JPS5817324B2 - Heat shielding structure of metal structure in contact with high temperature gas atmosphere in gas turbine - Google Patents

Description

[Detailed description of the invention] The present invention relates to a turbine rotor blade in a gas turbine.

The present invention relates to a heat shielding structure for metal structures such as stator vanes and combustion tubes that are in contact with a high-temperature gas atmosphere.

It is well known that high-efficiency operation of gas turbines becomes possible by increasing the gas temperature at the turbine inlet, and the recent growing trend toward energy conservation has particularly required further increases in gas temperature. are doing.

By the way, one of the major reasons for the rise in gas temperature is to ensure that metal structures, such as turbine blades, can withstand the gas temperature and maintain mechanical strength. For example, as shown in Figure 1, the air cooling system is
It is necessary to increase the cooling effect by providing cooling holes inside and changing the method of circulating air through the holes to a liquid cooling method.

However, when the cooling effect is increased using this method, the difference between the temperature around the passage of the cooling medium and the temperature on the outer peripheral surface becomes a dog, creating a large temperature difference inside the turbine blade. target strength decreases.

Therefore, a new problem arises in that increasing cooling capacity has its own limits.

In order to fundamentally improve this problem, it is necessary to develop highly heat-resistant turbine blade materials, but at present no significant technological progress has been made in terms of materials.

Furthermore, these points also apply to the combustion tubes that supply high-temperature gas to the turbine blades, and from this point of view, the current situation is that the demand for increasing the gas temperature has hit a wall.

Therefore, in order to overcome this bottleneck, for example, as shown in Figure 2, the surface of the metal structure a that makes up the turbine blade is made of a material that has higher heat resistance than the metal structure but also has a lower thermal conductivity. A method has been proposed in which the turbine blades are coated with a heat shield C, and the heat flow to the turbine blades is suppressed to cope with gas temperatures in a range exceeding the limits of the cooling method described above.

According to this method, it is possible to suppress the above-mentioned thermal stress applied to the turbine blades and increase the gas temperature at the turbine inlet.

However, the above-mentioned heat shields, such as alumina and sintered zirconium, which have both high heat resistance and low thermal conductivity, as well as structures that rotate at high speeds such as turbine rotor blades, There are concerns about the mechanical strength of the product.

The present invention suppresses the heat flow to the turbine blades, that is, improves the heat shielding effect, and increases the gas temperature at the turbine inlet while minimizing the thermal stress applied to the turbine blades. The present invention aims to provide a heat shielding structure that can promote efficiency while at the same time reducing concerns regarding the mechanical strength of the heat shield.

Next, the details will be explained using the drawings.

According to experiments, as shown in Fig. 3, the surface of the metal structure a is covered with a sintered zirconium heat shield C, which has higher heat resistance and lower thermal conductivity than the metal structure, with a small gap d. Create a block e that simulates a turbine blade,
While cooling the metal structure a from the non-installed surface of the heat shield C (simulating cooling by cooling fluid passing through the cooling pores provided in the turbine rotor blade), the surface of the shield C is heated. g and measured the temperature distribution, it was revealed that the heat flow suppression effect in the gap d greatly (exceeds) the suppression effect of the shield C.

For example, the thickness of the heat shield is 3.2 mm, and the thickness of the cavity is approximately 0.2 mm.
It was revealed that the heat flow suppression effect in the gap is approximately twice that in the shield C when the heat flow is 2 mrn.

The present invention can further raise the gas temperature at the turbine inlet by covering the metal structure with a heat shield with higher heat resistance and low thermal conductivity so as to leave voids on the surface, and also provide a heat shield. Although it is inferior in thermal conductivity to alumina or sintered zirconium, it has excellent mechanical strength, such as sintered silicon nitride or sintered silicon carbide. The idea was to provide a turbine blade with high mechanical strength.

FIG. 4 is a partial perspective view of an embodiment of the present invention applied to a turbine rotor blade in which cooling holes are provided in the direction of action of centrifugal acceleration inside the blade, and FIG. 5 is a sectional view of the main part thereof.

In FIG. 4, reference numeral 1 denotes an airfoil-shaped metal structure, which is fixed onto a part of the rotor (not shown).

Reference numeral 2 denotes a plurality of cooling holes provided in the direction of action of centrifugal acceleration, one end of which is connected to a compressor (not shown) through a portion of the rotor, and air is introduced into the turbine working gas atmosphere through the opening of the cooling hole 2. Metal structure 1 in a spouting manner
cooling.

