Patent ID: 12200846

DESCRIPTION OF EMBODIMENTS

First Embodiment

Hereinafter, a turbine blade1and a high-frequency hardening apparatus100according to a first embodiment of the present disclosure will be described with reference toFIGS.1to6.

(Configuration of Turbine Blade)

The turbine blade1is used as a low-pressure stage rotor blade of a steam turbine, for example. As shown inFIG.1, the turbine blade1includes a blade body11and a blade root12. The blade body11extends in a blade height direction Dh, and the sectional shape thereof as seen in the blade height direction Dh is an airfoil-like shape. Specifically, a section of the blade body11has an arc shape extending from a trailing edge ET to a leading edge EL. In addition, one (concave surface Sp) of two surfaces connecting the leading edge EL and the trailing edge ET to each other is recessed in a curved surface shape. The other of (convex surface Sn) the surfaces is swollen in a curved surface shape. A black coating film Lb is formed on the surface of the blade body11. The black coating film Lb is a thin film formed of a black paint.

Furthermore, the blade body11is three-dimensionally twisted from one side toward the other side in the blade height direction Dh. Specifically, the blade body11is twisted in a circumferential direction around the blade height direction Dh from a tip11T side toward the blade root12side. Therefore, a direction in which a straight line (chord line) connecting the leading edge EL and the trailing edge ET to each other extends changes from the tip11T side toward the blade root12side. The blade root12is provided with a serration12S, of which the sectional shape is like fir-tree serrations, so that the blade body11is attached to a blade groove formed on a disk (not shown) of the rotor.

(Configuration of High-Frequency Hardening Apparatus)

The high-frequency hardening apparatus100performs hardening processing with respect to the turbine blade1through quenching. As shown inFIG.2, the high-frequency hardening apparatus100includes a stand2, an induction heating coil3, a moving mechanism4, a rotating mechanism5, a temperature detection unit6, an alarm temperature detection unit7, an electrical current supply unit8, and a control device90.

The stand2has a stand body21having a plate shape for supporting the turbine blade1and fixation members22respectively provided on both ends of the stand body21. On a mounting surface2S of the stand2, the turbine blade1is immovably fixed by the fixation members22from both sides in the blade height direction Dh. When being fixed to the stand2, the turbine blade1is in a state in which the convex surface Sn faces an upper side.

(Configuration of Induction Heating Coil)

The induction heating coil3performs quenching by performing heating processing on the leading edge EL of the turbine blade1fixed onto the stand2by means of a high-frequency electrical current supplied from the electrical current supply unit8. As shown inFIG.3, the induction heating coil3includes a U-shaped portion31, linear portions32, and connecting portions33. The U-shaped portion31sandwiches an edge on the leading edge EL side from both sides in a thickness direction. The U-shaped portion31is curved in a U-shape to extend from the convex surface Sn side to the concave surface Sp side via the leading edge EL. It is desirable that the U-shaped portion31extends from the leading edge EL to the trailing edge ET by one-third of the chord length.

The linear portions32are provided on both sides of the turbine blade1to form a pair and extend to be parallel with the U-shaped portion31while being separated from the U-shaped portion31in the blade height direction Dh. Note that, being “parallel” means being substantially parallel, and design tolerances and manufacturing errors are allowed. The connecting portions33connect end portions of the U-shaped portion31that are on the trailing edge ET side and end portions of the linear portions32that are on the trailing edge ET side to each other in the blade height direction Dh. In addition, an iron core C is provided at an intermediate position on the connecting portion33on the convex surface Sn side. The iron core C is provided to increase a magnetic flux density of a magnetic field generated by the induction heating coil3. The induction heating coil3may be in contact with a surface of the turbine blade1and may be disposed with a slight gap provided therebetween.

(Configuration of Moving Mechanism)

As shown inFIG.2, the moving mechanism4supports the induction heating coil3and moves the induction heating coil3in the blade height direction Dh. Specifically, the moving mechanism4includes a rail41extending in the blade height direction Dh, a first moving portion42movable along the rail41, and a second moving portion43supported by the first moving portion42. The first moving portion42extends upward from the rail41. A second moving portion43is provided on a surface of the first moving portion42that is on one side in the blade height direction Dh. The second moving portion43is movable vertically along the first moving portion42. The above-described induction heating coil3is supported by the second moving portion43. The induction heating coil3extends from the second moving portion43toward the turbine blade1. When the first moving portion42is moved, the induction heating coil3moves relative to the turbine blade1in the blade height direction Dh. Furthermore, when the second moving portion43is moved, the induction heating coil3moves relative to the turbine blade1in the vertical direction. Although details will be described later, the operation of the moving mechanism4is controlled by the control device90.

