JP4077274B2 - Gas turbine air compressor blade surface crack inspection method and apparatus - Google Patents

Description

となり、亀裂深さ０．１〜０．２ｍｍは、かろうじて検出が可能な超音波である。そこで、検査対象の亀裂深さから、使用する超音波の発振周波数は、２０ＭＨｚ程度が適用可能となる。
【００２２】
超音波を使用して亀裂を検出するためには、亀裂に対して超音波に対し強い指向性を持たせることを必要とする。超音波の指向性を強めるためには、超音波を発振する振動子の直径Ｄを大きくすることで達成できる。振動子の直径Ｄが限りなく小さい場合、単一の振動子から発振される超音波は、ホイヘンスの原理のように、１点から全周に向かって超音波が発振する。振動子がある構造物に取り付けられていれば、１点から１８０°の方向に向かって超音波が発振する。
【００２３】
複数の振動子を並列に配置すると、各点からの超音波が合成された超音波として形成される。この合成過程で超音波の指向性が形成される。振動子の直径がＤの場合、各点の振動子がＤの間に多数設置された状況となり、超音波の発振は同時間，同位相となる。このような超音波は、超音波合成過程では、超音波振動子からある程度離れた位置で超音波のビームが発生する。このビームを使って、超音波による探傷を行うことができる。
【００２４】
ここで、振動子から安定したビームが発生するまでの距離（超音波が不安定な距離）を近距離音場と称し、安定したビームが存在する領域を遠距離音場と称される。振動子から遠距離音場の開始までの距離（近距離音波限界距離）Ｘ0は、以下の式で求められる。
【００２５】
Ｘ0＝Ｄ^２／（４×λ） （ｍｍ）
ここで、Ｄ：振動子直径（ｍｍ）であり、λ：超音波波長（ｍｍ）である。
【００２６】
２０ＭＨｚの周波数を振動子直径１０ｍｍで超音波を発振し、被検材と同一素材の中を伝播させるためには、Ｘ0＝８３ｍｍ程度必要とする。この寸法は、ガスタービン空気圧縮機の翼の厚さ１０ｍｍを遥かに超えた寸法となる。
【００２７】
このため、翼の裏面の亀裂部分に超音波をフォーカスしようとすると、振動子と翼の間に超音波を通す媒体（ガラス等）を設置する方法が考えられる。この場合、ガラス等の音速は５６００ｍ／ｓであり、被検材とほぼ同等のため、振動子の前面にガラスを設置してセンサを構成しようとすると、センサの高さは９０ｍｍ程度のサイズとなる。一方、ガスタービン空気圧縮機の翼列の距離（図１の距離Ｈ１）は、２９ｍｍであるため、上述したように、ガラス等を設置したセンサでは、翼列の間に挿入できず、測定が不可能である。
【００２８】
そこで、本実施形態では、図２にに示したように、同じ振動子直径１０ｍｍに対し、数多くの振動子エレメントを個別に組立て、個々の振動子エレメント１０−１，…，１０−３２から単独に超音波を発振するアレイ型探触子１０を使用するようにしている。個々の振動子エレメントからは、上述したように１８０°の方向に超音波が発振できるが、個々の振動子を振動させるタイミングを調整して超音波を合成することで、従来の超音波センサからの超音波発振時に発生する近距離音場の領域をなくすることが可能となる。以上のようにして、翼間隔の狭い翼の検査を可能とした。
【００２９】
アレイ型探触子から発振する超音波の周波数は、検出する亀裂深さが０．１〜０．２ｍｍと微細なため、超音波波長は０．２〜０．４ｍｍが必要となる。翼内の音速は縦波で約６０００ｍ／ｓ、横波で約３３００ｍ／ｓとなる。この音速で亀裂深さ０．１〜０．２ｍｍを検出するためには、波長が０．２〜０．４ｍｍ以下を発振する周波数が必要となる。
【００３０】
縦波では、ｆ＝（６０００ｍ／ｓ）／（０．２〜０．４ｍｍ）よりｆ＝３０ＭＨｚ〜１５ＭＨｚとなる。横波では、ｆ＝（３３００ｍ／ｓ）／（０．２〜０．４ｍｍ）よりｆ＝１７ＭＨｚ〜８．３ＭＨｚとなる。横波は、縦波より音速の特性より適用周波数が低めにて対処可能となることより、横波の超音波を適用することで０．１ｍｍの亀裂を確実に検出するためには、１７ＭＨｚ〜２０ＭＨｚの超音波周波数を使用ですむことが確認された。
【００３１】
