Volume 7C: Structures and Dynamics最新文献

{"title":"Aeromechanical Response of a Distortion Tolerant Boundary Layer Ingesting Fan","authors":"A. Provenza, K. Duffy, M. Bakhle","doi":"10.1115/gt2018-77094","DOIUrl":"https://doi.org/10.1115/gt2018-77094","url":null,"abstract":"Boundary Layer Ingestion (BLI) is a propulsion technology being investigated at NASA by the Advanced Aircraft Transportation Technology (AATT) Program to facilitate a substantial reduction in aircraft fuel burn. In an attempt to experimentally demonstrate an increase in propulsive efficiency of a BLI engine, a first-of-its-kind sub-scale high-bypass ratio 22” titanium fan, designed to structurally withstand significant unsteady pressure loading caused by a heavily distorted axial air inflow, was built and then tested in the transonic section of the GRC 8′ × 6′ Supersonic Wind Tunnel. The vibratory responses of a subset of fan blades were measured using strain gages placed in four different blade pressure side surface locations. Response highlights include a significant response of the blade’s first resonance to engine order excitation below idle as the fan was spooled up and down. The fan fluttered at the design speed under off operating line, low flow conditions. This paper presents the blade vibration response characteristics over the operating range of the fan and compares them to predicted behaviors. It also provides an assessment of this distortion tolerant fan’s (DTF) ability to withstand the harsh dynamic BLI environment over an entire design life of billions of load cycles at design speed.","PeriodicalId":347795,"journal":{"name":"Volume 7C: Structures and Dynamics","volume":"26 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":"114652229","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":"The Validation of Flutter Prediction in a Linear Cascade of Non-Rigid Turbine Blades","authors":"Václav Sláma, Bartoloměj Rudas, J. Ira, A. Macálka, P. Eret, V. Tsymbalyuk","doi":"10.1115/GT2018-75502","DOIUrl":"https://doi.org/10.1115/GT2018-75502","url":null,"abstract":"In low-pressure steam turbines, aerodynamic and structural design of the last stage blades is critical in determining the power plant efficiency. The development of longer last stage blades which are recently over 1 meter in length is an important task for steam turbine manufactures. The design process involves a flutter analysis of last stage blade tip sections where increased unsteady aerodynamic forces and moments might endanger the blade aerodynamic stability. However, numerical design tools must be validated using measurements in test facilities under various operating conditions. In this work, ANSYS CFX is used for flutter prediction of turbine blade tip sections oscillating in a travelling wave mode. Simulations are compared to experimental results obtained from controlled flutter tests in a wind tunnel with a linear cascade of eight turbine blade profiles made of carbon fibre. Central four blades are flexibly mounted each with two degrees of freedom (i.e. bending and torsion motions). Large deflections of thin blade profiles are accounted for the estimation of unsteady aerodynamic forces and moments. A satisfactory agreement between the simulations and experiments is achieved.","PeriodicalId":347795,"journal":{"name":"Volume 7C: Structures and Dynamics","volume":"47 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":"125481775","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":"Aeroelastic Control on Compressor Blades With Virtual Control Surfaces: A Numerical Assessment","authors":"V. Motta, L. Malzacher, Victor Bicalho Civinelli de Almeida, D. Peitsch","doi":"10.1115/GT2018-75079","DOIUrl":"https://doi.org/10.1115/GT2018-75079","url":null,"abstract":"Plasma actuators are numerically implemented as virtual control surfaces to reduce turbomachinery blades vibration and enlarge flutter-free ranges. Actuators are located at the trailing edge of the blades, both on pressure and suction side, and are triggered either independently or alternately. Upstream blowing — i.e. plasma operating in a way that the induced flow is against the freestream — has been assessed by the authors in a previous work, and is now compared with downstream blowing — i.e. plasma-induced flow in the direction of the freestream. Steady state and traveling-wave mode calculations are performed. Transient results indicate that both upstream and downstream actuation increase remarkably the stability of the cascade. This improvement in the aeroelastic response is observed for the entire interblade phase angle range. Furthermore, the effects of locally actuating the flow on lift, drag and moment coefficients are typified. A wide range of angles of attack and blowing forces is simulated. The obtained results demonstrate that also downstream plasma actuation can be a powerful tool to deal with aeroelastic instabilities on turbomachinery, and make worthwhile to assess further in-depth the capabilities of the two actuation approaches.","PeriodicalId":347795,"journal":{"name":"Volume 7C: Structures and Dynamics","volume":"51 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":"124771213","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 Acoustic