| 1. |
- Costa, Fabíola Paula, et al.
(författare)
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Aerodynamic Analysis of Conventional and Boundary Layer Ingesting Propellers
- 2023
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Ingår i: Journal of Engineering for Gas Turbines and Power. - : ASME International. - 1528-8919 .- 0742-4795. ; 145:1
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Tidskriftsartikel (refereegranskat)abstract
- The boundary layer ingestion (BLI) concept has emerged as a novel technology for reducing aircraft fuel consumption. Several studies designed BLI-fans for aircraft. BLI-propellers, although, have still received little attention, and the choice of open-rotors or ducted propellers is still an open question regarding the best performance. The blade design is also challenging because the BLI-propulsors ingest a nonuniform flow. These aspects emphasize further investigation of unducted and ducted BLI-propulsors and the use of optimization frameworks, coupled with computational fluid dynamics simulations, to design the propeller to adapt to the incoming flow. This paper uses a multi-objective NSGA-II optimization framework, coupled with three-dimensional RANS simulations and radial basis function (RBF) metamodeling, used for the design and optimization of three propeller configurations at cruise conditions: (a) conventional propeller operating in the freestream, (b) unducted BLI-propeller, and (c) ducted BLI-propeller, both ingesting the airframe boundary layer. The optimization results showed a significant increase in chord and a decrease in the blade angles in the BLI configurations, emphasizing that these geometric parameters optimization highly affects the BLI-blade design. The unducted BLI-propeller needs approximately 40% less shaft power than the conventional propeller to generate the same amount of propeller force. The ducted BLI-propeller needs even less power, 47%. The duct contributes to the tip vortex weakening, recovering the swirl, and turning into propeller force, as noticed from 80% of the blade span to the tip. However, the unducted and ducted BLI-configurations presented a higher backward force, 26% and 46%, respectively, compared to the conventional propeller, which can be detrimental and narrow the use of these configurations.
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| 2. |
- Lejon, Marcus, 1986, et al.
(författare)
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The Impact of Manufacturing Variations on Performance of a Transonic Axial Compressor Rotor
- 2020
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Ingår i: Journal of Turbomachinery. - : ASME International. - 1528-8900 .- 0889-504X. ; 142:8
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, the impact of manufacturing variations on performance of an axial compressor rotor is evaluated at design rotational speed. The geometric variations from the design intent obtained from measurements were used to evaluate the impact of manufacturing variations on performance and the flow field in the rotor. The complete blisk is simulated using 3D computational fluid dynamics calculations, allowing for a detailed analysis of the impact of geometric variations on the flow. It is shown that the mean shift of the geometry from the design intent is responsible for the majority of the change in performance in terms of mass flow and total pressure ratio for this specific blisk. In terms of polytropic efficiency, the measured geometric scatter is shown to have a higher influence than the geometric mean deviation. The geometric scatter around the mean is shown to impact the pressure along the leading edge and the shock position. Furthermore, a blisk is analyzed with one blade deviating substantially from the design intent. It is shown that the impact of this blade on the flow is largely limited to the blade passages that it is directly a part of. It is also shown that the impact of this blade on the flow field can be represented by a simulation including three blade passages. In terms of loss, using five blade passages is shown to give a close estimate for the relative change in loss for the blade deviating substantially from the design intent and for the neighboring blades.
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| 3. |
- Siggeirsson, Elias, 1989, et al.
(författare)
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Integrated Compressor Duct with Bleed: Experimental Validation of a Hybrid RANS/LES Approach
- 2019
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- In this study, a comparison is performed between measurements done in an in-house experimental test rig at GKN Aerospace Engine Systems and simulations done using the commercial CFD solver ANSYS CFX. The aim is to compare a hybrid RANS/LES model to a more industrially applied RANS model in terms of capabilities of predicting the measurements. The geometry represents an intermediate compressor duct from an aircraft engine, with an integrated bleed-pipe upstream of the duct. The bleed-pipe gives a better engine control when run at part speed by uncoupling the mass-flow through the upstream and downstream components. Previous studies indicated no major separations in the intermediate compressor duct and therefore, to save computational resources, wall-functions were employed for the hybrid simulations. Overall, the CFD simulations compare well with measured data in terms of wall-pressure coefficient in the intermediate compressor duct as well as at upstream and downstream locations. In terms of normalized total pressure profiles, the CFD and the experiments agree upstream of the test section. However, at an evaluation surface downstream of the duct, only the hybrid model simulations are capable of predicting the measured total pressure. Furthermore, it has to be kept in mind that even though the SBES simulations where significantly more expensive compared to the RANS simulations, the RANS results only represent the averaged flow field, with minimum information about transient behaviour. On the contrary, the SBES simulations represent the transient flow field, where the results have to be time-averaged.
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| 4. |
- Siggeirsson, Elias, 1989, et al.
