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Validation of improved turbomachinery noise prediction models and development of novel design methods for fan stages with reduced broadband noise

Periodic Reporting for period 2 - TurboNoiseBB (Validation of improved turbomachinery noise prediction models and development of novel design methods for fan stages with reduced broadband noise)

Reporting period: 2018-03-01 to 2019-08-31

The technical objective of TurboNoiseBB is the development of concepts and enabling technologies aimed at reducing aeroengine noise at source. The addressed fan broadband noise (BBN) is a major aircraft noise challenge. TurboNoiseBB will enabe a major technical leap in providing the industry with low fan broadband noise concepts, based on an improved understanding of the broadband noise source mechanisms and validated broadband noise prediction methods.
The quantitative objective of TurboNoiseBB is to provide a 3 dB reduction at source on fan noise alone. In the process, TurboNoiseBB will advance the current noise technologies to higher TR-levels. The plan is to raise the TRL of innovative low noise OGV concepts from 2-3 up to 4-5 by performing large scale fan rig tests. High fidelity CFD/CAA computations will also advance the state-of-the-art CFD/CAA broadband noise design methods to a higher level that can be integrated within industry-exploitable tools.
All specifications for the tests, for the simulation work as well as for the data formats and the benchmarking have been issued and documented in collaboration between industrial
key players, research etsablishments and universities. The turbine related work made excellent progress: The industrial partners made use of the fan measurement data,
validated their codes and prepared a read-across to in-house turbine data in order to improve the turbine noise predictions codes.

The unpreceded BBN fan test was completely conducted and delivered an enormous amount of precious measurement data. All measurement data were documented and the
test conditions well described. The database was distributed to all partners, who needed them for their further activities in the project. The data analysis and appraisal was
completed. In the frame of this, an substantial amount of information has been analysed. The appraisal provided the certainty that the data sets are of maximum value,
quality and completeness. The acquired data sets will serve as reference data for fan BB noise and will establish a data-base, which did not exist before. It is
unique in the world in its richness, quality and depth of information.

The benchmark tests as well as a first stage of numerical predictions based on the reference fan geometry were already undertaken.
A lot of numerical results were achieved and could be compared with the experimental outcome of the elaborated fan tests.

A design of an aerodynamically optimized OGV is available for the second stage of the optimization process, being acoustically orientated both on tonal as well as on BBN.
The first stage of the optimization scheme has been accomplished.

The design phase for a novel, serrated, acoustically optimized OGV set has been completed.
The final design was chosen and the high-fidelity simulation work exhibits good progress.
The accurate modelling of a representative turbulence in an aero-engine fan stage is still a huge challenge in all current industry-based design methods. TurboNoiseBB will provide for the first time a step further into the integration of the higher accuracy CFD/CAA methods aforementioned into the multi-disciplinary fan-stage design. Comparisons with the experimental database, acquired using advanced aero-acoustics measurement techniques on the large scale UHBR fan stage (Anecom rig), will highlight the added value of the high fidelity CFD/CAA methods relative to industry RANS-based methods. Experimental results from parametric studies of fan/stator spacing, which shows significant difference in noise and flow behaviour will also be accurately captured through large scale testing at Anecom and will strengthen the quality of the database across the whole of the UHBR fan stage design space.
Industrial interaction noise prediction methods are based on a two-step process which first aims at modelling the incoming turbulence between the hub and the outer wall of the confined duct and then at reproducing the broadband response of the vanes using validated semi-analytical methods.
TurboNoiseBB will tackle fan broadband noise reduction for the first time using both state-of-the-art unsteady CFD/CAA methods as well as industrial methods. Integrated 3D design of stator vanes, which include design effects (thickness, sweep, lean, flow path optimisation) as well as noise reduction technologies (leading edge serrations, porous leading edge as identified in the outcome of FP7 FLOCON) will be thoroughly evaluated for aerodynamics and noise performance using state-of-the-art advanced CFD/CAA methods and state-of-the-art multi-disciplinary optimisation processes. A direct validation / calibration of the latter with the respect to the former will be performed to improve the turbulence and noise prediction accuracy of industry-exploitable methods for the specific case of a UHBR fan stage application.
TurboNoiseBB will subsequently assess the noise reduction obtained at the source for each stator vane design in flight conditions by Airbus through both Short Medium Range aircraft and Long Range aircraft platforms representative of future UHBR engine powered aircraft and taken from other projects (e.g. CleanSky2). These platforms include all engine and aircraft noise sources at all certification operating conditions and fulfill the final objective of assessing the noise reduction evaluated at the source in TurboNoiseBB to overall European noise regulations measured around airports.
Example of acoustic mode decomposition using advanced analysis techniques
Large eddy simulation: Vorticity iso-contours near the OGV blades
Investigated model fan geometry
Numerical simulation result: Entropy contours in the vicinity of the fan
ANECOM Fan rig in anechoic room