Investigation of possibility of flow field diagnostics by laser induced biacetyl phosphorescence

Experimental results of laser induced phosphorescence of biacetyl triplet³A _u in a mixture of biacetyl and N₂ show that: the lifetime of phosphorescence is a function of temperature and independent of density and concentration; the initial phosphorescence intensity is a linear function of density and insensitive to the variation of temperature. The temperature and density distribution of gas flow could be measured by observing the phosphorescence lifetime and initial intensity of biacetyl mixed with N₂ respectively. The velocity distribution could be measured by observing the time-of-flight of the gaseous phosphorescent spot under pulsed laser excitation. Compared with Doppler anemometer, it, to a great extent, avoids the particle lag problem in flow field with large velocity gradient. The phosphorescence decay mechanism is also analysed and the analytical results agree with experimental ones. The project supported by National Natural Science Foundation of China and The Third World Academy.