RU2110054C1 - Method of diagnostics of turbomachine transmission bearings and device intended for its realization - Google Patents

Abstract

FIELD: diagnostics of turbomachines. SUBSTANCE: in "Training" mode, vibration pickup is positioned on mechanical oscillating element. The latter is installed in motor, and range of motor shaft rotational frequency from f_min to f_max is determined when motor shaft rotates within f frequency range from Δf to (Δf≤f_min), with motor rotational frequency varying in steps of f₁ which is less than or equal to minimum frequency f₂ of motor shaft rotation. Rigidity and coordinates of reference points of mechanical oscillating element are also determined. At these points difference of any two amplitudes A_i,A_k of vibration pickup oscillations ΔA for "standard" bearing is considerably less than minimum amplitude of vibration pickup oscillations (ΔA = A_i-A_k≪ A_min for given "standard" bearing. Oscillation amplitude of vibration pickup for given "standard" bearing is taken for maximum permissible amplitude A_m.p.. In diagnostics mode vibration pickup is placed on mechanical oscillating element with rigidity and coordinates of reference points determined in "Training" mode. Mechanical oscillating element is installed in motor with bearing under test, motor shaft is rotated at frequency f being within the range of f₁ to f₂, and vibration pickup oscillation amplitude is measured. If amplitude is below maximum permissible oscillation amplitude A_m.p. of vibration pickup, bearing is fit for further operation. If oscillation amplitude exceeds maximum permissible oscillation amplitude A_m.p. of vibration pickup or is equal to it, bearing under test must be rejected. Device intended for method realization has series-connected vibration pickup, amplifier and indicator. It is provided with n(n≥1) mechanical oscillating elements. Every mechanical oscillating element carries vibration pickup, first feedback resistor, n second feedback resistors, decoder with n outputs and m(m≥1) inputs. Vibration pickups are provided with permanent storages, m outputs of which are connected to decoder inputs. Decoder outputs are connected to first leads of second feedback resistors, the second lead of which are combined and connected to first lead of first feedback resistor and to second input of amplifier, the output of which is connected to second lead of first feedback resistor. EFFECT: more reliable diagnostics.

Description

 The invention relates to vibro-acoustic diagnostics of turbomachines, mainly rolling bearings of aircraft gas turbine engines (GTE).

 A known method for diagnosing defects of rolling bearings by measuring the average value of vibrations [1]. A defective bearing is considered as a generator of vibrational noise (random oscillations), the frequency composition of which is concentrated in a certain frequency range. The vibration sensor is mounted directly on the bearing support and the average frequency value is measured regardless of the amplitude of the vibrations. A change in the average frequency value indicates the occurrence and development of defects in the bearings.

 This method cannot be used to diagnose the transmission bearings of turbomachines, since direct contact with the surface of the bearing housing is required. In addition, a change in the average frequency value begins with a strongly developed defect in the bearings, i.e. the method does not have the necessary sensitivity, which excludes the use of this method for the diagnosis of aircraft engines.

 A device for vibration diagnostics of bearings, comprising a vibration sensor, amplifier, multiplication unit, a cyclic device, comparison circuits, generators, matching circuits, switches, blocks of determining the probability of a bearing defect, input blocks of the probability of a bearing defect, memory blocks, amplifiers with variable gain, threshold blocks and digital indicators [2].

 This device is intended to implement a method for diagnosing bearings, which is as follows.

 In the "Training" mode, the frequencies characterizing certain types of defects and their corresponding levels are determined by the "reference" bearing with technological defects or with assembly defects, which are aligned using amplifiers with variable amplification factors, and in the diagnostic mode, using the threshold blocks, compare the current values voltages corresponding to certain information frequencies, with the reference voltage of the threshold blocks. The voltage difference serves as the basis for predicting defective bearing operation.

 The disadvantage of this method is the low reliability of the diagnostic results, since there is a probability of missing a number of frequencies characterizing the bearing defect both in the "Training" mode and in the "Diagnostics" mode, as well as the complexity of the device for implementing the method.

