Effects of Swirl Numbers、 Flow Rates of Flue Gas and Jet Spray Angles on Combustion Efficiency and Formation of Pollutants in a Boiler
| Autor: | Ming-Chieh Hsu, 徐明杰 |
|---|---|
| Rok vydání: | 1999 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 87 In this research a modified commerical boiler, which burns diesel oil, is used to study the combustion characteristics and pollution of the exhausting products under various operating conditions. In our experiments, the oil-burner designs are modified, and the different equivalence ratios and swirl numbers can be controlled by adjusting fuel-air ratio. The controlling rangesof the various experimental parameters include equivalence ratio from 0.8 to 1.1, swirl number from 0 to 1.0, recirculated flue gas from 0 to 12 %, and jet spray angle including45°、60° and 80°. These controlling variables are used to study effects of the combustion efficiency and pollutant formations; eventually, we certain hope that optimized operating conditions can be found. A photographic technology is used to study the flame structures to help us understand- ing the behaviors of the flame under various operating condition. From the experimental results, we find when the strength of swirl increases, the temperatures along the injection direction of burner increases, but the temperature along the radius direction decreases. At the same time, NO concentration increases near the main combustion region, and decreases in the other region. The temperature in the flue is much lower than in combustiob zoon. The radius distribution of product concentration in flue is quite uniform due to the mixing effect in up- stream. At equivalence ratio0.9, the temperature distribution in combustion zone decrease, when the flow rate of recirculated flue gas increase. When the flow rate of recirculated flue gas increases, the temperature in the flue increase; however, the over- all concentration in any region decreases obviously. Through a series of experimental works, the certain best combinations with higher combustion efficiency and lower NO emission can be found. One of the combination is equivalence ratio at 0.9, the flow rate of recirculated flue gas at 8 %, swirl number at 0.4 and spray angle at 80 degree. The deduction rate of NO is 20~25 %. Flame structures display that when the flow rates of the recirculated flue gas increase, the flame colors in primary com- bustion region changed gradually from white-yellow to orange-red. The flame outside of the primary combustion region exhibits the red color which is due to the formation of CO2 and water vapor. On the other hands, with the increase of swirl, the streamlines of the flame changed gradually from smooth to strongly disturbance |
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