State whether following statement is true or false and justify: Swirl instead of turbulence is required inside CI engine combustion chamber.

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written 9.5 years ago by

teamques10 ★ 70k

The statement is true. Both SI and CI engines require air motion in the form of turbulence and swirl respectively.
Turbulence in SI engines is characterized by disordered motion of air without any general direction of flow. This motion breaks up the surface of flame front and distributes flame throughout an externally prepared combustible mixture.
In CI engines the fuel air mixture formed in combustion chamber is essentially heterogeneous due to non-uniform distribution of injected fuel droplets. Because of these conditions, if the air in cylinder remains motionless, only a small portion of fuel would get sufficient oxygen and even burning of this fuel would be slow or choked.
Also it is important to provide proper mixing of fuel and air in shortest possible time. For this purpose an organized air movement is required to produce high relative velocity between fuel droplets and air and not just turbulence.
So it is necessary to impart swirl to air. The swirl in CI engines is an orderly movement of air with a particular flow direction to provide a continuous supply of fresh air to each burning fuel droplet and also sweep away the products of combustion.

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