The mechanisms of transient formation and oxidation of soot in an aero-engine model combustor at elevated pressure are studied for the first time using a combination of high-speed simultaneous stereo-PIV and OH-PLIF and results from a recent detailed LES. A combined analysis of experiment and LES shows that the highly transient and intermittent evolution of soot in this combustor is governed by an unsteady interplay of distinct pockets of burned gas in the inner recirculation zone (IRZ) with either relatively rich or relatively lean composition. The former originate from reaction of fuel-rich unburned gas, whereas the latter result from additional admixture of secondary air further downstream. The analysis further enables distinction and localization of premixed and diffusion-type flame fronts within the flame zone. The time-resolved complementary measurements of velocity field and flame structure allow accurate tracking of both the burned gas pockets and soot filaments. It is seen that soot generally forms in the rich pockets if their residence time in the IRZ is sufficient, whereas oxidation occurs in the lean zones carrying OH. Correlating the dynamics of flow field and soot indicates that the intermittency of soot is driven by an intermittent flow of lean burned gas into the IRZ that affects the residence time of rich pockets. The results suggest that the formation of soot might be further reduced by a proper adjustment of secondary air injection aiming at a sufficient and more constant recirculation of lean burned gas. A remarkably good agreement of measured and simulated instantaneous flame structures is observed, indicating that flow field and gas-phase reactions are well predicted by the LES. The experimental insights into the transient mechanisms of soot formation and oxidation, on the other hand, may provide useful input for LES soot models where deviations from measurements are generally larger.

首次结合高速同步立体PIV和OH-PLIF研究了航空发动机模型燃烧器中烟灰在高压下的瞬态形成和氧化机理，并根据最近的详细LES结果进行了研究。对实验和LES的综合分析表明，该燃烧器中烟尘的高度瞬态和间歇性演变受内部再循环区（IRZ）中具有相对浓或相对稀的成分的不同燃烧气袋不稳定的相互作用所控制。前者源自富含燃料的未燃烧气体的反应，而后者源自二次空气在更下游的额外混合。该分析还使得能够在火焰区域内区分和定位预混合型和扩散型火焰锋。时间分辨的速度场和火焰结构的补充测量值可精确跟踪燃烧的气穴和烟ot丝。可以看出，如果烟灰在IRZ中的停留时间足够长，则通常会在富烟气中形成烟灰，而在带OH的贫油区发生氧化。将流场和煤烟的动力学相关联表明，煤烟的间歇性是由稀薄的燃烧气体间歇性流入IRZ驱动的，这会影响富煤袋的停留时间。结果表明，通过适当调节二次空气喷射以进一步实现稀薄燃烧气体的充分和更稳定的再循环，可以进一步减少烟灰的形成。观察到的瞬时火焰结构与实测结果非常吻合，表明LES很好地预测了流场和气相反应。另一方面，对烟灰形成和氧化的瞬态机制的实验研究可能为LES烟灰模型提供有用的输入，其中与测量值的偏差通常较大。