Coriolis effects in bladed discs
File(s)
Author(s)
Ruffini, Valentina
Type
Thesis
Abstract
New aero-engine architectures are currently being developed to satisfy the increasing demand for fuel-efficiency and lower noise, pushing the boundaries of todays design practice. These unproven designs require additional effort to ensure safety to high-cycle fatigue and flutter, widely acknowledged as a main risk for turbomachinery components. This calls for a new focus on phenomena that have been little investigated in the past due to their minor relevance for traditional designs, like the Coriolis effect. The Coriolis effect can cause an increase in the number of resonance frequencies, and generate global travelling-wave modes that can affect performance and flutter stability. Experimentally validated prediction and analysis methods are essential to ensure the accurate evaluation of the impact of the Coriolis effect on future engine designs.
The major finite element (FE) software packages were systematically assessed, and proven to provide reliable simulations of the dynamics of bladed discs when the Coriolis effect is included. Experimental modal tools for the detection and identification of the Coriolis effect are also needed, to provide accurate interpretation of the data for model validation and updating. For this purpose, a dedicated rotating test rig was designed and manufactured. A novel Multiple Input Multiple Output testing framework was developed, based on the use of an array of strain gauges and piezoelectric actuators in combination with a poly-reference identification method, for the extraction of the full set of modal parameters arising in a bladed disc from the Coriolis force.
The new technique allowed the successful recovery of Campbell diagrams, damping and strain mode shapes. Left displacement eigenvectors, which appear in the FRF formulation due to the Coriolis effect, could also be extracted and validated for the first time. An accurate comparison was conducted between the measurement data and the FE results, and confirmed the reliability of the new approach.
The major finite element (FE) software packages were systematically assessed, and proven to provide reliable simulations of the dynamics of bladed discs when the Coriolis effect is included. Experimental modal tools for the detection and identification of the Coriolis effect are also needed, to provide accurate interpretation of the data for model validation and updating. For this purpose, a dedicated rotating test rig was designed and manufactured. A novel Multiple Input Multiple Output testing framework was developed, based on the use of an array of strain gauges and piezoelectric actuators in combination with a poly-reference identification method, for the extraction of the full set of modal parameters arising in a bladed disc from the Coriolis force.
The new technique allowed the successful recovery of Campbell diagrams, damping and strain mode shapes. Left displacement eigenvectors, which appear in the FRF formulation due to the Coriolis effect, could also be extracted and validated for the first time. An accurate comparison was conducted between the measurement data and the FE results, and confirmed the reliability of the new approach.
Version
Open Access
Date Issued
2016-01
Date Awarded
2016-07
Copyright Statement
Attribution NoDerivatives 4.0 International Licence (CC BY-ND)
Advisor
Schwingshackl, Christoph W.
Cawley, Peter
Sponsor
Rolls-Royce Ltd
Grant Number
MEDY_P41191
Publisher Department
Mechanical Engineering
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)