| 1. |
- Benini, Ernesto, et al.
(författare)
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A parametric method for optimal design of two-dimensional cascades
- 2001
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Ingår i: Proceedings of the Institution of mechanical engineers. Part A, journal of power and energy. - : SAGE Publications. - 0957-6509 .- 2041-2967. ; 215:4, s. 465-473
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Tidskriftsartikel (refereegranskat)abstract
- A parametric method for optimal design of two-dimensional cascades, based on the coupling between a genetic algorithm and a commercial computational fluid dynamics code, is introduced. The results of cascade geometry optimization for a large range of inlet and outlet flow angle pairs are presented. The method is a simple as well as effective tool for the optimal design of cascades for axial flow pumps.
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| 2. |
- Benini, Ernesto, et al.
(författare)
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Axial-flow compressor model based on a cascade stacking technique and neural networks
- 2002
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Ingår i: Proceedings of the ASME Turbo Expo 2002 Turbomachinery. - New York : American Society of Mechanical Engineers. - 079183610X ; , s. 793-801
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Konferensbidrag (refereegranskat)abstract
- This paper introduces a cascade-stacking technique for the development of a gas turbine multi-stage axial-flow compressor model. A large database of stationary and rotating cascade performance is first obtained by quasi three-dimensional CFD simulations and used to train neural networks for the prediction of cascade performance under generalized conditions. Then the model directly calculates the operating point of a compressor having known geometry characteristics, including variable inlet guide/stator vane effects, as a function of mass flow rate and rotational speed. The model can also be used as a valuable preliminary design tool, obtaining geometry characteristics by imposing flow patterns.
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| 3. |
- Benini, Ernesto, et al.
(författare)
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Centrifugal compressor of a 100 kW microturbine : Part 1 - Experimental and numerical investigations on overall performance
- 2003
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Ingår i: Proceedings of the ASME Turbo Expo 2003. - New York : American Society of Mechanical Engineers. - 079183686X ; , s. 691-698
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Konferensbidrag (refereegranskat)abstract
- This paper describes on/off design performance of a centrifugal compressor of a 100 kW turbogenerator gas turbine engine used for small scale power generation. The compressor stage is made up of a radial impeller and a two-stage diffuser (radial and deswirl). Pan 1 deals with the experimental and numerical tests on overall compressor and diffuser performance: An extensive test series with steady probe measurements at impeller exit and diffuser exit is performed at different operating points and rotational speeds. This makes it possible to characterize both overall compressor and diffuser. The numerical model is based on a mixing plane at impeller-diffuser interface and therefore neglects the effect of unsteadiness due to rotor-stator interaction. Then, in part 2 the true time-dependent interaction is investigated by means of a numerical model where a sliding mesh technique is adopted. The unsteady results are then processed and compared with the steady ones regarding the flow in the diffuser. Finally, in part 3 the geometry of the compressor diffuser is optimized using an evolutionary algorithm coupled with a CFD code in order to improve compressor performance.
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| 4. |
- Benini, Ernesto, et al.
(författare)
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Centrifugal compressor of a 100 kW microturbine : Part 3 - Optimization of diffuser apparatus
- 2003
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Ingår i: Proceedings of the ASME Turbo Expo 2003. - New York : American Society of Mechanical Engineers. - 079183686X ; , s. 707-714
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Konferensbidrag (refereegranskat)abstract
- This is the last part of a three-part paper regarding performance analysis and optimization of a centrifugal compressor used in a 100 kW microturbine. This part deals with the numerical constrained optimization of the diffuser apparatus (i.e. the radial and deswirl cascades) for maximum aerodynamic efficiency and pressure recovery. The optimization is accomplished through the application of a multiobjective Pareto evolutionary algorithm which is interfaced to a parametric code, that generates the geometries to be analyzed, and a Computational Fluid Dynamics code that measures the fitness of the candidate solutions. The variables of the optimization include the main dimensions of diffuser (with a constraint on the overall radial and axial size) and the profiles' shape. The set of optimized configurations is illustrated and compared to the original one; the reason of improved performance are finally discussed.
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| 5. |
- Benini, Ernesto, et al.
(författare)
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Development of high-performance airfoils for axial flow compressors using evolutionary computation
- 2002
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Ingår i: Journal of Propulsion and Power. - : American Institute of Aeronautics and Astronautics (AIAA). - 0748-4658 .- 1533-3876. ; 18:3, s. 544-554
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Tidskriftsartikel (refereegranskat)abstract
- An original multiobjective optimization method is used to support the generation of a new family of profiles for two-dimensional cascades suitable for subsonic compressors. The aim of the optimization is to maximize the pressure ratio and to minimize the profile losses of a cascade, while conforming to a functional constraint on the operating range. The method uses an evolutionary algorithm featuring a novel evaluation technique conceived for multiobjective problems and a blade-to-blade inviscid/viscous solver for calculating flow quantities. As an example, an excerpt of optimized profiles is presented, and their performances are compared with those of conventional NACA 65 profiles. The new profiles show superior design performances both in efficiency and pressure rise, as well as a tolerance to incidence angles comparable to conventional profiles. The reasons of this improvement are discussed in detail on the basis of rigorous loss analysis.
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| 6. |
- Benini, Ernesto, et al.
(författare)
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Experimental and numerical analyses to enhance the performance of a microturbine diffuser
- 2006
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Ingår i: Experimental Thermal and Fluid Science. - : Elsevier BV. - 0894-1777 .- 1879-2286. ; 30:5, s. 427-440
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Tidskriftsartikel (refereegranskat)abstract
- This paper describes design and off-design behavior of a centrifugal compressor of a 100 kW gas turbine used for small scale power generation and establishes the guidelines to improve diffuser performance. The first part of the paper deals with the experimental and numerical tests on the overall machine: An extensive series of tests at different operating points and rotational speeds is performed using steady probe measurements at impeller exit and diffuser exit; the numerical model features a mixing plane at impeller-diffuser interface and therefore neglects the effect of unsteadiness due to rotor-stator interaction. In the second part of the paper, the true time-dependent rotor-stator interaction is investigated by means of a numerical model where a sliding mesh technique is adopted instead. The unsteady results are then processed and compared with the computed steady flow in the diffuser. Finally, the geometry of the compressor diffuser is optimized using an evolutionary algorithm coupled with a CFD code.
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| 7. |
- Benini, Ernesto, et al.
(författare)
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Innovative procedure to minimize multi-row compressor blade dynamic loading using rotor-stator interaction optimization
- 2007
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Ingår i: Proceedings of the Institution of mechanical engineers. Part A, journal of power and energy. - 0957-6509 .- 2041-2967. ; 221:1, s. 59-66
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents a two-dimensional two-objective procedure for minimizing dynamic loading and maximizing efficiency in multi-stage compressors. The procedure arises from the combination of an evolutionary algorithm and a CFD code, in which a sliding mesh technique and a time-dependent approach are implemented, enabling the study of unsteady rotor-stator interaction. The method is then applied to a two-stage compressor cascade (rotor-stator-rotor-stator). The results concerning the optimal set of geometrical parameters considered for optimization (axial distances between successive cascades, circumferential clocking between stators and between rotors) are finally presented and discussed
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| 8. |
- Benini, Ernesto, et al.
(författare)
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Optimal design of horizontal-axis wind turbines using blade-element theory and evolutionary computation
- 2002
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Ingår i: Journal of solar energy engineering. - : ASME International. - 0199-6231 .- 1528-8986. ; 124:4, s. 357-363
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Tidskriftsartikel (refereegranskat)abstract
- This paper describes a multi-objective optimization method for the design of stall-regulated horizontal-axis wind turbines. Two modules are used for this purpose: an aerodynamic model implementing the blade-element theory and a multi-objective evolutionary algorithm. The former provides a sufficiently accurate solution of the flow field around the rotor disc; the latter handles the decision variables of the optimization problem, i.e., the main geometrical parameters of the rotor configuration, and promotes function optimization. The scope of the method is to achieve the best trade-off performance betoveen two objectives: annual energy production per square meter of wind park (to be maximized) and cost of energy (to be minimized). Examples of the best solutions found by the method are described and their performance compared with those of commercial wind turbines
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| 9. |
- Magrini, Andrea, et al.
(författare)
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A review of installation effects of ultra-high bypass ratio engines
- 2020
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Ingår i: Progress in Aerospace Sciences. - : Elsevier BV. - 0376-0421. ; 119
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Tidskriftsartikel (refereegranskat)abstract
- The adoption of ultra-high bypass ratio (UHBPR) engines has been long recognised to bring about reduction of specific fuel consumption and noise emission. In the need to fulfil ambitious environmental targets and mitigate the aviation sector impact, they represent a smoother technology change, compared to futuristic aircraft designs featuring electric, distributed and boundary layer ingesting propulsion. However, the challenges related to UHBPR adoption can prevent a real system performance improvement, due to interdependent counteracting factors and enhanced interference between engine and airframe. This paper reviews the installation effects on underwing-mounted UHBPR turbofan engines, first presenting the cycle design studies and how they are affected by considering integration. The advancements in nacelle components modelling and optimisation are then reviewed, where new numerical models, statistical methods and optimisation algorithms are employed to tackle the inherently multi-objective problems. The computational estimation of installation effects and the studies on optimal engine position are also presented, highlighting the overall effect on the aerodynamic characteristics. Finally, the wind tunnel tests using powered engine simulators are discussed. The tools developed to quantify the thrust and drag figures of installed propulsors and obtain indications on their best underwing location now allow quite accurate estimations, both in numerical and experimental simulations. The higher level of interaction and the increased mutual sensitivity of engine operation and wing flow field, however, suggest the need to elaborate closely coupled methods to correctly replicate these effects and an assessment of current wind tunnel practices for the design and operation of powered engine simulators.
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| 10. |
- Toffolo, Andrea, et al.
(författare)
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Genetic diversity as an objective in multi-objective evolutionary algorithms
- 2003
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Ingår i: Evolutionary Computation. - : MIT Press - Journals. - 1063-6560 .- 1530-9304. ; 11:2, s. 151-167
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Tidskriftsartikel (refereegranskat)abstract
- A key feature of an efficient and reliable multi-objective evolutionary algorithm is the ability to maintain genetic diversity within a population of solutions. In this paper, we present a new diversity-preserving mechanism, the Genetic Diversity Evaluation Method (GeDEM), which considers a distance-based measure of genetic diversity as a real objective in fitness assignment. This provides a dual selection pressure towards the exploitation of current non-dominated solutions and the exploration of the search space. We also introduce a new multi-objective evolutionary algorithm, the Genetic Diversity Evolutionary Algorithm (GDEA), strictly designed around GeDEM and then we compare it with other state-of-the-art algorithms on a well-established suite of test problems. Experimental results clearly indicate that the performance of GDEA is top-level.
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| 11. |
- Toffolo, Andrea, et al.
(författare)
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Towards a reduction of compressor blade dynamic loading by means of rotor-stator interaction optimization
- 2002
-
Ingår i: Proceedings of the ASME Turbo Expo 2002 Turbomachinery. - New York : American Society of Mechanical Engineers. - 079183610X ; , s. 667-674
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Konferensbidrag (refereegranskat)abstract
- This paper presents a two-dimensional procedure for minimizing dynamic loading and maximizing time-averaged isentropic efficiency in multi-stage compressors. The procedure arises from the combination of an evolutionary algorithm and a CFD code in which a sliding mesh technique and a time-dependent approach are implemented enabling the study of unsteady rotor stator interaction. The method is then applied to a two-stage compressor cascade (rotor-stator-rotor-stator). The results concerning the optimal set of geometrical parameters considered for optimization (axial distances between successive cascades, circumferential clocking between stators and between rotors) are finally presented and discussed.
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| 12. |
- Vanna, Francesco De, et al.
(författare)
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Effect of convective schemes in wall-resolved and wall-modeled LES of compressible wall turbulence
- 2023
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Ingår i: Computers & Fluids. - : Elsevier BV. - 0045-7930 .- 1879-0747. ; 250, s. 105710-
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Tidskriftsartikel (refereegranskat)abstract
- The current study discusses how numerical schemes and discretization approaches affect wall-resolved and wall-modeled LES outcomes. A turbulent boundary layer setup over a flat plate in both super-and hypersonic conditions is used to illustrate the effect of different numerical discretization strategies. In particular, six convective methods are examined, as well as various degrees of hybridization between shock-capturing and centered approaches: The former introducing non-negligible numerical viscosity, the latter being virtually dissipation-free. The analysis reveals that injected numerical viscosity due to upwinding procedures consid-erably alters wall dynamics for both wall-resolved and especially wall-modeled arrangements. In particular, if low-order or pure shock-capturing schemes are used, wall modeling fails in heading the system dynamics due to a strong modulation of main turbulent features. Conversely, realistic turbulence patterns are recovered if hybrid and/or high-order shock-capturing methods are employed. Thus, the paper establishes criteria for selecting a suitable numerical setup in wall-modeled LES, providing suggestions for grid resolution levels and convective scheme selection/hybridization. An overview perspective concerning numerical diffusion coupling with turbulent stresses in wall-resolved and wall-modeled LES is also provided.
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