中心分级燃烧室冷态流场的大涡模拟

Large-eddy simulation of non-reacting flow in a central staged combustor

对中心分级燃烧室冷态流场进行大涡模拟,研究主燃级叶片安装角对流场中大尺度湍流结构运动特性的影响,亚格子尺度湍流及其对大尺度流动结构的影响使用动态Smagorinsky涡黏模型描述。结果显示:流场纵向截面上涡量云图揭示了流场上游出现内外两层涡结构,分别发源于文氏管尾缘和套筒末端,随旋流强度增加,涡层径向尺寸变宽,中心回流区长度缩短。主燃级叶片安装角从20°增加到40°时,流场上游角涡显著减少。下游低压核心与流线束环绕中心重合且偏离轴心,并在流场中下游产生进动涡核。中心轴线上的轴向速度功率谱密度表明,随着叶片安装角增加,涡核进动频率升高。

Large-eddy simulation （LES） was used to explore non-reacting flow fields of the central staged combustor and investigate effects of the vane angle of swirler primary stage on the large-scale flow struc- tures. Smagorinsky eddy viscosity model was used to describe sub-grid turbulence flow and its influences on the large-scale flow structures. The contours of transient vorticity magnitude on x-z plane show that there are two vortex layers in upstream of the flow field. The inside layer derives from the end of the venturi and the outside one from the outer tube tail. With the increase of swirl strength, radial distance of the two vortex lay- ers becomes larger, and the axial length of center recirculation zone is reduced. The upstream comer vortex is significantly decreased when the vane angle increases from 20° to 40°. In downstream,the position of low pressure core and the streamline surrounded center overlaps. The overlap region deviates from the axis of chamber, and precessing vortex core generates in downstream of flow field. The axial velocity power spec- trum density on the chamber axis shows that precessing frequency of the vortex rises with the increase of angle.