 The aim of the invention is to increase the reliability of diagnostic results, as well as simplifying the device for implementing the method.

This goal is achieved by the fact that
1. in the "Training" mode, the vibration sensor is installed on a mechanical oscillating element, the mechanical oscillating element is installed in the engine and when the engine shaft rotates in the frequency range f from f _min to f _max with a discreteness of change in the frequency of rotation of the motor shaft, Δf, less than or equal to the minimum frequency ( Δf ≤ f _min ) of rotation of the motor shaft, determine the range of frequencies of rotation of the motor shaft from f ₁ to f ₂ , the rigidity and coordinates of the reference points of the mechanical oscillating element, at which the difference ΔA of any two amplitudes A _i and A _{to the} stake the vibration sensor for the "reference" bearing is much smaller than the vibration amplitude (ΔA = A _i -A _k ≪ A _min ) of the vibration sensor for this "reference" bearing, and the vibration amplitude of the vibration sensor for this "reference" bearing is taken as the maximum allowable A _p.p. and in the diagnostic mode the vibration sensor is installed on a mechanical oscillating element with the stiffness and coordinates of the reference points defined in the "Training" mode, the mechanical oscillating element is installed in the engine with the diagnosed bearing, the motor shaft is rotated with a frequency f belonging to the frequency range from f ₁ to f ₂ measure the vibration amplitude of the vibration sensor, and if the latter is less than the maximum allowable vibration amplitude of the vibration sensor A _p.p. , then the operation of the bearing is continued, and if it is greater than or equal to the maximum permissible vibration amplitude of the vibration sensor A _p.p. then the diagnosed bearing is rejected;
2. in the "Training" mode, n "standard" bearings (n ≥ 2) with various technological defects are sequentially installed in the engine, for each i-th "standard" bearing, the maximum allowable vibration amplitude of the vibration sensor A _{p.s.i is determined} , in accordance They give it intertransverse interval T _i, wherein for the "standard" bearing having a minimum geometrical dimensions of technological defects, the maximum allowable amplitude of vibration of the vibration pickup is designated as a _p.d.min minimum and calibration interval T as a Maximal ny time T _max, and a diagnostic mode for each j diagnosed bearing the measured value of the oscillation amplitude of the vibration sensor mounted calibration interval T _j;
3. in the "Diagnostics" mode, when the vibration amplitude of the vibration sensor is greater than the minimum maximum permissible vibration amplitude of the vibration sensor, indirect diagnostic methods are additionally used;
4. in the "Diagnostics" mode, when signs of defects of the bearing being diagnosed by indirect diagnostic methods appear, the vibration amplitude of the vibration sensor is measured n times (n ≥ 2) in series by n-vibration sensors, each of which is mounted on its own mechanical vibration element, and the diagnosed bearing is rejected if at least one measured vibration amplitude of the vibration sensor will exceed or be equal to the maximum permissible;
5. The device containing the vibration sensor, amplifier and indicator connected in series, is characterized in that it is equipped with mechanical oscillating elements in an amount n (n ≥ 1), each of which has a vibration sensor, a first feedback resistor, and second feedback resistors in an amount n , a decoder with the number of outputs n and with the number of inputs m (m ≥ 1), the vibration sensors are equipped with read-only memory devices with the number of outputs m that are connected to the first outputs of the second feedback resistors, the second outputs the odes of which are combined and connected to the first output of the first feedback resistor and the second input of the amplifier, the output of which is connected to the second output of the first feedback resistor.

 The advantage of the proposed method and device for its implementation in comparison with the prototype is a higher reliability of the control results, since the method and device involve working in a wide range of frequencies acting on a mechanical oscillating element, in addition, the method involves introducing a dependence of the verification interval of the diagnosed bearing on its condition , and also involves the use of indirect diagnostic methods and multiple diagnosis of the bearing when indicated Sven diagnostic methods of various mechanical oscillatory elements, which eliminates the passage of a defective bearing due to a malfunction of the diagnostic device. Compared with the prototype, the proposed device has a more simple design.

 The applicant is not aware of technical solutions containing features similar to those that distinguish the claimed solution from the prototype, which allows the claimed solution to be considered to have significant differences.

