Volume 7C: Structures and Dynamics最新文献

{"title":"Numerical and Experimental Study of Shrouded Blade Dynamics Considering Variable Operating Points","authors":"Ferhat Kaptan, L. P. Scheidt, J. Wallaschek","doi":"10.1115/GT2018-76692","DOIUrl":"https://doi.org/10.1115/GT2018-76692","url":null,"abstract":"The optimization of the mechanical design process of turbomachinery has been a subject of research for decades. In this context, many researchers developed efficient numerical methods to calculate the vibration response of bladed disks. In most cases, the studies are restricted to one single operating point of the system, which is sufficient for many applications. For turbomachinery with variable operating points, the conventional computation methods must be extended. Changing the turbine’s rotational speed Ω leads to entirely new load conditions. On the one hand, structural mechanical properties (e.g. stiffening effects) depend on the rotational speed. On the other hand, in case of coupled blades, the pressure distributions in the joints are sensitive to the rotational speed. In this paper, a model of a steam turbine blade is investigated numerically and experimentally. Beside the tip shroud contact, multiple contacts at the root of the blade are considered. The steady-state vibration response is calculated by the well-known harmonic balance method (HBM) and an alternating frequency-time scheme (AFT). In case of variable operating conditions, the stiffness matrix can be described as a matrix polynomial of second order in Ω2. The preload at the joints is based on nonlinear quasistatic finite element analysis and also depends on the rotational speed. For the first time, a computational methodology is presented for the calculation of the forced response of a fully bladed disk with multiple contacts considering rotational speed dependent structural mechanical properties and, in particular, contact pressures. The experimental study is conducted in two steps. Firstly, a single blade model is investigated at non-rotating test conditions. Here, the blade is clamped with two dummies at the shroud. The vibration response is measured for various pressure distributions at the shroud contact. The comparison with simulation results shows a very good agreement. The second step of the experimental study will be the future investigation of a bladed disk assembly on a rotating test rig. An overview of the test rig including operation conditions, excitation methods and measurement techniques is given at the end of the paper.","PeriodicalId":347795,"journal":{"name":"Volume 7C: Structures and Dynamics","volume":"194 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132671525","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Coupled Fluid Structure Simulation Method in the Frequency Domain for Turbomachinery Applications","authors":"C. Berthold, C. Frey, Harald Schönenborn","doi":"10.1115/GT2018-76220","DOIUrl":"https://doi.org/10.1115/GT2018-76220","url":null,"abstract":"Turbomachinery components are exposed to unsteady aerodynamic loads which must be considered during the design process to ensure the structural mechanical integrity. There are two primary mechanisms which cause structural vibrations and can lead to high-cycle fatigue due to high dynamic stresses: flutter (self-excited vibrations) and forced response (forced excitation, e.g. wakes from upstream blade rows). In this work an emerging numerical frequency-domain method which is designed to efficiently simulate coupled fluid-structure interaction (FSI) problems considering nonlinearities in the flow and structure is modified and applied to an academic and a realistic test case. Furthermore complex structural eigenmodes are considered instead of purely real modes as was demonstrated in the literature so far. This method is able to predict limit cycle oscillations and forced response amplitudes. The coupled solver uses the Harmonic Balance (HB) method with an alternating frequency time approach to model periodically unsteady flows and structure dynamics. The resulting nonlinear HB equations of the flow are solved with a pseudo-time stepping method while the nonlinear HB equations of the structure are solved with a Newton method. The dynamics of the involved structure are further simplified by considering only one relevant eigenmode of the structure. The method is applied to a 3D axial turbine configuration with a modified Young’s modulus for the material of the blisk. The standard flutter curve of the blade row shows that at least one eigenmode is aerodynamically unstable at certain nodal diameters. As a first model test case for the harmonic balance solver, the nonlinear structural damping is defined as a cubic modal damping term. The results of the frequency-domain method are compared to coupled FSI simulations