Periodic Reporting for period 2 - ANACO (Advance Nacelle Aerodynamic Optimisation)
Reporting period: 2020-05-01 to 2021-10-31
In 2001, the Advisory Council for Aviation Research and Innovation in Europe (ACARE) published the ‘Vision’ for 2020, setting challenging targets for reductions in aircraft emissions, stimulating activity in wide ranging technologies. Current powerplant development is contributing through increased engine bypass ratio, propulsive efficiency and operation at reduced specific thrust, a major factor in the design of next generation Ultra-High Bypass Ratio (UHBR) engines including Advance and Ultrafan®. Efficiency reductions arising from increased fan diameter, cowl size, weight and aerodynamic drag may be mitigated by multi-point, multi-objective optimisation (MOO) methods configured to minimise integrated mission drag.
The objectives of the ANACO project play an important role in this optimisation:
1. Design and develop short and slim nacelle designs for the UltraFan® type engine applying a novel philosophy of optimising nacelle drag across the mission conditions.
2. Apply the latest optimisation techniques in the multi-objective and multi-point design space to generate candidate geometries
3. Down-select optimum designs for experimental validation
4. Develop and expand existing experimental test techniques to assist in verification of the identified design optima
5. Design, manufacture and test a family of optimum geometries to prove the effectiveness of the new design philosophy
6. Measure the suitability of the proposed nacelle designs by simulation of the installed configurations - full-scale CFD investigation and wind tunnel (WT) test feasibility study
7. Validate design and computational methods for compact nacelle configurations using improved experimental data
8. Establish design guidelines for new nacelle configurations based on a synthesis of the computational and experimental data.
The objectives of the ANACO project play an important role in this optimisation:
1. Design and develop short and slim nacelle designs for the UltraFan® type engine applying a novel philosophy of optimising nacelle drag across the mission conditions.
2. Apply the latest optimisation techniques in the multi-objective and multi-point design space to generate candidate geometries
3. Down-select optimum designs for experimental validation
4. Develop and expand existing experimental test techniques to assist in verification of the identified design optima
5. Design, manufacture and test a family of optimum geometries to prove the effectiveness of the new design philosophy
6. Measure the suitability of the proposed nacelle designs by simulation of the installed configurations - full-scale CFD investigation and wind tunnel (WT) test feasibility study
7. Validate design and computational methods for compact nacelle configurations using improved experimental data
8. Establish design guidelines for new nacelle configurations based on a synthesis of the computational and experimental data.
Five technical work packages addressed the project objectives:
WP1: Multipoint design and optimisation of short and slim nacelles (CU lead)
WP2: Downselect of novel drag measurement enhancements and wing pressure field simulation feasibility (ARA lead)
WP3: Design and manufacture nacelle WT models, incorporating advanced instrumentation (ARA lead)
WP4: Conduct transonic WT test to provide a validation database of novel short and slim design space (ARA lead)
WP5: Installed validation of CFD short and slim nacelle design methods, and generation of design rules (CU lead)
Validation of the nacelle design tools has been enabled in part by the multi-point, multi-objective design and optimisation of compact nacelles performed in WP1. A family of axisymmetric nacelles for long and medium range operation was generated in order to develop the design tools and identify the principal aerodynamic sensitivities. The highly-automated process, employing linked tools including in-the-loop CFD (Figure 1), was controlled by genetic algorithms operating on multiple objectives in order to identify design optima. Non-axisymmetric configurations were then examined, paying attention to off-design conditions and applying novel aerodynamic performance metrics leading to down-select of four designs for WT test (long and medium range, conventional and compact). This was supported by CFD predictions of compact nacelle drag benefit when installed on the WT test rig (Figure 2) and on a representative aircraft wing (Figure 3). WP1 enabled ANACO objectives 1, 2 and 3 to be achieved.
WP2 advanced the experimental techniques for validation of nacelle drag benefit. ANACO is utilising the ARA Transonic Wind Tunnel (TWT) and Z30 isolated nacelle test rig (Figures 2 and 4), enabling external drag measurement of sting-mounted models by means of a rotating wake rake. CFD analyses facilitated optimised model integration with a new, profiled sting (Figure 5) and examined unsteady off design characteristics, informing the unsteady loading on the rig (Figure 6). CFD-based experimental uncertainty analyses identified improvements for the drag rake design and data correction methods and the necessity for improved ingested mass flow calibration. Supporting, novel test techniques have also been developed including boundary layer particle image velocimetry (BL PIV) enabling computation of surface shear stress. A new test rig (Figure 7) including a BL pressure rake and surface shear stress sensor was used for PIV validation. WP2 also investigated the feasibility of simulating the wing pressure field during WT test. A numerical study found that generation of a pressure field of the required fidelity using a swept prismatic wing would not be feasible. WP2 enabled ANACO objective 4 to be achieved.
WP3 utilised the outcome of WP1 for detailed design and manufacture of the four down-selected nacelle model geometries (Figure 8). Each model was instrumented for the measurement of surface pressure with one model also receiving unsteady pressure and surface shear stress sensors (Figure 9). A bespoke air meter design for rig mass flow calibration analysed using CFD was manufactured for application during the main test campaign scheduled for period 3.
WP4 addressed the assembly and WT test of the rig and nacelle models. The test rig was refurbished and modified in accordance with the recommendations of WP2. An initial shakedown WT test was conducted during period 2, de-risking the experimental systems and methods (Figure 10). This first test entry also supported revision of data correction algorithms prior to the upcoming main test entry.