(Configuration of Rotating Mechanism)

Here, as described above, the turbine blade1is three-dimensionally twisted from the one side toward the other side in the blade height direction Dh. Therefore, there is a probability that relative positions of the induction heating coil3and the turbine blade1cannot be maintained if only the moving mechanism4is provided. Therefore, the high-frequency hardening apparatus100according to the present embodiment is provided with the rotating mechanism5that rotates the stand2. The rotating mechanism5can rotate the stand2around a rotation axis Ax extending in the blade height direction Dh. The operation of the rotating mechanism5is controlled by the control device90which will be described later.

(Temperature Detection Unit)

Next, the temperature detection unit6will be described. The temperature detection unit6detects the temperature of a portion of the turbine blade1that is in the vicinity of the induction heating coil3. More specifically, as shown inFIG.3, a position (detection point P) where the temperature detection unit6detects the temperature is within a region surrounded by the U-shaped portion31, the linear portion32, and the connecting portion33on the convex surface Sn. That is, the temperature detection unit6detects a local temperature on the convex surface Sn. As the temperature detection unit6, an optical fiber type radiation temperature sensor capable of detecting the temperature of the detection point P in a non-contact manner is preferably used. In addition, the temperature detection unit6is supported and fixed with respect to the above-described moving mechanism4(second moving portion43) via a supporting part61. Therefore, when the moving mechanism4is moved, the temperature detection unit6moves relative to the turbine blade1together with the induction heating coil3. The value of a temperature (detection value) detected by the temperature detection unit6is transmitted to the control device90in the form of an electric signal.

(Configuration of Alarm Temperature Detection Unit)

The alarm temperature detection unit7is another detection device provided separately from the temperature detection unit6described above. The alarm temperature detection unit7detects a temperature distribution in a range wider than a temperature detection target range of the temperature detection unit6. The above-described detection point P is within this range. As the alarm temperature detection unit7, an optical fiber type radiation temperature sensor is also preferably used. The value of a temperature (detection value for alarm) detected by the alarm temperature detection unit7is transmitted to the control device90in the form of an electric signal.

(Configuration of Control Device)

As shown inFIG.4, the control device90is a computer that includes a central processing unit (CPU)91, a read only memory (ROM)92, a random access memory (RAM)93, a hard disk drive (HDD)94, and a signal receiving module95(I/O: Input/Output). The signal receiving module95receives electric signals (each detection value) from the temperature detection unit6and the alarm temperature detection unit7. The signal receiving module95may receive an amplified signal via, for example, a charge amplifier or the like.

As shown inFIG.5, the CPU91of the control device includes a controller81, a storage unit82, a determination unit83, a movement controller84, and an electrical current controller85by executing a program that is stored therein in advance. The controller81controls other functional units provided in the control device90. The storage unit82stores a threshold value (upper limit value) for each detection value of the temperature detection unit6and the alarm temperature detection unit7described above. Furthermore, the storage unit82stores a table showing a relationship between position coordinates in the blade height direction of the turbine blade1and a twist angle of the turbine blade1. The determination unit83determines whether or not each detection value exceeds the threshold value. The electrical current controller85controls the magnitude of a high-frequency electrical current supplied from the electrical current supply unit8to the induction heating coil3based on a result of determination performed by the determination unit83.

(Operation of Control Device)

Next, an example of processing performed by the control device90will be described with reference toFIG.6. As shown in the figure, the processing includes an operation determination step S1, a quenching step S2, a temperature detection step S31, an alarm temperature detection step S32, a first determination step S41, a second determination step S42, an electrical current adjustment step S51, and an alarm step S52.

In the operation determination step S1, it is determined whether or not the high-frequency hardening apparatus100is in a state of being operated under supervision of the temperature detection unit6and the alarm temperature detection unit7. In a case where it is determined that the high-frequency hardening apparatus100is not in an operation state, the processing is terminated (step S1: No). On the other hand, in a case where it is determined that the high-frequency hardening apparatus100is in the operation state (step S1: Yes), the quenching step S2, which is a subsequent step, is performed.

In the quenching step S2, quenching is performed by means of a high-frequency electrical current supplied to the induction heating coil3from the electrical current controller85. At this time, the movement controller84controls the operations of the moving mechanism4and the rotating mechanism5while referring to the above-described table stored in the storage unit82. That is, the moving mechanism4moves the induction heating coil3in the blade height direction Dh along the leading edge EL, and the rotating mechanism5rotates the stand2based on the twist angle of the leading edge EL. When the quenching step S2is performed once, quenching is performed for a predetermined time or a predetermined movement distance. After the predetermined time elapses or the quenching is finished for the predetermined movement distance, the temperature detection step S31and the alarm temperature detection step S32are performed in parallel.

