ROTARY MACHINE AND MODIFICATION METHOD THEREOF

PROBLEM TO BE SOLVED: To damp plural natural vibration modes of a rotation shaft of a rotary machine in a small installation space and by a small number of components.SOLUTION: A rotary machine in an embodiment comprises: plural bearings 2, 3 spaced from each other in an axial direction; a rotation shaft 4 that is supported by the bearings and has plural natural vibration modes of bending with the bearings as fulcrums, and on which a center hole 10 is formed along its axial center; plural support members 11, 12 spaced from each other in an axial direction inside the center hole 10 at plural axial positions different from axial positions at both ends of the plural bearings 2, 3; and a vibration control shaft 13 supported by the support members and having plural natural vibration modes of bending with the support members as fulcrums. A difference between each natural vibration frequency in the bending natural vibration mode of the vibration control shaft 13 and each bending natural vibration frequency in the bending natural vibration mode of the rotation shaft 4 is within a defined value.