 A prototype for the implementation of the method was manufactured at the enterprise, its trial operation was carried out, and positive results were obtained on the diagnosis of transmission bearings of DZO-KU, KP engines under both the conditions of the manufacturer of the engines and operating conditions. The economic effect of the introduction can be determined after a decision is made on the volume of manufacture of devices for implementing the method.

 In FIG. 1 presents a structural diagram of the proposed device; in FIG. 2 - one of the embodiments of a mechanical oscillating element.

 The device contains mechanical oscillatory elements 1 in an amount of n (n ≥ 1), vibration sensors 2 in an amount of n, read-only memory 3 in an amount of n, a decoder 4, a first feedback resistor 5, a second feedback resistor 6 in an amount of n, an amplifier 7 and indicator 8.

 The device operates as follows.

Shock pulses arising from the interaction of rolling elements and the bearing shaft cage with bearing defects during rotation of the motor shaft act on a mechanical oscillating element 1 with a vibration sensor 2 mounted on it. The mechanical oscillating element 1 converts shock pulses into mechanical harmonic vibrations with a damped amplitude and frequency f . When the motor shaft rotates in the frequency range f ₁ to f _{2, the} excited harmonic oscillations are practically undamped.

 The vibration sensor 2 converts the mechanical harmonic vibrations into an electrical signal, which is transmitted through the amplifier 7 to the indicator 8. The amplitude of the mechanical vibrations of the mechanical vibration element 1, and hence the amplitude of the electrical signal of the vibration sensor 2, amplifier 7 and indicator 8 are directly proportional to the geometric dimensions of the defects being diagnosed bearing, i.e. the value indicated by indicator 8 unambiguously characterizes the geometric dimensions of the defects of the diagnosed bearing, i.e. his condition.

 The diagnostic method for transmission bearings consists of three modes.

 The first mode is the calibration mode.

,
где
R₁ - первый резистор 5 обратной связи;
R_2i - одно из n (1 ≤ i ≤ n) вторых резисторов 6 обратной связи,
устанавливается подбором каждого i-го второго резистора 6 обратной связи таким образом, чтобы независимо от работающего в данный момент времени в устройстве для осуществления метода механического колебательного элемента 1 и вибродатчика 2 при амплитуде колебаний A вибростенда, величины, индицируемые индикатором 8, были равны между собой.In this mode, the mechanical oscillating elements 1 are sequentially from 1 to n with vibration sensors 2 from 1 to n installed on them, and are mounted on a vibrating stand that generates mechanical vibrations in the frequency range from f ₁ to f ₂ with the oscillation amplitude A. Permanent storage devices 3 from 1 to n, carrying information about the serial number of the mechanical oscillating element 1 and the serial number of the vibration sensor 2 operating at a given time, select the corresponding second feedback resistor 6 through the decoder 4. The vibration sensor 2 currently operating converts the mechanical vibrations of the vibration stand with amplitude A into an electrical signal, which is transmitted through the amplifier 7 to the indicator 8. The transmission coefficient K _{i of the} amplifier 7, defined as

,
Where
R ₁ is the first feedback resistor 5;
R _2i is one of the n (1 ≤ i ≤ n) second feedback resistors 6,
is set by selecting each ith second feedback resistor 6 in such a way that, regardless of the time that is currently operating in the device for implementing the method of mechanical oscillating element 1 and vibration sensor 2 with vibration amplitude A of the vibration stand, the values indicated by indicator 8 are equal to each other .

 The second mode is the training mode.

In this mode, n "reference" bearings are sequentially installed in the engine. Under the "reference" bearing understand bearings with defects on the bearing elements of both operational nature and artificially applied. The first "reference" bearing, which determines the maximum permissible vibration amplitude of the vibration sensor A _p.p. , has the geometric dimensions of the defects, if they are equal or exceeding, the technical conditions for the corresponding bearing require it to be rejected. All subsequent “reference” bearings have n times smaller geometrical dimensions, where n ≥ 2.

