CAREER: Compressive Laser Absorption Spectroscopy for Supercritical Combustion Studies

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The next generation of ultra-clean, efficient combustion engines are expected to operate at much higher pressures than today's engines. Unfortunately, combustion physics and chemistry are poorly understood at these high pressures, which has slowed the advancement of cleaner, more fuel-efficient engines (including automotive, diesel, jet, and rocket engines). Therefore, the overarching goal of this project is to better understand combustion at extreme pressures. A new laser diagnostic method is used to investigate fundamental chemistry and radiative properties of combustion at extreme pressures, targeting specific fuels and operating conditions relevant to current and future engine development. Successful completion of the project will yield (1) a novel, broadly-applicable diagnostic tool that will accelerate basic combustion research in a critically important, but largely unexplored high-pressure domain, and (2) new insights into the fundamental chemistry of ignition and pollutant formation at these conditions. Complementary educational activities will leverage modern media technologies to test the integration of laboratory research in the classroom and to engage broader groups outside the university in current scientific and engineering challenges related to energy and combustion.A challenge and research focal point of this project is combustion at supercritical thermodynamic conditions, where the reacting fluid is neither liquid or gas and exhibits non-ideal behavior that is difficult to model. To study non-equilibrium processes in this regime, an experimental method is introduced that adapts advanced theories of signal compression to the wavelength domain in order to conduct laser absorption-based measurements of species and temperature at supercritical pressures. The proposed method can be used to perform broad spectral surveys of the mid- to far-infrared domain or ultra-fast sensing in a narrower wavelength range. Accordingly, this project involves a re-examination of the approaches to fundamental high-temperature spectroscopy studies and in situ species measurements in shock tubes, and enables new exploratory approaches that leverage the strengths of the novel measurement technique. It is envisioned that the compressive sensing method, when synergistically combined with a high-pressure, high repetition-rate shock tube, will (1) extend and/or allow the building of new spectroscopic databases to include extreme pressures, and (2) enable new combustion chemistry studies that isolate high-pressure reaction kinetics in the supercritical regime. A research plan is set forth to test variations of the compressive sensing technique, investigate spectroscopic properties of supercritical fluids, and examine chemical kinetics of high-pressure ignition and soot formation.