An experimentally validated modal model simulator for the assessment of different Blade Tip Timing algorithms

Abstract

Blade Tip Timing (BTT) technology is concerned with the estimation of turbomachinery blade vibration. A BTT system comprises two parts: (a) measurement system for blade tip arrival times ("BTT data"); (b) the analysis algorithms. Simulators that generate BTT data play a key role in BTT development since they enable an assessment of the performance of the different BTT algorithms. Such assessments are not feasible with real engine data since they require controlled conditions and knowledge of the true tip vibration as the reference.Most simulators in the literature are based on a simple spring-mass-damper model and commercially available ones have no physical underpinning. This work presents a novel realistic simulator based on the experimentally validated Finite Element (FE) model of a bladed disk (blisk). Transformation to modal space enables the efficient generation of simulated BTT data regardless of the complexity of the blisk geometry. The simulator is then used in a first-time comparative study of three principal BTT algorithm methods (autoregressive, sine fitting, two-parameter plot) under various conditions involving synchronous and asynchronous excitations with both single and simultaneous frequencies.The study clarifies obscurities in the methods and demonstrates the applicability of each method to different BTT system scenarios.

Network of Smart Tip-Timing Sensors in Distributed Blade Health Monitoring System

“…Unfortunately, previous attempts to standardize the requirements for the sensor signal and its initial processing have not been successful [19]. The issue of BTT system validation and uncertainty estimation has recently been studied under the Clean Sky 2 program [20] using the simulator [21] and rig testing.…”

The efficient inclusion of rotation-induced inertia effects in a shaft-blisk assembly model using zero-speed modes

“…The contribution of this paper is motivated by the need to upgrade a blisk simulator designed to generate blade tip timing (BTT) data for the development and validation of BTT algorithms [41]. In this simulator, the blisk motion is a superposition of rigid rotation, prescribed steady movement (i.e.…”

“…This latter component of the movement is represented by a modal superposition that uses modal data from the FE model at zero rotational speed. Transformation to modal coordinates is crucial for the efficient operation of the simulator since the effective number of blisk modes required for accurate convergence of the vibration response is typically much less than the number of degrees of freedom of the FE model [41]. In the current version of the simulator (i.e.…”

“…In the current version of the simulator (i.e. as in [41]), the modal equations of motion neglect rotational effects. This simulator was first used by the authors in [42] to investigate the effect of steady movement on BTT data.…”

“…Hence, the variation in rotational speed considered in [43] was only around 10%. Using the methodology presented in this paper, the authors' blisk simulator of [41,42] is upgraded to accommodate rotation-induced inertia effects, without speed restriction, by adding them to the modal equations as "external" excitations at discrete locations, so that the modal equations continue to be based on the zero-speed modes. The simulator is also upgraded to include the deflection of the shaft, but the parametric excitation effect introduced by the consequent in-plane vibration of the blisk centre [44] is not considered.…”