Abstract Flash boiling spray has been extensively investigated because it has the potential in improving spray atomization. However, some phenomena, such as flow rate reduction, exit velocity choke and drastic bubble generation near the exit, etc., cannot be explained by existing theory of subcooled liquid jet and spray atomization. The phase change process occurring inside the nozzle still needs further exploration and investigation. However, due to the small dimensions of the nozzle, it is challenging to measure the flow characteristics experimentally. In this research, a one-dimensional two-phase flow model incorporating modified Stiffened Gas Equation of State is used to simulate the in-nozzle flow characteristics under flash boiling conditions. The model was validated against previous experimental data. The simulation results of the phase change process inside the nozzle was compared qualitatively with experimental data taken from a 2D optical nozzle. Different from subcooled conditions, superheated working liquid inside the nozzle evaporates more drastically as the result of local pressure distribution change. The flow velocity and mass flow rate are affected accordingly as well. In addition, the effects of the injection pressure, ambient pressure, and liquid temperature on these phenomena are also discussed. It was found that the ambient pressure and liquid temperature can affect the bubble generation by altering the evaporation rate of the fuel, while the injection pressure only influence the flow velocity and change the evaporation time of the liquid.

中文翻译：

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闪沸条件下喷嘴内流动特性的数值模拟

摘要 闪蒸喷雾已被广泛研究，因为它具有改善喷雾雾化的潜力。然而，现有的过冷液体射流和喷雾雾化理论无法解释流速降低、出口速度阻塞和出口附近气泡产生剧烈等现象。喷嘴内部发生的相变过程还有待进一步探索和研究。然而，由于喷嘴尺寸小，实验测量流动特性具有挑战性。在这项研究中，一个一维两相流模型结合了修正的强化气体状态方程被用来模拟闪蒸条件下的喷嘴内流动特性。该模型根据之前的实验数据进行了验证。喷嘴内部相变过程的模拟结果与从 2D 光学喷嘴获取的实验数据进行了定性比较。与过冷条件不同，喷嘴内过热的工作液体由于局部压力分布变化而蒸发得更加剧烈。流速和质量流量也相应地受到影响。此外，还讨论了注射压力、环境压力和液体温度对这些现象的影响。研究发现，环境压力和液体温度可以通过改变燃料的蒸发率来影响气泡的产生，而喷射压力只影响流速并改变液体的蒸发时间。