 After the i-th “reference” bearing is installed in the engine, a mechanical oscillating element 1 with a vibration sensor 2 is installed in the engine. FIG. 2 the following notation is accepted, where 1 is the vibration sensor, 2 is the mass, 3 is 5 stiffness, 6 are the engine elements.

After that, the engine shaft starts to rotate in the frequency range from f _min to f _max with a discreteness of the change in the rotation frequency Δf. The mechanical oscillating element 1 converts shock pulses caused by defects of the "reference" bearing into harmonic vibrations, which are converted by an vibration sensor 2 into an electrical signal. Through the amplifier 7, the signal is supplied to the indicator 8. The indicator 8 is recorded at each of the discrete frequencies f _i in the range of the engine shaft speed from f _min to f _max , with selected stiffness parameters 3, 4, 5 and lengths L1, L2, L3 (Fig. 2), after which the range of frequencies of rotation of the motor shaft from f ₁ to f ₂ is determined, at which the difference between the two readings of indicator 8 is much smaller than the minimum readings of indicator 8 in this range. By varying the stiffness parameters 3, 4, 5 (Fig. 2) and the lengths L1, L2, L3 (Fig. 2), they achieve the maximum frequency range from f ₁ to f ₂ . In this case, the reading of indicator 8 is taken as the maximum allowable vibration amplitude of the vibration sensor for the i-th "reference" bearing.

Sequentially performing the above operation with each of the n "reference" bearings at the previously determined stiffness and coordinates of the support points of the mechanical oscillating element 1, determine for each i-th "reference" bearing (1 ≤ i ≤ n) the maximum allowable amplitude A _{i of the} vibration sensor vibrations 2, expressed in terms of i of indicator 8.

 The third mode is the diagnostic mode.

In this mode, in a motor with a bearing, the technical state of which is unknown, a mechanical oscillating element 1 is installed with the stiffness and coordinates of the reference points defined in the "Training" mode with the vibration sensor 2 installed on it, after which the motor shaft is rotated in the frequency range from f ₁ to f ₂ . The mechanical oscillating element 1 converts shock pulses caused by bearing defects into mechanical harmonic vibrations, which are converted by the vibration sensor 2 into an electrical signal, which is transmitted through the amplifier 7 to the indicator 8. The readings of the indicator 8 unambiguously characterize the geometric dimensions of the defects of the bearing being diagnosed, i.e. its technical condition, in accordance with which:
if the readings of indicator 8 are greater than or equal to the maximum permissible oscillation amplitude for the first "reference" bearing, then the bearing will be rejected;
if the readings of indicator 8 correspond to the readings for a "reference" bearing having defects with minimum geometric dimensions, then the maximum calibration time interval is set;
if indicator 8 readings are greater than indications for a “standard” bearing having defects with minimum geometric dimensions, then additional diagnostic methods are used, such as chip control in oil, metal in oil, etc .;
if there are signs of a defect in the diagnosed bearing by indirect diagnostic methods, then the vibration amplitude of the vibration sensor 2 is measured n times (n ≥ 2) successively by n-vibration sensors, each of which is mounted on its own vibration element, the diagnosed bearing is rejected, if only when using the readings of indicator 8 of one of the n-vibration sensors are greater than or equal to the maximum permissible vibration amplitude of the vibration sensor for the first "reference" bearing.

 Examples of specific performance.

 1. Mechanical vibration element 1. A possible embodiment of the mechanical vibration element is shown in FIG. 2.

 2. Vibration sensor 2. Vibration sensor can be made on the basis of an accelerometer type ANS 014 (BY 2.781.004 TU).

 3. Permanent storage device (ROM) 3. The ROM can be made on the basis of any type of electrical connector, the number of the mechanical oscillating element and its corresponding vibration sensor, in which it can be set by the corresponding wiring of the connector contacts, for example, in binary code.

 4. Decoder 4. The decoder can be made on the basis of an integrated circuit series K133, for example, K133 and D10 (see the journal "Radio", N 3, 1985, p. 24).

 5. The first feedback resistor 5 and n second feedback resistors 6. Feedback resistors can be made on the basis of serial resistors of any type, for example, MT, MPT, OMLT, etc.

