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Handbook of Lubrication part 12

Tham khảo tài liệu 'handbook of lubrication part 12', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Volume II 443 FIGURE 34. Film damping for full journal bearing with ruptured oil film laminar flow Re 1000 . Stability of Full journal Bearings The stability characteristics of a rotor carried on full journal bearings ruptured film Type 2 BC supported on a rigid foundation can be estimated from Figure 35. The full journal bearing unruptured continuous film Type 1 BC is inherently unstable over its entire operating range. External damping in the system must be present to yield stable operation. More stable fixed-type bearing and the influence of bearing support flexibility can be found in References 32 and 33. Example determine the oil film-rotor stability given the following for a horizontal rotor D 2R 5 in. N 90 r sec 5400 rpm L 2.5 in. KS 5 X 106 lb in. rotor stiffness C 0.005 in. Rotor weight 5000 lb M 5000 386 13.0 lb sec2 in. 2 X 10-6 lb sec in.2 From Figure 35 P W DL 1 2 X 5000 5 X 2.5 200 psi S 0.225 with S L D 2 .0563 C W KS 10 and C W Mw2 0.005 2500 X 13.0 X 2 n X 90 2 8.28. Since coordinate point S L D 2 0.0563 C W M 2 8.28 lies below the curve for C W KS 10 the rotor is free of oil whip instability. PIVOTED-PAD JOURNAL BEARINGS Tilting-pad journal bearings consist of a number of individually pivoted pads or shoes. This pivoting capability enables relatively high loading in applications where shaft deflection or misalignment is a factor. Another advantage is their inherent stability since the load component from each pad passes through the journal center. A further advantage is that clearance can be closely controlled by making the pivots adjustable radially thus enabling Copyright 1983 CRC Press LLC Volume II 445 FIGURE 36. Preloading of a pad. 1 As machined and 2 preloaded Ob bearing pivot circle center. Oj journal center Op pad center rb bearing pivot circle radius rp pad radius and R journal radius. imbalance misalignment etc. and thus operate nearly concentric eo 0 with the journal. This is often undesirable because of the low-radial stiffness and .