| 1. |
- 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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| 2. |
- 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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| 3. |
- 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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| 4. |
- 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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| 5. |
- Lejon, Marcus, 1986, et al.
(författare)
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Multidisciplinary Design of a Three Stage High Speed Booster
- 2017
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Ingår i: ASME Turbo Expo 2017: Turbine Technical Conference and Exposition. - : ASME Press. ; 2B-2017
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Konferensbidrag (refereegranskat)abstract
- The paper describes a multidisciplinary conceptual design of an axial compressor, targeting a three stage, high speed, high efficiency booster with a design pressure ratio of 2.8. The paper is outlined in a step wise manner starting from basic aircraft and engine thrust requirements, establishing the definition of the high speed booster interface points and its location in the engine. Thereafter, the aerodynamic 1D/2D design is carried out using the commercial throughflow tool SC90C. A number of design aspects are described, and the steps necessary to arrive at the final design are outlined. The SC90C based design is then carried over to a CFD based conceptual design tool AxCent, in which a first profiling is carried out based on a multiple circular arc blade definition. The design obtained at this point is referred to as the VINK compressor. The first stage of the compressor is then optimized using an in-house optimization tool, where the objective functions are evaluated from detailed CFD calculations. The design is improved in terms of efficiency and in terms of meeting the design criteria put on the stage in the earlier design phases. Finally, some aeromechanical design aspects of the first stage are considered. The geometry and inlet boundary conditions of the compressor are shared with the turbomachinery community on a public server. This is intended to be used as a test case for further optimization and analysis.
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| 6. |
- Norton, S., et al.
(författare)
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Modelling of turbine blade vibrations via computational intelligence methods
- 2017
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Ingår i: 12th European Conference on Turbomachinery Fluid Dynamics and Thermodynamics, ETC 2017. - : European Turbomachinery Society.
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Konferensbidrag (refereegranskat)abstract
- A method for modelling turbomachine blade vibration events is proposed, based on computational intelligence algorithms. The method utilises steady thermodynamic data and blade tip-timing data to identify high amplitude vibration events and to draw underlying relationships between steady-thermodynamic input channels and resultant blade motion characteristics. Several computational studies probe specific process aspects in order to improve model prediction accuracy and several methods of data-feature reduction are established to further enhance vibration predictions. Overall, the study shows promise of what prediction capabilities can be achieved with seemingly limited instrumentation. Drawbacks in matters of tip-timing interpretation, quality/quantity of data and process limitations are discussed. Consequential future objectives are outlined to envisage onward predictive accuracy.
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| 7. |
- Pan, Minghao, et al.
(författare)
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Determination of aerodynamic damping at high reduced frequencies
- 2018
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Ingår i: Proceedings of the ASME Turbo Expo. - : ASME Press. - 9780791851159
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Konferensbidrag (refereegranskat)abstract
- In turbomachines, forced response of blades is blade vibrations due to external aerodynamic excitations and it can lead to blade failures which can have fatal or severe economic consequences. The estimation of the level of vibration due to forced response is dependent on the determination of aerodynamic damping. The most critical cases for forced response occur at high reduced frequencies. This paper investigates the determination of aerodynamic damping at high reduced frequencies. The aerodynamic damping was calculated by a linearized Navier-Stokes flow solver with exact 3D non-reflecting boundary conditions. The method was validated using Standard Configuration 8, a two-dimensional flat plate. Good agreement with the reference data at reduced frequency 2.0 was achieved and grid converged solutions with reduced frequency up to 16.0 were obtained. It was concluded that at least 20 cells per wavelength is required. A 3D profile was also investigated: an aeroelastic turbine rig (AETR) which is a subsonic turbine case. In the AETR case, the first bending mode with reduced frequency 2.0 was studied. The 3D acoustic modes were calculated at the far-fields and the propagating amplitude was plotted as a function of circumferential mode index and radial order. This plot identified six acoustic resonance points which included two points corresponding to the first radial modes. The aerodynamic damping as a function of nodal diameter was also calculated and plotted. There were six distinct peaks which occurred in the damping curve and these peaks correspond to the six resonance points. This demonstrates for the first time that acoustic resonances due to higher order radial acoustic modes can affect the aerodynamic damping at high reduced frequencies.
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| 8. |
- Qi, Di, et al.
