| 1. |
- Fuhrer, C., et al.
(författare)
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The influence of non-equilibrium wet steam effects on the aeroelastic properties of a turbine blade row
- 2016
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Ingår i: Proceedings of the ASME Turbo Expo. - : ASME Press. - 9780791849866
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Konferensbidrag (refereegranskat)abstract
- Turbine blade flutter is a concern for the manufacturers o steam turbines. Typically, the length of last stage blades of larg steam turbines is over one meter. These long blades are susceptibl to flutter because of their low structural frequency an supersonic tip speeds with oblique shocks and their reflections Although steam condensation has usually occurred by the las stage, ideal gas is mostly assumed when performing flutter analysi for steam turbines The results of a flutter analysis of a 2D steam turbine tes case which examine the influence of non-equilibrium wet stea are presented. The geometry and flow conditions of the test cas are supposed to be similar to the flow near the tip in a stea turbine as this is where most of the unsteady aerodynamic wor contributing to flutter is done. The unsteady flow simulation required for the flutter analysis are performed by ANSYS CFX Three fluid models are examined: ideal gas, equilibrium we steam (EQS) and non-equilibrium wet steam (NES), of whic NES reflects the reality most Previous studies have shown that a good agreement betwee ideal gas and EQS simulations can be achieved if the prescribe ratio of specific heats is equal to the equilibrium polytropic inde of the wet steam flow through the turbine.
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| 2. |
- Gao, Yang, et al.
(författare)
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FORCED RESPONSE ANALYSIS OF A RADIAL TURBINE WITH DIFFERENT MODELLING METHODS
- 2019
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Ingår i: PROCEEDINGS OF THE ASME TURBO EXPO. - : ASME Press.
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Konferensbidrag (refereegranskat)abstract
- Forced response analysis is a critical part in the radial turbine design process. It estimates the vibration mode and level due to aerodynamic excitations and then enables the analysis of high-cycle fatigue (HCF) to determine the life span of the turbine stage. Two key aspects of the forced response analysis are the determination of the aerodynamic forcing and damping which can be calculated from unsteady 3D computational fluid dynamics (CFD) simulations. These simulations are problematic due to the high level of complexity in the simulations (multi row, full annular, tip gap, etc.) and the consequent high-computational cost. The aim of this paper is to investigate and compare different CFD methods applied to the forced response analysis of a radial turbine. Full annular simulations are performed for the prediction of the excitation force. This method is taken as the baseline and is usually the most time-consuming one. One method of reducing the computational effort is to use Phase-lag periodic boundary conditions. A further reduction can be obtained by using a frequency-based method called nonlinear harmonic. For the prediction of aerodamping, the Phase-lag periodic boundary condition method is also available. Moreover, a frequency-based method called harmonic balance can further accelerate the aero-damping calculation. In this paper, these CFD methods will be applied to the simulations of an open-geometry radial turbine with a vaned volute. A comparison of unsteady results from different methods will be presented. These unsteady results will also be implemented to a tuned forced response analysis in order to directly compare the corresponding maximum blade vibration amplitudes.
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| 3. |
- Gao, Yang, et al.
(författare)
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Validation of meanline performance prediction method for radial and mixed flow turbine
- 2018
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Ingår i: Institution of Mechanical Engineers - 13th International Conference on Turbochargers and Turbocharging 2018. - : Institution of Mechanical Engineers. - 9781510873872 ; , s. 357-372
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Konferensbidrag (refereegranskat)abstract
- This paper describes a meanline performance prediction method which is developed based on a preliminary design tool, namely TOPGEN. The newly proposed method extends the application of former tool to off-design conditions and mixed flow turbine. To achieve this goal, special treatments to incidence loss calculation of mixed flow turbine and throat flow prediction are developed. The method is validated against test data from open literature. The predicted results of radial turbine showed good agreement with test data on whole performance curve. For mixed flow turbine, different loss model combinations were investigated to give insights to mixed flow turbine prediction.
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| 4. |
- Gezork, Tobias, et al.
(författare)
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A NEW VISUALIZATION METHOD FOR HARMONIC UNSTEADY FLOWS IN TURBOMACHINERY
- 2016
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Ingår i: PROCEEDINGS OF THE ASME TURBO EXPO. - : AMER SOC MECHANICAL ENGINEERS.
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Konferensbidrag (refereegranskat)abstract
- Understanding unsteady flow processes is key in the analysis of challenging problems in turbomachinery design such as flutter and forced response. In this paper a new visualization method for harmonic unsteady flow is presented. The method illustrates the direction in which unsteady waves are traveling and transporting energy by the direct visualization of the propagating pressure waves in terms of field lines constructed from the wave group velocity. The group velocity is calculated from the unsteady flow solution by assuming that the local unsteady pressure perturbation of interest can be represented by a single harmonic unsteady wave. The applicability of the method is demonstrated for three test cases including a linear cascade of two-dimensional flat plates and a linear cascade of two-dimensional compressor blade profiles.
