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AdaptiVe Area nozzle for Ultra high bypass Nacelle Technology

Periodic Reporting for period 2 - AvAUNT (AdaptiVe Area nozzle for Ultra high bypass Nacelle Technology)

Reporting period: 2018-10-01 to 2020-03-31

The AvAUNT project seeks to advance the state-of-the-art in the understanding of the aerodynamic interference challenges associated with the Ultra High Bypass Ratio (UHBR) nacelle with integrated Variable Area Nozzles (VAN) to Technology Readiness Level 4. The move towards higher bypass ratios can lead to significant reductions in emissions and noise; up to 10% propulsive efficiency enhancement and 2dB noise reductions from UHBR ~15 and above have been reported. However, by lowering fan pressure ratios, fan surge problems can emerge with increasingly larger variations in flight performance between sea-level and cruise. To overcome this, the VAN can provide the necessary increases in surge margin at low mass flow conditions at sea-level, but at the expense of additional system weight and complexity. While many of the potential benefits of the UHBR configuration have been substantiated for isolated nacelle configurations, there is limited understanding of the installation interference effects that will be induced at these very high/ultra high ratios, or how the incorporation of the VAN may affect the nature of these interference losses. In the current project, early stage candidate concepts for a nacelle with VAN technology will be studied through complementary experimental and computational simulation to ascertain the interference effects induced and to propose a verified modelling methodology which can be used in advance design studies. This will be used to inform best practice in the design of installed UHBR nacelles with VAN technology to support a move towards an integrated technology demonstrator within the Clean Sky 2 Joint Undertaking for late 2023.

The overall objectives of the project are:

1. Develop fundamental understanding of the impact of Variable Area Nozzles (VAN) on UHBR powerplant performance characteristics beyond the state of the art through integrated computational and experimental evaluation of candidate concepts.

2. Propose methods for the aerodynamic design and evaluation of VAN concepts which are suitable for development to Technology Readiness Level (TRL) 6 by the end of 2023, which can realise the innovation potential of the concept, drawing on industrial expertise in VAN design and manufacture through partner UTC Aerospace Systems.

3. Identify barriers to achieving sustainable performance benefits through exploration of installation effects (wing, mounting and high lift devices) of the candidate VAN configurations.

4. Establish best practice in VAN installation effects informed through experimental, computational and industrial experience, considering technological, logistical and commercial roadmaps.
In order to achieve the project objectives, it is necessary to progress through several project stages: Design of rig (simulator) and models (Variable Area Nozzles); Manufacturing of rig and models; Commissioning of the rig; Wind tunnel test and CFD of simulator with models; Analysis of the generated data.

The work performed from the beginning of the project to the end of period 2 was focused on four out of the five stages:

1.- Design of rig (simulator) and models (Nozzle concepts):

This involved tasks such as the performance mapping of the ARA transonic wind tunnel facility in order to carry out the rig sizing, the rig external and internal aerodynamics studies (mainly using CFD), the mechanical and structural design, and the layout of the instrumentation for data acquisition.

2.- Manufacturing and assembly of rig and models:

This has involved the manufacture of all rig and models parts and the installation of the instrumentation. The rig and the three nozzle concepts have been assembled and safety pressure tests performed and passed.
Inspections of the manufacturing parts and assemblies of rig, baseline nozzle and the wing simulator have been carried out and the results accepted.

3.- Commissioning of rig and models:

Initial stages of the rig commissioning activity have been carried out during the last reporting period. The effort has been focused on the calibration of a newly developed flow-through five-components balance.

4- Wind-tunnel test and CFD of simulator with models:

Agreement on meshing strategy for the baseline nozzle has been achieved. Numerical simulations of the baseline nozzle installed in the rig have been performed and analysed.

The main results achieved from the beginning of the project consist of:

- Design of rig and models
- Manufacturing and assembly of all rig and model components
- Inspection of manufactured parts and assemblies
- Phase 1 of balance calibration (calibration in component in isolation)
- CFD simulations of baseline nozzle installed in rig
AvAUNT will considerably enhance the knowledge base on the scope, origin, causes and aerodynamic performance effects of Variable Area Nozzles (VAN) installation in next generation Ultra High Bypass Ratio (UHBR) powerplants which are aimed at abating environmental noise while simultaneously achieving significant fuel burn reductions.

The results produced from the beginning of the project positions the consortium close to a stage where the jet propulsion simulator for the transonic wind tunnel can be commissioned. The simulator or rig is a fundamental tool to experimentally evaluate the designed VAN models and acquire knowledge beyond the state-of-the-art.

The AvAUNT project will also support the development of new aerodynamic methods for studying installation aerodynamic characteristics beyond the isolated UHBR nacelle configuration. This research will provide the basis for future innovation investment policies, elevating proposed UHBR with VAN technologies from TRL2 to TRL4 and beyond. The research also aims at furnishing recommendations on best practice in VAN design, and recommendations for future strategies for development of the concept through to final production.
Flow conditioning elements in rig internals
Isolated configuration on wind-tunnel cart
Example of high-fidelity CFD solution
Rig and baseline nozzle - Static test configuration
Mach number field from CFD solution
Phase 1 of new balance calibration
Installed configuration
High-fidelity mesh of baseline nozzle
Flow inside the rig
Stress analysis of the balance component