TY - JOUR

T1 - Single Nodal Diameter Excitation of Turbine Blades

T2 - Experimental and Theoretical Study

AU - Hoffmann, Thomas

AU - Panning-Von Scheidt, Lars

AU - Wallaschek, Jörg

N1 - Funding Information: The investigations were conducted as part of the joint research program SchauTex in the frame of AG Turbo. The derotator measurements were supported by the German Research Foundation (DFG) by funding their subproject“Regeneration induced Mistuning” as part of the Collaborative Research Center (CRC) 871 “Regeneration of Complex Capital Goods”. The authors gratefully acknowledge Siemens AG for their support and permission to publish this manuscript. The responsibility for the content lies solely with its authors. Bundesministerium fur Wirtschaft und Energie (BMWi) as per resolution of the German Federal Parliament (No. 03424292D; Funder ID: 10.13039/501100006360). German Research Foundation (DFG) by funding their subproject“Regeneration induced Mistuning” as part of the Collaborative Research Center (CRC) 871 “Regeneration of Complex Capital Goods” (Funder ID: 10.13039/501100001659). Funding Information: The investigations were conducted as part of the joint research program SchauTex in the frame of AG Turbo. The derotator measurements were supported by the German Research Foundation (DFG) by funding their subproject“ Regeneration induced Mistuning” as part of the Collaborative Research Center (CRC) 871 “Regeneration of Complex Capital Goods”. The authors gratefully acknowledge Siemens AG for their support and permission to publish this manuscript. The responsibility for the content lies solely with its authors.

PY - 2021/9

Y1 - 2021/9

N2 - Validating simulation results of vibrating turbine blades relies on measurements of realistic or academic cyclic structures on special test rigs. In real operation the blades are excited mainly by aerodynamic forces. For measurements of blade vibration on special test rigs, the excitation should be well known. It is desirable to use excitation spectra that consist of only a few engine order excitations. Especially for nonlinear systems, unwanted excitation orders can possibly lead to nonlinear effects which may interfere with the measurement. To separate different engine orders, an innovative electromagnetic excitation device was developed at the institution to overcome the aforementioned problems. The excitation force spectrum is controlled by a variable air gap over the circumference between device and blade. Any desired engine order excitation can be realized. Additionally, by varying the devices coil current in a harmonic fashion, frequency sweeps at constant speed can be performed. In this manuscript, an extensive study of the excitation force spectrum of the device is conducted. Therefore, theoretical investigations of the expectable spectrum are given under simultaneous variation of air gap geometry and excitation current. These predictions are then validated by experiments featuring a small, academic bladed disk. The vibrations of the blades are measured. The device promises to create well predictable and controllable excitation force spectra which will improve the validation strategy in particular of nonlinear simulation tools for the prediction of turbine blade vibrations.

AB - Validating simulation results of vibrating turbine blades relies on measurements of realistic or academic cyclic structures on special test rigs. In real operation the blades are excited mainly by aerodynamic forces. For measurements of blade vibration on special test rigs, the excitation should be well known. It is desirable to use excitation spectra that consist of only a few engine order excitations. Especially for nonlinear systems, unwanted excitation orders can possibly lead to nonlinear effects which may interfere with the measurement. To separate different engine orders, an innovative electromagnetic excitation device was developed at the institution to overcome the aforementioned problems. The excitation force spectrum is controlled by a variable air gap over the circumference between device and blade. Any desired engine order excitation can be realized. Additionally, by varying the devices coil current in a harmonic fashion, frequency sweeps at constant speed can be performed. In this manuscript, an extensive study of the excitation force spectrum of the device is conducted. Therefore, theoretical investigations of the expectable spectrum are given under simultaneous variation of air gap geometry and excitation current. These predictions are then validated by experiments featuring a small, academic bladed disk. The vibrations of the blades are measured. The device promises to create well predictable and controllable excitation force spectra which will improve the validation strategy in particular of nonlinear simulation tools for the prediction of turbine blade vibrations.

UR - http://www.scopus.com/inward/record.url?scp=85126642736&partnerID=8YFLogxK

U2 - 10.1115/1.4051172

DO - 10.1115/1.4051172

M3 - Article

AN - SCOPUS:85126642736

VL - 143

JO - Journal of Engineering for Gas Turbines and Power

JF - Journal of Engineering for Gas Turbines and Power

SN - 0742-4795

IS - 9

M1 - 091028

ER -