Study On Metal Particle Magnetization In Harmonic Field And Mechanism Of Microfluidic Oil Detection

Oil as an energy transfer medium and a lubricant is widely used in industry. Hydraulic and lubrication systems, the solid particles are the major contaminants. More than75%of the hydraulic system failure, about35%of the diesel engine operational failure,38.5%of the gear failure and40%of the rolling bearing failure are caused by failure of oil, from which the importance of oil contamination analysis can be seen.According to oil analysis, first the paper carried out a study for metal particle magnetization characteristic in the magnetic field. Electromagnetics models for ferromagnetic and non-ferromagnetic metal particles are established in low and medium frequency harmonic magnetic field, and then impedance analysis method for metal particle is obtained. Base on this method different forms of microfluidic chip are designed for oil monitor, which can distinguish ferromagnetic metal particle, non-ferromagnetic metal particle and non-metal particle. Mass concentration for all ferromagnetic metal particles within oil can be measured by the chips. Based on impedance analysis, oil contaminants identification technology is given. Oil contaminants mentioned above were carried out on the quantitative analysis and experimental verification. Research priorities and achievements embodied in the following aspects:(1) The electromagnetism model is established for ferromagnetic and non-ferromagnetic metal particle in low or medium frequency harmonic magnetic field. Harmonic field magnetization theory for two types metal particle is obtained by solving differential equations, and using magnetization of metal particle harmonic field factor Kp to describe the magnetization state;(2) Effects of metal particle on general inductive sensors are analyzed and modeled, which illustrate that the inductance-resistance combined analysis achieve more accurate metal particle detection and size estimation. The model provides guidelines for sensor optimal design, under which the two forms of inductor microfluidic chips are designed in paper, and the model is verified by experiment.(3) Base on harmonic field magnetization theory, for metal particles below lower limit of detection, a method is presented for mass concentration detection. By modeling, low-frequency inductance signal is found increasing linearly with concentration of ferromagnetic metal particles, and low-frequency resistance signal is a complex function of concentration of non-ferromagnetic metal particles and size distribution. This paper tests with two chips to verify the feasibility of ferromagnetic metal particle concentration measurements.(4) Base on model of ferromagnetic concentration detection paper illustrate the feasibility to detect non-metallic particles, and modeling detector impedance change caused by non-metallic particle, which was verified by the experiment.(5) Comprehensive analysis of the impedance signal caused by four different oil contaminants, logical identification system is established for oil contaminants.Based on particle magnetization model within harmonic magnetic field, the effects of various oil contaminants on impedance signal detection of chip are studied in the paper, and geometry optimization basis of chips is presented. The device overcomes low detection sensitivity, simple oil contaminants and high detection costs of existing on-line detection method. The paper provides an important theoretical basis to achieve a variety of contaminants detection improve the detection sensitivity.