| 1. |
- Assato, Marcelo, et al.
(författare)
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PERFORMANCE BENEFITS OF A FAN ON BLADE – FLADE – FOR A VARIABLE CYCLE ENGINE
- 2022
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Ingår i: 33th Congress of the International Council of the Aeronautical Sciences. - 2958-4647. - 9781713871163 - 9781713871163 ; 7, s. 4888-4902
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Konferensbidrag (refereegranskat)abstract
- Variable cycle engines promise to enable adaptive cycles that give close to optimal performance over a wide range of conflicting mission requirements, such as low altitude high speed flight and supercruise still providing excellent range. Modelling such engines pose challenges for general purpose software since variable geometry gas paths modify the underlying set of equations being solved. It is possible to use multiple engine models transferring design data between the models. This, however, creates a high risk for inconsistency and modelling error. It is more attractive if the solutions obtained could be determined using the same model. In this work an in-house software was developed to model an Adaptive Cycle Engine (ACE). This development was used to show how variable cycle mode switches can be integrated into general purpose performance tools. The variable cycle engine uses a FLADE, which is a "fan on blade" component, to extend its range and to provide improved subsonic performance. The individual impact of the components, its effect on propulsion performance parameters and in the engine installation were analyzed as the main results. The contribution from this paper is thus two-fold, firstly the paper goes ahead and proposes new methods for the simulation of mode switching in generic performance tools by introducing dynamic equation systems. Secondly, the paper then studies the FLADE component and its potential performance benefits if added to a conventional turbofan architecture.
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| 2. |
- 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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| 3. |
- Costa, Fabíola Paula, et al.
(författare)
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Coupled unsteady RANS and FW-H methodology for aeroacoustics prediction of high-speed propellers
- 2022
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Ingår i: 28th AIAA/CEAS Aeroacoustics Conference, 2022. - Reston, Virginia : American Institute of Aeronautics and Astronautics.
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Konferensbidrag (refereegranskat)abstract
- This work investigates the use of solid and permeable surfaces in the Ffowcs WilliamsHawkings (FW-H) analogy for predicting high-speed propeller noise. The CFD/CAA methodology encompasses unsteady Reynolds-Averaged Navier-Stokes simulations to compute the flowfield on the acoustic surface applied in the FWH analogy to obtain the noise signatures in the far-field. Furthermore, this manuscript also investigates the effects of the downstream end-cap position, on the propeller noise prediction, by using two permeable surfaces with different lengths to assess the propeller noise levels in each case. The former is a short SFW-H surface placed near the rotor, and the latter, namely the LFW-H, is a surface larger in length where the end-cap grid is placed farther downstream from the rotor. The results showed the capability of the permeable surface technique for predicting the noise with higher accuracy than the solid formulation, especially at the first blade passing frequency. Also, the larger LFW-H surface performed better than the SFW-H surface. A reason that could justify this is that the LFW-H end-cap surface is placed at a suitable distance downstream from the propeller. Therefore, the LFW-H surface can include more of the contributions of the non-linear effects or quadrupole sources enclosed within the permeable source surface region.
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| 4. |
- Da Silva, Lucilene Moraes, et al.
(författare)
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Numerical investigation of film and impingement cooling schemes for gas turbine application
- 2018
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Ingår i: Proceedings of the ASME Turbo Expo. ; 5A-2018
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Konferensbidrag (refereegranskat)abstract
- In modern gas turbine engines, many sophisticated cooling schemes are used to maintain the turbine blade temperature in acceptable levels. These schemes, such as convective cooling, film cooling, impingement cooling and the use of pin fins, can be combined to increase the cooling effectiveness. Jet impingement cooling, pin fins and convective cooling are internal cooling techniques, in which the cooling is achieved based on coolant flow through internal blade channels decreasing the blade metal temperature. Film cooling is an external cooling technique, in which the cold fluid (air) is injected into the hot gas flow through discrete holes providing a coolant film at blade surface, protecting the blade metal. In this way, the present work refers to the numerical investigation of internal and external cooling strategies applied in gas turbines. The methodology developed to analyze such strategies is based on the flat-plate approach with laboratory length scales and Computational Fluid Dynamics (CFD) techniques, being the flow, in the study domain, considered viscous, turbulent and compressible. A commercial CFD program is used to solve the general equations of fluid mechanics with Reynolds Average Navier-Stokes (RANS) technique for steady state regime and Shear Stress Transport (SST) turbulence model to determine the flow eddy viscosity. The combined effects of internal and external cooling is studied through a highly sophisticated scheme, called louver, which combines the effects of impingement and film cooling. Pin fins and ribs turbulator geometries applied in the channel between the impingement and the film cooling have the purpose of evaluating the impact of these geometries on the film cooling effectiveness over the flat surface in comparison to the louver scheme without turbulator. This study concluded that, pin fins proved to be the most promise solution because they increased in 7% the film cooling effectiveness. Ribs also have a good potential to increase the effectiveness, because an increase of 4% in film cooling effectiveness was observed. In addition, the effects of the turbulator are dependent on their location, since the turbulator positioned near the film cooling hole exit showed improvements in the film cooling effectiveness in relation to the turbulator near of the impingement cooling jet.
