Tuning of centrifugal pendulum vibration absorbers operating in a fluid

Abstract The linear and nonlinear tuning of centrifugal pendulum vibration absorbers operating in a fluid is addressed. These devices are used to reduced engine order torsional vibrations in rotating machinery. They are frequently housed in a rotating enclosure filled with a fluid, an important example of which is the automotive torque converter. The pressure field in the rotating fluid generates an effective buoyancy on the pendulum mass, thereby affecting its oscillation frequency. This effect is well known for simple pendulums operating in a static fluid under gravity, and is herein generalized to the case of a finite-sized centrifugal pendulum operating in a rotating fluid. A sample shape for the pendulum absorber is considered in detail, showing how the the expected results from a simple, small volume absorber can be generalized to account for more realistic geometries. The main results provide a convenient method for tuning the linear and nonlinear dynamics of the pendulum motion to account for the effects of the surrounding fluid. It is also shown that ignoring the fluid effect can lead to ineffective, and even catastrophic, operation of the pendulum absorber.