波瓣混合器涡系结构及射流掺混机理的数值研究

借助流体力学软件ANSYS CFX,对波瓣混合器射流掺混流场进行了全三维定常数值模拟,研究了流场中各涡系结构的形成机理及发展过程,并详细探讨了其加速射流掺混过程的作用机制.结果表明:基于SST(shear stress transport)模型的封闭N-S方程能较好地模拟波瓣混合器射流掺混过程,波瓣特殊几何外形诱导产生的流向涡主要通过扭曲内外涵交界面的间接方式加速射流掺混过程,波瓣下游剪切层中K-H(Kelvin-Helmholtz)不稳定性发展而成的正交涡是直接加速射流掺混的关键因素,波谷附近二次流之间的相互作用所产生的通道涡对该区域内的射流掺混有明显的加速作用,受波瓣前缘切割的边界层在径向压力梯度作用下沿波瓣表面卷起而形成的马蹄涡对射流掺混的影响不是特别明显.

Numerical investigation on vortex structure and jet mixing mechanism in lobed mixer

With computational fluid dynamics software ANSYS CFX,the three-dimensional steady numerical simulation was conducted on the jet mixing flow of lobed mixer to study the formation mechanism and development process of the vortex structure,and its functional mechanism of the forced jet mixing.The results show that based on the SST(shear stress transport) model,the closed N-S equation can simulate the jet mixing process in lobed mixer excellently.While the streamwise vortices induced by the special geometry of lobed mixer depend on an indirect way of twisting the interface between core and bypass flow to accelerate the jet mixing process,normal vortices formed on the promotion of K-H(Kelvin-Helmholtz) instability accelerate the jet mixing directly.The passage vortices are produced by the interaction between the radical inward secondary flow and the low momentum fluid along the wall moving toward the lobe's crest where the passage vortices have an obvious promoting effect on jet mixing.Under the radical pressure gradient within the lobed mixer,boundary layer cut by lobe's leading edge rolls up along the surface of the lobe and forms the horseshoe vortex,and it has little effect on jet mixing.