Identification of Mixed Operational Modes in Rotating Machinery Using the TVDFT Order Tracking Technique

In this paper, the TVDFT Order Tracking technique (Time Variant Discrete Fourier Transform) is used to process complex non-stationary signals, generated by real measured signals. The method is applied in an experimental set-up for several run-ups, in order to identify the forward and backward precession movement in the directional order map. In this map, the negative orders are related to the backward and the positive ones to the forward orbit movement. The directional order maps are obtained for several rotor stations in order to identify the mixed operational modes, i.e., when some stations of the rotor describe their precessional movement in the forward direction while others move in the backward direction simultaneously. The experimental results showed the influence of the spatial distribution of the imbalance in the occurrence of the mixed operational modes.