in the time domain. The analysis shows that the frequency-domain method is very promising in terms of both computational efficiency and accuracy.","PeriodicalId":347795,"journal":{"name":"Volume 7C: Structures and Dynamics","volume":"11 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121788361","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Numerical and Experimental Estimation of the Turbine Blade Damper Efficiency","authors":"B. Shorr, N. Serebriakov, G. Mel’nikova, D. Shadrin, B. Vasilyev, A. Stadnikov","doi":"10.1115/GT2018-76974","DOIUrl":"https://doi.org/10.1115/GT2018-76974","url":null,"abstract":"Prevention of high cycle fatigue failures of blades caused by increased level of vibrational stresses is important problem in engine design and development. Different types of dampers are usually installed under the blade platforms in the region between the shanks of adjacent blades are usually used to reduce the vibrational stresses in the turbine blades. The action of these dampers is based on the vibrational energy dissipation by the dry friction forces arising due to the relative displacement of the contacting surfaces of the damper and the blade. Adoption of a reliable choice of damper design mass and stiffness at the design stage of the aircraft engines requires an experimentally validated estimation of its damping efficiency and its influence on the blade frequency characteristics. The dampers need to be tested under conditions that are maximally close to the operational conditions. This paper presents an analysis of the stress gauging results of a turbine wheel with box-type dampers of various mass. The tests were carried out on a dynamic bench where resonance oscillations of a stage for a given mode were excited by one of the harmonics to a given rotational speed under the corresponding forces pressing the dampers onto the blade platform. An estimation of the damper efficiency in a wider range of pressing forces was also obtained by conducting the laboratory tests using on a specially designed vibration unit that simulates the dampers effect on a set of three blades. Numerical analysis of the damper mass and stiffness influence on the frequency and damping characteristics of a real turbine wheel was performed. Obtained experimental data and the GAP model of contact interaction of the insert with blades were used in the MSC. Nastran software package. Analysis showed a satisfactory correlation between the calculated and experimental estimates of the decrease in resonant stresses and resonance frequency changes when the dampers are inserted. The results presented here confirm the possibility of increasing the reliability of the choice of mass and stiffness of turbine blade dampers at the design stage.","PeriodicalId":347795,"journal":{"name":"Volume 7C: Structures and Dynamics","volume":"62 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115276156","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Practical Optimization of Mistuned Bladed Disk of Steam Turbine With Free-Standing Blade Structure for Forced and Self-Excited Vibration","authors":"Y. Kaneko, K. Mori, Hiroharu Ooyama","doi":"10.1115/GT2018-75056","DOIUrl":"https://doi.org/10.1115/GT2018-75056","url":null,"abstract":"Although bladed disks are nominally designed to be cyclically symmetric (tuned system), the vibration characteristics of all the blades on a disk are slightly different due to the manufacturing tolerance, deviations in the material properties, and wear during operation. These small variations break the cyclic symmetry and split the eigenvalue pairs. Bladed disks with small variations are referred to as a mistuned system. Many researchers suggest that while mistuning has an undesirable effect on the forced response, it has a beneficial (stabilizing) effect on blade flutter (the self-excited vibration). Therefore, it is necessary to optimize a bladed disk for forced vibration and blade flutter. In this study, firstly, the stability analysis of a mistuned bladed disk of a steam turbine that experienced the blade flutter in the field is carried out by use of the reduced order model, the Fundamental Mistuning Model. It is reported that the bladed disk analyzed failed due to unstalled flutter of the 1st mode, and the problem was solved by alternating mistuning. By comparing the analysis results with these field experiences, the analysis method is validated. Secondly, a parametric study on the mistuning effect is carried out for typical mistuning patterns, such as periodic and random mistuning, for both forced and self-excited vibrations. Finally, based on the above-mentioned results, a practical optimization method considering both forced vibration and self-excited vibration with respect to the bladed disk of a steam turbine with a free-standing blade structure