ここで、アレイ型探触子から直接発振する超音波は、縦波である。この縦波では、亀裂長さ０．１ｍｍを検出するためには３０ＭＨｚ以上の超音波が必要であるが、現状の製作レベルでは難しいのが実情である。
【００３２】
そこで、横波を使用するために、アレイ型探触子１０の出口と翼との間に、図２に示した形状のシュー２０を設置している。シュー２０の角度θ１を、縦波の臨界角（２７．５°）以上である角度，例えば、２９．２°とすることにより、シュー２０内に縦波の超音波が入射したものがシューから翼に入る時点で縦波成分がなくなり、横波成分のみとなる。このように、シュー２０を設置することにより、翼内の超音波は横波となり、１７〜２０ＭＨｚの周波数においても、０．１ｍｍの亀裂の検出が可能となる。
【００３３】
以上のように、現状で製作できる最も高い周波数（１７〜２０ＭＨｚ）を発振するアレイ型探触子の出口に、２７．５°以上の角度をもつシューを設置することで、３０ＭＨｚと同レベルの検出能力を出すことを可能となった。（横波の活用による検出能力を高めた）この横波の活用により、アレイ型探触子からの翼内への超音波の入射角θ２は、３５〜４５°となる。以上の対策で現状で製作できる最も高い周波数（１７〜２０ＭＨｚ）を発振し、しかも現状の翼の配列の中で使用できる寸法のアレイ型探触子を使用して０．１ｍｍ程度の亀裂を検出可能とするためには、シュー（２７．５°以上）をアレイ型探触子出口に設置して入射角３５〜４５°で超音波を発振することが必要であり、この条件下で初めて翼の内に発生している０．１ｍｍ程度の亀裂の検出を可能となる。
【００３４】
アレイ型探触子と翼内の超音波を横波とする２７．５°以上の角度をもつシューからなる探傷方法において発振した超音波を亀裂が発生している翼面に焦点を結ぶように超音波を調整することで、亀裂からの反射エコーの音圧を高めることにより、微細亀裂の検出能力を高めることができる。
【００３５】
以上のようにして、図２に示したアレイ型探触子１０は、微少亀裂を検出可能とするため、発振周波数を１７〜２０ＭＨｚとしている。また、図２に示すように、微少亀裂Ｃ２が発生している翼裏面９０Ｂの直下に焦点化するように、３２個の探触子エレメントの内、１６個の探触子エレメントを用いて、超音波をフォーカスに制御している。
【００３６】
さらに、探傷装置３０は、３２個の探触子エレメントの内、発振するエレメントを順次移動して、焦点位置も順次移動するようにしている。すなわち、第１回目では、１６個の探触子エレメント１０−１，１０−２，…，１０−１６を発振させ、超音波Ｓ１を翼９０の裏面９０Ｂにフォーカスする。第２回目では、発振する探触子エレメントを１個ずらして、１６個の探触子エレメント１０−２，１０−３，…，１０−１７を発振させ、超音波Ｓ２を翼９０の裏面９０Ｂにフォーカスする。同様にして、発振する探触子エレメントを１個づつずらして、第１７回目では、１６個の探触子エレメント１０−１７，…，１０−３２を発振させ、超音波Ｓ１７を翼９０の裏面９０Ｂにフォーカスする。このとき、１６エレメントにより放射される超音波Ｓ１の入射角θ２は、例えば、３５〜４５°となるように、シュー２０を設置している。他の超音波Ｓ２，…，Ｓ１７の入射角も同一である。
【００３７】
次に、図３を用いて、本実施形態によるガスタービン空気圧縮機翼面亀裂検査装置による検出結果について説明する。
図３は、本発明の一実施形態によるガスタービン空気圧縮機翼面亀裂検査装置の検出結果の説明図である。図３（Ａ）は、検出波形を示し、図３（Ｂ）は、検出画像を示している。
【００３８】
図３は、図１に示したＣＲＴ制御用パソコン４０によってＣＲＴ５０に表示されたガスタービン空気圧縮機翼面亀裂検査装置の検出結果を示している。図２において説明したように、孔食底部から進展した亀裂範囲に対して、１７回の探傷結果が、図３（Ｂ）に示すように、時間と個々のエレメントの受信感度による２次元表示を色調階調で表示される。この２次元の色調階調の表示により、微細な亀裂の検出において、従来の一般的な超音波のようにＡスコープ表示（波形）のように表示スコープの波形形状の特徴が何を示すかを判断しながら微少な波形変動を見つめる（専門技能を必要とする）ことなく、検査員は欠陥を容易に確認することができる。すなわち、アレイ型探触子の個々のエレメントからいくつかの焦点を連続的に発振することで、翼面上に亀裂がどのように分散しているかが色調階調として表示が可能となる。この方法により、翼面近くの亀裂の分布が容易に確認でき、検出速度を高めることを可能とする。