In the temperature detection step S31, the temperature detection unit6detects the temperature of the above-described detection point P which is set on the convex surface Sn of the turbine blade1. After the temperature detection step S31, the first determination step S41is performed. In the first determination step S41, it is determined whether or not a detection value obtained in the temperature detection step S31exceeds a predetermined value.

In a case where it is determined in the first determination step S41that the detection value exceeds the predetermined value (step S41: Yes), the electrical current adjustment step S51, which is a subsequent step, is performed. In the electrical current adjustment step S51, the controller81issues a command to the electrical current controller85to reduce the magnitude of the electrical current. Accordingly, the heating temperature of the induction heating coil3is lowered. After the electrical current adjustment step S51, the processing returns to the quenching step S2described above. Accordingly, quenching is performed again for a predetermined time or a predetermined moving distance.

On the other hand, in a case where it is determined in the first determination step S41that the detection value does not exceed the predetermined value (step S41: No), the processing returns to the above-described quenching step S2again without the electrical current adjustment step S51being performed. Accordingly, quenching is performed again for a predetermined time or a predetermined distance. Such a cycle is repeated over the entire leading edge EL.

In the alarm temperature detection step S32, the alarm temperature detection unit7detects a temperature distribution in a relatively wide range including the above-described detection point P which is set on the convex surface Sn of the turbine blade1. After the alarm temperature detection step S32, the second determination step S42is performed. In the second determination step S42, it is determined whether or not a portion of which the temperature exceeds a predetermined value (alarm threshold value) is present within a detection target range obtained in the alarm temperature detection step S32.

In a case where it is determined in the second determination step S42that the detection target range includes a portion where the predetermined value is exceeded (step S42: Yes), the alarm step S52, which is a subsequent step, is performed. In the alarm step S52, by means of sound, light, or the like, an administrator is notified or warned that the temperature is on the rise. It is also possible to adopt a configuration in which an electrical current supplied from the electrical current controller85is cut off in the alarm step S52. After the alarm step S52, the processing returns to the quenching step S2described above. Accordingly, quenching is performed again for a predetermined time or a predetermined distance.

On the other hand, in a case where it is determined in the second determination step S42that the detection target range does not include a portion where the predetermined value is exceeded (step S42: No), the processing returns to the above-described quenching step S2again without the alarm step S52being performed. Accordingly, quenching is performed again for a predetermined time or a predetermined distance. Such a cycle is repeated over the entire leading edge EL.

(Action and Effect)

According to the above-described configuration, the turbine blade1is subjected to quenching processing in a state where the leading edge EL of the turbine blade1is sandwiched by the U-shaped portion31of the induction heating coil3. Accordingly, in comparison with a case where a step of locally performing quenching processing is repeated, quenching can be finished more uniformly. Furthermore, the temperature detection unit6is configured to detect the temperature of the vicinity of the induction heating coil3in a non-contact manner. As a result, the influence of the temperature detection unit6itself on the detection value can be suppressed in comparison with a case where the temperature is detected by, for example, a contact type device. That is, it is possible to achieve an increase in detection accuracy.

In addition, the control device90controls the magnitude of a high-frequency electrical current supplied to the induction heating coil3based on the detection value of the temperature detection unit6. Therefore, it is possible to reduce a probability that the heating temperature of the induction heating coil3becomes excessively high.

According to the above-described configuration, the temperature detection unit6detects the temperature of a portion (detection point P) of the leading edge EL that is on a convex side (convex surface Sn side) of the turbine blade1and that is surrounded by the U-shaped portion31and the linear portion32. Accordingly, the temperature of a portion where the heating temperature of the induction heating coil3is highest can be obtained as the detection value. The control device90controls the amount of electrical current supplied to the induction heating coil3such that the detection value does not exceed a predetermined value. Therefore, it is possible to further reduce a probability that the heating temperature of the induction heating coil3becomes excessively high.

According to the above-described configuration, in a case where the turbine blade1has a three-dimensionally twisted shape, the turbine blade1can be rotated around the rotation axis Ax extending in the blade height direction Dh by the rotating mechanism5. Accordingly, it is possible to maintain a relative distance between the induction heating coil3and the leading edge EL without moving the induction heating coil3itself. Therefore, the heating temperature can be controlled with a higher accuracy.