Travelling Wave System for the Analysis of Blisk Mistuning","authors":"Joshua J. Grant, M. Cosmo, J. Hou, E. O. Smith, J. D. Baar","doi":"10.1115/GT2018-75666","DOIUrl":"https://doi.org/10.1115/GT2018-75666","url":null,"abstract":"One of the few acoustic travelling wave systems (TWS) in the world has been developed by Defence Science and Technology Group Australia (DST). This system uses acoustic excitation of blisks by means of a high-powered speaker cluster. The response to this acoustic excitation is measured by a laser doppler vibrometer which shows the natural frequencies and mode shapes of the blisk. To date, this system has been verified and validated on a simple, twelve-bladed research blisk with a maximum error of 3.78% from FEM modal and harmonic analysis. Furthermore, the system has been refined and tested on a current in-service blisk with an accuracy of approximately 1%. This study outlines how the TWS has been used to investigate the effects of mistuning on blisks. Promising results have been achieved with the system able to accurately identify changes in resonant behaviour due to mistuning with correlation to finite element modelling predictions. The limitations are also outlined, along with suggested areas of research and improvement. This may ultimately result in the ability to verify manufacturer blending limits and assess the effect of foreign object damage and repairs on the dynamic response characteristics of a blisk without a complex and labour intensive mechanical spin rig investigation.","PeriodicalId":347795,"journal":{"name":"Volume 7C: Structures and Dynamics","volume":"20 2","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2018-06-11","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133008925","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":"Modelling Strategies to Obtain the Forcing Function for a Forced Response Analysis","authors":"S. Connell, L. Zori, S. Patil","doi":"10.1115/GT2018-75057","DOIUrl":"https://doi.org/10.1115/GT2018-75057","url":null,"abstract":"The forced response analysis of a turbomachinery component requires the transient pressure field over that component. For an accurate prediction, this pressure field or forcing function needs to contain the frequency signatures of adjacent components. This paper compares various efficient modelling strategies to include the effect of these adjacent components in obtaining this pressure field. The example used in this work is a hydro turbine though the strategies could be applied to other turbo machines.\u0000 The Hydro turbine example comprises a spiral casing (or a volute), inlet guide vanes, stay vanes and a rotating runner. The pitch ratio between the guide vanes and runner is 14:15. The desire is to compute the unsteady pressure field in the runner domain. The flow solver employed has a variety of simulation techniques available to compute flows in cases with unequal numbers of blades/vanes in adjacent rows (“unequal pitch”). These techniques, range from mixing plane and frozen rotor methods for steady flows to various transformation methods for unsteady flows. The transformation methods remove the need for large full or part wheel calculations. Therefore, solution can be obtained at fraction cost of the full wheel simulation. The Fourier transform method is used in this paper to model the pitch change between stator and rotor. Three transient pitch-change modelling strategies are presented, and its accuracy and solution efficiency are compared to full wheel simulation. The three pitch-change variations are: a single-frequency frozen gust analysis, a blade coupling between runner and guide vanes using pitch-change interface, and multiple-frequency frozen gust analysis which will account for the asymmetry due to presence of the spiral casing.","PeriodicalId":347795,"journal":{"name":"Volume 7C: Structures and Dynamics","volume":"14 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":"121160833","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":"Investigating Damping Performance of Laser Powder Bed Fused Components With Unique Internal Structures","authors":"O. Scott-Emuakpor, T. George, B. Runyon, C. Holycross, B. Langley, Luke Sheridan, Ryan O’Hara, Phil Johnson, Joseph A. Beck","doi":"10.1115/GT2018-75977","DOIUrl":"https://doi.org/10.1115/GT2018-75977","url":null,"abstract":"An additive manufacturing (AM) process has been used to fabricate beam components with unique internal geometries capable of reducing weight and inherently suppressing vibration of the structure. Using the laser powder bed fusion (LPBF) AM process, four unique designs are investigated to quantify and understand the damping effectiveness of this manufacturing concept. Forced-response tests are conducted to validate the damping capability of each internal design configuration. The effects of external geometry, thermal distribution associated with internal friction, strain amplitude, and loading rate dependence on damping performance are studied. The results of the studied beams are compared to the damping performance of a fully-fused, or solid baseline LPBF beam. With only 1–4% internal beam volume alteration, the four unique beams are capable of providing up to ten times damping