Investigation of the performance of experimental combustion devices relies heavily on proper diagnostics for characterization of operating regimes and validation of numerical modelling predictions. The primary goal of this work is to develop and implement a measurement system using infrared (IR) spectrum for measurements in combustion environments, capable of making high repetition rate multi-parameter measurements at multiple locations. We use tunable diode laser absorption spectroscopy (TDLAS) in the mid-IR to develop the capability of species and temperature measurements and use this method to characterize a typical flame (Hencken Burner) as well as the exit plane of a model scramjet engine. The measurement targets of primary interest are H2O concentration and flame temperature, although the designed system is also capable of NO, CO2, and CH2O concentration measurements. The design and assembly of the laser system is described in detail, with specific attention given to selection of the proper laser wavelengths for detection of the four abovementioned species. The spectroscopic modeling is described, and a code utilizing known transition parameters is developed to quantify the collected data. Validation results in the Hencken burner demonstrate successful implementation of the measurement technique. Finally, results collected in a scramjet test firing are presented. Experiments using several ethylene fueling strategies were carried out in the scramjet combustor in the Fine Rocket Propulsion Laboratory, and measurements of H2O concentration and temperature were taken at the exit plane. Challenges of the implemented measurement technique and future directions for increased accuracy are addressed.
Development of combustion measurement technique in the infrared spectrum
Investigation of the performance of experimental combustion devices relies heavily on proper diagnostics for characterization of operating regimes and validation of numerical modelling predictions. The primary goal of this work is to develop and implement a measurement system using infrared (IR) spectrum for measurements in combustion environments, capable of making high repetition rate multi-parameter measurements at multiple locations. We use tunable diode laser absorption spectroscopy (TDLAS) in the mid-IR to develop the capability of species and temperature measurements and use this method to characterize a typical flame (Hencken Burner) as well as the exit plane of a model scramjet engine. The measurement targets of primary interest are H2O concentration and flame temperature, although the designed system is also capable of NO, CO2, and CH2O concentration measurements. The design and assembly of the laser system is described in detail, with specific attention given to selection of the proper laser wavelengths for detection of the four abovementioned species. The spectroscopic modeling is described, and a code utilizing known transition parameters is developed to quantify the collected data. Validation results in the Hencken burner demonstrate successful implementation of the measurement technique. Finally, results collected in a scramjet test firing are presented. Experiments using several ethylene fueling strategies were carried out in the scramjet combustor in the Fine Rocket Propulsion Laboratory, and measurements of H2O concentration and temperature were taken at the exit plane. Challenges of the implemented measurement technique and future directions for increased accuracy are addressed.
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