Đang chuẩn bị liên kết để tải về tài liệu:
Handbook of Lubrication Episode 1 Part 6

Tham khảo tài liệu 'handbook of lubrication episode 1 part 6', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 118 CRC Handbook of Lubrication FIGURE 12. Two elliptical oil lift pockets located at quarter points along a journal bearing axis. Removing the plug allows the supply passages to be flushed. with size. Al the area of a single bearing pocket is usually made about 1.5 of A in a bearing of this type. Once the load is lifted the pocket pressure falls because pressurized oil is distributed over the whole bearing area. The flow oil film thickness and other quantities can be calculated for this condition as a pure hydrostatic bearing before rotation starts . The lift is the following function of the purnp flow 14 This is the corrected form of Equation 12-19 in Reference 12. a numerical example will illustrate the use of the above equations where Q 0.07 sec 1.1 gpm D 533.4 mm 21 in. L 304.8 mm 12 in. CD 0.711 mm 0.028 in. W 382 500 N 86 000 lb n 2 pockets Al 2580 mm2 4 in.2 and ỊT 0.058 Pa-sec 8.4 greyn . Solving Equation 13 assuming KbA 3 gives a breakaway pressure of 21.1 MPa 3072 psi . The oil pump should be sized to give at least this much pressure with some margin say 50 to 100 to allow for performance deterioration over a period of time. Employing appropriate units Equation 14 gives an eccentricity ratio of 0.63. Assuming that the shaft moves straight up the lift equals the minimum film thickness 1- CD 2 or 0.132 mm 0.005 in. . This is a realistic value which will allow for some misalignment or shaft deflection. In thrust bearings somewhat more pocket area has historically been used than in journal bearings about 5 of the bearing area. The pad in Figure 13 is from a bearing with an outside diameter of 2286 mm 90 in. with a design load of 4.1 MPa 600 psi . At breakaway the pocket pressure rises to 12.4 MPa 1800 psi . It then falls back to a steady-state value of 4.8 MPa 700 psi . The lift h may be estimated by assuming a circular pressure distribution similar to the bearing in Figure 3. For the bearing pad in Figure 13 the following values may be assigned to the .