JP5595241B2 - Gas turbine, split segment, and split segment forming method - Google Patents

Description

  The present invention relates to a gas turbine used for an aircraft engine or the like, a divided segment used therefor, and a method for forming a divided segment.

In a gas turbine, air is compressed by a compressor into high-temperature and high-pressure compressed air, and fuel is supplied to the compressed air and burned in a combustor to generate high-temperature and high-pressure combustion gas. This high-temperature and high-pressure combustion gas is sent to the turbine, which expands in the turbine to rotate the main shaft and obtain a driving force.
The inside of the gas turbine is very high at 1300 ° C. at the time of start-up, and a large temperature difference is generated with the room temperature outside the casing.
In connection with this, deformation | transformation by a thermal stress may arise in various components which comprise a vehicle casing and a gas turbine, and various countermeasures with respect to this have been proposed (for example, refer patent documents 1 and 2). .

  Incidentally, as shown in FIG. 6, in the gas turbine 1, in order to ensure sealing performance between the rotor blade 3 of the turbine 2 and the turbine case 4 fixedly provided on the casing side, Some turbine casings 4 are provided with an annular tip shroud 5 on the inner wall portion thereof. The inner peripheral surface 5a of the tip shroud 5 is opposed to the tip 3a of the rotor blade 3 with a minute clearance C therebetween, thereby preventing combustion gas from leaking between the rotor blade 3 and the tip shroud 5. .

The tip shroud 5 includes a ring segment 6 formed by dividing the tip shroud 5 into a plurality in the circumferential direction for assembly reasons.
As shown in FIG. 7, the ring segment 6 has an arc shape as a whole. In the ring segment 6, hook portions 7 and 8 that are locked to the turbine case 4 are integrally formed on the side (outer peripheral side) facing the turbine case 4. A plurality of hook portions 7 and 8 are formed at intervals from each other along the circumferential direction of the gas turbine 1.

JP 2008-144617 A Japanese Utility Model Publication No.59-172208

For such a ring segment 6, during operation, the opposed surface 6 a side facing the rotor blade 3 is at a high temperature of about 1000 ° C. even if heat-resistant coating is applied to contact the combustion gas. Since the case 4 is cooled to a temperature of about 500 ° C., the side facing the turbine case 4 has a temperature of slightly over 500 ° C.
Due to the thermal stress acting on this, each ring segment 6 constituting the tip shroud 5 and its inner peripheral surface 6a are not in the circumferential direction (the circumferential direction of the gas turbine 1) as shown in FIG. 7B. Deforms uniformly. This is because the temperature difference between the inner peripheral surface 6a facing the rotor blade 3 and the side (outer peripheral side) on which the hook portions 7 and 8 are formed (on the side on which the hook portions 7 and 8 are formed) A difference in thermal expansion caused by heat escaping to the turbine case 4 side through the portions 7 and 8 occurs between the inner peripheral side and the outer peripheral side. Here, FIG.7 (b) has shown the deformation | transformation shape of the internal peripheral surface 6a at the time of the driving | operation when the notch 9 mentioned later is not provided for convenience.
Further, the ring segment 6 is usually provided with a notch 9 as a measure against thermal stress. However, in the circumferential direction of the ring segment 6, the portions where the hook portions 7 and 8 are formed and the hooks adjacent to each other. The mechanical characteristics (rigidity, heat capacity, etc.) are also different from those of the notch 9 existing between the portions 7 and 8. As a result, as shown in FIG. 7 (c), notches existing between the hook portions 7 and 8 adjacent to each other with respect to the place where the hook portions 7 and 8 are formed in the circumferential direction of the ring segment 6. In the portion 9, the deformation amount becomes small. Accordingly, as shown in FIG. 8, the clearance C between the tip shroud 5 (ring segment 6) and the rotor blade 3 also becomes nonuniform in the circumferential direction. In order to prevent an accident in which the tip shroud 5 and the rotor blade 3 come into contact during operation, it is necessary to secure this non-uniform amount in the circumferential direction as a design margin. I had to make it bigger. However, since the clearance C between the tip shroud 5 and the rotor blade 3 is directly related to the fuel efficiency and performance of the gas turbine 1, it is preferable to make the clearance C uniform and small.

  The present invention has been made based on such a technical problem. A gas turbine capable of improving the performance of the gas turbine by making the clearance between the tip shroud and the moving blade uniform in the circumferential direction to reduce the clearance. An object of the present invention is to provide a divided segment and a method for forming the divided segment.

