tailieunhanh - Hydrodynamic Lubrication 2009 Part 11

Tham khảo tài liệu 'hydrodynamic lubrication 2009 part 11', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Temperature Analyses of Tilting Pad Thrust Bearings Sector Pads 173 11 a two-dimensional analysis of a sector pad taking into account the effect of centrifugal force on the lubricating oil Pinkus and Lund 15 a three-dimensional analysis of a fixed inclined rectangular pad bearing Ezzat and Rhode 9 and a three-dimensional analysis of a tilting sector-pad bearing taking into account only the inclination in pitch mode Tieu 10 . Fig. . Sector-type tilting pad bearing 20 Basic Equations A cylindrical coordinate system r 6 z is considered with the origin at the center of rotation of the disk see Fig. . Let the position of the pivot support be rp 6p . In the direction of pad thickness a coordinate z2 with the origin on the lubricating surface of the pad is used. Besides the usual assumptions of lubrication theory the following assumptions are made 1. The lubricating surfaces of the pad and the disk are rigid and their thermal and elastic distortions are disregarded. 2. The velocity gradient and heat conduction in the r and 6 directions can be ignored in comparison with those in the z direction. 3. The specific heat at constant pressure cp and the coefficient of thermal expansion av of the lubricating oil are constant. 174 8 Heat Generation and Temperature Rise 4. The thermal conductivity of the lubricating oil ko and the thermal conductivity of the pad ks are constant. 5. The coefficient of viscosity U and the density p of the lubricating oil are functions of temperature T only. The basic equations in this case are stated below. Let the state when the lubricating surfaces of the pad and the disk are parallel to each other and their separation is hoR be the standard state. Assume that the pad rotates around the x axis by ap pitching angle and around the y axis by ar rolling angle from the standard state. Then the gap h between the pad and the disk film thickness is given by the following equation assuming a small inclination of the pad ap 1 and ar 1 h r 0