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| 5. |
- De Campos, Gustavo Bonolo, et al.
(författare)
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Propulsive efficiency of boundary layer ingestion propellers
- 2018
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Ingår i: 31st Congress of the International Council of the Aeronautical Sciences, ICAS 2018.
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Konferensbidrag (refereegranskat)abstract
- The pursuit of lower fuel consumption for aircraft is promoting a departure from contemporary arrangements. One example is the development of more synergetic airframe and propulsion system designs, which are expected to increase significantly aircraft efficiency mainly by means of boundary layer ingestion. By integrating propulsion and airframe, both systems will significantly impact each other. This mutual interference requires the development of novel performance evaluation methods that consider such effects. This manuscript introduces a propulsive efficiency equation for boundary layer ingestion propellers based on the power balance method. Two formulations are presented for numerical and analytical evaluations. The equation is bounded between 0 and 1 and allows a meaningful evaluation of shaft to propulsive powers conversion, which results in an accurate determination of thrust and drag. This manuscript is the first advance of a project that will develop an optimizing tool for boundary layer ingestion propellers based on computational fluid dynamic simulations. The results will be presented in subsequent manuscripts.
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| 6. |
- Ferreira da Silva, Janaina, et al.
(författare)
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Considering the Effects of Turbine Blade Cooling on Engine Performance Estimation
- 2017
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Ingår i: Proceedings of the 23rd ISABE conference 2017.
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Konferensbidrag (refereegranskat)abstract
- In gas turbines, a way to improve the engine performance is by increasing the Turbine Inlet Temperature (TIT). However, increasing TIT causes an increase in heat load of turbine components. A limit in the performance improvement is imposed by the permissible metal temperature. Engine running above the melting point of material might be achieved only by cooling turbine components or using Thermal Barrier Coating (TBC). This thermal management must be done to ensure safe and durable engine operation. The most common method to cool turbine components is bleed a portion of the compressor airflow and inject it on blades and disks. Unfortunately, the extraction has an adverse effect on engine performance compared with engine without bleed. In this paper, the cooling effects on engine performance estimation at preliminary design was analyzed. The engine configuration used in the study is a turboshaft – single spool gas turbine engine. The coolant parameters are estimated using the method developed by Young and Wilcock. The results showed that there is a marked difference on performance for uncooled and cooled turbine blades, highlighting the importance in considering the cooling on performance estimation since design preliminary phase. Ignoring the cooling in evaluation can cause up to 15% difference in net specific work.
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| 7. |
- Moraes Da Silva, Lucilene, 1987, et al.
(författare)
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Analysis of Blade Aspect Ratio’s Influence on High-Speed Axial Compressor Performance
- 2024
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Ingår i: Aerospace. - 2226-4310. ; 11:4
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Tidskriftsartikel (refereegranskat)abstract
- The ratio between blade height and chord, named the aspect ratio (AR), plays an important role in compressor aerodynamic design. Once selected, it influences stage performance, blade losses and the stage stability margin. The choice of the design AR involves both aerodynamic and mechanical considerations, and an aim is frequently to achieve the desired operating range while maximizing efficiency. For a fixed set of aerodynamic and geometric parameters, there will be an optimal choice of AR that achieves a maximum efficiency. However, for a state-of-the-art aero-engine design, optimality means multi-objective optimality, that is, reaching the highest possible efficiency for a number of operating points while achieving a sufficient stability margin. To this end, the influence of the AR on the performance of the first rotor row of a multistage, multi-objective, high-speed compressor design is analyzed. A careful setup of the high-speed aerodynamic design problem allows the effect of the AR to be isolated. Close to the optimal AR, only a modest efficiency variation is observed, but a considerable change in compressor stability margin (SM) is noted. Decreasing the AR allows for increasing efficiency, but at the expense of a reduced surge margin. This allows the designer to trade efficiency for stability. Increasing the AR, however, is shown to reduce both the surge margin and efficiency; hence, a distinct optimality in stability is observed for the analyzed rotor blade row. In this work, optimality in the surge margin with respect to the AR is observed, whereas there is a close to optimal efficiency. The predicted range from AR = 1.10 to AR = 1.64 is only indicative, considering that the definition of multi-objective optimality requires balancing efficiency and the surge margin and that the choice of balancing these two criteria requires making a design choice along a pareto optimal front.
