Laminar premixed

At first glance, the science of vapor cloud explosions as reported in the literature seems rather confusing. In the past, ostensibly similar incidents produced extremely different blast effects. The reasons for these disparities were not understood at the time. Consequently, experimental research on vapor cloud explosions was directed toward learning the conditions and mechanisms by which slow, laminar, premixed combustion develops into a fast, explosive, and blast-generating process. Treating experimental research chronologically is, therefore, a far from systematic approach and would tend to confuse rather than clarify. 

Hansen, N. et al.. Initial steps of aromatic ring formation in a laminar premixed fuel-rich cyclopentene flame, /. Phys. Chem. A, 111, 4081,2007. 

Wang, H. and Frenklach, M., A detailed kinetic modeling study of aromatics formation in laminar premixed acetylene and ethylene flames. Combust. Flame, 110,173, 1997. 

Dixon-Lewis G., Aspects of laminar premixed flame extinction limits, Proc. Combust. Inst., 25 1325-1332, 1994. 

Egolfopoulos, F.N., Zhang, H., and Zhang, Z., Wall effects on the propagation and extinction of steady, strained, laminar premixed flames. Combust. Flame, 109,237,1997. 

S. Ducruix, D. Durox, and S. Candel. Theoretical and experimental determination of the transfer function of a laminar premixed flame. Proceedings of the Combustion Institute, 28 765-773, 2000. 

R. Relce and R. Glavin. Influence of hydrodynamics and diffusion upon the stability limits of laminar premixed flames. /. Fluid Mech., 124 219-237, 1982. 

J.H. Cho and T. Lieuwen. Laminar premixed flame response to equivalence ratio oscillations. Combust. Flame, 140 116-129, 2005. 

Darrieus and Landau established that a planar laminar premixed flame is intrinsically unstable, and many studies have been devoted to this phenomenon, theoretically, numerically, and experimentally. The question is then whether a turbulent flame is the final state, saturated but continuously fluctuating, of an unstable laminar flame, similar to a turbulent inert flow, which is the product of loss of stability of a laminar flow. Indeed, should it exist, this kind of flame does constitute a clearly and simply well-posed problem, eventually free from any boundary conditions when the flame has been initiated in one point far from the walls. 

Laminar premixed flames, 7 443 445 Laminar regime, viscous liquid blending in, 16 690-691... 

The results presented above clearly demonstrate the merits of the counter-current shear layer control as a flame stabilization technique. With the use of the high-resolution PIV, the near flame structure is measured with sufficient detail to obtain the velocity gradients with accuracy. Prom these measurements, it is observed that the transverse velocity gradient dU /dr assumes large values at the nozzle exit as compared to that of laminar premixed Bunsen burner flames. 

As mentioned in the previous section, laminar, premixed, flat flames are used widely in the study of combustion chemistry. The left-hand panel of Fig. 1.1 shows a typical burner setup. The flames themselves are accessible to an array of physical and optical diagnostics, and the computational models can incorporate the details of elementary chemical reactions. 

The objective of this problem is to explore the multicomponent diffusive species transport in a chemically reacting flow. Figure 3.18 illustrates the temperature, velocity, and mole-fraction profiles within a laminar, premixed flat flame. These profiles are also represented in an accompanying spreadsheet (premixed h2. air-flame. xls). 

This section concentrates on laminar premixed flames, which serve to illustrate many attributes of steady-state one-dimensional reacting systems. The governing equations themselves can be written directly from the more general systems derived in Chapter 3. Referring to the cylindrical-coordinate summary in Section 3.12.2, and retaining only the axial components, the one-dimensional flame equations reduce immediately to... 

Use laminar premixed free-flame calculations with a detailed reaction mechanism for hydrocarbon oxidation (e.g., GRI-Mech (GRIM30. mec)) to estimate the lean flammability limit for this gas composition in air, assuming that the mixture is flammable if the predicted flame speed is equal to or above 5 cm/s. For comparison, the lean flammability limits for methane and ethane are fuel-air equivalence ratios of 0.46 and 0.50, respectively. 

