Analyzing vibration of rotating blades
First Claim
1. A method of characterising the vibration of a plurality of rotating blades mounted on a rotor, the method including the steps of:
- providing a strain gauge on one of the blades;
analysing data from the strain gauge to provide information about the frequencies of vibration and the vibrationally induced stresses in that blade;
providing at least one stationary timing probe for detecting the times at which respective blades pass the probe;
analysing data from the or each timing probe to obtain information about the amplitudes and/or velocities of vibration of each of the plurality of blades;
determining the relationship between vibrationally induced stress as measured by the strain gauge and vibrational amplitude or velocity as measured by the timing probe(s) for the blade on which the strain gauge is mounted, for a particular frequency of vibration; and
assuming that the above relationship is applicable to each of the plurality of blades, calculating the vibrationally induced stress for each blade from its amplitude or velocity of vibration as measured by the timing probe(s) and the said relationship.
1 Assignment
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Accused Products
Abstract
A method of characterizing the vibration of a plurality of rotating blades (12), such as turbine blades in a gas turbine engine, includes the steps of providing a single strain gauge (16A) on a single one (12A) of the blades and providing either one or two tip timing probes (22A, 22B) on a casing surrounding the blades. The data from the strain gauge (16A) allows the vibration of the single blade (12A) to be fully characterized while the data from the tip timing probes (22A, 22B) allows the amplitudes or velocities of vibration of all the blades to be determined. The relationship between the data from the tip timing probes for the single blade (12A) and the stress data from the strain gauge may be established. This relationship may then be assumed to apply to all the blades, thus allowing the stresses induced in all the blades by the vibrations to be determined.
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Citations
13 Claims
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1. A method of characterising the vibration of a plurality of rotating blades mounted on a rotor, the method including the steps of:
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providing a strain gauge on one of the blades;
analysing data from the strain gauge to provide information about the frequencies of vibration and the vibrationally induced stresses in that blade;
providing at least one stationary timing probe for detecting the times at which respective blades pass the probe;
analysing data from the or each timing probe to obtain information about the amplitudes and/or velocities of vibration of each of the plurality of blades;
determining the relationship between vibrationally induced stress as measured by the strain gauge and vibrational amplitude or velocity as measured by the timing probe(s) for the blade on which the strain gauge is mounted, for a particular frequency of vibration; and
assuming that the above relationship is applicable to each of the plurality of blades, calculating the vibrationally induced stress for each blade from its amplitude or velocity of vibration as measured by the timing probe(s) and the said relationship. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
determining an approximate resonance frequency for a blade;
rotating the blade at a plurality of frequencies in a range from below to above the approximate resonance frequency, and at each frequency measuring the displacement of the blade from its expected position, using a timing probe;
analysing the plurality of measured displacements at the respective plurality of frequencies to provide maximum and minimum displacement values; and
comparing the maximum and minimum displacement values to provide an indication of the amplitude of the vibration of the blade.
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11. A method according to claim 1, wherein the method includes the use of two spaced timing probes, spaced between 5°
- and 20°
apart.
- and 20°
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12. Apparatus for characterising the vibration of rotating blades, the apparatus including:
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a plurality of blades mounted for rotation on a rotor and extending radially outwardly therefrom;
a casing at least partially surrounding the blades;
a strain gauge mounted on one of the blades;
at least one timing probe mounted on the casing for indicating the passage of each of the individual blades;
means for analysing data from the strain gauge to provide information about the frequencies of vibration of the blade and the vibrationally induced stresses in that blade;
means for analysing data from the at least one timing probe to obtain information about the amplitudes and/or velocities of vibration of each of the plurality of blades; and
means for determining in the relationship between vibrationally induced stress as measured by the strain gauge and vibrational amplitude or velocity as measured by the at least one timing probe for the blade on which the strain gauge is mounted for a particular frequency of vibration;
and assuming that the above relationship is applicable to each of the plurality of blades, calculating the vibrationally induced stress for each blade from its amplitude or velocity of vibration as measured by the at least one timing probe and said relationship. - View Dependent Claims (13)
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Specification