 6. Amplifier 7. The amplifier can be made according to the circuit shown in FIG. 2.22 p. 89 (J. Witson. "500 Practical Designs on IP"), Mir Publishing House, 1992.

 7. Indicator 8. The indicator can be made on the basis of the microammeter M2003-M1 GOST 8711-78.

Claims (5)

1. A method for diagnosing transmission bearings by comparing the vibration amplitude of the vibration sensor with that determined in the "Training" mode by installing the "maximum" bearing in the engine with the maximum allowable vibration amplitude of the vibration sensor, characterized in that in the "Training" mode the vibration sensor is mounted on a mechanical vibration element, a mechanical vibration element mounted in the motor and motor shaft during rotation in the frequency range from f f _{m i n} to f _{m a x} to the discrete changes engine speed Δf, m nshey or equal to the minimum speed the motor shaft (Δf ≤ f _min), determined speed range of the motor shaft from f ₁ to f _2, the rigidity and the coordinates of control points of the mechanical oscillatory body, in which a difference ΔA of any two amplitudes A _i, A _k oscillations vibration sensor for "standard" bearing considerably less than the minimum amplitude of the vibration sensor for the "standard" bearing _{(ΔA = A i -A k «} A min) oscillation wherein the oscillation amplitude of the vibration sensor for the" standard "bearing taken as the maximum admissible A _{n th. d ,} and in the diagnostic mode, the vibration sensor is installed on a mechanical oscillating element with the stiffness and coordinates of the reference points defined in the "Training" mode, the mechanical oscillating element is installed in an engine with a diagnosed bearing, the motor shaft is rotated with a frequency f belonging to the frequency range from f ₁ to f ₂ , measure the vibration amplitude of the vibration sensor, and if the latter is less than the maximum allowable vibration amplitude of the vibration sensor A _{p . d ,} the operation of the bearing is continued, and if it is greater than or equal to the maximum permissible vibration amplitude of the vibration sensor A _{p . e ,} then the diagnosed bearing is rejected. 2. The method according to claim 1, characterized in that in the "Training" mode, n "standard" bearings (n ≥ 2) with various technological defects are sequentially installed in the engine, for each i-th "standard" bearing, the maximum permissible vibration amplitude is determined vibration sensor A _{p . d ,} in accordance with it, the calibration interval T _{i is set} , and for a "reference" bearing having technological defects that are minimal in geometric dimensions, the maximum allowable vibration amplitude of the vibration sensor is designated as the minimum A _{p . d m i n} , and the calibration interval T is the maximum time T _{m a x} , and in the diagnostic mode for each j-th diagnosed bearing, the calibration interval T _{j is} set based on the measured value of the vibration amplitude of the vibration sensor.  3. The method according to claims 1 and 2, characterized in that in the diagnostic mode, when the vibration amplitude of the vibration sensor is greater than the minimum maximum allowable vibration amplitude of the vibration sensor, indirect diagnostic methods are additionally used.  4. The method according to claims 1 to 3, characterized in that in the diagnostic mode when signs of defects of the bearing being diagnosed by indirect diagnostic methods appear, the vibration amplitude of the vibration sensor is measured n times (n ≥ 2) in series by n vibration sensors, each of which is mounted on its own mechanical oscillating element, and the diagnosed bearing is rejected if at least one measured vibration amplitude of the vibration sensor exceeds or is equal to the maximum permissible.  5. A device for implementing a method for diagnosing transmission bearings, comprising a vibration sensor, an amplifier and an indicator connected in series, characterized in that it is equipped with n mechanical vibration elements (n ≥ 1), each of which has a vibration sensor, a first feedback resistor, n second resistors feedback, a decoder with n outputs and m inputs (m ≥ 1), vibration sensors are equipped with read-only memory devices with m outputs that are connected to the inputs of the decoder, the outputs of which are connected to rvymi pin second feedback resistors, the second terminals of which are combined and connected to the first terminal of the first feedback resistor and a second input amplifier, whose output is connected to a second terminal of the first feedback resistor.

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