ENGINE-AIRFRAME INTEGRATION STUDIES FOR FUTURE EFFICIENT PROPULSION SYSTEMS

Aviation is a key part in the complex web of global trade, political, cultural and personal exchanges and the broadening of horizons. Travel & aviation industries were hard-hit by the pandemic, but well on the way to return to pre-2020 growth rates. Increased environmental and societal pressures call for challenging reductions in carbon emissions. Propulsion technology will be core part of technology answer. Several promising engine technologies under study: UHBR turbofans (with geared fans), Open Rotor/Fan engines, Propellers, Distributed (propeller) propulsion, Boundary Layer Ingesting (BLI) engines. Mostly clear propulsive efficiency advantages at engine level. The challenge (aerodynamics and beyond) is the integration of these propulsion technologies with the airframe

Aerodynamic Analysis of a Transport Aircraft with a Boundary Layer Ingesting Aft-Propulsor at Cruise Flight Conditions

The implementation of advanced propulsion systems to ensure aviation meets the increasingly stringent environmental and economic pressures is a key building block in the development of future transport aircraft. A promising technology is the utilization of boundary layer ingesting (BLI) propulsion concepts, which are seen to offer an improvement of the engine propulsive efficiency in tandem with a reduction of the overall aircraft wake dissipation losses. In a collaborative study between the DLR Institute of Aerodynamics and Flow Technology, the DLR Institute of Propulsion Technology and industrial partners, a comprehensive study of the potential of implementing BLI concepts for future single-aisle short-to-medium range transport aircraft has been conducted. The present paper presents the result of an overall aircraft aerodynamic study, in which an aft BLI propulsor, specifically designed for this particular application, is investigated in its installation on the tail of a single aisle aircraft configuration at cruise flight conditions. A detailed aerodynamic analysis is presented, with a focus on comparing the results achievable through various BLI engine modeling approaches, which include the use of a classical engine boundary condition, a body force model as well as a full representation of the fan and OGV stage in a uRANS simulation approach. In addition to the study of the mutual aerodynamic interactions between the airframe and propulsor, some key aspects of the highest fidelity uRANS simulation approach are also discussed

Auswirkung von Grenzschichteinsaugung auf Triebwerkfans: Aerodynamik, Aeroelastik, Strukturmechanik und Akustik - Übersicht über das Projekt AGATA3S.

Bei der Integration moderner Triebwerke in zukünftige Flugzeugkonzepte entsteht insbesondere die Anforderung, die Auswirkungen einer ungleichförmigen Anströmung auf den Fan bewerten zu können. Eingesaugte Grenzschichten und Störungen in der Zuströmung wirken sich in einer verminderten aerodynamischen Performance, verstärkten strömungsinduzierten Schaufelschwingungen und der Anregung zusätzlicher Lärmquellen am Fan aus. Im Projekt AGATA3S wird das Verständnis über die zugrundeliegenden physikalischen Mechanismen vertieft sowie die Abhängigkeiten von den charakteristischen Größen der ins Triebwerk einlaufenden Strömung erarbeitet. Hierzu werden realistische Testfälle durch Flugzeugsimulationen abgeleitet und als Vorgaben für umfangreiche multidisziplinäre Messungen an einem realistischen Triebwerksfanmodell genutzt. Zusätzliche Prinzipexperimente und weiterentwickelte Mess-, Analyse- und Vorhersageverfahren unterstützen die Interpretation und Bewertung der Effekte. Abschließendes Ziel ist die Erfassung der Zusammenhänge zwischen der Außenaerodynamik des Flugzeugs und allen am Fan verursachten Effekten, um die Vor- und Nachteile der Grenzschichteinsaugung fachübergreifend für das gewählte Flugzeugkonzept zu bewerten. Der vorliegende Beitrag gibt einen Überblick über die Konzeption des Projekts, die entwickelten numerischen Testfälle und Experimente sowie stellt exemplarisch Ergebnisse vor

Current advancements of numerical methods and experimental means for the integration of future propulsion systems.

