Periodic Reporting for period 2 - VibSEA (SEA Applied to the Prediction of High Frequency Vibrations in Aircraft Engines)
Berichtszeitraum: 2020-10-01 bis 2022-12-31
VibSEA project is funded by the European Union’s H2020 through Clean Sky 2 Program under Grant Agreement #831893.
Designed to achieve reduction in fuel consumption, the Ultra-High Bypass and High Propulsive Efficiency Geared Turbofan engine incorporates evolutions likely to produce high frequency (HF) vibration excitations which propagate through the structure.
Numerical simulation is an efficient tool to control vibrations hence supporting the mechanical design. Where Finite Element (FE) based approaches show limitations due to computational hardware performances and HF dispersion management, Statistical Energy Analysis (SEA) stand as proven and effective method for this frequency range to predict the vibrational energy transfers across partitions – subsystems – of a structure.
Challenges of SEA modelling consist of the structure partitioning which usually requires expertise and the accuracy loss at lower frequencies where the high stiffness of parts or complexity of junctions counter the method initial assumptions. Those statements depend strongly on the studied structure, therefore the objective of the proposed project is to develop and demonstrate a SEA modelling process to predict the vibration propagated in a typical complex engine frame.
Comparisons of tests and calculations were made to validate and optimize SEA numerical models. Results show good consistency betewenn measured and predicted responses on the whole structure. The project outcomes are in line with the initial requirements thanks to an initial approach kept as general as possible, in order to remain open to various situation needs.
Designed to achieve reduction in fuel consumption, the Ultra-High Bypass and High Propulsive Efficiency Geared Turbofan engine incorporates evolutions likely to produce high frequency (HF) vibration excitations which propagate through the structure.
Numerical simulation is an efficient tool to control vibrations hence supporting the mechanical design. Where Finite Element (FE) based approaches show limitations due to computational hardware performances and HF dispersion management, Statistical Energy Analysis (SEA) stand as proven and effective method for this frequency range to predict the vibrational energy transfers across partitions – subsystems – of a structure.
Challenges of SEA modelling consist of the structure partitioning which usually requires expertise and the accuracy loss at lower frequencies where the high stiffness of parts or complexity of junctions counter the method initial assumptions. Those statements depend strongly on the studied structure, therefore the objective of the proposed project is to develop and demonstrate a SEA modelling process to predict the vibration propagated in a typical complex engine frame.
Comparisons of tests and calculations were made to validate and optimize SEA numerical models. Results show good consistency betewenn measured and predicted responses on the whole structure. The project outcomes are in line with the initial requirements thanks to an initial approach kept as general as possible, in order to remain open to various situation needs.
Tasks : 04/19 - 12/22
Within WP1, the State of the Art has been written. It aims at introducing the principle, history and main references of SEA and Hybrid FE SEA as prediction methods to evaluate the high frequency range of structural vibrations. A third version is being reviewed to be sent to SAFRAN.
Within WP5, modelling process has been achieved. A global FE Model has been developed and fragmented into individual substructures. These FE based substructures were analysed to support the SEA Subsystems and coupling qualification. Complex components such as OGV and arms blades were analysed with specific focus.
Four different SEA models, one hybrid FE-SEA model and one FE model were built. SEA Models have different levels of complexity and to analyse the level of details needed to get acceptable results.
Within WP2, Test Matrices of the experimental approaches have been detailed. They include the theoretical and practical basics to apply these methods.
Within WP3, the mechanical function of the test bench has been developed. It permits limiting the interaction between the test frame and the bench and defining two different boundary conditions that will be studied.
Within WP4, an optical detection method has been designed and developed to reduce the time measurement and to get more accurate results.
Within WP6, several test campaigns were carried out. Two campaigns were achieved with two boundary conditions using laser vibrometers and a shaker. Full matrices were built by exciting each one of the 16 subsystems and getting the responses of all subsystems. Another shorter test campaign was carried out by exciting each subsystem with an impact hammer and by measuring the responses of this subsystem.
Within WP7, a benchmark was made between numerical models to evaluate the accurate level of results according to SAFRAN test case. Moreover, a benchmark was made among three methods to get the best Damping Loss Factors of subsystems. A generic set of damping values was established to permit SAFRAN estimating damping on a new design.
Within WP8, the high frequency method developped in this project was transfered to SAFRAN. The final training took place between April 03th and April 06th 2023.
Results overview :
On the numerical simulation side, most of the challenge rely on the fact that the studied structure is rich in details and complexity. This had to be put in front of a numerical method, Statistical Energy Analysis, based on averaging approaches. Various modelling assumptions had to be stronger and required more attention than other types of structures. On the experimental side, the challenge was to build test benches which could provide large quantities of data within the project timeline. This has been done by combining laser vibrometers and optical detection algorithms. The approach and processes developed during the project are now meant to solve any similar problem.
