部分预混旋流燃烧的大涡模拟

采用耦合涡耗散概念模型的大涡模拟方法,探究了Re和组分变化对部分预混旋流火焰动力学特性的影响。通过与实验结果定性和定量的比较,验证了大涡程序模拟燃烧过程的可靠性。计算结果显示Re的增加,会明显提高空-燃混合效率,从而导致部分预混火焰中预混燃烧模式的比例有所增加,且预混燃烧区域向上游移动,Re的增加也会使得火焰下游产生更多更快的涡破碎结构。N_2含量的增加,会减小流向回流区尺寸,降低空-燃混合效率,但对减小火焰温度具有明显效果,从而对降低NO_x排放产生积极作用。结论为进一步研究部分预混旋流燃烧室的不稳定性及燃烧效率提供了理论和方法上的指导。

Large-eddy simulation of partially-premixed swirling combustion

The partially-premixed swirling combustion dynamics were studied by large-eddy simulation (LES) method based on eddy dissipation concept model. The influences of Reynolds number and nitrogen dilution on combustion dynamics were carefully analyzed. The reliability of the LES program was validated through comparison with experiments. Good correlation was obtained. The larger Reynolds number leads to better mixing between fuel and air, which facilitates the appearance of larger proportion of premixed combustion regime during the partially premixed operating condition. The premixed flame moves upstream with increased Reynolds number and more vortex breakdown appears downstream. The recirculation zone and flame temperature dramatically decrease with increased nitrogen content, which is significant for the reduction of NOX emissions. The obtained conclusions could be significant to the further study of combustion instability and economical efficiency in partially-premixed combustor.