Roll No:14ME112

Syed Ashraf Ali Shah Rizvi

Mehran UET, Jamshoro

Department of Mechanical Engineering

What is an Engine?An ENGINE is a machine used to convert HEAT ENERGY into MECHANICAL ENERGY.

PETROL ENGINE

PETROL ENGINEA petrol engine (known as a gasoline engine) is an INTERNAL COMBUSTION engine with the spark ignition. So it is also known as spark ignition engine(S.I. Engine).

Fuel used In a petrol engine is a gasoline ( Petrol ) and similar volatile fuel.

The petrol engine works on principle of theoretically OTTO CYCLE.

OTTO CYCLEAn OTTO cycle is an idealized thermodynamic cycle that describes the functioning of a typical spark ignition piston engine. It is the thermodynamic cycle most commonly found in automobile engines.

There are TWO types of Petrol Engines

- 4 STROKE PETROL ENGINE.

- 2 STROKE PETROL ENGINE.

4 STROKE PETROL ENGINE

A FOUR STROKE PETROL ENGINE shown in figure.

The valve operating the inlet is called inlet valve and the valve operating the exhaust is called exhaust valve. The spark plug fitted at the top of cylinder head initiates the ignition of the air fuel mixture.

The piston performs four stroke to complete one working cycle. The four different strokes are;

Suction stroke

Compression stroke

Power stroke

Exhaust stroke

INTAKE STROKEINTAKE VALVE OPEN

EXHAUST VALVE CLOSED

PISTON GO TO TDC TO BDC

AIR-FUEL MIXTURE ENTER IN TO THE CYLINDER

COMPRESSION STROKE INTAKE VALVE CLOSED

EXHAUST VALVE CLOSED

PISTON GO TO BDC TO TDC

AIR-FUEL MIXTURE COMPRESSED IN TO THE CYLINDER

POWER STROKEINTAKE VALVE CLOSED

EXHAUST VALVE CLOSED

AIR-FUEL MIXTURE BURN INTO THE COMBUSTION CHAMBER

PISTON GO TO TDC TO BDC

EXHAUST STROKEINTAKE VALVE CLOSED

EXHAUST VALVE OPEN

PISTON GO TO BDC TO TDC

EXHAUST GAS OUT THROUGH THE EXHAUST VALVE

THE WORKING OF 4 - STROKE PETROL ENGINE.

Exhaust valve Inlet valve

Petrol and air mixtureExhaust gases TDC

BDC

Spark plug

TWO STROKE PETROL ENGINE

• As the name itself implies, all the processes in two stroke cycle engine are completed in two strokes.

In two stroke engine cycle operations suction , compression , expansion and exhaust are completed in one complete revolution.These engines have one power stroke per revolution of the crank shaft.Two-stroke engines do not have valves, which simplifies their construction and lowers their weight.

Major parts •CYLINDER•PISTON•CRANK SHAFT •ENGINE VALVE •CONNECTING ROD•CAM SHAFT•SPARK PLUG

Cylinder in the ENGINE is

Piston in the ENGINE is

Crankshaft in the ENGINE is

Engine valve in the ENGINE is

Connecting rod in the ENGINE is

Camshaft in the ENGINE is

Spark Plug in the ENGINE is

Advantages of Petrol engine High engine speeds of about 3000 rpm.

Lighter in a weight because maximum pressure and temperature is less.

Less initial cost.

Less maintenance cost.

Disadvantages of Petrol engine

low compression ratio ranging from 6 to 10.

The thermal efficiency is lower due to lower compression ratio.

Running cost higher because petrol is costly.