RU2523044C1 - System and method for determination of spinning shaft torsion oscillation parameters - Google Patents

Abstract

FIELD: instrumentation.SUBSTANCE: system comprises shaft 1 angular displacement info elements composed of, for example, teeth 3 of gear 2 fitted on shaft 1. Shaft rpm info element composed of single tooth 6 at separate gear ring 7 or tooth 3.1 of said gear ring 2 is fitted also on said shaft 1. Besides, fixed transducers 4 and fixed rpm transducer counter located in its info element location surface are arranged outside shaft 1. Besides, it comprises hardware-software unit connected with said transducers for conversion and mathematical processing of transducers data. It differs from know designs in that second transducer 5 identical to first one 4 is fitted in every measurement plane at 180 degrees thereto on shaft 1 opposite side. The number of info elements in every measurement plane is even. Every info element makes a pair with the other info element (tooth 3) located in the same diameter on opposite side of shaft 1. Proposed method comprises measurement of time interval tbetween reference pulse of tooth 3.1 and current pulses. For every pair of serial pulses with numbers i and i+k/2 defined are the half-sum of time intervals ?ti=0.5(t+t), instantaneous angular displacements of current pulses ?=?t·?relative to reference; pulse and distribution of said instantaneous angular displacements caused by torsion oscillations ??=?-?.EFFECT: higher accuracy and validity.3 cl, 5 dwg

Description

Area of use

The invention relates to measuring equipment for diagnosing the technical condition of machines with rotating elements and can be used, in particular, to determine the characteristics of torsional vibrations of the shafts of power turbines, feed pumps and other similar equipment. The knowledge of the characteristics of torsional vibrations makes it possible to identify various defects of machines and evaluate the conditions unfavorable for their operation, and the smaller the values of the parameters characterizing torsional vibrations can be measured, the defect can be diagnosed at an earlier stage of development.

State of the art

Known adopted as a prototype of the claimed invention, a system for determining the characteristics of torsional vibrations of a rotating shaft, containing installed on it in the area of at least one measuring plane along the length of the shaft uniformly around its circumference information elements of the angular displacements of the shaft located on the specified shaft information element of the indicator of revolutions of its rotation , stationary measuring sensors installed outside the shaft, one in each of its measuring planes, and a stationary sensor a speed monitor installed in the plane of its information element for generating electrical impulse signals during contactless interaction of these sensors with the specified information elements, as well as a hardware-software unit for converting and mathematically processing the information received from the sensors (RU 2078324, G01M 15 / 00, 1997 [1]). As the indicated information elements, in combination with the corresponding sensors, for example, the teeth of a gear ring or turbine wheel blades specially mounted on the shaft can be used in combination with eddy current, induction, capacitive sensors, Hall sensors, etc .; reflective marks, slots in the disk mounted on the shaft, light-emitting diodes in combination as sensors with light-receiving devices.

From the same source [1] there is a known method for determining the characteristics of torsional vibrations of a rotating shaft, including the generation by the sensor of electrical impulses from information elements fixed in the measurement section on one of the sections of the specified shaft, and during the measurement, each revolution of the shaft is marked with a reference pulse from the marker revolutions and record the number of revolutions per unit time, and as the reference system take the start time of each revolution, record the indicated pulses from the next determining the required characteristics by mathematical processing of the measurement results with respect to the reference system created by a single impulse from the revolution indicator, and compare the obtained characteristics with similar characteristics in the shaft rotation mode with guaranteed absence of torsional vibrations.

The disadvantages of the system and method for determining the characteristics of torsional vibrations of a rotating shaft according to [1] include low measurement accuracy, which limits the possibility of using known means for diagnosing machines with rotating elements. The reason for the lack of measurement accuracy according to [1] is that the measured displacements of the shaft surface and the information elements installed on it are caused not only by angular (torsional) vibrations, but also by the precession movement of the shaft center and vibrational displacements of the sensor mounted on the stator relative to the shaft in the plane of rotation in the direction perpendicular to the axis of the sensor (not torsional transverse vibrations). Studies show that the amplitude of the transverse vibrations of the shaft relative to the torsional vibration sensor can reach 100 microns or more, and the vibration amplitude of the sensor itself relative to the shaft surface can exceed 50 microns. The indicated values are quite comparable with small torsional vibrations that determine the occurrence and development of a defect or the appearance of abnormal operating modes of the unit. As a result, a defect either cannot be detected at all or is identified with very low reliability.

