OH Measurement in Propane Diffusion Flames by a Laser Induced Fluorescence Using a KrF Excimer Laser

Abstract

Laser induced fluorescence was applied for the measurement of OH concentration in the propane diffusion flames. A tunable, narrow band KrF excimer laser was used to excite the A(ν'=3)←X(ν"=0) band of OH radical. An emission spectrum of the induced light from the flames was measured by a spectroscope. An OH fluorescence component was picked up from the emission spectrum in order to obtain the accurate distribution of OH fluorescence in the flames. We call this method for spectrum-LIF (S-LIF). The spectrum of the induced light from the diffusion flames was compared with that of the premixed flames. Although the spectrum had only OH fluorescence components in the case of premixed flames, high intensity emission from the yellow flame appeared on the LlF image in the case of diffusion flames. To remove the high intensity emission from the LIF image, off resonance image was deducted from the OH resonance image as the background image. Using this deduction method, a planer laser induced fluorescence (P-LIF) was tried to measure the distribution of OH fluorescence. OH fluorescence distribution measured by P-LIF was compared with that of S-LIF. As the result, the P-LIF image qualitatively agreed with the data of S-LIF.