齿型扩口对旋流燃烧器流动特性影响的研究

Effect of gear baffle on isothermal flow from radial bias combustion burner

采用一维热膜探针多方位转动法 ,在径向浓淡旋流煤粉燃烧器冷模试验台上 ,研究了在齿型和普通型两种中心扩口下旋流煤粉燃烧器出口气流的空气动力特性 .试验得到了冷态旋转射流的时均速度、湍流应力、偏斜因子的测量结果 .分析测量结果可见 ,齿型中心扩口下中心回流区直径减小 ,相对回流率较普通型中心扩口增加 2 0 % .同时在中心回流区边界附近湍流脉动强度明显提高 ,湍流正应力提高 1倍以上 ,湍流剪切应力提高 3倍以上 ,在主流区湍流瞬时速度的概率密度函数更快趋向于完全随机的高斯分布 .在齿型中心扩口下 ,出口射流的回流强度及湍流脉动强度的提高 。

The aerodynamic properties of swirling jet coming out from the swirl burner were studied with the structures of a central gear baffle and an ordinary baffle on a cold model test rig of Radial Bias Combustion (RBC) burner using the rotating hot film probing method to measure the mean velocities, turbulent stresses, skewness coefficient of isothermal swirling jet. The measurements show that the diameter of the internal recirculation zone (IRZ) reduces under the structure of central gear baffle, and the related reversed ratio increases by 20 percent. The turbulent normal stresses double while turbulent shear stresses triple. The probability density function of the mean stream instantaneous velocity approaches a Gauss distribution faster. Because of the increase of reversed flow and turbulent fluctuation intensity in the exit swirling jet of RBC burner, the process of pulverized coal combustion can be enhanced by the structure of gear baffle.