JPH0571303A - Ceramic heat-resistant wall structure - Google Patents

Abstract

PURPOSE:To provide a ceramic heat-resistant wall structure which can reduce the thermal shock stress in the ceramic material part, and can maintain the ceramic material part at the optimum temperature capable of reduction, etc., of oxidation or damage at stationary operation. CONSTITUTION:In an object wherein the metallic core bar 1 to be cooled by air is surrounded by a ceramic sleeve 3, cooling air is let flow to the space 6 between the metallic core bar 1 and the ceramic sleeve 3 so as to cool the ceramic sleeve 3 from inside.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-resistant wall structure of a high temperature component exposed to a high temperature gas such as a combustor, a moving blade or a stationary blade of a gas turbine, and particularly to a ceramic material for a portion directly exposed to the high temperature gas. The present invention relates to a ceramics heat-resistant wall structure which is constructed by using a metal material for each part which is not directly exposed to high temperature gas.

[0002]

2. Description of the Related Art Ceramic materials have heat resistance, corrosion resistance,
It is excellent in abrasion resistance, and various applications as high value-added mechanical structural parts are considered by making use of these characteristics. In particular, in the gas turbine machine, the maximum temperature (turbine inlet gas temperature) is 1100 to 1300 even under the current circumstances.
Reaches ℃. It is expected that the maximum temperature will be higher than that of the present as the performance of gas turbines will be improved in the future, and the adoption of ceramic materials with excellent heat resistance in high-temperature parts such as rotor blades, stator blades, and combustors. Being tried.

For example, as an example in which a ceramic material is used for the inner wall surface of a liner or a transition piece of a combustor, Japanese Patent Laid-Open No. 59-15727 and Japanese Patent Publication No. 59-17 are available.
Examples described in Japanese Patent Laid-Open No. 326 and Japanese Patent Laid-Open No. 63-207920 are known. Further, as an example of using a ceramic material for a moving blade, a hybrid ceramic moving blade in which a ceramic sleeve and a metal core are combined is disclosed in Japanese Patent Laid-Open No. 59-59.
The ones disclosed in JP-A-119001 and JP-A-59-160001 are known.

All of the above-described examples of application utilize the excellent heat resistance of the ceramic material. The portion directly exposed to the high temperature gas is made of the ceramic material, and the low temperature portion not directly exposed to the high temperature gas is The heat resistant wall structure is made of a metal material. Figure 9
FIG. 4 is a vertical cross-sectional view of a typical example of a conventional hybrid ceramic rotor blade. In this figure, a metal sleeve 1 is covered with a ceramic sleeve 3 with a heat insulating material layer 2 interposed therebetween. The metal core 1 is provided with a cooling air passage 4,
Exposed part of the metal core 1 and the ceramic sleeve 3
A heat resistant coating 5 is applied to a portion facing the. The cooling air passages 4 are distributed in the cross section of the metal core 1 and a plurality of longitudinal portions 4a are provided in the longitudinal direction of the moving blade.
And a lateral portion 4b which is in communication with these portions and which is open in the turbine casing at the side edge of the moving blade and is located near the tip of the moving blade.

In the conventional hybrid ceramic blade having the above structure, the metal core 1 is cooled by the cooling air flowing in the cooling air passage 4. Then, metal core 1
Since the ceramic sleeve 3 and the ceramic sleeve 3 are separated from each other by the heat insulating material layer 2, there is little thermal influence on the metal cored bar 1 of the ceramic sleeve 3 which has become high temperature due to direct contact with the high temperature gas, and the metal cored bar 1 is It is kept cool by a small flow of cooling air. On the other hand, the ceramic sleeve 3 has a temperature as high as the gas temperature due to contact with the high temperature gas, but since it is in contact with the metal core 1 being cooled through the heat insulating material layer 2, the amount of heat taken away is small. The distribution is uniform and the generation of thermal stress is suppressed.

In the hybrid type ceramic moving blade illustrated above, the heat insulating material layer 2 is interposed between the metal core metal 1 and the ceramic sleeve 3 to form the metal core metal 1
It is possible to reduce the flow rate of the air that cools, and to reduce the thermal stress generated in the ceramic sleeve 3 in a steady state.