A heat shield 3 is provided to cover the surface of the metal structure of the rotor blade, and is made of, for example, a molded material such as sintered silicon nitride or sintered silicon carbide that can withstand high temperatures of 1000° C. or higher.

Reference numeral 4 denotes a gap provided between the heat shield and the metal structure, and the heat shield 3 is attached to the surface of the metal structure 1 so as to create the gap 4, for example, by the method shown in FIG.

In the example shown in FIG. 5a, the surface of the metal structure is divided into an appropriate number of cylinders as shown in FIG. A body piece 31 is used to hold a held hero 32 with a constricted base provided at the center of the inner surface of the body piece 31. It is assembled by fitting the holding grooves 11 into the holding grooves 11 one after another.

Further, in the example shown in FIG. 5, when two heat shield pieces 31 are butted against both ends of the inner surface of the heat shield piece 31 shown in FIG. A half-drawn retainer 33 is provided, and this is assembled by fitting into a retaining groove 11 provided on the metal structure 1 side.

Further, in the example shown in FIG. 5C, the holding groove 110 on the metal structure 1 side is
This is an example in which an uneven surface 5 such as a waveform or a square shape (waveform in the figure) is provided on the surface, and FIG. It is an improved version of

In addition to this, various modifications are possible, such as providing the holding groove on the heat shield side and providing the held member on the metal structure side.

In this way, a heat resistance layer formed by the heat shield and a heat resistance layer larger than the heat shield formed by the void are formed on the surface of the metal structure.

Therefore, compared to the case where the surface of the metal structure is covered with a heat shield without providing any air gaps, the effect of suppressing the inflow of heat into the metal structure is even greater, so cooling installed inside the turbine rotor blades In conjunction with the reduction in temperature of the metal structures forming the turbine rotor blades due to the pores, good protection of the metal structures takes place.

Furthermore, since the temperature difference between the outer circumferential surface of the metal structure and the temperature around the cooling hole is small, the decrease in mechanical strength due to thermal stress is also improved.

Therefore, even if the metal structure of the rotor blade is formed using the same material as in the past, it is possible to allow the gas temperature at the turbine inlet to rise, thereby achieving higher efficiency.

In addition, it is possible to increase the thermal conductivity of the heat shield by taking into account the effect of suppressing heat flow due to the voids. Instead of zirconium or the like, a heat shielding material such as sintered silicon nitride or sintered silicon carbide, which has poor thermal conductivity but high mechanical strength, can be used.

Therefore, a turbine rotor blade that can cope with concerns about mechanical strength can be obtained.

Tables 1 and 2 are examples of the results of trial calculations of the temperatures of turbine blades in the case of air/air cooling and the case of water cooling.

As is clear from this, in the case without the heat shielding layer of the present invention, for example, when the gas temperature is 1400°C in air cooling, the surface temperature of the metal structure of the rotor blade is 1135°C, and the temperature in the cooling part is 870°C. On the other hand, when the heat shielding layer of the present invention is present, the temperature becomes 738° C. and 605° C., the surface temperature is about 40 times smaller, and the temperature difference is about 50 times smaller.

Although the present invention has been explained above using turbine rotor blades as an example, it can be similarly applied to turbine stationary blades, and metal structures can be protected by providing a heat shielding layer on the inner circumferential surface of the combustion tube in the same manner as described above. It can be carried out.

As is clear from the above description, according to the present invention, the heat resistance of metal structures in contact with high-temperature gas atmospheres, such as turbine rotor blades, stator blades, and combustion tubes, can be greatly improved, thereby reducing the gas temperature at the gas turbine inlet. It has the excellent advantage of making it possible to raise the turbine and increase the efficiency of the turbine, making it extremely useful in practice.

[Brief explanation of the drawing]

1 and 2 are explanatory diagrams of a method for protecting turbine blades against gas temperature; FIG. 3 is an explanatory diagram of the principle of the present invention; FIGS. 4 and 5 are partial perspective views of an embodiment of the present invention; and a sectional view of main parts. DESCRIPTION OF SYMBOLS 1... Metal structure, 3... Heat shield, 4... Cavity part.

Claims (1)

[Claims] 1 A retaining protrusion having a constricted base is provided on the back surface of a heat shield piece having heat insulating properties, and a retaining groove for the protrusion having a constricted entrance part is provided on the surface of the metal structure to be shielded, and the protrusion is When the heat shield piece is inserted into the groove, there is a gap between the heat shield piece and the metal structure to be shielded, so that the metal structure is thermally shielded by the heat insulating properties of the heat shield and the gap. Thermal shielding structure for metal structures in contact with high temperature gas atmosphere in gas turbines.