162 Open period gas exchange process

This has already been discussed qualitatively in section 1.5.2. The calculation technique again involves the solution of appropriate differential equations on a step-by-step basis. The main difference between the calculations for the closed and open period is that the non-flow energy eqn (1.42) is now replaced by the unsteady flow energy equation which allows for inflows and outflows of gas to and from the cylinder.

The gas exchange process, like the combustion process, is associated with major changes in the composition of the cylinder charge, but these are now connected with the incoming mass increment dmin (usually pure air) and outgoing mass increment dmex (usually products of combustion) each of known compo-

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