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Träfflista för sökning "hsv:(TEKNIK OCH TEKNOLOGIER) hsv:(Maskinteknik) hsv:(Rymd och flygteknik) srt2:(2010-2013)"

Sökning: hsv:(TEKNIK OCH TEKNOLOGIER) hsv:(Maskinteknik) hsv:(Rymd och flygteknik) > (2010-2013)

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1.
  • Saha, Ranjan, 1984-, et al. (författare)
  • Aerodynamic Implication of Endwall and Profile Film Cooling in a Transonic Annular Cascade
  • 2013
  • Ingår i: 21st ISABE Conference. - Busan, Korea.
  • Konferensbidrag (refereegranskat)abstract
    • An experimental study is performed to observe the aerodynamic implications of endwall and profile film cooling on flow structures and aerodynamic losses. The investigated vane is a geometrically similar transonic nozzle guide vane with engine-representative cooling geometry. Furthermore, a new formulation of the cooling aerodynamic loss equation is presented and compared with the conventional methods. Results from a 5-hole pneumatic probe show that the film coolant significantly alters the secondary flow structure. The effect of different assumptions for the loss calculation is shown to significantly change the measured loss.
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2.
  • Saha, Ranjan, 1984-, et al. (författare)
  • Suction and Pressure Side Film Cooling Influence on Vane Aero Performance in a Transonic Annular Cascade
  • 2013
  • Ingår i: Proceedings of the ASME Turbo Expo. - 9780791855225
  • Konferensbidrag (refereegranskat)abstract
    • An experimental study on a film cooled nozzle guide vane has been conducted in a transonic annular sector to observe the influence of suction and pressure side film cooling on aerodynamic performance. The investigated vane is a typical high pressure gas turbine vane, geometrically similar to a real engine component, operated at an exit reference Mach number of 0.89. The aerodynamic results using a five hole miniature probe are quantified and compared with the baseline case which is uncooled. Results lead to a conclusion that the aerodynamic loss is influenced substantially with the change of the cooling flow rate regardless the positions of the cooling rows. The aerodynamic loss is very sensitive to the blowing ratio and a value of blowing ratio higher than one leads to a considerable higher loss penalty. The suction side film cooling has larger influence on the aerodynamic loss compared to the pressure side film cooling. Pitch-averaged exit flow angles around midspan remain unaffected at moderate blowing ratio. The secondary loss decreases (greater decrease in the tip region compared to the hub region) with inserting cooling air for all cases compared to the uncooled case.
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3.
  • Chernoray, Valery, 1975 (författare)
  • Prediction of Laminar-Turbulent Transition on an Airfoil at High Level of Free-Stream Turbulence
  • 2013
  • Ingår i: Proc of EUCASS Conf..
  • Konferensbidrag (refereegranskat)abstract
    • Prediction of laminar-turbulent transition at high level of free-stream turbulence in boundary layers of airfoil geometries with external pressure gradient changeover is in focus. The aim is a validation of a transition model for transition prediction in turbomachinery applications. Numerical simulations have been performed by using a transition model by Langtry and Menter for a number of different cases of pressure gradient, at Reynolds number-range, based on the airfoil chord, 50 000 ≤ Re ≤ 500 000 and free-stream turbulence intensities 2 % and 4 %. The validation of the computational results against the experimental data showed good performance of used turbulence model for all test cases.
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4.
  • Niebles Atencio, Bercelay, 1979, et al. (författare)
  • An experimental study on laminar-turbulent transition at high free-stream turbulence in boundary layers with pressure gradients
  • 2012
  • Ingår i: The European Physical Journal Conferences. - : EDP Sciences. ; 25, s. Art. no. 01012-
  • Konferensbidrag (refereegranskat)abstract
    • We report here the results of a study on measurements and prediction of laminar-turbulenttransition at high free-stream turbulence in boundary layers of the airfoil-like geometries with presence of the external pressure gradient changeover. The experiments are performed for a number of flow cases with different flow Reynolds number, turbulence intensity and pressure gradient distributions. The results were then compared to numerical calculations for same geometries and flow conditions. The experiments and computations are performed for the flow parameters which are typical for turbomachinery applications and the major idea of the current study is the validation of the turbulencemodel which can be used for such engineering applications.
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6.
  • Aghaali, Habib, 1981-, et al. (författare)
  • Turbocharged SI-Engine Simulation with Cold and Hot-Measured Turbocharger Performance Maps
  • 2012
  • Ingår i: Proceedings of ASME Turbo Expo 2012, Vol 5. - : ASME Press. - 9780791844717 ; , s. 671-679
  • Konferensbidrag (refereegranskat)abstract
    • Heat transfer within the turbocharger is an issue in engine simulation based on zero and one-dimensional gas dynamics. Turbocharged engine simulation is often done without taking into account the heat transfer in the turbocharger. In the simulation, using multipliers is the common way of adjusting turbocharger speed and parameters downstream of the compressor and upstream of the turbine. However, they do not represent the physical reality. The multipliers change the maps and need often to be different for different load points. The aim of this paper is to simulate a turbocharged engine and also consider heat transfer in the turbocharger. To be able to consider heat transfer in the turbine and compressor, heat is transferred from the turbine volute and into the compressor scroll. Additionally, the engine simulation was done by using two different turbocharger performance maps of a turbocharger measured under cold and hot conditions. The turbine inlet temperatures were 100 and 600°C, respectively. The turbocharged engine experiment was performed on a water-oil-cooled turbocharger (closed waste-gate), which was installed on a 2-liter gasoline direct-injected engine with variable valve timing, for different load points of the engine. In the work described in this paper, the difference between cold and hot-measured turbocharger performance maps is discussed and the quantified heat transfers from the turbine and to/from the compressor are interpreted and related to the maps.
