Periodic Reporting for period 3 - ACONIT (Actuators for Surge Control in Gas Turbine)
Reporting period: 2022-09-01 to 2023-12-31
The objective of the ACONIT project is to design, manufacture and test actuators for flow control for an implantation in an aircraft engine. The actuators will fulfill aeronautics requirement in order to increase the Technology Readiness Level (TRL) in this domain. In particular, for the present proposal, one plans to focus on the extension of the stable operating range of axial compressor, allowing thus a reduction of the surge margin through postponing the stall onset. To do so, the first objective of the work is to improve the knowledge of the flow physics of an efficient flow control system by joint numerical and experimental analysis performed in a low speed, single stage axial compressor. The results of this analysis will be used to derive the fluidic specifications for a high TRL actuators and control system. These specifications will be the base for the design and manufacturing of amplified Piezo-electric actuator prototypes whose fluidic performance and operational performance in an environment with vibration and controlled level of temperature will be precisely evaluated before manufacturing final actuators that will be integrated in a full scale engine test facility. Their performance will be evaluated in terms of Surge Margin Improvement as well as in terms of energy balance between the induced consumption and the machine performance improvements. The consortium grouped for carrying out this project is composed of a SME (CTEC), two academic institutions
(Bundeswehr University Munich and Arts & Métiers) and a Research Center (ONERA). It groups skills ranging from internal flow analysis in turbomachineries, to flow control or actuators design, manufacturing and characterisations.
The consortium of the project is composed of : Ecole Nationale Supérieure des Arts et Métiers (ENSAM), Office National d'Etudes et de Recherches Aérospatiales (ONERA), Universität der Bundeswehr München (UniBw), Cedrat Tehnologies (CTEC).
The project is part of the overall CleanSky programme, which aims to reduce the impact of aviation by making it more sustainable. The ACONIT project seeks to improve the efficiency of aircraft engines to make them less polluting.
(Bundeswehr University Munich and Arts & Métiers) and a Research Center (ONERA). It groups skills ranging from internal flow analysis in turbomachineries, to flow control or actuators design, manufacturing and characterisations.
The consortium of the project is composed of : Ecole Nationale Supérieure des Arts et Métiers (ENSAM), Office National d'Etudes et de Recherches Aérospatiales (ONERA), Universität der Bundeswehr München (UniBw), Cedrat Tehnologies (CTEC).
The project is part of the overall CleanSky programme, which aims to reduce the impact of aviation by making it more sustainable. The ACONIT project seeks to improve the efficiency of aircraft engines to make them less polluting.
The ACONIT Project aimed at providing high TRL actuators for active flow control of axial compressor surge. The principal of such a control is based on actuators blowing high speed jet at the compressor casing.
The specifications of the actuators were based on an in-depth literature review and on an extensive study on a single stage compressor which included :
- A parametric study to determine the optimal parameters for an effective control strategy (both in terms of surge margin improvement and in terms of energy budget)
- A detailed experimental analysis of the flow based on Particle Image velocimetry in a blade channel and unsteady pressure measurements at the compressor casing).
- Numerical simulation which i/ helped to understand the physcis of the flow close to surge arising, with or without flow control. ii/ where used to determine the optimal methodology (in terms of turbulence modelling and meshing) to conduct simulations in such a complex configuration.
Based on these analysis, a prototype of actuator was designed and tested numerically and experimentally. This prototype was able to deliver a mass flow of 30g/s and to reach velocities up to 240 m/s in ambient conditions (whereas the fluid actuators existing in literature were blowing 2g/s maximum) and was also able to deliver a continuous or a pulsed jet.
The protype was then duplicated to produced a set of 17 actuators adapted to be installed on a complete aeronautical engine test bench.
The actuators where then successfully implemented on the engine with the control system fed by engine bleed air.
In terms of performance, on a single stage low speed compressor test bench, a very high SMI up to 140 % with a very high amplitude blowing and a moderate SMI (40 to 70%) with a positive energy balance. On the complete engine test bench the AFC allows to reached SMI of the order of 50% at 54 of the engine full speed.
A TRL 4 of the control system can be considered as achieved, even if, of course, many improvements can still be made (compactness for example and flow rate reached).
The specifications of the actuators were based on an in-depth literature review and on an extensive study on a single stage compressor which included :
- A parametric study to determine the optimal parameters for an effective control strategy (both in terms of surge margin improvement and in terms of energy budget)
- A detailed experimental analysis of the flow based on Particle Image velocimetry in a blade channel and unsteady pressure measurements at the compressor casing).
- Numerical simulation which i/ helped to understand the physcis of the flow close to surge arising, with or without flow control. ii/ where used to determine the optimal methodology (in terms of turbulence modelling and meshing) to conduct simulations in such a complex configuration.
