• Tribology and Lubricants
• /
• v.32 no.1
• /
• pp.1-8
• /
• 2016

This paper focuses on the thermal deformation induced preload change in the tilting pad journal bearing, using a three-dimensional (3D) thermo-hydro-dynamic (THD) approach. Preload is considered as a critical factor in designing the tilting pad journal bearing. The initial preload measured under nil external load and nil thermal gradient is influenced by two factors, namely, the thermal deformation and elastic deformation. Thermal deformation is due to a temperature distribution in the bearing pads, whereas the elastic deformation is due to fluid forces acting on the pads. This study focuses on the changes induced in preload and film clearance due to thermal deformation. The generalized Reynolds equation is used to evaluate the force of the fluid and the 3D energy equation is used to calculate the temperature of the lubricant. The abovementioned equations are combined by establishing a relationship between viscosity and temperature. The heat transfer within the bearing pads, the lubricant, and the spinning journal is calculated using the heat flux boundary condition. The 3D Finite Element Method (FEM) is used in modeling the (1) heat conduction in the spinning journal and bearing pads, (2) thermal gradient induced thermal distortion of the spinning journal and pads, and (3) viscous shearing, and heat conduction and convection in a thin film. This evaluation method has an increased fidelity, and it can prove to be a cost-effective tool that can be used by designers to predict the dynamic behavior of a bearing.

• The KSFM Journal of Fluid Machinery
• /
• v.9 no.5 s.38
• /
• pp.7-13
• /
• 2006

In the present study, we develop an analysis module to be applicable to design of sliding thrust bearings. The pressure equation is solved by using the finite element method. Average lubricant temperature is obtained from using the energy balance method. The module developed has been applied to three types of thrust bearing, such as tapered-land thrust bearings of angular and diamond types, and tilting-pad thrust bearings. Effects of the dam of the tapered-lad thrust bearings have also been investigated. It has been seen that the tapered-land thrust bearings of angular type result in the highest load capacity, while the tilting pad thrust bearings result in the lowest lubricant temperature. It has also been seen that the dam in the tapered-land thrust bearings increases both the load capacity and lubricant temperature.

• Tribology and Lubricants
• /
• v.33 no.2
• /
• pp.37-44
• /
• 2017

A DE-side LBP tilting pad journal bearing of a 1-stage overhung heat-pump compressor in a propylene process exhibited abnormal high-temperature behavior. Its temperature had been relatively high at $78^{\circ}C$ from the beginning of operation. In 2014, after three years of operation, it increased suddenly and reached $103^{\circ}C$. Installing a varnish removal equipment and others managed to stabilize the temperature at $95^{\circ}C$. We undertook a troubleshooting approach for reviewing the comprehensive status and integrity of the temperature design of the bearing. We performed lubrication and heat-balance analysis, based on the design engineering data and documents supplied by the OEM. For the base design data of DE-side TPJB, evaluating the effects of key design variables on bearing metal temperature showed that firstly, increasing the bearing clearance and supply oil flow-rate, and next, changing the oil type, and finally, increasing the machined pad clearance and offset, are more effective in reducing the bearing metal temperature. Furthermore, a clarification meeting with the OEM revealed that an incorrect decision had been made to decrease the bearing clearance to eliminate the SSV harshness issue, while not maintaining a sufficient oil flow-rate. We conducted a detailed retrofit design analysis, wherein we increased the oil flow-rate and bearing clearance by decreasing the preload. We predicted that the bearing temperature would decrease to $63^{\circ}C$ from $75.7^{\circ}C$ even at the rerate condition. Finally, after installing and operating a retrofit replacement bearing in 2015, the bearing temperature stabilized at a low temperature of $65^{\circ}C$. Currently (January. 2017), two year later, the bearing metal temperature remains at $65^{\circ}C$. Therefore, we can conclude that the abnormal high-temperature behavior of the bearing has been resolved completely.

• Tribology and Lubricants
• /
• v.32 no.4
• /
• pp.107-112
• /
• 2016

This paper presents a rotordynamic analysis of the reduction gear system applied to the 250 kW super critical CO₂ cycle. The reduction gear system consists of an input shaft, intermediate shaft, and output shaft. Because of the high rotating speed of the input shaft, we install tilting pad bearings, rolloer bearings support the intermediate and output shafts. To predict the tilting pad bearing performance, we calculate the applied loads to the tilting pad bearings by considering the reaction forces from the gear. In the rotordynamic analysis, gear mesh stiffness results in a coupling effect between the lateral and torsional vibrations. The predicted Campbell diagram shows that there is not a critical speed lower than the rated speed of 30,000 rpm of the input shaft. The predicted modes on the critical speeds are the combined bending modes of the intermediate and output shaft, and the lateral vibrations dominate when compared to the torsional vibrations. The damped natural frequency does not strongly depend on the rotating speeds, owing to the relatively low rotating speed of the intermediate and output shaft and constant stiffness of the roller bearing. In addition, the logarithmic decrements of all the modes are positive; therefore all modes are stable.

