tailieunhanh - Bearing Design in Machinery Episode 3 Part 8

Tham khảo tài liệu 'bearing design in machinery episode 3 part 8', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | The velocities on the right-hand side of this equation are in Fig. 5-2. If the bearing is stationary and the shaft rotates the fluid film boundary conditions on the bearing surface are U1 0 V1 0 15-2 Under dynamic conditions the velocity on the journal surface is a vector summation of the velocity of the journal center O1 and the journal surface velocity relative to that center. The journal center has radial and tangential velocity components as shown in Fig. 15-1. The components are de dt C de dt in the radial direction and e df dt in the tangential direction. Summation of the velocity components of O1 with that of the journal surface relative to O1 results in the following components U2 and V2 see Fig. 5-2 for the direction of the components U2 oR esin 0 _ e f cos0 15-3 dt dt V2 oRdh de cos 0 edf sin 0 15-4 2 dx dt dt Here h is the fluid film thickness around a journal bearing given by the equation h C 1 e cos 0 15-5 After substitution of U2 and V2 as well as U1 and V1 in the right-hand side of the Reynolds equation Eq. 15-1 the pressure distribution can be derived in a similar way to that of a steady short bearing. The load components are obtained by integrating the pressure in the converging clearance only 0 0 p as follows Wx -2R x pp p 2 p cos 0 d0 dz Jo Jo Wy 2R pp pL 2 p sin 0 d0 dz Jo Jo 15-6 15-7 Converting into dimensionless terms the equations for the two load capacity components in the X and Y directions as shown in Fig. 15-1 become Wx J12IU1 J e J22 Wy J11U - j - e J12 15-8 15-9 Copyright 2003 by Marcel Dekker Inc. All Rights Reserved. Here the dimensionless load capacity and velocity are W - 3 W and U U 15-10 mU0L U0 where U oR is the time-variable velocity of the journal surface and U0 is a reference constant velocity used for normalizing the velocity. The integrals Jy and their solutions are given in Eq. 7-13 . Under steady conditions the external force F is equal to the bearing load capacity W. However under dynamic conditions the .