UNS: Heterogeneous Nucleation on Nanoparticles

UNS：纳米颗粒上的异质成核

• 批准号: 1511498
• 负责人: Barbara Wyslouzil
• 金额: $ 35.5万
• 依托单位: Ohio State University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-09-01 至 2020-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1511498&HistoricalAwards=false
• 关键词: UNS; Heterogeneous; Nucleation; Nanoparticles

#1511498Wyslouzil, Barbara E.The streaming vapor trail near an airplane's wing during takeoff or landing illustrates condensation in a high-speed flow initiated by heterogeneous nucleation. The air cools as it passes over the wing, and its relative humidity starts to exceed 100%. This unstable situation drives water condensation on particles forming a cloud. The same phenomenon can play an important role in many other engineering applications including energy extraction from low pressure steam turbines, dehydration and heavy hydrocarbon removal from natural gas, and development of hypersonic wind tunnels. Unfortunately, there are few experimental data to test theories of heterogeneous nucleation at the extreme conditions in these devices. This project will use a supersonic nozzle apparatus to measure rates of heterogeneous nucleation, rates at which particles grow, and the size and structure of the final droplets. All of these are crucial for developing accurate models of heterogeneous condensation in industrial processes.This project explores heterogeneous nucleation under highly non-equilibrium conditions that occur in supersonic flows and investigates the resulting particle growth and structure. Vapor-carrier gas mixtures containing two condensable species will flow through a supersonic nozzle. The seed aerosol will be produced by homogeneous nucleation and growth of the lower vapor pressure condensable under conditions where the higher vapor pressure condensable is subsaturated. As the flow continues to cool, the higher vapor pressure material will become supersaturated and will nucleate on the preexisting aerosol. Static pressure measurements will characterize the flow, spatially resolved small and wide angle X-ray scattering will characterize the aerosol, and infrared spectroscopy will quantify the distribution of the condensable between the vapor, liquid and solid states. A one-dimensional flow model that incorporates heterogeneous nucleation and growth will be tuned to match experimental observations to yield estimates for the heterogeneous nucleation rates.

#1511498#1511498Wyslouzil，Barbara E.飞机起飞或降落时机翼附近的流动蒸汽轨迹说明了由非均质成核引发的高速流动中的凝结。当空气从机翼上方经过时，空气会变冷，相对湿度开始超过100%。这种不稳定的情况促使水在形成云的粒子上凝结。同样的现象可以在许多其他工程应用中发挥重要作用，包括从低压汽轮机中提取能量，从天然气中脱水和脱除重烃，以及开发高超声速风洞。遗憾的是，在这些装置中，几乎没有实验数据来检验极端条件下的非均相成核理论。该项目将使用超音速喷嘴设备来测量非均质成核速度、颗粒生长速度以及最终液滴的大小和结构。所有这些对于开发工业过程中非均相冷凝的准确模型都是至关重要的。本项目探索了在超音速流动中发生的高度非平衡条件下的非均相成核，并研究了由此产生的颗粒生长和结构。含有两种可冷凝物质的蒸汽-载气混合物将通过超音速喷嘴流动。在较高的可凝结的蒸汽压是次饱和的条件下，种子气溶胶将通过低蒸气压可凝聚物的均匀成核和生长而产生。当气流继续冷却时，较高的蒸汽压物质将变得过饱和，并将在先前存在的气溶胶上成核。静态压力测量将表征流动，空间分辨率的小角度和广角X射线散射将表征气溶胶，红外光谱将量化可凝聚物在蒸气、液体和固体之间的分布。一个包含非均相成核和生长的一维流动模型将被调整，以与实验观测结果相匹配，以产生非均相成核速率的估计。