JPH08160035A - Method and apparatus for controlling life of high temperature part of gas turbine - Google Patents

Abstract

PURPOSE: To ensure the reliability to keep operation by determining the load condition of heat stress analysis on the basis of damage distribution at the time of periodic inspection and executing heat cut-off coating on the basis of the result of proper residual life evaluation to control the life of the high temp. part of a gas turbine. CONSTITUTION: Temp. analysis and heat stress analysis by a finite-element method are performed with respect to the high temp. part of a gas turbine by setting a planning condition such as a shape dimension or the like and operation history such as the number of times of start and stop or operation temp. as fundamental boundary conditions. The analytical results are converted into damage distribution on the basis of the stress distribution of the analytical results and the corresponding material strength data to evaluate the life of the high temp. part. A region large in damage cumulation is made clear from the damage analysis of the number of surface cracks and the length and region of the surface cracks and effective life control can be performed by setting a region to be monitored. The image of the surface damage of a determined region is magnified by a video camera to be subjected to image processing by a computer to evaluate the whole life. When it is diagnosed that there is no residual life, the replacement of the part or life extending treatment such as heat cut-off coating is performed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a preventive maintenance technique for power generation equipment using a gas turbine, and more particularly to a life management method and apparatus for high temperature parts such as gas turbine moving vanes and combustors operating at high temperature for a long time. Get involved.

[0002]

2. Description of the Related Art Embrittlement, fatigue damage, and creep damage of main components of high-temperature equipment progress with long-term use. Diagnosis of these aging deterioration and prediction of material damage are the most important issues in considering the strength reliability of high temperature parts and in evaluating the remaining life of high temperature parts. As an example of deterioration diagnosis technology for this, many proposals have been made in the past regarding steam turbines, and for example, in low alloy heat-resistant steel, an index of material embrittlement is obtained from a replica method based on an intergranular corrosion method or an electric polarization method. Fracture transition temperature (F
It has been proposed to estimate the ATT) and evaluate the maximum allowable defect size of the aged member (deterioration diagnosis method for turbine member JP-A-1-110259, deterioration determination method for low alloy steel JP-A-62). -222155).

Regarding a gas turbine, a method has been proposed in which deterioration of the surface layer of a high temperature component is detected from changes in physical constants to predict the life (gas turbine Japanese Patent Laid-Open No. 5-26054).
issue).

[0004]

In the above conventional method,
Degradation can be evaluated non-destructively for low alloy steels, but degradation cannot be evaluated for high temperature superalloy parts used in gas tabines. Further, it is difficult to propose maintenance management and a longer life of the gas turbine only by predicting the life of the gas turbine member from the physical constants of the materials, and therefore it is difficult to perform proper maintenance, replacement or replacement at the time of regular inspection. By the way, gas turbines are easy to start up, have a short construction period, and have high thermal efficiency in a combined plant that combines high-temperature exhaust gas with a steam turbine. It is actively moving forward. Gas turbines, which are the main equipment of this power generation facility, are required to have high efficiency, and the turbine inlet gas temperature is rapidly increasing year by year. As a result, the load conditions on the combustor and turbine blades, which are the main high-temperature equipment, have become more severe than ever before. However, these high temperature parts are required to have high reliability for stable equipment operation. By the way, the Ni-based and Co-based superalloys, which are constituent materials of the gas turbine, have high temperature and high strength, but there is a possibility that material deterioration and accumulation of damage may occur due to high temperature long time load and repeated start and stop. Therefore, in order to operate the gas turbine with high reliability, it is necessary to accurately grasp the deterioration and damage of these high-temperature members at the time of regular inspection, and perform maintenance management such as inspection time and repair and parts replacement based on these results. There is. High temperature corrosion and fatigue are extremely important among the deterioration damage of gas turbine high temperature parts. Since many gas turbines have excellent start-up characteristics, they are frequently started and stopped according to power demand. As a result, turbine blades and vanes are subject to severe thermal fatigue damage. By the way, the moving blade is generally coated, and the crack initiation mechanism in this coating blade is considered as follows. First, the deterioration of the coating layer, that is, the layer structure is 2
It changes into phases (β and γ '), becomes brittle, and spalling occurs.
Next, a crack is generated in the coating, and oxidation or sulfide corrosion extends to the interdiffusion layer and the base material, and the crack grows in the corrosion-affected portion. It has been confirmed by microscopic observation that crack growth is significantly affected by the environment. However, for coated blades commonly used in gas turbines, there is currently no effective diagnostic method for this degradation damage. The conventional electrochemical method has a problem in that it is difficult to set the environmental temperature and the corrosion time due to the influence of electrical noise at the plant site, which may cause a large error in the evaluation of the deterioration degree. Furthermore, the operating conditions of the plant change, and the frequency of starting and stopping the plant increases accordingly, making it difficult to predict the remaining life based on the conventional trend curve based on operation data. Under these circumstances, there is a strong demand for the development of a method for highly accurately diagnosing deterioration under operating conditions of gas turbine power plant equipment, a method for maintenance management, and an apparatus therefor. The object of the present invention is the segregation of the coating interface in high-temperature parts that is a problem in gas turbines for power plants, and high-temperature parts in which surface microcracks are generated by repeated loading at high temperatures, for example, in a stationary blade, It is an object of the present invention to provide a gas turbine life management method and apparatus for more rational maintenance management.

