ABSTRACT
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 and construction processes were carried out in the workshop. The shaft to be used was machined on the lathe machine to the design specification. So also was the bearing to be used. This was all explicitly discussed in this report. Frame construction was carried out by welding process also stated in the work. The spring damper support was another constructed part. The assembly was done in such a way that the eccentricity between the bearing and the shaft would exist so as to get results. Relevant formulas, derivation and equation models were used in carrying out calculations used to get mathematical results that can be used to compare the experimental results. It is observed in the graph plotted from the experimental results, that the speed is proportionally or linear to the pressure build up in the journal bearing. The pressure tapping (h5), shows the highest reading on the manometer board, ranging from 76cm for 1144rpm to 25cm for 572rpm due to eccentricity of the two centers (shaft and journal bearing).
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TABLE OF CONTENT Title page ……………………………………………………………………... i Certification page ……………………………………………………………... ii Dedication …………………………………………………………………….. iii Acknowledgment …………...……………………………………………….... iv Abstract ………………………………………………………………………... v Table of content ……………………………………………………………... vi List of figures ………………………………………………………………... x List of tables ………………………………………………………………… xi CHAPTER ONE 1.1Introduction………..........................................................................................1 1.2 Historical background……………………………………………………... 3 1.3 Research problem………………………………………………………….. 5 1.4 Aims and objectives of this project………………………………………... 6 1.5 Scope of this project……………………………………………………….. 6 CHAPTER TWO 2.1 Literature review …………………………………………………………. ..7 2.2 Theoretical background……………………………………………………10 2.2.1 Basics of bearings……………………………………………………….10 2.2.2 Classification of bearings ………………………………………………10 2.2.3 Hydrodynamic lubricated bearings…………………………………….11 2.2.4 Terms used in hydrodynamic journal bearing……………………………12 2.2.5 Assumptions in Hydrodynamic Lubricated bearings ……………………14 2.2.6 Important factors for thick oil film……………………………… ………14 2.2.7 Properties of bearing materials…………………………………... ……...15 2.3 Basic principle of Journal bearing ………………………………………..18 2.4 Working principle of journal bearing ……………………………………..19 2.5 Applications of Journal bearings…………………………………………. .20
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CHAPTER THREE
DESIGN AND CONSTRUCTION OF THE JOURNAL BEARING DEMONSTRATION RIG, AND EQUATION MODELS OF VARIOUS PARTS 3.1 Design of components…………………………………………………… .21 3.1.1 The journal shaft………………………………………………………..21 3.1.1.1 Shaft analysis………………………………………………………….21 3.1.1.2 Design………………………………………………... ……………..23 3.1.1.3 Dimensions……………………………………………... ……………..24 3.1.1.4 Construction…………………………………………. ……………..24 3.1.2 The journal bearing…………………………………………………… 25 3.1.2.1 The design calculation………………………………………………….25 3.1.2.2 Dimensions…………………………………………….. …….……….31 3.1.2.3 Construction…………………………………………. …….……….32 3.1.3 The frame……………………………………………………... ………32 3.1.3.1 Design……………………………………………….. ……………...33 3.1.3.2 Dimensions…………………………………………….. ……………...33 3.1.3Construction………………………………………………………………34 3.1.4 The Base plate………………………………………………….. .............35 3.1.4.1 Design……………………………………….……….. ……………..35 3.1.4.2 Dimensions……………………………………......................................35 3.1.4.3 Construction…………….….…………………………. …………….35 3.1.5 Electric motor ………………….….……………………………………..36 3.1.5.1 Specification …………………………………………………………...37 3.1.5.2 Reason for selection……………………………………. ……………37 3.1.6 Coupling………………………………………………………….. ……..38 3.1.6.1 Reason for selection …………………………………………………38 3.1.7 Oil pipes/tubes …………………………………………………………38 3.1.7.1 Reason for selection ………………………………………...................39
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3.1.8 Fasteners …………………………………………………………………39 3.1.8.1 Functions ………………………………………………………………39 3.1.9 Lubricant (oil)………………………………………………………….40 3.1.9.1 Properties of lubricants ……………………………………………….40 3.1.9.2 Specification ………………………………………………………….42 3.1.9.3 Reason for selection…………………………………………………42 3.1.10 Oil collecting pan ……………………………………………………42 3.1.11 Oil reservoir/tank …………………………………………………........42 3.1.12 Spring damper support ………………………………………………42 3.2 Design consideration and selection of materials ………………………….43 3.3 Assembly of the apparatus ………………………………………………43 3.4 Working principle of the journal bearing test rig …………………………46 3.5 Operating conditions ………………………………………………………46 3.6 Operating instructions ……………………………………………………46 3.7 Mathematical Models and Calculations…………………………………47 3.7.1 Bearing Characteristics number for journal bearing ……………….........48 3.7.2 Critical pressure of the journal bearing …………………………….........48 3.7.3 Sommerfeld number …………………………………………………….49 3.7.4 Heat generated in a journal bearing …………………………………….49 3.7.5 Heat dissipated by the journal bearing ………………………………….50 3.7.6 Calculation on pressure head ………………………………………........51 3.7.7 Derivation of Sommerfeld’s and Reynold’s equation ………………….51 3.7.8 Derivation of Petroff’s equation ……………………………....................56 CHAPTER FOUR DISCUSION OF RESULTS, MAINTENANCE INSTRUCTION, SAFETY PRECAUTIONS AND STORAGE 4.1 Discussion of results..……………………………………………………61 4.2 Maintenance instruction..…..……………………………………………61