【００３９】
ここで、図４を用いて、従来から一般的なＡスコープの連続的な表示により亀裂を検出した検出結果について説明する。
図４は、従来から一般的なＡスコープの連続的な表示により亀裂を検出した検出結果の説明図である。図４（Ａ）は、検出波形を示し、図４（Ｂ）は、検出画像を示している。
【００４０】
図４に示すように、従来のＡスコープの連続的な表示では、亀裂の存在は判断できるが、どの程度の亀裂がどのように分散しているかはアレイ型探触子を移動しながら判断することになり、検査作業としては技能的な熟練度が必要となる。
【００４１】
次に、図５及び図６を用いて、本実施形態によるガスタービン空気圧縮機翼面亀裂検査装置による検出方法について説明する。
図５及び図６は、本発明の一実施形態によるガスタービン空気圧縮機翼面亀裂検査装置による検出方法の説明図である。なお、図１と同一符号は、同一部分を示している。
【００４２】
図５は、長手方向走査による検出方法を示している。図示するように、翼９０の長手方向（Ｘ１，Ｘ２方向）にジグザグにアレイ型探触子１０とシュー２０からなるプローブを走査して、亀裂検出を行う。
【００４３】
また、図６は、横方向走査による検出方法を示している。図示するように、翼９０の横方向にジグザグにアレイ型探触子１０とシュー２０からなるプローブを走査して、亀裂検出を行う。
【００４４】
なお、検査は、翼９０に対し、両面から実施する。また、空気圧縮機の翼面は曲面のため、シュー２０の底面の形状は、それぞれの翼面に合わせた形状としている。
【００４５】
以上説明したように、本実施形態によれば、ガスタービン空気圧縮機において翼が密集して取り付けられた状態の中で、翼の表面に発生した孔食の底部の微細亀裂を直接に容易に短時間で検出することができるため、ガスタービンの安全運用を実施できるとともに先手管理を可能する。
【００４６】
【発明の効果】
本発明によれば、孔食底部からの微細亀裂を検出することができる。
【図面の簡単な説明】
【図１】本発明の一実施形態によるガスタービン空気圧縮機翼面亀裂検査装置の全体構成を示すシステム構成図である。
【図２】本発明の一実施形態によるガスタービン空気圧縮機翼面亀裂検査装置の測定原理の説明図である。
【図３】本発明の一実施形態によるガスタービン空気圧縮機翼面亀裂検査装置の検出結果の説明図である。
【図４】従来から一般的なＡスコープの連続的な表示により亀裂を検出した検出結果の説明図である。
【図５】本発明の一実施形態によるガスタービン空気圧縮機翼面亀裂検査装置による検出方法の説明図である。
【図６】本発明の一実施形態によるガスタービン空気圧縮機翼面亀裂検査装置による検出方法の説明図である。
【符号の説明】
１０…アレイ型探触子
１０−１，１０−２，…，１０−３２…探蝕子エレメント
２０…シュー
３０…探傷装置
４０…ＣＲＴ制御用パソコン４０
５０…ＣＲＴ[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a gas turbine air compressor blade surface crack inspection method and apparatus for nondestructively detecting defects generated on a blade surface of a gas turbine air compressor, and in particular, using ultrasonic flaw detection, particularly for a blade surface. The present invention relates to a gas turbine air compressor blade surface crack inspection method and apparatus suitable for detecting a microcrack that has developed from a pitting bottom.
