Combustion wave propagation

Piane Combustion Wave. See Combustion Wave Propagation in Vol 3, C433-R Ref J.H. Burgoyne F. Weinberg, A Method of Analysis of a plane Combustion Wave , 4th SyropGombstn, Williams Wilkins, Baltimore (1953), 294-302. ... 

HMX and RDX are heated, deflagration combustion occurs with a burning rate of about 1 mm s" at 1 MPa. However, when these nitramines are ignited by primers giving rise to shock waves, detonation combustion occurs with a burning rate of more than 7000 m s . The characteristics of combustion wave propagation are determined by the Chapman-Jouguet relationship described in Refs. [1-5]. 

No theoretical criterion for flammability limits is obtained from the steady-state equation of the combustion wave. On the basis of a model of the thermally propagating combustion wave it is shown that the limit is due to instability of the wave toward perturbation of the temperature profile. Such perturbation causes a transient increase of the volume of the medium reacting per unit wave area and decrease of the temperature levels throughout the wave. If the gain in over-all reaction rate due to this increase in volume exceeds the decrease in over-all reaction rate due to temperature decrease, the wave is stable otherwise, it degenerates to a temperature wave. Above some critical dilution of the mixture, the latter condition is always fulfilled. It is concluded that the existence of excess enthalpy in the wave is a prerequisite of all aspects of combustion wave propagation. 

Combustion Wave Propagation. This subject has been discussed in the following refs. 

Rybanin, S. S., Sobolev, S. L. Combustion Wave Propagation in Heterogeneous Reaction, a preprint, Chernogolovka, Branch of the Institute of Chemical Physics Academy of Sciences of the USSR 1981 (in Russian)... 

In a stationary detonation wave, the shock front is followed by a zone of chemical reaction which can be considered as an ordinary stationary-state combustion wave propagating through the denser and hotter gases behind the shock front (Fig. XIV.7). Such a combustion wave is characterized by a pressure decrease and a temperature increase across the flame front. Because of this and because, in the stationary state, the flame front must follow the shock front at a fixed distance, the model of the moving surface is not quite adequate to describe a stationary detonation/ A further difference between the two is that, whereas in the mechanical shock the surface velocity Vb was an independent parameter at the disposal of the experimenter, in the detonation the chemical composition of the reacting gases is the collective parameter which replaces vt and is the means by which the experimenter can control the detonation velocity. 

In all these laminar-flame experiments, the combustion wave propagates at a definite velocity that empirically depends on the pressure, temperature, and composition of the initial combustible mixture. Our primary objective in this chapter is to predict this burning velocity. In Section 5.1.2 a simple physical picture of the deflagration wave is presented, leading to a crude estimate of the burning velocity. The discussion, which is similar to that of Landau and Lifshitz [3], illustrates the essential mechanism involved. 

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