椭圆形切扇修形对波瓣混合器掺混性能影响

Numerical investigation in the effect of oval scalloping modification on the aerodynamics performance of lobed mixers

在保证面积不变的情况下,选取不同的长轴、短轴,对波瓣混合器进行椭圆形切扇修形,研究切口深度与宽度对波瓣混合器掺混性能的影响规律。使用商用CFD软件对流场进行数值模拟。结果显示,对波瓣侧壁进行切扇处理会加强流向涡的强度,切扇越深,流向涡强度越大;切扇波瓣流向涡的耗散速率要大于基准波瓣混合器的流向涡耗散速率,预示着更为高效的掺混;引射系数与切口深度成正比,而总压恢复系数与切口深度成反比。考察了两种衡量热混合效率的模型并对其信度进行了比较,发现在x=0.4 m之前切扇可以提高热混合效率,而在x=0.4 m之后,基准波瓣混合器热混合效率要大于切扇波瓣混合器。

Oval scalloping modification on a lobed mixer was conducted. A set of semi-ellipsis of the same area but with different length of major and minor axes which represent the depth and width of scalloping respectively was adopted. The effect on aerodynamic performance of the lobed mixer was studied in this paper by CFD software in terms of streamwise vorticity,pumping factor,total pressure recovery coefficientand the thermal mixing efficiency. The results show that deeper scalloping attains strongerstreamwise vorticity. The dissipation of streamwise vorticity of the scalloped lobed mixers is faster than that of baseline lobed mixer. Pumping factor is directly proportional to the depth of the notch while total pressure has an inverse relationship with the depth. The fidelity of two different models for thermal mixing efficiency is evaluated. It is revealed by comparison thatscalloping enhances thermal mixing efficiency before x = 0. 4 mm. After that the baseline lobed mixer has a larger value than the scalloped mixers investigated.