[0005]

According to the present invention, a heat transfer coefficient, which is a load condition of thermal stress analysis, is determined by paying attention to a crack which is a damage distribution which is data obtained by a periodic inspection, and an appropriate residual life evaluation is performed. Is performed, and as a result, the life control of the high temperature parts of the gas turbine is performed by performing thermal barrier coating for replacing the thermal stress, which is a life extension process, and part replacement.

[0006]

In the case of a high-temperature component of a gas turbine, for example, a stationary blade, small cracks are often distributed and grow on the surface due to thermal fatigue during use. These are detected and recorded at each regular inspection, so that the damage development can be grasped in a tendency. The area of the observation record of these records is determined by the part of the high temperature component, and the deterioration state of the high temperature component is quantitatively evaluated by representing the damage state in that region by the maximum crack length. On the other hand, in the residual life evaluation of parts based on thermal stress analysis by the finite element method using design conditions and operation history data, the heat transfer coefficient is adjusted so that the stress distribution corresponds to the damage distribution based on the crack length. The accuracy of evaluation can be improved by repeatedly performing boundary conditions such as the above and performing thermal stress analysis so as to match the damage distribution and determining the stress distribution. In addition, when there is not a sufficient remaining life, it is known that damage due to thermal fatigue can effectively extend the life by decreasing the operating temperature as a treatment for extending the life of parts. Apply a thermal barrier coating that lowers the temperature of the member. As a result, it is possible to extend the service life of parts by partial repair.

[0007]

【Example】

(Embodiment 1) One embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a procedure for managing the life of the high temperature gas turbine component. For gas turbine high-temperature parts, for example, a stationary blade as shown in Fig. 2, temperature analysis and thermal stress analysis are performed by the finite element method with design conditions such as geometry and operating history such as the number of start and stop times and operating temperature as basic boundary conditions. I do. Based on the stress distribution of the stationary blade as a result of this analysis, the corresponding material strength data is converted into a damage distribution for evaluation. In this case, the damage distribution data as the regular inspection data of the corresponding stationary blade, for example, the observation data of the surface crack as shown in FIG. In the area with a high value, repeated analysis is performed while changing the boundary conditions such as the heat transfer coefficient so that the crack density increases. The residual life is analytically evaluated from the stress distribution, which is the result when the observation data of the crack distribution agrees with the analysis result. Figure 3 shows the distribution of crack initiation and the equal stress distribution obtained by stress analysis. Here, the operation history of the gas turbine differs depending on each power generation facility or each device because of its excellent starting characteristics. Therefore, it is possible to grasp the operating history that is significantly different depending on the equipment, that is, to evaluate the thermal fatigue damage assuming that the stress obtained by the stress analysis as described above from the number of times of start and stop, operating time, number of trips, exhaust gas temperature history, etc. is repeated. The remaining life of the device is calculated. On the other hand, in the case of the stationary blade as shown in FIG. 2, the damage distribution is analyzed by considering the site where one entire stationary blade is divided into, for example, 16 as shown in FIG. The relationship between the number of observed cracks and each part is shown in FIG. The observed driving time is about 6
Three times from 000 hours to about 20,000 hours. From this result, the outer wall parts of Nos. 1 and 2 and No. 10
It was found that the number of cracks was large in the pressure side area of the trailing edge part of, and the difference in damage between the outer wall and the inner wall was remarkable. FIG. 6 shows the relationship between the total length, which is the sum of the lengths of the cracks that occurred, and the site. This relationship is shown in Figure 5.
The tendency is almost the same as the result of crack number. That is, it can be seen that the cracks greatly grow in the pressure side regions of the outer wall portions of Nos. 1 and 2 and the trailing edge portion of No. 10. From the damage analysis of FIGS. 5 and 6, the region where the damage accumulation of the gas turbine stationary blade is large becomes clear, and it becomes clear which region of the stationary blade should be monitored to effectively manage the life. Further, FIG. 7 shows the result of organizing the relationship between the number of start-stops and the total length of cracks, which are the main items of the operation history, focusing on the part 10, that is, the trailing edge portion on the outer wall side.

