波瓣帽罩结构和脊线对混合排气系统性能影响

Effects of Lobe Cap and Crest Line on Performance of Mixing Exhaust System

关键词:  波瓣混合排气系统  帽罩  波瓣脊线  热混合效率  总压恢复系数 

Key words:  Lobed mixing exhaust system  Cap  Lobe crest line  Thermal mixing efficiency  Total-pressure recovery coefficient

摘要:

为了明确波瓣帽罩结构和不同脊线形状对混合排气系统气动热力性能的影响,采用基于Navier-Stokes方程组的三维数值模拟方法对含帽罩结构以及脊线发生变化的4个波瓣混合器模型进行了定量研究,并将研究结果同原始波瓣混合器模型进行了对比。结果表明,帽罩结构能改善波瓣周围的流场,减小由于扩张角过大所导致的边界层分离,从而缩小流动损失；波瓣脊线形状的改变虽然能改变波瓣混合器附近的流场,从而减小流动损失,提高总压回复系数,但与此同时,脊线的改变也会影响主、次流间的混合,降低热混合效率。同原型相比,改变波瓣脊线加入帽罩结构后,研究的波瓣混合器总压恢复系数的最大增幅为1%,而热混合效率的最大降幅却为11%。 

Abstract:

In order to clarify the effects of lobe cap and different crest lines on the aerodynamic and thermal performance of the mixing exhaust system, quantitative study on four lobed mixers with cap structure and changed crest line was carried out through the three dimensional numerical simulation based on Navier-Stokes equations, and the research results were compared with original lobed mixer. The results show that cap structure can not only improve the flow field near lobed mixer, but also reduce the boundary separation and flow loss. Besides, the change of crest line can improve the flow field near the lobed mixer, reduce the flow loss by controlling boundary separation due to overlarge penetration angle, and increase the total-pressure recovery coefficient, but meanwhile it can also have a negative effect on mixing between core and fan flow and reduce the thermal mixing efficiency. Compared with the original model, after lobe crest line is changed and cap is added, the largest increase rate of total-pressure recovery coefficient of lobed mixers is 1%, and the largest drop of thermal mixing efficiency is 11%. 