Periodic Reporting for period 1 - BRAVO (Establishing Blend Repair limit of blisks –from A perspective of Vibration amplificatiOn)
Reporting period: 2021-03-15 to 2023-03-14
Blisks are extensively used in the fan/compressor sections of advanced aeroengines, due to their reduced-weight and increased-performance benefits. However, they also suffer from notorious disadvantages of technical difficulty and high cost arising from the repair process if inevitable blade damages in service occur, e.g. foreign object damages and wear, etc. Efficient sustainment of the extremely expensive blisks requires that damaged blades can be cost-effectively repaired by blending operations with high reliability.
Structural dynamics evaluations for the repaired blisks are of significant importance to ensure continued safe operation with minimal risk of failure. However, currently limited understanding of blending effects on the structural dynamics of blisks challenges the rational determination of blend limits, i.e. the maximum allowable blend size, location and number in a damaged blisk. One of the principal reasons is that blisks are susceptible to high-level blade vibration due to inevitable blade mistuning. Blade mistuning arises primarily from the scatters of blade geometry profiles due to manufacturing tolerance. Moreover, blend repairs of the blades during maintenance can also induce relatively large geometry variances. The underlying fundamental issue is whether or not the blends will exacerbate the intrinsic geometric mistuning such that the blisk is subject to excessive vibration level and fails from high cycle fatigue. In fact, the accurate modelling and dynamic analysis of geometrically mistuned blisks has been a long-standing issue in both the academic and industrial communities.
In pursuit of an improved blade geometric mistuning evaluation capability, the BRAVO project focuses on development of the high-fidelity dynamic modeling, analysis and experimental verification techniques specifically for blisks with both intrinsic small geometry mistuning and blend repairs, based on the state-of-the-art 3D optical geometry scanning technology.
The BRAVO project aims to develop a comprehensive vibration evaluation tool for industrial designers to predict the risks and benefits of possible blend repairs within damaged blisks. A parallel goal of the MSCA Individual Fellowship is to enhance the fellow’s professional maturity and scientific independence as a research group leader.
Structural dynamics evaluations for the repaired blisks are of significant importance to ensure continued safe operation with minimal risk of failure. However, currently limited understanding of blending effects on the structural dynamics of blisks challenges the rational determination of blend limits, i.e. the maximum allowable blend size, location and number in a damaged blisk. One of the principal reasons is that blisks are susceptible to high-level blade vibration due to inevitable blade mistuning. Blade mistuning arises primarily from the scatters of blade geometry profiles due to manufacturing tolerance. Moreover, blend repairs of the blades during maintenance can also induce relatively large geometry variances. The underlying fundamental issue is whether or not the blends will exacerbate the intrinsic geometric mistuning such that the blisk is subject to excessive vibration level and fails from high cycle fatigue. In fact, the accurate modelling and dynamic analysis of geometrically mistuned blisks has been a long-standing issue in both the academic and industrial communities.
In pursuit of an improved blade geometric mistuning evaluation capability, the BRAVO project focuses on development of the high-fidelity dynamic modeling, analysis and experimental verification techniques specifically for blisks with both intrinsic small geometry mistuning and blend repairs, based on the state-of-the-art 3D optical geometry scanning technology.
The BRAVO project aims to develop a comprehensive vibration evaluation tool for industrial designers to predict the risks and benefits of possible blend repairs within damaged blisks. A parallel goal of the MSCA Individual Fellowship is to enhance the fellow’s professional maturity and scientific independence as a research group leader.
The project is organized into 3 technical work packages (WP1~3), a training and transfer of knowledge WP4 and a management/dissemination WP5.
WP1--Development of methodologies for high-fidelity As-Measured Modelling and reduction techniques specifically for blisks undergoing blend repairs, by employing the state-of-the-art 3D optical geometry scanning technology.
WP2--Development of methodologies for forced response analysis of blended blisks based on the As-Measured Model, along with experimental verification in the top-level stationary/spinning test facilities specifically developed for blade disk structures within AERMEC group.
WP3--Development of methodologies for predictive evaluation of the impact of blend geometry variance and number on the structural dynamics of the damaged blisk to be repaired.
WP4-- The training-through-research/transfer of knowledge activities include: 1) Training on Time-Frequency Analysis technique. 2) Training on the stationary traveling wave excitation system for the bench test in WP2. 3) Training on blade tip-timing technique for vibration measurement of spinning blisks in WP2. 4) Effective transfer of knowledge from the fellow in the form of regular research meetings, seminars, scientific publications and tutoring activities: a) the state-of-the-art as-measured blisk modelling technique based on advanced optical scanning technology; b) the classical blade mistuning identification methods relying on blisk modal tests and various reduced-order model techniques; (c) the novel blade mistuning identification method based on blade detuning tests; d) the original blisk model reduction technique “SMART” for geometrically mistuned blisk models. 5) Training on transferable skills for career needs by deeply involved in managing/coordinating the research work/financial part of the project, dealing with unexpected events, interacting with the AERMEC group and its international networks, co-supervising a MSc student’s thesis, etc.