FIG. 8 shows the relationship between the number of times of starting and stopping and the maximum crack length in the region of the region 10. From these results, the number of starting and stopping and the maximum crack length are correspondingly and exponentially increasing. From these results, the maximum crack length is a _max ,
If the number of start-stops is N, the following equation is obtained.

N = C.log (a _max ) ... (1) The future maximum crack length a _max can be predicted by the above equation, and the remaining life of the stationary blade can be evaluated. In this case, as shown in FIG. 10, an image of the surface damage is enlarged and input by a video camera or the like to the determined part, and this is image-processed by a computer and statistically processed to obtain the maximum crack length, and the remaining life is evaluated. . Furthermore, by recording the image and capturing the image of the same area at the next regular inspection, the crack image of the previous image is output with a high density, and the crack image of this time is output thinly to make it easy to check the crack length. You can recognize the growth.

As described above, comprehensive residual life diagnosis of high-temperature parts can be performed by analytical and nondestructive residual life evaluation by crack length detection. In this case, if it is diagnosed that there is a remaining life that can maintain sufficient reliability by the next periodic inspection, the operation is continued, and if not, the life extension processing of the relevant part is performed. The life extension treatment includes replacement and repair of relevant parts, and then thermal barrier coating. It has been conventionally used for parts replacement and repair. Since thermal fatigue is the main mechanism for cracks in stator vanes, the life of thermal barrier coating is extended by lowering the temperature applied to the material of the parts, which extends the life of the thermal barrier coating. To be adopted as. If this treatment is applied, it will be returned to the turbine and used again.

By the way, the remaining service life diagnosis is required for the next regular inspection of the blade having the thermal barrier coating. This would require new diagnostic techniques for thermal barrier coated blades. This will be described in detail below.

The thermal barrier coating is formed by coating a ceramic mixture of zirconia oxide and yttria oxide on the alloy coating. By the way, the crack initiation mechanism in the coating blade is considered as follows.
First, the deterioration of the coating layer, that is, the layer structure has two phases (β
And γ ′) and becomes brittle, causing microdelamination at the interface.
Next, a crack is generated in the coating, and oxidation or sulfide corrosion extends to the interdiffusion layer and the base material, and the crack grows in the corrosion-affected portion. Therefore, it is indispensable to diagnose the change at the interface analytically or nondestructively and by destructive evaluation in the deterioration process. As an example of the present invention, the analysis and evaluation stage is performed based on this deterioration mechanism. That is, the evaluation procedure will be described using the analytical explanatory diagram of the deterioration process of the intermediate layer coating of the ceramics and the base material shown in FIG. This figure shows that a concentration gradient of the composition elements Ni and Al in the coating layer and the base material occurs. As shown in the diagram (b), due to this concentration gradient, each element undergoes diffusive migration in a high-temperature operating state. As a result, mass transfer and vacancy transfer occur as shown in the figure, and precipitates and voids are generated at the coating interface as shown in (c). This process is known as Kirkendall diffusion focusing on Ni and Al. From this equation, the void density Cv which is a problem for deterioration
Can be evaluated by the following formula. Cv = -1 / (NsF) Jv / x (2) Here, Ns is a hole source density, F is a constant depending on temperature,
Jv is the flux of the holes. An appropriate constant Cc is determined from the correspondence with the destructive test result described later by the above formula (2),
Set the standard value for analysis evaluation. That is, Cv <Cc2.

According to the deterioration mechanism of the coating blade shown in FIG. 11, since the voids develop in the interface layer and the material rigidity and physical properties change, the deterioration can be diagnosed non-destructively using ultrasonic waves.

FIG. 12 shows a micro punch (small SP punch) test method used in a destructive test.

