Quantitative Detection of Combustion Species using Ultra-Violet Diode Lasers

Combustion studies in microgravity are critical to ensuring the safety of personnel onboard space craft as well as for improving our knowledge of combustion phenomena. Under microgravity conditions, flame ignition, propagation and extinction become simplified due to the lack of buoyancy. Quantitative monitoring of combustion species (reactants, products, intermediates) provides rigorous validation of combustion models and yield a better understanding of combustion. Many laboratory-based combustion diagnostics are not suited to use on microgravity platforms due to unique space and power constraints. We propose developing a new UV diode laser-based microgravity combustion diagnostic for quantitative detection of key combustion species. The instrument will allow absolute concentration measurement of key combustion species including trace radicals using a wide variety of microgravity combustion platforms including the Space Station. Our approach uses room temperature UV diode laser output directly, thereby keeping the instrument compact, rugged and energy efficient. The feasibility of the proposed technique will be demonstrated by quantitative measurement of CH radicals in laboratory flames. Further progress in fabrication technology of UV diode lasers for shorter wavelengths and higher power will result in measurement of species in deeper UV.