(författare)
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Establishment of an open 3D steam turbine flutter test case
- 2017
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Ingår i: 12th European Conference on Turbomachinery Fluid Dynamics and Thermodynamics, ETC 2017. - : European Turbomachinery Society.
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Konferensbidrag (refereegranskat)abstract
- This paper introduces an open three-dimensional (3D) flutter test case for steam turbines. The test case is fully described and initial results are presented. The steam turbine last stage blading geometry is taken from a test case originally presented by Durham University. The stage is representative of the aerodynamic characteristics of modern steam turbine blading. To the authors' knowledge, this is the first time that a steam turbine flutter test case is presented based on an open 3D realistic blade geometry. ANSYS CFX and LUFT (Linearized Unsteady Flow solver for Turbomachinery) were both applied to calculate inviscid and RANS steady and unsteady flow solutions. Plots of aerodynamic damping versus inter-blade phase angle and plots of the local work coefficient on the blade for critical cases are presented.
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| 9. |
- Sun, Tianrui, et al.
(författare)
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Detached-Eddy Simulation Applied to Aeroelastic Stability Analysis in a Last-Stage Steam Turbine Blade
- 2019
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Ingår i: Journal of turbomachinery. - : ASME. - 0889-504X .- 1528-8900. ; 141:9
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Tidskriftsartikel (refereegranskat)abstract
- Blade flutter in the last stage is an important design consideration for the manufacturers of steam turbines. Therefore, the accurate prediction method for blade flutter is critical. Since the majority of aerodynamic work contributing to flutter is done near the blade tip, resolving the tip leakage flow can increase the accuracy of flutter predictions. The previous research has shown that the induced vortices in the tip region can have a significant influence on the flow field near the tip. The structure of induced vortices due to the tip leakage vortex cannot be resolved by unsteady Reynolds-averaged Navier-Stokes (URANS) simulations because of the high dissipation in turbulence models. To the best of author's knowledge, the influence of induced vortices on flutter characteristics has not been investigated. In this paper, the results of detached-eddy simulation (DES) and URANS flutter simulations of a realistic-scale last-stage steam turbine are presented, and the influence of induced vortices on the flutter stability has been investigated. Significant differences for the predicted aerodynamic work coefficient distribution on the blade surface, especially on the rear half of the blade suction side near the tip, are observed. At the least stable interblade phase angle (IBPA), the induced vortices show a destabilizing effect on the blade aeroelastic stability. The motion of induced vortices during blade oscillation is dependent on the blade amplitude, and hence, the aerodynamic damping is also dependent on the blade vibration amplitude. In conclusion, the induced vortices can influence the predicted flutter characteristics of the steam turbine test case.
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| 10. |
- Sun, Tianrui, 1996-
(författare)
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Improved Flutter Prediction for Turbomachinery Blades with Tip Clearance Flows
- 2018
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Recent design trends in steam turbines strive for high aerodynamic loading and high aspect ratio to meet the demand of higher efficiency. These design trends together with the low structural frequency in last stage steam turbines increase the susceptibility of the turbine blades to flutter. Flutter is the self-excited and self-sustained aeroelastic instability phenomenon, which can result in rapid growth of blade vibration amplitude and eventually blade failure in a short period of time unless adequately damped. To prevent the occurrences of flutter before the operation of new steam turbines, a compromise between aeroelastic stability and stage efficiency has to be made in the steam turbine design process. Due to the high uncertainty in present flutter prediction methods, engineers use large safety margins in predicting flutter which can rule out designs with higher efficiency. The ability to predict flutter more accurately will allow engineers to push the design envelope with greater confidence and possibly create more efficient steam turbines.The present work aims to investigate the influence of tip clearance flow on the prediction of steam turbine flutter characteristics. Tip clearance flow effect is one of the critical factors in flutter analysis for the majority of aerodynamic work is done near the blade tip. Analysis of the impact of tip clearance flow on steam turbine flutter characteristics is therefore needed to formulate a more accurate aeroelastic stability prediction method in the design phase.Besides the tip leakage vortex, the induced vortices in the tip clearance flow can also influence blade flutter characteristics. However, the spatial distribution of the induced vortices cannot be resolved by URANS method for the limitation of turbulence models. The Detached-Eddy Simulation (DES) calculation is thus applied on a realistic-scale