EP2297555A2

EP2297555A2 - Apparatus and method for determining the vibration behavior of an integrally bladed stator or rotor disk

Info

Publication number: EP2297555A2
Application number: EP10721931A
Authority: EP
Inventors: Robert Meitzner; Harald SCHÖNENBORN; Ulrich Retze
Original assignee: MTU Aero Engines GmbH
Current assignee: MTU Aero Engines AG
Priority date: 2009-02-26
Filing date: 2010-02-25
Publication date: 2011-03-23
Also published as: DE102009010375A1; WO2010097074A3; WO2010097074A2

Abstract

In a method for detecting a vibration behavior of an integrally bladed stator or rotor disk (10), a first phase relation and a second phase relation are defined. A first blade (14) of the stator or rotor disk (10) is excited using the first predetermined phase relation with a reference signal. A second blade (15) of the stator or rotor disk (10) is excited using the second predetermined phase relation with the reference signal. A vibration of the stator or rotor disk (10) is detected in a temporal relation to the reference signal.

Description

description

Apparatus and method for determining the vibration behavior of an integrally bladed stator or rotor disk

The present invention relates to an apparatus and method for detecting the vibration behavior of the individual blades of an integrally bladed stator or rotor disk and / or the entire integrally bladed stator or rotor disk for a compressor or turbine stage of a gas turbine or turbine engine for a mobile or stationary application.

Rotor disks for compressor or turbine stages of gas turbines or turbine engines for mobile or stationary applications have long been built from several separately manufactured pieces. In particular, the rotor blades were positively connected to a disc or hub. Increasingly, however, are bladed integrally

Rotor discs used, first in compressor stages, then in low-pressure turbines and now in high-pressure turbines. Sometimes, the rotor blades are manufactured separately and then materially connected to the hub, for example by means of a friction welding process. Similarly, stator disks are increasingly being inspected integrally.

In contrast to built stator or rotor disks have integrally bladed Statorbzw. Rotor disks (bladed disks, blisks in short) have a pronounced system natural vibration behavior. Since the blades of an integrally bladed stator or rotor disk never have completely identical properties, their natural frequencies differ slightly in mechanical vibrations, typically by a few percent or less. This slight scattering of the natural frequencies of not ideally equal stator or rotor blades is also referred to as mistuning. From the slightly different vibration behavior result in resonances strongly different vibration amplitudes of the individual blades. These amplitude peaks, typically by a factor of 2 to 5, but sometimes more, must be quantified on a test bench.

CONFIRMATION COPY Among other things, vibrations of a rotor disk are excited by the fact that the gas stream in which they rotate is not homogeneous and not even perfectly axisymmetric. By adjacent components, in particular upstream or downstream of the rotor disc arranged stator blades or other means of gas flow is spatially modulated. Each individual blade of the rotating rotor disk is therefore subject to varying, in particular oscillating, forces. During a full revolution of the rotor disk, all the rotor blades are exposed to approximately the same forces varying as a function of time, but depending on their position on the rotor disk at different times. In other words, the time-dependent forces on the individual rotor blades of a rotating rotor disk are out of phase with each other. The same applies to the forces acting on the individual stator blades of a stator disk.

In DE 868 674 an excitation of blade vibrations by means of an electromagnet is described. The blade vibrations are observed under stroboscopic illumination.

DE 10 2005 042 820 A1 describes a measurement of vibration distributions on a gas turbine component by means of a vibrometer.

DE 10 2006 048 791 A1 describes an excitation of mechanical vibrations of a test object. The vibrations of the test object are recorded and compared with previously detected vibrations in order to determine any damage to the test object.

In US 2002/0083772 Al (later published as US 6,679,121 B2) an excitation of vibrations of blades of a rotating rotor disk by means of a liquid jet is described.

The article "Traveling wave excitation and optical measurement techniques for non-contacting investigation of bladed disk dynamics" by JA Judge et al. describes one acoustic excitation of the blades of an integrally bladed rotor disk by means of a loudspeaker. The individual loudspeakers are driven with the same signal but delayed by different phases. As a result, the excitation of the rotor blades of a rotating rotor disk is simulated by their encounters with adjacent stator blades or other stationary components. Resultant oscillations of the rotor disk are selectively measured quantitatively by means of single-point laser vibrometry (SPLV) or qualitatively over a large area by means of speckle interferometry (English: Speckle Pattern Interferometry).

WO 2000/003197 (published in German as DE 699 34 474 T2) describes an excitation of a wave generated by a vibration excitation source and an image of the wave propagating on a diffusely reflecting surface by means of a reference wave front synchronous with the vibration excitation source is modulated. 5

An object of the present invention is to provide an apparatus, a method and a computer program for determining a vibration behavior of an integrally bladed stator or rotor disk.

o This object is solved by the subject matters of the independent claims.

