RU2598986C1 - Method of diagnostics of technical state of engine reduction gear - Google Patents

Abstract

FIELD: engines.

SUBSTANCE: invention relates to methods of technical diagnostics of weakening of an engine reduction gear elements fitting by vibration parameters during its testing or in operation and can be used during its finishing, as well as to create engine diagnostics systems. Vibration in a narrow frequency band is preliminarily measured and recorded having a dominance in the spectrum on the noise component background at the frequency of the lower boundary edge of the measurement system filter, the measured vibration range is expanded, and within the spectrum a component is identified at a frequency equal to half of the tooth frequency, the current value of amplitude of which is compared with the preset limit value, exceeded which indicates weakening of the engine reduction gear elements fitting on the shaft.

EFFECT: technical result of the invention is improvement of reliability of diagnostics of technical state of elements of the engine reduction gear due to exclusion of making a false diagnosis, as well as determining the stage of a defect occurence - during assembling, testing or in operation.

4 cl, 7 dwg

Description

The present invention relates to methods for the technical diagnosis of attenuation of the landing gear of the engine gearbox by vibration parameters during its testing or in operation and may find application in its refinement, as well as to create engine diagnostic systems.

There is a method for diagnosing the technical condition of the elements of the mechanism, in which the vibration of the equipment case and its elements is measured and recorded in the form of an amplitude-frequency spectrum, the components are identified in the spectrum at diagnostic frequencies, according to which it is concluded that there is a defect - weakening of the landing of the mechanism elements on the shaft ( Rusov VA Diagnostics of defects in rotating equipment by vibration signals 2012. Section 3.2.3.2. Weakening of the landing of the mechanism elements on the shaft, http://vibrocenter.ru/book2012_2.htm. 1999-2015 (date of treatment : 04/29/2015).

The runout of the shaft (gear) is one of the most common defects in the manufacture or assembly of gear mechanisms. This defect is understood to mean improper landing of the gear on the shaft, couplings on the pinion shaft, etc.

Errors in the manufacture or installation of gears are one of the factors causing vibration in gears, which causes the appearance of dominant components in the gear vibration spectrum at the gear frequency and its harmonics:

where f _z is the tooth frequency (frequency of reconnection of teeth), Hz;

z is the number of gear teeth;

f _BP - the frequency of rotation of the gear, Hz.

When diagnosing gear defects, it is advisable to allocate a harmonic series of frequencies that are multiples of the gear frequency f _z .

Progressive wear of the teeth of the mating gears of the diagnosed gear stage leads to a significant increase in the value of the diagnosed parameter, however, such a manifestation of the defect is also possible with other deviations from the normal engine operation, for example, violation of the gear lubrication mode. The increase in the amplitude of oscillations when a component appears in the spectrum at a frequency equal to half the tooth frequency indicates a violation of the gear lubrication regime (Genkin M.D., Sokolova A.G. Vibroacoustic diagnostics of machines and mechanisms. M.: Mechanical Engineering, 1987. P. 216-217).

Closest to the proposed one, there is a method for diagnosing the technical condition of engine gearbox elements, in which the gearbox vibration is measured and recorded in the form of an amplitude-frequency spectrum in which a component is isolated at a frequency multiple of the gear frequency, the presence of a defect is determined — attenuation of gearbox elements on the shaft is weakened and its belonging to certain elements of the gearbox (Non-destructive testing: Handbook. In 7 volumes. Under the general editorship of V.V. Klyuev. T. 7. In 2 books of Prince 2 F.Ya. Balitsky, A.V. Barkov, N.A. Barkova et al. Ibrodiagnostics. - M.: Mechanical Engineering, 2005. - S. 637-638).

Diagnostics of the technical condition is carried out in a wide frequency band of the spectrum by periodically measuring vibration information, isolating frequencies that are multiples of the tooth frequency, and the side components that are separated from them by the gear speed, by which they decide on the presence of a defect of incorrect gear landing on the shaft.

The main disadvantage of this method is the possibility of making a false diagnosis, which can lead to unreasonable cessation of engine operation, for example, unjustified early removal of the engine from testing, because the presence in the spectrum of a component at the tooth frequency and two side components spaced from it by the shaft (gear) rotational speed is also observed during normal (standard) operation of the gearbox (with the condition of its elements).

In addition, the known methods do not allow the analysis of the spectrum of the vibration signal to determine the stage of occurrence of the defect - occurred during assembly or in operating conditions.

The objective of the invention is to create a diagnostic method that allows during testing and operation of the engine (without stopping) to analyze the spectrum of the vibration signal, not only to detect at the early stage the presence of a defect in the weakening of landing gear elements, for example, a coupling half, a gear wheel on the shaft, to determine its location, but and the stage of occurrence of the defect.

The technical result to which the invention is directed is to increase the reliability of diagnostics of the technical condition of the engine gearbox elements by eliminating the false diagnosis.

