JP2008096410A - State monitoring technique for rotary machine using electromagnetic phenomenon - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a state monitoring technique capable of detecting an abnormal state generated in a rotary vane part of a rotary machine noncontactly with a rotary part. <P>SOLUTION: A permanent magnet or an electromagnet is arranged in a nonrotary part in the vicinity of a rotary vane of the rotary machine, a turbulence of a magnetic field generated by a transverse motion of the rotary vane in the magnetic field is detected using a magnetic field sensor such as an induction coil and a Hall element arranged in the vicinity of the rotary vane. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

The present invention relates to a state monitoring and state diagnosis technique that realizes early detection of an abnormal state of a rotor blade using an electromagnetic phenomenon.

In rotating machines such as turbines and pumps, damage and deterioration associated with long-term operation cannot be avoided. Depending on the part being used, the occurrence of a malfunction in the rotating machine may lead to the entire system being stopped, so the status of the rotating machine is regularly or continuously diagnosed to indicate as much as possible the signs of the malfunction. It is important to detect early. Conventionally, a technique of collecting displacement, velocity, acceleration, vibration spectrum data, and the like in the axial vibration of a rotating device and diagnosing the state of the rotating device based on those values has been mainly used. For example, in Japanese Patent Application Laid-Open No. 08-254402, a magnetic substance is attached to a rotating shaft or a component provided on the outer periphery of the rotating shaft, and an external magnetic field is detected by a magnetic sensor. A method for measuring the amount of directional movement is described.

Most of the damage to the rotating machine is due to the wear of the bearing. If the damage is caused by the wear of the bearing according to previous studies, the physical quantity of the rotating shaft is measured, and the accuracy is practically sufficient. It is said that a failure can be predicted. However, damage to the rotating machine is not necessarily due to bearing wear, and it cannot be said that the soundness of the rotating machine can be diagnosed simply by measuring the physical quantity of the rotating shaft. In particular, flaws generated at the end of the rotor blade have little effect on the rotation of the shaft, and unless the flaw has already grown to such a degree that it will seriously affect the function of the rotating machine, Cannot be detected. The present invention has been devised in view of such a background, and an object of the present invention is to provide a state diagnosis technique that enables detection of flaws generated in the rotor blades of a rotating machine at an early stage.

In the invention for solving the above-described problems, a permanent magnet or an electromagnet is arranged in a non-rotating part near the rotor blade of the rotating machine, and the disturbance of the magnetic field generated when the rotor blade crosses the magnetic field is arranged near the rotor blade. This is a state monitoring technique for detection using a magnetic field sensor such as an induction coil or a Hall element, and is characterized by detecting an abnormal state of a rotor blade from a measured magnetic field disturbance.

In the state monitoring technique as described above, an abnormal state occurring in the rotating blade portion of the rotating machine can be detected without contact with the rotating portion. In addition, there is a problem that abnormalities at the tip of the rotor blade are difficult to detect from vibration measurement of the rotating shaft of the rotating machine, but since this technology directly diagnoses the rotor blade, it can be detected by vibration of the rotating shaft. It is possible to detect abnormal conditions of rotor blades that cannot be detected at an early stage

Next, the Example in this invention is described in detail based on an accompanying drawing. Parts common to the drawings use the same reference numerals.

FIG. 1 shows an example of an embodiment of the present invention. FIG. 1A is a side view, and FIG. 1B is a front view. The figure shows a rotating machine composed of four rotating blades 21, 22, 23, 24 attached to a rotating shaft 11, and the rotating blade rotates around the rotating shaft in the direction of the arrow 31. And 41 is a permanent magnet or electromagnet for generating a magnetic field, and 51 is a magnetic field sensor.

Now, let us consider a case in which a rotating machine having four rotating blades is rotating 10 times per second as in FIG. 1, and a signal is measured using an induction coil as a magnetic field sensor. When there is no abnormality in the wings and all the wings have the same shape, the output signal waveform of the magnetic field sensor is a periodic one in which four identical waveforms are included in 0.1 second as shown in FIG. Become. On the other hand, for example, when the rotor blade 23 is missing, the contribution of the rotor blade 23 is lost as shown in FIG. 3 in the obtained signal, and three identical waveforms were confirmed in 0.075 seconds. A signal as shown in FIG. 3 indicating that no signal is confirmed for 0.025 seconds later is obtained.

Further, even when one of the four blades is twisted, the signal from the blade is changed. If the rotor blade 23 is twisted, if the distance between the blade and the magnetic field sensor is reduced due to the twist, only the signal from the rotor blade 23 has a large amplitude value as shown in FIG. On the other hand, when a twist that causes the distance between the wing and the magnetic field sensor to occur is large, it is clear that the signal amplitude is small. In general, a magnetic field sensor has a characteristic that a signal changes greatly depending on a distance from an object to be inspected. Therefore, even with slight deformation, a significant signal change can be confirmed according to the present invention. Further, as shown in FIG. 5, when a crack occurs at the tip of the rotor blade 23, the current induced in the rotor blade 23 flows around the crack, and the resulting signal is shown in FIG. Like 6, it looks as if the wings were split.

As described above, in the embodiment of the present invention, it is possible to easily detect the abnormality of the rotor blade, and it is also easy to evaluate the abnormal state from the obtained signal.

Effects of the embodiment

As described above, according to this embodiment, it is possible to easily and easily detect fine flaws generated on the rotor blades of the rotating machine, and early detection of deterioration of the rotating machine due to damage to the rotor blades is made possible. Will be able to.

Other embodiments

In the embodiment of FIG. 1 described above, the magnetic field generation source and the magnetic field sensor are arranged so as to sandwich the rotor blade, but it is important to detect the disturbance of the magnetic field by the rotor blade. Obviously, the location of the magnetic field sensor does not necessarily have to follow FIG.

It is a side view (Drawing 1 (a)) and a front view (Drawing 1 (b)) of one embodiment of the present invention. In the embodiment of the present invention shown in FIG. 1, the signal obtained when the shaft rotates 10 times per second and any of the rotor blades is not damaged is represented. In the embodiment of the present invention shown in FIG. 1, the signal obtained when the shaft rotates 10 times per second and the rotor blade 23 is missing is represented. In the embodiment of the present invention shown in FIG. 1, a signal obtained when the shaft rotates 10 times per second and the rotor blade 23 is twisted is represented. In one Embodiment of this invention, it is a front view of what represented the case where the crack has arisen in the rotary blade 23 front-end | tip. In the embodiment of the present invention shown in FIG. 1, the signal obtained when the shaft rotates 10 times per second and the tip of the rotor blade 23 is cracked as shown in FIG. 5 is expressed.

Explanation of symbols

11, 21, 22, 23, 24, which are rotating shafts of the rotating machine, and rotating blades of the rotating machine.
31 represents the direction of rotation of the rotor blades.
41. A permanent magnet or an electromagnet for generating a magnetic field.
51 is a magnetic field sensor for detecting a magnetic field.
61, 62, 63, and 64 are signals resulting from the disturbance of the magnetic field generated when the rotor blades 21, 22, 23, and 24 cross the magnetic field, respectively.
71, a crack generated at the tip of the rotor blade.

Claims (1)

A permanent magnet or electromagnet is arranged in the non-rotating part near the rotor blades of the rotating machine, and magnetic field sensors such as induction coils and Hall elements are arranged near the rotor blades to prevent magnetic field disturbances that occur when the rotor blades cross the magnetic field. It is a state monitoring technique that is used to detect, and is characterized by detecting an abnormal state of a rotor blade from a measured magnetic field disturbance.

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