The laminar premixed flame speed Si of a fuel is a function of the molecular and thermal diffusivity of the reactants and of the chemical reaction rate. 

Use GRI-Mech (GRIM30. mec) and a laminar premixed flame code to calculate the flame speed of a methane-air mixture at selected pressures between 0.1 and 10 atm. Evaluate whether the empirical correlation [412] for methane-air flames,... 

In the development of effective control methods for NO, it is important to establish the controlling mechanism of nitric-oxide formation in laminar premixed flames... 

The purpose of this exercise is to investigate the effect of an inert (CO2) and a chemically active agent (iron pentacarbonyl, Fe(CO)s) on the flame speed of an atmospheric, stoichiometric methane-air flame. Employ a laminar premixed flame code to determine the flame speed, using GRI-Mech extended with a subset for iron pentacarbonyl chemistry [344] (GRIMFe.mec). 

H. Wang and M. Frenklach. A Detailed Kinetic Modeling Study of Aromatics Formation in Laminar Premixed Acetylene and Ethylene Flames. Combust. Flame, 110 173-221,1997. 

The accuracy of the temperature pdf data obtained with the Raman Stokes/anti-Stokes technique has been assessed by tests made on a known and well-calibrated laminar premixed flame source, viz., a porous plug burner (20). These data, which were checked by analytical calculations based upon the optical and electronic properties of our detection system, showed a roughly 5-7% standard deviation, which has been considered acceptable for present measurement purposes (2 7). However, additional problem not considered in this type of test, can exist. For example ... 

Two flat flame burners have been employed, a 4 cm 10 cm burner with a ceramic-lined chimney for NO measurements (4) and a 2.6 cm x 8.6 cm open-faced burner with a nitrogen shroud flow for CO measurements. Both burners operate at atmospheric pressure with laminar, premixed methane-air mixtures. These burners work satisfactorily over a broad range of fuel-air equivalence ratios, but both have cold boundary regions which cause non-uniform conditions along the optical axis that can be important in the data analysis (4). 

The flame structure is modeled by solving the conservation equations for a laminar premixed burner-stabilized flame with the experimental temperature profile determined in previous work using OH-LIF. Three different detailed chemical kinetic reaction mechanisms are compared in the present work. The first one, denoted in the following as Lindstedt mechanism, is identical to the one reported in Ref. 67 where it was applied to model NO formation and destruction in counterffow diffusion flames. This mechanism is based on earlier work of Lindstedt and coworkers and it has subsequently been updated to include more recent kinetic data. In addition, the GRI-Mech. 2.11 (Ref. 59) and the reaction mechanism of Warnatz are applied to model the present flame. 

Fig. 8 Laminar premixed flames of methane. (A) Slightly fuel rich (B) fuel-rich and sooting and (C) diffusion flame. Note increased luminosity with increasing equivalence ratio.

Marinov, N.M. Pitz, W.J. Westbrook, C.K. et al. Aromatic and polycyclic aromatic hydrocarbon formation in a laminar premixed n-butane flame. Combust. Flame 1998, 114, 192-213. 

Balthasar, M. Kraft, M. 2003 A stochastic approach to calculate the particle size distribution function of soot particles in laminar premixed flames. Combustion and Flame 133, 289-298. 

Kazakov, A. Frenklach, M. 1998 Dynamic modelling of soot particle coagulation and aggregation implementation with the method of moments and application to high-pressure laminar premixed flames. Combustion and Elame 114, 484-501. 

Searby and Rochwerger [9] developed a model describing the effect of an acoustic field on the stability of a laminar, premixed flame, treated as a thin interface between two fluids of different densities and under the influence of a periodic gravitational field. Their model is an extension of the work by Markstein [8] and is consistent with the more recent flame theory of Clavin and Garcia-Ybarra [16]. Bychkov [17] later solved the problem analytically, presenting the following linear equation for the perturbation amplitude, /, of a flame under the influence of an acoustic field [17] ... 

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