For this purpose, the gas turbine of the present invention has a casing that forms the outer shell of the gas turbine, a turbine blade provided in the casing, and a fixed clearance between the tip of the blade and a specified clearance. separated by by opposing, and a annular sheet shroud to maintain the sealing property between the rotor blades, shea shroud from a plurality of divided segments obtained by dividing the equivalent 該Shi shroud in the circumferential direction Therefore, the facing surface facing the tip of the moving blade in the divided segment is an uneven surface at normal temperature, and when the gas turbine is operated, it is an arc surface separating a certain clearance in the circumferential direction from the moving blade. It is characterized by that.
By forming the concavo-convex surface in this way, the opposing surface becomes an arc surface that separates a certain clearance in the circumferential direction from the moving blade when the gas turbine is operated and becomes a high temperature state.
Such an uneven surface can be formed by machining the opposing surface. Moreover, a coating layer can be formed in an opposing surface and an uneven surface can be formed in the said coating layer.

  The divided segment may have any configuration, but a hook portion for locking the divided segment on the casing side may be formed. In this case, a plurality of hook portions can be provided at intervals in the circumferential direction in the entire divided segment, but can also be formed only at both ends in the circumferential direction in the divided segment.

Between the sheets shroud and the casing may be provided with a heat insulating layer.

Further, the present invention is fixed to a casing that forms an outer shell of a gas turbine, and is opposed to a tip of a moving blade of the turbine provided in the casing with a predetermined clearance therebetween, thereby sealing between the moving blades. An annular shroud that maintains its performance is divided in the circumferential direction, and the opposed surface facing the tip of the rotor blade is a rough surface at room temperature. It can also be a divided segment characterized by a circular arc surface with a certain clearance in the circumferential direction between the blades .

Furthermore, in the present invention, the opposed surface facing the tip of the moving blade in the divided segment as described above is an arc surface separating a certain clearance in the circumferential direction with the moving blade in a state where the gas turbine is operated, A step for obtaining data indicating the shape of the arc surface when it returns to room temperature by finite element analysis, and processing the facing surface of the divided segment into a shape when it returns to room temperature at room temperature based on the obtained data. And a segmented segment forming method characterized by comprising the steps.

  According to the present invention, in the operating state of the gas turbine, the opposing surface (inner peripheral surface) of the tip shroud with respect to the rotor blade is an arc surface, so that the clearance between the tip shroud and the rotor blade is made uniform in the circumferential direction. It is possible to improve the performance of the gas turbine.

It is sectional drawing which shows the principal part of the gas turbine in this Embodiment. It is a figure which shows a ring segment, Comprising: (a) Side sectional view, (b) is a view seen from the direction orthogonal to the axis of the turbine, (c) is an uneven surface formed on the opposing surface (inner peripheral surface), It is a figure which shows typically the circular arc surface in the state which act | operated the gas turbine. It is a figure which shows the other example of a ring segment. It is a figure which shows the further another example of a ring segment. It is sectional drawing which shows the example which formed the heat insulation layer between the ring segment and the casing. It is sectional drawing which shows the chip | tip shroud in the conventional gas turbine. It is a figure which shows the conventional ring segment, Comprising: (a) Side sectional drawing, (b) is the model which looked at the deformation | transformation state of the ring segment by the heat influence in the case of not having notched from the direction orthogonal to the axis line of a turbine. FIG. 4C is a schematic view of a deformed state of the ring segment in consideration of mechanical characteristics in the case where there is a notch, as viewed from a direction perpendicular to the axis of the turbine. It is a figure which shows the deformation amount of the conventional ring segment.

Hereinafter, the present invention will be described in detail based on embodiments shown in the accompanying drawings.
FIG. 1 is a view for explaining a main part of a gas turbine 10 in the present embodiment.
The gas turbine 10 is provided with an air intake, a compressor, a combustor, and a turbine 11 in a casing casing that forms an outer shell of the gas turbine 10 from the upstream side to the downstream side of the air flow. And the air taken in from the air intake is compressed by the compressor, and is sent to the combustor as high-temperature and high-pressure compressed air. In the combustor, fuel is supplied to the compressed air and burned to generate high-temperature and high-pressure combustion gas. This high-temperature and high-pressure combustion gas is injected into the turbine 11, expands in the turbine 11, and rotates the turbine 11. The compressor blades connected to the main shaft of the gas turbine 10 are driven by the rotational energy of the turbine 11.

