Combined measurement of velocity and temperature distributions in oil based on the luminescent lifetimes of seeded particles

Abstract

The velocity field and temperature distribution in a fluid flow were measured simultaneously based on luminescence. PIV is useful for velocity measurement, and a measurement method based on the luminescent lifetime is appropriate for detecting the transient temperature field. However, there have been few reports on thermometry in the fluid flow by luminescence, whereas several studies have investigated surface temperature measurement. The europium complex (EuTTA) has been commonly used in temperature-sensitive ‘paints’ for several years and consequently has been examined in several papers. In the present study, particles doped with EuTTA, called temperature-sensitive particles (TSParticles), were prepared. The optical properties of the TSParticles were investigated. A TSParticle was found to be suitable for use with an optical sensor because its lifetime is very sensitive to temperature changes. The lifetime of the TSParticle was approximately 600 µs at 20 °C in water and the intensity was also large enough to be detected by a CCD camera without any image intensifier, at an exposure time of less than 60 µs. It was found that TSParticles could also be used for velocity measurement by means of the PIV technique. The temperature field was measured based on the decay ratio of the TSParticle images, and the velocity distribution in the same plane was also evaluated from these images by PIV. A demonstration was carried out in a thermal stratified silicone oil bath. The velocity and the transient temperature distribution of the oil flow were successfully measured. The spatial resolution of the temperature measurement in the demonstration was 60 µm. The uncertainty of the temperature was 0.35 °C. The spatial resolution and the uncertainty of velocity measurement were 0.6 mm and 20 µm s−1, respectively.