[0002]
[Prior art]
The blade surface of the air compressor of the gas turbine for power generation is coated with a corrosion-resistant coating on the surface to cope with corrosive components such as S and Cl in the atmosphere that are simultaneously sucked when a large amount of air is sucked. However, after many years of operation, the anti-corrosion coating has worn and peeled off, and in the humid environment upstream of the compressor, the S and Cl components in the atmosphere, along with moisture, adhere to and concentrate on the blade surface. This causes pitting corrosion.
[0003]
Conventionally, as a method for detecting this corrosion fatigue defect, a method for detecting the presence or absence of surface cracks and the size of pitting corrosion by magnetic particle inspection or the like has been used.
[0004]
[Problems to be solved by the invention]
However, as a result of the blade destructive inspection, it was confirmed that a crack occurred at the bottom of the pitting corrosion where no crack occurred on the surface of the blade. The crack generated from the bottom of this pitting corrosion generates excessively high vibration stress during the rotation of the compressor when the gas turbine for power generation is started and stopped, and this vibration stress is applied to the bottom of the pitting corrosion. It is thought that stress concentration occurs, cracks are generated and propagated from the pitting bottom, and spread to the blade surface.
[0005]
It has been found that the conventional magnetic particle inspection method has a problem that it cannot detect cracks detected from the pitting bottom. Cracks from the bottom of the pitting corrosion will be confirmed for the first time when the cracks have developed on the blade surface. At this point, it is necessary to replace the cracks as soon as possible. This is a plan for maintaining the air compressor. It was a difficult situation.
[0006]
An object of the present invention is to provide a gas turbine air compressor blade surface crack inspection method and apparatus capable of detecting fine cracks from a pitting bottom.
[0007]
[Means for Solving the Problems]
(1) In order to achieve the above object, the present invention provides a gas turbine air compressor that non-destructively inspects microcracks generated from pitting corrosion on the blade surface of a gas turbine air compressor using ultrasonic waves. in the blade surface crack testing methods, as ultrasonic probe, focusing using an array type pROBE, ultrasonic wave oscillated from該探probe within the blade surface of the test portion having a plurality of probes elements And the scanning flaw is made so that the focal point is along the blade surface at the same incident angle in the array type probe .
By this method, a fine crack from the pitting bottom can be detected.
[0008]
In (2) above (1), preferably, the array type PROBE are those whose oscillation frequency is oscillated at 17～20MHz.
[0009]
(3) In the above (1), preferably, those to be incident shear waves at 45 ° incidence angle into the blade from 35 ° from the array PROBE.
[0010]
(4) To achieve the above object, the present invention includes a蝕子probe array type for the wing-side inspection, each of the control means for varying the oscillation timings of a plurality of transducer elements constituting the array type PROBE The result detected from the probe is displayed in two dimensions at the scanning position where the focal point is scanned at the same incident angle as time.
[0011]
With such a configuration, a fine crack from the pitting bottom can be detected.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a gas turbine air compressor blade surface crack inspection method and apparatus according to an embodiment of the present invention will be described with reference to FIGS.
First, the overall configuration of the gas turbine air compressor blade surface crack inspection apparatus according to the present embodiment will be described with reference to FIG.
FIG. 1 is a system configuration diagram showing the overall configuration of a gas turbine air compressor blade surface crack inspection apparatus according to an embodiment of the present invention.
[0013]
Gas turbine air compressor blade surface crack inspection device according to the present embodiment, an array-type probe (10), the shoe 20, the flaw detector 30 is constituted by a CRT control PC 40 for controlling the image to be displayed on CRT50 ing.
