Carburetor

Carburetor, device that mixes air and gasoline in the correct proportion for efficient combustion (about 15:1 by weight) in internal combustion engines (as in automobiles). In its simplest form a carburetor is a tube that is constructed at one point into a narrow throat or venturi. As air flows through the venturi, it speeds up and its pressure decreases. Gasoline from a reservoir (the float chamber) is piped to the venturi and sucked into the airstream. The fuel mixture then passes through a “butterfly” throttle valve into the engine cylinders. The throttle valve controls the rate at which the fuel mixture enters the engine and therefore the engine speed. A butterfly choke valve is fitted in the air intake to the carburetor to cut off the air supply when the engine is started from cold.

See also: Gasoline engine.