Torsional Vibration of In-Line Aircraft Engines 380159
A DISCUSSION is presented of the two-node as well as the single-node characteristics for various crankshaft systems both with regard to frequency and to severity of vibration. The effect of frequency on harmonic torque input, which is a measure of vibration severity, also is discussed. The paper shows that, with a careful selection of the vibration frequency, the harmonic torque input for various vibration orders can be reduced considerably.
A method is presented for the selection rather than the determination of vibration frequencies. It shows that, by the careful selection of frequencies, certain harmonic orders both for single-node and two-node vibration can be minimized appreciably and/or eliminated from the normal operating range of the engine. The friction-type and the dynamic-pendulum-type vibration damper are discussed.
This paper brings out the fact that a definite restriction on vibration amplitude (degrees) cannot be used to limit the severity of torsional vibration. The allowable magnitude of vibration for safe operation depends upon the type of system being used and the relative specific power output of the engine. The stresses brought about by vibration must be considered before an intelligent restriction of vibration amplitude can be made.