Study on the plasma spatial distribution characteristics of laser-induced breakdown on the oil-water interface

Abstract

The technology of oil-water separation is very important for the improvement of water resources and environment. The detection of oil-water interface characteristics is one of the key requirements of the technology. In this paper, the laser plasma spectroscopy is used to detect the oil-water interface, and the theoretical research and verification are carried out. The spatial distribution characteristics of plasma electron temperature and electron density are experimentally studied. The semi-ellipsoid model of laser plasma spatial distribution is proposed, combined with the laser focusing characteristic. The position of oil-water interface was determined by the laser-induced plasma spectroscopy based on the difference of element luminescent characteristics. According to the relationship between the intensity of spectral lines and the concentration of elements, the relationship between the intensity of characteristic spectral lines and the number of elements is obtained based on the semi-ellipsoid model. Furthermore, the relationship between the intensity ratio of characteristic elements and the thickness of the oil film is studied, and the spectral measurement of oil layers with different thickness is realized. In this paper, the law of the self-absorption effect of C and H elements with the thickness of the oil film is analyzed, and the rationality of the direct judgment of oil film thickness by the relative strength ratio of the characteristic elements of the detection spectrum signal is verified. According to the intensity ratio of spectral lines, the scatter distribution of oil thickness, and the simulation curve, the variation rule of experimental error with oil thickness are obtained. The relative error is less than 20%, which also verifies the reliability of the method.