[0007]

However, in the hybrid type ceramic moving blade having the above-mentioned structure, the ceramic sleeve has a high temperature while the advantages as described above due to the interposition of the heat insulating material layer 2 are unavoidable. .. Ceramic materials such as SiC and Si ₈ N ₄ T ₅ are
Originally, it has excellent heat resistance and corrosion resistance as compared with metallic materials, but in the ultrahigh temperature range of 1000 ° C. or higher, the above excellent characteristics are inevitably decreased with increasing temperature. ..

Further, although the thermal stress in the ceramic sleeve 3 is kept low as described above in the steady state, the thermal stress generated by the thermal shock due to the rapid cooling at the time of emergency stop (trip) cannot be ignored. Can not.
That is, the higher the temperature of the moving blade during steady operation, the greater the thermal stress during quenching, causing various problems.

The present invention has been made in view of the above circumstances. For example, the thermal shock stress in the ceramic material portion at the time of turbine trip can be reduced and the ceramic material portion can be reduced from the viewpoint of reducing oxidative damage during steady operation. It is an object of the present invention to provide a ceramics heat-resistant wall structure capable of maintaining the optimum temperature.

[0010]

The ceramic heat-resistant wall structure of the present invention comprises a metal cored bar internally cooled by cooling air, and a sleeve made of a ceramic material surrounding the metal cored bar. The space between the gold and the ceramic sleeve is filled with cooling air or a heat transfer material.

[0011]

In the ceramic heat-resistant wall structure of the present invention having the above structure, the temperature of the ceramic sleeve can be set to an optimum temperature by appropriately setting the flow rate of the cooling air for cooling the metal cored bar. The life of the heat resistant wall structure can be extended.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 in which the same parts as in FIG.
2 is a vertical sectional view of an embodiment in which the present invention is applied to a hybrid rotor blade for a gas turbine, and FIG. 2 is a sectional view taken along line II-II of FIG. In these drawings, a space 6 communicating with the turbine casing is formed between a core metal 1 and a ceramic sleeve 3 surrounding the core metal 1 in a gap 7 near the upper end of the Christmas tree portion 1a of the core metal 1, A lateral portion 4b of the cooling air passage 4 is connected to the blade tip side of the space 6.

In the embodiment having the above structure, the metal core 1 is made of a heat-resistant Ni-based superalloy, and the ceramic sleeve 3 is made of structural fine ceramics such as SiC and Si ₃ N _4. Configure.

The cooling air supplied from the turbine disk side (not shown) flows through the vertical portion 4a, the horizontal portion 4b, and the space 6 of the cooling air passage 4 as shown by an arrow C in the drawing, and flows out into the turbine casing. That is, in the above embodiment, the cooling air flows through the space 6 after cooling the core metal 1 to raise the temperature, and then flows out of the moving blades.

The ceramic sleeve 3 is heated by hot gas from its surface and cooled by cooling air flowing in the space 6 from its inner surface. FIG. 3 (A) is a diagram showing the temperature distribution during steady operation of the above embodiment, and FIG. 3 (B) is a diagram showing the temperature distribution of the conventional hybrid ceramic moving blade shown in FIG. In the moving blade of the present invention, since the space 6 through which the cooling air flows is formed between the ceramic sleeve 3 and the metal cored bar 1, the maximum temperature of the inner surface of the ceramic sleeve 3 is lower than that of the conventional one. ..

FIG. 4 is a diagram showing the oxidation resistance of various ceramic materials in comparison. In this figure, the horizontal axis represents temperature, and the vertical axis represents the amount of oxidative metal loss after 10,000 hours have elapsed (the amount of reduction of the amount of healthy material due to oxidation). Generally, ceramic materials are excellent in oxidation resistance, but 1000 ° C
At the above extremely high temperatures, even a ceramic material, its oxidation resistance decreases significantly as the temperature rises. Therefore, the maximum usable temperature of the ceramic material is determined from the viewpoint of oxidation resistance. In the above-described embodiment, the temperature at which the amount of oxidative wall loss after a lapse of 10,000 hours exceeds a certain value is set as the limit temperature, and the cooling air flow rate is set so that the maximum temperature of the ceramic sleeve 3 does not exceed it.