[0014]
On the surface of the array probe (20), a plurality of elements for generating ultrasound are arranged in an array. The detailed configuration of the array type probe (10) will be described later with reference to FIG. Shoe 20 includes an array-type probe (10) of the surface, in order to provide a predetermined angle θ1 between the vanes (blades) 90 of the surface of the gas turbine air compressor is a material being tested, PROBE array It is attached to the surface of the child 10. The reason why the predetermined angle θ1 is given will be described later with reference to FIG.
[0015]
Array type probe (10), by moving the surface of the blade 90 in the longitudinal direction (arrow X direction), and pitting occurring on the back surface of the blade 90, to detect cracks generated from this pitting bottom . Gap G between the other wing 90 adjacent to the blade 90 to the blade 90, for example, as narrow as 29 mm, the height H2 of the array type probe (10), for example, are compact so that 27 mm. The thickness H1 of the blade 90 is, for example, 10 mm.
[0016]
Flaw detector 30 controls the ultrasonic waves generated from the array-type probe (10), also takes in the reflected wave from a defect of the blade 90 detected by the array probe (10), occurs on the back surface of the blade 90 Defects such as pitting corrosion and cracks generated from the bottom of this pitting corrosion are detected. The personal computer 40 for CRT control displays information obtained from the defect of the blade 90 detected by the flaw detection apparatus 30 on the CRT 50 as image data.
[0017]
When inspecting the gas turbine air compressor blades, for narrow inter blade contacts the blade which the signal cable to the array PROBE adjacent the damaged or arrangement of cables by sharp tip as cutlery It may not be used. Therefore, in order to prevent the cable from being damaged by the blade tip of the adjacent wing with respect to the signal cable extraction position, by attaching the signal cable so as to be parallel to the direction of the blade surface as shown in FIG. The inspection speed can be increased because attention is not paid to cable breakage.
[0018]
Next, the detection principle of the gas turbine air compressor blade surface crack inspection apparatus according to the present embodiment will be described with reference to FIG.
FIG. 2 is an explanatory diagram of the measurement principle of the gas turbine air compressor blade surface crack inspection apparatus according to one embodiment of the present invention. The same reference numerals as those in FIG. 1 denote the same parts.
[0019]
On the surface of the array probe (10), in this example, 32 PROBE elements 10-1, 10-2, 10-3, ..., 10-16,10-17, ... 10-32 array Arranged in a shape. And the surface of the array type probe (10), between the wings (blades) 90 of the surface 90F of the gas turbine air compressor which is subject material, by the shoe 20 is inclined by a predetermined angle .theta.1.
[0020]
The blade (blade) 90 of the gas turbine air compressor has a front surface 90F and a back surface 90B, and the thickness H1 is, for example, 10 mm. It is assumed that a pitting corrosion C1 and a fine crack C2 generated from the bottom of the pitting corrosion C1 are generated on the back surface 90B of the blade 90 as illustrated. The depth of the crack C2 generated from the pitting bottom generated on the surface of the blade is a fine crack of 0.1 to 0.2 mm.
[0021]
Regarding the defect detection depth and the oscillation frequency, generally, the defect detection limit is up to ½ length of the ultrasonic wavelength to be used. The sound velocity of the longitudinal wave of the test material is about 6000 m / s, and in the case of a 20 MHz ultrasonic wave, sound velocity (C) = frequency (f) × wavelength (λ),

Thus, the crack depth of 0.1 to 0.2 mm is an ultrasonic wave that can barely be detected. Therefore, from the crack depth to be inspected, the oscillation frequency of the ultrasonic wave to be used can be about 20 MHz.
[0022]
In order to detect a crack using an ultrasonic wave, it is necessary to give a strong directivity to the ultrasonic wave with respect to the crack. Increasing the directivity of the ultrasonic wave can be achieved by increasing the diameter D of the vibrator that oscillates the ultrasonic wave. When the diameter D of the vibrator is extremely small, the ultrasonic wave oscillated from a single vibrator oscillates from one point to the entire circumference as in Huygens' principle. If the vibrator is attached to a structure, an ultrasonic wave oscillates from one point toward 180 °.
[0023]
When a plurality of transducers are arranged in parallel, ultrasonic waves from each point are formed as synthesized ultrasonic waves. Ultrasonic directivity is formed in this synthesis process. When the diameter of the transducer is D, a large number of transducers at each point are installed between D, and the ultrasonic oscillations have the same time and the same phase. Such ultrasonic waves generate an ultrasonic beam at a position some distance away from the ultrasonic transducer in the ultrasonic synthesis process. This beam can be used for ultrasonic flaw detection.
