Study On Raman Spectroscopic Determination Of Furfural In Transformer Oil By Microfluidic Extraction

It is of great importance to detect the aging characteristics of transformer oil to keep the safe operation of oil-immersed power equipment.Raman spectroscopy can be well used in the analysis of multi-feature composition,but due to the low content of aging feature in transformer oil,the effect of Raman detection is greatly affected.The application of microfluidic technology in Raman detection of aging characteristics in transformer oil can greatly improve the detection sensitivity.In this paper,furfural is taken as a typical aging characteristic in transformer oil,and the generation,transportation and fusion process of liquid droplets are simulated and analyzed.A microfluidic chip is made and a Raman detection platform based on microfluidic extraction is built.Based on the platform,the Raman spectrum detection research of furfural in transformer oil is carried out.The main work is as follows:(1)The mechanism of droplet formation in microfluidic chip was analyzed,and the T-shaped microflow channel model was built with COMSOL Multiphysics finite element analysis software.The generation,transportation and fusion process of liquid droplets in microfluidic chips were simulated and analyzed,and the main two-phase flow pattern in the microflow channel was explored.The effects of flow rate,channel structure and twophase viscosity on droplet diameter,droplet spacing and droplet generation time are studied,which provides theoretical guidance for the design of microfluidic chip and the selection of experimental parameters.(2)Based on the the simulation results,the channel structure diagram of microfluidic chip for droplet extraction is designed by Auto CAD software;Several common microfluidic chip materials were compared and analyzed.Glass and polydimethylsiloxane were selected as the substrate and cover of the microfluidic chip.Lithography and etching technology were used to prepare the male mold with microchannel structure,and the whole cover was prepared based on the molding method.Plasma assisted bonding was used to bond the substrate and the cover to complete the fabrication of the microfluidic chip.(3)A Raman spectroscopy detection platform for furfural in oil based on microfluidic extraction technology was established.For standard furfural oil samples with different concentrations,direct measurement in oil,methanol and deionized water as extractant,and methanol and deionized water as disperse phase in microfluidic system were carried out,respectively.The minimum concentration of furfural Raman assay was5.5 mg/L,2.75 mg/L,1.38 mg/L and 0.02 mg/L,respectively.(4)Based on the simulation analysis,the influence of two-phase flow rate on droplet formation and extraction rate in microfluidic chip was studied.The simulation results are in good agreement with the experimental results.For standard furfural oil samples with different extraction ratios,the traditional extraction method and Raman detection based on microfluidic technology were carried out,and the highest extraction rates were 58.89%and 78.65%,respectively,through experiment and calculation analysis.The microfluidic technology increased the extraction rates to 1.33 times of the original.The minimum concentration of furfural can reach 0.01 mg/L at the optimal flow rate ratio of 2.75:1.