ROTORDYNAMIC TESTS OF A FLEXIBLE ROTOR ON FLEXURE PIVOT JOURNAL BEARINGS AND STABILITY CORRELATION WITH FREQUENCY DEPENDENT CHARACTERISTICS

摘要

A series of performance, unbalance response, and stability tests were performed on a flexible rotor incorporating two flexure pivot tilt-pad journal bearings, followed by a theoretical correlation using synchronous and frequency dependent bearing characteristics. The test data consisting of Bode plots and frequency cascade plots are presented along with measured bearing performance data, including peak temperatures at different speeds. Unbalance tests consisted of applying a midspan unbalance. Effects of oil inlet flowrate and oil inlet temperature are examined. The measured peak responses are compared to the theoretical in five measurement planes. Stability tests consisted of running the balanced rotor up in speed to provide a high flexibility ratio and reduced logarithmic decrement. For these cases, the motion of the rotor was measured in five planes and results are presented in the form of cascade diagrams. The tests were conducted under a series of operation conditions by varying the speed, oil inlet temperature, and flowrates. High amplitude resonant whip instability did not occur; however, low amplitude limit cycle instability did occur, which aided in determining the stability threshold. Correlation of the test results to the theoretical logarithmic decrement was performed using both synchronous and nonsynchronous bearing coefficients, both with and without pivot rotational stiffness. Based on the results of this study, the theoretical model with the nonsynchronous bearing coefficients best represents the rotorbearing system. Pivot rotational stiffness had little effect.