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

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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