TY - CHAP A1 - Giersch, Thomas A1 - Kühhorn, Arnold A1 - Figaschewsky, Felix T1 - Probabilistic Analysis of Low Engine Order Excitation Due to Geometric Perturbations of Upstream Nozzle Guide Vanes : ISABE-2015-20165 T2 - Conference Proceedings from the 22nd International Symposium on Air Breathing Engines, October 25-30, 2015, Phoenix, Arizona Y1 - 2015 UR - http://hdl.handle.net/2374.UC/745749 SP - 1 EP - 9 PB - ISABE ER - TY - CHAP A1 - Figaschewsky, Felix A1 - Kühhorn, Arnold T1 - Analysis of Mistuned Blade Vibrations Based on Normally Distributed Blade Individual Natural Frequencies T2 - ASME Turbo Expo 2015: Turbine Technical Conference and Exposition Volume 7B: Structures and Dynamics Montreal, Quebec, Canada, June 15–19, 2015 N2 - With increasing demands for reliability of modern turbomachinery blades the quantification of uncertainty and its impact on the designed product has become an important part of the development process. This paper aims to contribute to an improved approximation of expected vibration amplitudes of a mistuned rotor assembly under certain assumptions on the probability distribution of the blade’s natural frequencies. A previously widely used lumped mass model is employed to represent the vibrational behavior of a cyclic symmetric structure. Aerodynamic coupling of the blades is considered based on the concept of influence coefficients leading to individual damping of the traveling wave modes. The natural frequencies of individual rotor blades are assumed to be normal distributed and the required variance could be estimated due to experiences with the applied manufacturing process. Under these conditions it is possible to derive the probability distribution of the off-diagonal terms in the mistuned equations of motions, that are responsible for the coupling of different circumferential modes. Knowing these distributions recent limits on the maximum attainable mistuned vibration amplitude are improved. The improvement is achieved due to the fact, that the maximum amplification depends on the mistuning strength. This improved limit can be used in the development process, as it could partly replace probabilistic studies with surrogate models of reduced order. The obtained results are verified with numerical simulations of the underlying structural model with random mistuning patterns based on a normal distribution of individual blade frequencies. Copyright © 2015 by ASME KW - Vibration KW - Blades Y1 - 2015 SN - 978-0-7918-5677-2 U6 - https://doi.org/10.1115/GT2015-43121 PB - ASME CY - New York, NY ER - TY - CHAP A1 - Maywald, Thomas A1 - Beirow, Bernd A1 - Heinrich, Christoph Rocky A1 - Kühhorn, Arnold T1 - Vacuum Spin Test Series of a Turbine Impeller with Focus on Mistuning and Damping by Comparing Tip Timing and Strain Gauge Results T2 - ASME Turbo Expo 2015: Turbine Technical Conference and Exposition Volume 7B: Structures and Dynamics Montreal, Quebec, Canada, June 15–19, 2015 N2 - This paper describes preparation, execution and evaluation of a comprehensive bladed disk spin test series. At the example of an turbine impeller the effects of rotation and temperature are analyzed with special focus on mistuning and damping. The forced response is measured synchronously via 13 identical positioned strain gauges on each blade as well as via blade tip-timing. Subsequently it is possible to compare the results of both systems. During the test series rotational speed varies in the range from 10.000 up to 19.000 RPM. Simultaneously, the wheel is heated up to 820 K by an oven. A number of pre-selected natural frequencies, damping ratios and operating deflection shapes are evaluated and compared with respect to different rotational speeds and impeller temperatures. Copyright © 2015 by ASME KW - Rotation KW - Vacuum KW - Impellers KW - Damping KW - Turbines KW - Strain gages Y1 - 2015 SN - 978-0-7918-5677-2 U6 - https://doi.org/10.1115/GT2015-42649 PB - ASME CY - New York, NY ER - TY - CHAP A1 - Rey Villazón, José Maria A1 - Wildow, Toni A1 - Kühhorn, Arnold A1 - Benton, Robert A1 - Eydam, Tobias T1 - Advanced Turbine Preliminary Design Environment for the automatic Generation of Secondary Air System Models T2 - ASME Turbo Expo 2015: Turbine Technical Conference and Exposition Volume 7A: Structures and Dynamics Montreal, Quebec, Canada, June 15–19, 2015 N2 - The design and development process of an aero engine is a complex and time-consuming task that involves many disciplines and company departments with different objectives and requirements. Along the preliminary design phase, multiple concepts are assessed in order to select a competitive technology. The engine design process, which was traditionally subdivided into modular component tasks, is nowadays considered as a multi-disciplinary workflow. Having recognized the need for developing advanced turbine preliminary design tools, this work focuses on enhancing the integration of turbine