Sensitivity of the Critical Speeds of a Rotor to Changes in the Design

Abstract

When designing a rotor it is frequently required to shift one or several critical speeds by making proper changes in rotor dimensions. This paper presents a scheme for computing the percentage change in critical speed as caused by a percentage change in any element of the rotor model. In this way it becomes possible to determine which elements are the most critical, and by how much they should be changed to effect the desired shift in critical speed. Such data also make it possible to adjust a given rotor model to bring it into agreement with measurements. The method can readily be incorporated into the conventional critical speed calculation and the additional computing time is insignificant.