| OCR Text |
Show t4. 1.16 1.12 1.08 5 Fuel: C3H!(97vol%HN2(3vol%) 0.053m Vh, 323K Air O.(4vol%), 15m3/h, 1223K Nitrogen (N2) Flue gas Carbon dioxide (C02 j- •Helium (He) _ i i i i i_ properties between different diluents could result in the difference of mixing processes between fuel and diluted air. In the turbulent diffusion flame, however, the mixing process becomes complex since the turbulent diffusion takes dominant roles. In light of this, the influence of diluents on the highly preheated air combustion still needs further investigations. 50 100 150 200 250 300 Distance from Air Inlet [ m m ] Since the N O x emission mainly depends on the flame temperature, the influence of diluents on the N O x emission has the same tendency as on the temperature. It should point out that both thermal-NOx and prompt-NOx are hardly formed when the flame temperature is lower than about 1800 K. A s can be seen, the N O x emission tends to be zero when the oxygen concentration is as low as 4 vol%. Figure 14 Influence of diluent on temperature uniformity 2" 2350 Fuet C^H1(97vor»/.) + NJ(3vol%) 323K 0 OSSNm'/h Air dilated by flue gas, 0,( 15vol%) ISNm'/h NOx 1.5 1 f-B 1.4 1.3 T„-1123K ' T.,=1223ICV\ /T.,=1323]t\v \ /T„=1423K~\^^ \\ Fuel: C,H,(97vol%) + N2(3vc4%) 323K, 0.053Nm'/h Air diluted by flue gas, O2(15vol%) 15NmVh - 1100 1150 1200 1250 1300 1350 1400 Preheated Air Temperature [K] Figure 15 Influence of air temperature on maximum flame temperature and N O x emission at furnace exit 0 50 100 150 200 250 300 Distance from Air Inlet [ m m ] Figure 16 Influence of air temperature on temperature uniformity r Influence of preheated air temperature. In the case of flue gas diluted air with oxygen concentration of 15 %, the combustion was simulated under different preheated air ». |