design disciplines, improving the accuracy of models and speeding the time to generate models. The proposed process facilitates an automated turbine Secondary Air System (SAS) and turbine discs concept definition. Furthermore, the process of CAD models and flow network models generation is accelerated via automation of the engineering workflow. This is accomplished through a novel Java based data model, where the design of turbine discs and SAS features is captured in a programmable framework. In the application section, the preliminary design definition of a reference HP turbine subsystem is replicated using the newly developed common design environment. The automated workflow is then used to generate the corresponding CAD models, recognize the subsystem flow network, and generate the 1D flow network model. The results are then compared to the experimentally validated model of a reference engine. As conclusion, the automated workflow offers a quick and parametric model generation process, while providing a good level of fidelity for the preliminary design phase. Copyright © 2015 by Rolls-Royce Deutschland Ltd & Co KG KW - Design KW - Turbines Y1 - 2015 SN - 978-0-7918-5676-5 U6 - https://doi.org/10.1115/GT2015-42661 PB - ASME CY - New York, NY ER - TY - CHAP A1 - Wagner, Frank A1 - Kühhorn, Arnold A1 - Parchem, Roland T1 - Robust design optimization applied to a high pressure turbine blade based on surrogate modelling techniques T2 - ASME Turbo Expo 2015: Turbine Technical Conference and Exposition Volume 7A: Structures and Dynamics Montreal, Quebec, Canada, June 15–19, 2015 N2 - To achieve reverse objectives in engine design, advanced modelling and analysis methods are among the key research technologies. In the presented work, a robust design optimization of a first stage high pressure turbine blade has been carried out. This blade derives from a current production of a Rolls-Royce aero engine. The motivation of this work is to show that the methodology of robust design optimization can be applied to high pressure turbine blades. A fully automated workflow, which encapsulated the integral blade design and analysis process, has been used. The main workflow objective is a representative life value of the external surface of the blade. In addition, the workflow enables the engineering uses to consider sub objectives like mass, efficiency and life at critical locations of the blade. These can also be taken into account in the multi-objective robust design optimization. This research also focuses on the use of surrogate models, with attention to the delivery of a physically correct result. For this purpose, the validation of the applied methods has a huge significance and a toolbox was created to generate and evaluate the quality of the surrogate models. In the present case sixteen geometry parameters were considered. In order to show that this methodology is not limited to geometry variation, parameters for material specification and for boundary conditions were varied in addition. The surrogate model was trained by the workflow generated DoE-data and could be used for different kinds of optimization. As a conclusion, it has been demonstrated that the methodology can be used for the engineering design process of turbine blades, while delivering physically correct results. The different techniques for surrogate modelling were examined and compared. With the help of these surrogate models, an optimization of life, mass and efficiency with 22.5 million evaluations was possible. Finally, an overview of the methodology for the case of a real world turbine blade could be given, and an improved blade in the sense of multi-objective robust design was found. Copyright © 2015 by Rolls-Royce Deutschland Ltd & Co KG KW - Turbine blades KW - High pressure (Physics) KW - Design KW - Modeling KW - Optimization Y1 - 2015 SN - 978-0-7918-5676-5 U6 - https://doi.org/10.1115/GT2015-42365 ER - TY - CHAP A1 - Beirow, Bernd A1 - Kühhorn, Arnold A1 - Figaschewsky, Felix A1 - Nipkau, Jens T1 - Effect of Mistuning and Damping on the Forced Response of a Compressor Blisk Rotor T2 - ASME Turbo Expo 2015: Turbine Technical Conference and Exposition Volume 7A: Structures and Dynamics Montreal, Quebec, Canada, June 15–19, 2015 N2 - The forced response of an E3E-type high pressure compressor blisk front rotor is analyzed with regard to intentional mistuning and its robustness towards additional random mistuning. Both a chosen alternating mistuning pattern and artificial mistuning patterns optimized concerning the forced response are considered. Focusing on three different blade modes, subset of nominal system mode-based reduced order models are employed to compute the forced response. The disk remains unchanged while the Young’s modulus of each blade is used to define the particular mistuning pattern. The well established aerodynamic influence coefficient technique is employed to model aeroelastic