In-situ Diagnostics of Supercritical Flows and Combustions

高压流动动力学和燃烧在重要的工业、交通和航空领域有着广泛的应用。一些根本性的挑战是持续技术进步的障碍，包括对真实流体效应、湍流、各种高压条件下的光学稠密流动和燃烧以及有效的系统集成和分析缺乏了解。由于缺乏对高压流动和燃烧的研究，拟议的项目旨在开发和利用新的诊断工具，并获得高压条件下反应流动和燃烧的基准数据。从实验数据中获得的新见解可用于开发、校准和验证高压条件下的燃烧模型，大大减少了计算工作量。这样的模型可以成为未来推进系统设计的基石。该项目的目标是进行系统的实验，借助新的高空间和时间分辨率成像技术，在从大气压到亚临界/跨临界/超临界条件的流动之间建立一座桥梁。具体地说，将使用中子和2D光学(拉曼)成像技术，并结合可变压力燃烧室。总体而言，该项目旨在获得喷嘴几何形状、内部(喷嘴内)流动、近场稠密流动以及反应流至超临界压力时的气相特性的全面表征。此外，拟议的工作将获得(I)通过2D拉曼定量测量局部燃料/空气浓度，(Ii)通过2D拉曼信号的光流分析来定量测量流动速度，以及(Iii)通过斯托克斯和反斯托克斯拉曼光谱的比率来测量局部温度。从拟议的实验和未来的建模工作中获得的新理解将导致下一代推进系统性能的改进。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。

High-pressure flow dynamics and combustion have many applications in major industrial, transportation, and aviation sectors. A number of fundamental challenges stand as barriers to continued technical progress, including lack of understanding of real-fluid effects, turbulence, optical dense flow and combustion under various high-pressure conditions, and efficient system integration and analysis. Motivated by the lack of high-pressure flow and combustion research, the proposed project aims to develop and utilize novel diagnostic tools and to obtain benchmark data of the reactive flow and combustions at elevated pressure condition. The new insights gained from experimental data can be used to develop, calibrate, and validate combustion models at high-pressure conditions, with significant reduction in computation effort. Such models can be building blocks for designs of future propulsion systems. The goal of this project is to conduct systematic experiments to build a bridge between flows from atmospheric pressure to subcritical/transcritical/supercritical conditions with the help of novel high-spatial and -temporal resolution imaging techniques. Specifically, neutron and 2D optical (Raman) imaging techniques will be used, coupled with a variable-pressure combustion chamber. Overall, the project aims to obtain comprehensive characterization of the nozzle geometry, internal (in-nozzle) flow, near-field dense flows, and gas-phase properties in reacting flows up to supercritical pressures. Additionally, the proposed work will obtain (i) quantitative measurements of local fuel/air concentrations by 2D Raman, (ii) flow velocities by optical flow analysis of 2D Raman signal, and (iii) local temperature by ratios of Stokes and anti-Stokes Raman spectroscopy. The new understanding gained from proposed experiments and future modeling efforts will lead to improvement in performance of next generation propulsion systems.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.