边界条件对双级旋流器下游涡量的影响

Effects of Boundary Conditions on Downstream Vorticity from Twin-Stage Swirlers

关键词:  粒子图像测速法  数值模拟  旋流器  边界条件  漩涡

Key words:  PIV  Numerical simulation  Swirler  Boundary condition  Vortex

摘要:

使用PIV实验和CFD数值模拟的方法研究多个双级旋流器和单个双级旋流器下游的冷态流场，对比分析两种情况下，速度场分布、漩涡结构和涡量的变化规律，获得边界条件对双级旋流器下游漩涡结构的影响规律。PIV实验与CFD数值模拟结果在中心漩涡结构和涡量的变化规律上吻合得较好；单个旋流器情况下，由于旋流器和壁面之间的相互作用形成了两对角涡，多个旋流器情况下，由于旋流器旋流之间的相互作用而形成了一个旋流器边界区域漩涡(边界涡)；单个旋流器情况下的中心漩涡涡强在主燃孔射流之前始终低于多个旋流器情况，其中，距离旋流器出口10mm处，数值模拟结果显示单个旋流器中心漩涡涡量是多个旋流器的92.4%，而PIV实验结果显示该值为90.0%；单个旋流器情况下主燃孔射流对中心漩涡的加强作用较多个旋流器更加显著。正是由于不同边界条件下，外围流体处的漩涡结构不同导致了中心漩涡涡量变化规律不同。

Abstract:

PIV experiment and numerical simulation were utilized to study the non-reaction flow field downstream of the single-swirler and the multi-swirler，which had the same twin-stage structure. Velocity fields，vortex structures and variation of vorticity in both cases were compared and analyzed to study the effects of different boundary conditions on vortex structure of twin-stage swirler. The results of PIV experiment and numerical simulation agreed well on the structure and variation of the central vortex vorticity. In the single-swirler case，two couples of corner vortex were formed due to the interaction between the swirl-flow of swirler and walls，and in the multi-swirler case，a vortex located on the boundary between two swirlers called boundary vortex was formed due to the interaction between the swirl-flow of the swirlers. The vortex intensity of the central vortex in the single-swirler case was always smaller than that in the multi-swirler case before the jets from primary holes，specifically，at a distance of 10mm from the outlet of the swirlers. The results of numerical simulation show that the vortex intensity of the central vortex in the single-swirler case was 92.4% of that in the multi-swirler case，while the results of PIV experimental show that the value was 90.0%. The jets from the primary holes enhanced the vortex intensity of the central vortex，and such effect was more significant in the single-swirler case. The difference of vortex structure located in external fluid under different boundary conditions resulted in the different variation of the central vortex vorticity.