Combustion and radiation characteristics of the flame of an Al-Li-based alloy composed of many discrete condensed phase particles

Abstract

The use of alloys as the combustible component in infrared decoy formulations enhances their infrared radiation characteristics, resulting in a spectral output that more closely aligns with that of actual protected targets. In this study, formulations for two Al-Li-based and three Mg-Al-based alloys were developed for application in infrared decoys, and their combustion behavior and infrared radiation characteristics were investigated. The results indicate that the mid-to-far infrared radiation intensity ratio for the Al-Li-based alloys ranges from 3.0 to 3.5, whereas that for the Mg-Al-based alloys spans from 4.5 to 5.2. The mechanism responsible for the lower mid-to-far infrared radiation ratio of the Al-Li-based alloys was analyzed using high-speed photography, high-speed infrared imaging, radiometry, and X-ray diffraction (XRD). In contrast to the Mg-Al-based alloys, those based on Al-Li produce combustion products that are primarily high-temperature condensates. Furthermore, Al-Li alloys combust at a lower temperature. The combustion products of the Al-Si-Li alloy, in particular, exhibit characteristic emission in the far-infrared band, thereby significantly enhancing the radiant proportion in this spectral region.