Dynamic characteristics of in-nozzle flash boiling bubbles and corresponding temporal responses of external spray
Dynamic characteristics of in-nozzle flash boiling bubbles and corresponding temporal responses of external spray
复制标题
DOI：
10.1007/s00348-019-2806-2
复制
发表时间：
2019-09
影响因子：
2.4
通讯作者：
Shangze Yang;Zhen-Wei Ma;Shengqi Wu;Xuesong Li;Min Xu
中科院分区：
文献类型：
--
作者：
Shangze Yang;Zhen-Wei Ma;Shengqi Wu;Xuesong Li;Min Xu
闪急沸腾喷雾被认为具有进一步提高实际液体燃料燃烧室效率的潜力。然而，这种瞬态的多相过程的复杂物理尚未完全理解。尽管近喷嘴闪急沸腾喷雾的破碎和雾化性能得到了改善，但其在循环间的变化和波动方面也面临着挑战。本研究旨在探讨喷嘴内闪急沸腾气泡的动态形成、发展与聚集，以建立气泡特性与外部喷雾行为之间的关联。在这项研究中，一个透明的二维喷嘴被用于高速阴影可视化和闪急沸腾喷雾在不同的燃料温度（摄氏度）进行了测量和研究。结合理论分析解释了闪急沸腾气泡的成核和长大过程。近场外部喷雾也被捕获，以揭示在喷嘴闪急沸腾气泡结构的时间响应。结果表明，喷嘴内部的分层结构对喷嘴外喷雾的振荡有直接的影响。快速傅立叶变换（FFT）也被用于量化振荡闪急沸腾喷雾的主频。图形摘要闪急沸腾气泡的增长在喷嘴的轴向方向上被加速。在喷嘴内部可以发现闪急沸腾气泡的波浪状结构。气泡层数随燃油温度的升高而增加。气泡层数越多，外部喷雾脉动越剧烈。
AbstractFlash boiling spray is believed to have the potential in further improving the efficiency of practical liquid fuel combustors. However, the complex physics of this transient, multiphase process are not fully understood. Despite improved spray breakup and atomization performance, near-nozzle flash boiling sprays also faced the challenge in cycle-to-cycle variation and fluctuation. This work aims to explore the dynamic formation, development, and aggregation of in-nozzle flash boiling bubbles to establish the connection between bubble features and external spray behaviors. In this investigation, a transparent two-dimensional nozzle was utilized for high-speed shadowgraph visualization and flash boiling sprays at various fuel temperatures (superheat degrees) were measured and investigated. Theoretical analysis was incorporated to interpret the nucleation and growth of the flash boiling bubbles. Near-field external sprays were also captured to reveal the temporal response with regard to in-nozzle flash boiling bubble structures. Results showed that the layered structure inside the nozzle had a direct impact on the oscillation on the external spray. Fast Fourier transform (FFT) was also adopted in quantifying the dominant frequency of the oscillating flash boiling sprays.Graphic abstractGrowth of flash boiling bubble is accelerated in axial direction of the nozzle. Wavy structure of flash boiling bubbles can be found inside of the nozzle. Number of bubble layers increases with increasing fuel temperature. Fluctuation of external spray is fiercer with greater number of bubble layers.