How does an automobile engine work?

How does an automobile engine work?


An “Automobile Engine” is an “Internal Combustion Engine”(ICE). In this engine, energy is created by burning either petrol or diesel in a combustion chamber. The burnt gases expand and with pressure move a piston in a linear motion.  The linear motion of the piston is then converted into a rotary motion through the crankshaft and axle. The axle turns the wheels and makes the car move forward.

Almost all cars currently use what is called “A Four Stroke Combustion Cycle” to convert fuel into motion. The Four Stroke Approach is also known as the “Otto Cycle”, in honor of “Nikolaus Otto”, who invented it in 1867. The four strokes are illustrated in fig. They are - Intake Stroke, Compression Stroke, Combustion Stroke and Exhaust Stroke.

The Strokes:

Intake Stroke: The Piston starts at the top, the intake valve opens and the piston moves  down to let the engine take in (suck) a mixture of air and petrol (only  air in case of a diesel engine as the injectors inject the diesel through a different mechanism). This is “Intake Stroke”. Only the tiniest drop of gasoline needs to be mixed into the air for this to work.

Compression Stroke: Then the piston moves back up to compress this fuel/air mixture. Compression makes the explosion more powerful.

Combustion Stroke: When the piston reaches the top of its stroke,i.e. second rotation of crankshaft  the spark plug emits a spark to ignite the fuel. The fuel charge in the cylinder explodes. The pressure created from this combustion pushes the piston down. In the case of a diesel engine during this phase diesel is injected into the cylinder.

Exhaust Stroke: Once the piston hits the bottom of its stroke, the exhaust valve opens and by-products of combustion leaves the cylinder to go out the tail-pipe.

Basic Engine Parts are:

1. Cylinder: It is core of the engine. The engine described above has a one cylinder. But most cars have More than one cylinders arranged in horizontally opposed way.

2. Spark Plug: It supplies spark that ignites the air/fuel mixture so that combustion can occur. The  Spark must happen at just the right moment for things to work properly.

3. Valves: The intake and exhaust valves open at the proper time to let in the air/fuel and to let out Exhaust. Both valves are closed during compression and combustion so that the Combustion chamber is sealed.

4. Piston: It is a cylindrical piece of metal that moves up and down inside the cylinder.

5. Piston Rings: These provide a sliding seal between the outer edge of the piston and the inner edge of the cylinder that prevents the air/fuel mixture and exhaust in the combustion chamber from leaking into the sump during compression and combustion. They keep oil in the sump from leaking into the combustion area where it would be burnt & lost.

6. Connecting Rod: It connects the piston to the crankshaft.

7. Crankshaft: It turns the piston’s linear motion into circular motion.

8. Sump: It surrounds the crankshaft. It contains some amount of oil, which collects in bottom.