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In this paper results are presented from a study that investigates the use of centrifugally driven pendulum vibration absorbers for the attenuation of engine torsional vibrations. Such absorbers consist essentially of movable counterweights whose center of mass is restricted to move along a specified path relative to the rotational frame of reference. These devices are commonly used in light aircraft engines and helicopter rotors. The most common designs use a circular path for the absorber, tuned to a particular order of rotor disturbance, although more recent developments offer a wider variety of paths. Our goal here is to evaluate the system performance for a range of path types with different types of tuning. This analytical study is carried out for a simple mechanical model that includes a rotor and an absorber riding along a quite general path. Approximate solutions are obtained using a perturbation scheme and compared with detailed computational results.

Laser Doppler anemometry measurements have been made in a motored rotary engine assembly. The purpose of this study was to compare the flow fields of two different rotor pocket geometries experimentally. Two-dimensional measurements were taken over a central plane grid during intake and early compression at a shaft speed of 2000 rpm and wide open throttle. This data is to be used to quantify the central plane flow field and to provide experimental data for comparison with current analytical models. Two rotor pocket geometries were examined. The first rotor pocket geometry was a leading deep recess, and the second was a centrally located symmetric pocket. The same production apex and side seals were used for both rotors. The reduced velocity data was displayed as vector field plots within a computer animation to facilitate observation of the flow field and comparisons to analytical models.