A new bladed assembly simulator and an improved two-parameter plot method for blade tip-timing numerical simulations

Abstract

The blade tip-timing measurement technique is presently the most promising technique for monitoring the blades of axial turbines and aircraft engines in operating conditions. Due to the high cost of experimental simulations of blade tip-timing–based condition monitoring methods, a numerical simulator for the vibrational behavior of bladed assemblies can be helpful for researchers interested in this field. So far, in most of the numerical simulators, the centrifugal effect of rotational speed on the natural frequencies is neglected. In this study, a new bladed assembly considering the centrifugal effect of the rotational speed for blade tip-timing numerical simulations is proposed. Moreover, an improvement in the engine order estimation algorithm in a two-parameter plot method is accomplished. In the assembly, blades are assumed to be cantilevered Euler–Bernoulli beams coupled together using linear springs. The finite element method is used to extract mass and stiffness matrices from differential equations of the system. By using the two-parameter plot method, the engine order of the excitation is detected. To examine the performance of the algorithm, Monte–Carlo simulation is implemented. The new simulator fulfills both cyclic symmetry and increase in the natural frequencies with increase in rotational speed. Engine order estimation with the new formulation in the two-parameter plot method is accurate. Hence, the new simulator and formulation for two-parameter plot method are reliable for numerical simulations.

Parameters Identification of Blade Multi-mode Coupled Vibration Based on Blade Tip Timing

“…Substituting ( 14) and ( 15) into (10), the forced vibration response of the free end can be expressed as:…”

“…However, BTT is a severely undersampled measurement method, which provides great challenges for the parameters identification of vibration based on BTT. In order to extract blade vibration parameters from undersampled signals, parameters identification methods such as Circumferential Fourier Fitting (CFF) method, single-parameter method, double-parameter method, and spatial methods have been developed [8][9][10][11][12][13]. The CFF method is simple and requires less data, so it is widely used in engineering.…”