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| 5. |
- Gezork, Tobias, et al.
(författare)
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Influence of gap detailing on calculated unsteady non-adjacent blade row aero-forcing in a transonic compressor stage
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Resonant or close to resonant forced response excitation of compressor blades limits component life time, and can potentially lead to high cycle fatigue failure if the excitingforces are large and damping is insufficient. When numerically quantifying the forcing function by means of simulations,simplifications are typically made in the analysis to reducecomplexity and computational cost. In this paper we numerically investigate how the blade forcing function is influencedby the rotor tip gap flow and by flow across gaps in the upstream VIGV row. Unsteady simulations are made using a testrig geometry where a forcing crossing with an excitation froma non-adjacent blade row had previously been measured. Theeffects of the gaps on the forcing function for the first torsionmode are presented for both the non-adjacent blade row excitation (changes compared with a case without gaps indicating a 20% reduction) and an adjacent excitation (changes indicating an80% increase in terms of forcing function amplitude comparing with a case without gaps).
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| 6. |
- Gezork, Tobias, et al.
(författare)
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Influence of Gap Detailing on Calculated Unsteady Non-Adjacent Blade Row Aero-Forcing in a Transonic Compressor Stage
- 2020
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Ingår i: Journal of turbomachinery. - : ASME International. - 0889-504X .- 1528-8900. ; 142:11
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Tidskriftsartikel (refereegranskat)abstract
- Resonant or close to resonant forced response excitation of compressor blades limits component life time and can potentially lead to high-cycle fatigue failure if the exciting forces are large and damping is insufficient. When numerically quantifying the forcing function by means of simulations, simplifications are typically made in the analysis to reduce complexity and computational cost. In this paper, we numerically investigate how the blade forcing function is influenced by the rotor tip gap flow and by flow across gaps in the upstream variable inlet guide vane row. Unsteady simulations are made using a test rig geometry where a forcing crossing with an excitation from a non-adjacent blade row had previously been measured. The effects of the gaps on the forcing function for the first torsion mode are presented for both the non-adjacent blade row excitation (changes compared with a case without gaps indicating a 20% reduction) and an adjacent excitation (changes indicating an 80% increase in terms of forcing function amplitude comparing with a case without gaps).
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| 7. |
- Gezork, Tobias
(författare)
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The Influence of Flow Leakage Modelling on Turbomachinery Blade Forcing Predictions
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Vibrations in turbomachinery engine components are undesirable as they put the structural integrity of the components at risk and can lead to failure during the lifetime of the turbomachinery engine. Vibrations arising from aerodynamic forces and stability of turbomachinery blades is assessed in the discipline of aeromechanics. Ultimately, aeromechanical considerations limit turbomachinery designs and impose constraints on innovative aerodynamic designs with highly loaded light-weight components. Besides, aeromechanical assessment of blade vibration is done at a late stage of the design process and the number of iterations in the design loop is limited. Aeromechanical calculations can have large uncertainties in the prediction accuracy, especially when made a-priori without test data or without comparable design experience to tune the analysis methods. Therefore, large safety margins are required in the design, given that only a small set of prototype engines of a chosen design can be manufactured for testing. This may result in unnecessarily conservative engines and inhibit efficient or cost-effective design.Accurate prediction methods together with a reliable estimate of the accuracy and sensitivity of the calculations will allow designers to push the limits and to design machines with highly efficient components. Efficiency directly translates into savings in terms of operational cost, capital cost as well as reductions in emissions when fuels are used.In the presented work the sensitivity of aerodynamic forcing to the geometry features of a tip gap, hub cavity, tip-shroud cavity and inlet guide vane partial gaps has been investigated by the means of URANS CFD computations. The results indicate that sensitivity is both feature and case dependent, and that the detailing features can significantly alter the aerodynamic forcing function. The work shows, that the features should be included in high-fidelity aerodynamic models used for aeromechanics and highlights the mechanisms in which the features affect the aeromechanic forcing.Investigations were performed for a subsonic model steam turbine configuration in 1.5 stage simulations, for a transonic turbine stage and for a 1.5 stage transonic research compressor in a 5 row investigation. Computations were performed using time domain simulations on scaled sectors of the blade rows. Results are analysed in terms of generalised modal force, and differences in the flow-field between the investigated detailing configurations are highlighted, marking the influence of the detailing features.
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| 8. |
- Gutierrez, Mauricio, et al.
