Abstract

The emission characteristics of non-premixed impinging flames are investigated using PIV experiments and numerical simulations. Different coflow conditions are conducted to focus on the pollutant emissions with the flame-wall interaction. Results show that flame dynamics obtained from experiments are in good agreement with that calculated from numerical simulations, and flame instability is intensified in near wall region in large coflow velocity case. In addition, the increase of coflow velocity may promote CO production, especially in low mean mixture fraction region (0.07-0.26). The distribution of CO is dispersed in large coflow velocity case, which is related with a strong convection and diffusion process. Besides, it is found that the decrease of flame temperature and the large wall quenching distance is observed with the increase of coflow moisture content, which is associated with the weakened combustion progress and the migration of reaction zone due to the decrease of O₂ concentration in coflow mixture and the increase of specific heat capacity. The decrease distribution of local emission indexes of CO and NO is also shown in high coflow moisture content case, which can weaken the production of CO, thermal NO and prompt NO, and accelerate the consumption of NO. Moreover, CO reduction occurs mainly in high CO concentration region, while NO reduction is observed in the whole flow field. Results indicate that small coflow velocity and high coflow moisture content are beneficial to supress pollutant emissions, which can provide reference data for the optimization of clean combustion devices.

抽象的

使用PIV实验和数值模拟研究了非预混撞击火焰的发射特性。进行了不同的顺流条件，以通过火焰-壁相互作用来关注污染物的排放。结果表明，通过实验获得的火焰动力学与通过数值模拟计算得到的动力学动力学具有良好的一致性，并且在大同流速度情况下，近壁区域的火焰不稳定性会增强。另外，同流速度的增加可能会促进一氧化碳的产生，特别是在平均混合物分数较低的区域（0.07-0.26）。CO的分布在大同流速度情况下分散，这与强对流和扩散过程有关。除了，₂混合气流中的浓度和比热容的增加。在高并流含水量的情况下，CO和NO局部排放指标的分布也有所减少，这会削弱CO的产生，热态NO的产生并促进NO的产生，并加速NO的消耗。此外，CO还原主要发生在高CO浓度区域，而在整个流场中却观察不到NO还原。结果表明，较小的同向流速和较高的同向水分含量有利于抑制污染物的排放，可为清洁燃烧装置的优化提供参考数据。