2-D–3-D Combined Numerical Method for Optimal Design of Magnetic Field Generator in Analytical Ferrograph

Analytical ferrograph (AF) is mainly used for the wear debris analysis in the lubrication oil of mechanical equipment, and the high-intensity magnetic field establishment of magnetic field generator (MFG) in AF is one of the key problems in design of AF. This article proposes an analytical, numerical, and experimental methodology for magnetic field design of AF. Based on Ohm's law and Gauss's flux law, the magnetic flux leakage coefficient of MFG is obtained, and then, the theoretical value of magnetic induction intensity at the working air gap is calculated, which provides a basis for the numerical method. Then, a 2-D finite-element model (FEM) is established to determine the magnetic circuit parameters of MFG, and a 3-D FEM is further developed to determine the ferrogram position parameters. Through the numerical calculations, the influence laws of magnetic circuit parameters and ferrogram position parameters on the magnetic field of MFG are obtained, and the optimal parameter ranges are determined. A Gauss meter is used for the magnetic field measurement, and the error between the experimental and numerical results is obtained to verify the correctness of the proposed numerical method. The average error between the measured and numerically calculated values is 6.07%. This article provides a positive contribution for wear particle analysis and the quick and accurate ferrogram preparation by AF.