  Now, in such a gas turbine 10, a plurality of turbine disks 12 provided integrally with the turbine 11 are provided at intervals in the axial direction of the turbine 11. A rotor blade 13 is integrally provided on the outer peripheral side of each turbine disk 12.

  An annular ring positioned on the outer peripheral side of the moving blade 13 on the inner wall portion of the turbine case 14 in order to ensure sealing performance between the moving blade 13 and the turbine case 14 fixedly provided on the casing side. The chip shroud 15 is provided. The inner peripheral surface 15a of the tip shroud 15 faces the tip 13a of the rotor blade 13 with a clearance C of 0.5 mm or less, for example, so that combustion gas leaks from between the rotor blade 13 and the tip shroud 15. prevent. Especially for small aircraft turbines, clearance management is performed in units of 0.1 mm, and it is important to reduce clearances in units of 0.1 mm.

  The tip shroud 15 includes a ring segment (divided segment) 16 formed by dividing the tip shroud 15 into a plurality of portions in the circumferential direction. As shown in FIG. 2, each ring segment 16 has an arc shape, and an annular tip shroud 15 is configured by connecting a plurality of ring segments 16 to each other.

Each ring segment 16 is integrally formed with hook portions 17 and 18 that are locked to locking portions 14 a and 14 b provided on the turbine case 14 on the side (outer peripheral side) facing the turbine case 14. Here, the shapes of the locking portions 14a and 14b and the hook portions 17 and 18 are not limited at all, and it is allowed to have an appropriate shape and structure other than those illustrated.
A plurality of such hook portions 17 and 18 are formed at intervals along the circumferential direction of the gas turbine 10, and a notch 19 is formed between the hook portions 17 and 18 adjacent to each other in the circumferential direction. Has been.

In such a ring segment 16, the opposing surface (inner peripheral surface) 16a facing the rotor blade 13 has an arc shape as a whole.
Furthermore, in the present embodiment, an uneven surface 20 is formed on the facing surface 16 a of the ring segment 16. The uneven surface 20 forms a circular arc surface 20 </ b> C having a concentric arc shape with respect to the center of the turbine 11 when the gas turbine 10 is activated and high-temperature combustion gas passes through the turbine 11. It is formed so as to face the front end 13a with a certain clearance C in the circumferential direction.

Such an uneven surface 20 may be formed by directly machining the facing surface 16a of the ring segment 16, or a coating layer such as a heat and oxidation resistant coating is formed on the coating layer. Also good.
The concave / convex surface 20 is first in a high temperature state (when the gas turbine 10 is started and high-temperature combustion gas has passed through the turbine 11) on the opposing surface 16 a of the ring segment 16 by FEM (finite element method) analysis. The difference between the surface shape of the facing surface 16a of the ring segment 16 and the surface shape in the normal temperature state (ambient ambient temperature state when forming the uneven surface 20) is analyzed, and the arc surface 20C is formed in a high temperature state from this difference. It is determined by calculating the shape in the normal temperature state to be performed.
Then, based on the surface distribution data obtained by the analysis, the uneven surface 20 is formed on the facing surface 16a of the ring segment 16 by machining or the like at room temperature.

  Thus, by forming the uneven surface 20 on the opposed surface 16a facing the rotor blade 13 in the ring segment 16, the gas turbine 10 is activated and the high-temperature combustion gas has passed through the turbine 11. In this case, the facing surface 16a of the ring segment 16 becomes an arcuate surface 20C facing the tip 13a of the rotor blade 13 with a certain clearance C in the circumferential direction. As a result, the clearance C can be designed in a state in which the margin for non-uniform deformation in the circumferential direction is eliminated, so that the clearance C can be made narrower than before, and the fuel efficiency and performance of the gas turbine 10 can be improved.

In addition, in the said embodiment, there is no intention which limits at all about the specific shape of hook parts 17 and 18, the number of installation, and an installation interval.
For example, as shown in FIG. 3, the hook portions 17 and 18 may be formed at a larger interval in the circumferential direction than the configuration shown in FIG. 2, and the circumferential length of the notch 19 may be increased. good.

