Matthew M. Biss

High-speed digital color imaging pyrometry

Temperature measurements of high-explosive and combustion processes are difficult to obtain due to the speed and environment of the events. To overcome these challenges, we have characterized and calibrated a digital high-speed color camera that may be used to measure the temperature of such events. A two-color ratio method is used to calculate a temperature using the color filter array raw image data and a graybody assumption. If the raw image data are not available, temperatures may be calculated from the processed images or movies, depending on proper analysis of the digital color imaging pipeline. We analyze three transformations within the pipeline (demosaicing, white balance, and gamma correction) to determine their effect on the calculated temperature. Using this technique with a Phantom color camera, we have measured the temperature of exploded C-4 charges. The surface temperature of the resulting fireball was found to rapidly increase after detonation, and subsequently decayed to a constant value of approximately 1980 u2009K.

High-speed two-camera imaging pyrometer for mapping fireball temperatures

A high-speed imaging pyrometer was developed to investigate the behavior of flames and explosive events. The instrument consists of two monochrome high-speed Phantom v7.3 m cameras made by Vision Research Inc. arranged so that one lens assembly collects light for both cameras. The cameras are filtered at 700 or 900 nm with a 10 nm bandpass. The high irradiance produced by blackbody emission combined with variable shutter time and f-stop produces properly exposed images. The wavelengths were chosen with the expected temperatures in mind, and also to avoid any molecular or atomic gas phase emission. Temperatures measured using this pyrometer of exploded TNT charges are presented.

Thermal imaging of nickel-aluminum and aluminum-polytetrafluoroethylene impact initiated combustion

Combustion temperatures from impact initiated nickel-aluminum (NiAl) and aluminum-polytetrafluoroethylene (Al-PTFE) materials have been measured using a high-speed two-camera imaging pyrometer. The materials were launched with a nominal velocity of 1700u2009m/s into a sealed chamber. Upon impact into a steel anvil chemical reactions were initiated and a flame propagated through the chamber. The measured temperature after impact was 3600u2009K (NiAl) and 3300u2009K (Al-PTFE).

Near field optical characterization of explosions

Techniques and instrumentation allow for simultaneous, real-time mapping of temperature, pressure, chemical species and energy deposition during and following explosions. This work provides quantitative, simultaneous measurement in the explosive near and far-field (0-500 charge diameters) of surface temperatures, peak air-shock pressures, chemical species signatures and shock energy deposition that characterize explosions.