PLANAR LASER-INDUCED FLUORESCENCE TECHNIQUE FOR MEASUREMENTS OF CONCENTRATION FIELDS IN CONTINUOUS STIRRED-TANK REACTORS

A new non-intrusive method based on laser sheet visualization and imag e processing has been developed to measure the instantaneous concentra tion fields of a nonreacting fluorescent dye in a continuous stirred t ank reactor. The method consists of measuring the fluorescence intensi ty of a tracer excited by a thin planar laser sheet and in transformin g it into an instantaneous concentration field of tracer by a calibrat ion procedure. This allows the characterization of mixing in a plane d efined as the cross section of the flow by the laser sheet. Flow visua lization images have been recorded on video tape and subsequently digi tized. The relationship between the intensity of the fluorescent light and the grey level of the images has been established. The first resu lt is the instantaneous field of dye concentration. A contacting param eter between the fluids coming from the two inlet sources, and emphasi zing the average state of the mixing, has been defined and its field h as been determined. The field of temporal variance, which characterize s the segregation of the investigated zone, has also been computed.