The combustion chamber is the area inside the engine where the fuel-air mixture is compressed and ignited. It is located between the cylinder head and the piston. Different combustion chamber designs include hemispherical, wedge-shaped, and bathtub chambers. The shape of the chamber affects power, efficiency, and emissions by influencing factors like fuel-air mixing, flame propagation, and heat transfer.

1. Combustion Chamber

2. Combustion chamber in piston

3. COMBUSTION CHAMBER
 A combustion chamber is the part of an engine in which
fuel is burned.
 The combustion chamber is the area inside the engine
 where the fuel/air mixture is compressed and then
ignited.
 It is generally formed on one side by the shape cast into
the cylinder head,
 and on the other side by the top of the piston.

4.  The combustion chamber is recessed in the cylinder head
and commonly contains a single intake valve and a single
exhaust valve.
When the piston is at top-dead-center the chamber is at its
smallest dimension, and this is the time
 when the fuel/air mixture is at its most unstable condition
and ready to be ignited.
 The better the combustion chamber is designed the better
the engine "breathes;"
 that is, the more efficient the overall flow of air through
the engine

5.  The hot gases produced by the combustion occupy a far
greater volume than the original fuel,
 Thus creating an increase in pressure within the limited
volume of the chamber.
 This pressure can be used to do work,
 For example, to move a piston on a crankshaft or a
turbine disc in a gas turbine.
 The energy can also be used to produce thrust when
directed out of a nozzle as in a rocket engine.

6.  The shape of the chamber has a marked effect on power
output, efficiency and harmful emissions
 The intake valve/port is usually placed to give the
mixture a pronounced "swirl" (the term is preferred to
turbulence which implies movement without overall
pattern) above the rising piston,
 improving mixing and combustion.
The shape of the piston top also affects the amount of
swirl.

7.  Finally, the spark plug must be situated in a position
from which the flame front can reach all parts of the
chamber at the desired point,
 usually around 15 degrees after top dead centre
 Various shapes of combustion chamber have been used,

8. Combustion chamber types.
 Hemispherical or Pentroof Combustion
Chamber
 Wedge-Shaped Chambers
 Bathtub or Heart-shaped Combustion Chamber

9. Hemispherical or Pentroof Combustion
Chamber

11. Hemispherical or Pentroof Combustion
Chamber
 Hemispherical combustion chamber is one half of
a sphere cast into the bottom of the cylinder head.
 The valves are placed at the outside of the bore
area,
 and at a specific angle from the crankshaft
centerline.
 Hemispherical chambers generally have a central
spark plug, which offers excellent octane tolerance.

12.  This creates a more efficient cross-flow movement of the
charge during valve overlap and limits thermal transfer
from the exhaust valve to the fresh charge.
 This design offers the best surface-to-volume ratio and
also creates a very short direct exhaust port, essential in
limiting heat rejection into the coolant.
 An additional benefit is the distance between the intake
and exhaust valves, which further limits heat transfer.

13. Wedge-Shaped Chamber

15. Wedge-Shaped Chamber
 This type of chamber resembles an inclined basin
recessed into the deck of the head.
 The spark plug is located on the thick side of the wedge
and is usually positioned midway between the valves.
 The relatively steep walls in such chamber design force
the air/fuel flow path and deflect .
 and force it to move in a downward spiral around the
cylinder axis.

16.  During the compression stroke, the compressed air/fuel
area reduces
 To such an extent that the trapped mixture is violently
thrust from the thin to the thick end of the chamber.
 This builds up significant kinetic energy, which when
ignited contributes to overall power.

17. Bathtub combustion chamber

19. Bathtub combustion chamber
This is formed in the cylinder head and has two vertical
valves and a side- mounted spark plug.
 Mixture in the squish’ area between the piston and the
flat face of the head provides some turbulence within the
mixture,
 Air is pushed into combustion space provided air
movement known as squish.
 which helps it burn smoothly.

20.  Some bathtub chambers have a shaped
projection between the valves,
 giving the chamber a heart-shaped plan view.
 This swirls the incoming mixture, helping to
atomize it further.

21. Thanks