Simultaneous measurement of velocity and temperature field of high temperature jet using thermographic phosphor particles

In order to overcome existing complicated and costly simultaneous measurement system, an inexpensive and simple measurement system was suggested to measure the temperature field and velocity field at high temperature. The manganese-activated magnesium fluorogermanate (Mg4FGe6:Mn, MFG) which is one of thermographic phosphor with luminescence characteristic of excitation at 385 nm wavelength and emission 660 nm wavelength light was used as a tracer particle for PIV. Instead of costly Nd:YAG laser, Light Emitting Diode (LED) which is relatively inexpensive and alterable in terms of wavelength and only one high speed camera with CMOS sensor were used for the simultaneous measurement system. To validate the constructed simultaneous measurement system, dispersion of the confined oil jet with high temperature was investigated. The instantaneous temperature and velocity field were obtained when 200 oC of silicon oil was injected into the 25 oC of the silicon oil chamber. For the temperature field analysis, the decay – slope method was used, and the velocity field was obtained by two-frame cross correlation algorithm. The instantaneous temperature and velocity field were obtained successfully with 0.1 second time interval. It is investigated that the velocity of injected silicon oil was rapidly decreased because of the change of viscosity of silicon oil over temperature. And the injected high temperature silicon oil was cooled by surrounding low temperature silicon oil. Therefore, the velocity of oil jet was decreased rapidly and was dispersed widely. The temperature gradient is also related to oil jet dispersion. The temperature difference before and after of a dispersion point appears significantly, since the temperature of silicon oil difference between the spread widely area and non-spread area. The temperature filed and velocity filed were obtained successfully by simple simultaneous measurement system using thermographic phosphor tracer.