Tip-timing measurements of transient vibrations in mistuned bladed disks

Bladed disks are usually characterized by a rich dynamic response during service due to the occurrence of several mode shapes that vibrate at resonance within the operative range. In particular, during start-ups and shutdowns, the variable speed causes a temporary crossing of resonance that cannot be neglected to determine stress envelope and safety margins of the system during its whole mission. In fact, fluid flow induces fluctuating loads with variable frequencies (non-stationary regime) on the blades being responsible of a dynamic response which does not follow the so-called steady-state (stationary) response. This paper proposes a novel post-processing method for Blade Tip-Timing (BTT) measurements for the identification of the resonance parameters of mistuned bladed disks working in non-stationary operative conditions. The method is based on a two degrees of freedom model (2DOF) and focuses on transient resonances in which two mistuned modes with close resonance frequencies are involved in the dynamic response. In such circumstances, the identification method based on the single degree of freedom (1DOF) model usually fails.To verify the effectiveness of the method, numerical and experimental investigations have been performed. First, a mathematical simulator based on a lumped parameter model of a bladed disk system is used to generate the BTT simulated data. Experimental signals are measured using a commercial BTT system through a set of optical probes mounted circumferentially around a rotating dummy blisk. It is shown that the method produces accurate predictions for the numerical simulation, even in the presence of considerable noise levels. Moreover, experimental results confirm a successful implementation of the method on the actual BTT measurements

Vibration parameters identification of turbomachinery rotor blades under transient condition using Blade Tip-Timing measurements

During run ups and run downs, the rotating blades are subjected to fluctuating forces with time dependent frequencies and the dynamic response of the blades around the resonance crossings deviates from the stationary response. This paper presents a procedure to identify the vibration parameters of rotating blades under this non-stationary condition. An analytically based solution of a single degree of freedom (SDOF) system exposed to a transient harmonic excitation with linear time varying frequency is used for parameters identification. This analytical model is fitted into the Blade Tip-Timing (BTT) data and the vibration parameters are determined by a least square optimization technique. A numerical simulator based on a lumped parameter model of the bladed disk assembly is employed to demonstrate the method performance. Afterwards, the accuracy of the method is proved by testing it on the experimental data acquired by BTT and strain gauges on a rotating bladed disk

Aeromechanical optimization of first row compressor test stand blades using a hybrid machine learning model of genetic algorithm, artificial neural networks and design of experiments

202002 bcrcVersion of RecordPublishe

Investigation on behaviors of acoustoelastic cavities using a novel reduced finite element-dual reciprocity boundary element formulation

202303 bcwwVersion of RecordOthersThis work was sponsored by the philosophy and social scienceplaning project of Guangdong province [grant no. gd20ygl12],basic and applied basic project of Guangzhou city [grant no.202102020629], Philosophy and social science planning projectof Guangzhou city [grant no. 2121GZGJ48].Publishe