Flame-vortex interactions are critical to the understanding of turbulent reacting flows. The impact of exothermicity on reacting vortex rings is investigated both numerically and experimentally to assess the dominant effect of heat release. Experimental observations of ring trajectories show an initial increase in ring speed in the early stage, followed by a large reduction in speed. It is found numerically that dilatation due to combustion heat release is the dominant effect over enhanced diffusivities in a reacting vortex ring. Increasing fuel volume in the ring beyond a critical limit, obtained from a simple model, actually decreases the amount of heat release during the early stage of the interaction. In addition, the increase in ring circulation led to a decrease in ring speed in the early stage of formation. Nitrogen dilution of the propane fuel reduces the flame luminosity and burnout time, as well as changes in details of the formation and dissipation of the luminous cap, with little change in the primary structure or dynamics of the interaction. The numerical simulations were successful in explaining most of the experimental observations, however, differences in flame structure and ring dynamics attributed to radiative heat loss were inconclusive when radiative heat loss was modeled as an overall decrease in flame temperature.
A sensor for carbon monoxide detection based on broadband absorption spectroscopy with a gas correlation filter is developed using a miniaturized light source and detector without the need of a mechanical chopper to alternate between two gas correlation cells into the optical path. Measurements were conducted using calibrated CO/N 2 mixtures and sampled combustion products from a diffusion flame. The detection sensitivity was found to be 100 ppm for the measured range of 100 to 500 ppm. The sensor can be used to control individual burners in small scale combustion systems in order to maintain combustion efficiency and minimize pollutant emissions during their operation life cycle.
The demonstration of an in-flight Tunable Diode Laser Absorption Spectroscopy (TDLAS) system for the measurement of mass capture is being developed in the Hypersonic International Flight Research Experimentation (HIFiRE) Flight 1 (see Kimmel et al AIAA 2007-534 for full description). The key to integration into a flight payload is to make a system that will both fit into the flight system meaning weight, size and power requirements as well as being able to survive in the much harsher flight environment as compared to the laboratory. This document contains the design consideration and overview of the system as it progressed from bench type hardware to being a fully integrated flight payload.
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