Velocity, subsonic

Deflagration. In a deflagration, the flame front travels through the flammable mixture relatively slowly, i.e., at subsonic velocity. 

Deflagration Chemical reaction in which the output of heat is sufficient to enable the reaction to proceed and be accelerated without heat from another source a surface phenomenon in which reaction products flow away from the unreacted material along the surface at subsonic velocity. The result of a true deflagration under confinement is an explosion. 

An explosion can be defined as a fast, transient, exothermic reaction. It needs exothermicity to generate energy and must be fast to generate this energy very quickly in a transient pulse. We can also distinguish between events in which the reaction propagates at subsonic velocity as an explosion and one in which the reaction propagates with sonic or supersonic velocity as a detonation. 

The velocity of advance of the front is super sonic in a detonation and subsonic in a deflagration. In view of the importance of a shock process in initiating detonation, it has seemed difficult to explain how the transition to it could occur from the smooth combustion wave in laminar burning. Actually the one-dimensional steady-state combustion or deflagration wave, while convenient for discussion, is not easily achieved in practice. The familiar model in which the flame-front advances at uniform subsonic velocity (v) into the unburnt mixture, has Po> Po> an[Pg.249]

Since detonations propagate at supersonic velocities, while deflagrations propagate at low subsonic velocities, the mass flow rate m is much larger for detonations than for deflagrations. Consequently, the dimensionless reaction-rate function F,(z, [Pg.191]

Fig. 29. The hyperradius p of a cluster of 125 Ar atoms imi> u ting a surface at a subsonic velocity of 100 ms. Results are shown over a long time scale beginning before the impact (at t = 0) and for a long time thereafter. It is evident that the slight increase in p is due to an evaporation of one Ar atom, see inserts.

Kraft, H. (1949). Reaction tests of turbine nozzles for subsonic velocities. Transactions of the American Society of Mechanical Engineers, 71, 781-787. 

Many applications of Eq. 7,16 involve jets. A jet is a stream of fluid which is not confined within a pipe, duct, or channel examples are the stream of water issuing from a garden hose and the exhaust gas stream from a jet engine. If a jet is flowing at a subsonic velocity, its pressure will be the same as the pressure of the surrounding fluid. If a jet enters or leaves a system or device at subsonic speed, it will enter and leave at the pressure of the surrounding fluid, although its pressure may be different inside the device. 

For P2 > Pa the combustion fi ont moves with supersonic velocity and for p2 < Pb with subsonic velocity. The differentiation has to be based on the velocity... 

Figures 10 and 11 show the decay of overpressure with distance outside the ignited vapor cloud for natural gas and hydrogen jets dependent on subsonic velocity Uo and nozzle diameter do/ as measured in the BASF experiments.

Deflagration - a combustion wave propagating from an explosion at subsonic velocity relative to the unburnt gas immediately ahead of the flame (flame front). 

Sect. 1.10 if we restrict the discussion to the subsonic case. For subsonic velocities, /(co) can be expanded as a Taylor expansion in the velocity, where each term is a rational function of the moduli, as required by the argument in Sect. 1.10. We will see in the next section that the situation becomes more complex above the subsonic region. Taking the inverse Fourier transform of (7.2.3 a) gives... 

A detonation is a wave in which an exothermal chemical reaction takes place and which moves with supersonic velocity with respect to the undetonated gas. This is in contrast to a flame, which moves with subsonic velocity. Flames and detonations are associated with qualitatively distinct types of solutions of the same set of hydrodynamic equations and boundary conditions. 

Deflagration Flame front propagation at relatively lower subsonic velocity than the sound speed in the reactants ahead of it (but not necessarily). 

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