On the other hand, regarding the setting of the temperature of the ceramic sleeve 3, it is necessary to consider the generated thermal stress. The magnitude of the thermal stress generated during steady operation depends on the temperature difference inside the ceramic sleeve 3. In the above embodiment, the surface of the ceramic sleeve 3 is exposed to the high temperature gas and the inner surface is cooled by the cooling air. Therefore, the temperature difference in the ceramic sleeve 3 is caused by the heat insulating material layer 2 shown in FIG. It is significantly larger than conventional blades. This temperature difference increases as the cooling air flow rate increases.

Further, when the gas turbine is tripped, the cooling air continues to flow even after the flame of the combustor disappears, so that thermal shock is applied to the ceramic sleeve 3 and thereby thermal stress is generated. The thermal stress due to the thermal shock during the turbine trip is the difference ΔT between the temperature T _c of the ceramic sleeve during the steady operation and the cooling air temperature T _g during the trip.
(= T _c −T _g ), heat transfer coefficient h between the ceramic sleeve 3 and the cooling air, thermal conductivity k of the ceramic material, linear thermal expansion coefficient α of the ceramic material, Young's modulus E, specific heat C
Etc.

Considering only the temperature T _c of the ceramic sleeve 3 during steady operation, the thermal stress generated will be considered. The larger ΔT is, that is, the higher T _c is, the more the thermal shock occurs during trip. The generated thermal stress is large. FIG. 5 is a diagram showing the stress generated during thermal trip during turbine trip and the thermal stress during steady state, with the temperature during steady operation taken along the horizontal axis. However, in this case, the working fluid gas temperature during steady operation is 1550 ° C. From this figure, it is possible to suppress the thermal stress during steady operation to a low level by increasing the ceramic sleeve temperature T _c during steady operation, but on the contrary, the thermal stress due to thermal shock during turbine trip may increase. I understand. In order to actually set the optimum temperature, it is necessary to consider at what level each of the generated stresses described above is with respect to the material strength. Generally, the fracture strength characteristics of ceramic materials are
It shows a delayed fracture characteristic that decreases as the load time increases, and has the following relationship with the effective load time t _eff . σ _f = K (1 / t _eff ) ^nf (1) where K is a constant, n _f is the strength deterioration index, and t _eff is the load stress σ that changes with time t.
The effective load time equivalent to (t) is converted as follows.

Here, assuming that the effective load time per trip is t _eff and the guaranteed number of times is N _f , the fracture strength with respect to the cumulative effective load time N _f t _eff can be obtained by the equation (1). This fracture strength is σ _ftrip . For steady-state thermal stress, the strength with respect to the guaranteed operation time t (= t _eff ) is _calculated by the above equation (1), and this is calculated as σ
_fsteady .

FIG. 6 is a diagram showing the ratio of the material strength to the thermal stress during steady operation and the thermal stress during trip, that is, the safety margin, obtained by the following equations (3) and (4). Safety margin against thermal stress during steady-state operation …… σ _fsteady / σ _max …… (3) Safety margin against thermal stress during trip …… σ _ftrip / σ _max ……… (4)

Further, FIG. 6 also shows the heat resistance limit obtained from the oxidation characteristics. In the above embodiment, the optimum temperature T _C of the ceramic sleeve 3 is set so as to satisfy the following conditions. That is, T _c
Is less than the oxidation heat resistance limit, and the safety margin for thermal stress during steady-state operation or the safety margin for trip thermal stress, whichever is lower, is taken as the safety margin when the two are superposed. The temperature that maximizes the safety margin is the optimum temperature.

In the embodiment having the above construction, since the ceramic sleeve 3 exposed to the high temperature gas is cooled from the inside by the cooling air, the oxidation resistance of the ceramic material, the thermal stress generated during the steady operation, and the trip during the trip. The optimum temperature of the ceramic sleeve 3, which is determined from the three viewpoints of the thermal stress generated by the thermal shock, can be set by the heat radiation control by the cooling air flow.

