Research On Detection Method Of Marine Oil Contaminants Based On Cross-capacitance Microfluidic Chip

With the implementation of "One Belt,One Road",the shipping industry continues to flourish.As the working medium of marine machinery,marine oil is of great significance to maintain the normal operation of marine machinery and equipment.Ship oil usually refers to marine hydraulic oil and lubricating oil.Monitoring the health status of ship oil can effectively prevent mechanical failures and is also an important technical issue in fault diagnosis.The presence of moisture and air in marine oil can seriously affect the operation of machinery and equipment.However,the detection of moisture and air in oil is limited by the traditional parallel-plate capacitive sensor,which has certain limitations in detection accuracy and flux.In this thesis,a new type of cross-capacitance microfluidic chip ship oil pollution detection sensor is proposed,which can effectively distinguish and detect moisture and air pollutants in oil.At the same time,it has the advantages of small error source,high detection accuracy,and large flow channel flux.The main research contents of this thesis include:(1)The research status of moisture detection and air detection in oil and the theory of cross capacitance are briefly explained.The working principle of the cross-capacitance oil detection sensor for detecting the moisture and air in the oil is analyzed,and the theoretical correction of the cross-capacitance microfluidic chip is carried out.(2)Using COMSOL Multiphysics simulation software to model the cross-capacitance microfluidic chip structure and finite element analysis.The influence of the structural parameters of the cross-capacitor and the detection excitation on the detection effect was explored,and the reasonable parameter optimization of the cross-capacitance oil detection sensor is completed.The optimal axial length of the cross capacitor is 0.1mm by the control variable method;the aperture of the cross capacitor has the most obvious influence on the detection accuracy,and the diameter of the cross capacitor is set to 1mm through simulation comparison,which also greatly improves the flux;The excitation voltage has no effect on the detection effect.Through experimental analysis,the optimal excitation frequency is 1.9MHz.(3)Under the guidance of the simulation results,microfluidic chips were fabricated and an experimental bench for oil detection was built,and the methods of preparing experimental oil samples containing water droplets or bubbles of different sizes were explored.The oil samples containing various water droplets and bubbles are tested for oil.The experimental results show that with the increase of the diameter of the water droplets or bubbles in the experimental oil sample,the change of the cross capacitance is also larger,and the signal-tonoise ratio also increases.trend.At the same time,there is a good linear relationship between the change of cross capacitance and the diameter of water droplets and bubbles,which is consistent with the theoretical analysis and simulation results.(4)The lower detection limit of the cross-capacitance microfluidic chip for water droplets and bubbles in oil was explored.The experimental results show that the detection limit of water droplets in oil is 130～140μm,and the detection limit of air bubbles in oil is160～170μm.Compared with the traditional parallel-plate capacitive microfluidic chip,the detection limits of water droplets and bubbles are 180μm and 240μm,respectively.