FIG. 3A shows a jig used for the small punch test. The feature of this method is that the test piece is 10 mm square and is 0.
It is possible to use a minute one of 5 mm. Since the test piece can be prepared by cutting it directly from the actual coating blade, it is possible to diagnose the deterioration degree of the actual member with high accuracy.
The diagram (b) shows the definition of SP energy, which is a parameter when diagnosing material deterioration in the above-described micro punch test. As shown in the figure, the degree of deterioration can be evaluated by the magnitude of SP energy on the curve of load and displacement obtained by the test piece jig shown in FIG. In the present invention, a test piece is cut out from a high temperature portion which is considered to be most deteriorated from the portion of the stationary blade, an SP test is carried out, the comparison is made, and the relationship between the SP energy and the deterioration degree which is separately obtained in the standard test piece is used. Performs wing deterioration diagnosis. If the coating is located on the tensile side and the deterioration progresses as shown in FIG. (B), the test load appears with good sensitivity. By determining the SP energy from this load lowering position, it is possible to accurately diagnose the deterioration of the coating layer. Further, in this test, if an AE sensor is attached to a test piece and an experiment is conducted, the crack generation in the coating portion can be detected with high sensitivity.

[0016]

According to the present invention, the load condition of the thermal stress analysis is determined based on the damage distribution which is the data obtained in the regular inspection, and the appropriate remaining life is evaluated. By performing the thermal barrier coating to manage the life of the high temperature parts of the gas turbine, the reliability of the gas turbine can be secured and the operation can be maintained.

[Brief description of drawings]

FIG. 1 is a flowchart showing an outline of an evaluation procedure according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating a damaged state of a gas turbine stationary blade and an example of stress analysis results corresponding to the damaged state, which illustrates an example of the present invention.

FIG. 3 is a distribution diagram of stress generated in a gas turbine stationary blade.

FIG. 4 is a diagram showing a target region used when analyzing a damage state adopted in the non-destructive method according to the present invention.

FIG. 5 is a diagram showing a result of analyzing damage.

FIG. 6 is a diagram showing a result of analyzing damage.

FIG. 7 is a diagram showing a result of analyzing damage.

FIG. 8 is a diagram showing a result of analyzing damage.

FIG. 9 is a diagram illustrating an example in which a portion is determined from a real blade according to the present invention for damage evaluation, enlarged, and image processed.

FIG. 10 is a diagram showing a deteriorated state of a thermal barrier coating portion.

FIG. 11 is a diagram showing a deteriorated state of a thermal barrier coating portion.

FIG. 12 is a diagram illustrating deterioration diagnosis by a small punch test.

Claims (10)

