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Vibration Characteristics and Structural Damping of Rotating Compressor Blades
KTH, School of Engineering Sciences (SCI), Aeronautical and Vehicle Engineering, MWL Structural and vibroacoustics.
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Nowadays, the increasing demand on the high efficiency energy, low fuel consumption and environment friendly leads the turbomachinery to be operating under a critical high rotation speed at high temperature and pressure. This severe operation condition will definitely increase the probability of the occurrence of the high cycle fatigue. To reduce the risk of appearing high cycle fatigue, the structural damping of turbomachinery components has to be increased. Since the structural damping is always positive while the aerodynamic damping can be negative at some situation, increasing structural damping is nevertheless an interesting field in turbomachinery research. One efficient way of increasing damping is to treat damping material over the blade surface. Traditional damping materials, such as rubber, are not applicable in the severe operation environment. Therefore, hard coating material is applied due to its high stiffness and good sustainability in rough environments.

Numerical tools are developed to predict the structural damping of a dynamic rotating blade while varying several important designing parameters. Two types of rotating blades are modeled using the Hamilton’s principle: the straight blade by plate theory and pretwisted blade by shell theory. The extended Galerkin method and Chebyshev collocation method are applied for the numerical simulation, such as modal analysis and frequency response analysis. The parametric analysis is performed with respect to rotation speed, stagger angle, pretwisted angle, aspect ratio, etc. Proportional damping isused in all dynamic models to investigate the damping characteristics of the blades.

Alternatively, a multilayer rotating blade is modeled by a high order layerwise theory, where the validated results reveal the modal damping exchanges between modes dueto frequency loci veering and the influence of the damping configurations on the total damping of the multilayered structure. Finally, a commercial finite element software isused to predict the damping of a real compressor blade treated by the hard coating while varying the coating thickness and distributions.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2012. , p. ix, 61
Series
Trita-AVE, ISSN 1651-7660 ; 2012:41
National Category
Applied Mechanics
Identifiers
URN: urn:nbn:se:kth:diva-101241ISBN: 978-91-7501-431-9 (print)OAI: oai:DiVA.org:kth-101241DiVA, id: diva2:546885
Public defence
2012-09-07, K2, Teknikringen 28, KTH, Stockholm, 10:00 (English)
Opponent
Supervisors
Funder
TrenOp, Transport Research Environment with Novel Perspectives
Note

QC 20120827

Available from: 2012-08-27 Created: 2012-08-25 Last updated: 2013-04-11Bibliographically approved
List of papers
1. A dynamic rotating blade model at an arbitrary stagger angle based on classical plate theory and the Hamilton's principle
Open this publication in new window or tab >>A dynamic rotating blade model at an arbitrary stagger angle based on classical plate theory and the Hamilton's principle
2013 (English)In: Journal of Sound and Vibration, ISSN 0022-460X, E-ISSN 1095-8568, Vol. 332, no 5, p. 1355-1371Article in journal (Refereed) Published
Abstract [en]

A dynamic model based on classical plate theory is presented to investigate the vibration behavior of a rotating blade at an arbitrary stagger angle and rotation speed. The Hamilton's principle is applied to derive the equations of motion, which are discretised by a novel implementation of the fast and efficient collocation method for rotating structures and by the traditional Extended Galerkin method. The results obtained with these methods are compared and validated with results found in the literature and from commercial finite element software. The proposed collocation method leads to a significantly lower computation time than the Extended Galerkin method for the same accuracy. The results show a good agreement with those of the finite element method. Finally, the forced response analysis is determined for two cases; a point force and a distribution force, using a proportional damping model.

Keywords
Classical plate theory, Collocation method, Computation time, Damping model, Finite element software, Forced response analysis, Hamilton's principle, Point force, Rotating blades, Rotating structures, Rotation speed, Stagger angle, Vibration behavior
National Category
Applied Mechanics
Identifiers
urn:nbn:se:kth:diva-31158 (URN)10.1016/j.jsv.2012.10.030 (DOI)000313919800013 ()2-s2.0-84871220052 (Scopus ID)
Funder
Swedish Energy Agency
Note

QC 20130215. Updated from accepted to published.

Ingår i avhandling, något modifierad

Available from: 2011-03-10 Created: 2011-03-10 Last updated: 2017-12-11Bibliographically approved
2. Dynamic modeling of a multilayer rotating blade via quadratic layerwise theory
Open this publication in new window or tab >>Dynamic modeling of a multilayer rotating blade via quadratic layerwise theory
2013 (English)In: Composite structures, ISSN 0263-8223, E-ISSN 1879-1085, Vol. 99, p. 276-287Article in journal (Refereed) Published
Abstract [en]

A novel dynamic model for a multilayer rotating blade mounted at an arbitrary stagger angle using a quadratic layerwise theory is developed to study structural dynamics of the blade, particularly damping properties, using various coating layer configurations. A reduced two-dimensional (2D) model is used to describe the dynamic behavior of each layer in the weak form, while the quadratic layerwise theory is applied to interpolate the transverse shear stresses along the thickness direction. Results of numerical simulations with the reduced 2D model are compared to the full three-dimensional (3D) model showing an excellent agreement, comparable to the cubic layerwise theory, for both modal analysis and frequency response calculations. Moreover, damping analyses are performed on two types of multilayer blades: two-layer (free damping) and three-layer (constrained layer), in both non-rotating and rotating situations, and, parametric analyses with varying coating thickness and rotation speed are carried out. It is shown that damping decreases as the rotation speed increases due to inertial and Coriolis effects. Furthermore, frequency loci veering as a result of the rotation speed is observed. The proposed model gives an efficient and accurate way to study the dynamic behavior of rotating multilayer structures, such as compressor blades.