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7.
  • Gullberg, Peter, 1983, et al. (författare)
  • Axial fan performance predictions in CFD, comparison of MRF and sliding mesh with experiments
  • 2011
  • Ingår i: SAE Technical Papers. - 400 Commonwealth Drive, Warrendale, PA, United States : SAE International. - 0148-7191. ; 2011
  • Tidskriftsartikel (refereegranskat)abstract
    • Underhood Thermal Management has become an important topic for the majority of automotive OEM's. To keep combustion engines cool and manage waste heat efficiently is an important part in the design of vehicles with low fuel consumption. To be able to predict cooling performance and underhood airflow with good precision within a virtual design process, it is of utmost importance to model and simulate the cooling fan efficiently and accurately, and this has turned out to be challenging. Simulating the cooling fan in a vehicle installation involves capturing complex fluid dynamic interaction between rotating blades and stationary objects in the vicinity of the fan. This interaction is a function of fan rotation rate, fan blade profile, upstream and downstream installation components. The flow is usually highly turbulent and small geometry details, like the distance between the blade tip and the fan shroud, have strong impact on the fan performance characteristics. Fan installations therefore have a large influence on cooling performance which the fan data from the supplier cannot capture. Improved simulation capabilities in this area are critical for optimizing the design of energy efficient vehicles since the performance of these fans, which provide airflow to the heat exchangers used for engine cooling and HVAC system operation, have a big impact on the vehicles' overall energy efficiency. This paper presents a comparison of two methodologies for simulating fan air flows. Multiple Reference Frame (MRF) and Sliding Mesh (SM) techniques are applied for a typical heavy duty truck fan. Simulation results are compared to experimental data obtained in a fan test rig with representation of a typical truck fan installation, including fan shroud, ring, seal and an engine silhouette downstream. Results of MRF simulations are known to be sensitive to the MRF domain, which is highly constrained in tight fan installations. For typical truck installations, SM provides a more robust alternative, and better accuracy than MRF in the transitional and radial regime of the fan curve.
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8.
  • Kyprianidis, Konstantinos, et al. (författare)
  • Multi-disciplinary Analysis of a Geared Fan Intercooled Core Aero-Engine
  • 2013
  • Ingår i: <em><em>Proc. ASME</em>.</em> 55133; Volume 2: Aircraft Engine; Coal, Biomass and Alternative Fuels; Cycle Innovations, V002T07A027. GT2013-95474. - 9780791855133
  • Konferensbidrag (refereegranskat)abstract
    • Reduction of CO2 emissions is strongly linked with the improvement of engine specific fuel consumption, as well as the reduction of engine nacelle drag and weight. One alternative design approach to improving specific fuel consumption is to consider a geared fan combined with an increased overall pressure ratio intercooled core performance cycle. Thermal benefits from intercooling have been well documented in the literature. Nevertheless, there is very little information available in the public domain with respect to design space exploration of such an engine concept when combined with a geared fan. The present work uses a multidisciplinary conceptual design tool to analyse the option of an intercooled core geared fan aero engine for long haul applications with a 2020 entry into service technology level assumption.With minimum mission fuel in mind, the results indicate as optimal values a pressure ratio split exponent of 0.38 and an intercooler mass flow ratio just below 1.2 at hot-day top of climb conditions. At ISA mid-cruise conditions a specific thrust of 86m/s, a jet velocity ratio of 0.83, an intercooler effectiveness of 55% and an overall pressure ratio value of 76 are likely to be a good choice. A 70,000lbf intercooled turbofan engine is large enough to make efficient use of an all-axial compression system, particularly within a geared fan configuration, but intercooling is perhaps more likely to be applied to even larger engines.The proposed optimal jet velocity ratio is actually higher than the value one would expect by using standard analytical expressions primarily because this design variable affects core efficiency at mid-cruise due to a combination of several different subtle changes to the core cycle and core component efficiencies at this condition. Analytical expressions do not consider changes in core efficiency and the beneficial effect of intercooling on transfer efficiency, nor account for losses in the bypass duct and jet pipe, whilst a relatively detailed engine performance model such as the one utilised in this study does.Mission fuel results from a surrogate model are in good agreement with the results obtained from a rubberised-wing aircraft model for some of the design parameters. This indicates that it is possible to replace an aircraft model with specific fuel consumption and weight penalty exchange rates. Nevertheless, drag count exchange rates have to be utilised to properly assess changes in mission fuel for those design parameters that affect nacelle diameter.
