Combustion wave thermodynamic characteristics

The combustion wave of a premixed gas propagates with a certain velocity into the unburned region (with flow speed = 0). The velocity is sustained by virtue of thermodynamic and thermochemical characteristics of the premixed gas. Figure 3.1 illustrates a combustion wave that propagates into the unburned gas at velocity Mj, one-dimensionally under steady-state conditions. If one assumes that the observer of the combustion wave is moving at the same speed, Wj, then the combustion wave appears to be stationary and the unburned gas flows into the combustion wave at the velocity -Wj. The burned gas is expelled downstream at a velocity of-M2 with respect to the combustion wave. The thermodynamic characteristics of the combustion wave are described by the velocity (u), pressure (p), density (p), and temperature (T) of the unburned gas (denoted by the subscript 1) and of the burned gas (denoted by the subscript 2), as illustrated in Fig. 3.1. 

Premixed flames are waves of combustion (for example, see [PRU 13]), whose reference velocity (that of the adiabatic planar flame) can quite easily be calculated on the basis of the thermodynamic characteristics of the constituent parts, as long as we are deahng with flames with high activation energy. Here, we shall limit ourselves to the study of the effects of gravity and of a centrifugal acceleration field on such flames, and primarily on their res dting frequency of oscillation. 

---