Flame profile

The raw data of the thermocouples consist of the temperature as a function of time (Fig. 8.9, left). In the raw data, the passing of the conversion front can be observed by a rapid increase in temperature. Because the distance between the thermocouples is known, the velocity of the conversion front can be determined. The front velocity can be used to transform the time domain in Fig. 8.9 (left) to the spatial domain. The resulting spatial flame profiles can be compared with the spatial profiles resulting from the model. The solid mass flux can also be plotted as a function of gas mass flow rate. The trend of this curve is similar to the model results (Fig. 8.9, right). 

Chemical reaction or reaction product, partly or entirely gaseous, that yields heat and light. State of blazing combustion. Flame profile is temperature profile of any particular flame. Flame temperature is the calculated or determined temperature of the flame. 

This equation expresses the stationary condition that the two fluxes of enthalpy and heat must be in balance at every point in the flame profile. The summation on the left can be looked upon as a current of excess enthalpy moving toward the flame front with the flame speed m and compensated by a heat flux K(dT/dx) moving in the opposite direction from the hotter to the colder gases. This excess enthalpy comes from the conduction, convection, and diffusion losses of the volume elements in and near the flame zone. ... 

The interpretation of measured flame profiles by means of the continuity equations may be approached in one of two ways. The direct experimental approach involves the use of the measured profiles to calculate overall fluxes, reaction rates, and hence rate coefficients. Its successful application depends on the ability to measure the relevant profiles, including concentrations of intermediate products. This is not always possible. In addition, the overall fluxes in the early part of the reaction zone may involve large diffusion contributions, and these depend in turn on the slopes of the measured profiles. Thus accuracy may suffer. The lining up on the distance axis of profiles measured by different methods is also a problem, and, in quantitative terms, factor-of-two accuracy is probably about the best that may normally be expected from this approach at the position of maximum rate. Nevertheless, examination of the concentration dependence of reaction rates in flames may still provide useful preliminary information about the nature of the controlling elementary processes [119—121]. Some problems associated with flame profile measurements and their interpretation have been discussed by Dixon-Lewis and Isles [124]. Radical recombination rates in the immediate post-combustion zones of flames are capable of measurement with somewhat h her precision than above. 

The second approach to the interpretation of flame profiles is to assume a reaction mechanism and data, solve the conservation equations to obtain the flame properties, and then compare these with experiment. 

A flame profile provides useful informalir>n ahoiil the processes lhai go on in different parts of a flame it is a contour plol lhal reveals regions of the flame lhal have similar values for a variable of interest. Some t>f these variables include icinperaiurc. chemical composition, absorbance, and radiant or fluorescence iniensiiv. 

Figure 6.17 (a) Flame profiles for Cr, Mg, and Ag demonstrating differences in free atom formation... 

How does the rapid formation of a stable oxide of the analyte affect its flame profile ... 

Fig. 6.3. Flame profile of a conventional type A flame (fig. 6.2) on a steel reheat furnace. The vertical (temperature) scale reflects the heat flux profile. ATP burners can operate at a constant high input while switching temperature profiles, for example, from 30% to 100%.

ATP burners can control their thermal profile by by varying their spin to change the directions and lengths (reach) of their jets while maintaining near-stoichiometric air/fuel ratio. They are the best method currently available with large burners for obtaining both low fuel cost and excellent temperature uniformity because two T-sensor locations can be controlled by one burner (discussed in several places within this book). Regenerative burners with flame profile control will be the answer for excellent uniformity and fuel economy. 

Other recommended equipment changes related to the improvement of clinker quality can be found in papers by Hansen (1983) and Miller (1978). Jany and Love (1993) presented microscopical data corresponding to specific changes in flame profile, initial cooling, cooler bed depth, and I.D. fan, in a 158.6-mefer, dry-process kiln. 

FIGURE 9-3. Flame profile showing areas of maximum emission intensities of various elements. [From B. E. Buell, Use of Organic Solvents in Limited Area Flame Spectrometry, Anal. Chem., 34, 636 (1962). Used by permission of the American Chemical Society.]... 

FIGURE 10-18. Atomic absorption flame profiles for rhenium and zinc. [From W. G. Schrenk, D. A. Lehman, and L. Neufield, Atomic Absorption Characteristics of Rhenium, AppL Spectrosc., 20, 389 (1966). Used by permission of Applied Spectroscopy.]... 

Fig. 3. Typical flame profiles. Stoichiometric ethylene/oxy-gen pressure, 4 Torr adiabatic flame temperature, 2500°K total flow, 100 ml sec (STP) burner diameter, 15 cm.

In Fig. 10 an experimental rotation-vibrational CARS-spectrum (Q-branch of N2) from the burner is shown as a solid line curve. The best fit for T 1793 K is plotted as a dashed line. To get a flame profile the height of the burner relative to the laser beam axis was varied in steps of 0.25 mm. Each CARS spectrum takes 10 - 15 min. In Fig. 11 the measured temperature points are presented as circles. The theroretlcal curve is shown as dashed line. 

Equation (1) gives the actual relation between burning velocity and flow velocity at the x axis. There is a flame profile and a flow profile at the cross section along the tube ... 

Figure 20.19 Main zones in a laminar flame profile...

The primary advantage of EV burner designs is that their high mass flow, high velocity flame profile delivers more surface treatment per unit of time and can effectively lead to treatment productivity improvements. An increase in gap distance between the burner and the substrate to be treated is a key design feature, as are the following ... 

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