Measurement of inter-scale molecular fluxes in supercritical reacting turbulence

超临界反应湍流中尺度间分子通量的测量

• 批准号: 1923254
• 负责人: Adam Steinberg
• 金额: $ 31.58万
• 依托单位: Georgia Tech Research Corporation
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2019
• 资助国家: 美国
• 起止时间: 2019-09-01 至 2024-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1923254&HistoricalAwards=false
• 关键词: Measurement; inter; scale; molecular; fluxes

Understanding how fluctuations at a specific length scale in a turbulent flow affect the phenomena at other length scales is critical to accurately predict flow properties by numerical simulation. In turbulent combustion, which is the predominant mode of converting chemical energy to thermal energy for transportation and power generation applications, additional challenges arise in comparison to non-reacting turbulent flows because the fluctuating chemical reaction rates occur at very small length scales that typically are not resolved by simulations. This problem is exacerbated by the desire to operate combustion systems at increasingly high pressures, often spanning in to the supercritical pressure conditions. While increasing the pressure has important benefits for efficiency and power density, it also concentrates fluctuations at increasingly small scales and introduces strong variations in thermodynamic properties around the critical point. To better understand this phenomenon, this project will use a novel combination of laser diagnostic and data analysis techniques to measure how fluctuations in molecular nitrogen density move between length scales in premixed flames burning reactants at initially supercritical conditions. Time-resolved measurements of the spatially filtered nitrogen number density and velocity fields will be made in crossed planes using burst-mode spontaneous Raman scattering. The filtering effect of the observation process will be determined and tuned through image deconvolution. Hence, the resultant data will allow explicit determination of the flux of sub-filter fluctuations through the filter scale based on the dynamics of the filtered fields. This information will identify whether traditional modeling paradigms hold for supercritical reacting turbulence and, where necessary, enable the development of more physically accurate models. It also will provide a unique data set against which to benchmark simulations of supercritical turbulent combustion.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.

了解湍流中特定长度尺度上的波动如何影响其他长度尺度的现象对于通过数值模拟准确预测流量特性至关重要。在湍流燃烧中，这是将化学能转化为热能进行运输和发电应用的主要模式，与非反应的湍流相比，出现了其他挑战，因为波动化学反应速率在很小的长度尺度上发生，通常不会通过模拟解决。渴望在越来越高的压力下运行燃烧系统的愿望加剧了这个问题，通常跨越了超临界压力条件。尽管增加压力对效率和功率密度具有重要的好处，但它还集中在越来越小的尺度上的波动，并引入了临界点周围热力学特性的强烈变化。为了更好地理解这种现象，该项目将使用激光诊断和数据分析技术的新型组合来衡量在最初超临界条件下的预混合火焰燃烧反应物中分子氮密度的波动如何在长度尺度之间移动。 使用爆发模式自发的拉曼散射在交叉平面中进行空间过滤的氮数密度和速度场的时间分辨测量。观察过程的过滤效果将通过图像反卷积确定和调整。因此，最终的数据将允许根据过滤场的动力学明确确定子滤波器波动通过滤波器刻度的通量。该信息将确定传统的建模范例是否适用于超临界反应的湍流，并在必要时能够开发更精确的模型。它还将提供一个独特的数据集，以基准对超临界动荡燃烧进行基准模拟。该奖项反映了NSF的法定任务，并认为使用基金会的知识分子优点和更广泛的影响评估标准，认为值得通过评估来获得支持。