Tham khảo tài liệu 'hydrodynamic lubrication 2011 part 12', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 214 9 Turbulent Lubrication In reference to the coordinate axes x and y of Fig. elastic coefficient Kij and damping coefficient Cij are defined as Eq. using the oil film forces Px and Py where the positive direction of Px and Py are taken in the direction of -x and -y. The subscript 0 denotes the static equilibrium position. To obtain Px and Py first solve the turbulent Reynolds equation Eq. for the pressure multiply the obtained pressure by cos Ộ and sin Ộ integrate these with respect to Ộ to obtain PK and Pg see Fig. and finally transform these into Px and Py. Kxx o Kxy dPx dy dPy dx Kyy 0 C xx dPx n . Cxy dx 0 dPx _ A. Cyx dy 0 dPy dx Cyy dP dy 0 p dy 0 Fig. . Axes of coordinates horizontal vertical P d x Kyx 0 Figure shows three examples of the above-mentioned elastic coefficients and a damping coefficient Kxx Kxy and Cxx as functions of eccentricity ratio K0 with Pd as a parameter. The figure shows that the larger the pressure difference is the larger the value of these constants absolute values becomes. Further the value of Kxx for laminar flow is larger than that in the case of turbulent flow. The same can be said of Kyy although the data are not shown. The calculation conditions are as follows D 70 mm L 35 mm c mm N 4000 rpm U mPa the axial Reynolds number Ra wmc v 767-2540 wm is the axial average velocity the circumferential Reynolds number RM Rojf v 1418. Turbulent Lubrication Theory Using the k-s Model In the case of a journal bearing in which the eccentricity ratio of the journal is large the pressure gradient in the oil film is large. The mixing length used in the mixing Turbulent Lubrication Theory Using the k-E Model 215 Fig. . Spring and damping coefficients of a fluid film seal 36 length model is usually determined experimentally for small pressure gradients but it changes with pressure gradient. Therefore it is more reasonable to use the k-E model which is less affected by pressure gradient for .