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4.3 Safety precautions …………………………………………………………62 4.4 Storage ……………………………………………………………………63 CHAPTER FIVE PROJECT COST ANALYSIS, CHALLENGES, CONCLUSION AND RECOMMENDATION 5.1 Project Cost Analysis………………………………………………………64 5.2 Challenges……………………………………………………………….66 5.3 Conclusion …………………………………………………………............66 5.4 Recommendation………………………………………………………….67 REFERENCES .................................................................................................69 APPENDIX A APPENDIX B APPENDIX C APPENDIX D APPENDIX E APPENDIX F APPENDIX G
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LIST OF FIGURES
Fig 2.1 Hydrodynamic Journal Bearing ………………………….………12
Fig 2.2 Journal Bearing During Operation…………………….…………18
Fig 2.3 Oil Film Pressure Distribution in Journal Bearing ………….…20
Fig 3.1 Construction of the journal….…………………………………24
Fig 3.2 Construction of the frame………………………………...……33
Fig 3.3 Frame Construction ……………………………………………34
Fig 3.4 Base Plate Construction …………………………………………36
Fig 3.5 Electric Motor………………………………………………….37
Fig 3.6 Oil Pipes …………………………………………………………38
Fig 3.7 First Phase of Assembly ……………………………………….44
Fig 3.8 Second Phase of Assembly ……………………………...…….45
Fig 3.9 Third Phase of Assembly ……………………………...…………45
Fig 3.10 Schematic Diagram of a Journal Bearing …………..……………51
Fig 3.11 Plain Journal Bearing Clearance versus Theta ……..……………55
Fig 3.12 Concentric Journal bearing ………………………………………56
Fig 4.1 Graph of speed of rotation against the pressure build up………60
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LIST OF TABLES
Table 2.1 Bearing Material Properties………………………………………17
Table 3.1 Dimension of the shaft…………………………..……………….24
Table 3.2 Journal bearing operating value and parameter…………………26
Table 3.3 Oil Types and Viscosities at Various Temperatures…………….28
Table 3.4 Dimensions of the Journal Bearing…………………………….32
Table 3.5 Dimension of the Frame…………………………………………34
Table 3.6 Dimensions of the Base Plate…………………………………….35
Table 3.7 Specifications of the Electric Motor…………………………….37
Table 3.8 Specification of the Oil………………………………………….42
Table 4.1 Results that shows variation of speed against pressure………..59
Table 5.1 Cost analysis table…………………………………………...65
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CHAPTER ONE
1.1 INTRODUCTION
Hydrodynamic journal bearings are typical critical power transmission components that carry high loads in different machines. In machine design, therefore, it is essential to know the true or expected operating conditions of the bearings. These operating conditions can be studied both by experimental and mathematical means, for example in test rig experiments, in field or laboratory tests with engines and by calculation or simulation.
Numerous studies of the operating conditions of hydrodynamic journal bearings have been made during the last decades. Still, the case is far from closed. For example, there are a limited number of studies that carry out an in-depth examination of the true operating conditions of bearings in true-scale experiments. There is also a need for experimental studies to verify the theoretical ones.
Fluid friction i.e. viscosity which exists in the lubricant being used is studied alongside the pressure effect which is being generated in the bearing, thus the effect of lubricants with different viscosities are considered.
A simple journal bearing consists of two rigid cylinders. The outer cylinder (bearing) wraps the inner rotating journal (shaft). A lubricant fills the small annular gap or clearance between the journal and the bearing. The amount of eccentricity of the journal is related to the pressure that will be generated in
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the bearing to balance the radial load. The lubricant is supplied through a hole or a groove and may or may not extend all around the journal. The pressure around the journal is measured on various manometers by means of pressure pipe/tubes. This is done at various speeds to get the relationship between speed and the pressure.