基于层状PI薄膜FBG传感器的KCl浓度测量

KCl concentration measurement using FBG sensor based on layered PI film

为了监测核工业冷却管道中冷却剂的浓度,针对目前测量仪器易受环境干扰、介质沉积、难以分布式多点监测等问题,设计了一种基于层状聚酰亚胺(Polyimide,PI)的光纤布拉格光栅(Fiber Bragg Grating,FBG)浓度传感器。结合PI薄膜的吸水特性、水分子扩散原理和FBG传感理论,研究基于层状PI薄膜的FBG浓度传感机理,设计制作了层状PI薄膜FBG浓度传感器。最后,搭建浓度测量实验平台,进行浓度传感实验,得到镀层状PI薄膜的FBG浓度传感器对氯化钾(KCl)溶液的浓度特性曲线,并分析了其灵敏度与滞回特性。实验结果表明:浓度与波长漂移量呈线性变化关系,浓度特性曲线拟合度为0.9942,正、反行程输出的最大差值为35 pm,传感器的平均灵敏度为157.6 pm/(mol·L^(-1)),是同条件下镀一层环状PI薄膜FBG浓度传感器和腐蚀型FBG浓度传感器灵敏度的7.4倍和49.1倍。该传感器为核工业管道中冷却剂浓度测量提供了新方法,具有高灵敏度、安全、抗电磁干扰等优点。

A layered polyimide(PI)-fiber Bragg grating(FBG)concentration sensor was designed to monitor the concentration of a coolant in a nuclear cooling pipeline to solve various problems that exist in current measuring instruments,such as vulnerability to environmental interference,medium deposition,and difficulty in the distribution of multi-point monitoring.First,the design of a layered PI film-FBG concentration sensing mechanism was investigated based on a combination of the PI film water absorption characteristics,the principle of water molecule diffusion,and FBG sensing theory.Subsequently,the layered PI film-FBG concentration sensor was designed and fabricated,the concentration measurement experiment platform was built,and the concentration sensing experiment was conducted.Finally,the concentration characteristic curve of the PI film-coated FBG concentration sensor in a potassium chloride(KCl)solution was obtained,and its sensitivity and hysteresis characteristics were analyzed.The experimental results show that there is a linear relationship between the concentration and wavelength shift,and the fitting degree of the concentration characteristic curve is 0.9942.In addition,the maximum difference between the forward and reverse stroke output is 35 pm,and the average sensitivity of the sensor is 157.6 pm/(mol·L^(-1)),which are 7.4 times and 49.1 times higher than those of the one-layer annular PI film-coated FBG concentration sensor and corrosive FBG concentration sensor under the same conditions,respectively.Therefore,the sensor provides a new method for measuring the coolant concentration in nuclear industrial pipelines with high sensitivity,safety,and anti-electromagnetic interference.