激光击穿油水界面的等离子体空间分布特性研究

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

油水分离技术对水资源的治理和环境的改善非常重要,油水界面特性检测是该技术的关键要求之一.本文提出了采用激光等离子体光谱法进行油水界面探测的方法,并进行了理论研究和验证.本文实验研究了等离子体电子温度和电子密度的空间分布特性,并结合激光聚焦特性,提出了激光等离子体空间分布的半椭球模型;采用激光诱导等离子体光谱法,基于元素发光特性差异,对油水界面的位置进行了判定;结合谱线强度与元素浓度的对应关系,基于半椭球模型得到特征谱线强度与元素个数关系式;进一步对特征元素强度比值和油膜厚度关系进行了研究,实现了不同厚度油层的光谱测量.本文分析了C和H元素的自吸收效应随油膜厚度的变化规律,验证了采用检测光谱信号的特征元素相对强度比对油膜厚度直接判断的合理性.根据谱线强度比和油厚的散点分布,以及仿真曲线,本文得到实验误差随油厚的变化规律,并且相对误差总体小于20%,这也验证了该方法的可靠性.

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.