JP2012047184A - Turbine moving blade - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a turbine moving blade having a fork type blade embedding part suitable for ultrasonic flaw detection.SOLUTION: Assuming a point at which an ultrasonic wave oscillated from an ultrasonic sensor 55 enters a smooth surface 15C as an oscillation reference point P1c, an area on a blade installation surface adjacent to a projecting image of an outer fork 10a onto the blade installation surface 13 as a sensor arranging area D2, a width of the outer fork as a fork width (W3), a distance up to the oscillation reference point from an inflection point P3 of expanding the outer fork as the ultrasonic wave passing depth (H4), a point at which a straight line of contacting with a pinhole of the outer fork by passing through the inflection point from the oscillation reference point, reaches an end surface of the outer fork as an ultrasonic wave arrival point P2c, and a distance up to the oscillation reference point from the ultrasonic wave arrival point as an ultrasonic wave arrival distance (Hc), the sensor arranging area D2 is formed so that a width (W4) in the rotary axis direction satisfies "W4=H4*W3(Hc-H4)", and the smooth surface is arranged so that the oscillation reference point is positioned in the sensor arranging area D2.

Description

  The present invention relates to a turbine blade having a fork-type blade implantation portion.

  As shown in the perspective view of FIG. 1, the turbine includes a disk 1, a turbine blade (blade) 2, and a pin 3.

  The disk 1 is a disk-shaped member attached to the outer peripheral side of the rotating shaft, and has a disk fork 4 and a pin hole 5. FIG. 1A shows only a part of the disk 1 and shows a partial cross-sectional shape of the disk 1.

  The disk 1 includes a plurality of forks 6 provided so as to engage with a blade implantation portion 7 (described later) of the moving blade 2. The forks 6 of the disk 4 are arranged along the rotor axial direction on the outer edge of the disk 1 at intervals corresponding to the intervals of forks 10 (described later) of the wing implantation portion 7.

  The pin hole 5 is for inserting a pin 3 for fixing the rotor blade 2 to the disk 1. The pin hole 5 is manufactured to have the same diameter as the center of the pin hole 11 (described later) of the rotor blade 2. A plurality of pin holes 5 are provided in order to disperse stress and improve durability.

  The moving blade 2 includes a fork-type blade implantation portion (wing fork) 7, a blade attachment portion 8, and a blade portion 9.

  The blade implantation portion 7 is a portion located on the disk 1 side in a posture (blade attachment posture) in which the moving blade 2 is attached to the disk 1, and has a plurality of forks 10 and pin holes 11.

  The forks 10 are members that protrude inward in the rotor radial direction in the blade mounting posture, and a plurality of forks 10 are arranged along the rotor axial direction. The fork 10 is provided so as to engage with the fork 6 of the disk 1 and has a plurality of pin holes 11.

  The pin hole 11 is for inserting a pin 3 for fixing the rotor blade 2 to the disk 1 and is provided so as to penetrate through the plurality of forks 10 of the blade implantation portion 7 from the rotor axial direction.

  The blade attachment portion 8 is a portion having a predetermined thickness in the rotor radial direction, and is attached integrally with the blade implantation portion 7. A blade portion 9 is attached to a blade attachment surface 13 on the outer side in the rotor radial direction of the blade attachment portion 8. The blade attachment portion 8 has overhang portions 12 at both ends in the rotor axial direction. The overhanging portion 12 is a portion provided such that the end surface in the rotor axial direction protrudes compared to both end surfaces in the rotor axial direction of the blade implantation portion 7 in the blade mounting posture.

  In this type of turbine, stress is applied to the pin hole 10 as the turbine rotates, so that a crack (hereinafter referred to as a defect) may occur. For this reason, in order to confirm the reliability of the moving blade in service, the defect inspection of the fork 10 is regarded as important.

  Conventionally, the magnetic particle testing (MT) shown in FIG. 10 has been used for defect inspection of the fork 10. MT is a technique for detecting a magnetic flux leaking from the defect 44 when a magnetic field is applied to the inspection target 40 with the N magnetic pole 41 and the S magnetic pole 42, and a magnetic material coated with a fluorescent material accumulated in the leakage magnetic flux of the defect. This is a technique for detecting defects by irradiating the metal powder 43 with ultraviolet light and observing whether or not the magnetic metal powder 43 is accumulated as fluorescence emission. However, in the defect inspection by MT, it is necessary to remove the pin and disassemble the disk and the moving blade, so that there is a problem that the inspection takes time.

  Therefore, application of an ultrasonic flaw test (UT (Ultrasonic Testing)) has been studied as a technique for realizing non-decomposition inspection. As shown in FIG. 11, UT is an inspection method in which an ultrasonic wave U is transmitted into an inspection object 40 and a reflected wave is received using an ultrasonic sensor 45, and whether there is reflection from a defect 43 or not. In this case, the presence or absence of defects is evaluated. As a method for applying this UT to the fork inspection, (1) a method of reflecting ultrasonic waves in the inspection object to reach the defect as shown in FIG. 11, (2) a method of exceeding the pin hole as shown in FIG. A method is conceivable in which a sound wave is incident and converted into a surface wave to reach a defect.

