Study On Detection Technology Of Metal Abrasive Particles In Engine Lubricating Oil

Parts of engine will be worn out during operation,and the metal particles generated from the procedure will mix into the lubricating oil.The lubricating metal particles will intensify the abrasion rate of engine parts and lead to engine failure.Detection and recognition of the size,quantity and material of the metal particles in lubricating oil are conductive to define the wear parts and wear degree of the engine,which will contribute to conducting targeted maintenance and significantly improve the reliability of the engine.This thesis,taking a new inductive detection sensor of metal particle in lubricating oil as a research object,analyzed the magnetic field distribution of sensor and the disturbance properties of iron particles and copper particles to the magnetic field,verified the results through experimental researches subsequently.Firstly,this thesis recommended a sensor design with a multi-layer rectangular coil at its core to elaborate the detection principle of inductive detection sensor of metal particle,and to establish a mathematical model of the relationships among coil inductance variation and the number of turns of coil of sensor and metal particles based on Biot-Savart law.Secondly,a voltage-controlled oscillation circuit with excitation and detection functions was designed in detail and made into a real object.Through the circuit,the change of coil inductance caused by metal particles was transformed into frequency change to realize the detection of inductance change.Next,the thesis carried out simulation analysis on the factors that exerted influence on the functional relationship between coil inductance and metal particles via ANSYS Maxwell,thus determining the number of turns of coil of the sensor and verifying the feasibility of the sensor design.Then,the data acquisition system was designed by Lab VIEW software.And based on the principle of wavelet transform,MATLAB was used to conduct wavelet denoise for the collected frequency signal.Finally,the performance of the sensor to detect metal particles was tested through experimental researches.The results show that the sensor could identify iron particles of no less than 50?m and copper particles of no less than 100?m in a flow channel whose sectional area is 10mm~2,thus overcoming the problem that the sensitivity of traditional inductive sensor will decrease sharply when it is in a large flow channel.At the same time,an optimized measuring circuit is utilized to make sure that the noise amplitude that the sensor output remains steady at under 30Hz,thus improving the sensitivity of the sensor.In addition,adopting a structural mode with a multi-layer rectangular coil can increase the uniformity of the magnetic field and decrease the false positive probability of sizes of metal particles caused when many metals come into the detection area together.The research findings of this thesis have important theoretical and applied value in the detection of engine's metal particles in lubricating oil.