last stage steam turbine model to analyze the structure of induced vortices in the tip region. The influence of the tip leakage vortex and the induced vortices on flutter prediction are analyzed separately.The KTH Steam Turbine Flutter Test Case is used in the flutter analysis as a typical realistic-scale last stage steam turbine model. The energy method based on 3D unsteady CFD calculation is applied in the flutter analysis. Two CFD solvers, an in-house code LUFT and a commercial software ANSYS CFX, are used in the flutter analysis as verification of each other. The influence of tip leakage vortex on the steam turbine flutter prediction is analyzed by comparing the aeroelastic stability of two models: one with the tip gap and the other without the tip gap. Comparison between the flutter characteristics predicted by URANS and DES approaches is analyzed to investigate the influence of the induced vortices on blade flutter characteristics.The multiple induced vortices and their relative rotation around the tip leakage vortex in the KTH Steam Turbine Flutter Test Case are resolved by DES but not by URANS simulations. Both tip leakage vortex and induced vortices have an influence on blade loading on the rear half of the suction side near the blade tip. The flutter analysis results suggest that the tip clearance flow has a significant influence on blade aerodynamic damping at the least stable interblade phase angle (IBPA), while its influence on the overall shape of the damping curve is minor. At the least stable IBPA, the tip leakage vortex shows a stabilization effect on rotor aeroelastic stabilities while the induced vortices show a destabilization effect on it. Meanwhile, a non-linear unsteady flow behavior is observed due to the streamwise motion of induced vortices during blade oscillation, which phenomenon is only resolved in DES results.
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| 11. |
- Sun, Tianrui, et al.
(författare)
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Influence of the Tip Clearance on the Aeroelastic Characteristics of a Last Stage Steam Turbine
- 2019
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Ingår i: Applied Sciences. - : MDPI. - 2076-3417. ; 9:6
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, the tip clearance effects on the aeroelastic stability of a last-stage steam turbine model are investigated. Most of the unsteady aerodynamic work contributing to flutter of the long blades of the last-stage of a steam turbine is done near the tip of the blade. The flow in this region is transonic and sensitive to geometric parameters such as the tip clearance height. The KTH Steam Turbine Flutter Test Case was chosen as the test case, which is an open geometry with similar parameters to modern free-standing last-stage steam turbines. The energy method based on 3D URANS simulation was applied to investigate the flutter characteristics of the rotor blade with five tip gap height varying from 0-5% of the chord length. The numerical results show that the global aerodynamic damping for the least stable inter-blade phase angle (IBPA) increases with the tip gap height. Three physical mechanisms are found to cause this phenomenon. The primary cause of the variation in total aerodynamic damping is the interaction between tip clearance vortex and the trailing edge shock from the adjacent blade. Another mechanism is the acceleration of the flow near the aft side of the suction surface in the tip region due to the well-developed tip leakage vortex when the tip clearance height is greater than 2.5% of chord. This causes a stabilizing effect at the least stable IBPA. The third mechanism is the oscillation of the tip leakage vortex due to the blade vibration. This has a negative influence on the aeroelastic stability.
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| 12. |
- Tian, Simeng, et al.
(författare)
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CFD-Aided Design of a Transonic Aeroelastic Compressor Rig
- 2019
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Ingår i: Journal of turbomachinery. - : ASME. - 0889-504X .- 1528-8900. ; 141:10
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents the results of computational fluid dynamics (CFD)-aided design calculations of a transonic linear cascade wind tunnel. The purpose of the wind tunnel is to generate data for the validation of numerical methods employed to calculate aerodynamic damping for forced response cases in transonic compressors. It is common for transonic wind tunnels to use transonic walls (perforated walls with controlled suction) to adjust the transonic flow in the experiment. Unfortunately, perforated walls are difficult to model in CFD simulations, and they complicate the validation process. One of the goals of the new tunnel is not to use perforated walls. The main difficulty in the design of a transonic linear cascade is achieving periodic flow for the central blades due to shock reflections from the side walls and the sensitivity of transonic flow to small changes in geometry. Other design constraints are the maximum available mass flow of 4.5 kg/s and the minimum required blade thickness of 2 mm for instrumentation. The purpose of the current CFD simulations is to determine the optimum geometry (sidewalls, tailboards, and throttle) of the tunnel with the goal of achieving near periodic flow conditions for the central blade channels at the similar condition in a typical transonic compressor.
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