Off-Design Installed Nacelles

Informations projet

ODIN

N° de convention de subvention: 101007598

DOI

10.3030/101007598

Projet clôturé

Date de signature de la CE 12 Janvier 2021

Date de début 1 Avril 2021

Date de fin 31 Decembre 2023

Financé au titre de

• SOCIETAL CHALLENGES - Smart, Green And Integrated Transport

Coût total

€ 3 267 561,25

Contribution de l’UE

€ 3 267 561,25

Coordonné par

CRANFIELD UNIVERSITY
United Kingdom

Periodic Reporting for period 2 - ODIN (Off-Design Installed Nacelles)

Période du rapport: 2022-10-01 au 2023-12-31

Résumé du contexte et des objectifs généraux du projet

To secure European global leadership in aviation, while also responding to societal needs, the ‘FlightPath 2050’ report identified targets of 75% fuel reduction, 65% perceived noise and 90% landing/take-off NOx emissions by 2050. Ultra High Bypass Ratio (UHBR) engines offer propulsive efficiency improvements and potential fuel burn reduction. However, UHBR engines typically have a larger diameter which can increase nacelle drag and weight and reduce fuel burn benefits. There is a need to develop the technologies to design compact nacelles and to integrate with an airframe to reduce fuel burn, meet noise requirements and operate at both design and off-design conditions.

The ODIN project objectives are as follows:
• Deliver aerodynamic design guidelines for UHBR novel nacelles which take into account off-design performance including external cowl separation at low-speed, high-lift conditions
• Deliver detailed understanding of installed UHBR nacelle off-design performance.
• Establish a highly instrumented, nacelle section rig to take innovative measurements of the flow physics of nacelles at off-design conditions.
• Quantify the effect of close-coupled integration with the wing on the exhaust system under low-speed, high-lift conditions when the exhaust is operating at low flow rates
• Evaluate design constraints imposed by noise levels at take-off, approach and cruise by combining the tools of computational aero-acoustics and experiments.
• Deliver guidance on the arrangements for acoustic sensor for a Flight Test Demonstrator for the validation of acoustic numerical simulations

The main objectives, both computational and experimental, relating to the nacelle aerodynamic design and exhaust suppression have been achieved. There have been notable advances around the computational and experimental aspects of the jet noise and jet flap interaction theme within ODIN. The wind tunnel tests identified conditions, and instrumentation, in which useful noise data could potentially be acquired on an aerodynamic test rig configuration. Unsteady simulations have been successfully carried out for an aircraft configuration and linked to the results from the transonic rig testing.

Travail effectué depuis le début du projet jusqu’à la fin de la période considérée dans le rapport et principaux résultats atteints jusqu’à présent

New optimisation methods for the design of novel compact nacelles have been developed. The optimisation takes into account cruise (Figure 1) as well as off-design operating conditions such as end of runway windmilling, and windmilling diversion at altitude. Optimisation strategies were developed which quantified the relative importance of off-design conditions and the impact on cruise drag. A range of compact and conventional nacelles were integrated with an intake, exhaust and pylon and installed on a representative airframe. Two airframe configurations were investigated: cruise and a take-off, high-lift configuration (Figure 2). The impact of the airframe integration on the nacelle aerodynamics was evaluated for cruise and both windmilling conditions (Figure 3). The effect of the windmilling design requirements on the cruise fuel burn was assessed for compact and conventional nacelle designs.

An innovative experimental rig configuration, which is sufficiently representative of the aerodynamics of 3-D nacelle under diversion and end-of-runway windmilling conditions was developed (Figure 4). A key consideration was to examine the onset of boundary layer separation from the nacelle (Figure 5) as this plays a key role in the nacelle design and optimisation strategies. The experimental data quantified the windmilling aerodynamic characteristics and enabled the assessment of industry standard, and more advanced, computational methods. The industry-type computational methods proved sufficiently able to discern the separation onset for the range of windmilling conditions and can be used for industrial design within identified uncertainty bounds.

An ODIN objective was to quantify the effect of the engine-aircraft integration on the exhaust system under off-design conditions. The experimental work was conducted in an industrial transonic wind tunnel and used a dual-stream exhaust rig with a representative swept wing with two configurations (0ᶱ and 20ᶱ flap deflections) (Figure 6). The experiment successfully quantified the impact of the wing on the exhaust flows. The simulations (Figure 7) provided excellent agreement with the wind tunnel data and validated the computational tools. These experimental and computational results were integrated with an engine cycle modelling method to quantify the overall impact on engine massflow under windmilling conditions.

The same dual-stream exhaust-swept wing rig configuration (Figure 6) was used to understand the feasibility of conducting jet noise measurements in an industrial wind tunnel without the complexity of wall treatments typically used for acoustic testing. The experimental data showed that the acoustic measurements on the wing and the flap is of value for both CFD validation and as a noise source term in an analytical model. The measurements identified the combinations of configuration, Mach number, nozzle pressure ratio, and frequency range for which the microphone measurements may be of potential use. Unsteady simulations showed that the computations could predict an increment in noise due to Jet Flap Interaction for the wind tunnel configuration. The same computational methodology was successfully used to assess the acoustics of a transonic transport aircraft in cruise and high-lift take-off configurations (Figure 8). These results have provided guidance on instrumentation positioning for a flying demonstrator aircraft.

ODIN achievements were disseminated, to date, through 13 conference papers and 3 peer-reviewed journal papers. A dedicated website was established to disseminate information about the project (www.odin-project.info). A technical symposium was held in November 2023 with participants from industry and academia. Some of the new methods and outcomes will form the basis of future post graduate MSc/PhD teaching.

Progrès au-delà de l’état des connaissances et impact potentiel prévu (y compris l’impact socio-économique et les conséquences sociétales plus larges du projet jusqu’à présent)

Within ODIN there have been advances beyond the state of the art in the following aspects:
• Development of new aerodynamic design and optimisation strategies for aero-engine nacelles that encompass cruise and off-design conditions
• Development of a new experimental rig to provide representative flow fields to investigate boundary layer separation under windmilling conditions
• Identification of the important flow field mechanisms for nacelles under off-design conditions, validation of computational methods and guidance for industrial design practices
• Quantification of the effect of a wing on the separate jet exhaust system flow at off-design conditions. Successful validation of the computational methods to predict the exhaust/wing interaction effects and integration of the results with a simulation method to determine the overall impact on the engine.
• Demonstration of jet-flap interaction acoustic measurements in an industrial wind tunnel in the absence of special acoustic wall treatments. Identification of the regions and conditions under which potentially useful data could be acquired.

Overall, the results from ODIN will support the design and performance of future close-coupled UHBR turbofan engines, particularly focusing on the unexplored off-design flight regimes, and thereby contribute to the wider aim of reduced emissions and the continued success of the European aviation sector.

Figure 6 – Wind tunnel model of the dual stream exhaust system and swept wing

Figure 4 – Photograph of rig installed in wind tunnel

Figure 3 – Nacelle aerodynamic under high lift, off-design conditions

Figure 7 – Examp RANS CFD flow-field prediction for DSJP rig operating at EOR windmilling conditions

Figure 2 – Nacelle integrated with pylon and exhaust and installed on the airframe

Figure 5 – Wind tunnel flow visualisation of the nacelle flow field

Figure 1 – 3D nacelle aerodynamics at mid-cruise condition

Figure 8 – Predicted unsteady flow field disturbances for the engine/airframe