短螺旋型燃烧室旋流结构及气动边界发展规律数值模拟研究

Numerical Investigation on Structure of Swirling Flows and Evolution of Aerodynamic Boundary in Short Helical Combustors

关键词:  短螺旋型燃烧室  气动边界  旋涡结构  旋流流动

Key words:  Short helical combustor  Aerodynamic boundary  Vortex structure  Swirling flow

摘要:

短螺旋型燃烧室的头部轴线沿发动机周向与发动机轴线偏转一定角度，可以在保证燃烧效率不变的条件下有效缩短燃烧室轴向长度。短螺旋型燃烧室流场的最大特点是旋流流动单侧受限。为了研究头部安装角α变化对燃烧室旋流流动特性的影响，基于数值方法对短螺旋型燃烧室进行了计算分析。结果表明：随着α变化，旋流器下游旋涡依次出现对称环状、马蹄状、环状结构；随着α增加，气动边界逐渐出现并抑制旋流的周向扩张，导致流场出现不同的旋涡结构；不同α下的切向角动量随轴向距离增加而衰减，但α为35°和45°时，气动边界在非受限侧出现并对旋流产生约束，角动量衰减变慢；当α为0°，15°，35°，45°时，燃油液滴依次集中分布在旋流器下游两旋涡边缘、侧壁面和头部端壁、非受限旋涡边缘。本文研究了不同α下的旋涡结构及气动边界沿轴向的演化过程，为短螺旋型燃烧室进一步的设计与优化提供基础。

Abstract:

The swirler axis of short helical combustor is tilted a certain angle along circumferential direction relative to the axis of engine, which can effectively reduce the axial length of combustor while maintain high combustion efficiency at the same time. The prominent feature of the flow field in short helical combustor is the single confine of the swirling flow. To study the effect on the swirling flow of short helical combustor under different swirler fixing angles (α), the numerical methods were used to simulate and analyze. The relevant results show that: the vortex successively presents symmetric ring-like, horseshoe-like and ring-like structure as α varied.The aerodynamic boundary gradually appears and weakens the circumferential expansion of the swirling flow as α increased, resulting in different vortex type. The tangential angular momentum is decreased as the axial position increased under different α, but the aerodynamic boundary appears on the unrestricted side and restricts the circumferential expansion of swirling flow when α=35° and 45°, leading to a slower decline of angular momentum. The fuel droplets mainly distribute on the edge of the vortices downstream the swirler, on the sidewall and dome, and on the edge of vortex near the unrestricted side when α=0°, 15°, 35°, 45°, respectively. This paper investigated the vortex structure and the evolution of the aerodynamic boundary along axial direction under different α, which can provide the foundation for the further design and optimization of short helical combustors.