  The technology for inspecting a defect of a moving blade using these UT methods includes an ultrasonic probe holder and a positioning jig for the dovetail type moving blade shown in FIG. An ultrasonic flaw detection sensor has been developed (see Patent Document 1).

JP 7-248316 A

  By the way, when performing UT by the method of (1) above, (i) the total number of reflections from the oscillation of an ultrasonic wave to reflection at a defect in order to ensure detection sensitivity (including reflection at the defect) (Ii) In order to stabilize the reflection efficiency as shown in FIG. 7, it is necessary to set the range of the ultrasonic incident angle to about 35 to 55 °.

  However, since the fork shape does not consider the propagation of ultrasonic waves, a region where the ultrasonic waves do not reach occurs due to restrictions on the number of reflections and the incident angle. Moreover, as shown in FIG. 16 showing a comparison of ultrasonic reach distances of the first embodiment and the second embodiment described later, when the UT sensor is installed on the blade installation surface, the ultrasonic reach distance becomes long. When attempting to install the UT sensor on the blade installation surface, a gap is generated between the curved surface of the blade and the sensor, making it difficult for the ultrasonic wave to enter.

  An object of the present invention is to provide a turbine rotor blade having a fork type blade implantation portion suitable for ultrasonic flaw detection.

In order to achieve the above object, the present invention provides a turbine rotor blade having a fork-type blade implantation portion, which is located at an end portion in the rotation axis direction of a plurality of forks and is an object of an ultrasonic flaw detection test. A fork, a wing attachment portion integrally attached to the wing implantation portion outside the radial direction of the rotation shaft of the wing implantation portion, and a wing on which a wing is attached on a surface on the wing attachment portion A mounting surface and a smooth surface provided on the blade mounting surface and on which the ultrasonic sensor is placed;
The point where the ultrasonic wave oscillated from the ultrasonic sensor enters the smooth surface is an oscillation reference point, and the cross-sectional shape in the rotation axis direction of the outer fork is projected onto the blade mounting surface by projecting in the radial direction of the rotation shaft. For the projection image to be formed, the area on the blade mounting surface adjacent from both sides in the rotation axis direction is the sensor installation area, the width of the outer fork in the rotation axis direction is the fork width (W3), and the outer fork is enlarged. The inflection point, the radial distance from the inflection point to the oscillation reference point in the radial direction of the rotation axis (H4), the ultrasonic reference point passing through the inflection point from the oscillation reference point The point where the straight line created so as to contact the pin hole of the fork reaches the end surface of the outer fork is the ultrasonic arrival point, and the distance in the radial direction of the rotation axis from this ultrasonic arrival point to the oscillation reference point Reach distance (Hc) When you,
The sensor installation area is formed such that the width (W4) in the rotation axis direction satisfies “W4 = H4 · W3 (Hc−H4)”, and the smooth surface is within the sensor installation area. It is assumed that the points are provided.

  According to the present invention, since ultrasonic flaw detection can be used for a turbine blade having a fork-type blade implantation portion, the reliability of the turbine blade in service can be improved.

The perspective view of a turbine provided with a fork type wing implantation part. The block diagram of the turbine rotor blade which is the 1st Embodiment of this invention. The block diagram of the UT sensor used when performing UT with the turbine rotor blade which is the 1st Embodiment of this invention. The figure which shows the method of performing UT using a UT sensor. The figure which shows an example of distribution of ultrasonic oscillation start time difference dt [s]. The relationship diagram of incident angle (theta) and the maximum reach | attainment distance L in the 1st Embodiment of this invention. The figure which shows the incident angle dependence of ultrasonic reflection efficiency. The figure which shows the dependence with respect to the fork width (W2) of the ultrasonic reach (H) at the time of W1 = 25 [mm] and S1 = 5 [mm]. The flowchart of the UT implementation procedure in the 1st Embodiment of this invention. Explanatory drawing of the defect inspection by MT. Explanatory drawing of the defect inspection by UT. Explanatory drawing of UT by the ultrasonic wave reflected within the test object. Explanatory drawing of UT by the ultrasonic wave converted into the surface wave. Explanatory drawing of the problem by the shape of the attachment position of a UT sensor. The block diagram of the turbine rotor blade which is the 2nd Embodiment of this invention. The figure which shows the dependence with respect to the protrusion part width | variety (W2) of the ultrasonic reach distance (Ha) in the case of W1 = 25 [mm] and S2 = 5 [mm]. The principle figure of the UT method which converts a transverse wave into a surface wave. The block diagram of the turbine rotor blade which is the 3rd Embodiment of this invention. The figure showing the principle of ultrasonic incident angle change using a shoe. The flowchart of the UT implementation procedure in the 3rd Embodiment of this invention. Explanatory drawing of the method of calculating | requiring the distance to a defect in the 3rd Embodiment of this invention. Explanatory drawing of the method which injects into a pin hole the ultrasonic wave which carried out the mode conversion by the side surface of a protrusion part. The figure which shows the incident angle (theta) L of a longitudinal wave, the efficiency of mode conversion, and the figure which shows the relationship between the incident angle (theta) L of a longitudinal wave, and the reflection angle (theta) T of a transverse wave. The block diagram of the turbine rotor blade which is the 4th Embodiment of this invention. The figure which shows the dependence to the fork width W3 of the sensor installation area width W4 in the 4th Embodiment of this invention. The figure which shows the form of a dovetail type turbine rotor blade implantation part. The definition figure of the length of a fork type wing implantation part. The definition figure of the length of a fork type wing implantation part.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 2 is a configuration diagram of the moving blade 2 according to the first embodiment of the present invention. 2A is a top view, FIG. 2B is a front view thereof (viewed from the rotor radial direction), and FIG. 2C is a side view thereof (viewed from the rotor axial direction). In addition, the same code | symbol is attached | subjected to the same part as the previous figure, and description is abbreviate | omitted (the following figure is also the same).

