Combustion chamber designs

Layout of valves and form of combustion chamber :

As we have mentioned before about cylinder head that it holds intake and exhaust valves or ports ,
So it have many design according to positioning valves and form of combustion chamber.

Cylinder head design should help the improve
of Swirl or Turbunlence of the air fuel mixture
and prevents fuel droplet set onto piston surface
or cylinder wall .

When air fuel mixture is compressed between
The piston and the flat part of the cylinder head
,it produces which called squish which mean
squeezing of the gases to increase it's velocity
and turbunlence.

Combustion is alwayes take place within
a turbulent flow field for two reasons :

* turbunlence increases the mixing process
and enhance combustion , but at the same
time
* flow instability generated by combustion released heat through gas expansion and buoyancy ,
thus enhancing the transtion to turbulence .

Layout of valves and form of combustion chamber :

In petrol engines the three most combustion chamber designs are

* Hemispherical

* Bath - tub

* Wedge

Hemispherical cylinder head design :

                                               Hemispherical cylinder head design

It have the Intake valve in one side of the combustion chamber and the exhaust valve at the other, and this produces cross flow, positioning valves in this way help the engine breath.

When fuel starts to burn at the Spark plug the flame start to travel in all directions and this called
Flame propagation .

When the plug in the middle of the hemisphere start to ignite the flame have less distance to travel than other design and this give rapid and effective combustion , so this design is common in a lot of passenger
vehicles.

Bath - tub cylinder head design   :

The bath - tub combustion chamber is over-shaped like inverted bath - tub , Valves are mounted vertically and side by side which make it simple to operate.

The plug is one side and that creat a short flame path, it all help to increase turbulence.

                                             Bath - tub cylinder head design