Exploitation and dissemination :
VibSEA project is the opportunity for ESI to apply and consolidate dedicated techniques toward a systematic and predictive approach of SEA modelling, which is often considered as too complex and requiring much expertise. Thus, the proposition from ESI contribution is to be able to offer tools to the industry that rationalize the SEA Modelling approach, in particular:
FE modelling best practices in support of SEA model qualification
Automatization of SEA qualification by development of dedicated functions
Automatization of Damping Loss Factor extraction from measurement fully integrated in a mature software environment (VA One)
VibSEA project will permit CETIM to develop and to improve post processing tools for the SEA experimental DATA. CETIM will be able to:
Post treat the SEA key parameters for a defined complex system
To measure the kinetic energy and the injected power on some subsystems with vibrometer lasers and piezoelectric shaker.
Within WP1, the State of the Art has been written. It aims at introducing the principle, history and main references of SEA and Hybrid FE SEA as prediction methods to evaluate the high frequency range of structural vibrations. A third version is being reviewed to be sent to SAFRAN.
Within WP5, modelling process has been achieved. A global FE Model has been developed and fragmented into individual substructures. These FE based substructures were analysed to support the SEA Subsystems and coupling qualification. Complex components such as OGV and arms blades were analysed with specific focus.
Four different SEA models, one hybrid FE-SEA model and one FE model were built. SEA Models have different levels of complexity and to analyse the level of details needed to get acceptable results.
Within WP2, Test Matrices of the experimental approaches have been detailed. They include the theoretical and practical basics to apply these methods.
Within WP3, the mechanical function of the test bench has been developed. It permits limiting the interaction between the test frame and the bench and defining two different boundary conditions that will be studied.
Within WP4, an optical detection method has been designed and developed to reduce the time measurement and to get more accurate results.
Within WP6, several test campaigns were carried out. Two campaigns were achieved with two boundary conditions using laser vibrometers and a shaker. Full matrices were built by exciting each one of the 16 subsystems and getting the responses of all subsystems. Another shorter test campaign was carried out by exciting each subsystem with an impact hammer and by measuring the responses of this subsystem.
Within WP7, a benchmark was made between numerical models to evaluate the accurate level of results according to SAFRAN test case. Moreover, a benchmark was made among three methods to get the best Damping Loss Factors of subsystems. A generic set of damping values was established to permit SAFRAN estimating damping on a new design.
Within WP8, the high frequency method developped in this project was transfered to SAFRAN. The final training took place between April 03th and April 06th 2023.
Results overview :
On the numerical simulation side, most of the challenge rely on the fact that the studied structure is rich in details and complexity. This had to be put in front of a numerical method, Statistical Energy Analysis, based on averaging approaches. Various modelling assumptions had to be stronger and required more attention than other types of structures. On the experimental side, the challenge was to build test benches which could provide large quantities of data within the project timeline. This has been done by combining laser vibrometers and optical detection algorithms. The approach and processes developed during the project are now meant to solve any similar problem.
Exploitation and dissemination :
VibSEA project is the opportunity for ESI to apply and consolidate dedicated techniques toward a systematic and predictive approach of SEA modelling, which is often considered as too complex and requiring much expertise. Thus, the proposition from ESI contribution is to be able to offer tools to the industry that rationalize the SEA Modelling approach, in particular:
FE modelling best practices in support of SEA model qualification
Automatization of SEA qualification by development of dedicated functions
Automatization of Damping Loss Factor extraction from measurement fully integrated in a mature software environment (VA One)
VibSEA project will permit CETIM to develop and to improve post processing tools for the SEA experimental DATA. CETIM will be able to:
Post treat the SEA key parameters for a defined complex system
To measure the kinetic energy and the injected power on some subsystems with vibrometer lasers and piezoelectric shaker.
Beyond the state of the art, the project's goals are to extend the SEA methodology to a complex engine frame. The expected results until the end of the project are to be able to provide sufficiently accurate SEA models that can be used and updated with experimental data.
The project will permit to develop and to improve post processing tools for the virtual and experimental SEA. Consortium members will be able to propose extended and improved SEA technical services to customers in aeronautic but also to other markets such as automotive, off-road vehicles, energy fields and railway.
Technical advances made is this project will be included in technical training courses given by CETIM. Contactless velocity measurements and piezzo-electric shaker will be presented in these courses to provide efficient way of measuring structure vibration for aeronautic , automotive, off-road vehicles and railway markets.
The project will permit to develop and to improve post processing tools for the virtual and experimental SEA. Consortium members will be able to propose extended and improved SEA technical services to customers in aeronautic but also to other markets such as automotive, off-road vehicles, energy fields and railway.
Technical advances made is this project will be included in technical training courses given by CETIM. Contactless velocity measurements and piezzo-electric shaker will be presented in these courses to provide efficient way of measuring structure vibration for aeronautic , automotive, off-road vehicles and railway markets.