which gets diluted with the fresh incoming charge during a next suction stroke.In this type of engine four strokes of piston are required to complete the cycle.. Four strokes make two revolutions of the crankshaft. Each alternative revolution of the crankshaft has one power stroke. A power stroke consist of above mentioned cycles.

ADVANTAGES OF

FOUR STROKE

PETROL ENGINE

• Less fuel consumption.

• Thermal efficiency is more.

• More volumetric efficiency.

• Less wear and tear.

DISADVANTAGES OF

FOUR STROKE PETROL

ENGINE

• More components.

• Separate valve mechanism is required.

• More cost.

• More complicated design.

APPLICATIONS OF FOUR STROKE PETROL ENGINE:

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.

DIFFERENCE BETWEEN 4 STROKE AND

2 STROKE PETROL ENGINE

FOUR STROKE ENGINE

One cycle completed in every 2 revolution of crankshaft

More moving parts

More maintenance

Heavy in weight

More expensive

Produce more pollution Long engine life Not required Complex design

TWO STROKE ENGINE One cycle completed in every

revolution of crankshaft

Less moving parts

Less maintenance

Light in weight

Less expensive

Less pollution

Short engine life

Required a mix of oil to lubricate the crankshaft

Simpler design