Liquid Jet Atomization at Supercritical Pressure

先进的燃气轮机发动机和其他先进发动机等新技术涉及在更高压力下喷射液体，这种压力可以达到比大气压力高数百倍的水平。需要新的预测能力来描述液流破碎(雾化)过程中从表面脱落的小液滴的大小、形状和位置。这个项目寻求对物理机制的解释，以及对破碎过程和由此产生的喷雾的控制。研究生和本科生将进行该项目。专题开发将允许加强流体动力学主题的各种研究生课程和未来的第三版教科书。通过现有的UCI少数民族支持计划，首席调查员和他的研究生可以支持项目工作，并就感兴趣的话题进行公开演讲。该项目的目标是为超临界压力下的液流破碎提供令人满意的计算分析，并利用真实气体状态方程和相平衡定律确定重要的混合长度尺度。溶解到液体中的气体的量和新的、显著更高的临界压力将被确定，当两个不同的相存在时。液体和气体都是可压缩的，在高压下密度是可变的。该分析将预测相关的特征时间和规模(例如，扩散时间、频率、最不稳定的波长和增长率)。作为压力和温度、输运性质、表面张力和汽化能的函数的显热能将被确定。三维Navier-Stokes解，通过流体体积或水平集方法跟踪界面，然后进行涡度-动力学分析，将解释在破碎级联中出现的较小结构的顺序。这种方法将描述和解释喷流破碎是在两相还是超临界气体状态下的行为；在这两种情况下，都会出现较小的结构。具有实际意义的雷诺数和韦伯数的雾化将被分析并适当地视为过渡性湍流。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

New technologies such as advanced gas-turbine engines and other advanced engines involve injection of liquids at higher pressures, which can reach levels that are hundreds of times greater than atmospheric pressure. There is a demand for new predictive capabilities to describe the sizes, shapes, and locations of small droplets breaking from the surface during the liquid-stream breakup (atomization) process. This project seeks an explanation of the physical mechanisms and to control of the breakup process and of the resulting spray. Graduate and undergraduate students will conduct the project. Topical development will allow strengthening of various graduate courses in the topic of fluid dynamics and a future third edition of a textbook. Through existing UCI minority support programs, the Principal Investigator and his graduate students can support project work and give public talks on topics of interest. The project goals are to provide a satisfactory computational analysis of the liquid stream breakup at a supercritical pressure and to determine the important mixing length scales with real-gas equations of state and phase-equilibrium laws. The amount of gases dissolving into the liquid and the new, substantially higher critical pressure will be determined, establishing when two distinct phases exist. Both liquids and gases will be compressible and have variable density at high pressures. The analysis will give predictions of relevant characteristic time and scales (e.g., diffusion times, frequencies, most unstable wavelengths, and growth rates). The sensible enthalpy, as a function of pressure and temperature; transport properties; surface tension; and energies of vaporization will be determined. Three-dimensional Navier-Stokes solutions, with interface tracking through volume-of-fluid or level-set methods, followed by ?2 vorticity-dynamics analysis will explain the sequence of smaller structures that appear in the breakup cascade. This approach will describe and explain the behavior whether the jet breakup is in a two-phase or supercritical gaseous state; in either case, the smaller structures appear. Atomization, at the Reynolds and Weber numbers of practical interest, will be analyzed and properly viewed as transitional turbulence.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.