Abstract
Blade tip timing is a technique for the measurement of vibrations in rotating bladed assemblies. Although the fundamentals of the technique are simple, the analysis of data obtained in the presence of simultaneously occurring synchronous resonances is problematic. A class of autoregressive-based methods for the analysis of blade tip timing data from assemblies undergoing two simultaneous resonances has been developed. It includes approaches that assume both sinusoidal and general blade tip responses. The methods can handle both synchronous and asynchronous resonances. An exhaustive evaluation of the approaches was performed on simulated data in order to determine their accuracy and sensitivity. One of the techniques was found to perform best on asynchronous resonances and one on synchronous resonances. Both methods yielded very accurate vibration frequency estimates under all conditions of interest.
Highlights
Blade tip timing (BTT) is a vibration measurement technology that can be used to identify vibration problems in bladed assemblies through measurement of the passing times of blade tips under stationary points
This paper presents a new class of methods for the analysis of BTT data from assemblies undergoing two simultaneous resonances
Evaluation A consisted of varying the probe spacing on the resonance (PSR) values and noise levels simultaneously with the aim to determine the effect of PSR variation upon the ability of the methods to recover the correct frequencies of vibration
Summary
Blade tip timing (BTT) is a vibration measurement technology that can be used to identify vibration problems in bladed assemblies through measurement of the passing times of blade tips under stationary points. The aim of researching and developing BTT vibration measurement systems is to provide technically feasible cost-effective means to identify causes of potential blade failures. Blade tip timing has the potential to overcome many of the limitations of currently well-established systems, providing more information at a fraction of the cost. The main recent focus of BTT data analysis research has been the determination of frequencies when the vibration of the blades is synchronous. Synchronous vibration, known as integralordered or engine-ordered (EO) resonance, occurs when the response frequency of the blades is an integer multiple of the rotational speed of the assembly. The probes always detect the blade at the same phase of the vibration cycle, limiting the amount of data that is available for the estimation of the response frequency and amplitude
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