According to the above-described configuration, since the temperature detection unit6is an optical fiber type radiation temperature sensor, the temperature detection unit6is less likely to be influenced by an induced electrical current generated by the induction heating coil3. Accordingly, temperature detection of the temperature detection unit6can be realized with an even higher accuracy.

According to the above-described configuration, the alarm temperature detection unit7is provided in addition to the temperature detection unit6. The alarm temperature detection unit7detects a temperature distribution in a wider range than the temperature detection unit6. The control device90issues an alarm in a case where the temperature distribution includes a value higher than the alarm threshold value. That is, in the above-described configuration, in a case where the heating temperature of the induction heating coil3becomes excessively high even in just a part, a warning can be issued to the administrator not to perform further heating. Accordingly, quenching processing can be performed on the turbine blade more uniformly and more accurately.

According to the above-described configuration, the black coating film Lb is formed on the surface of the turbine blade1. The temperature detection unit6detects the temperature of a surface of the black coating film Lb. Accordingly, in comparison with a case where, for example, a metallic material is exposed at the surface of the turbine blade1, a variation in emissivity of heat from the surface can be suppressed. Accordingly, temperature detection can be performed with an even higher accuracy.

According to the above-described configuration, a region surrounded by the linear portion32and the U-shaped portion31is formed on the surface of the turbine blade1. Accordingly, a high-temperature state is maintained in the surrounded region. Accordingly, quenching processing can be performed efficiently and uniformly.

Here, in the case of the turbine blade1, erosion is likely to occur particularly at one-third of a portion from the leading edge EL in a chord direction (direction connecting leading edge EL and trailing edge ET). According to the above-described configuration, it is possible to actively perform quenching processing on such a portion. Accordingly, the turbine blade1having an even higher durability can be obtained.

Other Embodiments

Hereinabove, the embodiment of the present disclosure has been described in detail with reference to the drawings. However, a specific configuration is not limited to the embodiment, and design changes can be made without departing from the gist of the present disclosure. Note that, in the above-described embodiment, a configuration in which the induction heating coil3and the temperature detection unit6are moved in the blade height direction Dh by the moving mechanism4has been described. However, it is also possible to adopt a configuration in which the stand2is moved in the blade height direction Dh by the moving mechanism4. In this case, the configuration of the apparatus can be simplified.

<Appendix>

The high-frequency hardening apparatus described in each embodiment is understood as follows, for example.

(1) The high-frequency hardening apparatus100according to a first aspect includes the induction heating coil3that includes the U-shaped portion31that sandwiches the leading edge EL of the turbine blade1, the pair of linear portions32that sandwiches the turbine blade1, and the connecting portion33that connects the U-shaped portion31and the linear portions32to each other on a convex side and a concave side of the turbine blade1, the temperature detection unit6that detects the temperature of the leading edge EL of the turbine blade1in the vicinity of the induction heating coil3in a non-contact manner, the moving mechanism4that moves the turbine blade1and the induction heating coil3relative to each other in the blade height direction Dh of the turbine blade1, the electrical current supply unit8that supplies a high-frequency electrical current to the induction heating coil3, and the control device90that includes the electrical current controller85, the electrical current controller85controlling the magnitude of the high-frequency electrical current from the electrical current supply unit8based on a detection value of the temperature detection unit6such that the detection value does not exceed a predetermined temperature.

According to the above-described configuration, the turbine blade1is subjected to quenching processing in a state where the leading edge of the turbine blade1is sandwiched by the U-shaped portion31of the induction heating coil3. Accordingly, in comparison with a case where local quenching processing is repeated, quenching can be finished more uniformly.

Furthermore, the temperature detection unit6is configured to detect the temperature of the vicinity of the induction heating coil3in a non-contact manner. As a result, the influence of the temperature detection unit6itself on the detection value can be suppressed in comparison with a case where the temperature is detected by, for example, a contact type device. That is, it is possible to achieve an increase in detection accuracy.

In addition, the control device90controls the magnitude of a high-frequency electrical current supplied to the induction heating coil3based on the detection value of the temperature detection unit6. Therefore, it is possible to reduce a probability that the heating temperature of the induction heating coil3becomes excessively high.

(2) In the high-frequency hardening apparatus100according to a second aspect, the temperature detection unit6detects the temperature of a portion of the leading edge EL that is on the convex side of the turbine blade1and that is surrounded by the U-shaped portion31and the linear portion32.

According to the above-described configuration, the temperature of a portion where the heating temperature of the induction heating coil3is highest can be obtained as the detection value. The control device90controls the amount of electrical current supplied to the induction heating coil3such that the detection value does not exceed a predetermined value. Therefore, it is possible to further reduce a probability that the heating temperature of the induction heating coil3becomes excessively high.

