Influence of Injection Pressure on the Thermohydrodynamic Behavior of Tilting Pad Journal Bearings—Model and Experiment

Abstract

In rotating machines, tilting pad bearings (TPJBs) are widely used due to their enhanced design stability in comparison with alternative bearing configurations.In the present research, a thermohydrodynamic (THD) lubrication model for a tilting pad bearing with injection is developed. Within the THD lubrication model, the lubricant is also fed into each pad through a central injection orifice.The effects on the lubricant oil film pressures and temperatures and subsequent influences on the system dynamic behavior were investigated. Another important factor considered within the THD model is associated with the flexibility of the pivot of each pad and its impact on the behavior of the bearing when subjected to direct lubricant injection. The numerical model results are compared with the measurements of the rotor equilibrium position within the bearing and the pad temperatures obtained from the test rig designed specifically for the TPJB geometry with and without central pad injection. Pad temperatures are measured before the injection orifice position and after it. Agreement between experimental and model-predicted results provides confidence in the model's ability to evaluate the dynamic behavior of the bearing and its effect on the complete system through the stiffness and damping coefficients.

Effect of direct injection and pivot stiffness on the static performance parameters of tilting pad journal bearings

“…This extra degree of freedom allows for real-time adaptation of the bearing to different operation conditions and demands. 2 This bearing configuration also effectively eliminates the cross-coupling forces typical of fixed geometry bearings, pointing out its superior stable characteristic. 3 In hydrodynamic bearings, the most common lubricants used are mineral oils.…”

“…Although this model may be simplistic, it represents well the inlet temperature of the considered TPJB and operating conditions. 2,[6][7][8] Figure 7(c)-(i) presents the temperature distribution at the film-bush interface. For the rigid pivot, the film temperature greatly increases downward the minimum film thickness, while for the intermediate pivot, the temperature steadily increases, without abrupt changes.…”

“…Varela et al 37–39 also verified theoretically and experimentally the feasibility of active TPJBs featuring the leading edge groove (LEG) concept. Bizarre et al 2 investigated the effect of pivot flexibility and direct injection on a TPJB, comparing theoretical predictions with experimental measurements, revealing promising results for theoretical models in rotor-bearing systems application. Jensen & Santos 40 investigated actively lubricated TPJBs to reduce coupled vibrations of the flexible rotor and flexible foundation, neglecting the thermal behavior of the TPJB with direct injection.…”

“…A three-dimensional temperature model accounting for radial injection and pivot flexibility is only presented in Ref. 2, with a comparison with experimental results. The current work continues the research presented in Refs.…”

“…The current work continues the research presented in Refs. 2, 8, presenting the effect of the supply pressure on direct injection and the effect of pivot stiffness on the predicted pressure and temperature fields of the lubricant. Novel results are also presented with respect to the shear driven torque, not previously estimated.…”