is proposed.","PeriodicalId":347795,"journal":{"name":"Volume 7C: Structures and Dynamics","volume":"37 2 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122248645","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Optimal Placement and Sizing of Piezoelectric Material for Multiple-Mode Vibration Reduction","authors":"Christopher R. Kelley, Jeffrey L. Kauffman","doi":"10.1115/GT2018-77025","DOIUrl":"https://doi.org/10.1115/GT2018-77025","url":null,"abstract":"Modern turbomachinery blades have extremely low inherent damping, which can lead to high transient vibrations and failure through high-cycle fatigue. Recent research seeks methods to reduce vibration with minimal effect on the weight and aerodynamic efficiency of the blade. Smart materials present an interesting means to augment the mechanical characteristics of the blade while meeting the strict requirements of the turboma-chinery environment. In particular, piezoelectric-based vibration reduction offers the potential to semi-actively reduce vibration while simultaneously harvesting enough energy to power the implementation. The placement and size of the piezoelectric material is critical to the vibration reduction capabilities of the system. Furthermore, the implementation should target multiple vibration modes. This work develops a procedure to optimize electromechanical coupling across multiple vibration modes for a representative turbine blade with a surface-mounted piezoelectric patch.","PeriodicalId":347795,"journal":{"name":"Volume 7C: Structures and Dynamics","volume":"45 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133553798","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Intentional Mistuning With Predominant Aerodynamic Effects","authors":"C. Martel, J. J. Sanchez","doi":"10.1115/GT2018-75081","DOIUrl":"https://doi.org/10.1115/GT2018-75081","url":null,"abstract":"Intentional mistuning is a well known procedure to decrease the uncontrolled vibration amplification effects of the inherent random mistuning and to reduce the sensitivity to it. The idea is to introduce an intentional mistuning pattern that is small but much larger that the existing random mistuning. The frequency of adjacent blades is moved apart by the intentional mistuning, reducing the effect of the blade-to-blade coupling and thus the effect of the random mistuning. The situation considered in this work is more complicated because the main source for the blade damping is the effect of the aerodynamic forces (as it happens in a blisk for a family of blade dominated modes with very similar frequencies). In this case the damping is clearly defined for the tuned traveling waves but not for each blade. The problem is analyzed using the Asymptotic Mistuning Model methodology. A reduced order model is derived that allows us to understand the action mechanism of the intentional mistuning, and gives a simple expression for the estimation of its beneficial effect. The results from the reduced model are compared with those from a finite element model of a more realistic rotor under different forcing conditions.","PeriodicalId":347795,"journal":{"name":"Volume 7C: Structures and Dynamics","volume":"197 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126076274","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"An Experimental Study of Resonance Frequency Detuning Applied to Blade Mistuning","authors":"Garrett K. Lopp, Jeffrey L. Kauffman","doi":"10.1115/GT2018-76834","DOIUrl":"https://doi.org/10.1115/GT2018-76834","url":null,"abstract":"Turbomachinery blade technology has recently trended towards the use of monolithic bladed disks. Although offering a wealth of benefits, this construction removes the blade attachment interface present in the conventional design, thus unintentionally removing a source of friction-based damping needed to counteract large vibrations during resonance passages. This issue is further exacerbated for blade mistuning, which is well-known to induce vibration localization with correspondingly larger vibration magnitudes. Recently, an alternative method to reduce vibration, termed Resonance Frequency Detuning (RFD), utilizes the variable stiffness properties of piezoelectric materials embedded on-blade to detune the response when approaching a resonance crossing, thus resulting in reduced vibration. For a single-degree-of-freedom (SDOF) system, the vibration reduction performance and the optimal stiffness state switching is well-defined. Previously, RFD has been experimentally validated on a representative blade for a sufficiently well-separated vibration mode, thus satisfying the SDOF assumption. No such experimental validation currently exists for a system with closely-spaced modes or, more specifically, applied to blade mistuning. This work utilizes an academic blisk machined in the