To integrate advanced propulsion systems and to assess and verify the related benefit (e.g. fuel burn, noise) suitable design, evaluation and measurement tools are required. For that reason, the so-called Cross-Capability-Demonstrator (XDC) has been set up as one major activity of the Large Passenger Aircraft (LPA) Platform 1 of the Clean Sky 2 initiative. The XDC is intended to demonstrate high-fidelity CFD-tools, further developed prediction tools for noise and aero-elastics as well as advanced testing tools for measuring e.g. the flow field, the deformation and the acoustics. The article will provide an update on activities within the XDC and presents some examples of recent accomplishments related to this demonstrator

CFD Validation of Unsteady Installed Propeller Flows Using the DLR TAU-Code

A series of unsteady CFD simulations have been conducted for a set of generic isolated- and installed-propeller configurations at low-speed flight conditions. The propeller geometry investigated is a four-bladed design typical of those used on modern regional turboprop aircraft. The computations were performed with the unstructured DLR TAU-code and the numerical results are compared with experimental data obtained in a wind tunnel test campaign conducted in the 1980s. The results of the unsteady computations agree well with the available propeller slipstream data and surface pressure distributions measured in the wind tunnel. Additionally, a detailed analysis and comparison of the forces acting on the wing and the propeller is performed

Unsteady CFD Simulations of Contra-Rotating Propeller Propulsion Systems

Having proven its utility for the simulation of single rotation propellers (SRP), the unstructured DLR TAU-Code has been applied to the unsteady simulation of isolated Contra Rotating Open Rotor (CROR) congurations. In order to demonstrate the codes applicability to the simulation of the complex aerodynamics of this type of propulsion system, a generic 8x8 pusher CROR powerplant was designed and uRANS computations at typical cruise conditions of M=0.75 and an altitude of 35,000ft were performed for the two angles of attack of 0 and 2 degrees. The results obtained allow for a detailed analysis of the complex aerodynamic interactions between the two rotors as well as an in-depth analysis of the blade and rotor forces

Unsteady Simulations of a Generic Isolated Tractor Contra-Rotating Propeller with the DLR TAU-Code

Having proven its utility for the simulation of single rotation propellers (SRP), the unstructured DLR TAU-Code has been applied to the unsteady simulation of isolated contra-rotating propeller (CRP) configurations. In order to demonstrate the codes applicability to the numerical analysis of this type of propulsion system, a generic tractor contra-rotating propeller configuration with eight blades per rotor was chosen and unsteady Euler and RANS simulations for a low-speed take-off case at angle of attack were performed. The results obtained allow for a detailed analysis of the complex aerodynamic interactions between the two rotors as well as an in-depth analysis of the blade and rotor forces

A uRANS-Based Hybrid CFD/CAA-Methodology for the Analysis of CROR Low-Speed Aerodynamic and Aeroacoustic Installation Effects

Contra-Rotating Open Rotor (CROR) engines promise a significant efficiency improvement over turbofan engines, which they derive from their ultra-high bypass ratio, made possible through the omission of a nacelle around the contra rotating co-axial rotors. However, the absence of the nacelle as well as the complex aerodynamic interactions between the two rotors also make meeting requirements of further reductions in noise emissions a significant technical challenge. In this thesis a flexible and robust simulation approach is developed, which, through the coupling of modern numerical tools for the aerodynamic and aeroacoustic analysis, allows for a detailed and precise multi-disciplinary analysis of CROR powered aircraft configurations. In addition to establishing an accurate and efficient simulation approach, the validation of this methodology is a central aspect of this work. It is demonstrated that this coupled simulation method delivers high accuracy in the prediction of the aerodynamic performance of isolated and aircraft-installed CROR engines and yields an accurate representation of the impact of installation effects on the noise emissions. The application of this approach to the analysis of successively more complex CROR engine-airframe installation scenarios furthermore demonstrates the valuable insights gained on the complex aerodynamic phenomena as well as key tonal noise source mechanisms on the basis of the simulation data