| 1. |
- Capitao Patrao, Alexandre, 1988, et al.
(författare)
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An Optimization Platform for High Speed Propellers
- 2016
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- To improve the efficiency by which current power plants translate jet energy into useful thrust the use of turboprop and in particular open rotor aircraft are being revisited. One challenge in association with developing new powerplants for such aircraft is high speed propeller design in general and noise prediction in particular.The Boxprop was invented in 2009 by GKN Aerospace in order to mitigate the effects of the tip vortex on noise and to improve upon the aerodynamics of a conventional propeller blade. The Boxprop is composed of a double-bladed propeller joined at the tips, and the design has the potential to eliminate the tip vortex, and thereby decrease that particular noise source. The complex and highly three-dimensional shape of an advanced propeller blade is challenging to model with classical propeller design methods, requiring instead more sophisticated optimization methods.This paper presents an optimization platform developed for high speed propellers, and illustrates its use by performing a reduced aerodynamic optimization of the Boxprop. The optimization process starts by performing a Latin Hypercube Sampling of the design space, and analyzes the resulting geometries using CFD. A meta-model employing radial basis functions is then used to interpolate on the obtained CFD results, which the GA uses to find optimal candidates along the obtained Pareto front. These designs are then evaluated using CFD, and their data added to the meta-model. The process iterates until the meta-model converges.The results of this paper demonstrate the capability of the presented optimization platform, and applying it on the Boxprop has resulted in valuable design improvements and insights. The obtained designs show less blade interference, more efficiently loaded blades, and less produced swirl. The methodology for geometry generation, meshing and optimizing is fast, robust, and readily extendable to other types of optimization problems, and paves the way for future collaborative research in the area of turbomachinery.
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| 2. |
- Capitao Patrao, Alexandre, 1988, et al.
(författare)
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Wake Analysis of an Aerodynamically Optimized Boxprop High Speed Propeller
- 2019
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Ingår i: Journal of Turbomachinery. - : ASME International. - 1528-8900 .- 0889-504X. ; 141:9
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Tidskriftsartikel (refereegranskat)abstract
- The Boxprop is a novel, double-bladed, tip-joined propeller for high-speed flight. The concept draws inspiration from the box wing concept and could potentially decrease tip vortex strength compared with conventional propeller blades. Early Boxprop designs experienced significant amounts of blade interference. By performing a wake analysis and quantifying the various losses of the flow, it could be seen that these Boxprop designs produced 45% more swirl than a conventional reference blade. The reason for this was the proximity of the Boxprop blade halves to each other, which prevented the Boxprop from achieving the required aerodynamic loading on the outer parts of the blade. This paper presents an aerodynamic optimization of a 6-bladed Boxprop aiming at maximizing efficiency and thrust at cruise. A geometric parametrization has been adopted which decreases interference by allowing the blade halves to be swept in opposite directions. Compared with an earlier equal-thrust Boxprop design, the optimized design features a 7% percentage point increase in propeller efficiency and a lower amount of swirl and entropy generation. A vortex-like structure has also appeared downstream of the optimized Boxprop, but with two key differences relative to conventional propellers. (1) Its formation differs from a traditional tip vortex and (2) it is 46% weaker than the tip vortex of an optimized 12-bladed conventional propeller.
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| 3. |
- Kissner, Carolin, et al.
(författare)
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ACAT1 Benchmark of RANS-Informed Analytical Methods for Fan Broadband Noise Prediction-Part I-Influence of the RANS Simulation
- 2020
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Ingår i: Acoustics. - : MDPI AG. - 2624-599X. ; 2:3, s. 539-578
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Tidskriftsartikel (refereegranskat)abstract
- A benchmark of Reynolds-Averaged Navier-Stokes (RANS)-informed analytical methods, which are attractive for predicting fan broadband noise, was conducted within the framework of the European project TurboNoiseBB. This paper discusses the first part of the benchmark, which investigates the influence of the RANS inputs. Its companion paper focuses on the influence of the applied acoustic models on predicted fan broadband noise levels. While similar benchmarking activities were conducted in the past, this benchmark is unique due to its large and diverse data set involving members from more than ten institutions. In this work, the authors analyze RANS solutions performed at approach conditions for the ACAT1 fan. The RANS solutions were obtained using different CFD codes, mesh resolutions, and computational settings. The flow, turbulence, and resulting fan broadband noise predictions are analyzed to pinpoint critical influencing parameters related to the RANS inputs. Experimental data are used for comparison. It is shown that when turbomachinery experts perform RANS simulations using the same geometry and the same operating conditions, the most crucial choices in terms of predicted fan broadband noise are the type of turbulence model and applied turbulence model extensions. Chosen mesh resolutions, CFD solvers, and other computational settings are less critical.
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| 4. |
- Lindblad, Daniel, 1989, et al.