  Further, as shown in FIG. 4, the hook portions 17 and 18 may be provided only at both ends in the circumferential direction of the ring segment 16. In this case, the amount of heat escaping to the turbine case 14 side can be suppressed by reducing the number of hooks 17 and 18 installed as compared with the examples of FIGS. 2 and 3, and the radius of the gas turbine 10 of the hooks 17 and 18 can be suppressed. The temperature difference in the direction can be reduced. Further, by reducing the number of hook portions 17 and 18 as compared with the examples of FIGS. 2 and 3, the rigidity of the ring segment 16 is reduced, and the circumferential intermediate portion 16c of the ring segment 16, that is, the hook portions 17 at both ends, The rigidity in the part between 18 becomes low entirely, and the nonuniform deformation | transformation in this part can also be suppressed.

Further, as shown in FIG. 5, a material having lower thermal conductivity than the turbine case 14 or the ring segment 16 and having a necessary and sufficient mechanical strength, for example, ceramic, between the turbine case 14 and the ring segment 16. It is also possible to sandwich a heat insulating layer 30 made of foamed metal, heat resistant coating, or the like.
Thereby, the amount of heat escaping from the ring segment 16 to the turbine case 14 can be suppressed, and uneven temperature distribution in the circumferential direction and uneven deformation in the circumferential direction can be suppressed.

In the above-described embodiment, the configuration in which the uneven surface 20 and the heat insulating layer 30 are provided on the ring segment 16 has been described. However, the other portions of the gas turbine 10 may have any structure.
Further, in FIG. 2C, the uneven surface 20 formed on the facing surface 16a is shown, but this is only a schematic diagram with the unevenness emphasized, and the shape is not restricted to what is shown in the figure. Needless to say, the shape is based on actual analysis.
In addition to this, as long as it does not depart from the gist of the present invention, the configuration described in the above embodiment can be selected or changed to another configuration as appropriate.

  DESCRIPTION OF SYMBOLS 10 ... Gas turbine, 11 ... Turbine, 13 ... Moving blade, 13a ... Tip, 14 ... Turbine case, 15 ... Tip shroud, 15a ... Inner peripheral surface, 16 ... Ring segment (divided segment), 16a ... Opposite surface (inner periphery) Surface), 17, 18 ... hook part, 20 ... uneven surface, 20C ... circular arc surface, 30 ... heat insulation layer

Claims (8)

A casing that forms the outer shell of the gas turbine;
A turbine blade provided in the casing;
Fixed to said casing, by opposed spaced tips and provision of clearance of the rotor blade, and a annular sheet shroud to maintain the sealing property between the moving blade,
Before carboxymethyl shroud is comprised of a plurality of divided segments obtained by dividing the equivalent 該Shi shroud in the circumferential direction,
In the divided segment, the facing surface facing the tip of the moving blade is an uneven surface at room temperature, and in a state where the gas turbine is operated, an arc having a certain clearance in the circumferential direction with the moving blade A gas turbine characterized by being made into a surface.   The gas turbine according to claim 1, wherein the uneven surface is formed by machining the facing surface.   The gas turbine according to claim 1, wherein a coating layer is formed on the facing surface, and the uneven surface is formed on the coating layer.   The gas turbine according to any one of claims 1 to 3, wherein the divided segment is formed with a hook portion that locks the divided segment to the casing side.   The gas turbine according to claim 4, wherein the hook portion is formed only at both ends in the circumferential direction in the divided segment. Between the front carboxymethyl shroud and the casing, the gas turbine according to any one of claims 1 5, characterized in that the heat insulating layer is provided. It is fixed to the casing that forms the outer shell of the gas turbine, and maintains the sealing performance between the moving blades by facing the tip of the moving blade of the turbine provided in the casing with a predetermined clearance. A divided segment formed by dividing an annular shroud in the circumferential direction,
The facing surface facing the tip of the moving blade is an uneven surface at room temperature, and when the gas turbine is operated, it is an arc surface with a certain clearance in the circumferential direction between the moving blade and the moving blade. A segment that is characterized by A method for forming a divided segment according to claim 7 ,
The facing surface facing the tip of the moving blade in the divided segment is an arc surface that separates a certain clearance in the circumferential direction between the moving blade and the gas turbine when the gas turbine is operated, and the arc surface is at room temperature. A step of obtaining data indicating a shape when returning by finite element analysis,
Based on the data obtained, at room temperature, the steps of processing the facing surface of the divided segments to the shape when returned to the room temperature,
A method for forming divided segments, comprising:

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