| OCR Text |
Show combustion capacity air ratio regenerative cycle time pre heat air temperature exhausted gas composition 25, 50, 75, 100% (=1.74MW) 1.05 30, 60sec 700*C-1,200'C and 25'C (conventional low NOx burner) COz, Oz, CO, NOx by gas analyzer through the gas sampling pipe at the position in Fig.8 Test results are shown in Table 1. NUMERICAL ANALYSIS Numerical conditions are as follows : 2mX2mX2m : 1/2 model by symmetrical boundary condition : Fig.10 : conventional low NOx burner using atmospheric temperature air : regenerative center gun type burner : regenerative eccentric gun type, namely distributed combustion type burner calculation grids : case 1,2 44X18X150=118,800 cells case 3 47X18X150=126,900 cells fuel, air injection hole size : Table 2 model furnace dimension calculation area calculation case case 1 case 2 case 3 code combustion model NOx walI condition gas radiation pre heat air temperature physical property FLUENT V4.4 PDF thermal NO and prompt NO wall temperature 1,423'K walI emissivity 0.8 considered HzO, COz measured temperature air (1,200*0 thermal conductivity 0.0891 W/m.k dynamic viscosity 5.27X10"5 Pa.s In analyzing regenerative combust ion,we analyze the first stage combustion calculation by injection from X=0m position, then using these results as initial value we analyze the second stage combustion by injection from X=10m position. In the case 3, fuel hole resides lower than air hole at the first stage and upper at the second stage. We show calculation result in Table 3, Fig.11, 12, 13, and 14. From Fig.11, velocity vectors show the characteristic gas flow of eccentric gun type in comparison with case 2 and case 3, that is,stream line of recirculation flow penetrates into the inner of main stream. From Fig.12, temperature distribution shows high temperature zone over 2,000'K decreases in case 3 than in case 2, and case 3 composes one low temperature zone in around fuel distributed injection position. From Fig.13, oxygen distribution shows the lowest oxygen combustion generates in case 3 among 3 cases, and very low oxygen concentration zone generates clearly in around eccentric fuel gun position, but the peak Oz level in case 2 and case 3 is about 2%, then we need more real measured Oz datas. From Fig.14, NO distribution shows peak NO generates just behind fuel injection hole in case 3, that is why, high oxygen concentration zone exists in the outside of low oxygen concentration zone. We can observe the characteristics of regenerative burner. From Table 3, maximum temperature and maximum NO in case 3 are larger than in case 2, but average NO in exit is smaller, that is why, these datas are related with oxygen |
