Actively controlled bearing dampers for aircraft engine applications

This paper describes some of the requirements for bearing dampers to be use d in an aircraft engine and briefly discusses the pros and cons of various types of dampers that were considered as candidates for active control in a ircraft engines. A disk type of electrorheological (ER) damper was chosen f or further study and resting. The paper explains how and why the choice was made. For evaluating potential applications to aircraft engines, an experi mental development engine (XTE-45) was used as an example for this study. L ike most real aircraft engines, the XTE-45 ran through more than one critic al speed in its operating speed range. There are some speeds where damping is desirable and other speeds where it is not. Thus, the concept of a dampe r with controllable forces appears attractive. The desired equivalent visco us damping at the critical speeds along with the available size envelope we re two of the major criteria used for comparing the dampers. Most previous investigators have considered the ER damper to produce a purely Coulomb typ e of damping force and this was the assumption used by the present authors in this study. II is shown in a companion paper, however, that a purely Cou lomb type of friction cannot restrain the peak vibration amplitudes at roto rdynamic critical speeds and that the equivalent viscous damping for rotord ynamics is different from the value derived by previous investigators for p lanar vibration. The type of control scheme required and its effectiveness was another criterion used for comparing the dampers in this paper.