| 1. |
- Fruth, Florian, et al.
(författare)
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INFLUENCE OF THE BLADE COUNT RATIO ON AERODYNAMIC FORCING PART I : HIGHLY LOADED TRANSONIC COMPRESSOR
- 2010
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Konferensbidrag (refereegranskat)abstract
- The influence of the Blade Count Ratio (BCR) on the aerodynamic forcing of a highly transonic compressor has been investigated. The focus has been put on the unsteady aerodynamics as well as mode excitability and thus High Cycle Fatigue (HCF) risk. A number of compressor stages were investigated that differed in blade count of the stator blade row. Time-resolved aerodynamic forcing results were acquired using a non-linear CFD approach. The results were decomposed into frequency content and combined with modal properties of the various components. It is found that the BCR is a key parameter to reduce generalized force and consequently vibratory HCF stresses. Furthermore a potential in avoiding and/or alleviating potential resonant crossings in the Campbell diagram is reported. The dependency of these aspects from BCR is largely non-linear and for the first time discussed in detail on the basis of a transonic compressor stage.
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| 2. |
- Fruth, Florian, et al.
(författare)
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Influence of the blade count ratio on aerodynamic forcing part II : High pressure transonic turbine
- 2012
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Ingår i: Proceedings of the ASME Turbo Expo. - New York : American Society of Mechanical Engineers. - 9780791854662 ; , s. 1343-1354
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Konferensbidrag (refereegranskat)abstract
- The influence of the Blade Count Ratio (BCR) on the aerodynamic forcing of a transonic high pressure turbine has been investigated numerically. Main focus here was put on the change in unsteady aerodynamics, modal properties and the mode excitation. Using a scaling technique, six different transonic turbine stages with different numbers of scaled blades but maintained steady aerodynamics were generated and further analyzed. In the analysis a non-linear, time marching CFD solver was used and the unsteady, harmonic forces projected onto the mode shapes. For this transonic turbine the unsteady pressure at the rotor blade decreases in amplitude and spanwise distribution from low to high blade count ratios. In chordwise direction a local minimum for intermediate blade count ratios was found for the rotor and stator blades. Mode frequencies decreased monotonically with an increasing BCR. Significant mode changes for modes 5 and 6 of the different BCRs were captured using the Modal Assurance Criteria. It was found that for these transonic turbines the blade count ratio and reduced frequency are amongst others key parameters for a reduction in aerodynamic forcing. Even though an almost monotonic trend was found for the stator blade excitation, the rotor blade excitation behaves highly non-monotonic. A maximum value in excitation potential was found close to reported blade count ratio values. Optimization of certain modes is possible but case dependent, due to the non-monotonic nature. Moreover it was found that for a minor increase in upstream blade count the mean unsteady forces on the rotor blades is reduced, but the mode excitation not necessarily has to decrease.
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| 3. |
- Fruth, Florian, et al.
(författare)
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Unsteady forcing vs. efficiency - The effect of clocking on a transonic industrial compressor
- 2013
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Ingår i: ASME 2013 Fluids Engineering Division Summer Meeting. - : ASME Press. - 9780791855546 ; , s. V01AT02A010-
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Konferensbidrag (refereegranskat)abstract
- A numerical investigation on the impact of clocking on the efficiency and the aerodynamic forcing of the first 1.5 stages of an industrial transonic compressor was conducted. Using unsteady 3D Navier-Stokes equations, seven clocking positions were calculated and analyzed. Efficiency changes due to clocking were up to 0.125%, whereas modal excitation changes up to 31.7%. However, no direct correlation between the parameters of efficiency, stimulus and modal excitation was found as reported by others. It was found that potential forced response risks can be reduced by clocking, resulting only in minor efficiency penalties. Assuming almost sinusoidal behavior of efficiency and stimulus changes, as found in this investigation, both parameters can be set into correlation by using an ellipse interpolation. Direct impact of design changes on efficiency and stimulus through clocking can be deducted from that graph and quick estimations about extrema be made using only 5-6 transient simulations. Results however also stress the importance of considering modal excitation when optimizing for aerodynamic forcing, for which the ellipse interpolation is not necessarily possible. Highest efficiency is achieved with the IGV wake impinging on the stator blade leading edge at mid-span. It was found however that this alone is not a sufficient criteria in case of inclined wakes, as wake impingement at different span positions leads to different efficiencies.
