INFLUENCE OF BEARING LOAD ON THE PERFORMANCE OF TILTING-PAD JOURNAL BEARING UNDER HIGH SURFACE VELOCITY

摘要

Tilting-pad journal bearings (TPJBs) are dominant as shaft support in high-parameter turbomachinery, particularly in highspeed applications. Bearing test technology and high-precision model simulation are the key technologies for the development of high-end bearings. A bearing test platform which is based on the active magnetic bearing (AMB) loading and excitation is first designed and developed. Two large AMBs are used in the test rig as loader and exciter, and the system has a whole loading capacity up to 20000 N. As the bearing load is not always along the vertical direction, the performance of five-pads TPJBs with inner diameter of 140 mm is tested under the different load directions and load magnitudes in the speed range of 2000 to 12000 r/min. The results indicate that the direction and magnitude of the bearing load have a considerable effect on the experimental characteristics of TPJBs, especially under high-speed and heavy-load operation conditions. The bearing load has less influence on power loss than the rotation speed. By changing the direction of load, the bearing pad in the load direction has much higher temperature than the opposite pad. The change of pad temperature caused by the change of bearing load direction becomes greater under a larger bearing load. By analyzing the influence of the magnitude and direction of the bearing load on the rotor vibration, the mutual relationship among the dynamic stiffness, bearing load and rotor vibration are revealed. The performance test of TPJBs under different load directions with the AMB loading is beneficial to design the tilting pad bearing with high performance, to reduce the power loss of bearing, and to verify the correctness of the numerical model analysis. The results can be used for the performance prediction of the integrally geared centrifugal compressor because of their ever varying bearing load direction and load magnitude.