两相圆湍射流大颗粒调制作用的PDPA实验研究

PDPA EXPERIMENTAL STUDY OF TURBULENCE MODULATION IN A ROUND TURBULENT JET LADEN WITH LARGE PARTICLES

采用相多普勒颗粒分析仪(PDPA)测量了雷诺数为8500的两相圆湍射流速度场,研究了两种大粒径颗粒对湍流的调制作用。发现在相同气载比条件下,大粒径颗粒加入后,在射流近场区域(X/D<10)气相湍流度增强,沿着射流中心轴线轴向和径向气相湍流度增强;较小粒径颗粒加入后削弱气相湍流度。在射流远场X/D=20截面,较大粒径颗粒的加入会削弱气相湍流度,但其削弱程度不如小粒径颗粒。随着粒径的增大,两相射流湍流的气相湍流度进一步增加。

Two-phase velocity fields in a round turbulent jet with Reynolds number 8500 were measured by Phase Doppler Particle Analyzer （PDPA）. The turbulence modulations by large particles in two different diameters were then studied. Under the condition of the same particle-loading ratio, the gas-phase turbulence intensities are augmented by large particles both in the axial and radial directions in the near-field regions （X/D 〈10）, while the gas-phase turbulence intensities are attenuated in the same regions when the flow is loaded with small particles. The turbulence intensities are higher than those in a particle-free jet along the jet axis line for the case loaded with large particles. In the jet far-field, at the profile of X/D=20, the turbulence intensities are attenuated when the large particles are added into the jet, but still larger than those in the existence of smaller partides. It is observed that the augment of turbulence by particles increases with the particle＇s diameter.