JPH03229125A - Accuracy improving method for rotary machine state monitoring system - Google Patents

Abstract

PURPOSE:To remove the mixture of an error in measured value due to a drift, etc., by calculating the peripheral positions of a rotary shaft where the perpendicular supporting force becomes minimum/maximum, finding bearing supporting forces at positions where a specific phase is obtained based on the positions, and calculating and correcting a gap measured value. CONSTITUTION:The position of the axis of a journal shaft 1 is arranged so that the position is measured by detectors 2-1 and 2-2 such as eddy current displacement gauges based on the center CB of the bearing. After the outputs of the detectors are converted by a measuring instrument 3 into the value of the position of the axis of the journal shaft 1, a computing element 4 performs arithmetic operation to correct an error and the corrected axis position is inputted to a monitoring device 5 to monitor the state. At this time, the peripheral positions CJU and CJD of the rotary shaft where the perpendicular bearing supporting force becomes minimum/maximum are calculated, the vector sum of the supporting forces at the positions CJ1 and CJ3, and CJ2 and CJD where the specific phase is obtained is found at least twice based on both positions, and the gap measured value is calculated and corrected so that the difference between the vector sums becomes minimum.

Description

Detailed Description of the Invention A) Industrial Application Field A system that monitors the position of the rotational axis of a rotating machine such as a turbine supported by an oil film bearing to determine whether there is an abnormal condition that may impede the operation of the rotating machine. It belongs to the field of designing and using.

b) Conventional technology Since only a simple gap measurement method such as the use of an eddy current displacement meter could be used, for example, the Japan Society of Mechanical Engineers 68
As can be seen in the description in Table 2 on page 34 of the one-time training course "Easy Rotating Objects", the disadvantage of monitoring the axis position is that "the reliability of the measuring device (especially the measuring device) is poor". there were. Therefore, as a result of increased errors in measured values due to drift due to thermal and voltage changes over time, etc., it has been difficult to monitor trends in state changes of rotating machines.

(1) Problem to be Solved by the Invention Even if measurement errors with a relatively small rate of change over time, such as drift, are mixed into the measured value of the position of the rotational axis, it can be easily removed and Suggest ways to monitor long-term trends.

Eccentricity of the rotating shaft relative to the bearing center (= eccentricity divided by effective radius clearance) obtained based on gap measurements using an existing eddy current displacement meter, etc. When calculating the supporting force of the bearing using the capacity coefficient (= reciprocal of the Sommerfeld number) for the eccentricity, determine the circumferential position of the rotating shaft where the vertical supporting force is minimum and maximum,
Using both positions as a reference, calculate the vector sum of the supporting force at a point with the same phase with respect to the circumferential position of the rotating shaft at least twice with different phases, and calculate the gap measurement value so as to minimize the difference between these vector sums. Correct the calculation.

E) Action The force supported by a bearing is usually a resultant force such as a component of the weight of the rotating body against the bearing, a force due to misalignment, and a fluctuating force due to rotation caused by unbalance. According to the configuration of the present invention, the unbalanced forces cancel each other in the process of calculating the vector sum, and the component force of the rotating body's own weight and the misalignment force cancel each other due to the difference in the vector sum obtained afterwards. In principle, the obtained result should normally be zero, but if there is a deviation error in the measured value of the rotation axis, the force calculated based on it will differ from the actual value. Therefore, a force component that cannot be canceled remains depending on the magnitude of the error in the measured value. Therefore, in order to bring the desired result close to zero, it is necessary to find and remove an appropriate correction value for the measured value of the axis of rotation, for example by using the well-known "hill climbing method" used to find appropriate values in the control field. If so, the error will be corrected.

Power) Example This will be explained in detail based on one embodiment shown in FIG.

A detector 2-1.2-2, such as an eddy current displacement meter, is arranged so that the position of the axis of the journal shaft 1 is measured with the center of the bearing as a reference. In this embodiment, the detector 2-1 is arranged vertically and the detector 2-2 is arranged horizontally.

(Even if the arrangement direction of the detectors is changed or the number of detectors is increased, the basic idea of the present invention will not be deviated from.) After converting into the value, the calculation unit 4 performs the calculations described below, and the corrected axis center position with error correction is input to the monitor 5 to monitor the state.

Journal axis l that is the target when calculating according to the present invention
FIG. 2 shows the state of the force applied to the axial center at each position of the axial center. journal shaft l
Let CJtl be the position in the bearing of the axis of journal shaft l when the vertical component of the force applied to the axis is minimum, and CJD be the position when it is maximum. Generally, the supporting force of an oil film bearing is determined by the eccentricity of the journal shaft 1 with respect to the center C3 of the bearing. The relationship between the eccentricity and the supporting force of an oil film bearing is given by the capacity coefficient, which is the reciprocal of the known Simmerfeld number. The eccentricity can be given by the ratio of the distance between the bearing center C6 and the center of the journal axis l to the effective radial clearance determined by the bearing. The distance can be obtained as the output of the measuring device 3, and the effective radial clearance can be obtained as the characteristic value of the bearing. Therefore, if the distance is determined as the output of the measuring device 3 using sampling pulses of, for example, 64 pulses/rotation synchronized with the rotation of the rotating shaft, then
Since the change in bearing support force within one revolution of the rotating shaft is known through eccentricity, CJU+CJl can be easily determined in terms of the position of the shaft center where the vertical component force is minimum and maximum. Furthermore, the bearing support force' at a position having a predetermined phase based on the CJul CJD standard can also be determined. (Please note that sampling is possible so that each side can be
Since it is natural to set the number of pulses/rotation as the number of pulses, it will not be discussed in further detail in this specification. ) C.J.
a, rotational phase difference α1 of journal axis l with reference to CJI; The positions of the axis of the journal shaft 1 in the state of α2 are CJII, CJl and G, respectively, as shown in Fig. 2.
Let's call it Jit CJ4.

