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Carburetion Principles

 Carburation Principles

Venturi Principles

  • The carburetor must measure the airflow through the induction system and use this measurement to regulate the amount of fuel discharged into the airstream.
  •  The air measuring unit is the venturi, which makes use of a basic law of physics: as the velocity of a gas or liquid increases, the pressure decreases.
  •  simple venture is a passageway or tube in which there is a narrow portion called the throat. As the velocity of the air increases to get through the narrow portion, its pressure drops.
  • Note that the pressure in the throat is lower than that in any other part of the venturi. This pressure drop is proportional to the velocity and is, therefore, a measure of the airflow.
  • The basic operating principle of most carburetors depends on the differential pressure between the inlet and the venturi throat.

Application of Venturi Principle to Carburetor

  • The carburetor is mounted on the engine so that air to the cylinders passes through the barrel, the part of the carburetor which contains the venturi.
  • The size and shape of the venture depends on the requirements of the engine for which the
  • carburetor is designed.
  •  A carburetor for a high-powered engine may have one large venturi or several small ones. The
  • air may flow either up or down the venturi, depending on the design of the engine and the carburetor.
  • Those in which the air passes downward are known as downdraft carburetors, and those in which the air passes upward are called updraft carburetors.
  • Some carburetors are made to use a side draft or horizontal air entry into the engine induction system.


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