| 1. |
- 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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| 2. |
- Gutierrez Salas, Mauricio, 1982-, et al.
(författare)
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Forced Response Analysis of a Mistuned Blisk Using Noncyclic Reduced-Order Models
- 2018
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Ingår i: Journal of Propulsion and Power. - 0748-4658 .- 1533-3876. ; 34:3, s. 565-577
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Tidskriftsartikel (refereegranskat)abstract
- The importance of mistuning analysis lies on understanding the distribution of the vibrational energy around the blisk. The large vibration amplitudes of individual blades inherent in mistuned blisks reduces the high cycle fatigue margin significantly. It is therefore important to perform mistuning analyses at a high accuracy while keeping the computational cost at an acceptable level. Because numerous analyses with large amount of degrees of freedom models are commonly performed, it is frequent to employ reduced-order models such as to reduce the computational effort. In this paper, a unique way to address the reduced-order model is presented, where each blisk sector is attached as individual substructures with the free-interface approach known as Craig-Chang. This implementation is compared against a fixed-interface approach known as Craig-Bampton in terms of accuracy for disk- and blade-dominated modes. Neither of these approaches applies cyclic symmetry, making them more accurate in the presence of mistuning when the harmonic patterns are destroyed. Results show the high benefits of using the free-interface approach for a mistuned forced response analysis.
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| 3. |
- Nadali Najafabadi, Hossein, et al.
(författare)
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Film Cooling Performance of Multiple Arrays of Cylindrical and Fan-Shaped Holes
- 2015
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Ingår i: Journal of Propulsion and Power. - : American Institute of Aeronautics and Astronautics. - 0748-4658 .- 1533-3876. ; 31:6, s. 1621-1630
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Tidskriftsartikel (refereegranskat)abstract
- Experimental investigations are performed on the suction side of a cooled turbineguide vane. Transient IR thermography is used to evaluate film cooling performanceof cylindrical and fan-shaped holes in a test facility representing engine conditions.Adiabatic film effectiveness (AFE) and net heat flux reduction (NHFR) results due tocoolant injection through double and multiple rows in the presence and absence of anupstream showerhead are presented. Two double staggered rows at different positionshave been cross-compared; one at a relatively high convex curvature region and theother close to the maximum throat velocity. A combination of the two double rowsis considered to be multiple rows. The tested blowing ratios are in the interval of[0.6 – 1.2] and [0.3 – 1.2] for double and multiple rows, respectively. The showerheadcooling is maintained at nominal blowing ratio. The findings suggest that the choice ofbest cooling hole shape for film cooling design can be highly influenced by the numberof cooling rows to be used and also the presence (or absence) of showerhead cooling.It is worth noting that the outcome may differ depending on the quantity of interest, i.e. AFE or NHFR.
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| 4. |
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| 5. |
- Tavares Silva, Vinícius, 1991, et al.
(författare)
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Multipoint aerodynamic design of ultrashort nacelles for ultrahigh-bypass-ratio engines
- 2022
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Ingår i: Journal of Propulsion and Power. - 1533-3876 .- 0748-4658. ; 38:4, s. 541-558
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents a newly developed methodology for multipoint aerodynamic design of ultrashort nacelles for ultrahigh-bypass-ratio turbofan engines. An integrated aerodynamic framework, based on parametric geometry generation and flowfield solution via three-dimensional Reynolds-averaged Navier-Stokes equations, was built and used for designing several ultrashort nacelle shapes and to evaluate their aerodynamic performance. An approach for modeling the inlet-fan coupling is presented and validated. A design strategy is introduced, and various test cases are evaluated under the following critical operating conditions: midcruise, low speed/high angle of attack, and pure crosswind. The major design parameters are highlighted and their influence in the flowfield is discussed in detail for all the chosen flight conditions. Performance was evaluated by assessing inlet flow distortion and by bookkeeping of thrust and drag. The framework has proven to be suitable for designing high-performance nacelles capable of operating under critical flight conditions, without flow separation or high levels of distortion. Drooping the inlet by 4 deg is shown to reduce the drag at cruise by 1.9%, which also has a large beneficial impact on internal lip separation at high-incidence conditions. Furthermore, crosswind was identified as the most severe of the conditions, requiring a drastic reshaping of the nacelle to avoid internal lip separation. Two final nacelle designs were compared: the first allowed inlet separation under a 90 deg crosswind condition, whereas the second was reshaped to be separation-free under all operating conditions. Reshaping to avoid separation has increased drag by 5.1% at cruise.
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| 6. |
- Williams, Kirk L., et al.