[0024]
Here, the distance until a stable beam is generated from the vibrator (distance where the ultrasonic wave is unstable) is referred to as a near field, and the region where the stable beam exists is referred to as a far field. The distance from the transducer to the start of the far-field sound field (short-distance acoustic wave limit distance) X0 is obtained by the following equation.
[0025]
^{X0 = D 2 / (4 ×} λ) (mm)
Here, D is the vibrator diameter (mm), and λ is the ultrasonic wavelength (mm).
[0026]
In order to oscillate an ultrasonic wave with a frequency of 20 MHz with a vibrator diameter of 10 mm and propagate it in the same material as the test material, approximately X0 = 83 mm is required. This dimension is a dimension far exceeding the thickness of the blade of the gas turbine air compressor.
[0027]
For this reason, in order to focus the ultrasonic wave on the crack portion on the back surface of the wing, a method of installing a medium (glass or the like) through which the ultrasonic wave passes between the vibrator and the wing can be considered. In this case, the sound velocity of glass or the like is 5600 m / s, which is almost the same as that of the test material. Therefore, when the glass is installed on the front surface of the vibrator and the sensor is configured, the height of the sensor is about 90 mm. Become. On the other hand, since the distance of the blade row of the gas turbine air compressor (distance H1 in FIG. 1) is 29 mm, as described above, the sensor installed with glass or the like cannot be inserted between the blade rows, and measurement is not possible. Impossible.
[0028]
Therefore, in the present embodiment, as shown in FIG. 2, a large number of transducer elements are individually assembled with respect to the same transducer diameter of 10 mm, and the individual transducer elements 10-1,. and to use the array type probe (10) for oscillating the ultrasonic wave. As described above, ultrasonic waves can be oscillated from individual transducer elements in the direction of 180 °, but by synthesizing ultrasonic waves by adjusting the timing of vibrating individual transducers, conventional ultrasonic sensors can It is possible to eliminate the region of the near field that is generated during the ultrasonic oscillation. As described above, it is possible to inspect blades with a narrow blade interval.
[0029]
Ultrasound frequency oscillated from the array type PROBE, crack depth to be detected for 0.1~0.2mm and fine, ultrasonic wavelength is required 0.2 to 0.4 mm. The speed of sound in the wing is about 6000 m / s for longitudinal waves and about 3300 m / s for transverse waves. In order to detect a crack depth of 0.1 to 0.2 mm at this speed of sound, a frequency that oscillates with a wavelength of 0.2 to 0.4 mm or less is required.
[0030]
In the longitudinal wave, f = 30 MHz to 15 MHz from f = (6000 m / s) / (0.2 to 0.4 mm). In the transverse wave, f = 17 MHz to 8.3 MHz from f = (3300 m / s) / (0.2 to 0.4 mm). The transverse wave can be dealt with at a lower applied frequency than the longitudinal velocity than the longitudinal wave. Therefore, in order to reliably detect a crack of 0.1 mm by applying the ultrasonic wave of the transverse wave, the frequency of 17 MHz to 20 MHz is used. It was confirmed that the use of ultrasonic frequency was sufficient.
[0031]
Here, ultrasonic waves oscillated directly from array PROBE is a longitudinal wave. In this longitudinal wave, an ultrasonic wave of 30 MHz or more is required to detect a crack length of 0.1 mm, but it is actually difficult at the current production level.
[0032]
Therefore, in order to use the shear, between the outlet and the wing of the array type probe (10), it has established the shoe 20 of the shape shown in FIG. By setting the angle θ1 of the shoe 20 to an angle equal to or greater than the critical angle (27.5 °) of the longitudinal wave, for example, 29.2 °, the ultrasonic wave incident on the shoe 20 is incident on the shoe 20 from the shoe. At the time of entering the wing, the longitudinal wave component disappears and only the transverse wave component is present. Thus, by installing the shoe 20, the ultrasonic wave in the wing becomes a transverse wave, and a crack of 0.1 mm can be detected even at a frequency of 17 to 20 MHz.
[0033]
As described above, the outlet of the array PROBE for oscillating the highest frequency that can be manufactured at present (17~20MHz), by installing the shoe with an angle of more than 27.5 °, the 30MHz at the same level It became possible to put out detection ability. (Enhanced detection capability by utilizing transverse waves) by utilization of the shear wave incident angle θ2 of the ultrasonic wave into the wing from the array PROBE becomes 35 to 45 °. The highest oscillation frequency (17~20MHz), yet detect 0.1mm approximately crack using an array type PROBE dimensions that can be used in the sequence of current wing that can be manufactured at present with these measures in order to enable the shoe (27.5 ° or more) the it is necessary to oscillate the ultrasonic wave incident angle 35 to 45 ° and placed in an array type pROBE outlet, the first wing in this condition It is possible to detect cracks of about 0.1 mm that are generated in the inside.
[0034]
Ultrasonic ultrasonic waves oscillated in the ultrasonic testing method consists of a shoe having an angle of 27.5 ° or more to the ultrasonic shear waves in the child and wings array PROBE so as to focus on the blade surface crack has occurred By adjusting the sound wave, the sound pressure of the reflected echo from the crack can be increased, thereby increasing the detection ability of the fine crack.
[0035]
As described above, the array type probe (10) shown in FIG. 2, in order to allow detecting microcracks, and the oscillation frequency and 17～20MHz. Further, as shown in FIG. 2, so that focusing just below the wing backside 90B of microcracks C2 has occurred, among the 32 PROBE elements, using the 16 probe elements, Ultrasound is controlled to focus.
[0036]
Further, the flaw detection apparatus 30 sequentially moves the oscillating elements among the 32 probe elements so that the focal position also moves sequentially. That is, in the first time, 16 probe elements 10-1, 10-2,..., 10-16 are oscillated, and the ultrasonic wave S 1 is focused on the back surface 90 B of the blade 90. In the second time, the oscillating probe element is shifted by one to oscillate the 16 probe elements 10-2, 10-3,..., 10-17, and the ultrasonic wave S2 is applied to the back surface 90B of the blade 90. Focus on. Similarly, the oscillating probe elements are shifted one by one, and in the seventeenth time, 16 probe elements 10-17,..., 10-32 are oscillated, and the ultrasonic wave S17 is applied to the back surface of the wing 90. Focus on 90B. At this time, the shoe 20 is installed so that the incident angle θ2 of the ultrasonic wave S1 emitted from the 16 elements is, for example, 35 to 45 °. The incident angles of the other ultrasonic waves S2, ..., S17 are also the same.
[0037]
Next, the detection result by the gas turbine air compressor blade surface crack inspection apparatus according to the present embodiment will be described with reference to FIG.
FIG. 3 is an explanatory diagram of detection results of the gas turbine air compressor blade surface crack inspection apparatus according to the embodiment of the present invention. FIG. 3A shows a detected waveform, and FIG. 3B shows a detected image.
[0038]
FIG. 3 shows the detection result of the gas turbine air compressor blade surface crack inspection apparatus displayed on the CRT 50 by the CRT control personal computer 40 shown in FIG. As described in FIG. 2, the flaw detection result of 17 times for the crack range that has developed from the pitting bottom shows a two-dimensional display based on time and reception sensitivity of each element, as shown in FIG. Displayed in tone gradation. This two-dimensional tone gradation display shows what the characteristics of the waveform shape of the display scope indicate, such as A scope display (waveform) like conventional general ultrasonic waves, in detecting fine cracks. The inspector can easily confirm the defect without staring at a minute waveform variation (needing specialized skills) while judging. That is, by continuously oscillating the number of focal point from the individual elements of the array type PROBE, or cracking is how dispersed becomes possible to display a color gradation on the blade surface. By this method, the distribution of cracks near the blade surface can be easily confirmed, and the detection speed can be increased.
[0039]
Here, with reference to FIG. 4, a detection result obtained by detecting a crack by continuous display of a conventional A scope will be described.
FIG. 4 is an explanatory diagram of detection results obtained by detecting cracks by continuous display of a conventional A scope. FIG. 4A shows the detected waveform, and FIG. 4B shows the detected image.
[0040]
As shown in FIG. 4, in the continuous display of a conventional A-scope, the presence of cracks can be determined, is how much of the crack is how dispersed judges while moving the array PROBE Therefore, a skill level is required for the inspection work.
[0041]
Next, a detection method using the gas turbine air compressor blade surface crack inspection apparatus according to the present embodiment will be described with reference to FIGS. 5 and 6.
5 and 6 are explanatory diagrams of a detection method by a gas turbine air compressor blade surface crack inspection apparatus according to an embodiment of the present invention. The same reference numerals as those in FIG. 1 indicate the same parts.
[0042]
FIG. 5 shows a detection method by longitudinal scanning. As shown in the drawing, the crack detection is performed by scanning the probe composed of the array probe 10 and the shoe 20 in a zigzag manner in the longitudinal direction (X1, X2 direction) of the blade 90.
[0043]
FIG. 6 shows a detection method by lateral scanning. As shown in the figure, the crack detection is performed by scanning the probe comprising the array-type probe 10 and the shoe 20 in a zigzag manner in the lateral direction of the wing 90.
[0044]
The inspection is performed on both sides of the wing 90. Further, since the blade surface of the air compressor is a curved surface, the shape of the bottom surface of the shoe 20 is set to a shape matched to each blade surface.
[0045]
As described above, according to the present embodiment, in the state where the blades are densely attached in the gas turbine air compressor, the microcracks at the bottom of the pitting corrosion generated on the surface of the blade can be directly and easily performed. Since it can be detected in a short time, the gas turbine can be safely operated and advanced management is possible.
[0046]
[Effect of inventions]
According to the present invention, fine cracks from the pitting bottom can be detected.
[Brief description of the drawings]
FIG. 1 is a system configuration diagram showing the overall configuration of a gas turbine air compressor blade surface crack inspection apparatus according to an embodiment of the present invention.
FIG. 2 is an explanatory diagram of a measurement principle of a gas turbine air compressor blade surface crack inspection apparatus according to an embodiment of the present invention.
FIG. 3 is an explanatory diagram of a detection result of a gas turbine air compressor blade surface crack inspection apparatus according to an embodiment of the present invention.
FIG. 4 is an explanatory diagram of detection results obtained by detecting a crack by continuous display of a conventional A scope.
FIG. 5 is an explanatory diagram of a detection method by a gas turbine air compressor blade surface crack inspection apparatus according to an embodiment of the present invention.
FIG. 6 is an explanatory diagram of a detection method by a gas turbine air compressor blade surface crack inspection apparatus according to an embodiment of the present invention.
[Explanation of symbols]
10 ... array PROBE 10-1, ..., 10-32 ... probe蝕子element 20 ... shoe 30 ... flaw detector 40 ... CRT control PC 40
50 ... CRT

Claims (4)

In the gas turbine air compressor blade surface crack inspection method that non-destructively inspects micro cracks generated from pitting corrosion on the blade surface of the gas turbine air compressor,
As ultrasonic probe, using an array type PROBE having a plurality of probes elements, electrically as ultrasonic wave oscillated from該探probe is focused on the blade surface of the inspected part A gas turbine air compressor blade surface crack inspection method which is operated and performs scanning flaw detection so that the focal point is along the blade surface at the same incident angle in an array type probe . In the gas turbine air compressor blade surface crack inspection method according to claim 1,
The array type PROBE, the gas turbine air compressor blade surface crack inspection method characterized by oscillation frequency is oscillated at 17～20MHz. In the gas turbine air compressor blade surface crack inspection method according to claim 1,
Gas turbine air compressor blade surface crack inspection method characterized by incident shear waves at 45 ° incidence angle into the blade from 35 ° from the array PROBE. An array-type PROBE for blade surface inspection,
And control means for changing the respective oscillation timings of a plurality of transducer elements constituting the array type PROBE,
A gas turbine air compressor blade surface microcrack inspection apparatus characterized in that the result detected from the probe is displayed in two dimensions at the scanning position where the focal point is scanned at the same incident angle as time.

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