Dynamic behavior and mechanism analysis of tip wetting process under flash boiling conditions
Dynamic behavior and mechanism analysis of tip wetting process under flash boiling conditions
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闪蒸条件下尖端润湿过程的动态行为及机理分析
DOI：
10.1016/j.fuel.2021.121773
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发表时间：
2022
期刊：
影响因子：
7.4
通讯作者：
Min Xu
中科院分区：
文献类型：
--
作者：
Di Xiao;Shuyi Qiu;Xuan Zhang;Yijia Zhang;Xuesong Li;David Hung;Min Xu
日益严格的排放法规要求最先进的内燃机在运行时产生最少的颗粒物。闪速沸腾喷雾具有改善气缸内燃料-空气混合过程和消除喷壁撞击等优点，被认为是实现高效燃烧的一种有潜力的技术。另一方面，认为闪蒸也会增强喷射器尖端的润湿现象，因为扩大的喷雾羽流会更频繁地与预孔相互作用，导致尖端烟尘和沉积。然而，在现有文献中，对尖端润湿膜形成、传播和蒸发的相关物理认识仍然缺乏。以一种双孔汽油直喷（GDI）喷油器为研究对象，采用光学方法分析了其尖端润湿特性。利用高速成像技术在近场显示薄膜的动力学特性，利用激光诱导荧光技术捕捉到尖端薄膜清晰的足迹。研究了不同的边界条件，如燃料温度、环境压力和喷射时间对尖端润湿过程的影响。研究发现，射流射流的尖端润湿过程可分为宽羽状诱导润湿和滴状诱导润湿两个阶段，其中燃料滴状是导致尖端润湿的主要原因。此外，闪蒸喷雾对喷嘴润湿的影响可以从两个方面进行分析。增强的宽羽流效应和翅片滴度将显著增加燃料在尖端的沉积，而强蒸发特性有助于消除闪蒸雾化对尖端的负面润湿影响。
The increasingly stringent emission regulations have required that the State-of-the-art internal combustion engines operated with minimum particulate matters produced. Flash boiling spray is considered to be potential technology for achieving high efficiency combustion, with its benefit of improving fuel-air mixing process in cylinders and eliminating spray-wall impingement. On the other side, it is believed that flash boiling would also enhance the injector tip wetting phenomenon since the widened spray plume would interact with the pre-hole more frequently, causing tip sooting and deposits. However, understanding of the physics related to the tip wetting film formation, propagation and evaporation is still lacking in the existing literature. This investigation focused on a two-hole gasoline direct injection (GDI) fuel injector, and its tip wetting characteristics were analyzed with optical means. High-speed imaging was used to illustrate the film dymanics in the near field, and laser-induced fluorescence was used to capture clear footprints of the tip film. Various boundary conditions, such as the fuel temperature, ambient pressure, and injection durations were investigated to figure out their impacts on the tip wetting process. It was found that the tip wetting process could be divided into two stages, namely wide plume induced wetting and dribble induced wetting, among which the fuel dribble was the primary cause of tip wetting. Besides, the impact of flash boiling spray on tip wetting could be analyze in two aspects. The enhanced wide plume effect and finner dribble would significantly increase the fuel deposited onto the tip, while the strong evaporating nature can help eliminate negative tip wetting effects from flash boiling atomization.
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