A smooth surface 15 is provided on the blade attachment surface 13 shown in this figure. The smooth surface 15 is a surface on which the UT sensor 16 on the blade attachment surface 13 is placed, and is smooth so that no gap is generated between the UT sensor 16 and the blade attachment surface 13 when the UT sensor 16 is placed. Yes. The area of the smooth surface 15 is preferably 9 mm ² or more in consideration of the size of the smallest UT sensor capable of UT. Moreover, it is preferable to set it as 100 mm < ² > or less in consideration of suppressing the occurrence of fluid turbulence that rotates the rotor blades. In addition, the size of the smooth surface 15 of the present embodiment is equal to the bottom area of the UT sensor 16 so that the alignment of the UT sensor 16 is easy, but may be larger than the bottom area of the UT sensor 16. Of course it is good.

  Next, the UT sensor 16 will be described with reference to FIGS.

FIG. 3 is a configuration diagram of the UT sensor 16 used when performing UT with the turbine rotor blade 2. In this figure, the UT sensor 16 includes a plurality of ultrasonic elements 31, an electrode 32 provided on the bottom surface of each ultrasonic element 31 facing the inspection object, and an electrode 32B provided on the upper surface of each ultrasonic element 31. A signal line 33 for applying a voltage and a damper 34 provided on the electrode 32B for absorbing the energy of the oscillated ultrasonic wave are provided. Since the damper 34 reduces the after vibration at the time of ultrasonic oscillation, the S / N can be improved. In addition, the ultrasonic element 31, the electrode 32, and the damper 34 are stored in a protective case 35. The ultrasonic element 31 is a piezoelectric element such as PZT, LiNbO ³ , PVDF, the electrode 32 and the electrode 32B is a highly conductive metal such as Au, Ag, Cu, the signal line 33 is a copper wire, and a damper. As 34, it is preferable to use what mixed metals, such as Hf, W, and Ta, with resin. The protective case 35 is preferably molded and used from one or more materials of resin and metal.

FIG. 4 is a diagram illustrating a method of performing UT using the UT sensor 16. As shown in this figure, when performing UT, the ultrasonic oscillation in each ultrasonic element 31 is started so that the ultrasonic waves simultaneously reach the convergence point 36 from a plurality of ultrasonic elements 31 arranged in parallel in the sensor 16. Adjust the time. Here, the maximum distance between the ultrasonic element 31 and the convergence point is max (L) [m], the distance between the i-th ultrasonic element 31 and the convergence point from the left in the figure is Li [m], and the propagation of the ultrasonic wave. The velocity (sound velocity) is V [m / s], the X coordinate of the i-th ultrasonic element 31 is xi [m], the Y coordinate of the i-th ultrasonic element 31 is y i [m], and the X coordinate of the convergence point is When xf [m] and the Y coordinate of the convergence point are yf [m], the distance Li [m] between the i-th ultrasonic element 31 and the convergence point, and the ultrasonic oscillation start time difference dt [ s] is expressed by the following equations (1) and (2).
Li = ((xi−xf) ² + (yi−yf) ² ) ^1/2 [m] (1)
dt = (max (L) −Li) / V [s] (2)
FIG. 5 is a diagram illustrating an example of the ultrasonic oscillation start time difference dt [s]. This figure shows that the total number of ultrasonic elements 31 is 20, V = 5780 [m / s], xi = (0.5i−0.25) × 10 −3 [mm], yi = 0 [m], xf The ultrasonic oscillation start time difference dt [s] when = 0 [m] and yf = 3 × 10 ⁻² [m] is shown. As shown in this figure, when an ultrasonic element far from the convergence point is oscillated early, the ultrasonic wave arrival time from each element to the convergence point is aligned, so that the signal intensity can be increased.

  Returning now to FIG. As shown in FIG. 2, the point on the smooth surface 15 where the center of the UT sensor 16 is placed is the oscillation reference point P1, and the end surface located on the protruding portion 12a side of the outer fork 10a is the outer end surface 20. The end face of the outer fork 10a in the rotor axial direction and located on the other fork 10 side is the inner end face 21, the overhang width is W1, the width of the outer fork 10a is the fork width W2, and the tension is from the oscillation reference point P1. The distance to the end surface of the protruding portion 12a in the rotor axial direction is defined as a sensor distance S1. As shown in the figure, W2 in the present embodiment is constant in the rotor radial direction.

