网格湍流对剪切层中预混火焰结构的影响

本文研究网格湍流对射流剪切层以及建立在其中的预混火焰的影响。利用热线风速仪测量射流的速度场,发现网格湍流使剪切层内湍流强度明显降低,抑制了低频速度脉动,同时增加了湍动能在小尺度脉动上的分配,使湍流更趋于各向同性,这表明网格湍流抑制了剪切层内的大涡和拟序结构。用细丝热电偶测量了火焰温度,结果显示网格湍流使火焰前峰的低频大幅摆动减少,小尺度皱褶增加,火焰区平均温度更高,说明网格湍流有利于剪切层中预混火焰的强化和稳定。

INFLUENCE OF GRID TURBULENCE ON THE STRUCTURE OF PREMIXED FLAMES IN SHEAR LAYER

The influence of grid turbulence on the shear layer of a jet and the premixed flames embedded in it was investigated in the present study. Velocity field of the jet was measured by using hot wire anemometry. It was found that grid turbulence reduced turbulence intensities in the shear layer and suppressed low frequency fluctuation. Also, energy contained in small-scale fluctuation was increased and turbulence became more homogeneous. The results indicate that grid turbulence inhibits the formation of large-scale coherent structure in the shear layer. Flame temperature was measured by using a fine-wire thermocouple. It was found that grid turbulence reduced low frequency fluctuation of the flame fronts, increased the small-scale wrinkles and elevated mean temperature of the flame zone. The results show that grid turbulence will benefit the enhancement and stabilization of premixed flames in shear flow.