Flame plane

The xylene isomers are flammable Hquids and should be stored in approved closed containers with appropriate labels and away from heat and open flames. Limits for transportation by air are 5 L on passenger planes and 60 L on cargo planes. 

The pressure developed by decomposition of acetylene in a closed container depends not only on the initial pressure (or more precisely, density), but also on whether the flame propagates as a deflagration or a detonation, and on the length of the container. For acetylene at room temperature and pressure, the calculated explosion pressure ratio, / initial > deflagration and ca 20 for detonation (at the Chapman-Jouguet plane). At 800 kPa (7.93... 

Step 3 Calculate the distance from the center of the flame to a position with coordinates x and z, representing personnel or equipment exposed to radiation from the flame. (Since the limiting case is the one in which the flame is blown over in the direction of the exposed personnel or equipment, they are in the same plane and a two-coordinate system is adequate for describing their relative locations). Note also that all wind directions must be considered, even in locations which have a prevailing wind direction. 

The view factor depends on the shape of the emitting surface (plane, cylindrical, spherical, or hemispherical), the distance between emitting and receiving surfaces, and the orientation of these surfaces with respect to each other. In general, the view factor from a differential plane dAj) to a flame front (area A,) on a distance L is determined (Figure 3.10) by ... 

For a flash fire, the flame can be represented as a plane surface. Appendix A contains equations and tables of view factors for a variety of configurations, including spherical, cylindrical, and planar geometries. 

The flame-surface area dependent on time is approximated by a plane cross-section moving at burning speed through the stationary cloud. 

Section 3.5 mentions two approaches, the point-source model and the solid-flame model. In the point-source model, it is assumed that a certain fraction of the heat of combustion is radiated in all directions. This fraction is the unknown parameter of the model. Values for fireballs are presented in Section 3.5.1. The point-source model should not be used for calculating radiation on receptors whose plane intercepts the fireball (see Figure 6.9B). 

The thermal radiation received by an object in the environment may now be computed if it is assumed that the flame appears as a flat plane, 33 m high, which propagates at a constant speed of 4.6 m/s during the full period of flame propagation (100/4.6 = 21.7 s). During this period, flame width varies from 0 to 100 m and back, according to Figure 8.1b ... 

Calculate the view factor using the equation given in Appendix A for a vertical plane surface emitter, or else read the view factor from Table A-2 of Appendix A for the appropriate X and fi. This results in F = 0.062 for each portion of the flame surface, and implies a total view factor of... 

Radiation heat flux is graphically represented as a function of time in Figure 8.3. The total amount of radiation heat from a surface can be found by integration of the radiation heat flux over the time of flame propagation, that is, the area under the curve. This result is probably an overstatement of realistic values, because the flame will probably not bum as a closed front. Instead, it will consist of several plumes which might reach heights in excess of those assumed in the model but will nevertheless probably produce less flame radiation. Moreover, the flame will not bum as a plane surface but more in the shape of a horseshoe. Finally, wind will have a considerable influence on flame shape and cloud position. None of these eflects has been taken into account. 

Further measurements on the flame speed have been obtained with the use of a rotating tube [11] and vortex ring combustion [12]. Figure 4.2.4 shows the flame speed in vortex rings [12]. The values of slope in the V( -plane is nearly equal to unity for the near stoichiometric methane/air mixtures. Thus, this value is much lower than the predictions of JPi/P, and flPn/P >. 

In all the mixtures, the flame speed increased almost linearly with an increase in the maximum tangential velocity. The value of the slope in the Vf-y(,max plane was almost unity for the stoichiometric mixtures, however, the slope became smaller for the lean and rich mixtures. The flame to the core diameter ratio decreased with the increasing Vg The ratio was around unity in the stoichiometric mixtures, while it was smaller than unity in the lean and rich mixtures. 

This chapter considers the first group of instabilities and introduces the analysis of processes implying an interaction with external flow-field perturbahons. This is exemplified by investigations of coupling between pressure waves and plane flames and also between an external acceleration field and flame fronts. The coupling between flow perturbations and flames giving rise to heat release unsteadiness and coupling with acoushc modes is considered in Chapter 5.2, which deals with the relationship between perturbed flame dynamics and radiated acoustic field, a fundamental process of thermo-acoustic instabilities. 

An individual isothermal surface can be traced with the help of laser tomography, also known as laser sheet imaging, where a laser sheet and oil droplets are combined to visualize the instantaneous flame surface in a plane. This technique is ideal when wrinkling of an isoline is of interest besides, typically it shows the area occupied by the combustion products if the instantaneous flame thickness is small, such as a black area in... 

Hawkes, E.R., S. Sankaran, J.C. Sutherland, and J.H. Chen, Scalar mixing in direct numerical simulations of temporally-evolving plane jet flames with detailed CO/Hj kinetics. Proc. Combust. Inst., 2007. 31 1633-1640. 

This equation has been derived as a model amplitude equation in several contexts, from the flow of thin fluid films down an inclined plane to the development of instabilities on flame fronts and pattern formation in reaction-diffusion systems we will not discuss here the validity of the K-S as a model of the above physicochemical processes (see (5) and references therein). Extensive theoretical and numerical work on several versions of the K-S has been performed by many researchers (2). One of the main reasons is the rich patterns of dynamic behavior and transitions that this model exhibits even in one spatial dimension. This makes it a testing ground for methods and algorithms for the study and analysis of complex dynamics. Another reason is the recent theory of Inertial Manifolds, through which it can be shown that the K-S is strictly equivalent to a low dimensional dynamical system (a set of Ordinary Differentia Equations) (6). The dimension of this set of course varies as the parameter a varies. This implies that the various bifurcations of the solutions of the K-S as well as the chaotic dynamics associated with them can be predicted by low-dimensional sets of ODEs. It is interesting that the Inertial Manifold Theory provides an algorithmic approach for the construction of this set of ODEs. 

In flame extinction studies the maximum temperature is used often as the ordinate in bifurcation curves. In the counterflowing premixed flames we consider here, the maximum temperature is attained at the symmetry plane y = 0. Hence, it is natural to introduce the temperature at the first grid point along with the reciprocal of the strain rate or the equivalence ratio as the dependent variables in the normalization condition. In this way the block tridiagonal structure of the Jacobian can be maintained. The flnal form of the governing equations we solve is given by (2.8)-(2.18), (4.6) and the normalization condition... 

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. 

Figure 8. Distance of the flame from the symmetry plane versus the equivalence ratio for hydrogen-air flames with a strain rate of a = 1000 sec . ...

The technology for making single crystal ball electrodes is inexpensive and well developed [223, 224], Wire of the noble metals Au and Pt can be melted in a hydrogen oxygen flame. By careful manipulation of the flame on the ball, it can be recrystallized repeatedly to form a perfect single crystal. The crystals have a set of flat spots, [111] planes, which develop on the surface. These facets feature some of the... 

In the Spalding burner, a flat plane flame stands off the surface of a cooled porous matrix. Data are compiled to give Su as measured by the speed in the burner supply, to maintain a stable flame, for a given measured cooling rate. By plotting these data so as to extrapolate to a zero cooling condition yields, S U under nearly adiabatic conditions. 

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