Object shape-based methodology for optical analysis of contaminated engine lubricants

Introduction of gasoline, water, coolant and other contaminants into the engine lubricant as well as the normal aging process affects the optical properties of liquid medium, such as transparency, absorption, and refractive index. A new methodology for optical analysis of contaminated engine lubricants is proposed and described in details in this paper. Novelty of the proposed methodology consists of obtaining and analysis of an optical image that combines an object with known periodical shape and lubricant. The object, e.g. a stainless steel woven wire cloth with a mesh size of 65×65 µm and a circular wire diameter of 33 µm was placed behind a microfluidic channel, containing engine lubricant and optical images of flowing lubricant with stationary object were acquired and analysed. Several parameters of acquired optical images, such as, color of lubricant and object, object shape width at object and lubricant levels, object relative color, and object width non-uniformity coefficient, were proposed. Measured on-line pa rameters were used for optical analysis of fresh and contaminated lubricants. Estimation of contaminant presence an d lubricant condition was performed by comparison of parameters for fresh and contaminated lubricants. Developed m ethodology was verified experimentally showing ability to distinguish lubricants with 1%, 4%, 7%, and 10% coolant contamination.