Based on these analysis, a prototype of actuator was designed and tested numerically and experimentally. This prototype was able to deliver a mass flow of 30g/s and to reach velocities up to 240 m/s in ambient conditions (whereas the fluid actuators existing in literature were blowing 2g/s maximum) and was also able to deliver a continuous or a pulsed jet.
The protype was then duplicated to produced a set of 17 actuators adapted to be installed on a complete aeronautical engine test bench.
The actuators where then successfully implemented on the engine with the control system fed by engine bleed air.
In terms of performance, on a single stage low speed compressor test bench, a very high SMI up to 140 % with a very high amplitude blowing and a moderate SMI (40 to 70%) with a positive energy balance. On the complete engine test bench the AFC allows to reached SMI of the order of 50% at 54 of the engine full speed.
A TRL 4 of the control system can be considered as achieved, even if, of course, many improvements can still be made (compactness for example and flow rate reached).
Technological impacts
Successful development of an active flow control system which has proven to stand a high level of temperature and vibration typical of the ones that can be encountered in an aeronautical engine. The prototype developed is able to deliver a mass flow of 30g/s and to reach velocities up to 240 m/s in ambient conditions (wheras the fluid actuators existing in litterature were blowing 2g/s maximum)
Successful implementation of this system fed by engine bleed air (to be compared with usual research development using external devices). A TRL 4 can be considered as achieved, even if, of course, many improvements can still be made (compactness for example and flow rate reached). In terms of performance, on a single stage low speed compressor test bench, a very high SMI up to 140 % with a very high amplitude blowing and a moderate SMI (40 to 70%) with a positive energy balance. On the complete engine test bench, the AFC allows to reached SMI of the order of 50% at 54 of the engine full speed
Valuable knowledges and expertise were developed, in particular concerning design and integration of active flow control devices in a real engine, but also in the conduct of the test campaign itself. As initially planned, a strong emphasis was made on CFD, whose contribution was significant in the design process, leading to some precious guidelines for designing the actuators (in particular the injector) for future research in this area, saving valuable time
Scientific impacts
The experiments and the numerical simulation conducted on the single stage configuration have led to a better understanding of the physical mechanisms by which the jet interacts with the flow at the blade tip
Concerning the numerical strategy necessary to predict correctly the stall of an axial compressor with active flow control: several turbulence models and numerical methods have been tested and evaluated. Two different meshing strategies (Hybrid meshes and Chimera Techniques) have been investigated in order to take into account the actuators in a computational domain. They have been successfully applied and on the basis of the results obtained, some CFD guidelines have been proposed to efficiently simulate these kinds of phenomena. In particular, the Hybrid grid approach offers an efficient way to simulate turbomachinery flows with flow control; indeed, it combines the advantage of keeping structured grids for the blades (well adapted for blade flow simulation), and non-structured grids for the actuators (which are generally complex to mesh).
Successful development of an active flow control system which has proven to stand a high level of temperature and vibration typical of the ones that can be encountered in an aeronautical engine. The prototype developed is able to deliver a mass flow of 30g/s and to reach velocities up to 240 m/s in ambient conditions (wheras the fluid actuators existing in litterature were blowing 2g/s maximum)
Successful implementation of this system fed by engine bleed air (to be compared with usual research development using external devices). A TRL 4 can be considered as achieved, even if, of course, many improvements can still be made (compactness for example and flow rate reached). In terms of performance, on a single stage low speed compressor test bench, a very high SMI up to 140 % with a very high amplitude blowing and a moderate SMI (40 to 70%) with a positive energy balance. On the complete engine test bench, the AFC allows to reached SMI of the order of 50% at 54 of the engine full speed
Valuable knowledges and expertise were developed, in particular concerning design and integration of active flow control devices in a real engine, but also in the conduct of the test campaign itself. As initially planned, a strong emphasis was made on CFD, whose contribution was significant in the design process, leading to some precious guidelines for designing the actuators (in particular the injector) for future research in this area, saving valuable time
Scientific impacts
The experiments and the numerical simulation conducted on the single stage configuration have led to a better understanding of the physical mechanisms by which the jet interacts with the flow at the blade tip
Concerning the numerical strategy necessary to predict correctly the stall of an axial compressor with active flow control: several turbulence models and numerical methods have been tested and evaluated. Two different meshing strategies (Hybrid meshes and Chimera Techniques) have been investigated in order to take into account the actuators in a computational domain. They have been successfully applied and on the basis of the results obtained, some CFD guidelines have been proposed to efficiently simulate these kinds of phenomena. In particular, the Hybrid grid approach offers an efficient way to simulate turbomachinery flows with flow control; indeed, it combines the advantage of keeping structured grids for the blades (well adapted for blade flow simulation), and non-structured grids for the actuators (which are generally complex to mesh).