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ASPIRE Report Summary

Project ID: 681856
Funded under: H2020-EU.

Periodic Reporting for period 1 - ASPIRE (Aerodynamic and acouStic for high-by-Pass ratIo tuRbofan intEgration)

Reporting period: 2016-01-01 to 2016-12-31

Summary of the context and overall objectives of the project

The latest engine technologies, which are about to enter into service around 2025 via the new generation of engines of for new Aircraft (Short range or Long range), will offer a substantial specific fuel consumption (SFC) improvement of 15-17% compared with reference EIS 2000 technology. Those benefits have mainly been achieved by successively improving engine component and cycle efficiency, based on increased overall pressure ratio (OPR = 40) and by-pass ratio (BPR = 10 to 12). New light weight and reduction gearbox technologies are key enablers for the mentioned cycle improvements.
Increasing the by-pass ratio for turbofans further towards UHBR technology (BPR between 12 and 20) is expected to bring substantial additional SFC improvement comparable or even superior to the expected gain of CROR technologies. The use of innovative technologies such as new light weight materials, allows a shift to higher values of the optimal BPR value of HBR or UHBR engines which is driven by a compromise between propulsive efficiency, aerodynamic drag and weight.
However, the integration of UHBR engines under the wing is a challenge. Indeed, because of the size of these engines tremendous interactions occur with other aircraft components such as the nacelle, the pylon, the wing or the high-lift devices.
In this context, the overall objective of the ASPIRE project is to demonstrate to ability of existing numerical and experimental methods to accurately assess the aerodynamic and acoustic performance of such configurations thanks to a reliable modelling of fan/airframe physical interactions. In more details, the technical objectives are:
1. Design generic fan/OGV combinations representative of future UHBR engine;
2. Demonstrate the ability of CFD codes (NLR ENFLOW , ONERA elsA, DLR TAU, DLR TRACE) to predict aerodynamic performance of aircraft equipped with UHBR engines;
3. Demonstrate the ability of aero-acoustic methods to predict aeroacoustic performance of aircraft equipped with UHBR engines;
4. Identify and assess the experimental capabilities for the characterization of UHBR installation noise sources.

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

Based on the Top Level Aircraft Requirements provided by Airbus, DLR designed a generic fan/OGV combination representative of future UHBR engine (Bypass Ratio ≈ 16, Fan Pressure Ratio ≈ 1.32). The detailed geometries were provided to Airbus, ONERA and NLR as a basis for aerodynamic and aero-acoustic computations.
Based on this geometry and the other geometric elements provided by Airbus (isolated nacelle, Air inlet and Nozzle), first aerodynamic steady and unsteady URANS 360° computations were performed by NLR, DLR and ONERA to assess the impact of the fan/OGV combination on the airframe performance and vice et versa. These computations were completed by aero-acoustic analysis (see Figure 1).
Regarding the numerical aero-acoustic aspects, a common test-case has also been defined to compare existing time-domain propagation codes and validate the results with an experimental database issued from tests conducted at ONERA’s B2A test bench. This benchmark case was initiated in the frame of ONERA-NASA collaboration.
Furthermore, to compare the experimental results provided by several test rigs available in the consortium (owned by ONERA, DLR and TsAGI) for acoustic liner characterization, common reference liner samples have been defined. They will be tested; the results of impedance eduction model and measurements techniques will then be compared.

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)

Derivatives of the generic fan/OGV combination designed by DLR, will be defined by ONERA in order to assess the impact of laminar blades and heterogeneous OGV on fan tone noise generation.
On the generic configuration (fan, OGV, nacelle, air, inlet, nozzle), a detailed cross-comparison of CFD codes will be performed by ONERA, DLR and NLR. This will be achieved in order to define the best numerical strategies to accurately predict the impact of the fan on airframe performance and vise et versa. For this, unsteady URANS 360° computations will be performed in different conditions (cruise, take-off). This activity will bring a valuable insight in the potential of UHBR engine and provide guidelines to Airbus for the integration of UHBR engine. This will strongly impact the development of future aircraft equipped with UHBR engines.
For the modelling of fan/OGV tone and broadband fan noise, DES/LES simulation will performed by ONERA and the results will be compared to classical broadband noise modelling based on CAA computations. Moreover, LES computations will be performed by NLR to predict installed jet noise for aggressive UHBR integration. All these numerical activities should permit to identify and quantify possible acoustic penalties and risks that could appear in future UHBR engines featuring short inlets and heterogeneous OGVs.
The two test cases defined to compare the results of numerical propagation methods and the experimental results obtained in different acoustic liner test benches on a unique liner sample will provide very relevant results to improve existing numerical and experimental prediction methods.
Furthermore, original experimental acoustic approaches will be tested to measure the tremendous interactions between airframe and engine (e.g. jet-flap interaction noise, boundary layer refraction correction with rotating sources). These approaches will be strategic tools during future wind tunnel and flight tests of future aircraft equipped with UHBR engines.

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