JPH0413531B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a gas turbine whose casing is lined with a heat insulating material.

Prior Art In gas turbines, high-temperature combustion gas flows at high speed, and the higher the gas temperature at the turbine inlet, the better the thermal efficiency, so it is desirable to increase the combustion gas temperature as much as possible. requires extremely high heat resistance. Therefore, consideration is being given to using highly heat-resistant materials such as titanium, special heat-resistant alloys, and ceramics for gas turbine components. However, these special materials are generally very expensive and are often difficult to machine and expensive to process. Therefore, if there are cost constraints, these cannot be fully adopted, and materials that can be used economically must be used, so the heat resistance temperature of the selected equipment component materials It is common to set an upper limit on the gas temperature (and therefore thermal efficiency) in the gas turbine.

Problems to be Solved by the Invention Although the casings of the combustion chamber, heat exchanger, turbine chamber, etc. in a gas turbine are simply shells, they are no different from other functional parts in that they are exposed to high-temperature, high-velocity combustion gas. do not have. Therefore, if cheap ductile cast iron is used for this part,
The surface becomes oxidized in a short period of time, and then the oxide film peels off and scatters on the high-speed gas flow, damaging heat exchangers and the like.

The casing uses a relatively large amount of metal, so it is desirable to use materials as inexpensive as possible, but by covering the inner surface of the casing with ceramic fiber insulation, the temperature can be lowered gradually below the combustion gas temperature. It is known that trying to maintain However, conventional heat insulating material-lined casings leave room for improvement in terms of the heat insulating performance and durability of the heat insulating material. That is, conventionally, the ceramic fiber insulation material layer is formed by applying a plasticized mixture of ceramic fibers and a binder to the inner surface of the casing and then firing it, but the insulation material layer formed by this method has uneven physical properties. However, there is a problem that it is easily broken due to thermal shock or vibration during gas turbine operation, and in order to avoid this problem, it is necessary to use a material with a considerably high density to ensure strength. The insulation properties could not be expected. In addition, since the wind speed resistance of the surface is not sufficient, it is necessary to cover it with a stainless steel plate or the like, and there is a problem in that the maximum gas temperature is ultimately limited by the heat resistance of the covering plate.

On the other hand, Japanese Patent Publications No. 60-51422 and No. 60-52106 describe a method for laminating ceramic materials on metal parts exposed to high temperatures, such as the inner surface of a gas turbine casing. FIG. 2 shows a cross section of an example of a metal part having a ceramic material attached by these methods, in which a laminate of a metal fiber mat 12 and a ceramic material 13 is placed on the inner surface of a metal base 11 on the mat 12 side. It is brazed (14 is a fused layer by brazing). The metal fiber mat can be elastically deformed with a small stress, so when the temperature rises, it absorbs the strain due to the difference in thermal expansion between the ceramic material and the metal base, preventing the ceramic material from breaking. prevent.
However, this direction seems to have been considered as a means of forming a ceramic layer as a durable coating on metal parts, as is clear from the fact that the ceramic material is densely formed by plasma spraying. No consideration is given to the thermal insulation properties of the ceramic material layer.

In view of the above-mentioned drawbacks of conventional gas turbine casings lined with heat insulating materials, the present invention provides good durability without the need for additional covering with metal plates and improves heat insulating properties. However, the present invention seeks to provide a gas turbine having a casing lined with an excellent insulating material.

Means for Solving the Problems The gas turbine of the present invention, which has succeeded in achieving the above object, is made by bonding ceramic fibers using borosilicate glass as a bonding material, and has a bulk density of 0.1 to 0.8.
The heat insulating material is made by applying a glaze to one side of a thin plate-like porous molded body (hereinafter referred to as a ceramic fiber-borosilicate glass molded body) of g/cm ³ and adhering a thin heat-resistant fibrous mat to the other surface. The casing is lined with a fibrous mat surface as a joint surface.

In the present invention, the ceramic fiber-borosilicate glass molded body is manufactured in a factory in advance in a form that matches the shape of the casing, but is appropriately divided so that it can be attached to the inner surface of the casing. The most preferable molded product is manufactured by the following method. That is, silicate ceramic fibers, such as aluminosilicate fibers, are first treated with mineral acid to form a porous silica layer on the surface, and then dispersed in a suspension of boron compounds such as boron nitride, boron carbide, and boron oxide. let After that, the fiber is dehydrated and molded to a moisture content of 50 to 300.
% molded product, and after drying, it is heated to 1 to 20% at 500 to 1500℃.
Bake for an hour. The resulting molded product has a structure in which fibers whose surface layer is vitrified with borosilicate while leaving a heat-resistant fiber skeleton form an aggregate with many voids, and are bonded by borosilicate glass at the fiber intertwining points. Its preferred bulk density is 0.1-0.8g/
^cm3 . If the density is higher than this, the insulation performance will be poor, and unless it is undesirably thick, it will be difficult to fully achieve the purpose of the present invention. Also, if the density is too low, even if the insulation property is good, the mechanical strength will be insufficient.

Ceramic fiber-borosilicate glass molded products with such a special structure have excellent heat resistance and are strongly fused to the ceramic fibers as a binding material, so the interfiber bond is repeatedly heated to high temperatures. It shows excellent durability even when placed inside a gas turbine under severe temperature conditions. The performance values for a typical example (bulk density 0.3) are as follows.