into their respective systems compared to the baseline, solid beam. From the studies of different parameter effects on damping, the main mechanism for vibration suppression is identified. Validation of the vibration suppression physics allows for internal feature optimization via LPBF that can maximize damping effectiveness.","PeriodicalId":347795,"journal":{"name":"Volume 7C: Structures and Dynamics","volume":"26 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":"128105928","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":"Experimental Validation of Forced Response Methods in a Multi-Stage Axial Turbine","authors":"Thomas Hauptmann, C. Meinzer, J. Seume","doi":"10.1115/GT2018-75390","DOIUrl":"https://doi.org/10.1115/GT2018-75390","url":null,"abstract":"Depending on the in service condition of jet engines, turbine blades may have to be replaced, refurbished, or repaired in the course of an engine overhaul. Thus, significant changes of the turbine blade geometry can be introduced due to regeneration and overhaul processes. Such geometric variances can affect the aerodynamic and aeroelastic behavior of turbine blades. One goal in the development of the regeneration process is to estimate the aerodynamic excitation of turbine blades depending on these geometric variances caused during the regeneration. Therefore, this study presents an experimentally validated comparison of two methods for the prediction of forced response in a multistage axial turbine. Two unidirectional fluid structure interaction (FSI) methods, a time-linearized and a time-accurate with a subsequent linear harmonic analysis, are employed and the results validated against experimental data. The results show that the vibration amplitude of the time-linearized method is in good agreement with the experimental data and, also requires lower computational time than the time-accurate FSI.\u0000 Based on this result, the time-linearized method is used to perform a sensitivity study of the tip clearance size of the last rotor blade row of the five stage axial turbine. The results show that an increasing tip clearances size causes an up to 1.35 higher vibration amplitude compared to the reference case, due to increased forcing and decreased damping work.","PeriodicalId":347795,"journal":{"name":"Volume 7C: Structures and Dynamics","volume":"118 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":"115188115","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":"Conceptual Flutter Analysis of Labyrinth Seals Using Analytical Models: Part II — Physical Interpretation","authors":"A. Vega, R. Corral","doi":"10.1115/GT2018-75831","DOIUrl":"https://doi.org/10.1115/GT2018-75831","url":null,"abstract":"A simple non-dimensional model to describe the flutter onset of labyrinth seals is presented. The linearized equations for a control volume which represents the inter-fin seal cavity, retaining the circumferential unsteady flow perturbations created by the seal vibration, are used. Firstly, the downstream fin is assumed to be choked, whereas in a second step the model is generalized for unchocked exit conditions. An analytical expression for the non-dimensional work-per-cycle is derived. It is concluded that the stability of a two-fin seal, depends on three non-dimensional parameters, which allow explaining seal flutter behaviour in a comprehensive fashion. These parameters account for the effect of the pressure ratio, the cavity geometry, the fin clearance, the nodal diameter, the fluid swirl velocity, the vibration frequency and the torsion center location in a compact and interrelated form. A number of conclusions have been drawn by means of a thorough examination of the work-per-cycle expression, also known as the stability parameter by other authors. It was found that the physics of the problem strongly depends on the non-dimensional acoustic frequency. When the discharge time of the seal cavity is much greater than the acoustic propagation time, the damping of the system is very small and the amplitude of the response at the resonance conditions is very high. The model not only provides a unified framework for the stability criteria derived by Ehrich [1] and Abbot [2], but delivers an explicit expression for the work-per-cycle of a two-fin rotating seal. All the existing and well established engineering trends are contained in the model, despite its simplicity. Finally, the effect of swirl in the fluid is included. It is found that the swirl of the fluid in the inter-fin cavity gives rise to a correction of the resonance frequency and shifts the stability region. The non-dimensionalization of the governing equations is an essential part of the method and it groups physical effects in a very compact form. Part I of the paper[3] detailed the derivation of the theoretical model and drew some preliminary conclusions. Part II analyzes in depth the implications of the model and outlines the extension to multiple cavity seals.","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":"125863752","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":"The Determination of Steady-State Movements Using Blade Tip Timing Data","authors":"Mohamed Kara