地沟油生物柴油在旋流喷嘴中的雾化实验及模拟

Experiment and simulation of atomization of drainage oil biodiesel in swirl nozzle

对地沟油生物柴油在旋流雾化喷嘴中的内部流场及外部流场进行数值模拟,考察了喷嘴孔径、旋流芯螺距、螺柱槽道横截面积和槽道形状等结构参数对出口雾化速度及索特平均直径的影响,通过实验对模型进行了验证。结果表明,0.7 mm孔径的喷嘴的韦伯数最大,索特平均直径与雾化锥角最优。螺距4mm的喷嘴雾化特性最优,旋流芯螺距越小,流体在喷嘴内旋流次数越多,阻力损失越大,流体在切向分量上速度越大。梯形槽道的雾化效果最好,相同横截面积下槽道的水力直径越大,雾化效果越好;截面积1 mm^2槽道的喷嘴最优,槽道横截面积越小,流体在槽道中的湍流程度越大,流体内部剪切应力越大,液体表面不稳定波急剧增大。

The internal and external flow fields of drainage oil biodiesel in the swirl atomization nozzle were numerically simulated by changing the nozzle diameter, swirl core pitch, stud groove cross-sectional area, groove shape and other structural parameters, and the atomization velocity and cable average diameter at the outlet were obtained. By comparison, the influence of different parameters on atomization was studied, and the model was verified by experiments. The results showed that the Weber number of 0.7 mm aperture, Sauter mean diameter and atomization cone angle were the best. The atomization characteristics of a nozzle with a screw pitch of 4 mm were optimal. With the decrease of the screw pitch of the swirl core, the time of the fluid swirls in the nozzle, the resistance loss and velocity of the fluid in the tangential component increased. Trapezoidal groove had the best atomization effect. With the increase of the hydraulic diameter of groove shape, the atomization effect was promoted at the same cross-sectional area. The nozzle with the groove cross-section area of 1 mm^2 was the best, because the smaller the groove cross-section area was, the greater the turbulence degree of the fluid in the groove, the greater the internal shear stress of the fluid, and the sharp increase of the instability wave on the liquid surface. Comparison of tangential velocity showed that the nozzle with the groove cross-section area of 1 mm^2 was optimal.