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Application of tilting-pad bearings in the design of large output turbines

Strzelecki S., Ghoneam S. M.

Transactions of the Institute of Fluid-Flow Machinery

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2003

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nr 114

201-208

EN

Modern steam turbines for electric power utilities have reached the output of 1000 MW per unit. It causes the need for an increase in shaft diameters and application of special tilting-pad journal bearings. The tilting-pad journal bearings are one of the options as they have very good hydrodynamic stability at high speed and are less sensitive to load direction and shaft misalignment. They allow for minimizing the oil flow too. In case of large output turbines, large diameter of heavy rotors the number of pads is restricted to three. The reliable design of journal bearings for responsible turbines is assured by calculation and analysis of static and dynamic characteristics of bearing. These characteristics can be determined from the oil film pressure and temperature distributions. The paper describes the possibilities of the application in large output turbines of some tilting-pad bearings. Static characteristics of these bearings can be obtained from the solution of Reynolds, energy, geometry and viscosity equations. Numerical method, assumption of incompressible lubricant, the laminar and adiabatic flow of oil in the bearing gap of finite length bearing and static equilibrium position of journal have been assumed.

2

Solving the nonlinear problem of gas-lubricated hybrid circular bearings. Part II: unsteady case

Nedelcu S., Postelnicu A.

International Journal of Applied Mechanics and Engineering

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2002

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Vol. 7, no 2

465-478

EN

In the paper, a dynamic analysis of gas-lubricated hybrid circular bearings is made. The mathematical model is the Reynolds equation in unsteady regimes along with the boundary conditions for a multiple connected domain. Within the hypothesis of a periodic relative motion of bearing surfaces, the method of small perturbations is used. The equations of the model are solved numerically using a difference finite method and finally, the curves of variation of the critical mass versus the eccentricity are obtained.

3

Solving the nolinear problem of gas-lubricated hybrid circular bearings. Part I: Steady case

Nedelcu S., Postelnicu A.

Applied Mechanics and Engineering

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2000

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Vol. 5, no 3

629-653

EN

In hybrid bearings, the carrying effect is produced by supplying under pressure and by the relative motion of the bearing surfaces. Because the pressure distribution in the bearing is the solution to a nonlinear partial differential equation of second order, the two causes cannot be studied separately and solving the problem is a difficult task. The mathematical model considered by us is the Reynolds equation for compressible fluids in a multiple connected domain. The boundary conditions on the inner boundaries are derived from the flow-rate continuity through the supplying orifices and are expressed as nonlinear integral-differential equations, which are solved numerically.