Dynamic characteristics of polymer faced tilting pad journal bearings are presented. Investigations are conducted using a single pad, load on pad configuration over a range of shaft speeds and loads. Two polyether ether ketone (PEEK) faced pads, one polytetrafluoroethylene (PTFE) faced pad and two entirely PEEK pads are investigated to determine the effect of varying mean bearing pressure and pivot characteristics as well as different material properties of the polymer layer. Experimental results indicate increased damping and decreased stiffness and slightly increased oil film temperature for entirely PEEK pads compared to pads with a PEEK lining and steel backing. Similar effects were observed by using a softer (PTFE) pad liner with a steel backing.

New turbine oils providing both extremely high viscosity index (VI) and improved boundary/mixed lubrication performance are investigated. Comparisons are made in both laboratory scale testing using typical journal bearing sliding surfaces (steel and white metal) and full scale testing using a hydrodynamic journal bearing test machine. The results from these studies demonstrate the effectiveness of new, high VI, turbine oils for reducing friction at machine startup and improving performance during full film operation.

Experiments are conducted using a 10-MW Kaplan hydropower machine which is outfitted with an extensive array of sensors to determine oil film thickness, pad load and oil temperature in all three guide bearings as well as motion of the shaft in relation to both the bearing housings and the concrete foundation. Test results for all journal bearings are compared to a commercial rotor dynamics model and results for the central journal bearing are compared to a multi-physics model to provide insight into the machine's steady state and dynamic characteristics and their variations during normal operation.

The increasing introduction of intermittent power sources combined with the de-regulation of electricity markets has led to increased instability in the electrical grid. This has led to increased start-up and shutdown of regulating power sources such as hydro-electric power plants and operation at non-ideal operating states both of which increase the wear and tear on machines. Likewise, the push for a less environmentally intrusive society has raised the importance of utilizing equipment with reduced impact on the natural surroundings.These challenges lead to a need to improve the robustness of existing and new equipment to guarantee their usefulness in a future with increased instability. While many components in hydropower systems require thorough investigation to improve their robustness, this work is focused on the guide/journal bearings which support the rotating portion of power generating machines.This work addresses the journal bearing problem through a multi scaled approach covering small and large scale laboratory experiments as well as investigations of a full scale machine.A journal bearing test machine was constructed to investigate a number of new synthetic lubricants and polymer bearing materials. These tests found that a significant reduction in power loss could be accomplished without significantly affecting the bearing's minimum film thickness by changing from a traditional mineral oil to a high viscosity index oil of much lower base viscosity grade. The high viscosity index lubricants were then improved to reduce start-up friction as well. Further studies were conducted in small scale to determine the optimum lubricant characteristics for the startup problem. This knowledge was used to develop new lubricants to test in the journal bearing test machine which showed great reductions in power loss in the bearing and pumping system as well as greatly reduced bearing operating temperature.Further experimental work led to the development of practical guidance for power plant operators contemplating a lubricant change. This technique focuses on the importance of maintaining equivalent viscosity in the minimum film thickness region after a lubricant change. Efficiency improvements can then be calculated by comparing the viscosity in the bulk of the bearing to that with the original lubricant.Experimental work with polymer bearing facing materials demonstrated the dramatic reductions in break away friction that these materials can provide. A number of polymer composite materials were investigated for their friction characteristics at the moment of the start of sliding, finding that PTFE based materials were far superior to traditional Babbitt metal. This work with polymer faced bearings was extended to testing in a tilting pad journal bearing test rig which allowed for identification of the dynamic characteristics resulting from changes in bearing pad material.Investigations in the full scale with the Porjus U9 unit provided valuable insight into the dynamics of a full scale machine as well as needed data for the improvement of multi-physics models of bearings. Insights from the Porjus U9 experiments clarify many of the design challenges for large journal bearings.The results from this work demonstrate that significant performance improvement of journal bearings is possible through the use of new lubricants, materials, and adjustments in operational methods.

Experiments are conducted using a 10 MW Kaplan hydropower machine with a PowerFormerT M generator, the Porjus U9 research machine. This machine is outfitted with an extensive array of sensors to determine oil film thickness, pad tilting, pad load and oil temperature in all three guide bearings as well as motion of the shaft in relation to both the bearing housings and the concrete foundation. Test results for all three guide bearings are examined during both steady state and transient operation.

This study aims at investigating the tribological behaviour of several unfilled polymer materials sliding against 316L stainless steel in distilled water. The tests were carried out in a unidirectional pin-on-disc configuration with an initial apparent contact pressure of 5 MPa at room temperature. The worn surfaces were examined using scanning electron microscopy and energy dispersive spectroscopy techniques and the wear mechanisms were discussed. These studies indicate the occurrence of tribocorrosion of stainless steel during sliding against polypropylene. It is inferred that the frictional behaviour of the polymers is determined by both their wettability and solubility in water, where generally an increased hydrophobicity and relative energy difference with regard to water results in lower friction. The results from friction and wear tests show overall superior tribological performance of ultrahigh molecular weight polyethylene compared with the other polymeric materials in water.

This study investigates the tribological characteristics at initiation of sliding (break-away friction) of several polytetrafluoroethylene based materials. Four PTFE composites, pure PTFE, and white-metal were tested in a reciprocating tribo-meter with the block on plate configuration against a steel counter surface. Apparent contact pressure and oil temperature were varied from 1-8 MPa and 25-85\degc respectively. SEM investigations revealed wear patterns of the PTFE materials and the abrasive nature of hard fillers.Bronze-filled, carbon-filled, and pure PTFE were found to provide lower break-away friction and less variation over the course of testing and generally superior properties.

New lubricants providing both extremely high viscosity index (VI) and improved boundary/mixed lubrication performanceare investigated. Comparisons are made in both laboratory scale testing using typical journal bearing slidingsurfaces (steel and white metal) and full scale testing using a hydrodynamic journal bearing test machine. The resultsfrom these studies demonstrate the effectiveness of new, high VI, turbine oils at reducing friction at machine startupand improving performance during steady state operation.

Computational models were used to optimize bearing performance by adjusting a number of lubricant properties. This computational optimization showed that the most beneficial characteristics to hydrodynamic bearing operation were high viscosity index (VI) and high specific heat capacity. Four environmentally adapted synthetic lubricants were developed to provide these characteristics including: ISO VG32 with 259 VI, ISO VG22 with 245 VI, ISO VG22 with 336 VI, and ISO VG15 with 226 VI. A full scale bearing test machine was then operated with these lubricants in addition to mineral based turbine oils, ISO VG68 with 103 VI and ISO VG32 with 105 VI, to determine the effect on bearing performance and to validate the models. The new lubricants reduced bearing power loss by up to 20% and significantly reduced bearing temperatures with somewhat reduced film thickness. The machine was then operated to provide equivalent minimum viscosity with the new lubricants by varying inlet temperature, finding that changes in power loss were less substantial with equivalent minimum viscosity. Comparison of simulated and experimental results led to development of a simple, practical method to estimate benefits and operational parameters for lubricants based on viscosity grade, viscosity index and a simplified description of the machine's bearings. Other, less tangible, factors considered are bio-degradeability and impact of power loss reduction

The present study aims at investigating the tribological behaviour of several unfilled polymer materials sliding against 316L stainless steel in distilled water. The tests were carried out in a uni-directional pin-on-disc configuration with an initial apparent contact pressure of 5 MPa at room temperature. The worn surfaces were examined using scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) techniques and the wear mechanisms were discussed. These studies indicate the occurrence of tribo-corrosion of stainless steel during sliding against polypropylene. The results from friction and wear tests show overall superior tribological performance of UHMWPE compared to the other polymeric materials in water.