Research On Differential Detection Of Contaminants In Microfluidic Oil Based On Radial Magnetic Field

Oil plays an important role in the normal operation of various large mechanical and electrical equipment,especially the equipment with harsh working environment,such as offshore wind turbines,ocean-going ships,mining machinery.Nearly 80% of such equipment failures are caused by oil pollution.Therefore,it is essential to carry out fault warning and life prediction for equipment timely and accurately by rapid onsite detection or online monitoring of oil,to ensure safety and economy.This research is based on the National Natural Science Foundation of China.An opposite solenoid sensor was proposed according to the mechanism of impedance change caused by different particles in oil.Through COMSOL Multiphysics,the electromagnetic field simulation and parameterized dynamic scanning of the sensor were carried out,which provided a certain support and basis for the structural optimization of the sensor,changing the magnetic field of the sensor inductance mode detection area to a quasi-closed magnetic field.Solid Works was utilized to build a 3D model to guide the fabrication and process improvement of the sensor chip.An experimental platform was built,and oil samples mixed with different particles were prepared to be tested.In inductive mode and capacitive mode of the sensor,the three sensor chips having been optimized and having not been optimized were tested to see if the had the function of particle pollutant differentiation detection and counting.In addition,the optimal external excitation frequency of the sensor chip in capacitance mode and the detection lower limit of the sensor detection chip were also investigated.The experimental results show that the opposite solenoid sensor can detect ferromagnetic metal particles and non-ferromagnetic metal particles separately in inductive mode,and water droplets and bubbles separately in capacitive mode.In capacitance mode,the optimal external excitation frequency of the sensor without silicon steel sheet is 1.3MHz,while that of the sensor with strip silicon steel sheet and sensor with ring silicon steel sheet are 1.1MHz and 0.9MHz respectively.In inductance mode,the quasi-closed magnetic field formed in the detection area by ring silicon steel sheet sensor can realize the effective detection of iron particles above 20μm and copper particles above 80μm.The sensor with strip silicon steel sheet can detect water droplets above 70μm and bubbles above 110μm effectively in capacitance mode.Compared with the existing products of particle technology,the detection accuracy of this sensor is obviously improved.The sensor in this thesis provides new ideas and methods for the structure optimization and development of portable oil detection equipment and oil online monitoring system.