Journal Bearing Lecture Notes 2022 PDF

Design and Construction of machines Faculty of Engineering – PED 331 Alexandria University Dr Elsayed Saad Summer 2022 Lecture 4: Journal Bearings 1 Dr Elsayed Saad Summer 2022 Lecture...

Design and Construction of machines Faculty of Engineering – PED 331 Alexandria University Dr Elsayed Saad Summer 2022 Lecture 4: Journal Bearings 1 Dr Elsayed Saad Summer 2022 Lecture 4: Journal Bearings 2 Lecture 4: Journal Bearings Dr Elsayed Saad Summer 2022 Lecture 4: Journal Bearings 3 Dr Elsayed Saad Summer 2022 Lecture 4: Journal Bearings 4 Dr Elsayed Saad Summer 2022 Lecture 4: Journal Bearings 5  Journal Bearing Nomenclature Dr Elsayed Saad Summer 2022 Lecture 4: Journal Bearings 6  Plain surface Bearing & Journal Bearing The term plain bearing refers to that kind of bearing in which two surfaces move relative to each other. Thus, there is sliding contact. The actual shape of the surfaces can be anything that permits the relative motion. The common shapes are flat surfaces and concentric cylinders. Dr Elsayed Saad Summer 2022 Lecture 4: Journal Bearings 7 Journal Bearing The name journal bearing is sometimes used for plain surface bearing. For the case of bearing of a rotating shaft, the porting of the rotating shaft at the bearing is called the journal. The stationary part that supports the load is the bearing. Dr Elsayed Saad Summer 2022 Lecture 4: Journal Bearings 8 Dr Elsayed Saad Summer 2022 Lecture 4: Journal Bearings 9  Type of lubrication Dr Elsayed Saad Summer 2022 Lecture 4: Journal Bearings 10 Bearing Materials The bearing material may be: - Bronze - Babbitt - Aluminum - Porous Metals - Plastics (Nylon, TFE, PTFE, Phenolic, acetal,polycaebonate, filled polymide) Dr Elsayed Saad Summer 2022 Lecture 4: Journal Bearings 11 Lecture 4: Journal Bearings Properties of Plain Bearing Materials Low Coefficient of friction High Compressive Strength High Fatigue Strength Low Thermal Expansion High Thermal Conductivity Elasticity Conformability Embeddability Corrosion Resistance Bonding Relative Hardness of Bearing Material Availability of Material Cost of Material Dr Elsayed Saad Summer 2022 12 Lecture 4: Journal Bearings Bearing Design Task Bearing requirements: 1. Magnitude and direction of radial load. 2. Magnitude and direction of thrust load. 3. Rotational speed of the journal (shaft). 4. Frequency of start and stop and duration of idle period. 5. Magnitude of load when stop and during start up. 6. Environment in which will operate. Dr Elsayed Saad Summer 2022 13 Lecture 4: Journal Bearings Design decisions 1. Materials for the journal and the bearing. 2. Diameters, including tolerance of the journal and the bearing. 3. Nominal value and range of radial clearance. Bearing 4. Surface finish of the journal and the bearing. 5. Length of the bearing. Design Task 6. Method of manufacturing the bearing system. 7. Type of lubricant and the meaning its supply. 8. Operating temperature of the bearing system and the lubricant, 9. Method of maintaining the lubricant cleanliness and temperature. Dr Elsayed Saad Summer 2022 14 Lecture 4: Journal Bearings Analysis required 1. Type of lubricant; boundary, mixed, full film. 2. Coefficient of friction. Bearing 3. Minimum film thickness. Design Task 4. Thermal expansion. 