US 5,206,816 A · System and method for monitoring synchronous blade vibration

Abstract

A system and method are provided for monitoring synchronous blade vibration in a turbo-machine. At least three sensors capable of detecting the arrival of each blade are arranged about the cylinder which surrounds the tips of the blades. The location of the sensors is selected to minimize the influence of errors in the data. To this end, and to simplify the installation of the sensors into the cylinder, the sensors may be non-uniformly spaced. The location of each sensor for purposes of constructing Fourier transforms is determined using the arrival times at the blades at each sensor, expressed as a fraction of a rotor revolution. The transform matrix is constructed for a predetermined discrete set of M harmonics, so that M harmonics are analyzed simultaneously, the number of harmonics which can be simultaneously analyzed is related to the number of sensors used. The blade arrival time data at each sensor, expressed as a fraction of a rotor revolution, is analyzed to determine the amplitude of the blade vibration at each of the harmonics selected for the set. The calculations are repeated for a variety of harmonic sets in order to accurately interpret the results in the event there is significant vibration at harmonics not included in the initial set.

Claims25

Dependent claims

A turbo-machine system comprising:

(a) a turbo-machine having a rotor having:
(i) a reference indicator,
(ii) a periphery, and
(iii) a plurality of blades spaced in a row around said periphery of said rotor, said blades having a radius R and being subject to vibration when said rotor rotates at a frequency of rotation, said vibration having components having an amplitude Dh.sub.k of vibration at a set H of M harmonics h.sub.k of said frequency of rotation of said rotor;
and
(b) a vibration monitor for monitoring said components of said vibration, said vibration monitor having:
(i) N sensors for generating a signal at an actual arrival time when each one of said blades arrives at one of said sensors, said sensors circumferentially spaced about said blade row at a spacing between each of said sensors that is not limited to uniform spacing, N being equal to 2M+1;
(ii) means, responsive to said sensor signals, for generating data representative of said actual arrival time tm.sub.i of each of said blades sensed by each of said sensors;
(iii) means for generating data representative of an expected arrival time te.sub.i at which each of said blades is expected to arrive at each of said sensors in the absence of said vibration;
(iv) means for forming a vector .DELTA.T from an equation .DELTA.T=tm.sub.i -te.sub.i ;
and
(v) means for calculating values of elements a.sub.ij of a matrix [A], having an inverse matrix [A].sup.-1, using equations:
##EQU10## (vi) means for calculating said inverse matrix [A].sup.-1 of said [A] matrix;
(vii) means for calculating values of elements d.sub.p of a vector D from an equation D=2.pi.R[A].sup.-1 .DELTA.T;
and
(viii) means for calculating said amplitude Dh.sub.k of said components of vibration at each of said harmonics h.sub.k in said set H from an equation Dh.sub.k =[d.sup.2.sub.2k-1 +d.sup.2.sub.2k ].sup.1/2.

13 more elements

In a turbo-machine having (i) a cylinder, (ii) a rotor having a periphery enclosed by said cylinder and rotating at a frequency, (iii) a plurality of blades arranged in a row about said periphery of said rotor and subject to vibration having components at harmonics of said rotational frequency of said rotor, a method for determining the amplitude of said components of said vibration for each of said blades at a set of said harmonics of said rotational frequency of said rotor, comprising the steps of:

(a) installing a reference indicator on said rotor;
(b) installing a first sensor for generating a signal when said reference indicator arrives at said first sensor;
(c) installing a set of N second sensors in said cylinder so as to be spaced circumferentially around said rotor, said spacing between said second sensors not being limited to uniform spacing, each of said second sensors having means for generating a signal when each one of said blades arrives at one of said sensors, N being an odd integer equal to at least 3;
(d) determining the angular location of each of said second sensors relative to said first sensor;
(e) selecting said set of harmonics, the number of harmonics in said set being equal to 1/2(N-1);
(f) rotating said rotor at a first speed, whereby each of said blades arrives at each of said second sensors and said reference indicator arrives at said first sensor,
(g) determining arrival time data for each of said blades at each of said second sensors relative to an arrival time of said reference indicator at said first sensor;
(h) normalizing said arrival time data for each revolution of said rotor by sensing the period of time between two consecutive arrivals of said reference indicator at said first sensor and dividing said arrival times by said time period;
(i) determining the Fourier transform matrix for transforming said arrival time data into a frequency domain using said angular locations determined in step (d) and said set of harmonics selected in step (e);
(j) forming said arrival time data determined in step (g) into a vector and multiplying by said Fourier transform matrix determined in step (i) to arrive at a blade-tip displacement vector;
and
(k) determining said amplitudes of said components of vibration at said selected set of harmonics based on said blade-tip displacement vector.

9 more elements

Dependencies are inferred from the claim text.

System and method for monitoring synchronous blade vibration

Life of this patent

System and method for monitoring synchronous blade vibration

Life of this patent

Abstract

Claims25