A novel technique for quantitative temperature mapping in liquid by measuring the lifetime of laser induced phosphorescence

Abs ract : A unique method is described in the present paper for quantitative mapping of temperature field in a liquid flow by taking advantage of the phosphorescence lifetime dependence on temperature. This methodology represents an extension of the Molecular Tagging Velocimetry (MTV) technique. As in MTV measurements, the phosphorescence signal is imaged at two successive times within the lifetime of the tracer. The phosphorescence lifetime, estimated from the intensity ratio of the two images at each point, is calibrated with respect to the temperature. This procedure eliminates the effects of the variation of the incident illumination. The method described in the present paper also allows the simultaneous quantification of velocity and temperature fields in a fluid flow by using the same phosphorescent tracer (1-BrNp⋅Gβ-CD⋅ROH) and the same optical and equipment setup. While the displacements of the tagged regions between two interrogations provide the estimate of fluid velocity vectors, the intensity ratio of the two images represents the fluid temperature distribution. The implementation and application of the new technique are demonstrated by conducting simultaneous temperature and velocity measurements in a pulsed cold jet discharging into hot ambient fluid. t