WP5—Activities for effective dissemination and communication of the project results: 1) 4 high-quality peer-reviewed journal papers have been published and deposited in Zenodo with Green open access; 3 manuscripts are forthcoming for journal publication. 2) an oral presentation in the well-established international conference ASME Turbo Expo 2022, an invited seminar presentation in Dec, 2022 by the International Committee on Joint Mechanics and an oral presentation at a specialized symposium (Nov, 2021) have been delivered. 3) A data management plan has been delivered in the 6th month and open access to the research data, e.g. the finite element models, is provided under request. 4) News related to the project are provided in Twitter of POLITO and the online magazine PoliFlash; a web page dedicated to the successful story regarding the BRAVO project was published; a short video “MSCA Answers” was posted on Instagram POLITO. 5) The fellow has participated in the outreach events-- the European Researchers’ Night (Oct, 2022) and Biennale della Tecnologia (Nov, 2022) in order to increase the general public’s awareness of the project BRAVO.
WP1--Development of methodologies for high-fidelity As-Measured Modelling and reduction techniques specifically for blisks undergoing blend repairs, by employing the state-of-the-art 3D optical geometry scanning technology.
WP2--Development of methodologies for forced response analysis of blended blisks based on the As-Measured Model, along with experimental verification in the top-level stationary/spinning test facilities specifically developed for blade disk structures within AERMEC group.
WP3--Development of methodologies for predictive evaluation of the impact of blend geometry variance and number on the structural dynamics of the damaged blisk to be repaired.
WP4-- The training-through-research/transfer of knowledge activities include: 1) Training on Time-Frequency Analysis technique. 2) Training on the stationary traveling wave excitation system for the bench test in WP2. 3) Training on blade tip-timing technique for vibration measurement of spinning blisks in WP2. 4) Effective transfer of knowledge from the fellow in the form of regular research meetings, seminars, scientific publications and tutoring activities: a) the state-of-the-art as-measured blisk modelling technique based on advanced optical scanning technology; b) the classical blade mistuning identification methods relying on blisk modal tests and various reduced-order model techniques; (c) the novel blade mistuning identification method based on blade detuning tests; d) the original blisk model reduction technique “SMART” for geometrically mistuned blisk models. 5) Training on transferable skills for career needs by deeply involved in managing/coordinating the research work/financial part of the project, dealing with unexpected events, interacting with the AERMEC group and its international networks, co-supervising a MSc student’s thesis, etc.
WP5—Activities for effective dissemination and communication of the project results: 1) 4 high-quality peer-reviewed journal papers have been published and deposited in Zenodo with Green open access; 3 manuscripts are forthcoming for journal publication. 2) an oral presentation in the well-established international conference ASME Turbo Expo 2022, an invited seminar presentation in Dec, 2022 by the International Committee on Joint Mechanics and an oral presentation at a specialized symposium (Nov, 2021) have been delivered. 3) A data management plan has been delivered in the 6th month and open access to the research data, e.g. the finite element models, is provided under request. 4) News related to the project are provided in Twitter of POLITO and the online magazine PoliFlash; a web page dedicated to the successful story regarding the BRAVO project was published; a short video “MSCA Answers” was posted on Instagram POLITO. 5) The fellow has participated in the outreach events-- the European Researchers’ Night (Oct, 2022) and Biennale della Tecnologia (Nov, 2022) in order to increase the general public’s awareness of the project BRAVO.
The BRAVO project has pushed the frontiers of the cutting-edge blisk dynamic modelling and analysis technique based on the advanced 3D optical geometry measurement technology. Research outputs shed new light on an in-depth understanding of the technical challenges, along with capabilities and shortcomings involved with the construction and dynamic analysis of the high-fidelity geometrically mistuned blisk model. Intensive dynamic tests for the subject blisk structures have been conducted in the top-level stationary/spinning test rigs in the AERMEC group. Experimental evidences during this project corroborate that due to its accurate representation of the geometric variance, the high-fidelity geometrically mistuned blisk modelling and dynamic analysis technique can be considered as a viable and valuable tool for vibration evaluations of the integrally manufactured blisks under blend repair, well past the stage of “one-shot” applications.
The scientific advances emerging from BRAVO are not only be of interest to academia in Europe and throughout the world, but also in accordance with the practical needs of improving design and maintenance techniques in aeroengine industries. Since the first batch of advanced aeroengines employing blisks are going to undertake their first overhauls, repair contractors are urged to establish their repair philosophy of blisks. An accurate evaluation of the blend repair potentials will ensure their safe returns in operation, as well as reduced scrap rate and life cycle costs.
This project also well aligns with the digital twin philosophy across the aeroengine industry, that the digital reconstruction of the real aeroengine parts, detected by the precise geometry measurement data, enables to evaluate and monitor the products’ performance through the life cycle in an effective way. Hence, the high-quality research and innovation of BRAVO is supposed to potentially contribute to the competitiveness of European aeroengine industry.
The scientific advances emerging from BRAVO are not only be of interest to academia in Europe and throughout the world, but also in accordance with the practical needs of improving design and maintenance techniques in aeroengine industries. Since the first batch of advanced aeroengines employing blisks are going to undertake their first overhauls, repair contractors are urged to establish their repair philosophy of blisks. An accurate evaluation of the blend repair potentials will ensure their safe returns in operation, as well as reduced scrap rate and life cycle costs.
This project also well aligns with the digital twin philosophy across the aeroengine industry, that the digital reconstruction of the real aeroengine parts, detected by the precise geometry measurement data, enables to evaluate and monitor the products’ performance through the life cycle in an effective way. Hence, the high-quality research and innovation of BRAVO is supposed to potentially contribute to the competitiveness of European aeroengine industry.