Groan Caused by Generation of Striped Pattern of Transfer Film on a Ventilated Rotor 2004-01-2788
It was reported that groan with a frequency synchronized with the rotation rate of a ventilated rotor is generated by contact of the friction pad with ripples on the vane/channel surface of the ventilated rotor.
However, this groan-generation model does not account for the difference in groan sound pressure between friction pads differing in the composition even when the friction pads have the same shape and compressibility.
In this study, the distribution of surface temperature of a rotating rotor, which was generating groan was examined. After the groan-generation test, elemental analysis of the rotor surface in the circumference direction was performed. As a result, the surface temperature in the vane area was about 50 °C higher than that in the channel area, and the adhesion of copper contained in the friction pad to the surface in the vane area was about 20% higher than that to the surface in the channel area. Subsequently, the relationship between the thickness of transfer film and temperature of the rotor was examined, and the thickness of transfer film was increased by 0.10micrometer with elevation of temperature by 50 °C.
These findings indicated that periodical changes in the frictional force caused by striped pattern of transfer film were the major cause of groan with a frequency synchronized with the rotation rate of a ventilated rotor.