Investigation of rapid evaporation in a nozzle

提出的研究是一个实验计划，以评估快速蒸发作为一种手段，以改善雾化燃料喷雾。这项工作将描述纯液体和有添加剂的液体中的成核过程。目前有许多相互竞争的模型来解释闪光喷雾、沸腾液体蒸发蒸汽爆炸、蒸汽爆炸和其他爆炸性沸腾事件中发生的快速相变。然而，控制这些事件的潜在过程仍然知之甚少。所提出的实验使用透明玻璃喷嘴，结合现有的喷雾装置，创建一个简单的流动系统，控制膨胀。液体将从喷嘴上游被加热。当流体通过喷嘴膨胀时，它会变得热力学不稳定，发生快速沸腾，并形成一个固定的蒸发波阵面。拍摄了波前的照片。在项目的第二阶段，端口将被熔合到喷嘴上，以容纳压力传感器和热电偶。这些仪器将用于获取有关波的热力学信息。该系统的数据可用于与现有模型的预测进行比较。沸腾过程被认为与常见的核沸腾行为有很大不同，也可以仔细观察到。这项工作将在三个方面产生影响。首先，它将显著促进我们对蒸发波行为的理解。其次，它将提出控制闪光的技术，用于有用的目的，如燃油喷射，制造或涂层工艺。第三，它将导致控制或减轻意外蒸汽爆炸的策略。总的来说，这项研究的结果将构成一个实质性的数据集，可用于快速蒸发模型的基准。波前的观测将澄清传播机制，热力学数据将有助于解释这些爆炸事件的能量输出。这些综合资料将对该领域作出重大贡献。

The proposed research is an experimental program to assess rapid evaporation as a means for improving atomization of fuel sprays. The work will characterize nucleation processes in pure liquids and liquids with additives.  Presently there are a number of competing models to explain the rapid phase change witnessed in flashing sprays, BLEVE's (Boiling Liquid Evaporating Vapour Explosions), steam explosions, and other explosive boiling events.  However, the underlying processes that control these events are still poorly understood.      The proposed experiment uses a transparent glass nozzle, in conjunction with an existing spray apparatus, to create a simple flow system with a controlled expansion.  The liquid will be heated upstream from the nozzle.  As the fluid expands through the nozzle it can become thermodynamically unstable, rapid boiling occurs, and a standing evaporation wave front can form.  Photographs are taken of the wave front.  In the second phase of the project ports will be fused onto the nozzle to accommodate pressure transducers and thermocouples.  These instruments will be used to acquire thermodynamic information about the wave.  The data from this system can be used to compare to the predictions from existing models.  The boiling process, which is thought to be quite different from common nucleate boiling behaviour, can also be carefully observed.      This work will have impact in three areas.  First, it will significantly advance our understanding of evaporation wave behaviour.  Second, it will suggest techniques for the control of flashing for useful purposes such as fuel injection, manufacturing, or coating processes.  And third, it will lead to strategies for controlling or mitigating accidental vapour explosions.  Overall, the results from this study will constitute a substantial data set that can be used to benchmark models of rapid evaporation.  The observations of the wave front will clarify the propagation mechanism, and the thermodynamic data will help to explain the energy output of these explosive events.  The combined information will make a significant contribution to the field.