JP2870778B2 - Gas turbine shroud structure - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a high-temperature and high-efficiency gas turbine used in various fields such as power generation and transportation, and in particular, improves an inner surface of a shroud which is in sliding contact with a blade tip. The present invention relates to a shroud structure of a gas turbine.

[Prior Art] In order to improve the efficiency of a conventional gas turbine, it is important to reduce the clearance between the blade tip and the shroud as much as possible and to reduce the leakage of gas passing between them. For this reason, an abradable seal that does not damage the blade side because the shroud surface is easily cut off even if the blade tip comes into contact with the shroud has been researched and developed.

In particular, in the case of a high-efficiency gas turbine having a high gas temperature at the turbine inlet, it is desirable to use ceramics for the abradable seal. Attempts have been made to form abradable seals.

[Problems to be Solved by the Invention] The ceramic abradable seal produced by the plasma spray method has the following problems because the ceramic particles are directly semi-molten bonded.

(1) If the material is made of a dense material having a low porosity, the material becomes hard and is not easily shaved by the blade tip. In particular, when ceramics are used for the moving blade, problems such as chipping of the moving blade tip occur.

(2) On the other hand, if a material having a high porosity is used, the hardness is reduced and the blade is easily shaved by the tip of the moving blade. The present invention has been made in view of the above circumstances, and has as its object to provide a shroud structure of a gas turbine which is easily shaved at the time of contact with a blade tip and hardly causes erosion due to dust or the like.

Means for Solving the Problems In order to achieve the above object, the present invention provides a shroud structure that slides on the tip of a moving blade, and has a particle diameter of 10 to 500 μm, which is higher in hardness than dust particles flowing into a turbine. The ceramic particles have a microstructure joined by a porous ceramic having pores of 1 μm or less and form a ceramic seal layer which is easily shaved by contact with the blade tip. It is joined to a metal shroud via an intermediate layer that absorbs the difference in thermal expansion.

[Operation] According to the above configuration, the ceramic seal layer can be easily scraped off by the tip of the blade, thereby improving the sealing property therebetween and also being durable against erosion.

EXAMPLES Preferred embodiments of the present invention will be described below with reference to the accompanying drawings.

In FIG. 1, reference numeral 1 denotes a ceramic moving blade attached to a rotating disk, and 3 denotes a shroud which is in sliding contact with the tip 1a of the moving blade 1, and is abradable (easy to cut) on the inner surface of a metal shroud 4 via an intermediate layer 5. A ceramic seal layer 6 is provided as a seal.

The ceramic seal layer 6 has a particle size of 10 as shown in FIG.
It is made of ceramics having a microscopic structure in which ceramic particles 7 having a size of about 500 μm are bonded by porous ceramics 8 having a pore diameter of 1 μm or less. The ceramic particles 7 are desirably ceramics having a Mohs hardness of 6 or more, higher in hardness than dust particles flowing into the turbine, and stable against oxidative corrosion or the like by a high-temperature gas. Silicon and the like are conceivable, but zirconia is most desirable in view of the fact that the difference in the coefficient of thermal expansion from the metal is small, and it is difficult to peel off as a seal. As the porous ceramics 8 of the bonding layer, the porosity is 10 to 50%.
When the porosity is too low, the hardness and strength are too high to make it difficult to cut, and when the porosity is too high, it is susceptible to erosion and easily breaks. As this material, alumina, zirconia, mullite, silica, silicon nitride, silicon carbide and the like can be considered. As a forming method, a solution of a soluble compound serving as a precursor of these ceramics, a dissolved polymer, an ultrafine particle (colloid) dispersion liquid, or the like is used, and these liquids and the ceramic particles 7 are mixed.
After forming into a seal shape, firing is performed to form a ceramic seal layer 6 having a microscopic structure.

The ceramic seal layer 6 is bonded onto the metal shroud 4 via an intermediate layer 5 that can absorb a difference in thermal expansion with a metal. The intermediate layer 5 may be made of a material having high flexibility, such as a molded article of heat-resistant metal fiber. The composition may be a mixture of ceramics and metal, and the composition may be continuous from the ceramic seal layer 6 side to the metal shroud 4 side. You may use the same gradient functional material which changes stepwise. Further, the joining method of the seal layer 6, the intermediate layer 5, and the shroud 4 includes brazing,
By diffusion (sintering) bonding or the like.

The reason for setting the particle size of the ceramic particles 7 to 10 to 500 μm is that if the particle size is 10 μm or less, the particles are weak to erosion,
If the thickness is more than μm, the blade 1 tip 1a is liable to be damaged.

The reason why the pore diameter of the bonding layer of the porous ceramic 8 is set to 1 μm or less is that the bonding layer is easily scraped and has durability against erosion. The erosion durability is improved by keeping the gap between the ceramic particles 7, that is, the thickness of the bonding layer of the porous ceramic 8 as small as possible.

 Hereinafter, more specific examples will be described.

(Example) A mixture of zirconia + 8% yttria particles having a particle diameter of 20 to 100 μm and zirconia sol, press-molding to form a seal, and baking are performed to contain 60% by volume of the zirconia-based particles, thereby forming a void. The average pore diameter is 0.1μ
m, a ceramic seal layer having a microstructure bonded with porous zirconia having a porosity of 40% was obtained.

On a metal shroud, a thin plate of a heat-resistant nickel alloy fiber molded sintered body is brazed to form an intermediate layer, and zirconia is plasma spray-coated thereon, and then the ceramic seal layer is bonded with a zirconia sol and fired. Sinter joining was performed.

The shroud structure thus obtained shows sufficient machinability and sealability in the tip contact sliding test with silicon nitride and ceramic blades, and has high durability in the erosion test of dust powder spraying. Indicated.

[Effects of the Invention] As described above, the present invention has the following effects.

(1) By forming the inner surface in sliding contact with the moving blade with a ceramic seal layer having a microscopic structure composed of ceramic particles and porous ceramic, an abradable seal can be easily scraped off by the moving blade tip to ensure an easy contact. Also in this case, the rotor blade side is not damaged and the sealing performance is good.

(2) Excellent durability against erosion due to dust and the like.

(3) As a high-temperature turbine, both efficiency and reliability can be improved.

[Brief description of the drawings]

FIG. 1 is a sectional view showing an embodiment of the present invention, and FIG.
It is an expanded sectional view of the part enclosed with the circle A in the figure. In the figures, 1 ... are blades, 3 ... are shrouds, 4 ... are metal shrouds, 5 ... are intermediate layers, 6 ... are ceramic seal layers.

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-53-82815 (JP, A) JP-A-63-170254 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) F01D 11/08

Claims (1)

(57) [Claims] In a shroud structure which slides on the tip of a moving blade, ceramic particles having a particle diameter of 10 to 500 μm, which are higher in hardness than dust particles flowing into a turbine, are bonded by porous ceramics having pores of 1 μm or less. A ceramic seal layer having a microstructure as described above and easily scraped by contact with the blade tip is formed, and this ceramic seal layer is joined to a metal shroud via an intermediate layer that absorbs a difference in thermal expansion. A shroud structure for a gas turbine, characterized in that: