Non-Intrusive Flow distortion measurements within a Turbofan Intake

Project Information

NIFTI

Grant agreement ID: 864911

DOI

10.3030/864911

Project closed

EC signature date 1 October 2019

Start date 1 January 2020

End date 31 October 2023

Funded under

• SOCIETAL CHALLENGES - Smart, Green And Integrated Transport

Total cost

€ 2 336 394,75

EU contribution

€ 2 250 000,00

Coordinated by

STICHTING DUITS-NEDERLANDSE WINDTUNNELS
Netherlands

Periodic Reporting for period 2 - NIFTI (Non-Intrusive Flow distortion measurements within a Turbofan Intake)

Reporting period: 2021-07-01 to 2023-10-31

Summary of the context and overall objectives of the project

Performance and environmental targets drive the design of next generation aircraft architectures towards closer integration between the propulsion system and the airframe. These architectures are likely to feature concepts with ultra-high bypass ratios (UHBR) where a short and slim intake design will be necessary to compensate for the drag and weight penalties of the increased diameter fan. Although such aircraft configurations may meet future performance targets, short intakes can cause high levels of unsteady flow distortion, especially under cross-wind operation during aircraft take-off. Such distortions can adversely affect the engine’s performance, operability and fan aerodynamic and mechanical compatibility. It is important to understand the intake flow characteristics of these novel intake concepts early in the design cycle, to reduce development risks, timescales and cost.
Current practices for engine testing rely on the use of intrusive measurements upstream of the fan to quantify the flow distortion. The emerging need for development of advanced design metrics for distortion tolerant aero-engines is hampered by the low spatial and temporal resolution of the current methods. Additionally, the intrusive nature of these methods is detrimental in short intake configurations where the fan and intake are tightly coupled.
Non-intrusive optical measurement techniques such as Particle Image Velocimetry (PIV) have proven their potential in wind tunnel testing over the past decades. The application of PIV to measurements of flow distortion near fan face of a turbofan is highly challenging. Both optical access and surface reflections hamper the application of PIV. Furthermore, PIV involves complex setups and calibration requirements which make them uneconomical solutions for large industrial scale test environments such as the DNW Large Low-Speed Facility (LLF). Thus, the NIFTI consortium has come together to define the following technical objectives:

Objective #1: Demonstrate a non-intrusive PIV technique to measure the velocity field upstream of the fan of an UHBR inlet in a large industrial wind tunnel at representative operating conditions
Objective #2: Demonstrate a highly flexible multi-camera PIV implementation in a representative industrial test environment to cover a wide range of inlet incidence angles in a time efficient way.
Objective #3: Develop advanced data processing methods to generate dynamic distortion metrics that will aid the development of design rules for closely integrated propulsion systems.
Objective #4: Develop advanced numerical methods to enable the aerodynamic and aero mechanical characterisation of the fan across the operating range when coupled with a short intake.

At project end, all project objectives have successfully been achieved by demonstrating the novel measurement technology in the DNW-LLF on a scale model of a UHBR inlet and validating the numerical methods to the acquired experimental data set.

Work performed from the beginning of the project to the end of the period covered by the report and main results achieved so far

After initial de-risking in work package (WP) 2, a multi-camera approach based on conventional PIV was selected. A fully automated system with remote control of the camera focus, Scheimpflug angle and axis has been developed in WP3. The system allows calibration of multiple configurations in a single pass and recall of stored configurations during testing for increased productivity.
To validate the NIFTI PIV and processing innovations, a phased experimental approach was used in WP4. Moving from laboratory scale system development, wind tunnel pre-testing at small scale, to a final verification wind tunnel test in the industrial DNW-LLF.
In parallel, novel data reduction and post-processing strategies were explored in WP5. Advanced PIV processing options such image background removal and pressure reconstruction from PIV velocity fields were refined for the application within the inlet. A comprehensive library was created to analyse the inlet flow data collected during the various experimental and computational campaigns. To support the development of post-processing techniques and guide the design of the wind tunnel tests, advanced CFD models of both the aspirated and fan powered wind tunnel geometries were developed.

The work performed has resulted in an innovative new flexible geometry PIV system, that offers many possibilities for future exploitation in testing environments requiring high productivity. The system has been employed to generate a unique experimental dataset of fan-coupled intake aerodynamics at off-design conditions. This has resulted in new insights into the aerodynamics of short inlets which allows many paths for further dissemination. Additionally, NIFTI has resulted in improved processing techniques, that allow reduction of complex flow data into meaningful inlet metrics that define the unsteady inlet flow distortions. Finally, significant advancements in the development of numerical tools for inlet and fan-inlet simulations have been achieved. Together with a unique experimental validation data set, these will result in further advancements beyond the project lifetime that the consortium plans to exploit and disseminate.

Progress beyond the state of the art and expected potential impact (including the socio-economic impact and the wider societal implications of the project so far)

NIFTI aims to develop non-intrusive measurement and numerical techniques as enabler of UHBR technology. The NIFTI PIV innovations will open up new possibilities and measurements solutions. Measuring a richer dataset in less time will support the ACARE goals for more efficient, cost-effective testing and upgrading physical facilities to and beyond state-of-the-art. Apart from providing significant benefits to the aviation sector, exploitation of these NIFTI outcomes will also have synergies with other transport modes such as the European automotive industry. The development and validation of unsteady numerical modelling of unconventional propulsion systems is vital for supporting the backbone of any future aircraft and propulsion development as it delivers richer, more accurate aerodynamic characterization.
Within the NIFTI project, development of new PIV techniques has taken a huge leap. Both the camera adjustment solution and developed fibre optics laser sheet delivery are innovations that will lead to new products and applications within and well outside the scope of the project. The developed PIV innovations have been validated in an industrial relevant environment achieving the target maturity of TRL5 set out at project start. The experimental and numerical datasets that have been acquired by the project have offered and will continue to offer a unique opportunity to validate the numerical models currently developed within the project. This improved understanding will contribute to full maturity of simulation techniques for novel propulsion concept.
The excellent cooperation of major academic and industrial stakeholders within the project guarantees the future application of the experience gained in the project. The project partners are fully committed to ensure effective exploitation of the numerical and experimental toolsets developed within NIFTI. The current project scope and direction closely matches the needs of industry and reflect the ambitions to progress beyond state of the art. As such the societal impact of NIFTI constitutes meaningful contributions to the roadmap of maintaining the leadership of the European aeronautics industry and reducing CO2 emissions by increased propulsion efficiency.

PIV setup for cross-wind at DNW-LLF

Inlet distortion at cross-wind conditions for a fan-coupled UHBR configuration