Further developments are specified in the dependent claims.

Various embodiments of the present invention are based on the idea to excite 5 blades of a stator or rotor disk with different or even same predetermined phase relationships relative to a reference signal and to detect a resulting vibration of the stator or rotor disk in temporal relation to the reference signal. The temporal reference of the detection of the oscillation to the reference signal is established, for example, by the fact that discrete points in time at which measured values o are detected, one or more predetermined phase relationships (mod 2π) to the

Have reference signal. Before exciting and detecting vibrations, a vibration mode can be selected in which, for example, due to the intended installation situation in a turbomachine, the amplitudes of amplification caused by mistuning are of interest. The phase relationships associated with the individual blades are then in particular defined or selected in such a way that the selected vibration mode is essentially a blade vibration mode at the defined phase relationships and does not or not substantially have the character of a disc vibration mode.

As a measure of whether there is essentially a pure blade vibration mode or how strong the coupling of the blades is with each other, for example, the distribution of the vibration energy in the stator or rotor disk can be used. Alternatively, the phase relationships are selected so that derivatives of the eigenfrequencies do not exceed a predetermined threshold after the phase relationships.

In particular, the phase relationships are defined such that the differences in the associated phase relationships are the same for all pairs of adjacent blades. The phase relationships are then given (mod 2π) unambiguously by the number of node diameters or by the number of nodes of the spatially harmonic excitation.

In particular, if an even number of blades is evenly distributed around the circumference of the stator or rotor disk, adjacent blades with opposite phase or with a phase difference of π (Pi, corresponding to 180 degrees) can be excited. In other words, the blades are divided into two groups which are excited in opposite phase, with the blades in their circular arrangement alternately belonging to one and the other group.

With an odd number of blades, which are evenly distributed around the circumference of the stator or rotor disk, not all pairs of directly adjacent blades can be excited in opposite phase. As an approximation, however, at least some blades can be excited in phase opposition. Here, the blades are divided into two groups, which are excited in opposite phase, with almost all adjacent Shovels alternately belonging to one group and the other group. At least one pair of nearest adjacent blades must belong to the same group. The blades of the stator or rotor disk are excited with different amplitudes. The amplitude of the excitation increases from a minimum value (in particular zero) in the 5 pairs of nearest adjacent blades belonging to the same group, monotone or strictly monotone, to a maximum value in the blade opposite the pair.

With the proposed excitation in phase relationships, where a coupling between the blades is low or substantially pure blade vibration modes are excited, the natural frequencies of the individual blades in their blade vibration modes can be determined with astonishing accuracy. Surprisingly, it was found that in many cases, especially in the case of antiphase excitation of adjacent blades, a surprisingly accurate determination of the natural frequencies or resonance frequencies of the individual blades is possible. For this purpose, the blades are excited sequentially with a series of frequencies within a predetermined frequency interval. From the detected vibrations of the blades at the different frequencies, the natural or resonant frequency of each blade can be determined.

o The described excitation of adjacent blades may be advantageous regardless of whether the blades are arranged uniformly or equidistantly or at equal angular intervals on the stator or rotor disk. The method described here, in particular the excitation described here, is no longer primarily concerned with the simulation of an excitation occurring in a real turbomachine under real operating conditions, but first with the determination of the natural frequencies of the individual

Blades.

Conventionally, natural frequencies of individual blades were determined for example by means of a pulse hammer. As a rule, however, all blades except the o were dampened or detuned by means of an impact hammer in order to reduce their influence on the blade of interest. However, this damping or detuning is an intervention in the oscillatory system, which can falsify the measurement results and, above all, a high, predominantly manually generated and difficult to automate workload causes. The high workload for damping or detuning of the blades results in a very long process time, which causes high costs. With the method described here, these disadvantages can be largely avoided.

The blades can be excited successively at frequencies whose distances increase to the expected value of the natural frequency of individual blades. The expected value is known, for example, from a numerical simulation or from a preceding measurement 0 on the same or a similar stator or rotor disk.

By initially exciting with frequencies that are close to the expected value of the natural frequency, and then with frequencies whose distance from the expected value increases, must be stimulated in many cases in total with a very small number of Fre-5 quencies. The method can therefore be carried out particularly quickly.

As already mentioned, the natural frequencies of the blades o can be determined on the basis of the oscillations of the stator or rotor disk detected upon excitation with different frequencies. The amplitude amplitudes of the blades resulting from the not completely identical natural frequencies of the individual blades can be numerically determined from the natural frequencies. Thereafter, the amplitude peaks can be used as input variables for numerical simulations of an entire turbine, an axial compressor or another turbomachine, of which the stator or rotor disk 5 is a component.

