A Subharmonic Vibration Absorber for Rotating IVIachineryWe demonstrate a dynamic vibration absorber system which can be used to reduce speed fluctuations in rotating machinery. The primary system is modeled as a simple rotating disk, and the idealized absorber system consists of a pair of equal point masses which are free to move along identical, prescribed paths relative to the disk. The unique features of the proposed arrangement are that the absorbers are tuned to one-half of the frequency of the applied torque and, more importantly, that they are effective in the fully nonlinear operating range. These absorbers can, in the undamped case, exactly cancel a pure harmonic applied torque of a given order without inducing any higher harmonics, thus rendering a perfectly constant speed of rotation. A perturbation method is used to extend the results to the small damping case and to investigate the dynamic stability of the desired motion. Simulations are used to verify the analysis and to demonstrate the effectiveness of the device. 590

The goal of the present work is to investigate the performance of tautochronic centrifugal pendulum vibration absorbers (CPVA’s) for reducing torsional vibrations in internal combustion engines. This is carried out using a mathematical model for the torsional dynamics of an in-line, four-stroke, four-cylinder engine with dynamic absorbers. This model includes the inertial effects of connecting rods and pistons, the forces caused by gas pressure inside the cylinder chambers, and friction in the bearings. Three configurations of the CPVA’s are applied to the model, including (1) a single CPVA tuned to order 2, (2) a pair of CPVA’s tuned to order 1, (3) two CPVA’s with tuning orders 2 and 4. For purposes of direct comparison, the total moment of inertia is the same for all three configurations. Numerical simulations are carried out in order to evaluate the performance of each configuration. This preliminary study indicates that Configuration (3) offers the best results for minimizing the peak value of crankshaft angular acceleration.