  Here, when the ultrasonic wave U is oscillated from the oscillation reference point P1 to the end face 21 at an incident angle θ, the ultrasonic wave U is oscillated and then reflected by the defect in order to ensure the detection sensitivity of the reflected wave from the defect. In consideration of the necessity of making the total number of reflections up to four times or less, the distance (L) to be reached when the ultrasonic wave U is reflected in the outer fork 10a is the following using W1, W2, and S1. It is given by equation (3).

L = (W1-S1 + 4W2) / tan θ (3)
In addition, when W1, W2, and S1 are fixed in this expression (3) and the incident angle θ (θ1 <θ2) is increased, the reach distance L (L1> L2) is decreased as shown in FIG. Further, when the reach distance L represented by the above formula (3) is limited to a range of 35 to 55 ° where the reflection efficiency is stable as shown in the incident angle dependence of the reflection efficiency of the ultrasonic wave in FIG. As shown in the following equation (4), the maximum value (Lmax) is obtained when θ = 35 °.

Lmax = (W1-S1 + 4W2) / tan35 ° (4)
Here, the longest arrival point where the ultrasonic wave from the UT sensor 16 needs to reach on the outer fork 10a is P2, and the distance in the rotor radial direction from P1 to P2 is the required arrival distance H. At this time, in order to make the ultrasonic wave U reach P2, the maximum arrival distance Lmax may be set to be larger than the required arrival distance H (that is, “H ≦ Lmax”). As a result, the turbine rotor blade 2 of the present embodiment is formed so that the required reach distance H, the overhang width W1, the fork width W2, and the sensor distance S1 satisfy the following formula (5).

tan35 ° ≦ (W1−S1 + 4W2) / H (5)
FIG. 8 is a diagram showing the dependence of the ultrasonic reach distance (H) on the fork width (W2) when W1 = 25 [mm], S1 = 5 [mm], and θ = 35 [°]. The straight line in FIG. 8 is drawn by the formula (H ≦ (20 + 4W2) / tan35 °) in which W1 = 25 [mm], S1 = 5 [mm], and θ = 35 [°] are substituted into the formula (5). It is. For example, when H = 100 [mm], it is understood that W2 needs to be about 12.5 [mm] or more.

  By the way, since a defect occurs around the pin hole 11, the necessary reach distance H is the position of the pin hole 11a in the above.

Moreover, in said embodiment, it is good to determine the thickness of the overhang | projection part 12a as follows. Here, assuming that the depth reached when the ultrasonic wave U oscillated from P1 to P2 shown in FIG. 2 passes through the overhanging portion 12a is the overhanging portion passage depth (H1), H1 is the blade mounting surface. 13 is represented by “H1 = (W1−S1) / tan θ”. Thereby, for example, in the example of FIG. 8 (W1 = 25, D1 = 5, θ = 35 °), H1 is about 28.7 [mm]. Note that the range of H1 takes into account the stability of the reflection efficiency of ultrasonic waves.
“(W1-S1) / tan 55 ° ≦ T1 ≦ (W1-S1) / tan 35 °”. Therefore, if the thickness of the overhanging portion 12a at the position of the outer end surface 20 of the outer fork 10a is defined as the overhanging portion minimum thickness (T1), “H1 ≦ T1” may be satisfied. If the overhanging portion 12a is formed in this manner, the ultrasonic wave U can be introduced into the outer fork 10a without being reflected within the overhanging portion 12a.

  FIG. 9 is a flowchart of the UT implementation procedure in this embodiment. As shown in this figure, in order to implement UT in the present embodiment, first, the shape of the wing implantation part 7 (the outer fork 10a and the overhanging part 12a), the ultrasonic element 31 in the UT sensor 16, and The ultrasonic oscillation start time difference dt is obtained from the position and the equations (1) and (2) (S201). Next, the UT sensor 16 is installed on the smooth surface 15, and an ultrasonic wave is oscillated using the time difference dt obtained in S201 to acquire an ultrasonic flaw detection signal (S202). Finally, the presence / absence of a defect in the blade implant portion 7 is evaluated from the measurement result of the ultrasonic flaw detection signal, and the UT is terminated (S203).

  Next, the effects of the present embodiment will be described with reference to comparative examples.

  Conventionally, magnetic particle testing (MT) has been used for defect inspection of fork-type turbine rotor blade implants. However, when this defect inspection by MT is used for a turbine rotor blade having a fork type blade implantation portion, there is a problem that it takes time to inspect because it is necessary to remove the pin and disassemble the disk and the rotor blade. Therefore, an inspection technique using UT has been developed as a technique for realizing non-disassembly inspection. The UT is an inspection method that transmits an ultrasonic wave U into an inspection object and receives a reflected wave using an ultrasonic sensor, and evaluates the presence / absence of a defect depending on whether there is reflection from the defect. . As a method of this UT, there is a method of reflecting the ultrasonic wave U in the inspection object 40 shown in FIG. However, when performing UT by this method, (i) the total number of reflections (including reflection at the defect) within 4 times from when the ultrasonic wave is oscillated until it is reflected by the defect to ensure detection sensitivity is within 4 times (Ii) In order to stabilize the reflection efficiency, it is necessary to set the range of the ultrasonic reflection angle to about 35 to 55 °. Due to this restriction, there was a case where the ultrasonic wave could not reach the defect 43.