Disclosure of invention

The technical result of the invention is to increase the accuracy of measurements and the reliability of diagnosis by eliminating spurious transverse vibrations of the shaft relative to the sensor from the measurements.

In the part of the invention on the “device”, this is ensured by the fact that in the system for determining the characteristics of torsional vibrations of a rotating shaft, which contains information elements of the angular displacements of the shaft located on the specified shaft in the area of at least one measuring plane along the length of the shaft along its circumference information element of the indicator of revolutions of its rotation, fixed measuring sensors installed outside the shaft, one in each of its measuring plane, and a stationary sensor revolution sensor installed in the plane of its information element for generating electrical impulse signals during contactless interaction of these sensors with the specified information elements, as well as a hardware-software unit for converting and mathematically processing the information received from the sensors according to the invention in each measurement the plane is additionally equipped with a second sensor, similar to the first and located relative to it under scrap 180 ° on the opposite side of the shaft in the same measuring plane, and the number of information elements in each measuring plane is even, each information element of the angular displacement of the shaft constitutes a pair with another similar information element, arranged on the same diameter on the opposite side of the shaft. In this case, one of the measuring information elements selected at least by a particular size in the measuring plane can preferably serve as a shaft rotation speed indicator.

In the part of the invention for the “method”, the indicated technical result is ensured by the fact that when implementing the method for determining the characteristics of torsional vibrations of a rotating shaft, which includes generating a sensor of electrical impulses from information elements mounted in the measurement cross section on one of the sections of the specified shaft, and during the measurement process mark each revolution of the shaft by the reference pulse from the speed indicator and record the number of revolutions per unit time, and take the time as the reference system the beginning of each revolution, the registration of the indicated pulses is carried out with the subsequent determination of the required characteristics by mathematical processing of the measurement results in relation to the reference system created by a single pulse from the revolution indicator, and the obtained characteristics are compared with similar characteristics in the shaft rotation mode with guaranteed absence of torsional vibrations, according to the invention to generate electrical impulses in the measurement cross section, an even number of information elec cops, arranged in pairs opposite each other in the measuring section, and two sensors mounted outside the shaft at an angle of 180 ° to each other, and to determine the desired characteristics of the torsional oscillations on each revolution of the shaft determine the time intervals t _i, where i = 1, 2, ..., k, k is the number of pulses per revolution, equal to the number of information elements between the reference pulse of the revolution marker and current pulses, and for each pair of consecutive pulses with numbers i and i + k / 2 determine the half-sum of time intervals Δti = 0.5 (t _{i + k / 2} + t _i ), instant the values of the angular displacements of the current pulses relative to the reference pulse φ _i = Δti · ω _j where ω _j is the average value of the angular frequency of rotation of the shaft per revolution equal to ω _j = 2π / T _j , T _j is the time of one revolution of the shaft, and the distribution over the circumference of the shaft of instantaneous values of angular displacements due to torsional vibrations Δφ _i = φ _i -φ _0i, where φ _0i are the angular distances between the reference and current pulses, which are determined during operation with a guaranteed absence of torsional vibrations.

A causal relationship between the hallmarks of the claimed invention and the achieved technical result is as follows:

- the location in each measuring plane of an additional second sensor, similar to the first and located relative to it at an angle of 180 ° from the opposite side of the shaft in the same measuring plane, allows you to exclude information signals associated with transverse vibrations of the shaft during mathematical processing of measurement results opposite direction;

- an even number of information elements in each measuring plane, as well as the fact that each information element of the shaft angular displacements is paired with another similar information element located on the same diameter on the opposite side of the shaft, provides a clear implementation of the above symptom due to strictly symmetrical effects on sensors of oppositely directed pulses of information signals;

- the determination at each revolution of the shaft of the time intervals t _i between the reference pulse of the revolution marker and the current pulses in the above order allows you to obtain the required characteristics of torsional vibration of the shaft with great accuracy and reliability of diagnosis.

