08-11-2012, 04:31 PM
Two Stroke engines & Four stroke engines
1Two Stroke engines.pptx (Size: 398.08 KB / Downloads: 40)
Engine
A device which convert heat energy in to mechanical energy to obtain some power is called an engine.
TYPES OF AN ENGINE
There are two types of an engine.
Internal Combustion Engine(I.C. Engines)
External Combustion Engine(E.C. Engines)
Internal Combustion Engine(I.C. Engines)
The engines in which combustion takes place inside the engine as in the cylinder are called as I. C. Engines e.g.; Petrol Engine, Diesel Engines.
External Combustion Engine(E.C. Engines)
The engines in which combustion takes place outside the engine as in boilers are called as E.C. Engines e.g.; Steam Engines.
Compression Ignition Engines
These are diesel engines in which the air only is compressed, and the fuel is injected into the air which is then at a sufficiently high temperature to initiate combustion.
Two Stroke Petrol Engines
The two stroke cycle is so called because it takes two strokes of the piston to complete the processes needed to convert the energy in the fuel into work.
Because the engine is reciprocating, this means that the piston must move up and down the cylinder, and therefore the crankshaft must revolve once. The air and fuel(Petrol or CNG) are mixed before compression.
Four Stroke Petrol Engines
The four strokes refer to intake, compression, combustion (power), and exhaust strokes that occur during two crankshaft rotations to complete the processes needed to convert the energy in the fuel into work.
Working of Four Stroke Petrol Engines
Intake Stroke
On the intake or induction stroke of the piston , the piston descends from the top of the cylinder to the bottom of the cylinder, reducing the pressure inside the cylinder. A mixture of fuel and air is forced by atmospheric (or greater) pressure into the cylinder through the intake port. The intake valve(s) then close.