5. Heat dissipation required and means of accomplishing it. 6. Shaft stiffness and slope of shaft in the bearing. Dr Elsayed Saad Summer 2022 15  Viscosity of Lubricating Oils Dr Elsayed Saad Summer 2022 Lecture 4: Journal Bearings 16  Dynamic Viscosity Units Dr Elsayed Saad Summer 2022 Lecture 4: Journal Bearings 17  Viscosity Of Some Common Substances At room temperature 21 Co Dr Elsayed Saad Summer 2022 Lecture 4: Journal Bearings 18  Bearing Parameter, mn/P mn/P Dr Elsayed Saad Summer 2022 Lecture 4: Journal Bearings 19  Bearing Parameter, mn/P For the highest value of mn/P, there is full fluid-film, or hydrodynamic, lubrication. In this regime of operation, the coefficient of friction attains a minimum of about 0.001 Wise designers will have the bearing operate at a higher mn/P value , paying for this margin of safety with some higher power loss. Dr Elsayed Saad Summer 2022 Lecture 4: Journal Bearings 20  Bearing Parameter, mn/P Full supporting lubrication film and consequently lower friction can be formed with higher values of mn/P. This can be established with: 1. High viscosity lubricant, m [mPa.s] 2. High operating speed ,n [rps], and 3. Light unit bearing load, P [MPa]. Dr Elsayed Saad Summer 2022 Lecture 4: Journal Bearings 21  Unit Bearing Load, P Dr Elsayed Saad Summer 2022 Lecture 4: Journal Bearings 22  Types of journal bearings Dr Elsayed Saad Summer 2022 Lecture 4: Journal Bearings 23  Mode of Operation of Full Bearing Dr Elsayed Saad Summer 2022 Lecture 4: Journal Bearings 24 Lecture 4: Journal Bearings Pressure Distribution in hydrodynamic bearing Dr Elsayed Saad Summer 2022 25  Design of journal bearing Dr Elsayed Saad Summer 2022 Lecture 4: Journal Bearings 26  Sommerfeld Number Sommerfeld number is more practical than bearing Characteristic Number. It considered the flow out the ends of the bearing. It is dimensionless variable. Design of bearing is based in using standard charts. Two additional quantities needed are: 1. The extent of bearing arc b 2. The length-to-diameter ratio L/D Dr Elsayed Saad Summer 2022 Lecture 4: Journal Bearings 27  Another form of S- Number  Heat Generated Rate Lecture 4: Journal Bearings  Heat Generated Rate Dr Elsayed Saad Summer 2022 Lecture 4: Journal Bearings 30  The at which lubricant is pumped by the shaft is found in Fig. 17.14. Some of this lubricant flows out of the ends of the bearing and has to be replaced by supply oil. The proportion that leak out the ends id found in Fig. 17.15. Dr Elsayed Saad Summer 2022 Lecture 4: Journal Bearings 31 Lecture 4: Journal Bearings Considerations Dr Elsayed Saad Summer 2022 32 Dr Elsayed Saad Summer 2022 Lecture 4: Journal Bearings 33 Dr Elsayed Saad Summer 2022 Lecture 4: Journal Bearings 34  Viscosity- Temperature Chart For SAE OILS (SI units) Dr Elsayed Saad Summer 2022 Lecture 4: Journal Bearings 35  Minimum Film Thickness Dr Elsayed Saad Summer 2022 Lecture 4: Journal Bearings 36 Position of Minimum Film Thickness Dr Elsayed Saad Summer 2022 Lecture 4: Journal Bearings 37  Coefficient of Friction Ratio Dr Elsayed Saad Summer 2022 Lecture 4: Journal Bearings 38 Flow Rate for full journal bearing Dr Elsayed Saad Summer 2022 Lecture 4: Journal Bearings 39  Side Flow for full journal bearing Dr Elsayed Saad Summer 2022 Lecture 4: Journal Bearings 40  Oil type ho f f Q Qs Dr Elsayed Saad Summer 2022 Lecture 4: Journal Bearings 41 Lecture 4: Journal Bearings Example Dr Elsayed Saad Summer 2022 42 Dr Elsayed Saad Summer 2022 Lecture 4: Journal Bearings 43 Dr Elsayed Saad Summer 2022 Lecture 4: Journal Bearings 44 Dr Elsayed Saad Summer 2022 Lecture 4: Journal Bearings 45 Dr Elsayed Saad Summer 2022 Lecture 4: Journal Bearings 46 Dr Elsayed Saad Summer 2022 Lecture 4: Journal Bearings 47 Dr Elsayed Saad Summer 2022 Lecture 4: Journal Bearings 48  (63.5 mm)] 41478 mm3/s 41.478 cm3/s Dr Elsayed Saad Summer 2022 Lecture 4: Journal Bearings 49  (41.478 cm3/s) 36.087 cm3/s Dr Elsayed Saad Summer 2022 Lecture 4: Journal Bearings 50 Dr Elsayed Saad Summer 2022 Lecture 4: Journal Bearings 51 Dr Elsayed Saad Summer 2022 Lecture 4: Journal Bearings 52