Untitled - Aerobib - Universidad Politécnica de Madrid

Chapter 5
Structure of the combustion
waves
5.1 Introduction
The different types of combustion waves compatible with the principles of the conservation
of mass, momentum and energy throughout the wave have been previously
established in chapter 4. Table 4.1 of that chapter summarizes the results of the said
analysis. These results where attained simply by comparing the initial and final state
of the gases. The conclusions are correct provided that the wave thickness is small
enough, so that its geometrical shape has no influence upon the transformations that
occur within the wave.
Owing to its nature, the aforementioned analysis is necessary incomplete, due
to the fact that the possible influence of the intermediate states is ignored. Therefore,
it is not to be expected that all the types of combustion waves compatible with the said
principles of conservation will actually occur. On the contrary, when analyzing the
internal mechanism of the propagation of the process, the existence of new limitations
is to be expected. It should also be expected that such limitations will enable us to
eliminate the indeterminacy, mentioned at the end of the preceding chapter, and to
select from all the waves compatible with the laws of conservation the one which will
actually occur in each case.
To make this point clear, it is necessary to take into consideration the internal
structure of the wave. This is done in the present chapter, following a similar procedure
to the one used in Gas Dynamics [1] when studying the internal structure of
shock waves.
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