Transient thermoelastic effects in fluid film bearings

A method is presented for the calculation of temperature in the shoe-film-rotor assembly of a thrust bearing. This method allows reverse flow to occur and simplifies the calculation of hot oil carry-over. An analysis is developed to propagate thermoelastic effects in time following a change in any operating condition such as load or speed. It is found that size effects can be correlated with a Fourier number F 0 = αt/ H 2 where H is the thickness of the rotor or shoe. The initial change in the bearing temperature is quite rapid but a Fourier number of at least 10.0 is needed to approach equilibrium in the new running condition. For large hydroelectric installations the time to equilibrium may be several hours (depending on size). It is doubtful whether the largest units in use ever achieve full thermal equilibrium because external operational changes occur before equilibrium is reached.