带拐弯混合管对波瓣混合器性能的影响

Effects of turning mixing duct on lobed mixer performance

针对波瓣混合器进行了一系列的数值计算和模型实验研究,揭示了带拐弯混合管对波瓣混合器性能的影响.实验结果表明:混合管长径比小于2时,带拐弯混合管会造成高温气流在出口截面呈月牙形分布,月牙形包围着一个回流区,该回流现象对引射性能不利,计算结果则验证了该气流分布,认为带拐弯混合管降低了波瓣混合器的引射效率,为改善其引射性能,应该加长混合管使得混合管的长径比大于等于2.计算结果还发现了波瓣混合器的最佳长径比为2,且该值不随面积比变化,和最佳长径比为6的圆管混合器相比,波瓣混合器可以有效缩短混合管的长度.另外,进一步给出了引射比与长径比的拟合关系式.

Based on a series of numerical computations and model experiments on the lobed mixer, the effects of turning mixing duct on the lobed mixer performance were re- vealed. The experimental results show that a crescent-shaped high temperature flow area is formed at the outlet cross section caused by turning mixing duct if the length-diameter ratio of mixing duct is less than 2. And a backflow zone is also found in the center of this area which is disadvantageous to the pumping performance. However, the numerical results not only verify the air flow distribution, but also show that the turning mixing duct lower the pumping efficiency of lobed mixer, and the mixer duct length should be increased for better pumping performance. To achieve a satisfied lobed mixer performance, the length-diameter ratio should not be less than 2. The numerical results also show that the optimum length-di- ameter ratio of lobed mixer is 2, which may not vary with the area ratio. Compared with pipe mixer whose optimum length-diameter ratio is 6, the lobed mixer could shorten the mixing duct effectively. Furthermore, fitting relations between the pumping ratio and length-diame- ter ratio are also presented.