Bending strength: normal 54.8Kg/cm ² After heating at 1000℃ x 50 hours 54.3 〃 Compressive strength: 8.9Kg/cm ² Heat shrinkage rate: 0.0% after heating at 1000℃ x 50 hours 0.3% after heating at 1200℃ x 50 hours The glaze applied to one side of the ceramic fiber-borosilicate glass molded product is to increase the surface strength of the molded product and improve wind speed resistance, and the appropriate thickness is about 0.1 to 0.5 mm. In order to form this glaze layer, a glaze is applied to the molded body prior to firing in the firing process of manufacturing the molded body, or a glaze is applied to the fired molded body and the molded body is fired again. In the fired formed body,
It is also possible to form this by a plasma spray method. Needless to say, a glaze that exhibits sufficient durability at the normal combustion gas temperature of a gas turbine is selected, and preferred examples include:
_Examples include those based on _SiO2 - _{B2O3 -R2O (} where R is an alkali metal) and those based on _SiO2 - _{B2O3 - Al2O3} .

As the heat-resistant fibrous mat on the opposite side of the glaze layer, felt made of steel wool, wire mesh made of thin steel wire, etc. can be used. This material, like the metal fiber mat in the prior art shown and explained in FIG. It absorbs and acts to prevent the molded object from breaking. In addition, it buffers strong vibrations during gas turbine operation to prevent the ceramic fiber-borosilicate glass molded body from peeling off or cracking, and also acts as a heat insulator. Its suitable thickness is 0.5-5 mm.
This mat may be bonded before the ceramic fiber-borosilicate glass molded body is attached to the gas turbine casing, or the mat may be bonded or brazed to the casing first and then the ceramic fiber with glaze layer is bonded to the casing. - The borosilicate vitreous molded body may be integrated by bonding.
For adhesion, a heat-resistant inorganic adhesive made of alumina, colloidal silica, kaolin, etc. can be used.

When obtaining the casing lining of the present invention using the above-mentioned materials, the gaps between the molded bodies, that is, the joints, created by using a plurality of ceramic fiber-borosilicate glass molded bodies prepared according to the inner surface of the divided casing, A suitable gap is provided, and the gap is preferably filled with a filler having a buffering effect, in order to provide for the expansion of the ceramic fiber-borosilicate glass molded body due to the temperature increase during gas turbine operation.

It is desirable to install the above-mentioned ceramic fibrous insulation material over the entire inner surface of the casing as long as it can be applied, but the effect of the structure of the present invention may be affected especially at high temperatures. It may also be installed only in prominent parts, for example in the combustion chamber.

Embodiment FIG. 1 is a partial sectional view showing an example of a gas turbine casing with a heat insulating material of the present invention formed as described above. In this example, steel wool felt 2 is first applied to the inner surface of casing 1 using an inorganic adhesive (based on iron powder and sodium silicate).
Ceramic fiber-borosilicate vitreous molded body (bulk density 0.25 g/cm ³ , thickness 15 mm) 5 which was bonded by step 3 and was coated with borosilicate vitreous glaze 4 produced by the following manufacturing method. are bonded together using an inorganic adhesive (mainly containing alumina, kaolin, and colloidal silica). Note that the joint portion 7 is filled with a filler 8 which is a mixture of ceramic fibers and an inorganic adhesive.

[Production method of ceramic fiber-borosilicate glass molded body 5: Aluminosilicate ceramic fiber/Fine Flex (Nichias Co., Ltd.)
Add 100 parts by weight to 3000 parts by weight of 10% hydrochloric acid, and add about 60 parts by weight.
After heating to ℃ and stirring for 3 hours, the mixture is dehydrated and dried. Next, this acid-treated ceramic fiber and 3 parts by weight of boron nitride powder with an average particle size of 0.38μ were mixed in water to form a slurry with a solid content concentration of approximately 2% by weight, and a small amount of flocculant was added to form a slurry of boron nitride. The powder is fixed on the fiber surface, dehydrated and molded, then dried at 120°C and further baked at 1150°C for 10 hours. ] Effects of the Invention As mentioned above, the gas turbine according to the present invention has a ceramic fiber-borosilicate glass molded body with a bulk density of 0.1 to 0.8 g/cm ³ that has excellent heat resistance and strength, and is coated with a glaze to improve its surface characteristics. By elastically supporting the reinforced material with a fibrous pine layer, the casing is lined with a durable insulation material that withstands repeated high-temperature heating and cooling, and also withstands the wind pressure of high-speed combustion gas flow and vibrations during gas turbine operation. This makes it possible to reliably suppress the temperature rise of the casing, which in turn increases the combustion gas temperature and improves thermal efficiency even when using an inexpensive material with a low heat-resistant limit temperature for the casing. I can do it.

[Brief explanation of drawings]

FIG. 1 is a partial sectional view showing a casing portion of an example of a gas turbine according to the present invention, and FIG. 2 is an explanatory diagram of a conventional method of laminating a ceramic material on a metal material. DESCRIPTION OF SYMBOLS 1... Casing, 2... Steel wool felt, 3, 6... Adhesive, 4... Glaze, 5... Ceramic fiber-borosilicate glass molded body.

Claims (1)

[Claims] 1. A thin plate-shaped porous molded body with a bulk density of 0.1 to 0.8 g/cm ³ made by bonding ceramic fibers using borosilicate glass as a binder, with a glaze applied to one side and a thin heat-resistant coating on the other side. A gas turbine characterized in that a heat insulating material made by bonding fibrous pine is lined on a casing with the fibrous pine surface as a bonding surface. 2. The gas turbine according to claim 1, wherein the ceramic fiber is an aluminosilicate fiber.