An additional technical result is to determine the stage of occurrence of the defect - during assembly, during testing or in operation.

The technical result is achieved by the fact that in the method for diagnosing the technical condition of the engine gearbox elements, in which the gearbox vibration is measured and recorded in the form of an amplitude-frequency spectrum in which the component is separated at a frequency multiple of the gear frequency, the presence of a defect is determined — attenuation of the gearbox elements is attenuated by shaft and its belonging to certain elements of the gearbox, in contrast to the known, pre-measured and recorded vibration in a narrow frequency band, with dominance in the spec Against the background of the noise of the component at the frequency of the lower cutoff edge of the filter, the measurement systems expand the range of the measured vibration and isolate in the spectrum a component at a frequency equal to half the tooth frequency, the current amplitude value of which is compared with a preset limit value, after which it is concluded that the fit of the elements is weakened gear on the shaft.

If a defect is detected at the first engine starts, it is concluded that the gearbox components are weakened at the assembly stage.

If a defect is detected during testing or in operation of the engine, a conclusion is made about a weakening of the landing gear elements under operating conditions.

The conclusion that the defect belongs to certain elements of the gearbox is made by the number of teeth of the gearbox member, determined using the value of the diagnostic frequency.

The invention is illustrated by drawings, which depict:

FIG. 1 - a vibration program from a vibration transducer mounted on the gear housing during power gain;

FIG. 2 - vibration spectrum in a narrow (left) and wide (right) frequency band during normal engine operation;

FIG. 3 - vibration spectrum in a narrow (left) and wide (right) frequency band when the landing of the coupling half on the input shaft of the gearbox is weakened;

FIG. 4 is a diagram of a gearbox of a power engine;

FIG. 5 - traces of hardening on the landing conical surface of the gear;

FIG. 6 - traces of hardening on the landing conical surface of the coupling half;

FIG. 7 - traces of hardening on the end surface of the cup lock nut mounting the coupling half on the gear of the gearbox.

A method for diagnosing the technical condition of engine gearbox elements is as follows.

Preliminarily, according to the results of experimental studies, the ultimate level of vibration of the component at a frequency equal to half the tooth frequency is set. The limit level of vibration at the indicated frequency is the level at which a defect occurs - a weakening of the landing gear elements on the shaft.

During engine operation (during testing or operation), the vibration of the gearbox (housing and components) is measured in a narrow frequency band (low frequency range - up to 200-300 Hz) (Genkin M.D., Sokolova A.G. Vibroacoustic diagnostics of machines and mechanisms . - M.: Mechanical Engineering, 1987. S. 35) and register it in the form of the amplitude-frequency spectrum. Perform a search in the spectrum of the component at the frequency of the lower cutoff edge of the measurement system (vibration equipment) and monitor its amplitude. During normal operation of the gearbox (Fig. 2 left), the level of the component does not exceed the level of noise (interference). When a defect occurs, the level of the component begins to dominate (exceeds the noise level) in the spectrum (Fig. 3 on the left). In this case, the range of measurement of vibration is expanded.

Measure the vibration of the gear housing in a wide frequency band (high frequency range - from 1-2 kHz), covering the tooth frequency, and register it in the form of the amplitude-frequency spectrum. Perform a search in the spectrum of the component at the frequency of a fractional multiple tooth equal to half the tooth frequency (½f _z ) of a pair of conjugate gear elements. Observe its amplitude, if it has exceeded a pre-set limit value, conclude that there is a defect - a weakening of the landing gear elements on the shaft (Fig. 3, right). The engine is stopped for inspections and analysis of results.

During normal operation of the gearbox, the level of the component at the frequency of the lower cutoff edge in a narrow band of the spectrum does not exceed the noise level (Fig. 2, left) and in the wide band of the spectrum the component at a frequency of ½f _z does not exceed its threshold value (Fig. 2, right).

The defect belongs to certain elements of the gearbox is determined by the number of teeth of the gearbox element, determined by the formula 1. The number of teeth is a gear element (coupling half or gear), the landing of which is weakened, and thereby determine the location of the defect.

In addition, if the component at the fractional multiple tooth frequency, equal to half the tooth frequency, dominates in the spectrum of controlled vibration at the first engine starts, this indicates that at the assembly stage a sufficient joint density of the mating gear elements was not provided.

If a component at a frequency of ½f _z dominates in the spectrum of controlled vibration during testing or in engine operation, this indicates that a weakening of the fit of the gearbox elements occurred already under operating conditions.

During normal operation of the engine gearbox in a wide frequency band of the vibration spectrum, there is no component at a frequency equal to half the gear, because There is no dynamic vibration amplification at this frequency.

The method was implemented during commissioning of a power gas turbine unit with a capacity of 2.5 MW.

