Effect of Slip Boundary Condition and Non-Newtonian Rheology of Lubricants on the Dynamic Characteristics of Finite Hydrodynamic Journal Bearing

In the present study, the influence of various slip zone locations on the dynamic stability of finite hydrodynamic journal bearing lubricated with non-Newtonian and Newtonian lubricants has been investigated. Linearized equation of motion with free vibration of rigid rotor has been used to find the optimum location of the slip region with maximum stability margin limit. It has been observed that bearing with interface of slip and no-slip region near the upstream side of minimum film-thickness location is effective in improving the direct and cross stiffness coefficient, critical mass parameter, and critical whirling speed. The magnitude of dynamic performance parameters with slip effect is highly dependent on the rheology of lubricant. Shear-thinning lubricants combined with slip boundary condition shows higher dynamic stability as compared to the Newtonian lubricants under the conventional boundary condition. For all considered rheology of lubricants, the dynamic stability of bearing with slip effect is improving by increasing the eccentricity ratio.

Prediction on Flow and Thermal Characteristics of Ultrathin Lubricant Film of Hydrodynamic Journal Bearing

This paper focuses on the flow and thermal characteristics of the lubricant film in the micro clearance of a hydrodynamic journal bearing (HJB) at high rotating speed. A thermohydrodynamic (THD) method consists of the Reynolds equation coupled with energy and viscosity-temperature equation with considering the cavitation is put forward. The 3D surface diagrams of the lubricant film thickness, pressure, temperature, liquid mass fraction, flow rate and heat dissipation distributions under different geometric, operating, slip and no-slip boundary conditions are systemically exhibited and analyzed. The results show that with the rise of eccentricity or length diameter ratio, the maximum peaks of pressure, temperature and heat dissipation are rapidly increased, the cavitation is aggravated, and the flow rate is accelerated in different extent. As the bearing speed accelerating, the maximum peak of temperature is strongly increased, whereas, the distinction between peaks of flow rate and heat dissipation is magnified and reduced, respectively. It provides a fruitful inside view of the inner flow and thermal characterizations of HJB for further understanding its flow-thermal interaction mechanisms and offers theoretical support for improving its working performance.

A Review on Improvement of Hydrodynamic Journal Bearing by using Bio-Lubricant

Journal bearings typically consists of metal sleeve that fits around a shaft. The sleeve is held in place within a housing. The journal is simply place on the shaft that is surrounded and supported by the bearing. Journal bearings can be made out of metallic or non-metallic materials such as bronze, aluminium etc. Bearings are generally made out of material that is softer than the metal of the shaft. Journal bearings typically consists of metal sleeve that fits around a shaft. The sleeve is held in place within a housing. The journal is simply place on the shaft that is surrounded and supported by the bearing. Journal bearings can be made out of metallic or non-metallic materials such as bronze, aluminium etc. Bearings are generally made out of material that is softer than the metal of the shaft. Typically, journal bearings are used in various applications such as turbines, compressors, centrifugal pumps etc. The performance of hydrodynamic journal bearing is depend upon the lubrication. Lubrication provides a thin film between internal sliding surfaces of the bearing components to reduce friction. Nowadays crude oil uses increases day by day. Due to depletion of petroleum resources, increasing its price and environmental pollution interest is developed towards the use of economical, environment-friendly lubricants. Bio-lubricants are made from vegetable oils. They are environment-friendly, non-toxic and also having performance benefits such as high viscosity index, high lubricity, high load carrying capacities, rapid biodegradability etc. In this review paper, to improve performance of hydrodynamic journal bearing and also to replace petroleum oil different types of bio-lubricants were examined.