(3) In the high-frequency hardening apparatus100according to a third aspect, the turbine blade1is twisted in a circumferential direction around the blade height direction Dh from one side toward the other side in the blade height direction Dh, and the high-frequency hardening apparatus100further includes the rotating mechanism5that maintains a relative distance between the leading edge EL and the induction heating coil3by rotating the turbine blade1around the rotation axis Ax extending in the blade height direction Dh as the turbine blade1and the induction heating coil3move relative to each other in the blade height direction Dh.

According to the above-described configuration, in a case where the turbine blade1has a three-dimensionally twisted shape, the turbine blade1can be rotated around the rotation axis Ax extending in the blade height direction Dh by the rotating mechanism5. Accordingly, it is possible to maintain a relative distance between the induction heating coil3and the leading edge EL without moving the induction heating coil3itself. Therefore, the heating temperature can be controlled with a higher accuracy.

(4) In the high-frequency hardening apparatus100according to a fourth aspect, the temperature detection unit6is an optical fiber type radiation temperature sensor.

According to the above-described configuration, since the temperature detection unit6is an optical fiber type radiation temperature sensor, the temperature detection unit6is less likely to be influenced by an induced electrical current generated by the induction heating coil3. Accordingly, temperature detection of the temperature detection unit6can be realized with an even higher accuracy.

(5) The high-frequency hardening apparatus100according to a fifth aspect further includes the alarm temperature detection unit7that is provided separately from the temperature detection unit6and that detects a temperature distribution in a range on the leading edge EL that is wider than a temperature detection target range of the temperature detection unit6, and the electrical current controller85is configured to issue an alarm in a case where the temperature distribution detected by the alarm temperature detection unit7includes a value higher than a predetermined alarm threshold value.

According to the above-described configuration, the alarm temperature detection unit7is provided in addition to the temperature detection unit6. The alarm temperature detection unit7detects a temperature distribution in a wider range than the temperature detection unit6. The control device90issues an alarm in a case where the temperature distribution includes a value higher than the alarm threshold value. That is, in the above-described configuration, in a case where the heating temperature of the induction heating coil3becomes excessively high even in just a part, a warning can be issued to the administrator not to perform further heating. Accordingly, quenching processing can be performed on the turbine blade more uniformly and more accurately.

(6) In the high-frequency hardening apparatus100according to a sixth aspect, the turbine blade1includes the black coating film Lb that is formed at least on the leading edge EL and that is formed of a black paint, and the temperature detection unit6is configured to detect the temperature of a surface of the black coating film Lb.

According to the above-described configuration, the black coating film Lb is formed on the surface of the turbine blade. The temperature detection unit6detects the temperature of a surface of the black coating film Lb. Accordingly, in comparison with a case where, for example, a metallic material is exposed at the surface of the turbine blade1, a variation in emissivity of heat from the surface can be suppressed. Accordingly, temperature detection can be performed with an even higher accuracy.

(7) In the high-frequency hardening apparatus100according to a seventh aspect, the linear portion32extends along a surface of the turbine blade1to be parallel with the U-shaped portion31.

According to the above-described configuration, a region surrounded by the linear portion32and the U-shaped portion31is formed on the surface of the turbine blade1. Accordingly, a high-temperature state is maintained in the surrounded region. Accordingly, quenching processing can be performed efficiently and uniformly.

(8) In the high-frequency hardening apparatus100according to an eighth aspect, the U-shaped portion31is configured to sandwich the turbine blade1by one-third of a distance from the leading edge EL in a chord direction of the turbine blade1.

In the case of the turbine blade1, erosion is likely to occur particularly at one-third of a portion from the leading edge EL in a chord direction. According to the above-described configuration, it is possible to actively perform quenching processing on such a portion. Accordingly, the turbine blade1having an even higher durability can be obtained.

REFERENCE SIGNS LIST

100: high-frequency hardening apparatus1: turbine blade11: blade body11T: tip12: blade root12S: serration2: stand21: stand body22: fixation member3: induction heating coil31: U-shaped portion32: linear portion33: connecting portion4: moving mechanism41: rail42: first moving portion43: second moving portion5: rotating mechanism6: temperature detection unit61: supporting part7: alarm temperature detection unit8: electrical current supply unit90: control device81: controller82: storage unit83: determination unit84: movement controller85: electrical current controller91: CPU92: ROM93: RAM94: HDD95: I/OAx: rotation axisC: iron coreDh: blade height directionEL: leading edgeET: trailing edgeLb: black coating filmP: detection pointSn: convex surfaceSp: concave surface