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| 4. |
- Gezork, Tobias, et al.
(författare)
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Unsteady blade force computation sensitivity in a transonic turbine to rotor tip gap, hub and shroud cavity model detail
- 2015
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Ingår i: Proceedings of the 14th International Symposium on Unsteady Aerodynamics, Aeroacoustics & Aeroelasticity of Turbomachines.
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Konferensbidrag (refereegranskat)abstract
- The influence of including geometric detailing features on blade forcing predicted by CFD calculations is investigated. Various features such as rotor tip gap, rotor tip shroud cavity with substantial leakage flow and large rotor upstream hub rim cavity are investigated. The test case is based on a single stage transonic test turbine rig in which the unsteady aerodynamics and blade forcing have previously been investigated numerically.Including the tip gap and the tip shroud leakage in the computational model resulted in an overall increase in unsteady forcing. The change in forcing is mainly due to a change in secondary flow structure, but also due to a change of the stage flow condition. Conversely, it is shown that including the hub cavity in the computational model, even without the presence of purge-flow, reduces the unsteady force. Lastly, even though there are changes in unsteady blade loading, the blade response amplitude is only changed marginally (maximum 7%) due to forcing variations alone.
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| 5. |
- Gutierrez Salas, Mauricio, et al.
(författare)
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Forced Response Analysis of a Mistuned, Compressor Blisk Comparing Three Different Reduced Order Model Approaches
- 2017
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Ingår i: Journal of engineering for gas turbines and power. - : ASME Press. - 0742-4795 .- 1528-8919. ; 139:6
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Tidskriftsartikel (refereegranskat)abstract
- Accurate structural modeling of blisk mistuning is critical for the analysis of forced response in turbomachinery. Apart from intentional mistuning, mistuning can be due to the manufacturing tolerances, corrosion, foreign object damage, and in-service wear in general. It has been shown in past studies that mistuning can increase the risk of blade failure due to energy localization. For weak blade to blade coupling, this localization has been shown to be critical and higher amplitudes of vibration are expected in few blades. This paper presents a comparison of three reduced order models (ROMs) for the structural modeling of blisks. Two of the models assume cyclic symmetry, while the third model is free of this assumption. The performance of the reduced order models for cases with small and large amount of mistuning will be examined. The benefits and drawbacks of each reduction method will be discussed.
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| 6. |
- Mayorca, María A., 1983-, et al.
(författare)
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A New Reduced Order Modeling for Stability and Forced Response Analysis of Aero-Coupled Blades Considering Various Mode Families
- 2010
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Ingår i: Proceedings of ASME Turbo Expo 2010. - Glasgow, UK : ASME 2010. - 9780791844014 ; , s. 1-10
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Konferensbidrag (refereegranskat)abstract
- This paper presents the description and application of a new method for stability and forced response analyses of aerodynamically coupled blades considering the interaction of various mode families. The method, here referred as MLS (Multimode Least Square), considers the unsteady forces due to the blade motion at different modes shape families and calculates the aerodynamic matrixes by means of a least square (L2) approximations. This approach permits the prediction of mode families’ interaction with capabilities of structural, aerodynamic and force mistuning. A projection technique is implemented in order to reduce the computational domain. Application of the method on tuned and structural mistuned forced response and stability analyses is presented on a highly loaded transonic compressor blade. When considering structural mistuning the forced response amplitude magnification is highly affected by the change in aerodynamic damping due to mistuning. Analyses of structural mistuning without aerodynamic coupling might result in over-estimated or under-estimated response when the source of damping is mainly aerodynamic. The frequency split due to mistuning can cause that mode families’ interact due to reducing their frequencies separation. The advantage of the present method is that the effect of mode family interaction on aerodynamic damping and forced response is captured not being restricted to single mode families.
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| 7. |
- Mayorca, María A., et al.