(författare)
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A Nonreflecting Formulation for Turbomachinery Boundaries and Blade Row Interfaces
- 2019
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Ingår i: AIAA Scitech 2019 Forum. - Reston, Virginia : American Institute of Aeronautics and Astronautics. - 9781624105784
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Konferensbidrag (refereegranskat)abstract
- Applying a nonreflecting formulation of a boundary condition or blade row interface is sometimes of paramount importance for obtaining an accurate prediction of turbomachinery blade flutter or tonal noise, just to name a few examples. Although the theoretical foundations for these type of boundary conditions have existed for several decades, nonreflecting boundary conditions still remain an area of active research. Today, much focus appears to be put towards obtaining more generic, higher-order and numerically stable formulations. In this work, a quasi-three-dimensional nonreflecting formulation based on the exact, nonreflecting boundary condition for a single frequency and azimuthal wave number developed by Giles is presented. The proposed formulation is applicable without modifications to both steady and unsteady simulations. An implementation strategy which is consistent for both a boundary condition and blade row interface is also presented. This implementation strategy does also partly address the stability problems often encountered when the type of formulation considered in the presented work is used together with a pseudo-time integration approach for converging the flow residual. Results from a set of two-dimensional validation cases are also presented to verify the formulation.
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| 5. |
- Lindblad, Daniel, 1989, et al.
(författare)
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Aeroacoustic Analysis of a Counter Rotating Open Rotor based on the Harmonic Balance Method
- 2018
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Ingår i: AIAA Aerospace Sciences Meeting, 2018. - Reston, Virginia : American Institute of Aeronautics and Astronautics. ; 2018:210059
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Konferensbidrag (refereegranskat)abstract
- The Counter Rotating Open Rotor (CROR) powerplant is an interesting architecture for future regional aircraft propulsion since it offers higher propulsive efficiency and thereby lower fuel consumption than the conventional Turbofan engine. The noise levels generated are however potentially larger compared to a Turbofan due in part to the absence of a ducting nacelle. This raises the need for efficient, high fidelity tools that can be used for the design and evaluation of new blade concepts capable of meeting strict noise regulations. In this paper, a Computational Aeroacoustics (CAA) platform for CRORs based on the Harmonic Balance method is presented. The method is formulated in the time domain and solves for the dominant frequencies of the flow by expressing the solution as a truncated Fourier series in time. Coupling between the resolved frequencies is furthermore possible since the nonlinear URANS equations are solved for. The far field acoustic signature is obtained by solving a convective form of the Ffowcs Williams-Hawkings equations for permeable surfaces. The CAA platform is applied to a generic, full scale, pusher type CROR operating at cruise conditions.
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| 6. |
- Lindblad, Daniel, 1989, et al.
(författare)
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Implementation of a Quasi-Three-Dimensional Nonreflecting Blade Row Interface for Steady and Unsteady Analysis of Axial Turbomachines
- 2018
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Ingår i: Turbomachinery and Core Noise. - Reston, Virginia : American Institute of Aeronautics and Astronautics. - 9781624105609 ; 5
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Konferensbidrag (refereegranskat)abstract
- Higher order nonreflecting blade row interfaces are today widely used for performing both steady and unsteady simulations of the flow within axial turbomachines. In this paper, a quasi-three-dimensional nonreflecting interface based on the exact, two-dimensional nonreflecting boundary condition for a single frequency and azimuthal wave number developed by Giles is presented. The formulation has been implemented to work for both steady simulations as well as unsteady simulations employing the nonlinear Harmonic Balance method. The theory behind the construction of the nonreflecting interface is presented and details on the numerical implementation is also provided. The implementation is verified for two dimensional wave propagation along a straight cascade. It is shown that the interface correctly absorbs incoming waves, but also found that the chosen implementation strategy may be ill-posed. A simple solution to stabilize the implementation is therefore implemented, but future work should seek a more generic solution to this problem.
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| 7. |
- Montero Villar, Gonzalo, 1992
(författare)
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Design and Detailed Analysis of Turbomachinery Blades using Truncated Domains
- 2020
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- With the continuous growth in air traffic that we are seeing nowadays comes an increase in the requirements needed to be satisfied by an aircraft for it to be certified to fly. These stricter regulations affect aspects such as CO2 emissions, sound pollution and so on, pushing manufacturers to aim for lighter, more efficient, more robust designs. These required improvements needed to keep up with the regulations might come in two different ways; by improving/optimizing existing technology, or by developing new technological concepts. In either of the two scenarios, numerical tools, such as optimization methods or reliable fluid flow simulations play a paramount role. In this thesis, the new capabilities implemented into the in-house Computational Fluid Dynamics (CFD) solver, G3D::Flow, are described. These new additions have been put in place with the objective in mind of performing broadband noise predictions of a fan/OGV configuration using hybrid RANS/LES simulations. Some of the additions to G3D::Flow include: phase-lagged pitch-wise and rotor-stator interfaces, sliding grids and synthetic turbulence injection. These methods have been then put together in order to simulate the flow around the ACAT 1 fan/OGV geometry. In this work, an optimization framework called HAMON is presented. It is based on evolutionary algorithms and can be coupled with meta-modeling techniques to speed up processes where computationally expensive simulations need to be performed, such as 3D CFD simulations. HAMON can be used to fine tune an existing design, or as it has been used here, a black-box approach. It has been able to design counter rotating open rotors with more than acceptable performance were no knowledge about propeller aerodynamics was assumed, giving all the design variables more freedom than probably needed. This black-box approach might be specially useful when optimizing new technologies for which no prior knowledge exist, allowing not only to hopefully find good designs but also to show the trends of what a good design should be like.