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| 8. |
- Silva, Vinicius Tavares, et al.
(författare)
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Numerical Simulation of Nacelle Flowfield for Counter-Rotating Open Rotor Propellers
- 2017
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Ingår i: International Society of Air-breathing Engines (ISABE).
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Konferensbidrag (refereegranskat)abstract
- This paper summarizes the development of a tool for designing axisymmetric nacelles for counter-rotating open rotor (CROR) engines, based on predefined geometries, global input relations and one-dimensional perfect gas equations. A nacelle geometry was generated to match the flight conditions and base dimensions of the Airbus AI-PX7 CROR propeller. Furthermore, the 3D turbulent flowfield around the nacelle was evaluated via Computational Fluid Dynamics (CFD) for four different angles of attack: 0°, 4°, 6° and 8°. The computations were performed for the nacelle without the propellers as a first analysis. The formation of shock waves, boundary layer separation and inlet flow distortion were the main parameters of the CFD study. The nacelle design was considered to be successful as a preliminary approach, since, even for the highest angle of attack, no critical conditions for the engine performance were detected.
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| 9. |
- Tavares Silva, Vinícius, 1991, et al.
(författare)
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A Propeller Model for Steady-State and Transient Performance Prediction of Turboprop and Counter-Rotating Open Rotor Engines
- 2018
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Ingår i: Journal of Engineering for Gas Turbines and Power. - : ASME International. - 1528-8919 .- 0742-4795. ; 140:7, s. 1-13
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Tidskriftsartikel (refereegranskat)abstract
- This paper describes a methodology used for propeller performance estimation, which was implemented in an in-house modular program for gas turbine performance prediction. A model based on subsonic generic propeller maps and corrected for compressibility effects, under high subsonic speeds, was proposed and implemented. Considering this methodology, it is possible to simulate conventional turboprop architectures and counter-rotating open rotor (CROR) engines in both steady-state and transient operating conditions. Two simulation scenarios are available: variable pitch angle propeller with constant speed; or variable speed propeller with constant pitch angle. The simulations results were compared with test bench data and two gas turbine performance commercial software packages were used to fulfill the model validation for conventional turboprop configurations. Furthermore, a direct drive CROR engine was simulated using a variable inlet guide vanes (VIGV) control strategy during transient operation. The model has shown to be able to provide several information about propeller-based engine performance using few input data, and a comprehensive understanding on steady-state and transient performance behavior was achieved in the obtained results.
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| 10. |
- Tavares Silva, Vinícius, 1991, et al.
(författare)
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Influence of Variable Geometry Compressor on Transient Performance of Counter-Rotating Open Rotor Engines
- 2018
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Ingår i: Journal of Engineering for Gas Turbines and Power. - : ASME International. - 1528-8919 .- 0742-4795. ; 140:12
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Tidskriftsartikel (refereegranskat)abstract
- This work describes a methodology used for counter-rotating (CR) propellers performance estimation. The method is implemented in an in-house program for gas turbine performance prediction, making possible the simulation of the counter-rotating open rotor (CROR) architecture. The methodology is used together with a variable geometry compressor control strategy to avoid surge conditions. Two cases are simulated under transient operation for both fixed and variable geometry compressor. The influence of the variable geometry control on the transient performance of CROR engines is evaluated and a comprehensive understanding on the transient behavior of this type of engine could be obtained. It is shown that the use of the variable geometry compressor control does not significantly affect the overall engine performance, while avoiding the surge conditions, thus ensuring the engine operation safety.
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