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  • 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.
  • 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: ASME Turbo Expo 2013.
  • 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.
  • 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. - 978-079184471-7 ; 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.
  • 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 Acoustical Society of America. - 0001-4966. ; 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.
  • 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)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.
  • Van der Kelen, Christophe, 1986-, et al. (författare)
  • Measurement and Inverse Estimation of the Full Anisotropic Flow Resistivity Tensor of Melamine Foam
  • 2010
  • Rapport (övrigt vetenskapligt)abstract
    • The flow resistivity tensor, which is the inverse of the viscous per- meability tensor, is one of the most important material properties for the acoustic performance of open cell foams used in acoustic treatments. Due to the manufacturing processes, these foams are most often geomet- rically anisotropic on a microscopic scale. For such a materials there is a need for improved characterisation methods, and this paper discusses the estimation of the flow resistivity tensor of Melamine samples using a methodology which is an improvement of a method previously published by Go ̈ransson et al. The validity of the new method is in addition ver- ified for a wider range of anisotropy. Measurements are performed on cubic Melamine samples, and the resulting 3D flow resistivity tensors are presented. The anisotropic flow resistivity tensors are validated by com- parison to measurements performed on uni-directional cylindrical samples extracted from the previously measured cubic samples. The results sug- gest that there is a relation between the direction of highest flow resistivity, and the rise direction of the material.
  • Fruth, Florian, 1981- (författare)
  • Reduction of Aerodynamic Forcing inTransonic Turbomachinery
  • 2013
  • Doktorsavhandling (övrigt vetenskapligt)abstract
    • Due to more and more aggressive designs in turbomachinery, assuring the structural integrity of its components has become challenging. Also influenced by this trend is blade design, where lighter and slimmer blades, in combination with higher loading, lead to an increased risk of failure, e.g. in the form of blade vibration. Methods have been proposed to reduce vibration amplitudes for subsonic engines, but cannot directly be applied to transonic regimes due to the additional physical phenomena involved. Therefore the present work investigates numerically the influence of two methods for reducing blade vibration amplitudes in transonic turbomachines, namely varying the blade count ratio and clocking. As it is known that clocking affects the efficiency, the concurrent effects on vibration amplitudes and efficiency are analyzed and discussed in detail.For the computational investigations, the proprietary Fortran-based non-linear, viscous 3D-CFD solver VolSol is applied on two transonic compressor cases and one transonic turbine case. In order to reduce calculation time and to generate the different blade count ratios a scaling technique is applied.The first and main part of this work focuses on the influence of the reduction techniques on aerodynamic forcing. Both the change in blade count ratio and clocking position are found to have significant potential for reducing aerodynamic force amplitudes. Manipulation of the phasing of excitation sources is found herein to be a major contributor to the amplitude variation. The lowest stimulus results are achieved for de-phased excitation sources and results in multiple blade force peaks per blade passing. In the case of blade count ratio variation it was found that blockage for high blade count ratios and the change in potential field size have significant impacts on the blade forcing. For the clocking investigation, three additional operating points and blade count ratios are analyzed and prove to have an impact on the force reduction achievable by clocking.The second part of the work evaluates the influence of clocking on the efficiency of a transonic compressor. It is found that the efficiency can be increased, but the magnitude of the change and the optimal wake impingement location depend on the operating point. Moreover it is shown that optimal efficiency and aerodynamic forcing settings are not directly related. In order to approximate the range of changes of both parameters, an ellipse approximation is suggested.
  • Malla, Bhupatindra, et al. (författare)
  • Proper Orthogonal Decomposition on LES and PIV Data Sets from a Mach 0.9 Jet.
  • 2012
  • Ingår i: 50th AIAA Aerospace Sciences Meeting Including the New Horizons Forum and Aerospace Exposition. - AIAA. ; s. 12
  • Konferensbidrag (refereegranskat)abstract
    • This paper contains the complementary analysis of the results obtained through computational and experimental methods using the technique of Proper Orthogonal Decomposition (POD). A detailed study of the experimentally obtained flow field data using the method of POD has already been accomplished. The experimental data consists of the 2D visualization of the velocity field obtained using Particle Image Velocimetry (PIV). The computational process is initialized with the simulation of the 3D flow field using a steady state RANS flow solver. RANS is used as a platform to proceed towards capturing the unsteadiness of the flow field which is accomplished using the Large Eddy Simulation (LES). A significant match in the characteristics of the mode shapes has been observed, in both the axial and radial components of the velocity field, however, there is difference in the distribution of the energies over the modes. The LES predicts the energies to be higher at the lowest modes and the energy drop off rate is higher. On the contrary, PIV predicts lower energies at the first few modes, in comparison to the LES results, however the energy drop off rate is smaller.
  • Saha, Ranjan, 1984-, et al. (författare)
  • Influence of Prehistory and Leading Edge Contouring on Aero Performance of a Three-Dimensional Nozzle Guide Vane
  • 2014
  • Ingår i: Journal of turbomachinery. - ASME Press. - 0889-504X. ; 136:7, s. 071014-1-071014-10
  • Tidskriftsartikel (refereegranskat)abstract
    • Experiments are conducted to investigate the effect of the prehistory in the aerodynamicperformance of a three-dimensional nozzle guide vane with a hub leading edge contouring.The performance is determined with two pneumatic probes (five hole and three hole)concentrating mainly on the end wall. The investigated vane is a geometrically similargas turbine vane for the first stage with a reference exit Mach number of 0.9. Results arecompared for the baseline and filleted cases for a wide range of operating exit Mach numbersfrom 0.5 to 0.9. The presented data includes loading distributions, loss distributions,fields of exit flow angles, velocity vector, and vorticity contour, as well as mass-averagedloss coefficients. The results show an insignificant influence of the leading edge fillet onthe performance of the vane. However, the prehistory (inlet condition) affects significantlyin the secondary loss. Additionally, an oil visualization technique yields information aboutthe streamlines on the solid vane surface, which allows identifying the locations ofsecondary flow vortices, stagnation line, and saddle point.
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