Place, publisher, year, edition, pages
Elsevier, 2013
Keywords
Layerwise, Rotating blade, Damping, Veering
National Category
Applied Mechanics
Identifiers
urn:nbn:se:kth:diva-101238 (URN)10.1016/j.compstruct.2012.12.012 (DOI)000316769200029 ()2-s2.0-84874320232 (Scopus ID)
Note

QC 20120827

Updated from accepted to published.

Available from: 2012-08-25 Created: 2012-08-25 Last updated: 2017-12-07Bibliographically approved
3. General shell model for a rotating pretwisted blade
Open this publication in new window or tab >>General shell model for a rotating pretwisted blade
2013 (English)In: Journal of Sound and Vibration, ISSN 0022-460X, E-ISSN 1095-8568, Vol. 332, no 22, p. 5804-5820Article in journal (Refereed) Published
Abstract [en]

A novel dynamic model for a pretwisted rotating compressor blade mounted atan arbitrary stagger angle using general shell theory and including the rotationalvelocity is developed to study the eigenfrequencies and damping properties of thepretwisted rotating blade. The strain-displacement relation and constitutive modelbased on the general (thick) shell theory are applied to bring out the strain energyof the rotating blade. Using the Hamilton’s principle, the variational form of thetotal energy is derived in order to obtain the corresponding weak form for thenumerical simulation. The model is validated by comparing to literature resultsand Ansys results, showing good agreement. Parametric analyses are carried outto study the influence of the rotation velocity, the stagger angle and the radius ofthe disk on the eigenfrequencies of the pretwisted blade. Proportional dampingis included into the proposed model to investigate the influence of rotational velocityon the damping characteristics of the pretwisted rotating blade system. It isshown that, due to inertial and Coriolis eects, damping decreases as the rotation velocity increases for the lower part of the velocity range considered and eitherdecreases or increases depending on the mode order for higher velocities. Furthermore,frequency loci veering as a result of the rotation velocity is observed.The proposed model is an ecient and accurate tool for predicting the dynamicbehavior of compressor blades of arbitrary thickness, stagger angle and pretwist,potentially during the early designing stage of turbomachinery.

Place, publisher, year, edition, pages
Elsevier, 2013
Keywords
Rotating pretwisted blade, Shell theory, Damping prediction
National Category
Applied Mechanics
Identifiers
urn:nbn:se:kth:diva-101239 (URN)10.1016/j.jsv.2013.06.025 (DOI)000323361000010 ()2-s2.0-84880923598 (Scopus ID)
Funder
Swedish Energy Agency
Note

QC 20130723

Available from: 2012-08-25 Created: 2012-08-25 Last updated: 2017-12-07Bibliographically approved
4. Coating methods to increase material damping of compressor blades: measurements and modeling
Open this publication in new window or tab >>Coating methods to increase material damping of compressor blades: measurements and modeling
2010 (English)In: Proceedings of ASME Turbo Expo 2010: Vol 6, Pts A and B, ASME Press, 2010, p. 1157-1165Conference paper, Published paper (Refereed)
Abstract [en]

Methods are developed to improve damping of compressor blades, where unconstrained and constrained damping techniques are applied to the blades to increase material damping, displaying both measurement and modeling results. Two specimens, titanium and stainless steel, are treated by aluminum oxide and epoxy coating material. Measurements of material damping of simple beam specimens without and with treatments are carried out and results show that both treatments give damping increase, where aluminum treatment is more effective for damping improvement than the corresponding epoxy treatment. The unconstrained damping layer model is used to predict the total material damping of the combined structure as well as the material damping of coating layer. Comparisons with measured results are made. The constrained-layer model is also used to optimize the damping configuration and parametric analyses are performed. Two compressor blades in titanium and stainless steel are tested in air and vacuum conditions to measure material damping and results show that difference between air and vacuum situations exists. One reason is being that the radiation loss factor produced in air condition increases damping comparing with the damping in vacuum condition. The calculation of the radiation loss factor is performed to match the measurement data and results demonstrate that the radiation loss factor is one factor and air friction is another strong factor in this case. Finally, increasing material damping gives a contribution to decrease peak stress values and therefore increase the life time of compressor blades.

Place, publisher, year, edition, pages
ASME Press, 2010
Keywords
Air conditions, Air friction, Aluminum oxides, Coating layer, Coating methods, Combined structure, Compressor blades, Damping layers, Epoxy coatings, In-vacuum, Life-times, Material damping, Measured results, Measurement data, Modeling results, One-factor, Parametric analysis, Peak stress, Radiation loss, Vacuum condition
National Category
Applied Mechanics
Identifiers
urn:nbn:se:kth:diva-31159 (URN)10.1115/GT2010-23790 (DOI)000290927800117 ()2-s2.0-82055184855 (Scopus ID)978-079184401-4 (ISBN)
Conference
ASME Turbo Expo 2010: Power for Land, Sea, and Air, GT 2010; Glasgow; United Kingdom; 14 June 2010 through 18 June 2010
Note

QC 20110311

Available from: 2011-03-10 Created: 2011-03-10 Last updated: 2014-09-03Bibliographically approved

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