Visual observation of fuel-borne ice crystals

This study closely observed fuel-borne ice crystals and discusses their morphological characteristics. Fuel-borne ice crystals are formed naturally in jet fuel when entrained water freezes, and unfortunately, their characteristics are poorly understood. Crystals nucleating in a fluid static condition were observed at about -38 degrees C. The ice crystals had various shapes that can be classified into three types: plate and spherical shapes, columnar shapes, and irregular shapes. The size of the crystals ranged from 5 to 15 microns along the prism plane and up to 30 microns along the base plane. No remarkable growth or phase change was observed after crystallization at low temperature since the number of water molecules in the jet fuel is limited. However, metastable crystals were found in the fuel, as in previous results obtained using a toluene matrix. The metastable crystals could help with the growth of hexagonal fuel-borne ice crystals. Further investigation is required for the growth rate of hexagonal ice crystals from metastable crystals.