The oscillation is detected, for example, by laser vibrometry, whereby the oscillation at a plurality of predetermined points or locations on the stator or o rotor disk is detected in succession-or when several laser vibrometers are used simultaneously or partly simultaneously. For this purpose, a scanning laser vibrometer can be used, as offered for example by the company Polytec in some variants. Each blade may be excited by an associated sound generator coupled to the blade via air or other fluid.

To ensure that all blades are excited with the same amplitude and as accurately as possible with the respective predetermined phase relationship, the sound generators and their upstream devices can be calibrated. For this purpose, a microphone is first brought into a defined spatial arrangement relative to a sound generator to be calibrated. A microphone is to be understood here and below as meaning any device for detecting a sound pressure and / or a phase of sound. The sound generator is controlled to produce sound that is detected by the microphone. Based on a comparison of actual and nominal values, the sound pressure and / or the phase of the sound generated by the sound generator is calibrated. Such a calibration can be done automatically. During a calibration process, each sound generator can be calibrated for several frequencies. The calibration factors thus obtained are stored, for example, in the form of an array. Alternatively or additionally, each sound generator can be calibrated for it before and / or after using a specific frequency.

Embodiments of the present invention may have a number of advantages, depending on the application. In particular, a rapid and partially or fully automated determination of the amplitude overshoot for a large frequency range and numerous phase configurations is made possible or simplified. By detecting the oscillation in temporal relation to the reference signal to which the excitations of the stator or rotor blades are in predetermined phase relationships, phase relationships between the oscillations at the individual measuring points can be detected even with a sequential sampling of many measuring points. Thus not only locally but also for the entire stator or rotor disk a quantitative and not only qualitative analysis of the vibration behavior is possible. The calibration, which can also be integrated into an automated process, enables precise excitation and thus high accuracy of the measurement results. Brief description of the figures

Embodiments will be explained in more detail with reference to the accompanying figures. Show it:

Figure 1 is a schematic representation of an apparatus for detecting a

Vibration behavior of an integrally bladed rotor disk;

Figure 2 is a schematic representation of a section of a clamping plate;

Figure 3 is a schematic representation of an excitation of a stator or rotor disk with an even number of blades;

Figure 4 is a schematic representation of an excitation of a stator or rotor disc with an odd number of blades;

Figure 5 is a schematic knot diameter diagram; and

FIG. 6 shows a schematic flowchart of a method for detecting a vibration behavior.

Description of the embodiments

1 shows a schematic representation of an integrally bladed rotor disk 10 with a plurality of rotor blades 14, 15 and a device 20 for detecting a vibration behavior of the rotor disk 10. The contours of the rotor disk 10 are shown with a broken line, since they are not part of the device 20th is. The diameter of the rotor disk 10 and the number, shape and size of the individual rotor blades 14, 15 are arbitrary and may differ significantly from the illustration in FIG. The device 20 comprises a reference signal device 30 for receiving or generating a reference signal having a predetermined frequency. Furthermore, the device 20 comprises several excitation devices 40, 50, of which only two are shown in FIG. 1 for reasons of clarity. A first excitation device 40 is associated with a first rotor blade 14, a second excitation device 50 is associated with a second rotor blade 15. For many applications, it is advantageous if the number of excitation devices 40, 50 corresponds to the number of rotor blades 14, 15 of the rotor disc 10 to be examined, and each rotor blade 14, 15 is assigned an excitation device 40, 50. In this case, for example, all exciter devices 40, 50 are the same as far as possible.

Each excitation device 40, 50 comprises a delay device 42, 52 whose input is coupled to a signal output of the reference signal device 30 in order to receive a reference signal from the reference signal device 30. An output of the delay means 42, 52 is coupled to an input of an amplifier 44, 54. An output of the amplifier 44, 54 is coupled to a sound generator 46, 56. Each sound generator 46, 56 may be circular as indicated in FIG. 1 or may have another shape. Each sound generator is for example an electrodynamic, electrostatic, magnetostatic, electromagnetic or ferroelekrischer speaker, a plasma tweeter or other electroacoustic transducer for generating sound or ultrasound. Carriers, holders or other devices for holding the sound generators 46, 56 are not shown in FIG. However, an example is shown below with reference to FIG.

