Li Shen, Sanned David, Huang Jianqing, Berrocal Edouard, Cai Weiwei, Aldén Marcus, Richter Mattias, Li Zhongshan
Opt Express. 2021 Oct 11;29(21):34465-34476. doi: 10.1364/OE.434836.
In this work, the combustion behavior of seeded iron particles (d = 70 µm) in a laminar diffusion flame was studied in a modified Mckenna flat-flame burner. Two high speed cameras in stereo configuration allowed 3D position and 3D velocity measurements of burning iron particles as well as 3D evaluation of particle microexplosions. Microexplosive processes are important since it can affect both combustion stability and formation of product components. The observed microexplosions happened before particle extinction resulting in change of trajectories, velocities, radiation intensities and fragmentation into smaller particles. It was observed for the first time that fragments of these microexplosions tend to produce planar structures. A frequent release phenomenon was observed during the iron particle combustion using magnified thermal radiation imaging and high-speed shadowgraphy. This release phenomenon was indirectly confirmed with scanning electron microscopy of combust products, revealing multiple cracked particle shells and hollow structures. Black body radiation characteristics was observed indicating the release being in condensed phase and emission spectroscopy identified FeO as intermediate species during combustion. The observed release is believed to mainly consist of iron-oxide nanoparticles formed in the homogenous reaction between vapor iron and oxidizers.
在这项工作中，在改进的麦肯纳平焰燃烧器中研究了粒径为70微米的籽晶铁颗粒在层流扩散火焰中的燃烧行为。两台立体配置的高速摄像机能够对燃烧的铁颗粒进行三维位置和三维速度测量，并对颗粒微爆炸进行三维评估。微爆炸过程很重要，因为它会影响燃烧稳定性和产物成分的形成。观察到的微爆炸发生在颗粒熄灭之前，导致轨迹、速度、辐射强度发生变化，并破碎成更小的颗粒。首次观察到这些微爆炸的碎片倾向于产生平面结构。在铁颗粒燃烧过程中，通过放大的热辐射成像和高速阴影成像观察到频繁的释放现象。通过对燃烧产物的扫描电子显微镜观察间接证实了这种释放现象，发现了多个破裂的颗粒壳和空心结构。观察到黑体辐射特征，表明释放处于凝聚相，发射光谱确定FeO为燃烧过程中的中间物种。据信，观察到的释放主要由气相铁与氧化剂之间的均相反应形成的氧化铁纳米颗粒组成。
