Abstract
In the context of an increased focus on fuel efficiency and environmental impact, turbofan engine developments continue towards larger bypass ratio engine designs, with Ultra-High Bypass Ratio (UHBR) engines becoming a likely power plant option for future commercial transport aircraft. These engines promise low specific fuel consumption at the engine level, but the resulting size of the nacelle poses challenges in terms of the installation on the airframe. Thus, their integration on an aircraft requires careful consideration of complex engine–airframe interactions impacting performance, aeroelastics and aeroacoustics on both the airframe and the engine sides. As a partner in the EU funded Clean Sky 2 project ASPIRE, the DLR Institute of Aerodynamics and Flow Technology is contributing to an investigation of numerical analysis approaches, which draws on a generic representative UHBR engine configuration specifically designed in the frame of the project. In the present paper, project results are discussed, which aimed at demonstrating the suitability and accuracy of an unsteady RANS-based engine modeling approach in the context of external aerodynamics focused CFD simulations with the DLR TAU-Code. For this high-fidelity approach with a geometrically fully modeled fan stage, an in-depth study on spatial and temporal resolution requirements was performed, and the results were compared with simpler methods using classical engine boundary conditions. The primary aim is to identify the capabilities and shortcomings of these modeling approaches, and to develop a best-practice for the uRANS simulations as well as determine the best application scenarios.
Highlights
Increasing environmental and economic requirements continue to drive turbofan engine development towards larger bypass ratio engine designs, with so-called Ultra-High Bypass Ratio (UHBR) engines a likely power plant choice for future commercial transport aircraft
In the frame of the EU funded Clean Sky 2 project ASPIRE, the DLR Institute of Aerodynamics and Flow Technology is contributing to an investigation of numerical analysis approaches for the aerodynamic, aeroacoustic and aeroelastic study of UHBR engines
For the uRANS simulations, a successfully established process chain used for previous CROR studies is adapted to the present UHBR turbofan simulations and a detailed numerical study, addressing both spatial and temporal resolution aspects, was performed
Summary
Increasing environmental and economic requirements continue to drive turbofan engine development towards larger bypass ratio engine designs, with so-called Ultra-High Bypass Ratio (UHBR) engines a likely power plant choice for future commercial transport aircraft. To better account for the fan aerodynamic interactions with the external aerodynamic flowfields around the aircraft for these increasingly more complex engine–airframe integration scenarios, the need to employ higher-fidelity fan modeling approaches than the classical engine boundary condition used in typical aerodynamic assessment of the entire configuration has been a growing focus in research projects and industrial applications. To understand the best modeling approaches for the engine fan module available in the DLR-developed TAU-Code, in particular when studying some of these challenging airframe aerodynamic topics, a comparison of a classical engine boundary condition and a high-fidelity rotating fan unsteady approach is being done based on a generic isolated UHBR engine configuration. With concurrent studies looking into the use of actuator disc and body force models, the overall aim of this and future work is to identify the capabilities and short-comings of each model, develop a best-practice approach in each case and determine the best application scenarios
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