Simultaneous temperature, mixture fraction and velocity imaging in turbulent flows using thermographic phosphor tracer particles

Abstract

This paper presents an optical diagnostic technique based on seeded thermographic phosphor particles, which allows the simultaneous two-dimensional measurement of gas temperature, velocity and mixture fraction in turbulent flows. The particle Mie scattering signal is recorded to determine the velocity using a conventional PIV approach and the phosphorescence emission is detected to determine the tracer temperature using a two-color method. Theoretical models presented in this work show that the temperature of small tracer particles matches the gas temperature. In addition, by seeding phosphorescent particles to one stream and non-luminescent particles to the other stream, the mixture fraction can also be determined using the phosphorescence emission intensity after conditioning for temperature. The experimental technique is described in detail and a suitable phosphor is identified based on spectroscopic investigations. The joint diagnostics are demonstrated by simultaneously measuring temperature, velocity and mixture fraction in a turbulent jet heated up to 700 K. Correlated single shots are presented with a precision of 2 to 5% and an accuracy of 2%.

High-speed planar thermometry and velocimetry using thermographic phosphor particles

“…From repeated measurement sequences, the maximum deviation of the mean measured temperatures to the flow temperature indicated by a thermocouple positioned in the measurement plane was only 5 K. This level of temperature precision is comparable with that achieved in a previous study using a low speed measurement system based on interline transfer CCD cameras and low repetition rate flashlamp pumped solid-state lasers [11]. BAM:Eu saturates at fluences around 2 mJ/cm 2 [11], so the phosphorescence emission intensity is comparable for the two cases as saturation can also be achieved with the high-speed 355 nm laser. The readout noise of CMOS cameras is larger than that of the CCD cameras used in [11].…”

“…BAM:Eu saturates at fluences around 2 mJ/cm 2 [11], so the phosphorescence emission intensity is comparable for the two cases as saturation can also be achieved with the high-speed 355 nm laser. The readout noise of CMOS cameras is larger than that of the CCD cameras used in [11]. However, in this study this potential decrease in signal to noise ratio was compensated for by increasing the phosphorescence collection efficiency.…”

“…When two spectrally filtered images of the particle phosphorescence emission are recorded, the tracer temperature can be determined using a ratio-based method. At low repetition rates, this technique has previously been demonstrated for time-averaged [10] and single shot [11] simultaneous temperature and velocity measurements.…”

“…Since the slip velocity is very low, conduction is the dominant mode of heat transfer between the gas and the particles. Based on a detailed heat transfer model it was previously shown that 2 lm phosphor particles can also accurately trace the gas temperature for most technically relevant flows [11].…”

Characterisation of the luminescence properties of BAM:Eu2+ particles as a tracer for thermographic particle image velocimetry

“…Simultaneously, a UV laser is used to excite the particles, and their temperature-sensitive phosphorescence emission is recorded to determine the particle temperature applying a two-colour intensity ratio method. For micrometre-size particles, it can be shown that the particle temperature and velocity match that of the surrounding gas [1], with both Abstract Thermographic phosphor particles are seeded into the flow as tracers for simultaneous temperature and velocity measurements in fluids. Several studies using different phosphors as gas-phase tracers have been published in recent years.…”