Two-dimensional Pyrometry for Measurements of Flame Structure in Energetic Systems

摘要

High-speed pyrometry provides researchers with a tool to optically measure the time-dependent temperature from energetic material flames. However, these measurements typically involve spatially integrating the light emitted from the combustion event, which prevents any spatial resolution within the measurement. The data obtained from these pyrometers also favors high temperatures, creating a bias, which may not always reflect the actual temperature distribution or structure of the flame. There is a need for techniques that can perform a more quantitative analysis of two dimensional flame fronts. In this study, two high-speed framing cameras (HSFC) were used to obtain two-dimensional temperature measurements. A narrow band pass interference filter was placed in front of each camera, one with a center wavelength of 730 nm and one with a center wavelength of 825 nm. The technique was validated by measuring the spatial temperature distribution of a heated nichrome wire before being applied to a reacting energetic system. Post-validation, temperature measurements obtained with the camera technique were used to determine the structure of the flame front as well as flame speed propagating in an aluminum-iron oxide thermite mixture. Details of the pyrometry calibration process are provided in more detail, and flame speed measurements are compared to previous work in the literature.