WP5 is focused on the validation of short and slim installed nacelle design methods, and the generation of design rules for compact nacelles. CFD has been heavily used to simulate aircraft installed nacelle configurations for both long and medium range applications (Figure 11, Figure 12), quantifying the potential benefits of compact designs. Pre-test CFD simulation of the Z30 WT configurations provides numerical results for comparison with the experimental data. CFD has also been used to guide the experiment design. The research under WP1 and WP5 has developed new compact nacelle designs and evaluated integration with the aircraft. This has provided guidance on new design rules for compact nacelles and design methods to be further investigated in period 3.
WP1: Multipoint design and optimisation of short and slim nacelles (CU lead)
WP2: Downselect of novel drag measurement enhancements and wing pressure field simulation feasibility (ARA lead)
WP3: Design and manufacture nacelle WT models, incorporating advanced instrumentation (ARA lead)
WP4: Conduct transonic WT test to provide a validation database of novel short and slim design space (ARA lead)
WP5: Installed validation of CFD short and slim nacelle design methods, and generation of design rules (CU lead)
Validation of the nacelle design tools has been enabled in part by the multi-point, multi-objective design and optimisation of compact nacelles performed in WP1. A family of axisymmetric nacelles for long and medium range operation was generated in order to develop the design tools and identify the principal aerodynamic sensitivities. The highly-automated process, employing linked tools including in-the-loop CFD (Figure 1), was controlled by genetic algorithms operating on multiple objectives in order to identify design optima. Non-axisymmetric configurations were then examined, paying attention to off-design conditions and applying novel aerodynamic performance metrics leading to down-select of four designs for WT test (long and medium range, conventional and compact). This was supported by CFD predictions of compact nacelle drag benefit when installed on the WT test rig (Figure 2) and on a representative aircraft wing (Figure 3). WP1 enabled ANACO objectives 1, 2 and 3 to be achieved.
WP2 advanced the experimental techniques for validation of nacelle drag benefit. ANACO is utilising the ARA Transonic Wind Tunnel (TWT) and Z30 isolated nacelle test rig (Figures 2 and 4), enabling external drag measurement of sting-mounted models by means of a rotating wake rake. CFD analyses facilitated optimised model integration with a new, profiled sting (Figure 5) and examined unsteady off design characteristics, informing the unsteady loading on the rig (Figure 6). CFD-based experimental uncertainty analyses identified improvements for the drag rake design and data correction methods and the necessity for improved ingested mass flow calibration. Supporting, novel test techniques have also been developed including boundary layer particle image velocimetry (BL PIV) enabling computation of surface shear stress. A new test rig (Figure 7) including a BL pressure rake and surface shear stress sensor was used for PIV validation. WP2 also investigated the feasibility of simulating the wing pressure field during WT test. A numerical study found that generation of a pressure field of the required fidelity using a swept prismatic wing would not be feasible. WP2 enabled ANACO objective 4 to be achieved.
WP3 utilised the outcome of WP1 for detailed design and manufacture of the four down-selected nacelle model geometries (Figure 8). Each model was instrumented for the measurement of surface pressure with one model also receiving unsteady pressure and surface shear stress sensors (Figure 9). A bespoke air meter design for rig mass flow calibration analysed using CFD was manufactured for application during the main test campaign scheduled for period 3.
WP4 addressed the assembly and WT test of the rig and nacelle models. The test rig was refurbished and modified in accordance with the recommendations of WP2. An initial shakedown WT test was conducted during period 2, de-risking the experimental systems and methods (Figure 10). This first test entry also supported revision of data correction algorithms prior to the upcoming main test entry.
WP5 is focused on the validation of short and slim installed nacelle design methods, and the generation of design rules for compact nacelles. CFD has been heavily used to simulate aircraft installed nacelle configurations for both long and medium range applications (Figure 11, Figure 12), quantifying the potential benefits of compact designs. Pre-test CFD simulation of the Z30 WT configurations provides numerical results for comparison with the experimental data. CFD has also been used to guide the experiment design. The research under WP1 and WP5 has developed new compact nacelle designs and evaluated integration with the aircraft. This has provided guidance on new design rules for compact nacelles and design methods to be further investigated in period 3.
ANACO has advanced the state of the art in several areas. Recent advances in MOO, CFD drag prediction, parametric geometry definition and computational resources enable the investigation of Ultrafan® type nacelles. Tools for MOO and multi-point nacelle optimisation have been employed with new approaches of full CFD in-the-loop, RSM led and hybrid CFD/RSM optimisation methods, enabling the viable design space for future turbo-fan aero-engines to be determined. Comprehensive approaches have been developed for the aerodynamic design and analysis of installed, podded underwing aero-engines and for thrust-drag bookkeeping. CFD has been applied to optimisation of isolated nacelle designs and confirmation of satisfactory installed performance prior to down-select and has supported design and development of the WT test rigs and assisted with definition of the WT test plan. Existing and novel experimental measurement techniques have been developed, advancing the industrial measurement technology.
The planned WT tests will enable validation of predicted compact nacelle drag benefit, supporting generation of design rules contributing to evolutionary improvement of UHBR nacelle design and the success of European industry in this field.
The planned WT tests will enable validation of predicted compact nacelle drag benefit, supporting generation of design rules contributing to evolutionary improvement of UHBR nacelle design and the success of European industry in this field.