Experimental investigation on the performance characteristics of tilting pad journal bearings for small ratios

Many journal bearings exist in an engine. Therefore, the effects of operation and design parameters of a journal bearing on power loss are the important information. In this study, simplified estim...

Simplified estimation method of bearing friction for engines

Journal bearings work under severe conditions of speeds and loads are far away from working at Newtonian condition due to the high shearing rate of the fluid in this case with cavitation at its divergent zone. The main goal of the present work is to study the journal bearing performance considering combined effects of nonlinearity behavior of the working fluid, cavitation, and the bearing liner elasticity. For this purpose, a finite length cylindrical journal bearing working with nonNewtonian lubricant modeled and analyzed numerically considering the effect of parameters. The analysis was implemented by solving the main governing equations using a suitable prepared computer program. The flow of lubricant assumed laminar, incompressible, and isothermal. Lubricant shear stress assumed to vary with a shear rate according to the power law with index coefficient (λ) varies from 0.7 to 1.3 while the cavitation effect included by implements Elrod's cavitation algorithm (ECA). The elastic deformation is considered by calculating the radial component of the bearing liner elastic deformation which is a function of the elasticity coefficient κ. Different parameters investigated in static analyses and the numerical model validated by comparing the results of pressure and density ratio obtained in the present work with that obtained by Ye et al., (1994) and they are found in a good agreement. The results obtained showed an increase in oil film pressure and the load carried by the bearing while the coefficient of friction decreases when the bearing lubricated with a non-Newtonian lubricant of a higher index. © 2020 Published by Faculty of Engineering * Corresponding author: Mushrek A. Mahdi E-mail: msb.mushrek.alawi@uobabylon.edu.iq Received: 5 September 2020 Revised: 2 November 2020 Accepted: 21 November 2020

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Effect of Cavitation on the Performance of Journal Bearings Lubricated with Non-Newtonian Lubricant

Abrasive Water Jet Machining (AWJM) is an advanced machining process that has a variety of applications, including machining of hard-to-machine materials, drilling, milling, coating removal, polishing, etc. They are attractive because of their versatility, absence of heat-affected zones, low thermal-distortions, low cutting-forces, and environment-friendly nature. However, use of plain-water in AWJM poses some problems due to lack of jet coherence, poor suspension characteristics, and unsatisfactory performances in submerged-cutting and cutting of hollow surfaces. Countering these problems appropriately can lead to better cutting performances in terms of material removal rate, depth of cut, kerf-width, and kerf-taper. It can be achieved with addition of some additives in abrasive water-jet. These additives are mostly polymers of high molecular mass, which increases viscosity, suspension capability, and stability of jet, while reducing drag. In addition to AWJM, the effect of polymeric-additives in other water-based jets like Abrasive-Slurry-Jet (ASJ), High-pressure ASJ, etc. are also discussed. Therefore, this study aims to identify and list of different additives that are used in AWJM and other water-jet-based machining-processes over a past few decades, and to provide a run-through on their performances. It can provide the significant information to researchers working in fields related to waterjets. 

A review of additives in abrasive water jet machining and their performance

Viscosity index improvers cause the lubricants to exhibit non-Newtonian flow behaviour and display shear thinning and normal stress differences. Shear thinning behaviour is studied by using a rotary shear viscometer. Owing to the non-availability of a rheogoniometer (for the measurement of normal stress differences), the first normal stress difference is calculated from the viscometric data using the Carreau viscosity function. The influence of the first normal stress difference on the hydrodynamic lubrication is analysed and shows that most of the commercial oils are inelasticoviscous in nature. Regression analysis shows that a large number of commercial lubricants follow the inelasticoviscous cubic law fluid model. Hence the cubic law fluid model is considered for the theoretical analysis.An experimental programme is developed to measure the effect of test parameters on the performance of a journal bearing lubricated with different types of non-Newtonian fluids. The experiments mainly include the measur...

B S Prabhu

Papers

Thermohydrodynamic Analysis of Journal Bearings Lubricated by Non-Newtonian Fluids—Theory and Experiments