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Effect of Scaling of Blade Row Sectors on the Prediction of Aerodynamic Forcing in a Highly Loaded Transonic Compressor Stage
KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
KTH, School of Industrial Engineering and Management (ITM), Energy Technology, Heat and Power Technology.
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2011 (English)In: Journal of turbomachinery, ISSN 0889-504X, Vol. 133, no 2, 021013- p.Article in journal (Refereed) Published
Abstract [en]

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.

Place, publisher, year, edition, pages
2011. Vol. 133, no 2, 021013- p.
Keyword [en]
Blade row, First harmonic, Generalized force, Geometrical scaling, Navier Stokes, Quantity of interest, Scaling ratio, Second harmonics, Stator blade, Test case, Test object, Transonic compressor, Compressors
National Category
Engineering and Technology
URN: urn:nbn:se:kth:diva-27067DOI: 10.1115/1.4000579ISI: 000283741600013ScopusID: 2-s2.0-77958571818OAI: diva2:376441
QC 20101210Available from: 2010-12-10 Created: 2010-12-06 Last updated: 2011-11-25Bibliographically approved
In thesis
1. Numerical Methods for Turbomachinery Aeromechanical Predictions
Open this publication in new window or tab >>Numerical Methods for Turbomachinery Aeromechanical Predictions
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In both aviation and power generation, gas turbines are used as key components. An important driver of technological advance in gas turbines is the race towards environmentally friendly machines, decreasing the fuel burn, community noise and NOx emissions. Engine modifications that lead to propulsion efficiency improvements whilst maintaining minimum weight have led to having fewer stages and lower blade counts, reduced distance between blade rows, thinner and lighter components, highly three dimensional blade designs and the introduction of integrally bladed disks (blisks). These changes result in increasing challenges concerning the structural integrity of the engine. In particular for blisks, the absence of friction at the blade to disk connections decreases dramatically the damping sources, resulting in designs that rely mainly on aerodynamic damping. On the other hand, new open rotor concepts result in low blade-to-air mass ratios, increasing the influence of the surrounding flow on the vibration response.


This work presents the development and validation of a numerical tool for aeromechanical analysis of turbomachinery (AROMA - Aeroelastic Reduced Order Modeling Analyses), here applied to an industrial transonic compressor blisk. The tool is based on the integration of results from external Computational Fluid Dynamics (CFD) and Finite Element (FE) solvers with mistuning considerations, having as final outputs the stability curve (flutter analysis) and the fatigue risk (forced response analysis). The first part of the study aims at tracking different uncertainties along the numerical aeromechanical prediction chain. The amplitude predictions at two inlet guide vane setups are compared with experimental tip timing data. The analysis considers aerodynamic damping and forcing from 3D unsteady Navier Stokes solvers. Furthermore, in-vacuo mistuning analyses using Reduced Order Modeling (ROM) are performed in order to determine the maximum amplitude magnification expected. Results show that the largest uncertainties are from the unsteady aerodynamics predictions, in which the aerodynamic damping and forcing estimations are most critical. On the other hand, the structural dynamic models seem to capture well the vibration response and mistuning effects.


The second part of the study proposes a new method for aerodynamically coupled analysis: the Multimode Least Square (MLS) method. It is based on the generation of distributed aerodynamic matrices that can represent the aeroelastic behavior of different mode-families. The matrices are produced from blade motion unsteady forces at different mode-shapes fitted in terms of least square approximations. In this sense, tuned or mistuned interacting mode families can be represented. In order to reduce the domain size, a static condensation technique is implemented. This type of model permits forced response prediction including the effects of mistuning on both the aerodynamic damping as well as on the structural mode localization. A key feature of the model is that it opens up for considerations of responding mode-shapes different to the in-vacuo ones and allows aeroelastic predictions over a wide frequency range, suitable for new design concepts and parametric studies.

Place, publisher, year, edition, pages
Stockholm: Royal Institute of Technology, 2011. 127 p.
Trita-KRV, ISSN 1100-7990 ; 11:08
Aeromechanics, numerical tools, methods, turbomachinery, aeroelasticity, gas turbines, vibrations
National Category
Mechanical Engineering
urn:nbn:se:kth:diva-48418 (URN)978-91-7501-135-6 (ISBN)
Public defence
2011-12-15, M2, Brinellvägen 64, KTH, Stockholm, 10:00 (English)
Turbopower, AROMA
QC 20111125Available from: 2011-11-25 Created: 2011-11-18 Last updated: 2011-11-25Bibliographically approved

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