基于CO2稀释的旋流无焰燃烧理论判别方法

基于温度判据和时间判据，本文建立了考虑旋流入口条件和CO₂稀释的无焰燃烧理论判别方法并进行验证，进而讨论了结构参数和操作参数对燃烧模式和火焰稳定性的影响。模型预测的旋流无焰燃烧临界氧浓度与文献中实验数据相比，最大相对误差不超过8%。降低氧浓度、减小当量比或提高入口流量时，温度判据1变化不大，而时间判据更易满足，因此有利于实现无焰燃烧；低旋流数条件下，无焰燃烧稳定性较差。增大燃烧室高度时，温度判据1更易满足，而时间判据更难满足，温度判据1分界线下移更快，有利于形成无焰燃烧；减小燃烧室截面积时，温度判据1变化不大，而时间判据更易满足，有利于实现无焰燃烧；增大燃烧器出口面积时，温度判据1和时间判据均更难满足，且时间判据分界线下移更快，不利于形成无焰燃烧。

Theoretical criterion of swirl flameless combustion based on CO2 dilution

Theoretical identification method of flameless combustion was established and validated considering the swirl inlet and CO₂ dilution based on temperature criterion and time criterion. The effects of structural and operational parameters on the combustion mode and flame stability were discussed. The critical oxygen concentration for swirl flameless combustion had an error within 8% compared to those reported in literature. With decreasing oxygen concentration, reducing equivalence ratio, or increasing flow rate, the temperature criterion barely changed, while the time criterion was easier to be satisfied, which was good for flameless combustion. The flame stability was worse for flameless combustion with a lower swirl number. As the height of combustion chamber increased, the temperature criterion was easier to be satisfied, while the time criterion was more difficult to be satisfied and the boundary corresponding to the temperature criterion moved downwards faster, which was good for flameless combustion. As the intersecting surface of combustion chamber decreased, the temperature criterion changed little, while the time criterion was easier to be satisfied, which was good for flameless combustion. As the outlet surface of combustor increased, both the temperature criterion and time criterion were more difficult to be satisfied, while the boundary corresponding to the time criterion moved downwards faster, which was bad for flameless combustion.