Research on Measuring Oil Film Thickness Based on Laser-Induced Water Raman Suppression Method

In this work, using a 266 nm laser as the excitation light source of the detection system, the water Raman spectra under the oil film of different thicknesses were obtained based on the laser-induced water Raman spectroscopy technology. The Gaussian function fitting method was used to correct the interference of the fluorescence spectrum on the Raman spectrum. And then, the oil film thickness inversion model could be established according to the water Raman suppression method combined with the nonlinear least square optimization algorithm. The results show that the six oils' detectable oil film thickness range (92(#) gasoline, 0(#) diesel, Mobil oil 20w-40, Shell Helix10w-40, Lifeguard Fluid AG6 and crude oil) is from 0.19 to 379.22 mu m. The average relative error of oil film thickness prediction ranges from 8.14% to 15.81% according to the water Raman spectrum-oil film thickness inversion model. This method can realize the measurement of micron-level oil film under laboratory conditions.