Effect Of Declination Angle Of Air Under The Arch On Flow Characteristics Of A Scale Model Of A Down-fired Utility Boiler With Swirl Burners

China is one of a few countries which has hard-to-burn fuel in abundance inthe world, as the policy about enegy and environment, the W-stype boiler has agreat future. But it is difficult for burning and burn-out with hard-to-burn fuel.W-stype boiler with swirl burners is a main mean for it. As to a300-MWe W-stypeboiler with swirl burners,a1:10-scale version of the furnace is performed toinvestigate the effect of the declination angle of vent air and staged air on flowcharacteristics of the furnace,by smoke followed and IFA300constant-temperatureanemometer system.Keeping the ratios of various air，by means of smoke followed, the inject pathof various declination angle of vent air and staged air and the mixed situation aresurveyed. And the experiment found the following.With a28°declination angle of vent air, the flow in the furnace has a goodsymmetry,but the inject of vent air is not stable. As the declination angle of vent airincreased, the stability and declination of the inject of vent air has a great improving.However, as the declination angle to45°the flow in in the furnace is dip and thedownward flow near the front wall got further than near the real wall.To the stagedair,when the declination angle30°, the inject has a good rigidity, and aunsatisfactory declination effect. As the declination angle increased to40°, thedeclination effect has a great improving,but the downward flow can not penetratethe staged air always.Keeping the ratios of various air, using an IFA300constant-temperatureanemometer system, cold air experiments on a scale model of a300-MWe W-stypeboiler with swirl burners was performed to investigate the effect of the declinationangle of vent air and staged air on flow characteristics of the furnace.Keeping the declination angle of satged air30°, when the angle of vent air is28°,35°and40°, the flow field in the furnace has a good symmetry. As the angle ofvent air increased, the mixing of downward airflow and vent air was delayed andthe dimensionless penetrating depth increases slightly, but not able to penetrate thestaged air. At a vent-air angle of45°, the flow field in the furnace was deflected.The downward airflow near front wall can penetrate the staged air and get to thefurnace hopper bottom. However the dimensionless penetrating depth of downward airflow near rear wall is decreased by the downward airflow near front wall pushingrear wall. And downward airflow near the rear wall began to turn upward in theregion of the vent air nozzle. Considering the symmetry of the flow field and thedimensionless penetrating depth, the best angle for the vent air is40°.Keeping the declination angle of vent air28°, a cold air experiment wasperformed to investigate the effect of the declination angle of staged air on flowcharacteristics of the furnace. As the angle of staged air increased, the flow field inthe furnace has a good symmetry and the dead recirculation zone in the furnacehopper reduced. When the angle of staged air is30°, the staged airs between thefront and rear walls crash seriously along the horizontal direction, and has a biggerresistance to the downward airflow. If increasing the declination angle of staged air,it helps weaken the crashing and resistance. With the angle of staged air increased,the dimensionless penetrating depth of downward airflow increases slightly, but forthe swirl burners, the downward airflow decay fast and can not penetrate the stagedair. Then the main role of the staged air is providing oxygen for combustion.Considering the symmetry of the flow field, the dimensionless penetrating depthand staged air washing the wall the furnace hopper, the best angle for the vent air is40°...