RU2287141C2 - Method for diagnostics of oscillations of working wheel of turbo-machine - Google Patents

Abstract

FIELD: technology for diagnostics of oscillations, appearing in turbo-machines, possible broad application during creation and finalizing of axial turbines and compressors, used in aviation and power engineering.

SUBSTANCE: method includes performing registration of vibro-strains on construction elements of working wheel in each operation mode of turbo machine simultaneously with registration of signal of pulsation indicators, these signals are transformed to frequency spectrum and frequency spectrum is compared to frequency spectrum of pulsation indicators. Based on coincidence of frequencies of pulsation spectrums and vibro-strains, it is possible to determine the source of high frequency pulsations, generating vibro-strains on construction elements of working wheel, thus significantly facilitating finalization of engine construction elements.

EFFECT: possible detection of high frequency pulsations, generation vibro-strains of construction elements of working wheel.

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Description

The invention relates to the diagnosis of vibrations arising in turbomachines, and can be widely used in the creation and strength tuning of axial turbines and compressors used both in aviation and in power engineering.

A known method for diagnosing oscillations of the impeller of a turbomachine, including registering a signal of flow pulsation sensors, converting a signal to the frequency spectrum, recording the repetition frequency of the blades, observing two spectrum components symmetrically equally spaced from the repetition frequency of the blades, characterizing the vibrations of the blades with deformation waves running along the wheel, in comparison itself in the process of development of fluctuations in the magnitude of the indicated components of the spectrum and judgment based on the results of comparison about the direction of motion uschih the wheel deformation waves (RF Patent №2111469, IPC: G 01 M 15/00, F 01 D 25/04, publ 20.05.98 g.).

The disadvantage of this method is the ability to determine only the self-oscillations of the blades and vibrations from a rotating stall.

The objective of the invention is the ability to detect a source of high-frequency pulsations that generate vibratory stresses of the impeller structural elements by simultaneously registering the signal of the pulsation and vibratory stress sensors on the impeller structural elements, which greatly expands the functionality of the known method.

This task is achieved by the fact that in a method for diagnosing oscillations of the impeller of a turbomachine, including registering a signal of flow pulsation sensors and converting a signal into a frequency spectrum, at each operating mode of a turbomachine simultaneously with registering a signal of pulsation sensors, register the vibratory voltages on the components of the impeller structure, convert these signals to frequency spectrum, compare this frequency spectrum with the frequency spectrum of ripple sensors and the coincidence of the frequencies of the spectra of ripple and vibration eny judge the source of high-frequency pulsations generating resonant stresses elements impeller design.

New in the method is that, at each operation mode of the turbomachine, simultaneously with the registration of the signal of the ripple sensors, the vibratory voltages are recorded on the impeller structural elements, these signals are converted into the frequency spectrum, this frequency spectrum is compared with the frequency spectrum of the ripple sensors and the coincidence of the frequencies of the ripple and vibration voltage spectra judge the source of high-frequency pulsations generating vibro-stresses of the elements of the construction of the impeller.

Experimentally, during the refinement of low-pressure compressors of turbofan engines with wide-chord high-loaded blades, direct excitation was detected at the natural frequencies of the compressor working blades and its casing by pressure pulsations generated by the interaction between the rotor blades and the stator at different engine operating modes. These resonances led to breakdowns of the blades and the compressor housing.

Having performed at each operating mode of the turbomachine, simultaneously with the registration of the signal of the pulsation sensors, the registration of vibration stresses on the impeller structural elements, converting these signals to the frequency spectrum and comparing this frequency spectrum with the frequency spectrum of the pulsation sensors, we can determine the source of high-frequency pulsations by the coincidence of the frequencies of the spectra of pulsations and vibrations generating vibratory stresses of the impeller structural elements, which greatly facilitates the refinement of the motor structural elements la.

Figure 1 shows a device for implementing a method for diagnosing oscillations of the impeller of a turbomachine.

Figure 2 presents statistical data on the maximum amplitudes of oscillations in the spectrum:

a) pulsation flow in the compressor;

b) vibration voltage of the compressor housing;

c) vibration stresses on the working blade of the second stage of the compressor.

A device for implementing a method for diagnosing oscillations of an impeller of a turbomachine comprises a two-stage compressor housing 1 with blades of guide vanes of the first and second stages 2 and 3, a rotor 4 with impellers 5 and 6 with impellers of the first 7 and second 8 stages. Behind the impellers 5 and 6, pressure pulsation sensors 9 and 10 are installed in the compressor flow path. Vibration stress sensors 11 and 12 are installed on the housing 1 and on the working blade 8, for example, high-temperature strain gauges, which can be used to measure vibration stresses is known from the collection of articles "High-temperature load cells". M .: State. Scientific and Technical Publishing House of Engineering Literature, 1963, pp. 74-77. The outputs of the sensors 9, 10, 11 and 12 through a multi-channel amplifier 13 are connected to the input of the spectrum analyzer 14, in which the output is connected to the input of the magnetic recorder 15. The analyzer 14 and the recorder 15 can be either multi-channel or have a switch at the input to select one channel .

The method is as follows. At each engine operation mode, when the low-pressure compressor rotates with certain revolutions, the signals from the pulsation sensors 9 and 10 and vibration stresses 11 and 12 through the amplifier 13 and the spectrum analyzer 14 are recorded on the magnetic recorder 15. According to the data from the magnetic recorder 15, a plot of the amplitude is plotted pulsations and vibration stresses (according to the maximum amplitudes in the spectrum) of the frequency at all engine operating modes.

A graph of the amplitude of the ripple and vibration stresses on the compressor of the test engine on the frequency at all modes of engine operation is presented in figure 2. In Fig.2a, the pulsation amplitudes are plotted: crosses on the sensor 9 and dots on the sensor 10. In Fig.2b, the amplitudes of the body vibrations are measured on the sensor 11: crosses from pressure pulsations behind the first impeller 5 registered by the pulsation sensor 9, points from the pressure pulsations behind the second impeller 6, registered by the pulsation sensor 10. On figv shows the amplitude of the vibration stresses of the working blades of the second stage of the compressor 8 by the sensor 12: crosses from pressure pulsations behind the first impeller 5, registered sensors ripple 9, points from pressure pulsations behind the second impeller 6, registered by the pulsation sensor 10. A comparison of the graphs in figa), b) and c) shows that the vibration voltage in certain frequency ranges at different operating modes of the engine compressor as on the housing 1 and on the blade 8 arise due to the coincidence of the eigenfrequencies of the structural elements (body, blade) with the frequency of pressure pulsations generated during rotation of the compressor rotor 4. There is a resonance phenomenon, which with a very short running time on which engine operating conditions leads to a breakdown of the compressor housing and the working blades of the second stage.

The damping of pressure pulsations in certain frequency ranges makes it possible to exclude the resonance phenomenon of compressor design elements and ensure its reliable operation over the life of the engine.

Claims (1)

A method for diagnosing oscillations of the impeller of a turbomachine, including registering a signal of flow pulsation sensors and converting a signal to a frequency spectrum, characterized in that at each operating mode of a turbomachine simultaneously with registering a signal of pulsation sensors, vibratory voltages are recorded on the impeller structural elements, these signals are converted into a frequency spectrum, compare this frequency spectrum with the frequency spectrum of ripple sensors and by the coincidence of the frequencies of the spectra of ripple and vibration stresses nick high frequency pulsations generating resonant stresses elements impeller design.

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