Furthermore, the device 20 comprises a microphone 60 or another device for

Detecting a sound pressure and / or a phase of sound. The microphone 60 is designed to be moved to each sound generator 46, 56 or to be arranged in a predetermined spatial arrangement relative to any sound generator 46, 56. Instead of a microphone 60, a plurality of microphones may be provided, which as a rule should be calibrated at least relative to one another. The apparatus 20 further includes a scanning laser vibrometer 70 or other means for detecting the vibration of the rotor disk 10 at a plurality of measuring points 71, 72. In the case of a laser vibrometer, a laser beam 78 is successively directed to the measuring points 71, 72. The number and the arrangement of the measuring points 71, 72 can be adapted almost arbitrarily to the rotor disk 10 and the vibration behavior to be examined. To speed up the measuring process, moreover, several vibrometers 70 can be used simultaneously. A signal input of the vibrometer 70 is coupled to the reference signal output of the reference signal device 30. Although the vibrometer 70 is shown in FIG. 1 adjacent the rotor disk 10, an arrangement near the axis of the rotor disk 10 is optimal in many cases. The reference signal device 30 shown separately in FIG. 1 may be part of the vibrometer 70.

The device 20 further comprises a controller 80 having a processor 82 and a memory 84. The controller 80 is provided with the reference signal device 30, the delay devices 42, 52 and the amplifiers 44, 54 of the excitation devices 40, 50, the vibrometer 70 and optionally also coupled to the microphone 60. In the memory 84 or a plurality of memories of the controller 80, an operating system and / or a computer program (in the form of software or firmware) for running on the processor 82 and parameters of a measuring program, as shown below with reference to FIG. 6, and Calibration factors are stored. The parameters include, for example, amplitudes, frequencies and phase relationships or intervals of frequencies or phase relationships and step sizes with which these are to be changed. Calibration factors for sound pressure and / or phase can be stored, for example, in the form of an array for all sound generators 46, 56 and several frequencies.

The controller 80 is configured to control the reference signal device 30, the delay devices 42, 52, the amplifiers 44, 54 and the vibrometer 60. In particular, the controller 80 is designed to predefine the reference signal device 30 with a frequency for a reference signal in order to specify delays or phase relationships to be generated by the delay devices 42, 52 in order to be amplified by the amplifiers 44,

To set 54 to be generated gain factors, and to transmit measurement points 71, 72 and other parameters to the vibrometer 70. Furthermore, the controller 80 can be formed to receive measurement signals or measurement data from the microphone 60 and from the vibrometer 70.

FIG. 2 shows a schematic representation of a detail of a section through rotor blades 14, 15 of a rotor disk, a clamping plate 90 and sound generators 46, 56. The section shown is a section along a circular cylindrical surface parallel to the axis of a rotor disk, whose components are the rotor blades 14 , 15 are. The clamping plate 90 has a plurality of holders 92, on each of which a sound generator 46, 56 is arranged. The shape of the individual holders 92 is adapted to the rotor blades 14, 15 and their interstices. The clamping plate 90 with the brackets 92 is formed as stiff as possible and / or with vibration absorbers in order to oscillate in the method described below in the least possible extent itself.

The device 20 shown above with reference to FIGS. 1 and 2 may have a modular design, so that, for example, the number of excitation devices 40, 50 and the arrangement of the sound generators 46, 56 can be changed and adapted to different rotor disks 10. The arrangement and spatial orientation of the sound generators 46, 56 may be variable, for example, manually or servo-motor. A radial displaceability of the individual sound generators, for example on rails, can also be advantageous in the case of the calibration carried out in the context of the method described below.

Figure 3 shows a schematic representation of an excitation of a stator or rotor disk with an even number of blades. Only the sound generators 46, 56 and the amplitudes 47, 57 of the excitation by the sound generators 46, 56 are shown. The

Blades themselves are not shown in FIG. 3 for the sake of clarity. They are the sound generators, for example, as shown above with reference to FIG 2 opposite. The illustrated amplitudes 47, 57 of the excitation are not to be confused with the amplitudes of the oscillations of the blades caused by the excitation.

The illustration in FIG. 3 is indicated axonometrically; this is particularly the case with the elliptical representations of the individual sound generators and of the circle on which the Sound generator 46, 56 are arranged, recognizable. The representation of the amplitudes 47, 57 as straight lines perpendicular to the sound generators 46, 56 indicates that the maximum of the sound pressure generated by a sound generator 46, 56 is emitted in this direction. In fact, unlike the illustration in FIG. 3, the sound generators do not have to be arranged in one plane. As in the example illustrated above with reference to FIG. 2, the sound generators are instead arranged, in particular, substantially parallel to the respective associated blade.

Starting from the plane defined by the positions of the sound generators 46, 56, the bars representing the amplitudes 47, 57 alternate in opposite directions. This indicates that adjacent sound generators each excite the associated blades with opposite phase.

FIG. 4 shows a schematic representation of an excitation of a stator or rotor disk with an odd number of blades. The representation is similar to that in FIG. 3. In particular, only the sound generators 46, 56, 96, 97 and the amplitudes 47, 57 of the excitation by the sound generators 46, 56 are shown.

