OCR Text |
Show Figure 22 shows the effect of oxygen nozzle angle 0 on N O x emission. Four levels of 0 (0, 5, 10 and 15 degrees) were tested with L set at 100 m m . In general, N O x emission decreased with the increase in 0. Larger 0 generates more wide-spread flame, enhancing the self-induced E G R and flame radiation. As demonstrated in Figures 17-22, NOx emission from the FDI flat flame oxy-fuel burner is influenced by various parameters such as V, L and 0. W h e n generating a unique flat flame with the self-induced EGR, these burner parameters determine the flame characteristics that influence temperature, residence time in high temperature region and distribution of gas species including in-leaked nitrogen. Each of the parameters has shown both positive and negative impacts on the N O x formation. N O x levels are somewhat the combined results. While it enhances mixing between natural gas and oxygen and possibly increases flame temperature, the increase in V enhances the self-induced E G R to reduce flame temperature and NOx . Larger L enhances the self-induced E G R to reduce flame temperature but it may enhance the entrainment of flue gas that contains in-leaked nitrogen. While it generates more wide spread flat flame with enhanced self-induced E G R , the increase in 0 enhances the mixing between natural gas and oxygen thereby increasing flame temperature and N O x emission. Further investigation on the detailed characteristics of the FDI flat flame is needed. Numerical analysis will be of use along with experimental approach. Figures 23 and 24 show the effect of nitrogen content on NOx emission. Nitrogen was doped into either the oxidant as shown in Figure 23 or the fuel gas in Figure 24. N O x emission increased as the nitrogen content in the oxidant or the fuel increased. The effect of nitrogen content on the increase in N O x depends on the burner parameters. Larger 0 or V resulted in lower N O x emission at high nitrogen content in the oxidant. W h e n nitrogen was doped into the oxidant show in Figure 23, lager 0 or higher V resulted in lower N O x at an identical nitrogen content. The effect of L is not clear. For all the burner parameters tested, N O x emission increased very steeply when nitrogen content in creased from 0 to 5%. N O x emission appeared to saturate to a certain level, depending on the burner parameters. W h e n nitrogen was doped in the fuel shown in Figure 24, clear effect of burner parameters such as V, L and 0 on N O x emission was no observed. The results of the FDI flat flame oxy-fuel burner are summarized in comparison with the generic burner and the FDI burner. Total radiative heat flux of the FDI flat flame oxy-fuel 12 |