coupling and hence to consider the strongly mode- and inter blade phase angle-dependent aerodynamic damping contribution. It has been found that a reduction of the maximum forced response beyond that of the tuned reference can be achieved for particular mistuning patterns and all modes considered. This implies an exciting engine order which would cause a low nodal diameter mode in case of a tuned blisk. At best a nearly 50% reduction of maximum response magnitudes is computed for the fundamental bending mode and large mistuning. The solution proved to be robust towards additional random mistuning of reasonable magnitude, which is of particular interest with regard to a potential technical realization. In case of small mistuning as assumed for the first torsion and the longitudinal bending mode the advantage of achieving response magnitudes beyond the tuned reference gets lost indeed, if random mistuning is superimposed. However, mostly a lower response level is calculated compared to responses obtained from models adjusted to mistuning determined by experiment. Copyright © 2015 by ASME KW - Compressors KW - Damping KW - Rotors Y1 - 2015 SN - 978-0-7918-5677-2 U6 - https://doi.org/10.1115/GT2015-42036 PB - ASME CY - New York, NY ER - TY - CHAP A1 - Keskin, Akin A1 - Kober, Markus A1 - Stelldinger, Enrico A1 - Kühhorn, Arnold A1 - Böhm, Holger A1 - Hornig, Andreas A1 - Hufenbach, Werner T1 - On the quantification of errors of a pre-processing effort reducing contact meshing approach : AIAA 2015-0408 T2 - 53rd AIAA Aerospace Sciences Meeting 2015, Kissimmee, Florida, USA, 5 - 9 January 2015, held at the AIAA SciTech Forum 2015, vol. 4 Y1 - 2015 SN - 978-1-5108-0117-2 U6 - https://doi.org/10.2514/6.2015-0408 SP - 3113 EP - 3124 PB - Curran CY - Red Hook, NY ER - TY - CHAP A1 - Popig, Frederik A1 - Hönisch, Peter A1 - Kühhorn, Arnold T1 - Experimental and Numerical Analysis of Geometrical Induced Mistuning T2 - ASME Turbo Expo 2015: Turbine Technical Conference and Exposition Volume 7B: Structures and Dynamics Montreal, Quebec, Canada, June 15–19, 2015 N2 - The application of high pressure compressor (HPC) rotors manufactured as blisk (Blade Integrated Disk) is ever-expanding in modern jet engine designs. Despite the major advantages of less mass and higher efficiency, the most challenging problem is lower mechanical damping due to the loss of damping between blades root’s and the disk. Mistuning is induced by material inhomogeneities, manufacturing tolerances or wear during use and leads to amplitude magnification and mode localization. From the experimental point of view mistuning can be evaluated via experimental vibration analysis in terms of frequency deviations. Furthermore optical measurements can be evaluated in terms of geometrical deviations between the real and designed geometry. From the structural point of view a mistuned blisk model can be obtained by morphing the nodes of the geometrical tuned FE model or by performing blade individual stiffness mistuning due to modification of Young’s modulus. The following work is focused on the numerical prediction of mistuned blisk vibrations. Therefore, the research blisk of the 4 stage research compressor, manufactured as job-production, is analyzed. For this research blisk optical measurement data as well as experimentally obtained frequency patterns are available. In a first part mistuning identification in terms of experimental vibration analysis and Proper Orthogonal Decomposition of the geometrical deviations is presented. In a second part mistuning modeling in terms of stiffness mistuning and geometrical mistuning is applied to the tuned FE-model and the numerical results are evaluated against experimental data regarding accuracy. Furthermore, the impact of geometrical deviations on mistuning is analyzed. Copyright © 2015 by Rolls-Royce Deutschland Ltd & Co KG KW - Numerical analysis KW - Blades KW - Finite element model KW - Disks KW - Stiffness KW - Damping Y1 - 2015 UR - http://proceedings.asmedigitalcollection.asme.org/proceeding.aspx?articleID=2428632 SN - 978-0-7918-5677-2 U6 - https://doi.org/10.1115/GT2015-43272 PB - ASME CY - New York, NY ER - TY - CHAP A1 - Stelldinger, Marco A1 - Giersch, Thomas A1 - Figaschewsky, Felix A1 - Kühhorn, Arnold T1 - A Semi-Unstructured Turbomachinery Meshing Library With Focus on Modeling of Specific Geometrical Features T2 - ECCOMAS VII European Congress on Computational Methods in Applied Sciences and Engineering, Crete, Greece, June 5-10, 2016 N2 - Computational Fluid Dynamics is widely used for the analysis and the design of turbomachinery blade rows. A well established method is the application of semi-unstructured meshes, that uses a combination of structured meshes in the radial direction and unstructured meshes in the axial as well as the tangential direction. This takes advantage of the approximately two dimensional flow field through the blade rows, whereby a