7 in which the same parts as those in FIG. 1 are designated by the same reference numerals.
FIG. 6 is a vertical sectional view of a second embodiment of the present invention. In this embodiment, the lateral portion 4b of the cooling air passage 4 is opened in the turbine casing, and the vertical portion 4a of the cooling air passage and the space 6 are communicated with each other near the Christmas tree portion 1a of the metal core 1. Through holes 8, 8 are provided to allow the vertical portion 4 of the cooling air passage 4 to be provided near the tip of the metal core 1.
Through holes 9, 9 are provided for communicating between a and the turbine casing.

In this embodiment, the cooling air is discharged into the turbine casing from the vertical portion 4a through the horizontal portion 4b as indicated by arrow C _{1 in} the drawing, and the through holes 8 and 8 to the space 6 are provided. The ceramic sleeve 3 flows directly into the turbine casing through the through holes 9 and 9 and is discharged into the turbine casing, and the ceramic sleeve 3 is directly cooled by the supplied cooling air instead of the air after cooling the core metal 1. .. The setting of the optimum temperature and the like are performed in the same manner as in the embodiment shown in FIGS.
In this embodiment, since the ceramic sleeve 3 is directly cooled by the supplied cooling air, the temperature of the ceramic sleeve 3 can be lowered.

FIG. 8 in which the same parts as those in FIGS. 1 and 7 are designated by the same reference numerals is a vertical sectional view of a third embodiment of the present invention. In this embodiment, a heat transfer material layer 10 having an appropriate thermal conductivity is provided in place of the conventional heat insulation material layer 2 shown in FIG.

In this embodiment, since the ceramic sleeve 3 is in contact with the metal core 1 via the heat transfer material layer 10, it is under the influence of air cooling of the metal core 1 and the heat transfer material layer 10
The heat will be removed via. Therefore, the temperature of the ceramic sleeve can be set to the optimum value by appropriately selecting the thermal conductivity of the heat transfer material.

[0028]

As is apparent from the above, in the heat resistant wall structure of the present invention, the temperature of the ceramic sleeve can be set to the optimum temperature by adjusting and setting the flow rate of the cooling air for cooling the metal cored bar. It is possible to extend the life of the hybrid ceramic blade.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of an embodiment in which the present invention is applied to a hybrid rotor blade for a gas turbine.

FIG. 2 is a sectional view taken along line II-II in FIG.

FIG. 3A is a diagram showing a temperature distribution during steady operation of the above embodiment, and B is a diagram showing a temperature distribution of the conventional hybrid ceramic moving blade shown in FIG.

FIG. 4 is a diagram showing a comparison of oxidation resistance of various ceramic materials.

FIG. 5 is a diagram showing the stress generated by thermal shock during turbine trip and the thermal stress during steady state, with the temperature during steady operation taken on the horizontal axis.

FIG. 6 is a diagram showing the ratio of material strength to the thermal stress during steady operation and the thermal stress during trip, that is, the safety margin calculated by calculation.

FIG. 7 is a vertical sectional view of a second embodiment of the present invention.

FIG. 8 is a vertical cross-sectional view of the third embodiment of the present invention.

FIG. 9 is a vertical cross-sectional view of a typical example of a conventional hybrid ceramic moving blade.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Metal core 1a ... Christmas tree part 2 ... Insulating material layer 3 ... Ceramic sleeve 4 ... Cooling air passage 4a ... Vertical part 4b ... Horizontal part 5 ... Heat-resistant coating 6 ... Space 7 ... Void 8, 9 ... Through hole 10 ... Heat transfer material layer C, C ₁ ... Arrow

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takashi Ikeda 2-4 Suehiro-cho, Tsurumi-ku, Yokohama-shi, Kanagawa Toshiba Keihin Office

Claims (1)

[Claims] 1. A metal cored bar which is cooled from the inside by cooling air, and a sleeve made of a ceramic material which surrounds the metal cored bar, wherein a space between the metal cored bar and the ceramic sleeve is cooled with air or Ceramic heat-resistant wall structure characterized by being filled with a heat transfer material.