In this paper dealing with the tilting pad journal bearing, experimental results are presented which show that, at higher shaft speeds, the leading-edge-groove (LEG) design has significantly lower operating temperatures to those of the conventional design of tilting pad journal bearing. Subsequent theoretical analysis has shown that this reduction in pad operating temperature is the result of feeding cool oil directly to the leading edge of the pad. This has the effect of reducing the amount of hot oil carried over from one pad to the next.

Testing and analysis of a profiled leading edge groove tilting pad journal bearing developed for light load operation is described. This bearing was designed for a generic, small, high speed steam turbine operating at projected loads of less than 25 psi (172.4 kPa) and journal surface speeds to 400 ft/s (122 m/s). On the second turbine application, a rotor instability was experienced with the oil flowrate reduced to optimize bearing steady state performance. This instability was eliminated by machining a taper on the exit side of the feed groove on each pad. At the reduced flowrate, the profiled groove bearing greatly improved the operating characteristics of the rotor system by reducing vibration amplitudes and stabilizing operation at speed. This paper is divided into two sections. The first section compares the rotordynamics analysis with test data that shows improved unbalance response and operating stability with the profiled groove bearing. The second section provides original insight of the effect of the profiled geometry on the bearing flow field using computational fluid dynamics models.

The effect of oil viscosity grade on the performance of tilting pad thrust bearings is examined in a wide range of shaft speeds and specific bearing loads. Data being discussed were obtained in tests carried out with 228 mm outer diameter (o.d.) and 267 mm o.d. bearings lubricated with ISO VG32 and ISO VG68 mineral oils in a fully flooded mode. In a low-speed range (below 40 m/s), the performance of the 228 mm bearing is analysed in terms of pad and collar temperatures, power loss and oil film thickness. Pad temperature and power loss are employed in the analyses of the 267 mm o.d. bearing operated at high sliding speeds of up to 115 m/s. The results show that there is a significant effect of oil viscosity grade on bearing main operating parameters. The substitution of ISO VG32 oil for ISO VG68 oil results in considerably reduced pad temperatures, lower power loss and thinner oil film thickness. However, no measurable difference in power loss was observed after the onset of turbulence. The influence of oil viscosity grade on pad temperature pattern is analysed. The thermal effect of oil viscosity grade on pad temperature pattern and power loss is also compared with the effect of offset pivot.

This article presents a report on an investigation into the performance characteristics of a steadily loaded pivoted shoe journal (PSJ) bearing that is lubricated with ISO VG 32 and VG 68 oils. The article describes a testing machine on which the experimental investigation was performed. Measurements of shaft torque, pad temperature distributions, oil inlet and outlet temperatures, oil flow rate, and eccentricity have all been recorded as functions of load and speed. The experimental results from both test oils are presented in graphical form and are compared with theoretical predictions obtained from the author's computer model of the PSJ bearing. These results showed that the thicker ISO VG 68 oil provided thicker oil films. However, it also had higher bearing temperatures and power losses. A good correlation between the theoretical and experimental results has been found. Theoretical analysis of the bearing friction losses indicate that shear losses predominate and churning losses account for approximately 20% of the total losses.

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