A band-pass filter was used, the lower cutoff of which was 12 Hz. Vibration was measured by RMS (rms value) of vibration velocity. The threshold value of the RMS vibration velocity set - 4 mm / s. The threshold value of the component at the diagnostic frequency is 40 g in units of vibration overload.

During the commissioning of the engine during testing under load, an excess of the established permissible level of vibration along the gearbox (Fig. 4) of the engine was exceeded. To find out the reasons for the increased level of vibration, the following checks were performed: external inspection, checking the tightening torque of the connection of the gearbox mounts to the frame and gearbox to the engine mounts, as well as the engine-turbogenerator transmission — no comments were found.

A measurement was made of the vibration of the gear housing of the engine during operation under load, both in the range of controlled frequencies of 30-300 Hz according to the RMS vibration speed, and unfiltered high-frequency vibration in units of vibration overload (kg) (Fig. 1).

A spectral analysis of the frequencies of increased vibrations revealed a predominance of a signal with a frequency of 12 Hz, not generated by either the engine or the gearbox. It was suggested that such an increase in the RMS of the vibration velocity at a low frequency (cutoff frequency of the lower boundary of the frequency-band filter of the vibration equipment) could be caused by overloading of the input stage of the equipment by intense high-frequency vibration when exposed to the primary vibration transducer.

During normal operation, in the absence of a component at the lower boundary of the 12 Hz bandpass filter (Fig. 2, left), the vibration overload at a frequency of 3150.9 Hz did not exceed 27.8 g (Fig. 2, right).

In the power range from 1.5 MW to 1.9 MW in the area of controlled frequencies, at frequencies generated by rotation of the power shaft 50.3 Hz, rotation of the castor wheel of the gearbox 128.6 Hz and rotation of the rotor 234.1 Hz, the RMS vibration speed did not exceed 4 mm / s, however, the spectrum was dominated by the component at the lower boundary of the frequency-band filter 12.4 Hz, the level of which exceeded the noise level (Fig. 3, left). As the analysis of high-frequency unfiltered vibration (Fig. 3, right) showed, this low-frequency component was caused by a high value of vibration overload (up to 75.3 g) at a frequency of 3150.9 Hz, equal to half the tooth frequency of the input shaft elements of the gearbox, and exceeded its limit level .

When disassembling the gearbox, the weakening of the landing gear elements was confirmed: the coupling half on the pinion shaft (Fig. 4). Traces of hardening were found on the landing conical surface of the gear (Fig. 5), on the landing conical surface of the coupling half (Fig. 6) and on the end surface of the cup lock nut of the coupling half on the gear wheel (Fig. 7). Nadirs (and looseness) were discovered already by visual inspection. The runout of the toothed ring of the coupling half on the pinion shaft was checked - it exceeded according to the requirements of the drawing. T.O. there was no interference in the conical connection of the pinion shaft and the coupling half of the power branch of the gearbox

The calculation of the number of teeth using formula 1 at the tooth frequency (3150.9 · 2): 234.1 = 26.9 showed that the landing of the coupling half (the number of teeth of which is 27) on the input shaft of the gearbox has weakened. The weakening of the landing occurred during operation and was caused by the weakening of the tightening of the coupling of the coupling half with the central gear of the gearbox, which, in turn, led to wear of the teeth of the coupling half in contact with the teeth of the central gear of the gearbox.

Restored according to the design documentation (or replaced) damaged parts of the gearbox. We conducted new tests, during which vibration was measured, and spectral analysis was performed. We made sure that there were no components indicating damage to the gearbox parts and sent the motor and gearbox into operation.

The proposed method for diagnosing the technical condition of engine gearbox elements allows one to determine, without stopping it, not only the presence of a defect and the location of its localization, but also whether it is a consequence of insufficient tightening during assembly or occurred under test or operation conditions.

Claims (4)

1. A method for diagnosing the technical condition of engine gearbox elements, in which gearbox vibration is measured and recorded in the form of an amplitude-frequency spectrum, in which a component is isolated at a frequency multiple of the gear frequency, the presence of a defect is determined — attenuation of gearbox elements on the shaft is weakened and it belongs to certain elements of the gearbox, characterized in that the vibration is previously measured and recorded in a narrow frequency band, with the component dominating in the spectrum against the background of noise at the lower frequency Measurement system filter cutoff boundaries extend the range of the measured vibration spectrum and isolated component at a frequency equal to half the tooth frequency, the current amplitude value which is compared with a predetermined limit value above which conclude the weakening elements landing gear on the shaft. 2. The method according to p. 1, characterized in that when a defect is detected at the first engine starts, it is concluded that the gearbox elements are weakened at the assembly stage. 3. The method according to p. 1, characterized in that if a defect is detected during testing or in operation of the engine, it is concluded that the gearbox elements are weakened under operating conditions. 4. The method according to p. 1, characterized in that the conclusion that the defect belongs to certain elements of the gearbox is done according to the number of teeth of the gearbox element, determined by the value of the diagnostic frequency.

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