الفهرس 
The Temperature effectOnly 14 pages are availabe for public view
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Abstract
Investigations on thermal performance of journal bearing lubricant are very important. In this work, study of thermal performance characteristics of several lubricant oil types in a turbomachine journal bearing has been considered. The tested oils are mineral oil 68, synthetic oil 46, and other five blends of the synthetic and mineral oils. The five blends contain: 20, 30, 40, 50, and 70 percent of the synthetic oil and the remainders are of mineral oil.
An experimental study has been carried out on a specially designed test-rig. The test-rig consists of, DC motor 3 hp with variable speed controller, two journal bearings and closed lubrication system in addition to an open cooling system. Balancing is performed on the journal according to ISO 1940 under its physical conditions and at the actual speeds up 2000 rpm. The tested speeds are 200, 300, 400, 500, 1000, 1500, and 2000 rpm.
Experimental tests are executed on the tested journal bearing in three steps:The first step is dealing with plotting the maximum temperature and the hydrodynamic pressure and calculating the coefficient of friction at the maximum temperature for the lubricant oils at the tested speeds to determine the lubrication regimes for the system. The second step investigates the temperature, and the hydrodynamic pressure distributions along the circumferential direction at the mid point of the journal bearing for tank oil temperature of 40 oC, and gauge pressure of 0.75 bar at the different lubrication regimes. The third step is concerned with the thermal performance tests for the lubrication regimes conducted for the tested oils as a function of the treated oil temperature: 40, 60, 80, 90, and 100 oC. In addition the effect of different supply oil gauges pressures: 0.5, 0.55, 0.6, 0.65, 0.70, and 0.75 bar on the maximum oil temperature has been considered.
A theoretical study is performed using a commercial CFD code based on the control-volume method, FLUENT 6.1.22. The flow is treated as incompressible, steady and turbulent. The standard k- turbulence model with the standard wall function is used to predict the heat transfer over the oil film. Navier-Stokes equations are solved by a second-order up-wind scheme. The energy terms are evaluated using a second-order scheme.
The coupling between velocity and pressure in momentum equations is governed by the SIMPLE scheme. Use of blend oils leads to decrease the failure in the maximum temperature when it treated up to 90, and 100 oC. This process is coupled with the synthetic oil percent increase.
Comparison between experimental results and the theoretical analysis have been carried out to validate the mathematical model behavior. Results of predicted temperature distribution of the lubricant oil show suitable agreement with that of the experimental measurements.