(författare)
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Numerical and experimental aerodynamic investigation of an s-shaped intermediate compressor duct with bleed
- 2020
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Ingår i: Proceedings of the ASME Turbo Expo. ; 2D-2020
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Konferensbidrag (refereegranskat)abstract
- A series of CFD simulations are performed to analyse the effects a rotor off-take bleed has on the performance of an Intermediate Compressor Duct (ICD). To validate the CFD results, a comparison is made to measurements obtained from an experimental facility located at GKN Aerospace Engine Systems in Sweden. To achieve a deeper understanding of the flow physics, hybrid RANS/LES simulations are performed for a single operating condition. The CFD simulations are capable of predicting the behavior when extracting large amount of air through the bleed pipe, where an improved prediction is obtained with the hybrid simulation. The performance of the ICD is severely compromised with increased amount of bleed as the flow delivered to the downstream component is highly disturbed. The disturbed flow is caused by the extraction of axial flow through the bleed pipe, increasing the incidence into the low-pressure compressor’s outlet guide vanes resulting in unfavorable velocity profiles into the ICD. This behavior causes the flow to separate at the OGV blades, where the separation increases with increase bleed. Furthermore, when including the full bleed system, significant circumferential distortions are observed, showing the necessity of the integrated design.
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| 5. |
- Siggeirsson, Elias, 1989, et al.
(författare)
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Numerical and Experimental Aerodynamic Investigation of an S-Shaped Intermediate Compressor Duct with Bleed
- 2021
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Ingår i: Journal of Turbomachinery. - : ASME International. - 1528-8900 .- 0889-504X. ; 143:10
-
Tidskriftsartikel (refereegranskat)abstract
- A series of computational fluid dynamics (CFD) simulations are performed to analyze the effects a rotor off-take bleed has on the performance of an intermediate compressor duct (ICD). To validate the CFD results, a comparison is made to measurements obtained from an experimental facility located at GKN Aerospace Engine Systems in Sweden. To achieve a deeper understanding of the flow physics, hybrid Reynolds-averaged Navier-Stokes/large eddy simulation (RANS/LES) simulations are performed for a single operating condition. The CFD simulations are capable of predicting the behavior when extracting large amount of air through the bleed pipe, where an improved prediction is obtained with the hybrid simulation. The performance of the ICD is severely compromised with increased amount of bleed as the flow delivered to the downstream component is highly disturbed. The disturbed flow is caused by the extraction of axial flow through the bleed pipe, increasing the incidence into the low-pressure compressor's outlet guide vanes (OGVs) resulting in unfavorable velocity profiles into the ICD. This behavior causes the flow to separate at the OGV blades, where the separation increases with increasing bleed. Furthermore, when including the full bleed system, significant circumferential distortions are observed, showing the necessity of the integrated design.
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| 6. |
- Minelli, Guglielmo, 1988, et al.
(författare)
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Using horizontal sonic crystals to reduce the aeroacosutic signature of a simplified ICE3 train model
- 2021
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Ingår i: Applied Acoustics. - : Elsevier BV. - 0003-682X .- 1872-910X. ; 172
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Tidskriftsartikel (refereegranskat)abstract
- The design of noise barriers for high-speed trains is challenging due to the flow interaction between the train body and barriers. A failed design could affect the flow that in turn introduces additional aerodynamic loads to the train and generates extra noise. This study is the first investigation to numerically explore the detailed effects of noise barriers on high-speed trains. In particular, horizontal sonic crystals are compared to vertical, closed at the ground barriers in order to investigate the detailed effects of different noise screens on high-speed trains. The compressible IDDES is used to simulate the flow. The focus of this study is twofold. The first is to test if an alternative barrier typology can effectively reduce the noise signature, without having an impact on the train’s aerodynamic performance. The second is to explore the connection between the near-field velocity fluctuations and the far-field noise. A few specific tonal frequency components have been commonly reported but not clearly explained in the literature. It is unclear if the specific tonal components are less dependent on the Reynolds numbers, although, in general, energetic flow structures are dependent on inflow speeds. Concerning the noise reduction, the results show that the sonic crystal barrier case has a significantly better performance. A modal analysis is used to explore the causes of the tonal peaks and the association of the underbody swirling vortices to the far-field noise is described.
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| 7. |
- Siggeirsson, Elias, 1989, et al.
(författare)
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Off design simulations of an S-shaped intermediate compressor duct: Experimental validation of DDES and RANS using G3D::Flow
- 2020
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Ingår i: AIAA Scitech 2020 Forum. - Reston, Virginia : American Institute of Aeronautics and Astronautics. ; 1 PartF:PartF
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Konferensbidrag (refereegranskat)abstract
- A comparison is made between measurements obtained in an experimental test rig at GKN Aerospace and simulations using the CFD solver G3D::Flow, developed and maintained at Chalmers University of Technology. The geometry represents an Intermediate Compressor Duct (ICD) of an aircraft engine. The aim is to validate the different CFD turbulence closure techniques with experimental data and to compare the CFD methods with each other. The turbulence techniques used are RANS, Unsteady-RANS (URANS) and Delayed-Detached Eddy-Simulation (DDES) models. The one-equation turbulence model, developed by Spalart and Allmaras, is used as the main model for the (U)RANS simulations and as the sub-grid-scale model for the DDES. To save computational resources, wall-functions are used to model the boundary layers. Overall, the CFD simulations are in a good agreement with the measured data, where some differences are observed when considering radial profiles of total pressure, downstream of the ICD. Furthermore, there are instabilities present in the DDES simulations at the inner wall of the ICD. Large instabilities were also observed in the experiments, represented by relatively large uncertainties. This behavior was not captured by the (U)RANS simulations. Additionally, the instantaneous DDES is capable of representing the true flow much better (if sufficiently small scales are resolved), where the (U)RANS results will never exist in reality, limiting the information acquired.
