Abstract
The complex modal testing methods developed for asymmetric rotors are briefly discussed and their performances are experimentally evaluated. For the experiments, a laboratory test rotor is excited by using a newly developed, cost effective magnetic exciter equipped with Hall sensors, which measure the excitation forces. It is concluded that the exciter system is characterized by a wide bandwidth and a high resolution for both the excitation and force measurement, and that the one-exciter/two-sensor technique for complex modal testing of asymmetric rotors is superior to the standard two-exciter/two-sensor technique in terms of practicality and realization.
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Abbreviations
- F:
-
Magnetic force
- fy, fz :
-
y- and z- direction force vectors
- g,\(\bar g\),\(\tilde g\) :
-
Complex force vectors in stationary coordinate
- g:
-
Air gap
- Gjw,\(\hat G(j\omega )\),\(\tilde G(j\omega )\):
-
Fourier transforms of g,\(\bar g\) and\(\tilde g\)
- Hgp,\(H_{\hat g\hat p} \),\(H_{\tilde g\tilde p} \):
-
Normal dFRFs
- \(H_{\hat gp} \),\(H_{g\hat p} \):
-
Reverse dFRFs of anisotropic rotors
- \(H_{\tilde gp} \),\(H_{g\tilde p} \):
-
Reverse dFRFs of asymmetric rotors
- \(\tilde H_{ik} i,k = p,g,\hat g,\tilde g\) :
-
Estimated dFRFs using unidirectional excitation
- j:
-
Imaginary number\( = \sqrt { - 1} \)
- k:
-
Stiffness of simple rotor
- p,\(\bar p\):
-
Complex displacement vectors in stationary coordinate
- P(jw),\(\hat P(j\omega )\):
-
Fourier transforms ofp and\(\bar p\)
- S ik ,\(i,k = p,g,\hat g,\tilde g\) :
-
Directional auto- and cross- spectral density functions
- y,z :
-
y- and z- directional displacement vectors
- \(\gamma _{g\hat g}^2 (\gamma _{g\tilde g}^2 )\) :
-
Directional coherence function between g,\(\bar g\) (g,\(\tilde g\))
- Ω :
-
Rotational speed
- \(F(\bar F)\) :
-
Forward (conjugate forward) mode
- \(B(\bar B)\) :
-
Backward (conjugate backward) mode
References
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Lee, CW., Kim, SK. Complex modal testing of asymmetric rotors using magnetic exciter equipped with hall sensors. KSME International Journal 15, 866–875 (2001). https://doi.org/10.1007/BF03185265
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DOI: https://doi.org/10.1007/BF03185265