Simplified Determination of Aerodynamic Damping for Bladed Rotors: Part 1 — Experimental Validation at Rest

Beirow, Bernd; Maywald, Thomas; Figaschewsky, Felix; Heinrich, Christoph Rocky; Kühhorn, Arnold; Giersch, Thomas

doi:10.1115/gt2016-56535

Cited by 7 publications

(7 citation statements)

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“…It could be shown in foregoing publications ( 18 , 19 ) that damping results generated in the manner indicated before represent a satisfying approximation for operational conditions in case of higher blade modes and sufficiently large distances from blade to blade. Two rotating test cases were considered in Ref.…”

Section: Experimental Modal Analysesmentioning

confidence: 88%

“…The large differences seem to be surprising; however, they can be explained with the impact of acoustic reflections between adjacent blades, which are more significant for modes emitting acoustic waves with a large wave length, as it is the case for a Mode 1 blade motion. It could be shown in foregoing publications (18,19) that damping results generated in the manner indicated before represent a satisfying approximation for operational conditions in case of higher blade modes and sufficiently large distances from blade to blade. Two rotating test cases were considered in Ref.…”

Section: Experimental Modal Analyses 41 Modal Damping Ratios and Natmentioning

confidence: 91%

“…In this way, numerous FRF could be determined, allowing for an identification of modal ratios using a multi degree of freedom (MDOF) fit approach as introduced in Ref. 18. Figure 9 clearly indicates an increasing level of modal coupling with increasing ambient pressure; and hence, the best separation of peaks is appearing at 3 mbar.…”

Section: Experimental Modal Analyses 41 Modal Damping Ratios and Natmentioning

confidence: 99%

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Model update and validation of a mistuned high-pressure compressor blisk

et al. 2019

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In order to prepare an advanced 4-stage high-pressure compressor rig test campaign, details regarding both accomplishment and analysis of preliminary experiments are provided in this paper. The superior objective of the research project is to contribute to a reliable but simultaneously less conservative design of future high pressure blade integrated disks (blisk). It is planned to achieve trend-setting advances based on a close combination of both numerical and experimental analyses. The analyses are focused on the second rotor of this research compressor, which is the only one being manufactured as blisk. The comprehensive test program is addressing both surge and forced response analyses e.g. caused by low engine order excitation. Among others the interaction of aeroelastics and blade mistuning is demanding attention in this regard. That is why structural models are needed, allowing for an accurate forced response prediction close to reality. Furthermore, these models are required to support the assessment of blade tip timing (BTT) data gathered in the rig tests and strain gauge (s/g) data as well. To gain the maximum information regarding the correlation between BTT data, s/g-data and pressure gauge data, every blade of the second stage rotor (28 blades) is applied with s/g. However, it is well known that s/g on blades can contribute additional mistuning that had to be considered upon updating structural models.Due to the relevance of mistuning, efforts are made for its accurate experimental determination. Blade-by-blade impact tests according to a patented approach are used for this purpose. From the research point of view, it is most interesting to determine both the effect s/g-instrumentation and assembling the compressor stages on blade frequency mistuning. That is why experimental mistuning tests carried out immediately after manufacturing the blisk are repeated twice, namely, after s/g instrumentation and after assembling. To complete the pre-test program, the pure mechanical damping and modal damping ratios dependent on the ambient pressure are experimentally determined inside a pressure vessel. Subsequently the mistuning data gained before is used for updating subset of nominal system mode (SNM) models. Aerodynamic influence coefficients (AICs) are implemented to take aeroelastic interaction into account for forced response analyses. Within a comparison of different models, it is shown for the fundamental flap mode (1F) that the s/g instrumentation significantly affects the forced response, whereas the impact of assembling the compressor plays a minor role.

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Section: Experimental Modal Analysesmentioning

confidence: 88%

Section: Experimental Modal Analyses 41 Modal Damping Ratios and Natmentioning

confidence: 91%

Section: Experimental Modal Analyses 41 Modal Damping Ratios and Natmentioning

confidence: 99%

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Model update and validation of a mistuned high-pressure compressor blisk

et al. 2019

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“…Comparably low magnifications ranging between 2 and 5 are found for BF 1 and 2. This can be explained by an increasing contribution of aero-acoustic interaction between adjacent blades due to their lower natural frequencies [16] .…”

Section: Experimental Modal Analysesmentioning

confidence: 99%

Vibration analysis of an axial turbine blisk with optimized intentional mistuning pattern

Beirow

Figaschewsky

Kühhorn

et al. 2019

Journal of Sound and Vibration

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Aiming to limit the forced response of an axial turbine blisk for ship Diesel engine applications efforts have been made to increase the aerodynamic damping contribution for the most critical modes. In this regard the potential of intentional mistuning is investigated since it offers the opportunity to ensure a safe operation without a severe loss of aerodynamic performance. Genetic algorithms have been chosen to derive an optimized mistuning pattern. In order to keep the manufacturing effort within a limit only two possible blade geometries are allowed which means that an integer optimization problem has been formulated. For the purpose of demonstrating the benefit of the intentional mistuning pattern found, two blisk prototypes have been manufactured: One with and another one without employing intentional mistuning for purposes of comparison. Furthermore, this offers the opportunity for an experimental determination of mistuning being really manufactured and other modal properties as well. The experimental data basis is employed to update structural models which are well suited to demonstrate the forced response reduction under operational conditions.

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“…The procedure applied here uses an optimization-aided nonlinear least square method in order to fit the frequency response function. A detailed description of this method is given in [20]. Figure 14 shows an exemplary frequency response function fit.…”

Section: Modal Parameter Identificationmentioning

confidence: 99%