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Periodic Reporting for period 1 - AvAUNT (AdaptiVe Area nozzle for Ultra high bypass Nacelle Technology)


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...


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.

Work performed

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 in the first reporting period was focused on the (most time consuming) first stage: the design of rig and models. 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.

The main results achieved during the first reporting period consist of:

- Layout of the rig external lines and arrangement of the rig elements for the isolated and installed test configurations (Figure 1 – isolated configuration on wind-tunnel cart; Figure 2 – Installed configuration)

- Aerodynamic design of the rig internal air paths and flow conditioning pack to achieve the required flow uniformity at the model inflow plane (Figure 3 – Flow inside the rig; Figure 4 – Flow conditioning elements in rig internals)

- Datasets with predicted rig and models forces and moments at different engine and flight conditions from CFD simulations (Figure 5 – Mach number field from CFD solution)

- Detailed mechanical design of a safe and fit-for-purpose simulator (Figure 6 – Stress analysis of the balance component)

This design stage is a critical project stage, since its results constitute the necessary information for the implementation of all the subsequent project stages.

Final results

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 during this first periodic reporting period provide necessary information to develop the jet propulsion simulator for the transonic wind tunnel, 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.

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