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

由于喷雾在各个领域的应用，到目前为止已经进行了无数次的调查。然而，湍流雾化的基本物理原理仍然不为人所知。主要原因是这些现象细微而迅速地观察到其细节，因此很难产生对揭示湍流雾化机理有用的概念。在本研究中，我们提出了一种独特的方法来克服这一困难，利用微重力环境，这是一种新的实验手段，在传统的雾化研究中从未使用过。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，并在室温下以远超过液体临界压力的高压释放到静止的氮气中。由于近临界混合表面射流具有极小的表面张力和高的蒸汽密度，气体的韦伯数为…更重要的是，即使液体射流以低速喷出，射流也可能具有很大的价值。因此，我们可以使用低速、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这两个问题提供了方法论。我们发展了基于微重力实验新发现的理论和数值模型。使传统的雾化理论发生了突破性的变化。特别是，我们发现，由射流解体产生的毛细管波变成了不稳定波，从而导致了随后的解体。我们还可以提出一种构建喷雾燃烧模拟器的策略，该模拟器包括雾化和液滴间火焰传播过程，而所有现有的模拟器都未能包括这些过程。较少

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