Wednesday, December 4, 2013

Direct injection


Direct injection:-

With direct injection, the fuel is injected directly into the combustion chamber which is usually formed by a cavity in the piston crown.

This cavity is carefully shaped to promote air swirl and the direction of the injector nozzle ensures that rapid mixing of the fuel and air assists complete combustion.

Advantages - It is claimed that direct injection gives higher thermal efficiency with lower fuel consumption. This is bought about by the fact that no heat is lost or power wasted in pumping air through a restricted opening into the separate chamber or in discharging the gases from the chamber. This gives easier starting and generally this type of engine does not require a starting aid device, such as glow plugs.

Disadvantages - This kind of injection is prone to “diesel knock”.
 

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