(författare)
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Demonstration of microcoil heaters for microthrusters
- 2007
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Ingår i: Journal of Propulsion and Power. - : American Institute of Aeronautics and Astronautics (AIAA). - 0748-4658 .- 1533-3876. ; 23:4, s. 881-884
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Tidskriftsartikel (refereegranskat)abstract
- The resilience and performance of carbon microcoil heaters made by laser-induced chemical vapor deposition (LCVD) to be used as an efficient means for increasing the specific impulse of cold/hot gas microthrusters were investigated. Two naked carbon coils and two tungsten coated carbon coils coated through LCVD were used in this experiment. Each pair of coated and uncoated carbon coils were heated resistively in a thermal cycling between 300-1173K and 973-1173K for 2 h in 0.000003 mbar and 2 bar N. The results show that at these temperatures the carbon microcoils and nitrogen propellant were compatible while the tungsten coated microcoils started degrading. It was observed that LVCD-deposited carbon and tungsten-coated carbon microcoils can withstand low to medium-high temperatures for extended periods of time during thermal cycling without showing signs of degradation.
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| 7. |
- Xu, Lei, 1988, et al.
(författare)
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Optimization Study of an Intercooled Recuperated Aero-Engine
- 2013
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Ingår i: Journal of Propulsion and Power. - 0748-4658 .- 1533-3876. ; 29:2, s. 424-432
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Tidskriftsartikel (refereegranskat)abstract
- The design space of an intercooled recuperated aero-engine has been explored using detailed engine and aircraft performance, weight, and dimensions modeling. The design parameters of the engine fan, core, intercooler, recuperator, cooling-air ratio, and variable-geometry settings for the low-pressure turbine have been optimized for minimum mission fuel. Analysis shows that the improvement achieved in terms of performance against the datum design can be attributed primarily to an increase in thermal efficiency. A parametric study has also been carried out around the optimal design to understand the impact of the chosen design parameters on mission fuel burn. The study demonstrates in detail the substantially more complex interrelationship that the different fan design parameters have in terms of engine performance compared to what is typical for conventional turbofan designs. Furthermore, the optimal pressure ratio split between the low-pressure compressor and the high-pressure compressor aligns well with a previous analytical study. It is also revealed that the increased amount of cooling air required when a hot bleeding concept is adopted is in fact beneficial for mission fuel burn. Finally, the study concludes that the potential of using variable geometry in the low-pressure turbine for improving fuel burn is limited by the high-pressure turbine blade-metal temperature.Read More: http://arc.aiaa.org/doi/abs/10.2514/1.B34594
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| 8. |
- Yan, Jinyue, et al.
(författare)
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Status and perspective of externally fired gas turbines
- 2000
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Ingår i: Journal of Propulsion and Power. - : American Institute of Aeronautics and Astronautics (AIAA). - 0748-4658 .- 1533-3876. ; 16:4, s. 572-576
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Tidskriftsartikel (refereegranskat)abstract
- Power generation with an externally fired gas turbine (EFGT) is a promising technology for solid fuels such as coal and biomass because it offers high efficiency, low cost, and low environmental impacts. Different systems of EFGT are presented, including externally fired combined cycles and externally fired humid air turbines. Recent research and engineering development of the technologies are reviewed. Topics including system configurations, thermal efficiencies, and high-temperature heat exchangers issues are discussed. The results of this study can be applied to guide the future development of solid-fuel-based externally fired gas turbine systems.
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| 9. |
- Östlund, Jan, et al.
(författare)
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Side-load phenomena in highly overexpanded rocket nozzles
- 2004
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Ingår i: Journal of Propulsion and Power. - : American Institute of Aeronautics and Astronautics (AIAA). - 0748-4658 .- 1533-3876. ; 20:4, s. 695-704
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Tidskriftsartikel (refereegranskat)abstract
- The operation of rocket engines in the overexpanded mode, that is, with the ambient pressure considerably higher than the nozzle exit wall pressure, can result in dangerous lateral loads acting on the nozzle. These loads occur as the boundary layer separates from the nozzle wall and the pressure distribution deviates from its usual axisymmetric shape. Different aerodynamic or even coupled aerodynamic/structural mechanic reasons can cause an asymmetric pressure distribution. A number of subscale tests have been performed, and three potential origins of side loads were observed and investigated, namely, the pressure fluctuations in the separation and recirculation zone due to the unsteadiness of the separation location, the transition of separation pattern between free-shock separation and restricted-shock separation, and aeroelastic coupling, which indeed cannot cause but do amply existing side loads to significant levels. All three mechanisms are described in detail, and methods are presented to calculate their magnitude and pressure ratio at which they occur.
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