Multispectral coded light for high-speed temperature imaging of aluminum combustion.

Aluminum is a promising carbon-free energy carrier, but advancing its use requires detailed understanding of its combustion behavior at the single-particle level. Measuring the transient surface temperatures of burning aluminum droplets is particularly challenging due to their small size, extreme temperatures, and fast dynamics. In this work, we demonstrate a multispectral pyrometry approach based on a passive frequency recognition algorithm for multiple exposures (FRAME) to achieve quantitative, time-resolved temperature imaging of aluminum droplet combustion. The method employs a single high-speed monochrome camera combined with spectral multiplexing, enabling simultaneous acquisition of multiple well-defined wavelength bands without compromising the native capture rate (50 kHz). By applying a multi-wavelength pyrometry analysis to the spectrally encoded images, we obtain spatially resolved temperature maps in the range of 2000-4000 K. The results reveal the ignition, droplet formation, and flame development stages with high temporal fidelity. The demonstrated technique offers an economical and flexible solution for pyrometry under harsh conditions, and provides insights into aluminum combustion dynamics relevant for its future use as a recyclable, carbon-free fuel.