JPS5934147A - Flaw detector for rotor blade - Google Patents

Abstract

PURPOSE:To judt the abnormality of a blade mounted to a rotor by detecting and storing the frequency output from the acoustic wave obtd. by hammering the blade and comparing the same with the frequency output of the next blade. CONSTITUTION:When a blade 2 is hammered, the oscillation sound thereof is collected with a microphone 6 and is inputted to a frequency detection circuit 7; therefore, the specific frequency with said blade 2 is detected in synchronization with the timing signal from a transmitter 8. The detected frequency detection signal is supplied to an arithmetic section 9 and is temporarily stored in a storage device 12. The frequency of the blade 2A obtd. before the same and the frequency obtd. from the blade 2 are compared in a comparator 13, and when there is a difference of a prescribed value or above between both frequencies as a result of the comparison, the section 9 discriminates the presence of abnormality and supplies the abnormality signal to an abnormality announcing means 11.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a deep flaw device capable of detecting cracks existing in turbine rotor blades by simple hammering.

Non-destructive testing methods are widely used when inspecting materials such as metal parts and the scratches generated by them. It has also been widely used as a flaw detection method. However,
When detecting the presence of cracks in the blades of turbine rotors, transmission inspection using radiation such as X-rays and visual inspection using microscopes have traditionally been used as non-destructive inspection methods. It's coming.

However, in any case, with such conventional flaw detection methods, the blade must be disassembled from the beginning and end, and especially when using radiographic inspection, it is necessary to project the entire surface in order to obtain a transmission image. In addition to requiring high equipment costs, it is also time consuming. Currently, SA@mirror detection is limited to external injuries, and when detecting small wounds, there is a risk of overlooking them, so reliability is at stake.

The object of the present invention is to provide a rotor blade flaw detection device which eliminates the above-mentioned drawbacks and is capable of detecting cracks in individual blades by hammering while the turbine rotor remains without disassembling the blades from the rotor. It is about providing.

In order to achieve this purpose, the present invention detects the frequency output, such as frequency distribution and average frequency, from the sound waves obtained by hammering the blades attached to the rotor.
The frequency output is memorized each time, and compared with the frequency output obtained when the next blade is hammered, and when there is a predetermined difference between these frequency outputs, it is determined that there is an abnormality in the blade. Configure it as follows.

The present invention will be described in detail below with reference to the drawings.

In general axial flow turbines, the turbine blades are installed radially on the rotor and have a cantilever structure, so if there are cracks in the blades, the rigidity decreases and the natural frequency of the blades increases. is lower than other normal blades.

Therefore, we hammered each individual blade,
By comparing the frequency output such as the frequency distribution and average frequency of each blade, since the majority of blades are normal, it is possible to clearly understand the difference between abnormal blades and detect abnormal blades. can do.

The present invention has been made based on such a principle, and FIG. 1 shows an embodiment of the present invention based on this principle, where / is a turbine rotor, and λ is an inspection object implanted in the rotor λ. This is a blade that detects existing cracks by hammering two blades one after another.
The detector has a microphone (9), a frequency detection circuit (72), a calculation section (2), a frequency display meter (.theta.), and an abnormality notification means (1).

Furthermore, the calculation unit 9 includes a storage device 12 for storing the frequency detected by the frequency detection circuit 7 and the average frequency up to that point outputted by the calculation unit W, respectively;
The comparison circuit 13 compares the detected frequency with a previously detected frequency or an average frequency up to that point.

In the rotor blade flaw detection device j configured in this way, when the blade λ is hammered, the vibration sound is collected by the microphone B and input to the frequency detection circuit 7, so that it is combined with the timing signal from the transmitter g. By synchronizing, a specific frequency (for example, the frequency of natural vibration) in the blade λ can be detected. In this way, the detected frequency detection signal is supplied to the calculation section,
Here, the frequency is temporarily stored in the storage device 12, and if there are two hammering blades in front of this blade λ, the frequency obtained from this blade JA and the frequency obtained from blade 2 are stored. Comparison circuit 13 compares the two frequencies, and if the comparison results in a difference of more than a predetermined value between both frequencies, the arithmetic unit determines that there is an abnormality and supplies an abnormality detection signal to abnormality notification means //. Here, if the abnormality notification means // is constituted by a lamp or a buzzer, an abnormality in the blade λ can be detected by lighting the lamp or warning.

