In-situ Diagnostics of Supercritical Flows and Combustions

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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.