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Study on the instability of near-critical-mixing surface jet and turbulent atomization for the purpose of high-pressure spray combustion control

用于高压喷雾燃烧控制的近临界混合表面射流和湍流雾化的不稳定性研究

基本信息

批准号：
14350510
负责人：
UMEMURA Akira
金额：
$ 8.51万
依托单位：
Nagoya University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2002
资助国家：
日本
起止时间：
2002 至 2005
项目状态：
已结题

项目摘要

Since spray is used in a variety of fields, a numberless of investigation has been conducted by far. However, the underlying physics of turbulent atomization is still veiled. The main reason is that the phenomena are so fine and rapid to observe its details so that it was very hard to produce those concepts which are useful to reveal the turbulent atomization mechanism. In the present study, we made a unique approach to overcome this difficulty by utilizing the microgravity environment, a new experimental means which has been never used in the conventional style of atomization study. A key point of the experiment is that we realize a liquid jet which has its surface close to a critical mixing state for a SF6 liquid issued into an otherwise quiescent nitrogen gas at a high pressure far exceeding the critical pressure of the liquid and at a room temperature. Since the near-critical-mixing surface jet has a vanishingly small surface tension and a high vapor density, the gas Weber number o … More f the jet may take a large value even when the liquid jet is issued at a low speed. Therefore, we can use a low-speed, near-critical-mixing surface jet to examine the unstable phenomena involved in turbulent atomization processes. Thus, this experiment provides the methodology simultaneously to resolve the two problems of (1) turbulent atomization mechanism and (2) the characteristic properties of the high pressure jet instability.We developed the theories and numerical models which bases the new findings from the microgravity experiments. And lead to a breakthrough change in the conventional atomization theories. In particular, we found that the capillary waves which is generated by the disintegration of the jet turns into unstable waves which leads to the subsequent disintegration. We could also figure out a strategy to construct a spray combustion simulator which includes the processes of atomization and inter-droplet flame propagation which all existing simulator have failed to incorporate. Less

由于喷雾被用于多种领域，迄今为止已经进行了大量的研究。然而，湍流原子化的基本物理原理仍然不为人知。主要原因是这些现象太精细、太快，很难观察到其细节，很难产生那些有助于揭示湍流原子化机制的概念。在本研究中，我们利用微重力环境提出了一种独特的方法来克服这一困难，这是一种在传统原子化研究中从未使用过的新实验手段。实验的一个关键点是，我们实现了一种液体射流，其表面接近临界混合状态，将 SF6 液体在远远超过液体临界压力的高压下和室温下喷入静止的氮气中。由于近临界混合表面射流具有极小的表面张力和高蒸气密度，因此即使当液体射流以低速发出时，射流的气体韦伯数也可能取很大的值。因此，我们可以使用低速、近临界混合表面射流来研究湍流雾化过程中涉及的不稳定现象。因此，该实验提供了同时解决（1）湍流雾化机制和（2）高压射流不稳定性特征两个问题的方法。我们基于微重力实验的新发现开发了理论和数值模型。并导致传统雾化理论发生突破性变化。特别是，我们发现射流崩解产生的毛细波变成不稳定波，导致随后的崩解。我们还可以找出一种构建喷雾燃烧模拟器的策略，其中包括所有现有模拟器都未能包含的雾化和液滴间火焰传播的过程。较少的