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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

由于喷雾剂在各个领域的应用，迄今为止已经进行了无数的调查。然而，湍流原子化的基本物理原理仍然被掩盖。主要原因是这些现象是如此的细微和迅速，以至于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，我们提出了一种独特的方法，即利用微重力环境来克服这一困难，这是传统雾化研究中从未使用过的一种新的实验手段。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SF6液体的临界混合状态，在远远超过液体临界压力的高压下，在室温下将其注入静止的氮气中。由于近临界混合表面射流具有极小的表面张力和较高的蒸汽密度，因此即使在低速喷射时，射流的气体韦伯数也可能取较大值。因此，我们可以使用低速、接近临界混合的表面射流来研究湍流雾化过程中的不稳定现象。因此，本实验为同时解决(1)湍流雾化机理和(2)高压射流不稳定特性两个问题提供了方法。我们发展了基于微重力实验新发现的理论和数值模型。并导致传统原子化理论的突破性变化。特别是，我们发现由射流解体产生的毛细波转变为不稳定波，导致随后的解体。我们还可以找到一种策略来构建一个包含雾化过程和液滴间火焰传播过程的喷雾燃烧模拟器，这是所有现有模拟器都无法包含的。少