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Design And Construction Of Journal Bearing Demonstration Riig
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In 1896, inspired by the work of Osborne Reynolds, Albert Kingsbury
conceived and tested a pivoted shoe thrust bearing. According to Dr.
Kingsbury, the test bearings ran well. Small loads were applied first,
on the order of 50 psi (which was typical of ship propeller shaft unit
loads at the time). The loads were gradually increased, finally reaching
4000 psi, the speed being about 285 rpm.
In 1912, Albert Kingsbury
was contracted by the Pennsylvania Water and Power Company to apply his
design in their hydroelectric plant at Holtwood, PA. The existing roller
bearings were causing extensive down times (several 16 outages a year)
for inspections, repair and replacement. The first hydrodynamic pivoted
shoe thrust bearing was installed in Unit 5 on June 22, 1912. At
start-up of the 12,000 kW units, the bearing wiped. In resolving the
reason for failure, much was learned about tolerances and finishes
required for the hydrodynamic bearings to operate. After properly
finishing the runner and fitting the bearing, the unit ran with
continued good operation. This bearing, owing to its merit of running 75
years with negligible wear under a load of 220 tons, was designated by
ASME as the 23rd International Historic Mechanical Engineering Landmark
on June 27, 1987.
Since then, there has been series of progressive
research carried out on bearings bringing to the advent of journal
bearings which are not so different from the bearings designed by
Osborne Reynolds and Albert Kingsbury which work on the same
hydrodynamic lubrication system.
1.3 RESEARCH PROBLEM
The
operating conditions of hydrodynamic journal bearings can be described
by a set of tribological variables called key operating parameters. For
example, the load level of a hydrodynamic journal bearing is described
by two parameters: the specific load and the sliding speed. The key
operating parameters most directly related to the bearing
lubricant-shaft contact are the oil film temperature, oil film thickness
and oil film pressure. These three key parameters can be determined by
experimental or mathematical means with varying levels of complexity.
Until
now, oil film pressure in hydrodynamic journal bearings has been
studied mainly by mathematical means, because the experimental
determination of oil film pressure has been a demanding or even an
unfeasible task. Under real operating conditions, there are typically
many practicalities that complicate the experimental determination of
true oil film pressure in a certain point or at a certain moment. The
oil film may be extremely thin and therefore sensitive to different
disturbing factors, for example defects in geometry. In addition, the
level of the oil film pressure may be extremely high or have a high
level of dynamic variability.
1.4 AIM AND OBJECTIVE OF THE PROJECT
The
research into the construction and design of the journal bearing
apparatus has several reasons and purposes which need to be achieved and
justified.
The main aim of the study was to determine the oil film
pressure in hydrodynamic journal bearings carrying realistic loads. In
addition, the relationship between the oil film pressure and other key
operating parameters of journal bearings such as eccentricity and shaft
speed was studied.
The study also included the determination of the
relationship between the speed of rotation of the shaft, the pressure
around the journal bearing and the oil thickness.
1.5 SCOPE OF THE PROJECT
The
design and construction of journal bearing demonstration rig covers a
very broad area. This area encompasses the design, design
considerations, construction, assembly, working conditions and governing
mathematical equations and laws. The design gives in depth details of
the construction and fabrication of the apparatus. The working
conditions consist of the loading, acting pressures and the variable
operating speed which the journal bearing apparatus undergoes. Relevant
design calculations and equations to include the Pressure head
calculation, Sommerfeld’s equation and number, Petroff’s equation and
Reynold’s equation to mention a few, are contained in this work.
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ABSRACT - [ Total Page(s): 1 ]The journal bearing demonstration rig is an apparatus which is used to study how pressure would vary around the section of a journal bearing at various speed of the shaft and loading conditions. The design of the journal bearing was done by the use of standard design procedures carefully stated within this work. The frame, the journal bearing, the journal shaft, the base plate and all relevant components of the apparatus were designed. Other parts not constructed were procured. The fabrication a ... Continue reading---
