Numerical Simulation On An Adjustable Length Of Flame Gas Burner

Flame furnace is a significant heat transforming equipment, in which the fuel chemical energy can be transformed into the heat energy in it, and then the heat energy is transformed to heated work piece. The performance of burner is always an important research field, because it decisive influence on energy consumption and temperature distribution in a furnace. It is easier for gas fuel to achieve complete combustion and less pollution to environment than solid or fluid fuel, thus it has been widely used in flame furnace. To adjust flame length for a tradition gas burner is usually done by increasing or decreasing heat load, but this measure can not meet any process requirement. Sometimes we want to achieve a condition that the flame length is changed without changing heat load Therefore, the adjustable length of flame gas burner has been discovered. Unfortunately, the results of current application are disappointing and the study on the theory of this kind of burner and its combustion characteristic is so little.So, the effects of thermal load and centre and air ratio between internal and external on combustion characteristic in a combustion chamber were studied by numerical models about a adjustable length of flame gas burner on the platform of Fluent6.3. The research content includes two parts, one is direct jet and the other is swirl jet. The combustion characteristics include temperature distribution, highest Temperature, velocity field, flame length, NO distribution and so on. The following conclusion has been achieved:On the direct jet condition:(1) The size of circulating zone remains unchanged with the β rising, but the strength of circulating zone is weakened gradually. The axis position of circulating zone moves backward with the heat load rising, however, moves forward with the β rising.(2) The front highest temperature rises gradually with heat load rising; Flame shape changes from fan shape to spindle shape; The length of flame grows longer with heat load rising; Temperature distribution tends to be more uniform, higher temperature zone expends gradually, and the temperature level goes up with heat load.(3) The length of flame grows longer with heat load rising or β rising, but the influence of β is greater than heat load. The highest temperature changes high and low with the β rising as β<0.5or β>0.5respectively, and it is the highest when β=0.5.(4) The emission concentration of NO increases with β rising, while slightly reduces with heat load rising.On the swirl jet condition:(1) The highest temperature becomes lower when swirl is added, and the influence when swirl is added at outer air inlet is less than the influence when swirl is added at inner air inlet. The influence degree becomes smaller gradually with a rising.(2) The flame length of situation of direct jet is shorter than swirl jet. Flame Length becomes shorter with a rising when outer or inner air inlet is added swirl. When a is fixed, flame length when inner air inlet is added swirl is shorter than when outer air inlet is added swirl.(3) The emission concentration of NO decreases when swirl is added. The emission concentration of NO decreases and the degree of drop becomes smaller gradually when a rising. When a is fixed, the emission concentration of NO when inner air inlet is added swirl is lower than the other.