Our research is driven by applications in propulsion and energy, with extensions to health and environment. Lab activities are united by a core focus in experimental thermofluids and applied spectroscopy. Projects commonly span fundamental spectroscopy science to the design and deployment of prototype sensors to investigate dynamic flow-fields.
High-speed chemical propulsion systems represent a uniquely challenging engineering system to design and model due to the complex combination of competing fundamental mechanisms of heat transfer, chemical kinetics, and fluid mechanics. Due to the high cost, and higher cost of failure, associated with space travel, propulsion systems must be engineered to operate near physical limits with a precision driven by intolerance for error. Many advanced propulsion technologies are hindered in their development by a lack of understanding and control to minimize risk of failure at performance limits. These constraints drive the need for advanced diagnostic capability for time-resolved, in-situ characterization of propulsion flows to accelerate technology development. Optical sensors uniquely solve this challenge.
Laser absorption spectroscopy can be used to measure temperature, species, pressure, and velocity in harsh, high-temperature flows that typify propulsion systems. Integration of this sensing method enables quantitative determination of performance (e.g. combustion efficiency, enthalpy flux) and the identification of high-speed events / anomolous factors (e.g. combustion instability). Such sensors further enable the investigation of alternative fuels and operating conditions (T,P) and the corresponding effects on performance and reliability. Example applications from recent research efforts include time-resolved sensing behind detonation waves and in-situ mapping of a supersonic combustor for hypersonic flight.
Chemical bond energy (in the form of solid, liquid, and gaseous fuels) accounts for more than 80% of the world's energy resource demand. Due to the high density (on both mass and volume basis) of energy stored in chemical bonds, fuels will remain carriers of energy for efficient transport and many on-board end-uses long after fossilized sources have been exhausted as a result of poor economics or regulatory constraints. Bio-fuels and cleaner synthetic fuels must be efficiently processed and integrated into existing and new energy conversion systems. These conversion processes (spanning from artificial photosynthesis to flex-fuel engines) uniformly involve reacting flows with transient species and thermodynamic properties.
Laser diagnostics provide a non-intrusive means to investigate and optimize these energy conversion processes with potential for in-situ analysis and real-time control. In recent works, advanced multi-species sensor systems were used to investigate pollutant formation and biofuel combustion at the fundamental level (laboratory chemical kinetics studies) and as applied to real-world power-generation systems (flex-fuel gas turbines). A complimentary application is in tracking the propogation of pollutant formation from anthropogenic sources to and between environmental sinks.
From a thermo-fluid engineering perspective, the human body can be depicted as a low-temperature engine with a complex inner-network of reacting flows. Like most engines, carbon-based fuel (i.e. food) and oxygen (air) are intakes, while carbon dioxide and water are the primary exhaust products. The trace composition of exhaled breath provides a window into the body's internal biochemistry, with much of the information in blood transferred across the alveolar barrier (lungs) to the breath. As such, matabolic dysfunction and disease states yield gaseous biomarkers, which can be detected by various methods ranging from mass-spectroscopy to trained animals. Breath analysis provides clear advantages to blood diagnostics due to inherent non-invasiveness and continuous monitoring potential, and yet has found little clinical traction, attributable in part to insufficient or impractical instrumentation.
Laser absorption spectroscopy, particulary in the mid-infrared, provides a means for rapid-response, point-of-care clinical breath analysis of numerous volatile biomarkers. By leveraging sensing techniques developed for high time-resolution measurements in harsh propulsion flows, novel calibration-free on-line breath diagnostics can be utilized for clinical and translational research, with particular suitability to emergent conditions that require time-senstivie information.