Identification of rotor-stator rub and dependence of dry whip boundary on rotor parameters. (October 2021)

• Record Type: Journal Article
• Authors: Srivastava, Aman K.; Tiwari, Mayank; Singh, Akhilendra
• Is Part Of: Mechanical systems and signal processing. Volume 159(2021)
• Publication Date: 2021-10
• Subjects: Rotor Rub -- Smoothening Function -- Adaptive Chirp Mode Decomposition -- Full Spectrum -- Floquet Multipliers; Structural dynamics -- Periodicals; Vibration -- Periodicals; Constructions -- Dynamique -- Périodiques; Vibration -- Périodiques; Structural dynamics; Vibration; Periodicals; 621
• DOI: 10.1016/j.ymssp.2021.107845
• Languages: English
• ISSNs: 0888-3270

Abstract

Highlights: Use of Smoothening Function can significantly improve computation time. Full spectrum clearly identifies the backward whirl and instability in rotor. Rotor exhibits dry whip and shows bifurcation via Secondary Hopf Bifurcation. Dry whip frequency is directly proportional to stiffness ratio and damping ratio. Dry whip frequency is inversely proportional to friction coefficient between rotor–stator. Abstract: Rotor rub is one of the most critical and catastrophic event that occurs in gas turbine aircraft engines and other rotating machineries. Rotor rubbing introduces non-linearity in the system which makes the study of such phenomena difficult. The present study models a Jeffcott rotor along with a stator. This paper aims to develop a rotor rub model with Smoothening Function (SF) which can detect the onset of rotor rub efficiently whilst revealing the properties of Instantaneous Frequencies (IF) of rubbing rotor. First, the Adaptive Chirp Mode Decomposition Method (ACMD) has been used to detect the rub and establish the properties of IF. Next, the benefits of smoothening function in the rotor rub model have been discussed in terms of computation time. Further, the nonlinear dynamical behavior of the model has been studied using Poincare maps and Bifurcation diagram. The results reveal that IF of rotor possesses oscillating property which can be observed using ACMD method and can be used to detect the onset of rub. Moreover, use of SF effectively reduces the computation time by a factor of 11.6 when compared with classic rub model. The rotor orbits, Poincare Maps and Bifurcation diagram clearly shows that the rotor exhibits properties such as full annular rub, partial rub along with quasi-periodic motion. The presence of backward whirl using full spectrum has been observed and boundary for dry whip has been identified. Stability analysis using Floquet Theory reveals that the dry whip makes the rotor unstable. Dry whip boundary's dependence on the parameters such as rotor stiffness ratio, damping ratio and friction coefficient has been discusses in detail.