Flash boiling spray has been considered as a promising atomization scheme in improving fuel-air mixture and reduce spray impingement in internal combustion engine applications. Because of its distinctive breakup mechanism, the thermal process of flash boiling spray has not been fully illustrated, in which the fluctuation of flash boiling sprays is not sufficiently studied. This work utilized a high-speed imaging system to implement Schlieren and backlit measurement, with a micro-lens to capture the near-field characteristics and a regular lens for macroscopic studies. A practical two-hole gasoline direction injection fuel injector was used, and the fuel temperature and ambient pressure were varied to generate different superheat indices. Image processing methods were used to find the variation of the center of mass in the spray image to quantify the fluctuation of the spray. Near-field and far-field spray fluctuations were studied systematically for the first time. The results show that near-field fluctuation is enhanced by flash boiling sprays, while far-field fluctuation of flash boiling sprays is suppressed, thus yielding a more stable overall spray cycle-to-cycle variation. The detailed breakup process of flash boiling sprays in the near-field is analyzed. The near-field cone angle and its uncertainty under various boundary conditions are investigated as well. Furthermore, the results have the potential to optimize the problems related to engine stability.

在内燃机应用中，闪蒸沸腾喷雾被认为是改善燃料-空气混合物并减少喷雾冲击的有希望的雾化方案。由于其独特的分解机理，因此尚未充分说明闪蒸喷雾的热过程，在该过程中，尚未充分研究闪蒸喷雾的波动。这项工作利用了高速成像系统来实现Schlieren和背光测量，并配备了微透镜来捕获近场特性和用于宏观研究的常规透镜。使用了实用的两孔汽油方向喷射燃料喷射器，并且改变了燃料温度和环境压力以产生不同的过热指数。使用图像处理方法来发现喷雾图像中质心的变化，以量化喷雾的波动。首次系统地研究了近场和远场喷雾波动。结果表明，闪蒸喷雾提高了近场波动，而闪蒸喷雾的远场波动得到了抑制，从而产生了更稳定的整体喷雾周期变化。分析了近场中闪蒸喷雾的详细分解过程。还研究了在各种边界条件下的近场锥角及其不确定性。此外，结果有可能优化与发动机稳定性有关的问题。结果表明，闪蒸喷雾提高了近场波动，而闪蒸喷雾的远场波动得到了抑制，从而产生了更稳定的整体喷雾周期变化。分析了近场中闪蒸喷雾的详细分解过程。还研究了在各种边界条件下的近场锥角及其不确定性。此外，结果有可能优化与发动机稳定性有关的问题。结果表明，闪蒸喷雾提高了近场波动，而闪蒸喷雾的远场波动得到了抑制，从而产生了更稳定的整体喷雾周期变化。分析了近场中闪蒸喷雾的详细分解过程。还研究了在各种边界条件下的近场锥角及其不确定性。此外，结果有可能优化与发动机稳定性有关的问题。还研究了在各种边界条件下的近场锥角及其不确定性。此外，结果有可能优化与发动机稳定性有关的问题。还研究了在各种边界条件下的近场锥角及其不确定性。此外，结果有可能优化与发动机稳定性有关的问题。