form of 8 blades attached to a central hub. Each blade incorporates two collocated piezoelectric patches located near the blade root: one patch provides the stiffness state modulation, while the other patch provides actuation to mimic engine order excitations. For the forcing configuration studied, experimental results show qualitative agreement to numerical results with the vibratory response associated with the optimal stiffness state switch showing reductions across all blades.","PeriodicalId":347795,"journal":{"name":"Volume 7C: Structures and Dynamics","volume":"151 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131109818","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Selection of Dynamic Testing Measurement Locations for Integrally Bladed Disks","authors":"Joseph A. Beck, Alexander A. Kaszynski, Jeffrey M. Brown, Daniel L. Gillaugh, O. Scott-Emuakpor","doi":"10.1115/GT2018-76791","DOIUrl":"https://doi.org/10.1115/GT2018-76791","url":null,"abstract":"The selection of sensor locations during dynamic testing of integrally bladed disks (Blisks) is discussed for measuring experimental mode shapes. As-manufactured geometries of the experimental Blisk are obtained in point-cloud form via a structured light optical measurement system. The nominal finite element mesh of the Blisk is then “morphed” to the average sector of as-measured, point-cloud geometry through a mesh metamorphosis algorithm. A ray-tracing algorithm is developed for selecting observable degrees of freedom (DOFs) of the morphed mesh to an overhead laser scanning vibrometer. This set of DOFs is then down-selected since measuring tens-of-thousands of points is in-feasible during experimental testing. This selection is carried out using a Cyclic Effective Independence Method that exploits a Blisk’s cyclic symmetry to greatly reduce computational expenses. Furthermore, the approach allows for selecting points belonging to specific engine order excitations typical in engine operating environments that can be excited during bench top traveling wave testing. Measurement point locations are compared for three cyclic symmetry finite element models: a nominal coarse mesh density, a nominal fine mesh density, and a fine mesh density morphed to average sector geometries.","PeriodicalId":347795,"journal":{"name":"Volume 7C: Structures and Dynamics","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134624091","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Automated Meshing Algorithm for Generating As-Manufactured Finite Element Models Directly From As-Measured Fan Blades and Integrally Bladed Disks","authors":"A. Kaszynski, Joseph A. Beck, Jeffrey M. Brown","doi":"10.1115/GT2018-76375","DOIUrl":"https://doi.org/10.1115/GT2018-76375","url":null,"abstract":"Automated tetrahedral meshing from manifold tessellated optical scan data is investigated to determine its viability as an approach for finite element analysis. This approach avoids the costs of constructing a volumetric representation of the scan data that can be meshed with conventional grid generation approaches. This paper demonstrates an auto-meshing algorithm for inserted airfoil and integrally bladed rotor hardware. These automatically generated models are compared to experimentally obtained frequencies and mode shapes for validation.\u0000 In an effort to compare the fidelity as well as the effect of mesh density on analytical convergence rate, manually generated all-hexahedral models are compared against the auto-meshed tetrahedral finite element models. CPU time, solution accuracy, and mesh convergence are evaluated to determine the viability of automatically generated tetrahedral meshes versus the standard approach of manually generating hex-dominant meshes. This paper demonstrates that given the power of modern CPUs, automatically generated all-tetrahedral meshes can serve as a viable alternative to manually generated hex-dominant finite element models, especially when these meshes can be refined for solution convergence within the auto-mesher. This new approach effectively solves both the mesh convergence problem while demonstrating that models based on as-measured geometry can be rapidly built with virtually no human interaction.","PeriodicalId":347795,"journal":{"name":"Volume 7C: Structures and Dynamics","volume":"164 10 Pt 1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127528163","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"ASME Conference Presenter Attendance Policy and Archival Proceedings","authors":"","doi":"10.1115/gt2018-ns7c","DOIUrl":"https://doi.org/10.1115/gt2018-ns7c","url":null,"abstract":"","PeriodicalId":347795,"journal":{"name":"Volume 7C: Structures and Dynamics","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130064810","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}