fine radial discretization, excepting the near wall region, is not necessary. Otherwise, it is possible to discretize particular regions, e.g. the leading and trailing edge regions, in the axial and tangential direction without generating unnecessary nodes in the far field. The meshing approach is based on the projection of a two dimensional unstructured mesh defined at a reference surface. Once, the two dimensional mesh is generated the projection is achieved by transfinite interpolation from the reference surface to further radial surfaces using a structured mesh. Due to the modeling of geometrical features, especially fillets, advanced methods for the generation of structured meshes and mesh smoothing algorithms are required. The paper presents two different approaches for the generation of an appropriate structured mesh. The first is based on the solution of elliptic partial differential equations. The second approach is based on the split of the domain into fourteen appropriately arranged blocks. Furthermore, two smoothing methods for two dimensional unstructured meshes, a constrained Laplace smoothing and an optimization based approach, are presented. Regarding a more realistic representation of the geometry, methods for the modeling of cavities, variable clearance sizes and fillets are presented. Finally, a comparison of the smoothing techniques applied to a rotor passage is presented and the influence of chosen geometrical features on the flow solution is evaluated. Y1 - 2016 UR - https://www.eccomas2016.org/proceedings/pdf/7554.pdf ER - TY - CHAP A1 - Maywald, Thomas A1 - Kühhorn, Arnold A1 - Schrape, Sven T1 - Experimental Validation of a Model Update Procedure Focusing on Small Geometric Deviations T2 - ECCOMAS VII European Congress on Computational Methods in Applied Sciences and Engineering, Crete, Greece, June 5-10, 2016 N2 - This contribution presents a model update procedure and its experimental validation using the example of a blade integrated disk rotor. This so called blisk is discretized using the finite element method. It is well known that numerical blisk models based on the ideal tuned design show major differences in structural dynamic behavior compared to the real rotor. In this context a modification of the mechanical simulation model should lead to a better accordance of numerical results and the real blisk characteristics. The described model update procedure utilizes data of an optical 3D measurement system. Using this data enables to identify geometric deviations between the ideal design and its real counterpart. Within the update procedure the originally tuned finite element mesh is modified in order to match the measured geometry of the real part. This is done by defining several morph regions. The outer surface nodes of these morph regions change their position along the surface normal vector until they meet the defined deviation constraint. Based on eigenvalue calculations employing free boundary conditions the sensitivity of structural dynamic behavior is shown with respect to small geometric changes. Finally computed eigenvalues and eigenvectors of the updated simulation model are compared with vibration measurement data. A laser Doppler vibrometer is used to detect the vibration responses of the impact excited structure. All experiments are carried out under technical vacuum conditions in order to minimize ambient air damping. In the context of an experimental modal analysis this low damping condition helps to identify more natural frequencies of the investigated structure. This leads to a much more efficient model validation. Y1 - 2016 UR - https://www.eccomas2016.org/proceedings/pdf/7386.pdf ER - TY - GEN A1 - Wagner, Frank A1 - Kühhorn, Arnold A1 - Weiss, Thomas A1 - Otto, Dierk T1 - Influence of different parametrizations on the optimum design of a high pressure turbine blade firtree T2 - ASME Turbo Expo 2016, Turbomachinery Technical Conference and Exposition, Volume 7A, Structures and Dynamics, Seoul, South Korea, June 13–17, 2016 N2 - Today the design processes in the aero industry face many challenges. Apart from automation itself, a suitable parametric geometry setup plays a significant role in making workflows usable for optimization. At the same time there are tough requirements against the parametric model. For the lowest number of possible parameters, which should be intuitively ascertainable, a high flexibility has to be ensured. Within the parameter range an acceptable stability is necessary. Under these constraints the creation of such parametric models is a challenge, which should not be underestimated especially for a complex geometry. In this work different kinds of parametrization with different levels of complexity will be introduced and compared. Thereby several geometry elements will be used to handle the critical regions of the geometry. In the simplest case a combination of lines and arcs will be