Estimation of Turbine Blade Natural Frequencies from Casing Pressure and Vibration Measurements
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Non-contact measurement of gas turbine rotor blade vibration is a non-trivial task, with no method available which achieves this aim without some significant draw-backs. This paper presents a truly non-contact method to estimate rotor blade natural frequencies from casing vibration measurements at a single engine operating speed. An analytical model is derived to simulate the internal casing pressure in a turbine engine including the effects of blade vibration on this pressure signal. It is shown that the internal pressure inside a turbine contains measureable information about the rotor blade natural frequencies and in-turn the casing vibration response also contains this information. The results presented herein show the residual, pressure and casing vibration, spectrum can be used to determine the rotor blade natural frequencies with validation provided for the analytical model by experimental measurements on a simplified test rig. A simulated blade fault in one of the rotor blades is introduced with successful estimation of the simulated faulty blade natural frequency.
The zip file provides supplementary data to the above-cited article. The MATLAB files contain casing vibration and pressure measurements from a simplified gas turbine test rig. Author: Gareth Forbes. Measurements taken: 01/07/2010 Version number: 0. MATLAB is available from http://www.mathworks.com/products/matlab. Supplementary data licensing : This work is licensed under the Creative Commons Attribution-ShareAlike 3.0 Australia License http://creativecommons.org/licenses/by-sa/3.0/au.
Article notice: This is the author’s version of a work that was accepted for publication in Mechanical Systems and Signal Processing. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Mechanical Systems and Signal Processing 36 (2): pp. 549-561. http://dx.doi.org/10.1016/j.ymssp.2012.11.006
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Ratz, Johannes; Forbes, Gareth; Randall, Robert (2013)Currently tip timing methods are the pseudo industry standard for measuring Gas Turbine blade vibration. The physical placement of tip timing probes is however reasonably prohibitive due to the high pressure/temperature ...
Forbes, Gareth; Alshroof, O.; Randall, R. (2010)A recent research program has identified the possibility of using the analysis of casing wall pressures in the direct measurement of gas turbine rotor blade vibration amplitudes.Currently the dominant method of non-contact ...
Forbes, Gareth; Alshroof, O.; Randall, R. (2011)A recent research program has identified the possibility of using the analysis of casing wall pressures in the direct measurement of gas turbine rotor blade vibration amplitudes. Currently the dominant method of non-contact ...