Combustion

Research Focus: We develop and apply advanced laser diagnostics to measure concentrations of chemical intermediates and temperatures, to address specific issues of combustion efficiency, pollutant formation, and flame structure. Diagnostics development research focuses on laser induced fluorescence (LIF) methods and includes basic spectroscopy studies to characterize and locate favorable excitation and detection wavelengths, as well as collisional quenching and energy transfer experiments needed to quantify flame measurements. Other pioneering work includes two photon excitation methods, amplified spontaneous emission, cavity ringdown absorption spectroscopy, and imaging and multiple species methodologies.

The diagnostics are then applied to study specific problems, using an appropriate laboratory-scale combustion system: various atmospheric pressure burners, a low pressure premixed laminar flame featuring excellent spatial resolution and modelability, and a high temperature arc-jet facility.

Accomplishments: We have developed new LIF flame diagnostics methods for CH, HCO, formaldehyde, and Mn atoms. From spectroscopic studies, a versatile simulation program was produced for spectral modeling of key species (link to LIFBase). Quenching recommendations were compiled for quantifying flame LIF concentration determinations. Low pressure flame studies have established values for prompt NO production and NO reduction by reburn in methane flames and confirmed a new hydrogen-based route to NO formation in combustion. Such experiments serve as targets in chemical kinetics mechanism development (link GRI-Mech, process modeling). Effects of a manganese fuel additive on flame chemistry were also studies by a series of LIF observations. Careful spatially resolved LIF measurements of CH, temperature, OH, and CH2O in Bunsen flames provide the flame structure knowledge and pollutant precursor information needed to guide understanding modeling of these appliance burner systems, including the effects of physical inserts.

A plasma arc-jet is a related high-temperature hostile environment to combustion, in this case with diamond synthesis as a goal. We used LIF measurements to characterize this process chemically and physically and provide diagnostics markers for process control.

Application Opportunities: We are currently using our diagnostics to interpret chemiluminescent emissions chemically, so these easier observations may be used quantitatively in combustion control, space experiments, and process monitoring. Our multifaceted approach, including modeling efforts, can be applied to problems ranging from pollution and efficiency for larger or alternative fuels, effects of additives, high temperature materials synthesis, and pollutant emissions reduction strategies. Because LIF is selective, remote, and sensitive to measuring trace intermediates, our methods are ideal for addressing or diagnosing combustion chemistry or other high temperature problems and processes.
 

Visit the Laboratory - Molecular Physics Laboratory

Technical Contact:
Gregory P. Smith
(650) 859-3496
gregory.smith@sri.com