As in the example shown above with reference to FIG. 3, adjacent sound generators 46, 56, 96, 97 are in opposite phase. However, the amplitudes 47, 57 of the excitation are not the same for all sound generators 46, 56, 96, 97. The amplitude is maximum for one sound generator 46 and minimum or zero for two opposite sound generators 96, 97.

For N sound generators 46, 56, 96, 97 for exciting N vanes, the amount | A _n | of the amplitude A _n at the nth sound generator 46, 56, 96, 97, for example A _n = A _max (1 + cos (2π (nl) / N)) / 2, where A _{max is} the maximum amplitude of the excitation, and the sound generators 46, 56, 96, 97 are numbered consecutively from n = 1 to n = N in the order of their arrangement. In this case, the maximum amplitude A _{max is applied to} the sound generator n = 1. Alternatively, a section-wise affine-linear or any other dependence of the amplitude A _n of n is possible. The excitation shown with reference to FIG. 4 is particularly suitable for determining the eigenbzw. Resonant frequency of the blade, which is excited by the sound generator 46 with the maximum amplitude, since blades are excited in the vicinity of this blade 46 with alternating phases. In order to determine the natural frequencies of all blades, the amplitudes of sound generators 46, 47, 96, 97 are shifted to sound generators with unchanged frequency. For example, the amplitudes A _n in the time interval i A _n = A _{max are} (l + cos (2π (n + il) / N)) / 2. Also a continuous change of the amplitudes is possible.

Figure 5 is a schematic knot diameter diagram showing the natural frequencies of a plurality of different modes of a model integrally bladed rotor disk with 8 rotor blades as functions of the number of knot diameters. The abscissa is assigned the number of nodal diameters, the ordinate the frequency, in particular the natural frequency, in kHz. Since the natural frequencies are the result of a numerical simulation, they are also available for non-integer nodule diameters.

For each number of node diameters, it has also been determined for each of the illustrated modes whether the mode is predominantly a blade vibration mode or a disk vibration mode. Vane vibration modes and disk vibration modes are distinguished, for example, by the distribution of vibration energy within the rotor disk or the amount of energy exchange between rotor blades. For example, a vibration mode is referred to as a blade vibration mode if the proportion of the vibration energy attributable to the blades exceeds or does not fall below a predetermined threshold. Otherwise, the vibration mode is referred to as a disc vibration mode. Alternatively, a vibration mode is referred to as a blade vibration mode when the energy exchange between rotor blades does not exceed a predetermined threshold, otherwise as a disk vibration mode.

In Figure 5, natural frequencies of a vibration mode are shown as small squares when the vibration mode at the corresponding number of node diameters one Vane vibration mode is. If the vibration mode at the corresponding number of node diameters is a disc vibration mode, the associated natural frequency is represented as a small cross. It will be appreciated that each of the illustrated vibration modes is vane vibration mode at all or part of the illustrated values of the number of 5 node diameters for given discrimination criteria. Where the vibration modes are blade vibration modes, their natural frequencies are largely independent of the number of nodule diameters in many cases. In other words, the derivative of the natural frequency is small according to the number of knot diameters. 0

Most of the illustrated vibration modes are not predominantly blade vibration modes in an interval of values of the number of nodal diameters, but disk vibration modes. In such an interval, the natural frequency is in many cases significantly dependent on the number of knot diameters. In other words, the derivation of the natural frequency is large according to the number of knot diameters. In the illustrated knot diameter diagram, blade vibration modes and disk vibration modes can therefore also be distinguished on the basis of the local value of the derivation of the natural frequency according to the number of nodule diameters. If the magnitude of the derivative does not exceed a predetermined threshold, there is a bucket oscillation mode, otherwise a bucket oscillation mode.

If all blades have identical mechanical properties, all blades have identical natural frequencies. This state, which is never ideally reached in reality, is also referred to as a tuned state. Different mechanical properties of the 5 individual blades result in different resonance frequencies. This is also called mistuning. As already mentioned, this scattering of the resonance frequencies can lead to a concentration of vibration energy on a single or multiple blades and there to greatly increased vibration amplitudes. This amplitude increase has an effect on the service life of the blades and must be taken into account when designing a stator or rotor disk, in particular the stator or rotor blades. The different natural frequencies of the individual blades in the same vibration mode, which differ in the same blade vibration mode due to different mechanical properties, can vary to different degrees. The stronger the coupling between different blades or the more a vibration mode has the character of a disc vibration mode, the less the natural frequencies of the individual blades differ as a rule. Conversely, the natural frequencies of individual blades typically differ most clearly in the number of nodule diameters at which the vibration mode is most pronounced blade vibration mode.

