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Supporting Understanding of Boundary Layer Ingesting Model Experiment

Periodic Reporting for period 2 - SUBLIME (Supporting Understanding of Boundary Layer Ingesting Model Experiment)

Reporting period: 2020-12-01 to 2021-11-30

The introduction of boundary layer ingesting propulsors integrated with the rear fuselage in large passenger aircraft poses new challenges regarding accurate assessments of the power savings potential over conventional podded installations.

The SUBLIME project will address this challenge, resulting in an experimental set-up to establish dependencies among the propulsor shape, fan inlet distortion pattern and the corresponding power savings.

The project will advance the state of the art in BLI studies by means of wind tunnel activities supported by high-fidelity CFD simulations to consistently predict full-scale behaviour of the aircraft architectures suitable for appropriate propulsor installation which minimizes inlet flow distortions and maximizes power saving.
The results of installed wind-tunnel tested aircraft + propulsors will be delivered in full compliance with the call. SUBLIME will provide methodologies, tools and facilities to the European aviation industry, therefore contributing to releasing the full potential of power saving of BLI engines.
The main Achievements include:

Seven deliverables achieved
Wind tunnel model design progressed to a successful Preliminary Design Review in December 2020.
Exploration of BLI 360 design space to identify beneficial region of design space to target in terms of intake mass flow & thrust split.
Identification of meshing philosophy for BLI fuselages.
Reference BLI configurations CFD assessment
3D BLI CFD DoE study almost completed
3D BLI 180 Parametric CFD study almost completed
Manufacturing review almost completed (april 2022)
Component testing completed for: pressure test of components connected to 250bar air system, calibration of load cell balance, calibration of boom strain gauges
Model has been re-costed based on current concept

The SUBLIME project has just reached the end of the first year so the impact on the wider society is limited. The project has allowed the beneficiaries maintain and increase their workforce, providing and maintaining high value employment throughout Europe. The COVID-19 pandemic has accelerated the wish for zero emission air travel and so methods for reducing power requirements are more relevant now that just 1 year ago when the project started. The COVID-19 pandemic has seen job losses in the aerospace and wider industry, the clean sky2 programme as a whole has helped to safe guard employment.

The SUBLIME projects progress beyond the state of the art:
a) Developing understanding of sub-scale to full-scale scaling, similarities and performance metrics for integrated BLI configurations.
b) Parametric DoE CFD design space exploration of high-speed BLI 360 configurations.
c) Modular High-speed wind tunnel model for investigating installed BLI configurations progressed through PDR.

Expected results beyond the state of the art:

#1: Advanced aircraft/propulsor coupling design for BLI
SUBLIME will advance knowledge of BLI coupled aero-propulsive model that will improve understanding of BLI propulsion systems. The project will consider a large search space for dealing with integrated BLI propulsion systems. Such an effort is possible only using appropriate experimental and numerical tools for design and analysis of candidate solutions including:
a) Wind tunnel tests on multiple BLI and reference configurations carried out over a wide range of Mach numbers up to transonic, with advanced measurement techniques.
b) Extrapolation of wind tunnel data to properly characterise BLI configurations at full scale conditions and geometric variation, using CFD/WTT data fusion approaches (VFM).

#2: Advanced measurement techniques
The ARA PIV system will be used to make conventional off surface flow measurements. The SUBLIME project will build on lessons learnt from the CS2 ANACO project and increase the robustness of a unique capability for non-intrusive measurements of boundary layers in an industrial wind tunnel. This data will allow understanding of the interference caused by total pressure rakes and provide high value rich dataset for increased understanding of the flow physics and CFD validation on BLI configurations.

#3: High-speed wind tunnel testing of BLI aircraft configurations
The SUBLIME project will provide opportunity to test integrated BLI aircraft configurations up to transonic cruise Mach. Transonic experimental tests of integrated powered BLI configurations have not previously been performed. This experimental database from the SUBLIME project is an ideal CFD validation source that will increase the confidence of future CFD based design studies. This will benefit the SUBLIME consortium and the company of the TM by learning from and exceed the knowledge gained from previous studies.

#4: Variable Fidelity Models (VFM)
The SUBLIME project will extend the application of Variable Fidelity Modelling (VFM) to integrated BLI configurations. The successful demonstration of VFM as a data fusion tool to merge CFD and WTT datasets, including powered BLI effects, has the potential to reap significant benefits downstream of this project. The ability to use relatively sparse WTT configurations to “correct” CFD (many configurations) is very powerful and represents strong innovation potential. Prospects are for reduced costs of aerodynamic data generation, including WTT, and reduced uncertainty (and hence risk) in using this approach.

#5: Realistic fan simulation in BLI propulsors
In SUBLIME, appropriate CFD modelling for simulation of fan effects and nacelle/fan interactions will be undertaken using source terms which replicate the presence of fan blading at an appropriate level of accuracy suitable for reliable installed predictions (i.e. BFM). This will eventually make it possible to derive fan maps under distorted flow, i.e. pressure ratio and efficiency vs. corrected mass flow from choking to actual surge line.

#6: Advanced Hybrid Momentum-energy Based Assessment Techniques
Hybrid method based on a complimentary combination of momentum and energy conservation will be used in SUBLIME and takes advantage of a multi-physics based approach, which will allow for application to both experimental and CFD investigations. It brings with it more opportunities to establish improved links between experiment and CFD, with more comprehensive evaluations of uncertainty analysis. The hybrid method enables greater insight into BLI physics and related flow mechanisms, which will be embellished by the combination of experimental and CFD datasets.
Technical Highlights