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Tham khảo tài liệu 'hydrodynamic lubrication 2009 part 13', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 210 9 Turbulent Lubrication Fig. 9.4a b. Results of calculation of the turbulent coefficients 33 for equal pressure gradients in the x and z directions a and for different pressure gradients b 1 Gx kx 12 1 axRhnx 1 Gz kz 12 1 azRhnz 9.53 where ax 0.00116 az 0.00120 nx 0.916 nz 0.854 These expressions were obtained using Eq. 9.33 as a coefficient of modification for the mixing length. Rh is the local Reynolds number. If Rh is sufficiently small Gx Gz 1 12 is obtained from the above and therefore Eqs. 9.51 and 9.52 are in agreement with Reynolds equation in the case of laminar flow. 9.4 Comparison of Analyses Using the Mixing Length Model with Experiments 211 9.4 Comparison of Analyses Using the Mixing Length Model with Experiments In this section some results of analyses of turbulent fluid film seals based on the mixing length model will be compared with experimental results. 9.4.1 Turbulent Static Characteristics of Fluid Film Seals Fig. 9.5. Fluid film seal 35 The turbulent static characteristics of a fluid film seal as shown in Fig. 9.5 are considered Kaneko et al. 32 35 . The turbulent Reynolds equation Eq. 9.51 or 9.52 is applied to the film of a seal and is solved by using the finite difference method. In the case of a fluid seal a big pressure difference exists between the two ends and a pressure loss takes place at the high pressure end where the liquid flows into the seal clearance. This is taken into consideration in the boundary conditions. The pressure loss is assumed to be expressed as follows when an average inflow velocity in the axial direction is wm J p Cl 9.54 where Cl is a pressure loss coefficient which according to experiments is given as follows Cl -Ro 2900 2.57 R0 Wmh v with a proviso that Cl constant when R0 1000. 9.55 9.56 212 9 Turbulent Lubrication R0 is the local Reynolds number in the axial direction. When the journal and seal are eccentric the average flow velocity wm changes with the position on the seal circumference and hence the .