Therefore, for detection of the slightly different natural frequencies of the individual blades, it may be advantageous to excite the stator or rotor disk at a number of node diameters at which the vibration mode is as pronounced as possible blade vibration mode.

FIG. 6 shows a schematic flowchart of a method for detecting a vibration behavior of an integrally bladed rotor disk or a similar component of a compressor, a turbine or another component of a gas turbine or a turbine engine. Although this method can also be implemented with devices and devices other than those described above with reference to FIGS. 1 and 2, reference numerals from FIGS. 1 and 2 are used by way of example in order to improve the comprehensibility of the text.

In a first step 101, a vibration mode is selected, in particular a blade vibration mode, for which the amplitude peak resulting from the properties of the blades 14, 15 which are not ideally identical is to be determined. For example, vibration modes of a rotor disk 10 are referred to as blade vibration modes, in which the vibration energy (oscillating between elastic energy and kinetic energy) is located substantially at the individual rotor blades 14, 15. This is accompanied by a low coupling or a low energy transfer between the individual rotor blades 14, 15. The disc vibration modes are vibration modes in which a significant proportion of the vibration tion energy in the rotor disk between the rotor blades 14, 15 is located. In a disc vibration mode, the individual rotor blades 14, 15 are strongly coupled with each other, and an energy exchange between the individual rotor blades 14, 15 is possible.

5

As already indicated blade vibration modes and disc vibration modes can be distinguished by means of a quantitative criterion. For example, the proportion of the rotor blades 14, 15 is considered in terms of the total vibration energy (oscillating elastic and kinetic energy) of the rotor disk 10. For this purpose, limits l o of the rotor blades 14, 15 can be defined, for example the inner edges of the blades. This proportion of the rotor blades 14, 15 at the vibration energy is compared with a predetermined threshold. If, in a considered vibration mode, the proportion of the rotor blades 14, 15 at the vibration energy exceeds the predetermined threshold value, the vibration mode is referred to as a blade vibration mode.

15 net, otherwise as disk vibration mode.

Alternatively, the energy flow or the energetic coupling between individual rotor blades 14, 15 is determined (for example in a numerical simulation) and compared with a predetermined threshold value. In a vibration mode 20 under consideration, if the energy flow does not exceed the predetermined threshold, the vibration mode is referred to as a blade vibration mode, otherwise as a disk vibration mode.

In a second step 102, phase relationships are defined. In particular, a phase relationship is defined for each rotor blade 14, 15 of the rotor disk 10 to be examined. The frequency and the phase relationships result from the number of rotor blades 14, 15 of the rotor disk 10, from the number and arrangement of the stator blades or other devices, which are arranged in an intended use of the rotor disk 10 in the vicinity, in particular upstream, and from a fictitious rotational speed of the rotor disk 10. Alternatively, regardless of the intended installation situation of the rotor disk in a turbomachine, the phase relationships are selected so that a coupling between the individual rotor blades 14, 15 does not exceed a predetermined threshold, or if the vibration mode selected in the first step 101 is a blade vibration mode using the described criteria and not a disk vibration mode. In many but not necessarily all cases, suitable phase relationships will be such that adjacent rotor blades 14, 15 are respectively excited with opposite phase or with a phase difference of π or 180 degrees.

In a third step 103, a frequency is defined at which the vibration behavior of the rotor disk 10 is to be detected. In particular, an expected value of the natural frequency of the vibration mode selected in the first step 101 is determined, for example on the basis of a numerical simulation of the rotor disk 10 or on the basis of measurements already carried out on the rotor disk 10 or a rotor disk of the same type.

In a fourth step 104, a reference signal is generated with the frequency defined in the third step 103, for example by a reference signal device 30.

In a fifth step 105, sound is generated by a sound generator 46, 56 in accordance with the reference signal, in particular with the frequency defined in the first step 101. In a sixth step 106, this sound is detected by a microphone 60 or other device for detecting a sound pressure and / or a phase of sound. In a seventh step 107, a calibration factor for the sound pressure or the phase is determined. The calibration factor, for example, enters the delay of the reference signal generated by the associated delay device 42, 52 or the gain of the delayed reference signal generated by the associated amplifier 44, 54. The calibration factor is determined, for example, by changing it until the sound pressure or the phase of the sound detected by the microphone 60 corresponds to a predetermined desired value. In this case, the fifth step 105, the sixth step 106, and the seventh step 107 are continuously performed simultaneously. The fifth step 105, the sixth step 106, and the seventh step 107 may be performed successively or partially or completely simultaneously for all the sound generators 46, 56. The fifth step 105, the sixth step 106, and the seventh step 107 may be performed simultaneously for a plurality of sound generators, respectively, if a corresponding plurality of microphones or other means for detecting sound pressure and / or phase of sound are provided. To perform the fifth step 105, the sixth step 106, and the seventh step 107, the rotor disk 10 is removed from the mounting plate 90 in a purely translatory or helical motion to allow the microphone 60 to be positioned opposite the sound generator 46, 56 , Alternatively, the sound generator 46, 56 to be calibrated is moved, for example, on a rail radially outwards to a point outside the circumference of the rotor disk 10.

