PRINCIPLES GASOLINE/DIESEL FUEL SYSTEMS - OD1620 - LESSON 2/TASK 2
b. Precombustion Chamber (figure 40). The precombustion chamber is an
auxiliary chamber at the top of the cylinder. It is connected to the main
combustion chamber by a restricted throat or passage. The precombustion
chamber conditions the fuel for final combustion in the cylinder. A
hollowed out portion of the piston top causes turbulence in the main
combustion chamber as the fuel enters from the precombustion chamber to aid
in mixing with air. The following steps occur during the combustion
process:
(1) During the compression stroke of the engine, air is forced into
the precompression chamber and, because the air is compressed, it is hot.
At the beginning of injection, the precombustion chamber contains a definite
volume of air.
(2) As the injection begins, combustion starts in the precombustion
chamber. The burning of the fuel, combined with the restricted passage to
the main combustion chamber, creates a tremendous
FIGURE 40. PRECOMBUSTION CHAMBER.
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