  On the other hand, the turbine rotor blade of the present embodiment has a smooth surface 15 on which the ultrasonic sensor 16 is placed on the blade attachment surface 13, and between W1, W2, S1, and H, “ tan35 ° ≦ (W1−S1 + 4W2) / H ”is established. When the turbine rotor blade is formed in this way, the above condition (i) (ii) is also obtained when an ultrasonic wave is oscillated at a point (the longest arrival point P2) located on the innermost side in the rotor radial direction among the portions where UT is required. ) Is satisfied, it is possible to reach the ultrasonic wave also in the portion located on the inner side in the rotor radial direction from P2. As a result, even if a defect occurs during the operation of the turbine blade having the fork-type blade implantation portion, it becomes easy to find by the UT, so that the reliability of the turbine blade in service can be improved.

  Next, a second embodiment of the present invention will be described.

  The turbine rotor blade 2A of the present embodiment is different from the turbine rotor blade 2 of the first embodiment in that the UT sensor 16 is attached to the outer end face in the rotor radial direction of the overhang portion 12a.

  FIG. 15 is a configuration diagram of a turbine rotor blade 2A according to the second embodiment of the present invention. 15A is a top view of the turbine blade 2A, FIG. 15B is a front view thereof (viewed from the rotor radial direction), and FIG. 15C is a side view thereof viewed from the rotor axial direction. ). In addition, the wing | blade part 9 is abbreviate | omitted in this figure.

In this figure, the end surface of the overhanging portion 12a in the rotor radial direction is provided smoothly, and the UT sensor 16 is detachably mounted on the end surface. Further, in this figure, a point on the end surface of the overhanging portion 12a in the radial direction of the rotor where the center of the UT sensor 16 is placed is set as an oscillation reference point P1a, and a distance from P1a to the blade mounting surface 13 is defined as a point. The sensor distance is S2. At this time, the distance (maximum reach distance La) from the point where the ultrasonic wave U oscillated at the incident angle θ in P1a is reflected for the fourth time in the outer fork 10a to the blade mounting surface 13 is the overhang width W1, the fork Using the width W2 and the sensor distance S2, it is given by the following equation (6).
La = (W1 + 4W2) / tan θ + S2 (6)
As in the first embodiment, considering that the maximum reach distance La is substantially the maximum when θ = 35 ° from the stability of the reflection efficiency of ultrasonic waves, the rotor from the blade mounting surface 13 to the longest reach point P2 The required distance Ha in the radial direction may be set so as to satisfy the following formula (8).

Ha ≦ (W1 + 4W2) / tan35 ° + S2 (8)
FIG. 16 is a diagram illustrating the dependence of the ultrasonic reach distance (Ha) on the fork width (W2) at W1 = 25 [mm], S2 = 5 [mm], and θ = 35 [°]. In this figure, when Ha = 100 [mm], it is understood that W2 needs to be about 10.4 [mm] or more.

  Also, the one-dot broken line in FIG. 16 is reference data of the ultrasonic reach distance of the first embodiment in the same wing implantation part shape. This broken line is drawn by the formula (Ha ≦ (25−5 + 4W2) / tan 35 °) in which W1 = 25 [mm], S1 = 5 [mm], and θ = 35 [°] are substituted into the formula (4). . As described above, in the second embodiment, the ultrasonic reach distance is shorter than that in the first embodiment. However, according to the turbine rotor blade 2A of the present embodiment configured as described above, the UT can be performed without providing a smooth surface on the blade mounting surface 13 as in the first embodiment. Therefore, UT can be implemented even when it is difficult to provide a smooth surface on the blade attachment surface 13.

  Next, a third embodiment of the present invention will be described.

  The difference between the turbine rotor blade 2B of the present embodiment and the turbine rotor blade of each of the above embodiments is that the transverse wave is converted into a surface wave (Rayleigh wave) to perform UT.

  FIG. 17 shows the principle of this UT method. As shown in this figure, when performing a UT by converting a transverse wave into a Rayleigh wave, an ultrasonic wave U is oscillated so as to be in contact with the surface of the pin hole. In this figure, the tangent line 50 is a straight line created so as to be in contact with the surface of the pin hole 11 from the oscillation position of the ultrasonic wave U, and the contact point 51 is a point where the straight line 50 is in contact with the pin hole 11. The transverse wave 52 is oscillated so as to travel on the tangent line 50, and contacts the surface of the pin hole 11 at the contact point 51. The transverse wave 52 in contact with the surface of the pin hole 11 at the contact point 51 becomes a Rayleigh wave 53 and propagates through the surface of the pin hole 11 and reaches the defect 54 formed on the surface of the pin hole 11. In order to generate a Rayleigh wave in the pin hole 11, it is necessary that a vibration component in the radial direction of the pin hole 11 is included in the ultrasonic wave U. Therefore, the ultrasonic wave U has a side surface as shown in FIG. It has a component that vibrates in the figure (ie, a transverse wave component).

