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Cylinder head design, combustion & emission (petrol)
Transcript of Cylinder head design, combustion & emission (petrol)
Principle of combustion chamber Designs
Inlet valves should be as large as it could be to improve volumetric efficiency
The flame travel should be as short as possible to evade detonation
Hot spots can cause pre ignition and must be avoided by providing cool and proper positioning of the spark plug and exhaust valve.
To ensure the velocity of the flame propagation is at its highest; optimum degree of turbulence should be present .
Cooling has to be optimum to reduce the risk of material failure.
Surface to volume ratio must be low so loss of heat it avoided and obtain a high thermal efficiency.
Cylinder Head Design
Cylinder heads are designed:
Improves the swirl or turbulence of the air-fuel mixture.
Prevents fuel droplets settling on the surfaces of the combustion chamber or cylinder walls.
Types of combustion chamber
pent - roof
The name has been derived from its shape, which has been likened to an inverted bathtub.
The spark plug is located on one side.
The valves are usually vertical in the cylinder head and are in-line.
A short flame path from the spark-plug is produced.
Simple valve-operating mechanism is able to be used.
Turbulence in the combustion chamber is assisted by the shape of the chamber and the small cross section in the chamber.
The spark plug is located at the wide part of the wedge.
Spark plug is usually positioned midway between the valves.
Inline valves are normally tilted to accommodate the sloping roof of this design.
Thoroughly mix the air and fuel before combustion.
Efficient combustion and reduces detonations.
Flame front moves evenly.
Allows rapid and even combustion.
presented by kendrick james and kevin salim
Pent - Roof type
Intake and exhaust valve heads face in opposition to one another, forming a “V” shape.
The configuration allows for 4 or more valves per cylinder.
The spark plug is located in the center of the valves.
Less heat is lost.
Flame front travelling distance is short.
Variable valve timing
To alter engine characteristics as required to optimize performance and economy under different driving conditions.
vvti (toyota) type