Mohamed, P. Bonello, P. Russhard","doi":"10.1115/GT2018-75488","DOIUrl":"https://doi.org/10.1115/GT2018-75488","url":null,"abstract":"One of the main challenges of the Blade Tip Timing (BTT) measurement method is to be able to determine the sensing position of the probe relative to the blade tip. It is highly important to identify the measurement point of BTT since each point of the blade tip may have a different vibration response. This means that a change in measurement position will affect the amplitude, phase and DC component of the results obtained from BTT data. This increases the uncertainty in the correlation between BTT measurements and Finite Element (FE) modelling. Also, the measurement point should ideally be located to measure as many modes as possible. This means that the probe’s position should not coincide with a node, or a position at which the sensor misses the blade tip. Changes in the sensing position usually arise from the steady state movements of the blades (change in mean displacement). Such movements are caused by changes to the static (thermal and pressure) loading conditions that result from changes in the rotational speed. Such movements usually have a constant direction at normal operating conditions, but the direction may fluctuate if the machine develops a fault. There are three main types of movements of the sensing position that are considered in this paper: (1) axial movement; (2) blade lean; (3) blade untwist. Ideally, the sensing position is known based on the geometries of both the blade and the probe, but due to different types of movements of the blade this position is lost. Very few works have researched the extraction of the sensing position. Such preliminary works have required a pre-knowledge of mode shapes and additional instrumentation. The aim of this paper is to present a novel method for the identification of the BTT sensing position of the probes relative to a blade tip, which can be used to quantify the above movements. The developed method works by extracting the steady state offset from measurements of blade tip displacements over a number of revolutions as the speed changes from zero to a certain value. Hence, that part of the offset that is due to the angular positioning error of the probes (outside the scope of this work) is cancelled out (since it is independent of speed). The change in steady state offset is then processed to identify the three possible movements. The new method is validated using a novel BTT simulator that is based on the modal model of the FE model of a bladed disk (“blisk”). The simulator generates BTT data for prescribed changes to the sensing position. The validation tests show that the novel algorithm can identify such movements within a 2% margin of error.","PeriodicalId":347795,"journal":{"name":"Volume 7C: Structures and Dynamics","volume":"15 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":"128271591","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":"A Comparison of Two Microslip Contact Models for Studying the Mechanics of Underplatform Dampers","authors":"Chao Xu, Dongwu Li, M. Gola, C. Gastaldi","doi":"10.1115/GT2018-76007","DOIUrl":"https://doi.org/10.1115/GT2018-76007","url":null,"abstract":"In turbine blade systems, under-platform dampers are widely used to attenuate excessive resonant vibrations. Subjected to vibration excitation, the components with frictionally constrained interfaces can involve very complex contact kinematics induced by tangential and normal relative motions. To effectively calculate the dynamics of a blade-damper system, contact models which can accurately reproduce the interface normal and tangential motions are required. The large majority of works have been developed using macroslip friction models to model the friction damping at the contact interface. However, for those cases with small tangential displacement where high normal loads are applied, macroslip models are not enough to give accurate results. In this paper two recently published microslip models are compared, between them and against the simple macroslip spring-slider model. The aim is to find to which extent these models can accurately predict damper mechanics. One model is the so called GG array, where an array of macroslip elements is used. Each macroslip element of the GG array is assigned its own contact parameters and for each of them four parameters are needed: normal stiffness, tangential stiffness, normal gap and friction coefficient. The other one is a novel continuous microslip friction model. The model is based on a modification of the original classic IWAN model to couple normal and tangential contact loads. Like the GG array the model needs normal and tangential stiffness, and friction coefficient. Unlike the GG array the model is continuous and, instead of the normal gap required by the GG array, the Modified IWAN model needs a preload value. The two models are here applied to the study of the mechanics of a laboratory under-platform damper test rig. The results from the two models are compared and allow their difference, both for damper mechanics and for the complex-spring coefficients, to be assessed.","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":"129831272","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}