Tham khảo tài liệu 'sổ tay tiêu chuẩn thiết kế máy p34', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | STANDARD HANDBOOK OF MACHINE DESIGN Qi and the carryover Q2 flows so that Tu T . It is further assumed that there is no energy generation and negligible heat transfer. Hence for the unloaded portion of the film QiTi Q2T2 Q2 QI Tl Next an energy balance is performed on the active portion of the lubricating film Fig. . The energy generation rate is taken to be F U J and the conduction heat loss to the shaft and bearing are taken to be a portion of the heat generation rate or KFjUU. Accordingly peiC T - s Q C Ta PQ2C T2 0 Combining Eqs. to and assuming that the side-flow leakage occurs at the average film temperature Ta T 2 T2 2 we find that JpC Ta-F 1 2Q2 Q 4n j C f l-X P 2-QJQ Q RCNL 1 This shows that the lubricant temperature rise is 1 A times the rise when conduction is neglected. LIQUID-LUBRICATED JOURNAL BEARINGS In the hydrodynamic operation of a liquid-lubricated journal bearing it is generally assumed that the lubricant behaves as a continuous incompressible fluid. However unless the lubricant is admitted to the bearing under relatively high hydrostatic head the liquid film can experience periodic vaporization which can cause the film to rupture and form unstable pockets or cavities within the film. This disruption of the film is called cavitation and it occurs when the pressure within the bearing falls to the vapor pressure of the lubricant. Narrow liquid-lubricated bearings are especially susceptible to this problem. Figure illustrates the general film condition in which lubricant is admitted through a lubricating groove at some angular position 0O. Clearly incomplete films complicate the analysis and therefore the design of a liquid-lubricated journal bearing. LID Effects on Cylindrical Full Journal Bearings Long-Length Bearings. When the length of a bearing is such that L 2D the axial pressure flow term in the Reynolds equation may be neglected and the bearing performs as if it were infinitely long. .