Also, regarding the respective forces supported by the bearings (not shown in the figure) that support the journal shaft l, let the component force of the rotating body's own weight be f Iln The misalignment force be f □ The force due to unbalance be f8 , CJll CJllCJ3+
At a feature point such as cJ4, the forces acting on the axis have the following relationship.

However, the rotation angle of the journal shaft l is taken in the direction of the Y axis with the X wheel in FIG. 2 as a reference.

CJl: Horizontal force Flx = f, ・CO3(β)+f, ・COS <π/2−α,)
CJI; Vertical force Fly = f, +f, ・5IN(β)+f1SIN(π/2-α1
)C1寞;Horizontal force F2x= f 1I−CO5(β) + f ,−CO3(π/2
+αχ)CJz: Vertical force F2y=f, +f, -5IN(β)+fII-SIN(π
/2+α2)C1,;Horizontal force F3x=f, -CO5(β)+fu-CO5(-π/2-α1
) C1,; Vertical force F3y = f, 10f, ・5IN(β) + f tI-SIN(-
π/2-α1) CJa; Horizontal force F4x= fl・CO5(β)+f1・CO5(-π/2+α:)
CJa; Vertical force F4y = f, +f, ・5IN (β) 10 f @・5IN (−π/
2+ α2) CJI+ Take the vector sum of the forces at C10 and let the result be F13, then F 13 x=2 ・f, -COS(β)IF 13
y=2・(f,+f ll-5IN(β)) Similarly, C,! , C, 4, and let the result be F24, then F24 x=2 · f, -CO3(β).

F24y=2 ・(f, 10f, ・5IN(β)) However,
F13. The subscripts x and y of F24 indicate components in the x and y directions.

Therefore, if we take the difference FS between the vector sum F13°F24 of these two forces, it is clear that FS must become zero. On the other hand, the supporting force of the oil film bearing is determined by the eccentricity of the journal shaft l with respect to the center C1 of the bearing, so if there is an error in the eccentricity, the FS determined from the eccentricity will not be zero.

By simulating an error in the output of the measuring device 3, the FS
Figure 3 shows the values of .

Figure 3 shows a journal with a diameter of 200 mm and a bearing length of 150 mm.
], f, -5000X 9.8 (N), f@-
,02[kgl x, 5[M] x (2π60)”[
N], effective radius clearance, 15 [1. viscous modulus,
07[N-s/M town, 7 Misalignment force and direction are 200x9.8 (N], 30 (deg), αt
=45 (deg) and αg=45 (deg), the size r, ・direction T, as shown in FIG.
This figure shows the value of FS when the center C of the bearing appears to be at CI' with respect to the axis of the journal shaft l, with an error of . As can be seen from Figure 3, if FS is minimized using the well-known "hill climbing method", the inherent size rlj
The error in the + direction γ can be found. Therefore, from the output of the measuring device 3, r, ·cosTa in the horizontal direction.

It is sufficient to subtract the correction amount of r, ·SIN r * in the vertical direction.

G) Effects of the Invention According to the present invention, the reliability of the monitoring system for rotating machinery can be improved by adding a small amount of calculation function, and long-term trends in the condition of rotating machinery can be grasped, making it possible to maintain condition-based maintenance. monitoring and diagnosis.

[Brief explanation of drawings]

FIG. 1 is a diagram related to the equipment configuration of an embodiment of the present invention, FIG. 2 is a reference diagram for explaining the algorithm of the present invention, and FIG.
The figure is an example of the influence of the magnitude of the output error of the measuring instrument, and FIG. 4 is an explanatory diagram of the error. : Journal axis, 2-1゜2-2: Detector, : Measuring device, : Computing unit, : Monitoring device. Applicant Nippon Steel Corporation

Claims (1)

[Claims] 1. When calculating the supporting force of the bearing from the eccentricity of the rotating shaft with respect to the bearing center using the capacity coefficient for that eccentricity, find the circumferential position of the rotating shaft where the vertical supporting force is minimum and maximum. Index, calculate the vector sum of the supporting force at the same position with respect to the circumferential position of the rotating shaft at least twice with the same phase relative to the circumferential position of the rotating shaft based on both positions, and set the gap so as to minimize the difference between these vector sums. A method for improving the accuracy of a rotating machine condition monitoring system, characterized by calculating and correcting measured values.