JPH0729201Y2 - Turbine blade tip sealing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention is directed to a chip clearance formed between the tip of a turbine blade of a gas turbine, a jet engine, etc. and the inner peripheral surface of the turbine shell facing the turbine blade. The present invention relates to a turbine blade tip sealing device in which an abradable seal ring is provided on the inner peripheral portion of the turbine shroud in order to suppress the above as small as possible.

(Prior Art) In recent years, in order to raise the turbine inlet temperature of combustion gas and improve thermal efficiency and output, it has been considered to make turbine blades and turbine shells ceramic.

In what uses such a ceramic turbine blade, as an abradable seal ring on the inner peripheral portion of the turbine shell facing the tip of the turbine blade,
A seal ring mainly composed of a conventionally known metal (Japanese Patent Laid-Open No. 61
-149506 gazette) use.

(Problems to be solved by the invention) However, since the seal ring mainly composed of metal has low heat resistance, it is easily softened by the high temperature combustion gas flowing in the inner circumference of the turbine shell, and in some cases, it is softened. It was difficult to apply because it melts.

This means that, as disclosed in Japanese Patent Publication No. 59-5808, even when a plurality of ceramic coating layers are formed on the inner peripheral surface of a metal substrate by a thermal spray layer such as a plasma torch or a laser, there are almost the same problems. There is.

That is, when the ceramic coating layer is formed on the inner peripheral surface of the metal substrate as a sprayed layer, the sprayed layer is, as is well known, extremely thin and fragile, and furthermore, the bond strength with the metal substrate is weak, so that the turbine If the tip of the blade slides with strong rotational energy, it easily breaks or peels off, making it impossible to achieve the original initial purpose of the ceramic coating layer.

Also, as the turbine blade, instead of metal,
Even when it is made of ceramic as disclosed in Japanese Patent Publication No. 61-48604, there are almost the same problems.

This invention has been earnestly studied in order to solve the above problems.It improves the heat resistance of the abradable seal ring, prevents damage to the turbine blade even when used at high temperatures, and is made of ceramics. It is an object of the present invention to provide a turbine blade sealing device capable of maintaining high thermal efficiency and power output for a long period of time by using the turbine blade.

(Means for Solving the Problem) As a result of various researches, the inventor of the present invention has found that the bending strength of the ceramics and the wear characteristics have a close correlation, and the ceramics having a small bending strength are abradable. It was found that it can be used as a seal ring (inner part of shroud).

This invention was made on the basis of such research results, and the turbine blade tip sealing device according to this invention has a bulk density of 3 which has a bending strength of 10 Kg / mm ² or more.
It is composed of a heat-resistant ceramic member made of a dense sintered body of 2 g / cm ³ or more, and the inner peripheral portion of the turbine shell facing the tip of the turbine blade has a bending strength of about 10 Kg / mm ² or less. It has a bulk density of 1.97 g / cm ³ or less and is composed of a ceramic member made of a sintered body.

(Operation) According to the present invention, the inner peripheral portion of the shroud has a bending strength smaller than that of the ceramic material forming the turbine blade, in other words, the turbine shroud has a smaller bending strength than the turbine blade made of the dense sintered body. Since the peripheral part is made of porous ceramic material with low bulk density, the inner part of the shroud is more likely to wear than the wear characteristics of the turbine blade, and the abradability required for the inner part of the shroud While ensuring the heat resistance of this shroud inner circumference,
Even if it contacts with a turbine blade, seizure is less likely to occur, and as a result, damage to the turbine blade can be suppressed as much as possible.

Moreover, since the ceramic member forming the inner peripheral portion of the turbine shell is a sintered body, it is thicker than the case where the ceramic coating layer is formed on the inner peripheral surface of the metal substrate by a sprayed layer as in the prior art. Since it is meat and has high coupling strength, even if the tip of the turbine blade is brought into sliding contact with strong rotational energy, it is not easily broken and the original initial purpose of the ceramic member can be achieved.

(Embodiment) An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a cross-sectional view of a main part of a gas turbine according to an embodiment of the present invention. In FIG. 1, reference numeral 1 denotes a heat-resistant ceramic turbine shroud. It is fixed by a fit. Numeral 4 is a ceramic ring that constitutes the inner periphery of the shroud, that is, an abradable seal. This seal ring 4 is mainly composed of silicon nitride (Si ₃ N ₄ ) and has a bending strength of approximately 10 kg / mm ² or less. The ceramic member is made of a porous sintered body having the following bending strength and a low bulk density, and is joined to the inner peripheral surface of the turbine shell 1 in a replaceable state.

Reference numeral 5 denotes a turbine blade. The turbine blade 5 is made of a dense heat-resistant ceramic material having a bending strength of several tens of kg / mm ² or more, such as silicon nitride obtained by pressureless sintering. Several dozen sheets are fixed to the outer circumference of the sheet at appropriate intervals in the circumferential direction. A small chip clearance C is formed between the tip of the turbine blade 5 and the seal ring 4 facing the tip.