  Below, the method to inject the ultrasonic wave U which has a transverse wave component directly into the surface of the pin hole 11 is demonstrated first.

  FIG. 18 is a configuration diagram of a turbine rotor blade 2B according to the third embodiment of the present invention. 18A is a top view of the turbine rotor blade 2B, FIG. 18B is a front view thereof (viewed from the rotor radial direction), and FIG. 18C is a side view thereof viewed from the rotor axial direction. ). The cross-sectional shape of the fork 10 in the rotor axial direction is projected onto the blade attachment surface 13 in the rotor radial direction. At this time, the smooth surface 15B is provided such that the oscillation reference point P1b is positioned within the cross-sectional shape (referred to as cross-sectional shape D1) of the fork 10 projected onto the blade attachment surface 13. That is, the smooth surface 15B of the present embodiment is provided on the blade attachment surface 13 so that the oscillation reference point P1b is located on the outer side in the rotor radial direction with respect to the end surface 60 of the fork 10 shown in FIG. Yes. When the smooth surface 15B is formed in this way, the ultrasonic wave U can be directly incident on the pin hole 11, so that UT using Rayleigh waves can be performed.

A turbine rotor blade 2B shown in FIG. 18 has a smooth surface 15B on which an ultrasonic sensor (UT sensor) 55 is placed on the blade attachment surface 13. The UT sensor 55 is a single probe type using a single ultrasonic element, and adjusts the ultrasonic incident angle θ by inserting the shoe 56 between the ultrasonic transmission element and the test body. FIG. 19 is a configuration diagram of a shoe used for the UT of the turbine rotor blade of the present embodiment. As shown in this figure, the shoe 56 is formed in a wedge shape having an inclined surface 57 inclined at an angle θ1, and is placed on the smooth surface 15B. A UT sensor 55 is fixed on the slope 57 with screws or the like. The ultrasonic velocity in the shoe 56 is V1, the ultrasonic velocity in the inspection object (turbine rotor blade 2B) is V2, and the ultrasonic incident angle in the inspection object is θ2. At this time, the following formula (9) is established from Snell's law.
sin θ1 / V1 = sin θ2 / V2 (9)
Therefore, when adjusting the ultrasonic incident angle θ2 with respect to the smooth surface 15B to a desired angle, the ultrasonic wave may be oscillated using the shoe 56 having the angle θ1 that satisfies the equation (9). Further, it is preferable to use acrylic or the like as the material of the shoe 56.

  FIG. 20 is a flowchart of the UT implementation procedure in this embodiment. As shown in this figure, in order to implement UT in this embodiment, first, the ultrasonic wave U is applied to the smooth surface 15B from the inclination of a straight line passing through the oscillation reference point P1b and in contact with the surface of the pin hole 11. The incident angle θ2 is obtained (S211). If the ultrasonic wave U is incident at the incident angle θ2 determined in this way, the ultrasonic wave U is converted into a Rayleigh wave on the surface of the pin hole 11. Next, the incident angle θ2 obtained in S211, the ultrasonic velocity V1 in the shoe 56, and the ultrasonic velocity V2 in the turbine rotor blade 2B are substituted into the equation (9), and the inclination angle of the shoe 56 is calculated. θ1 is obtained (S212). Then, the shoe 56 having the angle θ1 obtained in S212 and having the UT sensor 55 fixed on the inclined surface 57 is placed on the smooth surface 15B, and an ultrasonic wave is oscillated to acquire an ultrasonic flaw detection signal. Finally, the presence / absence of a defect in the blade implantation part 7 (fork 10) is evaluated from the measurement result of the ultrasonic flaw detection signal, and the UT is terminated (S213).

  According to the turbine rotor blade 2 </ b> B configured as described above, the ultrasonic wave U can be directly incident on the surface of the pin hole 11 through the smooth surface 15 </ b> B provided on the blade attachment surface 13. Thereby, the transverse wave component of the ultrasonic wave U can be converted into the Rayleigh wave by the pin hole 11 and propagated on the surface of the pin hole 11. As a result, even if a defect occurs during the operation of the turbine blade having the fork-type blade implantation portion, it becomes easy to find by the UT, so that the reliability of the turbine blade in service can be improved.

  In the present embodiment, a method for obtaining the distance from the UT sensor 55 to the defect by comparing the ultrasonic flaw detection signal obtained when there is no defect and the ultrasonic flaw detection signal obtained when there is a defect. Will be described with reference to FIG. FIG. 21A shows the case where there is no defect, and FIG. 21B shows the case where there is a defect. In this figure, the incident point of the transverse wave 61 with respect to the pin hole 11 is set as A point, the side surface of the fork 10 is set as B point, and the position of the defect 63 on the pin hole is set as C point. It is known that when the surface on which the Rayleigh wave propagates is not a plane, the propagation speed of the Rayleigh wave varies depending on the curvature (curvature, etc.) of the curved surface. Even when the propagation speed of Rayleigh waves is not known, the propagation time from the ultrasonic incident point (point A) to the end face (point C) of the fork 10 and the defect (point B) from the ultrasonic incident point (point A) ), The ratio of the length of the arc AB and the arc AC can be obtained. Therefore, the distance to the defect can be obtained based on the ratio of the lengths of the arc AB and the arc AC.

  In the above description, the method of directly injecting the ultrasonic wave U into the pin hole 11 has been described. However, the ultrasonic wave formed by the longitudinal wave component is once incident on the side surface of the fork 10, and the longitudinal wave component is converted into the transverse wave component by mode conversion. Then, a method of entering the pin hole 11 may be used. Next, this method will be described with reference to FIGS.

  FIG. 22 is an explanatory diagram of a method for injecting an ultrasonic wave that has undergone mode conversion on the side surface of the fork 10 into the pin hole, FIG. 23A is a diagram illustrating an incident angle θL of longitudinal waves and efficiency of mode conversion, and FIG. These are the figures which show the relationship between the incident angle (theta) L of a longitudinal wave, and the reflection angle (theta) T of a transverse wave.

In FIG. 22, ultrasonic waves composed of longitudinal wave components are incident on the smooth surface 15B at an incident angle θ2 (θ2 + θL = 90 °) and incident on the side surface of the fork 10 at an incident angle θL. The ultrasonic wave (longitudinal wave component) incident on the fork 10 at an incident angle θL is
sin (θT) ÷ VS = sin (θL) ÷ VL (11)
Is converted into a transverse wave based on the reflection angle θT and reflected at a reflection angle θT.

  For example, when a longitudinal ultrasonic wave is incident at θ2 = 30 ° from the smooth surface 15B to be inspected with VS = 3100 [m / s] and VL = 6100 [m / s], the longitudinal wave is incident on the side surface of the fork 10. The angle θL is 60 °. Thus, when a longitudinal wave is incident at an incident angle of 60 °, the mode conversion efficiency to a transverse wave in the fork 10 is set to 90% or more as shown in FIG. 23A, and the mode conversion is efficiently performed. Further, the transverse wave after the mode conversion is reflected at about 30 ° as shown in FIG. Therefore, it is understood that if a longitudinal wave is incident on the smooth surface 15B at an incident angle of 30 °, a transverse wave that is geometrically suitable for flaw detection is generated with respect to the pin hole 11. As described above, when performing UT by mode conversion from a longitudinal wave to a transverse wave, the incident angle θ2 may be determined in consideration of the mode conversion efficiency and the reflection angle θT, and the ultrasonic wave may be incident on the pin hole 11.

  In the above description, the method of using the single probe type UT sensor 55 has been described. In this embodiment, the array type UT sensor 16 as in the first and second embodiments is used to start oscillation. Needless to say, ultrasonic waves may be incident with a time difference (dt).

  Next, a fourth embodiment of the present invention will be described.

  The difference between the turbine rotor blade 2 </ b> C of the present embodiment and the third embodiment is the installation location of the UT sensor 55.

  FIG. 24 is a configuration diagram of a turbine rotor blade 2C according to the fourth embodiment of the present invention. 24A is a top view of the turbine rotor blade 2C, FIG. 24B is a front view thereof (viewed from the rotor radial direction), and FIG. 24C is a side view thereof viewed from the rotor axial direction. ). The turbine rotor blade 2C shown in this figure includes a smooth surface 15C in which an oscillation reference point P1c is set in any of the regions D2 provided on the blade attachment surface 13. The smooth surface 15C is a smooth surface provided on the blade attachment surface 13, and is a surface on which the ultrasonic sensor 55 or the shoe 56 to which the ultrasonic sensor 55 is fixed is placed. The oscillation reference point P1c is a point where the ultrasonic wave U oscillated from the UT sensor 55 enters the smooth surface 15C. The smooth surface 15C is provided on the blade attachment surface 13 so that the oscillation reference point P1c is located in the sensor installation region D2.

  As shown in FIG. 24B, the width of the fork 10 in the rotor radial direction is W2, the portion where W2 is expanded is P3, the distance in the rotor radial direction from P3 to P1c is the ultrasonic wave passing depth H4, and P3 is A point where the straight line that contacts the pin hole 11b reaches the end face of the fork 10 is defined as an ultrasonic arrival point P2c, and a point that the straight line that passes through P3 and contacts the pin hole 11b reaches the blade mounting surface 13 is defined as P1cm. Is the ultrasonic reach distance Hc. In the present embodiment, the fork width W3 is constant in the rotor radial direction, and the ultrasonic wave passage depth H4 corresponds to the thickness of the blade attachment portion 8 at the position of the end surface of the fork 10 in the rotor axial direction. . Here, P1cm is a point on the boundary line of the region D2. At this time, the width W4 in the rotor axial direction of the sensor installation region D2 is given by the following equation (10).

W4 = H4 · W2 / (Hc−H4) (10)
When the sensor installation region D2 having the width W4 is set in this way and the smooth surface 15C is provided so that P1c is located in the region, the ultrasonic wave U is applied to the plurality of pin holes 11 provided in the fork 10. Can be directly incident. As a result, even if a defect occurs during the operation of the turbine blade having the fork-type blade implantation portion, it becomes easy to find by the UT, so that the reliability of the turbine blade in service can be improved.

  FIG. 25 is a diagram showing the dependence of the sensor installation area width W4 on the fork width W3. FIG. 25A shows the case where the ultrasonic passage depth H4 is constant (30 [mm]), and FIG. 25B shows the difference between the ultrasonic reach distance Hc and the ultrasonic passage depth H4 (this In the embodiment, the length of the fork 10) “Hc−H4” is constant (80 [mm]). As shown in this figure, when the fork width W3 is increased, the sensor installation region width W4 can be increased. Thus, according to the present embodiment, the degree of freedom of the installation position of the UT sensor can be increased as compared with the third embodiment.

  By providing the smooth surface 15C in this way, the ultrasonic wave U oscillated from the ultrasonic sensor 55 can be directly incident so as to be in contact with the surface of the pin hole 11b, as in the third embodiment. In addition, if the ultrasonic wave U can be incident on the pin hole 11b closest to the rotor in this way, the ultrasonic wave U can also be incident on the other pin hole 11 positioned on the outer side in the rotor radial direction from the pin hole 11b. Therefore, the UT can be performed on all the pin holes 11 provided in the fork 10. In particular, according to the present embodiment, the range in which the smooth surface can be provided can be expanded as compared with the case of the third embodiment, so the degree of freedom of the smooth surface installation position can be improved. Thereby, for example, even when there is a possibility of disturbing the flow of the working fluid at the installation position of the third embodiment, this embodiment may solve this.

  In the present embodiment, the method for obtaining the distance from the UT sensor 55 to the defect and the UT method using mode conversion on the side surface of the fork 10 described in the third embodiment are described in the present embodiment. Of course, it can also be applied. Of course, the array-type UT sensor 16 can also be used in this embodiment.

DESCRIPTION OF SYMBOLS 1 Disc 2 Turbine blade 3 Pin 4 Disc fork 5 Pin hole 6 Fork 7 of disc 1 Wing implantation part 8 Wing attachment part 9 Wing part 10 Fork 10a Outer fork 11 Pin hole 11a Pin hole 12 nearest to rotor 12 Overhang part 12a Overhang portion 13 Blade mounting surface 15 Smooth surface 15B Smooth surface 15C Smooth surface 16 UT sensor 20 Outer end surface 21 Inner end surface 31 Ultrasonic element 32 Electrode 32B Electrode 33 Signal line 34 Damper 35 Protective case 36 Convergence point 40 Inspection target 41 N Magnetic pole 42 S magnetic pole 43 Magnetic metal powder 44 Defect 45 Ultrasonic sensor 50 A straight line 51 formed so as to contact the surface of the pin hole 11 from the oscillation position of the ultrasonic wave U A point 52 where the straight line 50 contacts the pin hole 11 52 A transverse wave 53 A Rayleigh wave 55 UT sensor 56 shoe 57 slope 60 on shoe end surface 61 of fork 10 transverse wave W1 overhang width W2 Protrusion width W3 Protrusion width W4 Sensor installation area width S1 Sensor distance S2 Sensor distance θ Incident angle H Required reach distance H1 Overhang passage depth H4 Ultrasonic passage depth Hc Ultrasonic reach distance D1 Cross-sectional shape D2 Sensor placement area T1 Overhang portion minimum thickness A point Incident point B of transverse wave 61 Side C point of fork 10 Position of defect 63 on pin hole P1 Oscillation reference point P1b Oscillation reference point P1c Oscillation reference point P2 Longest arrival point P3 W3 is expanded The point where the straight line that passes through the location P1cm P3 and contacts the pin hole 11b reaches the blade mounting surface 13

Claims (1)

In a turbine blade having a fork-type blade implantation part,
An outer fork that is located at the end in the direction of the rotation axis among the plurality of forks and is subject to ultrasonic flaw detection;
A wing attachment portion integrally attached to the wing implantation portion on the outer side in the radial direction of the rotation axis of the wing implantation portion;
A surface on the wing mounting portion, and a wing mounting surface to which the wing is mounted;
Provided on the blade mounting surface, and a smooth surface on which the ultrasonic sensor is placed,
The point at which the ultrasonic wave oscillated from the ultrasonic sensor enters the smooth surface is an oscillation reference point,
With respect to the projection image formed on the blade attachment surface by projecting the cross-sectional shape of the outer fork in the rotation axis direction in the radial direction of the rotation shaft, on the blade attachment surface adjacent from both sides in the rotation axis direction. The area is the sensor installation area,
The width of the outer fork in the rotation axis direction is the fork width (W3),
An inflection point where the outer fork expands,
The distance in the radial direction of the rotating shaft from the inflection point to the oscillation reference point is the ultrasonic wave penetration depth (H4),
An ultrasonic wave arrival point at which a straight line formed so as to contact the pin hole of the outer fork through the inflection point from the oscillation reference point reaches the end surface of the outer fork,
When the distance in the radial direction of the rotation axis from the ultrasonic arrival point to the oscillation reference point is the ultrasonic arrival distance (Hc),
In the sensor installation area, the width (W4) in the rotation axis direction is W4 = H4 · W3 (Hc−H4)
Is formed to satisfy
The turbine blade according to claim 1, wherein the smooth surface is provided so that the oscillation reference point is located in the sensor installation region.

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