Determining water content in a liquid fuel by the luminosity of its droplet

[Display omitted] •This research determines typical luminosities of fuel droplets being heated.•One can assess the conformity of a fuel to the specified grade without fluorophore.•Luminosity of fuels may differ from that of water by more than three times.•The lower the temperature, the greater the differences in fuel and water luminosity.•The proposed approach can be used for analysis of water content in composite fuels. In this research, an effective way to identify the grade of a typical liquid fuel or combustible liquid judging by the luminous intensity of a single droplet is offered. This method is based on comparing the luminosity of droplets under study illuminated by an impulse laser against reference values. The experiments feature droplets of typical fuels, a combustible liquid, and water at different heated air temperatures ranging from 20 to 500 °C. Water is used due to its popularity as an environmentally friendly additive to high-potential fuels. The experiments involved a non-contact optical diagnostic technique of Planar Laser Induced Fluorescence and two fluorophore types (Rhodamine 6G and Rhodamine B). The luminosity ranges of droplets of fuel-water compositions were experimentally determined for the first time. A number of approximations were obtained for typical combustible liquids, which make it possible to determine the percentage of water in a fuel.