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9.
  • Van der Kelen, Christophe, 1986-, et al. (författare)
  • Identification of the full anisotropic flow resistivity tensor for multiple glass wool and melamine foam samples
  • 2013
  • Ingår i: Journal of the Acoustical Society of America. - : Acoustical Society of America (ASA). - 0001-4966 .- 1520-8524. ; 134:6, s. 4659-4669
  • Tidskriftsartikel (refereegranskat)abstract
    • The flow resistivity tensor, which is the inverse of the viscous permeability tensor, is one of the most important material properties for the acoustic performance of porous materials used in acoustic treatments. Due to the manufacturing processes involved, these porous materials are most often geometrically anisotropic on a microscopic scale, and for demanding applications, there is a need for improved characterization methods. This paper discusses recent refinements of a method for the identification of the anisotropic flow resistivity tensor. The inverse estimation is verified for three fictitious materials with different degrees of anisotropy. Measurements are performed on nine glass wool samples and seven melamine foam samples, and the anisotropic flow resistivity tensors obtained are validated by comparison to measurements performed on uni-directional cylindrical samples, extracted from the same, previously measured cubic samples. The variability of flow resistivity in the batch of material from which the glass wool is extracted is discussed. The results for the melamine foam suggest that there is a relation between the direction of highest flow resistivity, and the rise direction of the material.
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10.
  • Van der Kelen, Christophe, et al. (författare)
  • Inverse estimation of static flow resistivity in porous materials : discussion of the method and results for two tested porous materials
  • 2011
  • Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
    • Porous materials are widely used in applications which focus on noise andvibration control. Their thermal, mechanical and acoustical properties arebenecial for the use of these materials in aeronautical and vehicle industries.Standard measurements for the characterization of porous materials exist andare carried out in many laboratories worldwide. However, these measurementsdo not always consider the possible anisotropy, present in porous materials.The production process of porous materials introduces an inherent geometricanisotropy in the material at micro scale, which in uences the materialproperties at macro scale. It has been shown by Khurana et al. [3] thatthe anisotropy can have a signicant in uence on the acoustical behaviourof the material, especially if the angle of incidence is increased. One ofthe macroscopic parameters, which is important for the performance ofthese material in acoustical applications, is the static ow resistivity. Themethodology to measure the ow resistivity in porous materials is described inISO 9053 [2], giving the ow resistivity of a porous material along one direction.These unidirectional measurements do not allow for a full characterization ofthe ow resistivity tensor, and hence a proper characterization of the porousmaterial. The identication method developed by Goransson et al. [1] providesa non-destructive measurement method to determine the static ow resistivitytensor. The method is based on an inverse estimation of the measured pressure drops over a cubic material sample.The method as described in the work of Goransson et al. [1] has beenimproved in several ways. The Globally Convergent Method of MovingAsymptotes (GCMMA) [5] , which assures convergence, has replaced theMethod of Moving Asymptotes (MMA) [4]. Secondly, the approach of inverseestimation has been veried for a wide range of anisotropy, by setting articialand a priori known anisotropic ow resistivity tensors as a target in theestimation. Furthermore, another approach towards the problem has beentested, in which the focus is on the eigenvalues and eigenvectors of the tensor,in stead of the independent components. In addition, a more precise descriptionof the errors will be presented as well as an error estimation.This method for identication of the anisotropic ow resistivity tensorhas been applied to two dierent porous materials, a brous glass wool anda Melamine foam. The two materials are expected to show dierent degreesof anisotropy with respect to ow resistivity. Glass wool is assumed to betransversely isotropic while the level of anisotropy of Melamine is not asobvious. The full anisotropic ow resistivity tensors of the tested glass wooland Melamine samples are presented, together with their principal valuesand directions. The eigenvalue decomposition provides an insight into theconnection between the directionality of the ow resistivity in each material,and its production process. The overall approach of the method is validated bycomparing the estimated ow resistivity tensors to the ow resistivity measuredin cylindrical samples extracted from the cubic samples tested. Furthermore, astudy of the homogeneity in density and ow resistivity for the two materialsshows that these properties vary within the block of material.References[1] P. Goransson, R. Guastavino, and N. E. Horlin. Measurement and inverseestimation of 3D anisotropic ow resistivity for porous materials.Journalof Sound and Vibration, 327:354{367, 2009.[2] ISO 9053:1991: Acoustics { materials for acoustical applications {determination of air ow resistance, 1991.[3] P. Khurana, L. Boeckx, W. Lauriks, P. Leclaire, O. Dazel, and J.F. Allard.A description of transversely isotropic sound absorbing porous materials bytransfer matrices.Journal of the Acoustical Society of America, 125:915{921,2008.[4] K. Svanberg. The method of moving asymptotes - a new method forstructural optimization.International Journal for Numerical methods inEngineering, 24:359{373, 1987.
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