Thus, all the distinguishing features of the invention are interconnected to provide, together with the restrictive features of the above technical result. The exclusion of any of these signs will lead to the impossibility of obtaining this result.

Brief Description of the Drawings

Figure 1 schematically depicts a controlled shaft with an electric pulse generating system of information elements in the form of a gear ring and with two sensors located 180 degrees relative to each other in the measurement plane; figure 2 shows the formation of a single impulse from the revolution meter, made in the form of a single protrusion (tooth) on a separate gear ring; figure 3 shows the time intervals to be measured between the reference and current pulses generated in the sensor when passing the teeth of the main gear ring and a single tooth of the revolution indicator; figure 4 - the same when using as a speed indicator of one selected tooth of the common gear ring; figure 5 presents in the form of vector segments the components of the angular displacements between the reference pulse and a pair of current pulses generated in two sensors shifted around the circumference of the shaft by 180 degrees.

DETAILED DESCRIPTION OF THE INVENTION

The system for determining the characteristics of torsional vibrations of a rotating shaft 1 according to the invention contains an information element of the angular displacements of the shaft, in this example, in the form of a gear ring 2 made of ferromagnetic material with teeth 3 mounted on the shaft 1 in the area of one arbitrary section along its length 3. From opposite sides of the gear ring 2 at an angle of 180 ° at points A and B, two measuring induction sensors 4, 5 are installed. A software-computing unit (not shown) is connected to these sensors 4, 5 for mathematical analysis bots of information received. The indicated system is also equipped with a rotation speed meter of shaft 1. In the example of figure 2, this marker is made in the form of a single tooth 6 on a separate gear ring 7. In the example of figure 4, this marker is made in the form of one of its selected in the common gear ring 2 teeth 3.1. In this case, the toothed ring 2 has an even number of teeth 3, and each tooth 3 is paired with another of the same tooth located on the same diameter from the opposite side of the ring.

The method according to the invention is as follows. On each revolution of the shaft 1 determine the time intervals t _i , where i = 1, 2, ..., k, k is the number of pulses per revolution of the shaft 1, equal to the number of teeth 3 of the gear ring 2 between the reference pulse of the speed indicator and the current pulses from the gear ring 2. For each pair of consecutive pulses with numbers i and i + k / 2, determine the half-sum of time intervals Δt _i = 0.5 (t _{i + k / 2} + t _i ). Dividing the time intervals by the average value of the angular frequency of rotation of the shaft 1 per revolution ω _j = 2π / T _j , where T _j is the time of one revolution of the shaft, we obtain instantaneous values of the angular displacements φ _i = Δt _i / ω _{j of the} current pulses relative to the reference pulse. The distribution around the shaft circumference of the instantaneous angular displacements due to torsional vibrations is obtained at each revolution of the shaft as the difference Δφ _i = φ _i -φ _0i, where φ _0i are the angular distances between the reference and current pulses (angles between the speed indicator 6 or 3.1 and teeth 3 of the toothed ring 2), which are determined separately during operation of the machine with the shaft 1 with a guaranteed absence of torsional vibrations. The values of φ _0i obtained in this way are stored at once as constants of the measurement procedure until the moment the position of the sensors or the gear ring 2 and the speed indicator 6 are changed relative to each other.

For greater clarity and by analogy with measurements of transverse vibrations of shafts and bearings, torsional vibrations can be measured in the form of linear displacements on an arc of conditional radius R. Then, the instantaneous values of torsional displacements are represented as ΔS _i = R · Δφ _i . Taking into account the mutual direction of the components, the resulting displacements are presented in the form of an algebraic sum (displacements in the direction of rotation are taken as positive):

S _A = ψ _A -γ _A + θ _A + ΔS _A ; S _B = ψ _B + γ _B -θ _B + ΔS _B , where

ψ _A and ψ _B are the angles between the revolution meter and the opposing teeth 3 of the gear ring 2;

γ _A and γ _B - displacements caused by transverse vibrations of the shaft 1 relative to the sensors 4, 5;

θ _A and θ _B - vibrational displacement of the sensors 4, 5 relative to the shaft 1;

ΔS _A and ΔS _B - displacements due to torsional vibrations of the shaft 1.