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| 8. |
- Siggeirsson, Elias, 1989, et al.
(författare)
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Sensitivity study of the SA-DDES shielding function
- 2018
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Ingår i: AIAA Aerospace Sciences Meeting, 2018. - Reston, Virginia : American Institute of Aeronautics and Astronautics.
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Konferensbidrag (refereegranskat)abstract
- In this paper the performance of the Delayed Detached Eddy Simulation (DDES) turbulence model is analyzed for a nozzle blade that serves as a Pre-Swirler (PSW) in an experimental test rig. The DDES model is based on the one-equation turbulence model developed by Spalart and Allmaras. The focus is put on evaluating how well the shielding function, an essential part in the DDES model, protects the boundary layer around the PSW. This study is a part of a larger project, where future ambitions are to apply the DDES model to the whole experimental rig configuration. Preliminary simulations on the PSW showed that the shielding function did not protect the boundary layer as intended. Modification to the DDES model, proposed in the literature where a coefficient in the shielding function is altered, were therefore implemented and tested with promising results. The modification results in a better model performance for the PSW. For that reason the modified model will be considered in future simulations of the full experimental rig.
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| 9. |
- Larusson, Ragnar, 1986, et al.
(författare)
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Investigation of supersonic jet flow using modal decomposition
- 2014
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Ingår i: 20th AIAA/CEAS Aeroacoustics Conference. - Reston, Virginia : American Institute of Aeronautics and Astronautics. - 9781624102851
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Konferensbidrag (refereegranskat)abstract
- Supersonic jet noise has been an important research topic for decades, both for its relevance within the aeronautical industry and for its scientific value. In the present study, the jet flow field produced by a slightly over expanded conical convergent-divergent nozzle was studied using modal decomposition. The nozzle exit Mach number is 1.58 at a nozzle pressure ratio of 4.0. The nozzle has an engine like geometry with a relatively sharp throat, creating an internal shock wave. Two different methods for modal decomposition were applied to the supersonic jet flow, namely Dynamic Mode Decomposition (DMD) and a method based on the Arnoldi algorithm. The DMD algorithm returns the eigenmodes of an approximate linear flow operator, which is constructed from the data set used in the algorithm. In the present study, the DMD algorithm was applied to observational data from a Large Eddy Simulation (LES) and 2D axisymmetric URANS simulation, respectively. The Arnoldi algorithm uses a 2D linearized flow solver to project the linear flow dynamics onto a reduced order Krylov subspace and computes the eigenmodes of that projection. Here, A steady state RANS solution of the jet flow was used as a reference state in the linear solver. The Results of the Arnoldi analysis for a azimuthal wavenumber m = 0 were directly compered with the DMD modes of a URANS simulations. It was found that both methods produce nearly identical modes in this case. The DMD modes of the LES data are comparable with the Arnoldi and URANS DMD modes in terms of frequency, acoustic radiation, and shock-cell movement. They were however, found to be significantly more damped. An additional Arnoldi analysis was performed with azimuthal wavenumber m = 1 and the resulting least damped mode had a frequency close to the experimentally observed screech frequency for the same nozzle geometry and operating condition. An animation of the evolution of the eigenmode reveals a feedback loop mechanisms that might contribute to the formation of screech tones.
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| 10. |
- Hafsteinsson, Haukur, 1984, et al.
(författare)
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Noise Control of Supersonic Jet with Steady and Flapping Fluidic Injection
- 2015
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Ingår i: AIAA Journal. - 1533-385X .- 0001-1452. ; 53:11, s. 3251-3272
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Tidskriftsartikel (refereegranskat)abstract
- Large-eddy simulation is used to investigate steady-state mass flow injection into a supersonic jet stream with and without flapping motion of the microjets. The results are validated with particle image velocimetry and acoustic measurements. The effect of microjet penetration on the far-field acoustics is studied by altering the number of injectors, the cross-sectional area of each injector, and the injection mass flow. The injectors are evenly distributed around the nozzle exit. The injection angle is 90 deg relative to the main jet flow. This research is a continuation of a previous large-eddy simulation study of pulsed injection that showed that the unsteady injection-induced pressure pulses in the jet caused increased tonal noise for far-field observers at low angles. Flapping jet injection was shown to minimize the creation of the pressure pulses, except for high-amplitude flapping angles and high injection mass flows, where the injections divert out of the shear layer and introduce periodic superposition of the double shock-cell structure. Furthermore, the flapping injection did not show improved noise reduction compared with the steady injection, which is essentially promising because steady injection proves to be a more practical solution for implementation in real jet engine applications.
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