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Show 3. VM Burner Experimental and Modeling Results F or all the results reported here on the VM burner natural gas fuel was used, but alternative fuels such as propane or oil could also be used. The experimental measurements were obtained on a 30- 50 kW laboratory scale VM burner and on a 340 kW industrial version under different operating conditions. 3.1 Oxy-fue/ Flame Emission Studies The light emission observed from a flame is one of the most characteristic features of the flame. By visually observing the flame one can obtain information on flame length, luminosity, and stability in the integrated spectral range of the human eye (400-700run). The visual observations of the VM burner for increased O2 injected in the inner tube shows the flame length decreases, stability (fluctuations in overall flame shape) increases, and luminosity decreases. Measurements on the observed visible flame length for a constant firing rate of 1 MW are shown in Figure 2. With 0% O2 in the inner tube the flame length is approx. 2.6m, but with the addition of only 17.5% O2 in the inner tube the flame length decreases by 50%. Also, shown are the gas velocities at the burner entrance for the different gases. Since the firing rate is constant there is no change in the natural gas velocity from the middle tube. There is a decrease in the outer O2 velocity of 17.5% and an increase in the inner O2 velocity of82.5 % over the range of conditions test (0-17.5% inner O2 injected). To obtain a greater understanding of the physical and chemical processes, specific spectral regions of flame are studied using UV -visible imaging techniques. These techniques provide an easy method for the detection offree radicals, e.g., OH, CH, and C2, that provide information about the reaction zone[ 4]. The radicals are important intermediates species for chain propagation reactions in CH4 combustion and CO and NOx formation [3]. The fonnation of these radicals by chemical reaction results in highly excited states that emit radiation at characteristic frequencies. Monitoring the quantity of radiation emitted provides qualitative infonnation on the location and abundance of a particular species. 6 |