Full Content is available to subscribers

Subscribe/Learn More  >

Frequency Analysis Performed on Compressor Blades of Two Types of Gas Turbines Using Campbell and SAFE Diagrams

[+] Author Affiliations
Saeed Bab

Niroo Research Institute, Tehran, Iran

Mohsen Behzadi, Ahmad Ahmadi, Ali Ramesh, Ali Reza Shahrabi

Turbotec, Tehran, Iran

Jalal Fathi Sola

University of Texas at Arlington, Arlington, TX

Paper No. GT2017-64108, pp. V07BT35A020; 12 pages
  • ASME Turbo Expo 2017: Turbomachinery Technical Conference and Exposition
  • Volume 7B: Structures and Dynamics
  • Charlotte, North Carolina, USA, June 26–30, 2017
  • Conference Sponsors: International Gas Turbine Institute
  • ISBN: 978-0-7918-5093-0
  • Copyright © 2017 by ASME


This paper investigates the results of a frequency analysis performed on the blades of the last three compressor stages of two different gas turbines (Case A and B). The axial compressors in A and B have ten and eleven stages, respectively. The studied stages have identical number of blades in both compressors. However turbine B has higher number of upstream vanes before each rotating stage. Turbine B is actually a modified version of A with higher power output. The manufacturer provides acceptable ranges for several natural frequencies of blades of stage No.8 to 10 in case A. One of the purposes of this study is to figure out the logic behind the abovementioned ranges.

FEM has been used in order to determine the natural frequencies of a single blade (for Campbell diagram) and bladed disk (for SAFE diagram). By surveying the results of the Campbell diagrams for blades of case A’s mentioned stages, it is concluded that the manufacturer has obtained the acceptable ranges by considering a 10% difference (at least) between single blade natural frequencies and excitation frequencies (upstream vane passage frequencies (VPF)).

On the other hand, according to Campbell diagram, there is no resonance for these blades within the operational speed while SAFE diagrams show the existence of one resonance mode within the same range. The reason of this contradiction is found to be ignoring the disk stiffness effect on the blades frequencies. A same procedure was also followed to study the critical frequencies of the blades of the last three stages of turbine B’s compressor by SAFE diagrams.

By checking the critical modes, it is concluded that these modes in case B are transferred to one or two modes higher in comparison to A which results in a much better vibrational behavior. This has been acquired by increasing the number of the upstream vanes.

In addition, in case A’s compressor, the blades of the stage No.10 have been designed with far thicker airfoils (approximately 50%) when compared to stage No.8 and 9, even though their other dimensions are almost identical. But, this fault has been corrected in turbine B and the airfoils of all three stages almost have the same thickness. To sum up, although the design of mentioned blades in turbine B looks better and more logical than A, still a more precise look at its stages bladed disk SAFE diagrams reveals another issue. In some references there are some hints that low number of critical nodal diameter (veering region) might cause high level of blade vibration due to mistuning and this means that even in turbine B the design might not be optimal. A cure could be an increase or decrease in the number of upstream vanes in order to have a higher critical nodal diameter.

Copyright © 2017 by ASME



Interactive Graphics


Country-Specific Mortality and Growth Failure in Infancy and Yound Children and Association With Material Stature

Use interactive graphics and maps to view and sort country-specific infant and early dhildhood mortality and growth failure data and their association with maternal

Citing articles are presented as examples only. In non-demo SCM6 implementation, integration with CrossRef’s "Cited By" API will populate this tab (http://www.crossref.org/citedby.html).

Some tools below are only available to our subscribers or users with an online account.

Related Content

Customize your page view by dragging and repositioning the boxes below.

Related eBook Content
Topic Collections

Sorry! You do not have access to this content. For assistance or to subscribe, please contact us:

  • TELEPHONE: 1-800-843-2763 (Toll-free in the USA)
  • EMAIL: asmedigitalcollection@asme.org
Sign In