applied. These will be replaced by superior elements like a double arc construct or different formulations of b-splines. There will be an additional focus on the variation of spline degree and control points. To guarantee consistency a set of general parameters will be used next to the specific ones at the critical regions. The different parameter boundaries have a influence on the possible geometries and should therefore be tested separately before an optimization run. Y1 - 2016 SN - 978-0-7918-4983-5 U6 - https://doi.org/10.1115/GT2016-56749 PB - ASME CY - New York, NY ER - TY - GEN A1 - Beirow, Bernd A1 - Maywald, Thomas A1 - Figaschewsky, Felix A1 - Kühhorn, Arnold A1 - Heinrich, Christoph Rocky A1 - Giersch, Thomas T1 - Simplified Determination of Aerodynamic Damping for Bladed Rotors, Part 1: Experimental Validation at Rest T2 - ASME Turbo Expo 2016, Turbomachinery Technical Conference and Exposition, Volume 7B, Structures and Dynamics, Seoul, South Korea, June 13–17, 2016 N2 - Considering both a radial turbine rotor of a turbocharger and an axial compressor test blisk at rest, aerodynamic damping characteristics are experimentally and numerically analyzed. Linear dependencies of modal damping ratios on the ambient pressure or the acoustic impedance, respectively, could be shown within experiments carried out inside a pressure chamber. The impact of the ambient air clearly dominates the modal damping ratios compared to the minor contribution of the structure. Assuming that acoustic emission can be regarded as main source of aerodynamic damping a simplified approach for its determination is introduced which only depends on natural frequency, mode shape and acoustic impedance. It is shown that a satisfying match between experiment and computation is achieved for those cases which are dedicated to sufficiently small ratios between wave lengths of acoustic emissions and blade distances. Y1 - 2016 SN - 978-0-7918-4984-2 U6 - https://doi.org/10.1115/GT2016-56535 N1 - Paper No. GT2016-56535 PB - ASME CY - New York, NY ER - TY - GEN A1 - Figaschewsky, Felix A1 - Kühhorn, Arnold A1 - Beirow, Bernd A1 - Giersch, Thomas A1 - Nipkau, Jens A1 - Meinl, Ferdinand T1 - Simplified Estimation of Aerodynamic Damping for Bladed Rotors, Part 2: Experimental Validation During operation T2 - ASME Turbo Expo 2016, Turbomachinery Technical Conference and Exposition, Volume 7B, Structures and Dynamics, Seoul, South Korea, June 13–17, 2016 N2 - Due to increasing requirements of future engine projects, much effort has been spent on the design of more efficient turbomachinery blades in the recent years. Besides aerodynamic efficiency constraints, these designs need to meet structural criteria ensuring that they are safe and robust with respect to High Cycle Fatigue (HCF). The estimation of the resonant vibration amplitude is done based on the aerodynamic force and the overall damping level. Since, for many applications the contribution of mechanical damping is often rather low compared to the aerodynamic counterpart, the determination of the aerodynamic damping is vital for the estimation of the forced vibration response. This second part is meant to contribute to a simplified computation of the aerodynamic damping during operation by making additional assumptions: The investigated mode family shall not suffer from flutter, has a high reduced frequency and the influence of adjacent blades is negligible. Under these circumstances a simplified approach can be introduced that allows for the computation of the mean value of the aerodynamic damping based on a steady state CFD solution of the regarded stage. It is well known, that the aerodynamic damping of a blade mode family depends on the inter blade phase angle (IBPA) and its direction of propagation, which is not covered by the simplified approach. For higher modes the difference between the minimum and maximum damping is often low and the mean value is a good approximation, whereas for fundamental modes there is often a significant difference. However, it is shown that considering a mistuned vibration response of the rotor, the expected value of the mistuned damping exhibits the mean value of IBPA-dependent aerodynamic damping. CFD simulations of an oscillating airfoil indicate a certain validity range of the simplified approach based on a modified reduced frequency and inlet Mach number, which allows to determine for which industrial applications the approach is most suitable. Finally, this range of validity is verified with experimentally determined overall damping values from strain gauge measurements during operation for 2 different industrial applications, an axial compressor stage of a jet engine and a radial turbine stage of a turbocharger. Copyright © 2016 by Rolls-Royce Deutschland Ltd & Co KG Y1 - 2016 SN - 978-0-7918-4984-2 U6 - https://doi.org/10.1115/GT2016-56458 N1 - Paper No. GT2016-56458 PB - ASME CY - New York, NY [u.a.] ER -