Direct-sampling optical techniques for the study of transient combustion events

• Main Author: Herron, John R.
• Other Authors: Peterson, Richard B.
• Language: en_US
• Published: 2013
• Subjects: Combustion; Flame spectroscopy
• Online Access: http://hdl.handle.net/1957/38264

Techniques have been developed for measuring the temperature, stable species concentrations, and atomic radical concentrations during a transient combustion event. They combine the features of direct sampling with two spectroscopic techniques to produce relatively simple diagnostic techniques to obtain time-resolved measurements. In this study, a transient event was provided by a propagating hydrogen/air flame. Stable species were detected downstream of the sampling orifice by electron impact fluorimetry, while temperatures and atomic hydrogen concentrations were measured by atomic resonance absorption spectroscopy. The calculation of stable species concentrations from time-varying fluorescence signals was straightforward, however conversion from absorption measurements to temperatures and atomic radical concentrations required the development of a computer model of the radiation source and the absorption by the sample. The model of the source was validated by comparing predicted and recorded spectra of hydrogen Lyman-α emissions, while the absorption model for the sampled gas was tested by comparing the temperatures predicted by absorption measurements with those recorded at a range of known temperatures. These direct sampling spectroscopic techniques minimize time-history distortions inherent in other direct sampling techniques, and are capable of tracking local temperatures and species concentrations during the passage of a propagating flame front. === Graduation date: 1990