[Claims] 1. A method and apparatus for managing the life of a gas turbine high temperature component, wherein when analyzing the temperature and stress of the high temperature component from the design conditions and operating history of the gas turbine high temperature component to evaluate the remaining life, The stress condition is determined by determining the load condition which is the thermal condition in the analysis so as to correspond to the damage distribution condition of the high temperature parts recorded during the periodic inspection, and the damage condition of the corresponding high temperature parts at the next scheduled regular inspection. Is calculated based on the number of times of start and stop and the operating time as the stress obtained in the above analysis is repeated to diagnose the remaining life of high temperature parts. After diagnosing the service life, if the prescribed amount of damage is not reached during the operation period until the next regular inspection, proceed with the operation as it is, and if it is more than the prescribed damage, shorten the regular inspection period or repair the relevant parts. Or parts replacement Life is extended and operation is advanced.For high temperature parts that have been extended in life, representative parts will be extracted at the next regular inspection, and test pieces will be collected from the representative parts and a destructive test will be performed to determine the remaining life. A gas turbine characterized by deciding whether or not to operate between the next regular inspections as a diagnosis, and systematically performing repairs or parts replacement as a regular inspection period or life extension processing based on the remaining life diagnosis. Method and apparatus for managing the life of high temperature parts. 2. The damage distribution state of the high temperature component recorded at the time of the periodic inspection is based on the distribution data of minute crack lengths generated on the material surface of the component, and the portion having a large crack density or the portion having a large crack length. Indicates that a large stress is acting, the thermal conditions such as the heat transfer coefficient, which is the load condition of the temperature stress analysis, are determined so that the distribution of the stress size is matched in proportion to the crack length distribution. Based on the operation plan, the damage is defined as the micro crack density D (a) or the maximum crack length Amax, and the damage development is taken as the operating time t of the operation plan and the number of start / stop times N.
Relational expression D (a) = f (N, t) or Amax = f (N, t)
A method and apparatus for managing the life of a gas turbine high temperature component, characterized by predicting from t) and evaluating the remaining life analytically. 3. The extension of service life of the gas turbine high temperature component according to claim 1 is based on a future operation plan, and the damage development is defined as a micro crack density or a maximum crack length. Predicted from the relationship of, and analytically evaluate the remaining life, and if there is no predetermined remaining life, as a life extension treatment, based on the data of minute crack density or maximum crack length, A method and apparatus for managing the life of a gas turbine high temperature component, characterized by extending the life of a gas turbine high temperature component by applying a thermal barrier coating to make the temperature distribution uniform and relieve thermal stress. 4. A method and apparatus for managing the life of a high temperature component of a gas turbine, wherein the non-destructive residual life diagnosis of the high temperature component is the damage data in each periodical inspection, such as the minute crack density or the maximum crack length of the member surface. Based on the relationship with the operation history, the history of damage development is statistically approximated and the approximate expression is used to predict the damage of the next periodic inspection and diagnose the remaining life, and the life management method of the gas turbine high temperature component and That device. 5. A method and apparatus for managing the life of a high temperature component of a gas turbine, wherein the non-destructive residual life diagnosis of the high temperature component is the damage data in each periodic inspection, which is the microcrack density or the maximum crack length of the member surface. To determine a representative area with a large damage in the high temperature member in relation to the operation history, collect data in only the representative area as a monitoring unit for damage of the high temperature part, and target only the representative area when damage is detected A method and apparatus for managing the life of a high-temperature component of a gas turbine, characterized in that the history of damage development is statistically approximated to a regression, and the approximation formula predicts the damage at the next periodic inspection to diagnose the remaining life. 6. Non-destructive residual life diagnosis of high temperature parts is based on the relationship between the maximum crack length of the member surface and the operation history, which is the damage data in each periodic inspection, and the representative region in the high temperature member where the crack size is large. The life management method of the gas turbine high temperature component for statistically approximating the history of crack growth by targeting the representative region at the time of damage detection and predicting the damage of the next periodic inspection and diagnosing the remaining life by the approximate expression In the device, the representative area is input and recorded by a video camera or the like, and the maximum crack length in the representative area recorded last time is comparatively calculated to predict damage at the next periodic inspection and diagnose the remaining life. And method for managing life of high temperature parts of gas turbine. 7. Non-destructive residual life diagnosis of high-temperature parts is based on the relationship between the maximum crack length of the member surface, which is the damage data in each periodical inspection, and the operation history, and the representative region in the high-temperature member where the crack size is large. A method for managing the life of the gas turbine high temperature component, which statistically approximates the history of damage development by targeting the representative region at the time of damage detection, and predicts the damage of the next periodic inspection and diagnoses the remaining life by the approximate expression. In that device, the representative area is input and recorded by a video camera or the like, and the maximum crack length is compared and calculated on the entire area of the representative area recorded last time and the image, and the relationship between the maximum crack length and the depth is obtained in advance. A method and apparatus for managing the life of a high temperature component of a gas turbine, which predicts the damage of the next periodical inspection and diagnoses the remaining life when a predetermined amount of cracks grow with respect to the wall thickness. 8. Based on the future operation plan of claim 2, damage development is predicted from the relationship between the operating time and the number of start and stop times of the operation plan with damage as the maximum crack length, and the remaining life is analytically evaluated. In the life management method and equipment for gas turbine high temperature parts, where a thermal barrier coating is applied to a part where damage progresses greatly based on the maximum crack length data when there is no prescribed remaining life, A method and apparatus for managing the life of a high temperature component of a gas turbine, characterized in that the remaining life of the thermal coating portion is diagnosed based on the detection of the peeled area using ultrasonic waves. 9. A method for controlling the life of a high temperature component of a gas turbine, and a thermal barrier coating as a measure for extending the life of the high temperature component in the apparatus thereof, Ni, Co, C on the surface of the base material of the high temperature component
An alloy coating containing r, Al, Y, etc. as a main component is applied by low-pressure plasma spraying, and the surface of the alloy coating is further coated with aluminum. Then, the surface is exposed to the atmosphere and oxidized, and the oxidized aluminum coating surface is coated. A method and apparatus for managing the life of a high temperature gas turbine component, characterized by applying a thermal barrier coating. 10. A method of managing the life of a high temperature component of a gas turbine and a thermal barrier coating as a measure for extending the life of the high temperature component in the apparatus, wherein Ni, Co,
A coating of an alloy containing Cr, Al, Y or the like as a main component is applied by low pressure plasma spraying or the like, and the surface of the alloy coating is further coated with aluminum, and then the surface is exposed to the atmosphere to be oxidized, and the oxidized aluminum coating surface A method and apparatus for managing the life of a high temperature component of a gas turbine, characterized by applying a thermal barrier coating after grinding and smoothing.