Turbulent burning rates

It is worth noticing that the "turbulent burning rates" reported in Figure 7.1.2 have been defined similarly but not exactly as the "turbulent flame speed" mentioned in Section 7.1.2. The mixture has been ignited at the center of the bomb and the dependence of the pressure on time has been recorded. This has enabled to determine the derivative of the burned mixture volume. This derivative is ascribed to a spherical surface whose volume is simply equal to the volume of fully burned products, thus leading to an estimate of the turbulent combustion rate. 

Ya.B. ZeFdovich, FizGoreniyaVzryva 7 (4), 463-76 (1971) CA 77, 64194 (1972) The influence of turbulence and nonturbulence is examined relative to a proplnt burning in a gas flow. Equations indicate exptl methods for determining the magnitudes of the thermal conductivity and viscosity under turbulent flow, and permit a study of thermal flow distribution and temps in a gas wherein an exothermic chem reaction occurs. Equations for non turbulent conditions can be used to calculate the distance from the surface of the proplnt to the zone of intense chem reaction and establish the relation of bulk burning rate to the vol reaction rate. 

Abdel-Gayed,R.G., Bradley, D.,andLawes, M., Turbulent burning velocities A general correlation in terms of straining rates, Proc. R. Soc. Lond. A, 414, 389,1987. 

Turbulent mass burning rate versus the turbulent root-mean-square velocity by Karpov and Severin [18]. Here, nis the air excess coefficient that is the inverse of the equivalence ratio. (Reprinted from Abdel-Gayed, R., Bradley, D., and Lung, F.K.-K., Combustion regimes and the straining of turbulent premixed flames. Combust. Flame, 76, 213, 1989. With permission. Figure 2, p. 215, copyright Elsevier editions.)... 

The fact that the fuel/air ratio is spatially constant in HCSI engines, at least within a reasonably close approximation, allows substantial simplifications in combustion models. The burn rate or fuel consumption rate dm /dt is expressed as a function of flame surface area the density of the unburnt fuel/air mixture Pu, the laminar burning velocity Sl, and the fluctuations of velocities, i.e., E as a measure of turbulence, u. ... 

Turbulent convective burning of vertical plate. An approximate solution matched to data was given by Ahmad and Faeth [11]. The average burning rate mp for a distance x measured from the start of the plate is given by the formula below ... 

In Figure 9.14 we see a more classical demonstration of the range of burning rate behavior of a pool fire. Below a diameter of 25 cm the burning rate is laminar with hc cx D 1 4 afterwards it is turbulent as hc oc D° or D1 5 at most. However, with... 

Figure 9.15 Regimes of the steady burning rate for methanol D < 25 cm laminar, D > 25 cm turbulent, D > 100 cm radiation saturated [16, 17]...

If, indeed, Eqs. (6.171) and (6.172) adequately predict the burning rate of a droplet in laminar convective flow, the droplet will follow a d3/2 burning rate law for a given relative velocity between the gas and the droplet. In this case (3 will be a function of the relative velocity as well as B and other physical parameters of the system. This result should be compared to the d2 law [Eq. (6.172)] for droplet burning in quiescent atmospheres. In turbulent flow, droplets will appear to follow a burning rate law in which the power of the diameter is close to 1. 

Although a nearly planar premixed turbulent flame is maintained in the stagnation-flow burning configuration (3), the divergence of flow-field streamlines results in mean strain rates which also modify the turbulent flame structure and burning rates. 

Combustion. 1) V.E. Annikov et al, Effect of Water, Ammonium Carbonate and other Additives on Combustion of Explosives , FizGoreniya-Vzryva 5 (1), 60-67 (1969) CA 71, 40905 (1969) [The authors state that the effects of w on the burning rate of Tetryl and RDX in a constant pressure bomb can be explained by the Zel dovich (1942) theory. They report that the burning rate of RDX with iO to 20% w added is higher because of strong turbulence] 2) M A. 

Structure of Turbulent Flames. The great technical importance of turbulent burning lies in the fact that the turbulent flame can consume fuel-air mixture at a faster rate than the laminar flame. 

The point is that no unambiguous turbulent burning velocity can be measured at present. However, it is perfectly possible to determine burning rates with reference to arbitrarily chosen surfaces in time-exposed photographs these rates must serve at present to characterize turbulent flames. 

Edelman, R. B. Fortune, 0. F. "A Quasi-Global Chemical Kinetic Model for the Finite-Rate Combustion of Hydrocarbon Fuels With Application to Turbulent Burning and Mixing in Hypersonic Engines and Nozzles" AIAA Paper 69-86, AIAA,... 

Equations (45) and (46) are only two of many formulas that have been used to describe erosive burning [8]. Most of the formulas that have been suggested are based on physical concepts of influences of crossflow on propellant burning. Among these concepts is the idea that high external velocities produce a turbulent boundary layer (see Chapter 12) on the propellant surface and thereby effectively increase the thermal diffusivity of the gas, which in turn increases the rate of heat transfer to the propellant and hence the burning rate [99]. The idea that turbulent convective heat transfer from the hot combustion products outside the boundary layer provides an additive contribution to the heat flux reaching the propellant surface and,... 

R. G. Abdel-Gayed and D. Bradley, The Influence of Turbulence Upon the Rate of Turbulent Burning, in Fuel-Air Explosions, J. H. S. Lee and C. M. Guirao, eds., Waterloo, Canada University of Waterloo Press, 1982, 51-68. 

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