Research on rheological and flow behavior of lubricating grease in extremely cold weather

Purpose - This paper aims to investigate the flow characteristics of lubricating grease in extremely cold weather in which it is difficult to convey the grease due to a huge pressure drop. Design/methodology/approach - The rheological behavior of grease at various temperatures is studied by a rotary rheometer to determine the constitutive equation of lubricating grease. Based on the Herschel-Bulkley (H-B) model, the flow pattern of grease is then simulated by computational fluid dynamics and compared with the test results. Findings - The yield stress increased dramatically when the shear rate was less than 1s(-1) in the rheological experiments of continuous shear mode, and the phenomenon was more significant with the decrease in temperature. The rheological data obtained from the continuous shear mode agrees with the H-B equation after the shear thinned. In extremely cold conditions, there is a large yield stress in the lubricating grease; the numerical results show that the viscosity of lubricating grease increased with an increase in temperature, and the viscosity and velocity of lubricating grease showed uneven distribution leading to difficulty of lubricating grease delivery. Originality/value - This paper focuses on the flow characteristics of lubricating grease in extremely cold area conditions which is studied rarely. In addition, the continuous shear model and oscillatory model are combined to establish the constitutive equations. Experiment and numerical simulation method are all used by establishing the H-B models.