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| 8. |
- Montero Villar, Gonzalo, 1992
(författare)
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Detached Eddy Simulation for Aerospace Applications
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- With the continuous growth in air traffic that we see nowadays, comes an increase in the requirements needed to be satisfied in order to certify an aircraft for operation. These stricter regulations affect aspects such as CO2 emissions, sound pollution and so on, pushing manufacturers to aim for lighter, more efficient, more robust designs. These improvements might be achieved in two different ways; by improving/optimizing existing technology, or by developing new technological concepts. In either of the two scenarios, numerical tools, such as optimization methods or reliable fluid flow simulations play a paramount role. In this thesis, new functionalities implemented into the in-house compressible Computational Fluid Dynamics (CFD) solver, G3D::Flow, are described. These new additions have been put in place with the objective of performing turbomachinery simulations using hybrid RANS/LES methods as well as nozzle flow simulations. Some of the additions to G3D::Flow include: phase-lagged pitch-wise and rotor-stator interfaces based on the chorochronic method as well as a method based on Proper Orthogonal Decomposition (POD), sliding grid interface and synthetic turbulence injection. The added capabilities, enable G3D::Flow to perform high-fidelity turbomachinery CFD simulations, which were not affordable before due to their high computational cost, since truncated domains can be used. A hybrid RANS/LES simulation of the VOLVO S6 nozzle contour operating under overexpanded conditions is performed. This same geometry, under the same conditions, was previously simulated and reported using a different hybrid RANS/LES methodology. A reduction of over $50\%$ in the difference between the predicted standard deviation of the side loads and those measured in a previous experimental is observed in the current simulation. In this work, an optimization framework called HAMON is also presented, which is based on evolutionary algorithms. In cases where the optimization is based on computationally heavy tasks, such as 3D CFD simulations, meta-modeling techniques can be used to speed up the optimization processes. HAMON can be used to fine tune an existing design, or as it has been used here, as black-box approach. It has been able to design counter rotating open rotors with more than acceptable performance where no knowledge about propeller aerodynamics was assumed, giving all the design variables more freedom than probably needed. This black-box approach might be specially useful when optimizing new technologies for which no prior knowledge exist, allowing not only to, hopefully, find good designs but also to show the trends of what a good design should be like.
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| 9. |
- Montero Villar, Gonzalo, 1992, et al.
(författare)
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Effect of Airfoil Parametrization on the Optimization of Counter Rotating Open Rotors
- 2019
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Ingår i: AIAA Scitech 2019 Forum. - Reston, Virginia : American Institute of Aeronautics and Astronautics.
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Konferensbidrag (refereegranskat)abstract
- The present study compares two optimizations performed on Counter Rotating Open Rotors (CRORs) running at the same operating condition. The main difference between the two optimizations is the airfoil profile used to construct the blades. The first, uses the NACA 16 family of airfoils, whereas the second one, uses a parametrized airfoil type, CST. Two independent multi-objective optimizations are carried out using approximately the same computational resources. All the design variables except those concerning the airfoil profile, are kept with the same design freedom so that a fair comparison can be made. Both sets of configurations are aerodynamically optimized for maximum thrust coefficient and efficiency at top of climb conditions. The optimization is performed using multi-objective Differential Evolution (DE) coupled with 3D RANS simulations and Radial Basis Function (RBF) meta-modeling.
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| 10. |
- Montero Villar, Gonzalo, 1992, et al.
(författare)
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Investigation of Phase-Lagged Boundary Conditions for Turbulence Resolving Turbomachinery Simulations
- 2020
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Ingår i: AIAA AVIATION 2020 FORUM. - Reston, Virginia : American Institute of Aeronautics and Astronautics. ; 1
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Konferensbidrag (refereegranskat)abstract
- The present work explores whether phase-lagged boundary conditions can be used to perform scale resolving simulations of turbomachines. The phase-lagged approach considered is based on storing the flow signal, both at the pitch-wise boundaries and the rotor-stator interface, as its temporal Fourier coefficients for a finite number of harmonics. The method is implemented in an in-house CFD solver, G3D::Flow, which can perform both URANS and hybrid RANS/LES simulations. In order to evaluate the performance of the phase-lagged boundary condition, a comparison is made with a sliding mesh simulation on a compressor cascade. Furthermore, the possibility of breaking an error feedback loop generated in the sampling process by including multiple blade passages is also investigated. It is found that this approach greatly improves convergence and accuracy of the sampling.
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