Investigation of Boundary Layer Ingestion for Civil Transport Aircraft Engine Installation
Creators: name:  J. GODARD 
name:   R. BARRIER 
name:   P. MOLTON 
name:   J. DAVID 
Publisher: name: Proceedings of  the 9th European Conference for Aerospace Sciences. Lille, France, 27 June - 1 July, 2022
Year: 2022
Subjects: FLIGHT PHYSICS
COMPUTATIONAL AERODYNAMICS
EXPERIMENTAL AERODYNAMICS

description: Modern turbofan engines are characterized by high by-pass ratio and high diameters, to reduce their fuel consumption and their emissions. The integration of big engines on civil transport aircraft can be challenging but can also be an opportunity to introduce new technologies such as Boundary Layer Ingestion (BLI). This technology consists in the ingestion of a portion of the viscous layers developing on the airframe by the engine intake. It presents the advantage of increasing the engine propulsive efficiency as the flow is naturally decelerated upstream of the fan face and the exhaust velocity is increased. On the other side, the flow ingested by the intake can present important distortions that can be a drawback for the aerodynamics and aeroelastic performance of the fan blades. ONERA, with the support of French DGAC agency, has set-up a project to develop its knowledge and competencies on this topic. The duration of the project is 5 years (2019 2023). Four scientific challenges of interest have been identified and studied: Quantification of aerodynamic performance of airplanes equipped with BLI engine installations; Capability to predict surge margin for the engine fan, in particular with characteristic BLI distortions; Capability to predict the characteristics of the flow in the engine intake, in particular distortion due to BLI; Capability to predict the aeroelastic behaviour of the fan blades, in case of an upstream flow presenting distortion. Both challenges are investigated using numerical and experimental activities, and for some of them through theoretical developments. For the quantification of aerodynamic performance, a theoretical work on the so-called far-field exergy balance is done and then introduced in the ONERA FFX software, evaluating the performance by analysis of CFD flow solutions. In parallel, different wind-tunnel models are defined numerically then manufactured for tests in the ONERA S1MA wind-tunnel. Conclusions are drawn on the gains due to BLI from numerical/experiments comparisons. The prediction of surge margin is investigated with experiments performed in the CME2 compressor bench of LMFL with different flow distortion generators. Unsteady URANS CFD computations are done on this geometry and for the test conditions. It is possible to conclude on the capabilities of ONERA software to predict the phenomenon from the analysis of both data. Tests are performed in the ONERA S3Ch wind-tunnel with different intakes ingesting a boundary layer to investigate the flow distortion in intakes with BLI. The measurements, in particular in the fan plane, are compared to CFD RANS computations to assess the capabilities of different numerical models, such as turbulence models, to predict distortion in intakes in conditions with BLI. Tests are executed in the ECL bench of LMFA to investigate the aeroelastic behaviour of a fan in case of an upstream flow with distortion. Aeroelastic computations are also performed on this configuration to conclude on the capabilities of ONERA software to predict these phenomena. The paper will present the structure and objectives of the project and some activities already performed. The project is not completed but first experimental and numerical results are already available and will allow to draw some preliminary conclusions.