(författare)
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A New Reduced Order Modeling for Stability and Forced Response Analysis of Aero-Coupled Blades Considering Various Mode Families
- 2012
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Ingår i: Journal of turbomachinery. - : ASME International. - 0889-504X .- 1528-8900. ; 134:5, s. 051008-
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Tidskriftsartikel (refereegranskat)abstract
- This paper presents the description and application of a new method for stability and forced response analyses of aerodynamically coupled blades considering the interaction of various mode families. The method, here referred as multimode least square, considers the unsteady forces due to the blade motion at different modes shape families and calculates the aerodynamic matrixes by means of a least square (L2) approximations. This approach permits the prediction of mode families' interaction with capabilities of structural, aerodynamic and force mistuning. A projection technique is implemented in order to reduce the computational domain. Application of the method on tuned and structural mistuned forced response and stability analyses is presented on a highly loaded transonic compressor blade. When considering structural mistuning the forced response amplitude magnification is highly affected by the change in aerodynamic damping due to mistuning. Analyses of structural mistuning without aerodynamic coupling might result in over-estimated or under-estimated response when the source of damping is mainly aerodynamic. The frequency split due to mistuning can cause that mode families' interact due to reducing their frequencies separation. The advantage of the present method is that the effect of mode family interaction on aerodynamic damping and forced response is captured not being restricted to single mode families.
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| 8. |
- Mayorca, María A., et al.
(författare)
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Effect of Scaling of Blade Row Sectors on the Prediction of Aerodynamic Forcing in a Highly Loaded Transonic Compressor Stage
- 2011
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Ingår i: Journal of turbomachinery. - : ASME International. - 0889-504X .- 1528-8900. ; 133:2, s. 021013-
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Tidskriftsartikel (refereegranskat)abstract
- An investigation of the sensitivity of a geometrical scaling technique on the blade forcing prediction and mode excitability has been performed. A stage of a transonic compressor is employed as a test object. A scaling ratio is defined, which indicates the amount of scaling from the original geometry. Different scaling ratios are selected and 3D Navier-Stokes unsteady calculations completed for each scaled configuration. A full-annulus calculation (nonscaled) is performed serving as reference. The quantity of interest is the generalized force, which gives a direct indication of the mode excitability. In order to capture both up- and downstream excitation effects, the mode excitability has been assessed on both rotor and stator blades. The results show that the first harmonic excitation can be predicted well for both up-and downstream excitations using moderate amounts of scaling. On the other hand, the predictions of second harmonic quantities do show a higher sensitivity to scaling for the investigated test case.
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| 9. |
- Mayorca, Maria Angelica, 1983-, et al.
(författare)
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Prediction of Turbomachinery Aeroelastic Behavior from a Set of Representative Modes
- 2012
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Ingår i: Proceedings of the ASME Turbo Expo 2011, Vol 6, Parts And B. - Vancouver, Canada : American Society of Mechanical Engineers. - 9780791854662 ; , s. 1449-1461
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Konferensbidrag (refereegranskat)abstract
- A method is proposed for the determination of the aeroelastic behavior of a system responding to mode-shapes different to the tuned in-vacuo ones, due to mistuning, mode family interaction or any other source of mode-shape perturbation. The method is based on the generation of a data base of unsteady aerodynamic forces arising from the motion of arbitrary modes and uses Least Square approximations for the prediction of any responding mode. The use of a reduced order technique allows for mistuning analyses and is also applied for the selection of a limited number of arbitrary modes. The application on a transonic compressor blade shows that the method captures well the aeroelastic properties in a wide frequency range. A discussion of the influence of the mode-shapes and frequency on the final stability response is also provided.
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| 10. |
- Mayorca, Maria Angelica, et al.
(författare)
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Prediction of Turbomachinery Aeroelastic Behavior From a Set of Representative Modes
- 2013
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Ingår i: Journal of turbomachinery. - : ASME International. - 0889-504X .- 1528-8900. ; 135:1, s. 011032-
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Tidskriftsartikel (refereegranskat)abstract
- A method is proposed for the determination of the aeroelastic behavior of a system responding to mode-shapes which are different from the tuned in vacuo ones, due to mistuning, mode family interaction, or any other source of mode-shape perturbation. The method is based on the generation of a data base of unsteady aerodynamic forces arising from the motion of arbitrary modes and uses least square approximations for the prediction of any responding mode. The use of a reduced order technique allows for mistuning analyses and is also applied for the selection of a limited number of arbitrary modes. The application of this method on a transonic compressor blade shows that the method captures the aeroelastic properties well in a wide frequency range. A discussion of the influence of the mode-shapes and frequency on the final stability response is also provided.
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