Next, a detailed description will be given of the procedure of the abrasion test conducted by the present inventor to find a suitable ceramic material as the seal ring 4 and the result of the abrasion test.

FIG. 2 is a schematic configuration diagram of the attrition tester. In FIG. 2, 10 is a rotor that fixes a plurality of simulated blades 11 corresponding to the turbine blades 5 on the outer periphery and rotates at a constant speed, and 12 is a seal ring 4. Is a sample holder that holds the sample 13 to be tested, which is a motor holder.
Further, it is possible to move in a direction in which the test sample 13 fixedly held is pressed against the simulated blade 11 in a rotating state via the slide mechanism 15 using a screw shaft.

Table 1 below shows the types and characteristics of the samples used for the abrasion test with the abrasion tester having the above-mentioned configuration.

Each sample in the table is an SN (silicon nitride) ceramic.

The seal ring samples No. 1 to No. 5 shown in Table 1 above are successively fixed to the sample holder 12 in the abrasion tester shown in FIG. Further, the pressing load generated when the pressing force is applied from the radial direction indicated by the arrow P in FIG. 2 at a constant speed, that is, the temporal change in the magnitude of the radial load is measured.

Fig. 3 shows a representative example of the above measurement results. Fig. 3 (a) is a radial load curve of sample No. 4, Fig. 3 (b)
Shows the radial load curve of sample No.2, and when comparing the two, the temporal change of the radial load magnitude (Kg) of sample No.2 is the radial load magnitude of sample No.4 (Kg)
It can be seen that it is much smaller than the change over time. This is presumed to be because the sample No. 2 has a lower bulk density than the sample No. 4 and is easily worn by the porous material, so that the radial load does not increase. In other words, sample No. 2 is suitable as an abradable seal.

By observing the above measurement results and the characteristics of each sample shown in Table 1, it can be understood that the radial load, that is, the abrasion characteristic has a close correlation with the bending strength of the material. That is, it is considered that the bonding force between the particles of the ceramic material is closely related to both the bending strength and the abrasion property.

From this point of view, when the correlation between the maximum value of the radial load and the bending strength of Sample No. 1 to Sample No. 5 shown in Table 1 above is taken, the results shown in FIG. 4 are obtained. It was

In Fig. 4, it is the sample No. 1 and the sample that satisfy the abradability required for the seal ring.
In No. 2, these have a bending strength of about 10 kg / mm ² or less. From these results, a suitable ceramic material as a seal ring is an estimated curve (X) shown by a chain line in FIG. It will be appreciated that it has the following flexural strength.

In the above-mentioned embodiment, the ceramic material containing silicon nitride as the main component is shown as the constituent material of the seal ring 4, but SiC and Si _{3 having} similar specific gravity and chemical properties to this silicon nitride are shown.
The ceramic member made of sialon and the like which is a solid solution of N ₄ + Al ₂ O ₃ may be used.

Further, although Table 1 discloses the bending strength and the porosity of the silicon nitride sintered body, the bending strength of the ceramic member is independent of the porosity, such as the sintering aid to be added and the atmosphere. The bending strength can be appropriately set depending on the firing conditions.

Therefore, even if the main components of the ceramic members forming the turbine blade 5 and the seal ring 4 are completely different,
The above-mentioned correlation between the bending strength and the abrasion characteristic is established.

(Effect of the Invention) As described above, according to the present invention, the inner peripheral portion of the shroud facing the tip of the heat-resistant ceramic turbine blade is
Since it is composed of ceramic members that have a smaller bending strength than the ceramic material that forms the turbine blade, the wear characteristics of the shroud inner circumference, which is closely related to the bending strength, are sufficiently smaller than the turbine blade, and the shroud inner circumference Since good abradability as a part can be secured and seizure at high temperature can be prevented, damage to the tip of the turbine blade can be suppressed as much as possible. It is possible to maintain high thermal efficiency and high output over a long period of time.

[Brief description of drawings]

FIG. 1 is a sectional view of an essential part showing an embodiment of the present invention, and FIG.
The figure is a schematic configuration diagram of the abrasion tester, Fig. 3 is a graph showing a measurement example of the change in radial load of the test sample, and Fig. 4 is the correlation between the radial load magnitude and bending strength of the test sample. It is a figure. 1 ... Turbine shroud, 4 ... Seal ring (inner circumference of shroud), 5 ... Turbine blade.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tatsumi Maeda 1-4 Yamashita-cho, Kokubun-shi, Kagoshima Prefecture Research Institute, Kyocera Corporation (56) Reference JP 59-5808 (JP, A) JP 61-48604 (JP, B1)

Claims (1)

[Scope of utility model registration request] 1. A turbine blade is composed of a heat-resistant ceramic member made of a dense sintered body having a bending strength of several tens of kg / mm ² or more and a bulk density of 3.2 g / cm ³ or more, and the tip of the turbine blade. The seal ring that forms the inner peripheral part of the turbine shroud facing to is a non-oxide ceramic member having a bending strength of approximately 10 kg / mm ² or less and a bulk density of 1.97 g / cm ³ or less. A turbine blade tip sealing device characterized by: