旋流扩散燃烧中旋流数对热NO生成的影响

本文对旋流扩散燃烧进行了数值模拟，研究旋流数对热ＮＯ生成的影响，其中对湍流采用Ｒｅｙｎｏｌｄｓ应力方程模型，对燃烧采用ＥＢＵ－Ａｒｒｈｅｎｉｕｓ模型，对热ＮＯ生成采用设定ＰＤＦ的模型。预报了不同旋流数下轴向和切向的平均和脉动速度、温度和ＮＯ浓度，指出随着旋流数的增大，计算得到的出口平均ＮＯ浓度首先升高然后下降。这一趋势和本文作者最近的实验结果的趋势一致．随着旋流数的增大，湍流脉动首先下阵然后升高，而进口附近的温度上升，二者综合效果造成上述趋势、因此在实际燃烧器中，完全靠改变族流数来控制ＮＯ生成是不现实的。应该采取其他方法来降低ＮＯ的生成。

ON THE EFFECT OF SWIRL NUMBER ON THERMAL NO FORMATION IN SWIRLING DIFFUSION COMBUSTION

The effect of swirl number on thermal No formation in swirling diffusion combustion is studied by numerical simulation, using the Reynolds stress equation turbulence model, EBU-Arrhenius combustion model and presumed-PDF NO formation model. The prediction results give the axial and tangential averaged and fluctuation velocities, temperature and NO concentration for different swirl numbers. It has been found that as the swirl number increases from 0 to 1, the mean thermal NO concentration at the exit at first increases, and then decreases. The highest NO emission occurs at the swirl number of 0.4-0.5. This tendency is in agreement with that observed in experiments. It is a result of the combined effect of turbulence and temperature change caused by changing the swirl number. Hence, in practical combustors, it is unrealistic to reduce the NO formation by changing the swirl number. Other measures should be taken to reduce NO formation.