Closed Loop Flow Control for Aeroengines
Lead Research Organisation:
University of Oxford
Department Name: Engineering Science
Abstract
This project falls within the EPSRC Engineering research area.
The studentship is jointly offered by the University of Oxford and Rolls-Royce under the EPSRC iCase award scheme.
Performance and efficiency goals neccessitate that future aero-engine designs will have high bypass ratios with associated fan operability challenges, highly loaded compressors that may require active stability management, and turbines employing adaptable cooling systems to trade between fuel burn performance and life. These problems require some form of air modulation across varying time scales from seconds through to 100 microseconds, achieving which demands flow control schemes and devices that can be made reliable in the harsh environments present in aeroengines.
Promising research in plasma and piezo fluidic valves for flow control carried out at Osney Thermofluids Institute offers the opportunities for deployment of these devices in both hot and cold end gas turbine applications outlined above. Building on the previous research this project will investigate novel applications of plasma devices and piezo-fluidic valves to fan-intake active flow control (AFC). Unlike passive flow control, AFC methods by definition require energy input (for example blowing/suction, synthetic jets, plasma actuators), the benefits of which include greater control authority and suitability for closed loop feedback control. In addition, the lack of moving parts in fluidic valves/switches benefit the weight and reliability of active control systems.
Recent advancements in data-driven system identification and fluidic actuators have brought closed-loop AFC to the forefront of current research. Particular aims include suppression of large coherent turbulent structures and boundary layer separation, most often for the purpose of imporved efficiency. Modal decomposition methods, such as proper orthogonal decomposition (POD) and dynamic mode decomposition (DMD), can be used to extract dynamically relevant flow structures from a time series of flowfield data and are useful both for analysis and in constructing reduced-order models of flowfield evolution for use in control. Despite substantial advancements in these fields, real-world applications of closed-loop AFC are still few and far between.
Flow separation or other flow nonuniformities over an aeroengine intake during takeoff and landing conditions, caused by crosswinds, high angles of attack, interaction with suction induced ground vortices or existing turbulence in the air, impacts the stability and structure of the flow oncoming to the fan, potentially leading to blade stall and immediate loss of thrust control, as well as high cycle blade fatigue and shortened engine life. Adequate low-speed near-ground engine performance is typically ensured by modification of inlet geometry, and can therefore limit cruise performance. Active flow control offers the attractive prospect of decoupling inlet geometry and flow conditioning.
The aim of this project is to investigate the viability of active flow control to prevent separation on aero-engine intakes (whether on an intake lip or in an S-duct) and achieve a stable and uniform flow to the fan, improving engine safety, reliability and efficiency.
Currently, the technology readiness level (TRL) of active flow control for aero-engine inlet flow is approximately 1: basic principles and potential have been observed, but commercial realisation is still far away. It is hoped that this project will raise the TRL to 3: proof of concept.
This project will include:
Research in the application of established control theory for closed loop control of fluids
Application of modal decomposition methods to closed loop flow control
Validation of computational models for flow control by matching simulations to wind tunnel experiments
CFD and Wind tunnel experiments evaluating performance and practicalities of active flow control for aero-engine inlet application
The studentship is jointly offered by the University of Oxford and Rolls-Royce under the EPSRC iCase award scheme.
Performance and efficiency goals neccessitate that future aero-engine designs will have high bypass ratios with associated fan operability challenges, highly loaded compressors that may require active stability management, and turbines employing adaptable cooling systems to trade between fuel burn performance and life. These problems require some form of air modulation across varying time scales from seconds through to 100 microseconds, achieving which demands flow control schemes and devices that can be made reliable in the harsh environments present in aeroengines.
Promising research in plasma and piezo fluidic valves for flow control carried out at Osney Thermofluids Institute offers the opportunities for deployment of these devices in both hot and cold end gas turbine applications outlined above. Building on the previous research this project will investigate novel applications of plasma devices and piezo-fluidic valves to fan-intake active flow control (AFC). Unlike passive flow control, AFC methods by definition require energy input (for example blowing/suction, synthetic jets, plasma actuators), the benefits of which include greater control authority and suitability for closed loop feedback control. In addition, the lack of moving parts in fluidic valves/switches benefit the weight and reliability of active control systems.
Recent advancements in data-driven system identification and fluidic actuators have brought closed-loop AFC to the forefront of current research. Particular aims include suppression of large coherent turbulent structures and boundary layer separation, most often for the purpose of imporved efficiency. Modal decomposition methods, such as proper orthogonal decomposition (POD) and dynamic mode decomposition (DMD), can be used to extract dynamically relevant flow structures from a time series of flowfield data and are useful both for analysis and in constructing reduced-order models of flowfield evolution for use in control. Despite substantial advancements in these fields, real-world applications of closed-loop AFC are still few and far between.
Flow separation or other flow nonuniformities over an aeroengine intake during takeoff and landing conditions, caused by crosswinds, high angles of attack, interaction with suction induced ground vortices or existing turbulence in the air, impacts the stability and structure of the flow oncoming to the fan, potentially leading to blade stall and immediate loss of thrust control, as well as high cycle blade fatigue and shortened engine life. Adequate low-speed near-ground engine performance is typically ensured by modification of inlet geometry, and can therefore limit cruise performance. Active flow control offers the attractive prospect of decoupling inlet geometry and flow conditioning.
The aim of this project is to investigate the viability of active flow control to prevent separation on aero-engine intakes (whether on an intake lip or in an S-duct) and achieve a stable and uniform flow to the fan, improving engine safety, reliability and efficiency.
Currently, the technology readiness level (TRL) of active flow control for aero-engine inlet flow is approximately 1: basic principles and potential have been observed, but commercial realisation is still far away. It is hoped that this project will raise the TRL to 3: proof of concept.
This project will include:
Research in the application of established control theory for closed loop control of fluids
Application of modal decomposition methods to closed loop flow control
Validation of computational models for flow control by matching simulations to wind tunnel experiments
CFD and Wind tunnel experiments evaluating performance and practicalities of active flow control for aero-engine inlet application
People |
ORCID iD |
| Neil Ashton (Primary Supervisor) | |
| Owen Sinclair (Student) |
Studentship Projects
| Project Reference | Relationship | Related To | Start | End | Student Name |
|---|---|---|---|---|---|
| EP/T517653/1 | 01/10/2019 | 30/09/2025 | |||
| 2288569 | Studentship | EP/T517653/1 | 01/10/2019 | 30/09/2023 | Owen Sinclair |