Direct lubricated tilting two pads bearing with 890 mm diameter for large steam turbine was developed. Its performance, both static and dynamic characteristics, and reliability were tested with full scale test, after confirmation by thermo-hydrodynamic calculation coupled with finite element method deformation analysis, to evaluate deformations of the bearing pads. As a result of full scale test, it was confirmed that all of the target values were satisfied. In the same manner, robustness tests, changing the tilt angle of the shaft and supply oil condition were also conducted, and sufficient safety operations of the test bearing were also confirmed. Compared to the conventional bearings, the friction loss of the developed bearing was less than half of other types, such as flooded type, or direct lubricated four pads bearing.

No abstract

In this paper, vibrational frequency effect in dynamic coefficients of tilting pad journal bearing is verified experimentally. Tilting pad journal bearings (TPJB) is applied in various turbomachinery. Accurate evaluation of the bearing characteristics of TPJB is very important to ensure reliability of rotating machinery. To evaluate the stability of such rotating machinery for sub-synchronous vibration accurately, examination of damped vibrational frequency effects in dynamic coefficients of TPJB under various bearing load condition is necessary. In this study, excitation test with test rig of 4pad TPJB with two types of preload or pad offset ratio is carried out in various load condition. Especially, the test condition where the influence of fluid inertia is small is focused. Frequency effect in dynamic coefficients of TPJB is verified experimentally under the test condition. And, thermo-elastic-hydrodynamic-lubrication (TEHL) analysis is carried out. By comparing analytical results to experimental results, good agreement with experimental result and TEHL analytical result is confirmed. In addition, the influence of bearing load, load direction, pre-load or pad offset ratio on frequency effect is confirmed experimentally and analytically. The results that the frequency effect is larger as bearing load is lower (Sommerfeld number is larger), and the influence of pre-load of bearing on frequency effect is small and that of pad offset ratio (pivot position) is large is obtained.

No abstract

The demand for improving the steam turbine economic efficiency is being expected for both GTCC and conventional power plants. MHPS suggests HP/IP/LP separate casing and one bearing/rotor (one bearing between two casings) type steam turbine to enhance the turbine efficiency and reduce the cost of construction. Separate casing is preferable for blade aerodynamic performance, and one bearing/rotor is effective to reduce turbine bearing mechanical losses and turbine length. From the view point to design this type of rotor shaft arrangement, the most important point is to apply bearing technologies to permit the higher specific load and lower mechanical loss as well as for better dynamic oil film characteristics. The new two pads tilting journal bearing has been developed, utilizing MHPS’s experience on traditional two pads bearing with direct lubrication. The bearing structure and design parameters are optimized and good static and dynamic performance are obtained. Further, as practical countermeasures for a sub-synchronous vibration, the oil supply nozzle efficiency is improved, while properly adjusting supply oil flow distribution. The 610 mm size bearing test was conducted in-house test facility. The limit of specific load was verified, the bearing loss has become less than target.