At an eighth step 108 and a ninth step 109, the rotor blades 14, 15 of the rotor disk 10 are excited by the sound generators 46, 56 with the same or different predetermined phase relationships to the reference signal. In particular, a first rotor blade 14 having a first phase relationship to the reference signal defined at the second step 102 and a second rotor blade 15 having a second phase relationship to the reference signal defined at the second step 102 are excited. Particularly realistic results are obtained if all rotor blades 14, 15 are excited simultaneously with predetermined phase relationships to the reference signal.

At a tenth step 110, a resulting vibration of the rotor disk 10 is detected, for example by means of a scanning laser vibrometer 70. The vibration of the rotor disk is detected in temporal relation to the reference signal. This temporal reference is in particular that measured values are acquired at defined points in time, which have a fixed reference to the reference signal except for whole multiples of 2π. Alternatively or additionally, the time is recorded for each measured value.

The above-described steps from the third step 103 to and including the tenth step 110 may successively for a plurality of different frequencies be repeated. The calibration at the fifth step 105, sixth step 106, and seventh step 107 may be performed as shown in FIG. 6 before the eighth step 108, the ninth step 109, and the tenth step 110 and / or after.

The above-described steps from the third step 103 to and including the tenth step 110 are performed, for example, first at the frequency corresponding to the expected value of the natural frequency of the blades, and thereafter at frequencies farther from that expected value.

At an eleventh step 111, the natural frequencies of the rotor blades 14, 15 are determined. The natural frequency of a rotor blade 14, 15 is determined in particular as the frequency at which there is a maximum of the oscillation amplitude of the rotor blade 14, 15. Once the maxima of the vibration amplitudes have been uniquely detected for all the rotor blades 14, 15, the repetition of the above-described steps from the third step 103 to and including the tenth step 110 can be stopped. Fourier transforms do not have to be performed in contrast to conventional methods.

If, after repeating the above-described steps, the natural frequencies of all the blades are determined for a plurality of frequencies, these can be used as input variables for numerical simulations or calculations. In this case, for example, in an optional twelfth step 112 amplitude amplitudes for the stator or rotor disk are determined using the natural frequencies. At an optional thirteenth step 113, the behavior of an entire turbine, axial compressor, or other turbomachine containing the rotor disk may be determined using the natural frequencies.

The present invention has been presented predominantly on the basis of a rotor disk and the detection of its vibration behavior. However, it is also applicable to a stator disk, in particular an integrally bladed stator disk, and the detection of its vibration behavior. The present invention is implementable as a method or computer program with program code for carrying out or controlling such a method when the computer program runs on a computer or a processor. Furthermore, the invention as a computer program product with on a machine-readable carrier (for example, a ROM, PROM, EPROM, EEPROM or Flash memory, a CD-ROM, DVD, HD-DVD, Blu-ray Disc, Floppy disk or hard disk) or firmware stored program code for performing one of said methods when the computer program product runs on a computer, computer or processor. Furthermore, the present invention can be used as a digital storage medium (for example ROM, PROM, EPROM, EEPROM or flash memory, CD-ROM, DVD, HD-DVD, Blu-ray Disc, floppy disk or hard disk) with electronically readable control signals, which may interact with a programmable computer or processor system to perform any of the described methods.

Further, the present invention may be implemented as a controller, wherein the controller is configured to execute one of the described methods, or wherein the controller comprises a computer program, a computer program product or a digital storage medium as described in the preceding paragraph were.

LIST OF REFERENCE NUMBERS

10 rotor disk

14 first rotor blade 15 second rotor blade

20 Device for detecting a vibration behavior

30 reference signal device

40 first excitation device

42 delay means of the first excitation means 44 amplifier of the first excitation means

46 sound generator of the first excitation device

47 amplitude of the excitation at the sound generator 46 50 second excitation device

52 delay means of the second excitation means 54 amplifiers of the second excitation means

56 sound generator of the second excitation device

57 Amplitude of the excitation at the sound generator 56 60 microphone

70 scanning laser vibrometer 71 first measuring point of the scanning laser vibrometer 70th

