Of premixed laminar flames

Marra, F.S. and Continillo, G., Numerical study of premixed laminar flame propagation in a closed tube with a full Navier-Stokes approach, Twenty-Sixth Symposium (International) on Combustion, The Combustion Institute, Pittsburgh, pp. 907-913,1996. 

Valorani, M., Creta, F., Goussis, D., Lee, J., Najm, H. An automatic procedure for the simplification of chemical kinetic mechanisms based on CSP. Combust. Flame 146, 29-51 (2006) Van Oijen, J.A., de Goey, L.P.H. Modelling of premixed laminar flames using Flamelet Generated Manifolds. Combust. Sci. Technol. 161, 113-137 (2000)... 

The relevance of premixed edge flames to turbulent premixed flames can also be understood in parallel to the nonpremixed cases. In the laminar flamelet regime, turbulent premixed flames can be viewed as an ensemble of premixed flamelets, in which the premixed edge flames can have quenching holes by local high strain-rate or preferential diffusion, corresponding to the broken sheet regime [58]. 

Darabiha, N., Candel, S., and Marble, R, The effect of strain rate on a premixed laminar flame. Combust. Flame, 64, 203, 1986. 

Giovangigli, V. and Smooke, M., Extinction of strained premixed laminar flames with complex chemistry. Combust. Sci. Technol., 53,23, 1987. 

The modeling of steady-state problems in combustion and heat and mass transfer can often be reduced to the solution of a system of ordinary or partial differential equations. In many of these systems the governing equations are highly nonlinear and one must employ numerical methods to obtain approximate solutions. The solutions of these problems can also depend upon one or more physical/chemical parameters. For example, the parameters may include the strain rate or the equivalence ratio in a counterflow premixed laminar flame (1-2). In some cases the combustion scientist is interested in knowing how the system mil behave if one or more of these parameters is varied. This information can be obtained by applying a first-order sensitivity analysis to the physical system (3). In other cases, the researcher may want to know how the system actually behaves as the parameters are adjusted. As an example, in the counterflow premixed laminar flame problem, a solution could be obtained for a specified value of the strain... 

Procedures enabling the calculation of bifurcation and limit points for systems of nonlinear equations have been discussed, for example, by Keller (13) Heinemann et al. (14-15) and Chan (16). In particular, in the work of Heineman et al., a version of Keller s pseudo-arclength continuation method was used to calculate the multiple steady-states of a model one-step, nonadiabatic, premixed laminar flame (Heinemann et al., (14)) a premixed, nonadiabatic, hydrogen-air system (Heinemann et al., (15)). 

A number of theoretical (5), (19-23). experimental (24-28) and computational (2), (23), (29-32). studies of premixed flames in a stagnation point flow have appeared recently in the literature. In many of these papers it was found that the Lewis number of the deficient reactant played an important role in the behavior of the flames near extinction. In particular, in the absence of downstream heat loss, it was shown that extinction of strained premixed laminar flames can be accomplished via one of the following two mechanisms. If the Lewis number (the ratio of the thermal diffusivity to the mass diffusivity) of the deficient reactant is greater than a critical value, Lee > 1 then extinction can be achieved by flame stretch alone. In such flames (e.g., rich methane-air and lean propane-air flames) extinction occurs at a finite distance from the plane of symmetry. However, if the Lewis number of the deficient reactant is less than this value (e.g., lean hydrogen-air and lean methane-air flames), then extinction occurs from a combination of flame stretch and incomplete chemical reaction. Based upon these results we anticipate that the Lewis number of hydrogen will play an important role in the extinction process. 

Arc-length continuation, steady states of a model premixed laminar flame, 410 Architecture, between parallel machines, 348 Arithmetic control processor, ST-100, 125 Arithmetic floating point operations,... 

Results of the model for two parameters, i.e., the spatial temperature profile and the mass flux into the reaction zone as a function of gas mass flux are presented in Fig. 8.7. The temperature profile of the solid fuel flame (Fig. 8.7, left) is similar to that of a premixed laminar flame it consists of a preheat zone and a reaction zone. (The spatial profile of the reaction source term, which is not depicted here, further supports this conclusion.) The temperature in the burnt region (i.e., for large x) increases with the gas mass flux. The solid mass flux (Fig. 8.7, right) initially increases with an increase of the air flow, until a maximum is reached. For higher air flows, it decreases again until the flame is extinguished. 

Van Oijen, J. Flamelet-generated manifolds development and application to premixed laminar flames, PhD thesis, Eindhoven University of Technology, Eindhoven, The Netherlands, (2002). 

Heimerl, J. M., and T. P. Coffee. 1980. The detailed modeling of premixed, laminar steady-state flames. 1. Ozone. Combustion Flame 39 301-15. 

The Premixed, Laminar Flame Perhaps the most common laboratory device for studying combustion chemistry is the laminar, one-dimensional, premixed flame [275]. Such flames are normally stabilized on top of a porous metal cylinder through which the reactants are fed. The flame is usually operated at low pressure, normally between 10 and 100 Torr, to spread out the reaction zone so that spatial distributions of temperature and... 

V. Giovangigli and M.D. Smooke. Calculation of Extinction Limits for Premixed Laminar Flames in a Stagnation Point Flow. J. Comp. Phys., 68 327-345,1987. 

Laser Probes of Premixed Laminar Methane-Air Flames and Comparsion with Theory... 

The measurements of temperature and species concentrations profiles in premixed, laminar flames play a key role in the development of detailed models of hydrocarbon combustion. Systematic comparisons are given here between a recent laminar methane-air flame model and laser measurements of temperature and species concentrations. These results are obtained by both laser Raman spectroscopy and laser fluorescence. These laser probes provide nonintrusive measurements of combustion species for combustion processes that require high spatial resolution. The measurements reported here demonstrate that the comparison between a model and the measured concentrations of CH, O2,... 

Figure 3. Schematic of turbulent combustor geometry and optical data acquisition system for vibrational Raman-scattering temperature measurements using SAS intensity ratios. Also shown are sketches of the expected Raman contours viewed by each of the photomultiplier detectors, the temperature calibration curve, and several expected pdf s of temperature at different flame radial positions. The actual SAS temperature calibration curve was calculated theoretically to within a constant factor. This constant, which accounted for the optical and electronic system sensitivities, was determined experimentally by means of SAS measurements made on a premixed laminar flame of known temperature. Measurements of Ne concentration were made also with this apparatus, based on the integrated Stokes vibrational Q-branch intensities. These signals were related to gas densities by calibration against ambient air signals.

R = K exp (Q/T), where the constant K incorporates spectroscopic and optical system constants. The value of K was experimentally determined by calibration against a premixed laminar flame with a known temperature produced on a porous plug burner. The characteristic vibrational temperature Q = hcco/k = 3374°K for nitrogen. Here, h is Planck s constant, c is the speed of light, 0) is the vibrational constant, k is Boltzmann s constant, and T is the temperature in Kelvin. 

The basic limitations to the overall accuracy of the data presented here lie in the Raman measurement process - inherently weak, but possessing sufficient intensity as utilized here to produce, for example, only 5-7% standard deviations for instantaneous temperature determinations in a "calibrated" premixed laminar flame (9). Further development of this light scatter-... 

---