• Tribology and Lubricants
• /
• v.5 no.2
• /
• pp.77-82
• /
• 1989

The influences of ram pressure on the performances of tilting-pad journal bearings are investigated experimentally. The test rig consists of a single tilting-pad and a rotating journal. Film thicknesses and pressure distribution of the lubricating film are measured continuously for several values of coordinate of the pivot position and journal speed. The findings of the investigation are as follows: (]) According as the journal speed increases the ram pressure increases, maximum pressure decreases and the pivot position which maximize the minimum film thickness shifts toward the leading edge. (2) The ram pressure makes it possible to generate the converging wedge and the positive pressure between the pad and the journal even when the pad is supported at the points between the leading edge and the center of the pad. (3) The influence of the ram pressure on the performance of tilting pad bearings is significant and must be considered in the design of these bearings.

• Tribology and Lubricants
• /
• v.22 no.4
• /
• pp.173-181
• /
• 2006

In the present study, we developed a numerical analysis software to predict performance of tilting-pad thrust bearings. The finite element method was adopted to compute lubricant film pressure and temperature. Three-dimensional heat transfer equations were solved simultaneously for the lubricant film, pad, and runner. Groove temperature was assumed with two different models. From application of the software to a thrust bearing, it has been seen that the three-dimensional analysis predicts higher temperature than the average temperature analysis. It has also been found that the groove model with a hot-oil-carry-over factor predicts higher temperature.

• Tribology and Lubricants
• /
• v.13 no.3
• /
• pp.33-41
• /
• 1997

In this paper the linearized stiffness and damping coefficients of tilting pad thrust bearing are calculated by the perturbation method. The coefficients are obtained for a wide range of pivot positions. The effects of exciting frequency and pad mass on stiffness and damping coefficients are investigated. Critical frequencies due to the tilting motions of the pad are presented and are shown to be strongly influenced by the pivot position and the pad mass.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
• /
• 2002.10b
• /
• pp.113-114
• /
• 2002

Radial, tilting 12-pad proceeding bearings are applied as the radial bearings of vertical rotors of water turbines. The mean loads are stable at the peripheral speeds of proceeding reaching 50 m/s. The operation of tilting 12-pads proceeding bearing has been introduced at the assumption of adiabatic oil film. The oil film pressure, temperature and viscosity distributions have been obtained by iterative solution of the Reynolds', energy and viscosity equations. The resulting oil film force, minimum oil film thickness, power loss, oil flow, maximum oil film pressure, maximum temperature have been computed for different load angle of bearing.

• Tribology and Lubricants
• /
• v.33 no.3
• /
• pp.112-118
• /
• 2017

Tilting pad journal bearings(TPJBs) are widely used for high speed rotating machinery owing to their rotordynamic stability and thermal management feature. With increase in the rotating speed of such machinery, an increasingly important aspect of TPJB design is the prediction of their thermal behaviors. Researchers have conducted detailed investigations in the last two decades, which provided design tools for the TPJBs. Based on these previous studies, this paper presents a thermohydrodynamic(THD) analysis model for TPJBs. To calculate pressure distribution, we solve the generalized Reynolds equation and to predict the lubricant temperature, we solve the 3D energy equation. We employ the oil mixing theory to calculate pad inlet temperature; further, to consider heat conduction via the pad, we solve the heat conduction equation for the pads. We assume the shaft temperature as the averaged oil film temperature and apply natural convection boundary conditions to the pad side and back surfaces. To validate the analysis model, we compare the predicted pad temperatures with those from previous research. The results show good agreement with previous research. In addition, we conduct parametric studies on a TPJB which was used in a gas turbine simulator system. The predicted results show that film temperature largely depends on the rotating speed and oil supply condition.

• Tribology and Lubricants
• /
• v.30 no.2
• /
• pp.77-85
• /
• 2014

This study set out to predict the load capacity and rotordynamic coefficients of tilting-pad journal bearings, taking the pivot stiffness into account. The analysis uses rocker-back (cylindrical) and ball in socket (spherical) pivot models, both of which are based on Hertzian contact stress theory. The models ascertain the non-linear elastic deformation of the pivots according to the applied load, pivot geometry, and material properties. At present, the Reynolds equation for an isothermal, isoviscous, and incompressible fluid is used to calculate the film pressure by using the finite-element method, after which the Newton-Raphson method is used to simultaneously find the journal center location, pad angles, and pivot deflections. The bearing analysis, excluding the pivot models, is validated using predictions those are readily available in the literature. As the rotor speed increases, the predicted journal eccentricity and damping coefficients decrease, but the stiffness coefficients increase, as expected. Most importantly, the implementation of the pivot models increases the journal eccentricity but significantly decreases the stiffness and damping coefficients of the tilting-pad journal bearings.