Flame measurement

Coppalle, A., and D. Joyeux. 1994. Temperature and soot volume fraction in turbulent diffusion flames Measurements of mean and fluctuating values. Combustion Flame 96 275-85. 

Following are some of the results of Bichel s flame measurements using a lOOg sample of ezpl ... 

Experimental designs were used to set the operational conditions of a flow injection method which combines continuous acid extraction, preconcentration and flame measurement... 

Effective Over-all Chemical Reaction Orders. Values of the effective over-all reaction order a have been obtained by many investigators. The published data are not comprehensive enough to permit any definite correlations to be made between reaction orders, pressure, temperature, and mixture ratios (26). One or more of the three basic types of flame measurements are used in determining reaction orders, these being flame thickness, burning velocity, and quenching distance. Reaction order data are available in the more recent literature for the following mixtures, obtained by the indicated method for various pressures, temperatures, and mixture ratios. 

The formed free atoms absorb the light at a characteristic wavelength from a hollow cathode lamp that is positioned on one side of the flame. A spectrophotometer with a grating monochromator located on the other side of the flame measures the intensity of the light beam. Because absorption is proportional to the number of free atoms that are produced in the flame, the light energy absorbed by the flame is a measure of the element s concentration. The FLAA technique is relatively free of interelement spectral interferences, but it has the sensitivity that is inferior to ICP-AES or GFAA. 

In exemplarily flame measurements conducted at the LTT-Erlangen (Will et al., 1996), flame temperatures were determined by emission spectroscopy or coherent anti-Stokes Raman scattering (CARS) thermometry depending on the maximum soot concentration. Typical temperatures are in the range of 1800 K in the middle of the flames and up to 2100 K in the outer regions where the reactions take place. A typical measurement setup for two-dimensional LII investigations is shown in Figure 10. 

Figure 29. Partial list of species that are likely amenable to laser flame measurements...

Also described in Ref. k is a new optical layout for LV data acquisition which permits a significant increase in the overlap between the Raman and LV probe test volumes. The worth of the various correlations of density and temperature with velocity is critically dependent upon the accuracy of this overlap at all flame measurement positions. Thus, one must either lock the Raman and LV probes together in a precise but movable fashion -a rather difficult procedure for the precision required for bench scale" laboratory flames - or else translate the flame. 

In fuel-rich flames, the CO should be in local chemical equilibrium, and hence the partial pressure of CO can be calculated from the local temperature and the measured fuel and air flowrates. Thus, a comparison between measured and calculated CO levels can serve as a validation of the diode laser technique for flame measurements. Such a comparison is shown in Figure 5 for equivalence ratios in the range <(> = 1.04 - 1.37. The data points shown represent the average of several observations on separate lines including ground state (v" = 0) and excited state (v" = 1) transitions. The agreement is consistently within the experimental uncertainty of 5%. 

Temperature proflles in spray flames were similar to those previously measured in gaseous diffusion flames. Measurement of temperature by coated thermocouple was more accurate than measurements by suction pyrometer within the temperature range and particular conditions of the spray flames investigated. Changes in temperature within the flame could be explained in terms of convection, reaction, entrainment, and dilution. 

Fig. 9. Discharge time response curves in the flame measured at the laser beam position a 100 pg/mi In, b 100 pg/ml In with 1 pg/ml K, c 100 pg/ml In with the cathodes moved into the flame 35)...

The precision of the flame measurement step was established using aqueous calibration standards (Table 15.11). The accuracy of the method was evaluated using various petroleum materials spiked with selenium dioxide and dilaurylselenide. The results (Tablel5.III) show an average recovery of 100% and suggest that the method is accurate within the precision of the measurement. 

Perrin, M., Imbach, J., Albert, S., Mariasine, J., and Quinqueneau, A. "Application of Advanced Instantaneous In-Flame Measurements Techniques in an Industrial Flame with Preheated Air." Proceedings of 1995 International Gas Research Conference, edited by D. A. Dolenc, 2406-15. Rockville, MD Govt. Institutes, 1996. 

Three of the burner settings were varied in the experiments air distribution between primary and secondary ducts (air ratio, AR, expressed as frachon of secondary air over the total air flow rate) and the swirl numbers of both air streams (SI and S2, respectively both reported here as a percentage with respect to maximum swirl level). Detailed in-flame measurements revealed significant changes in the distribution of species and temperatures inside the flame when AR, SI, or S2 were varied... 

In oxy-burner testing, generally two types of measurements are involved (i) measurements inside flames and (ii) global measurements in the furnace. In-flame measurements include chemical composition, flame temperature profile, and optical properties. Global measurements include flame shape, emissions, heat flux, and measurements taken on the load. Figure 27.13 shows typical measurements and their locations in an oxy-pilot furnace. 

The term atomic absorption refers to the absorption of energy from a light source, with a consequent decrease in the radiant power transmitted through the flame. Measurement of this absorption corresponds to atomic absorption spectroscopy. 

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