(författare)
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A Mistuned Forced Response Analysis of an Embedded Compressor Blisk Using a Reduced-Order Model
- 2019
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Ingår i: Journal of engineering for gas turbines and power. - : ASME International. - 0742-4795 .- 1528-8919. ; 141:3
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Tidskriftsartikel (refereegranskat)abstract
- Accuracy when assessing mistuned forced response analyses is still a major concern. Since a fully coupled analysis is still very computational expensive, several simplifications and reduced-order models (ROMs) are carried out. The use of a reduction method, the assumptions and simplifications, generate different uncertainties that challenge the accuracy of the results. Experimental data are needed for validation and also to understand the propagation of these uncertainties. This paper shows a detailed mistuned forced response analysis of a compressor blisk. The blisk belongs to the Purdue Three-Stage (P3S) Compressor Research Facility. Two different stator-rotor-stator configurations of 38 and 44 upstream stator vanes are taken into consideration. Several loading conditions are analyzed at three different speed lines. A ROM known as subset nominal mode (SNM), has been used for all the analyses. This reduction takes as a basis a set of modes within a selected frequency spectrum. It can consider a complete family of modes to study the disk-blade modal interaction. A detailed comparison between the predicted and measured results has been performed, showing a good agreement for the high loading (HL) conditions.
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| 9. |
- Gutierrez Salas, Mauricio, 1982-, et al.
(författare)
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A mistuned forced response analysis of an embedded compressor blisk using a reduced order model
- 2018
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Ingår i: Proceedings of the ASME Turbo Expo 2018: Turbomachinery Technical Conference. - : ASME Press. - 9780791851159
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Konferensbidrag (refereegranskat)abstract
- Accuracy when assessing mistuned forced response analysesis still a mayor concern. Since a full coupled analysis is still verycomputational expensive, several simplifications and reduced ordermodels are carried out. The use of a reduction method, theassumptions and simplifications, generate different uncertaintiesthat challenge the accuracy in the results. Experimental dataare needed for validation and also to understand the propagationof these uncertainties. This paper shows a detailed mistunedforced response analysis of a compressor blisk. The blisk belongsto the Purdue Three-Stage(P3S) Compressor Research Facility.Two different stator-rotor-stator configurations of 38 and 44 upstreamstator vanes are taken into consideration. Several loadingconditions are analyzed at three different speed lines. A reducedorder model known as subset nominal mode (SNM), has beenused for all the analyses. This reduction takes as a basis a setof modes within a selected frequency spectrum. A detailed comparisonbetween the predicted and measured results have beenperformed, showing a good agreement for the high loading conditions.
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| 10. |
- Gutierrez Salas, Mauricio
(författare)
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Development of Accurate Reduced Order Models in a Simulation Tool for Turbomachinery Aeromechanical Phenomena
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Modern gas turbines are still vulnerable to vibrations when operated at certain speeds. This unstable environment can lead to high cycle fatigue (HCF) and damage several of the components inside the turbine. Since engineers are striving to increase the turbines’ efficiency with thinner and more complex blade shapes, these critical speeds will always be present. For these reasons, aeromechanical analyses that is the study of structural and aerodynamic forces need to be assessed with a high level of accuracy. Since this type of analysis are very computational expensive, reduced order models (ROMs) are utilized to decrease the degrees of freedom (DoF) for a faster computation without compromising the accuracy. The present work focuses on cyclic and noncyclic ROMs implemented in an already existing aeroelastic tool, with different characteristics in their condensation and ease of usage depending on the analysis. The AROMA (Aeroelastic Reduced Order Model Analysis) tool has been previously developed to predict the fatigue life of turbomachinery blades with the use of ROMs. The aim of this work has been to improve the tool in terms of accuracy, flexibility and speed, by employing additional reduction methods capable to predict forced responses analysis of large industrial-size models. The understanding of an aeroelastic phenomena would not be complete if mistuning is not considered in the analysis. A mistuned bladed-disk means that all its sectors do not share the same mass and stiffness properties, which in reality this is the case. Mistuning can be addressed as probabilistic, taking into account the manufacturing tolerances and wear of the bladed disk, or it can be assessed as deterministic, also known as intentional mistuning. The latter is achieved to increase the flutter stability by breaking the circumferential traveling waves modes due to energy confinement, and also to have a certain understanding of the forced response amplitude, which helps in designing for worst and best case scenarios. The ROMs that have been incorporated in the AROMA tool are known as the component mode synthesis (CMS) and subset nominal mode (SNM) approaches. The CMS is split into two branches, these are the fixed- and freeinterface methods known as Craig-Bampton (CB) and Craig-Chang (CC), respectively. An intensive study with numerical and experimental validation has been performed for these three reduction methods. The outcome of the study is that each of these methods have their own drawbacks and benefits depending on the aeromechanical analysis problem. The SNM showed that it produces fast computations, with high level of accuracy when the mistuning level is low. On the other hand, a novel and unique approach, Craig-Chang multisubstructuring (CCMS), demonstrated fast computations and high accuracy when the mistuning level is high.
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