CAREER: Bottom-Up Understanding of Liquid Breakup at Supercritical Conditions

职业：对超临界条件下液体分解的自下而上的理解

基本信息

批准号：
2237124
负责人：
Dorrin Jarrahbashi
金额：
$ 50.31万
依托单位：
Texas A&M Engineering Experiment Station
依托单位国家：
美国
项目类别：
Continuing Grant
财政年份：
2022
资助国家：
美国
起止时间：
2022-12-15 至 2027-11-30
项目状态：
未结题

来源：
https://www.nsf.gov/awardsearch/showAward?AWD_ID=2237124&HistoricalAwards=false
关键词：
CAREER Bottom Up Understanding Liquid

项目摘要

The design of modern liquid-fueled engines is shifting toward higher pressures exceeding the fuel critical point (supercritical) to improve fuel-air mixing, enhance combustion efficiency, and reduce engine emissions. Liquid fuel injection generally entails liquid jet breakup into droplets, forming a spray. At supercritical conditions, however, spray formation transitions into a gas-like mixing behavior. The underlying mechanism of this transition, i.e., trans-critical breakup is elusive. Trans-critical breakup is linked to dramatic changes in fluid properties and reduced surface tension due to weakened intermolecular forces. However, the effect of molecular-level interactions on the breakup of microscopic droplets is not understood. This grant supports fundamental research to elucidate the mechanisms underlying liquid breakup at supercritical conditions from molecular interactions to higher scales to advance supercritical combustion. The results will enable new predictive capabilities in controlling supercritical mixing before combustion over multiple scales. This knowledge will promote the next generation of high-speed liquid-fueled propulsion systems for supersonic/hypersonic air and space transportation and supercritical power generation cycles. These benefits will promote U.S. clean energy initiatives and strengthen national security, defense, and economic competitiveness. The educational activities will cultivate an inclusive learning environment in multiphase flows and foster sustained mentorship for under-represented minorities and women to diversify the pipeline of future STEM leaders. Training teachers and informing students and parents at school’s STEM events will enhance public literacy on fluid mixing to promote clean combustion.This project intends to fundamentally understand the breakup of an isolated liquid droplet at supercritical conditions in both low-speed and shock-laden flows where shockwave interaction with droplets promotes breakup. The trans-critical shock-driven breakup mechanism is not known, as experimental diagnostics are not adequate for such extreme conditions, and models are decoupled from the molecular interfacial behavior that dictates droplet breakup. This project will address these knowledge gaps and generates new knowledge on the relationship between surface tension and phase change at supercritical conditions and its effect on droplet breakup. Three research objectives will be to (1) Identify the molecular interfacial behavior of a trans-critical droplet from molecular- to microscale; (2) Understand the breakup mechanisms of a trans-critical droplet in low-speed crossflow, and (3) Determine the shock-driven breakup mechanisms of a trans-critical droplet. The technical approach involves a bottom-up approach based on first principles involving coupled Molecular Dynamics-Direct Numerical Simulations and high-speed experimental measurements. The generated knowledge is critical for controlling fuel-air mixing in high-pressure liquid injection systems in diesel, rocket, gas turbine, scramjet, and rotating detonation engines.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.

现代液体燃料发动机的设计正在转向超过燃料临界点（超临界）的更高压力，以改善燃油-空气混合、提高燃烧效率并减少发动机排放。液体燃料喷射通常需要将液体射流分解成液滴，形成液滴。然而，在超临界条件下，喷雾形成转变为类似气体的混合行为，即跨临界破碎与流体性质的急剧变化和表面减少有关。由于紧张然而，分子级相互作用对微观液滴破裂的影响尚不清楚，这项资助支持阐明超临界条件下液体破裂的机制，从分子相互作用到更高尺度，以促进超临界燃烧。研究结果将为控制多尺度燃烧前的超临界混合提供新的预测能力，这些知识将促进下一代超音速/高超音速航空航天运输和超临界动力的高速液体燃料推进系统。这些好处将促进美国的清洁能源计划，并加强国家安全、国防和经济竞争力。这些教育活动将在多阶段流动中营造包容性的学习环境，并促进对代表性不足的少数族裔和妇女的持续指导，以使能源管道多样化。培训教师并在学校的 STEM 活动中向学生和家长提供信息，将提高公众对流体混合的认识，以促进清洁燃烧。该项目旨在从根本上了解低速和超临界条件下孤立液滴的破裂。冲击波与液滴相互作用促进破碎的冲击流，跨临界冲击驱动的破碎机制尚不清楚，因为实验诊断不足以应对这种极端条件，并且模型与决定液滴破碎的分子界面行为脱钩。该项目将解决这些知识空白，并产生关于超临界条件下表面张力和相变之间的关系及其对液滴破裂的影响的新知识，其中三个研究目标是（1）确定分子界面行为。从分子尺度到微观尺度的跨临界液滴；（2）了解低速横流中跨临界液滴的破碎机制；（3）确定冲击驱动的跨临界液滴的破碎机制。涉及基于耦合分子动力学直接数值模拟和高速实验测量的第一原理的自下而上方法，所生成的知识对于控制柴油、火箭、天然气高压液体喷射系统中的燃料-空气混合至关重要。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。