Dual-luminescence imaging for capturing time-resolved temperature distributions of two-phase flow

A dual-luminescence imaging method introduced in this paper captures time-resolved temperature distributions with unsteady flow structures for understanding two-phase flow phenomena. The method is featured as a time-resolved and non-intrusive measurement with high spatial and time resolutions. The spatial and time resolutions are mainly limited by the signal level from an optical setup of an imaging device. The absolute spatial and time resolutions can be limited by the size of the probe molecule and the thermal quenching process. The former is on the order of sub-nanometers and the latter is on the order of 10−12 to 10−8 s, respectively. The imaging system consists of two luminescent probes, color high-speed camera, and an illumination source. The illumination source can be a point, sheet, or volume illumination to locate the temperature measurement region of interest. The luminescent images from the two luminescent probes are simultaneously acquired by a color high-speed camera. By a ratio of the two-color images at each measurement-time frame, time-resolved temperature-dependent images can be captured. Time-resolved temperature distributions of supercooled-water droplet are shown as a demonstration of the dual-luminescent imaging method. A supercooled condition release is time-resolved with 1000 Hz image frame.