Experimental tests on large size tilting pad journal bearings for turbomachinery

This article reviews some experimental results obtained with two different but same size tilting pad journal bearings with four pads typically used in turbomachinery. One bearing is a ball-in-socket type with 60% pad offset, and one a flexure-pivot type with 50% offset. Firstly the experimental apparatus and the fundamental procedures used are briefly reported. Stiffness and damping coefficients are evaluated from the experimental results obtained in load-between-pad configuration for both bearings for two different load levels and several shaft rotational speeds. The trends of the dynamic coefficients obtained for two loads for each bearing are shown as a function of the rotational speed of the shaft. Each bearing exhibits almost equal direct coefficients with similar trends for the two bearings. The values of the direct stiffness coefficients seem to be a little greater for the flexure-pivot bearing compared to the ball-in-socket one.