However, it goes without saying that blade 2 is judged to be abnormal only when flaws are detected one after another using this procedure and a difference of more than a predetermined value is obtained only at blade l. It is.

Furthermore, the arithmetic unit 9 converts the above-mentioned frequency into the comparator circuit 1.
As a result of the comparison in step 3, if a difference of more than a predetermined value cannot be obtained between them, the average value of each frequency of the hammering results so far and the frequency obtained by hammering the blade λ is used, and this average value is calculated. The frequency is stored in the storage device 12.

Then, the next blade λB is hammered, and the frequency obtained in the same way by this hammering is compared with the frequency obtained for blade λ. If there is no difference of more than a predetermined value, then Average frequency and comparison circuit 13
A similar comparison is made, and if there is a difference greater than a predetermined value, this blade 2B is determined to be abnormal and an abnormality detection signal is supplied to the abnormality notification means.

Also, if there is no difference greater than a predetermined value, it is determined that the blades are normal, and the blades 20. ...
The flaw detection is continued by hammering ..., and after completing one rotation, the average frequency of all the blades can also be determined.

Note that these frequencies are displayed one after another by the frequency display meter l/. Here, regarding the frequency display,
It may be in either analog or digital form.

As explained above, according to the present invention, each blade installed in the rotor is hammered one after another, a specific frequency is detected from the vibration sound obtained, and if the blade is in a normal state, the upper part of the blade is detected. If the frequency obtained when hammering seven blades differs from the frequency obtained when hammering other blades by more than a predetermined value, an abnormality is detected. As a result, flaw detection can be performed with the blade still attached to the rotor without disassembling it.
Moreover, cracks existing in the blade can be detected reliably and quickly by simply hammering, and furthermore, the average frequency can be detected by just hammering seven times.

In addition, although the case where comparison is performed regarding a specific frequency has been described above, the present invention is not limited to this example, and it is of course possible to perform comparison regarding frequency distribution for successive blades.

[Brief explanation of the drawing]

FIG. 1 is a VC block diagram showing an example of the configuration of a rotor blade flaw detection apparatus according to the present invention, together with a rotor and a hammer. l...turbine rotor, λ...blade, 3...
・Hammer! ...Flaw detection device, 6..Microphone, 7..Frequency detection circuit, Z..-Transmitter, 9..9 section, /θ..Frequency display meter, l/..Abnormality alarm. Means, 12... storage device,
13... Comparison circuit. Patent applicant Nissan Motor Co., Ltd.

Claims (1)

[Claims] 1) Sound collection means for collecting vibration sounds generated when seven blades installed in a rotor are hammered, and a frequency output from the vibration sounds collected by the sound collection means. What is claimed is: 1. A rotor blade flaw detection device comprising: a frequency detection circuit for detecting; and a calculation section for determining whether or not there is an abnormality in the blade based on the frequency output obtained from the frequency detection circuit. 2. In the flaw detection apparatus according to claim 1, the calculation section includes a storage means for storing the frequency output, and a storage means for storing the frequency output, and a method for storing the stored frequency output by hammering another blade. A rotor blade comprising a comparison means for comparing the frequency output obtained from the frequency detection circuit, and a determination means for determining whether or not there is a difference of more than a predetermined value between the compared frequency outputs. flaw detection equipment. 3) In the flaw detection apparatus according to claim 2, when there is no difference between the frequency outputs by more than a predetermined value, the determination means calculates the average of both frequency outputs, and calculates the average of the frequency outputs. A rotor blade flaw detection apparatus characterized in that the data is stored in a storage means and used for comparison when the comparison means is busy.