Since ψ _A and ψ _B , γ _A and γ _B always enter the total displacements at opposite points with different signs, and the torsional displacements ΔS _A = ΔS _B , in the half-sum 0.5 (S _A + S _B ) = 0, 5 (ψ _A + ψ _B ) + ΔS _A, there will always be no terms due to vibrations of the shaft and sensors. Performing similar operations in the mode with no torsional vibrations, we obtain

0.5 (S _A0 + S _B0 ) = 0.5 (ψ _A + ψ _B ). Performing subtraction at the final stage of processing the measurement results

0.5 (ψ _A + ψ _B ) + ΔS _A -0.5 (ψ _A + ψ _B ) = ΔS _A ,

we obtain torsional displacements as a result. Obviously, similar operations are performed for all pairs of pulses (figure 5).

Thus, when using the system and method for determining the characteristics of torsional vibrations of a rotating shaft according to the invention, the above technical result is provided, which consists in increasing the accuracy of measurements and the reliability of diagnosis by eliminating spurious transverse vibrations of the shaft relative to the sensor from measurements.

Claims (3)

1. A system for determining the characteristics of torsional vibrations of a rotating shaft, containing information elements of the angular displacements of the shaft mounted on it in the region of at least one measuring plane along the length of the shaft along the circumference of the shaft, information element of the indicator of revolutions of its rotation located on the specified shaft, fixed measuring sensors, installed outside the shaft one at a time in each of its measuring planes and a stationary sensor for the speed indicator mounted in the plane of its inf an element for generating electrical impulse signals during the contactless interaction of these sensors with the specified information elements, as well as a hardware-software unit for converting and mathematical processing of information received from the sensors, characterized in that in each measuring plane there is an additional second sensor similar the first and located in relation to it at an angle of 180 ° from the opposite side of the shaft in the same measuring plate oskosti, and the number of information elements in each measuring plane is even, and each information element of the angular displacements of the shaft is paired with another similar information element located on the same diameter from the opposite side of the shaft. 2. The system for determining the characteristics of torsional vibrations of a rotating shaft according to claim 1, characterized in that one of the measuring information elements selected by at least one special dimension in the measuring plane serves as a shaft rotation speed indicator. 3. A method for determining the characteristics of torsional vibrations of a rotating shaft, including the generation by the sensor of electrical impulses from information elements fixed in the measurement section on one of the sections of the specified shaft, and during the measurement, each revolution of the shaft is marked with a reference pulse from the speed indicator and the number of revolutions is fixed in unit of time, and as the reference system take the start time of each revolution, record these pulses, followed by determining the required x characteristics by mathematical processing of the measurement results with respect to the reference system created by a single impulse from the revolution indicator, and compare the obtained characteristics with similar characteristics in the mode of rotation of the shaft with a guaranteed absence of torsional vibrations, characterized in that an even number is used to generate electrical pulses in the measurement cross section information elements arranged in pairs opposite each other in the measurement section, and two sensors mounted outside the shaft at an angle of 180 ° to each other, and to determine the required characteristics of torsional vibrations on each revolution of the shaft, time intervals t _{i are} determined, where i = 1, 2, ..., k, k is the number of pulses per revolution, equal to the number of information elements, between the reference pulse of the speed indicator and current pulses, and for each pair of consecutive pulses with numbers i and i + k / 2 determine the half-sum of time intervals Δt _i = 0.5 (t _{i + k / 2} + t _i ), instantaneous values of angular displacements of current pulses φ _i = Δt _i · ω _j relative to the reference pulse, where ω _j is the average e is the value of the angular frequency of rotation of the shaft per revolution equal to ω _j = 2π / T _j , T _j is the time of one revolution of the shaft, and the distribution around the shaft circumference of the instantaneous values of angular displacements due to torsional vibrations Δφ _i = φ _i -φ _0i where φ _0i are the angular distances between the reference and current pulses, which are determined in the operating mode with a guaranteed absence of torsional vibrations.

Images