Measurement of Lubricant Viscosity and Metal Particles Using Dual Coil Inductive Sensor

Lubricant is a critical component of a ship's power plant, and analyzing the information on the change of lubricant viscosity and the wear particle it carries is of great significance to realize the condition monitoring of the power plant. In this paper, we propose and design an inductive sensor capable of simultaneously detecting the viscosity, particle diameter, and velocity of lubricants. COMSOL was used to investigate the magnetic field, particle flow, and particle velocity characteristics. The inductance signal amplitude and velocity values of spherical iron particles of eight diameters passing through four levels of viscosity lubricants were collected. Based on this data, we plotted the particle diameter-inductance signal amplitude curves, viscosity-velocity (for different diameters), and diameter-velocity (for different viscosities) curves. According to the experiment, when the two unknown iron particles passed through the standard oil sample of 50 mm ² /s (20°C), the corresponding particle diameter can be obtained from the particle diameter-inductance amplitude curves as 300 μm and 278 μm, respectively. For the calibrated particle with a diameter of 300 μm, the viscosity-velocity (for different diameters) curve yielded the viscosity value of 53.382mm ² /s with an error of 6.76%. The estimated viscosity value of 54.73 mm ² /s was obtained by diameter-velocity (for different viscosity) curve for the non-calibrated particle of 278 μm, with an error of 9.46%. This detection technology provides a new research idea for marine lubricant testing.