72 second measuring point of the scanning laser vibrometer 70th

78 laser beam

80 control

82 processor 84 memory

90 clamping plate

92 bracket

96 sound generators

97 sound generator 101 first step

102 second step

103 third step 104 fourth step

105 fifth step

106 sixth step

107 seventh step

108 eighth step

109 ninth step

110 tenth step

111 eleventh step

112 twelfth step

113 thirteenth step

Claims

Claims:

A method for detecting a vibration behavior of an integrally bladed stator or rotor disk (10), comprising the following steps:

5

Defining (102) a first phase relationship and a second phase relationship;

Exciting (108) a first blade (14) of the stator disk (10) with 0 of the first phase relationship with a reference signal;

Exciting (109) a second blade (15) of the stator disk (10) with the second phase relationship to the reference signal; 5 detecting (110) a vibration of the stator or rotor disc (10) in temporal

Reference to the reference signal.

2. Method according to the preceding claim, further comprising the following step:

o selecting (101) a blade vibration mode,

wherein, at the step of defining (102), the first phase relationship and the second phase relationship are defined so that the selected blade vibration mode at the defined phase relationships does not or not substantially have the character of a disk vibration mode.

3. Method according to the preceding claim,

wherein, at the step of defining (102), the first phase relationship and the two-theta phase relationship are defined so that in the defined phase relationships, coupling the selected blade vibration mode to a disk vibration mode does not exceed a predetermined amount.

4. The method of claim 2 or 3, wherein the phase relationships are defined so that at the defined phase relationships at least either the distribution of the vibration energy in the stator or rotor disc meets a predetermined condition or the derivatives of the natural frequencies of the

Phase relationships do not exceed a predetermined threshold.

5. The method according to any one of claims 2 to 4, wherein the adjacent blades (14, 15) are excited with opposite phase.

6. The method according to any one of the preceding claims, further comprising the following steps:

Determining (111) of natural frequencies of the blades (14, 15) on the basis of the vibrations of the stator or vibration detected when excited at different frequencies.

Rotor disk (10);

numerically determining amplitude peaks of blades (14, 15) from the determined natural frequencies.

A method according to any one of the preceding claims, wherein the vibration is detected at a plurality of predetermined points (71, 72).

8. The method according to any one of the preceding claims, wherein the vibration laser vibrometrically detected.

A method according to any one of the preceding claims, wherein the blades (14,15) are excited by sound generators (46, 56) coupled to the blades (14,15) via air or other fluid.

10. The method according to the preceding claim, further comprising the following steps: Detecting (106) sound generated by the sound generator (46, 56);

Calibrating (107) at least one of the sound pressure and the phase of the sound generated by the sound generator (46, 56).

11. The method of claim 9 or 10, wherein

successively set several different frequencies of the reference signal,

at each frequency, the steps of deferring (102) phase relationships, exciting (108, 109) blades (15), and detecting (109) vibration are performed, and

at any frequency at least either before or after the steps of the excitation

(108, 109) is calibrated by blades (15) for each sound generator (46, 56) at least one of the sound pressure and the phase of the sound produced by the sound generator (15).

12. A computer program with program code for carrying out or controlling a method according to any one of the preceding claims, when the computer program runs on a computer or a processor (82).

13. A device (20) for detecting a vibration behavior of an integrally bladed stator or rotor disk (10), comprising:

reference signal means (30) for receiving or generating a reference signal;

a first excitation device (40) for exciting a first blade (14) of the stator or rotor disc (10) with a first phase relationship to the reference signal; a second excitation device (50) for exciting a second blade (15) of the stator or rotor disc (10) with a second phase relationship to the reference signal;

a detection device (70) for detecting a vibration of the stator or rotor disk (10) in temporal relation to the reference signal.

14. The device (20) according to the preceding claim, wherein the detecting means (70) for detecting the vibration at a plurality of predetermined points (71, 72) is formed.

15. Device (20) according to any one of claims 13 to 15, wherein the detection means comprises a scanning laser vibrometer (70).

16. Device (20) according to one of claims 11 to 15, wherein each excitation device (40, 50) comprises a sound generator (46, 56) which is designed to communicate with a blade (14, 15) via air or another fluid ) to be coupled.

17. Device (20) according to the preceding claim, further comprising

a microphone (60) for detecting sound generated by a sound generator (46, 56) of excitation means (40, 50);

calibration means (80) coupled to the microphone (60) and excitation means for calibrating at least one of the sound pressure and the phase of the sound generated by a sound generator.

18. Device (20) according to any one of claims 13 to 17, further comprising a controller, which is designed for controlling or carrying out a method according to one of claims 1 to 11.

9. Device (20) according to any one of claims 13 to 18, wherein the device (20) is modular in order to allow adaptation of the device (20) on the diameter and number of blades (14, 15) of different discs (10) ,