JPS5941002B2 - Turbine wheel and diaphragm sealing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a sealing fin device for a turbine wheel and diaphragm for sealing wheel cooling air or gas leakage air from a previous stage in a gas turbine.

Gas turbines are becoming increasingly larger in capacity, and combustion gas temperatures are also becoming higher in order to improve efficiency.
Since it has a unique and essential feature of having to be heated twice (for 7 days), various measures against thermal deformation and thermal stress are essential.

In order to alleviate thermal deformation and thermal stress, a turbine wheel cooling system as shown in FIG. 1 is provided.

First, the cooling system shown in FIG. 1 will be explained.

Air 10 compressed by the compressor 1 is mixed with fuel and combusted in the combustor 2, becoming a high temperature gas 11 at about 1000° C. and flowing into the first stage nozzle 6.

Work is done on this gas by the first stage wheel 4 fixed to the rotor 3, and the temperature reaches about 750°C at the inlet of the second stage nozzle 70. After work is done by the second stage wheel 5, the exhaust gas 12
and is released.

This gas causes the first stage wheel 4 and the second stage wheel 5 to
The air bleed port 13 is installed in the middle of the compressor 1 because the wheel is exposed to high temperatures and the rotational strength of the wheel cannot be obtained, leading to damage.
is provided to extract cooling air 14 at a temperature of about 200°C,
This cooling air passes through the turbine shell 21, the second-stage nozzle 7, and the second-stage diaphragm 8 through holes 34, and is discharged between the first-stage wheel 4 and the second-stage diaphragm 80. 4 and the second stage wheel 5.

FIG. 2 shows details of the vicinity of the second stage diaphragm, which is the main component of this cooling system.

Annular fins 26 and 27 are concentrically protruded from the surface of the second diaphragm 8 facing the first stage wheel 4.
Also on the step wheel 4 side, corresponding to these fins 26 and 27, annular fins (hereinafter referred to as platform) 29 and 30 having a diameter slightly smaller than these fins are protruded.

An annular fin 28 is also protruded from the surface of the second stage diaphragm 8 facing the second stage wheel 5, and a corresponding platform 31 is also projected from the second stage wheel 5.

A portion of the cooling air 14 is directed toward the fins 2 as shown by arrows 32.
7 and the platform 30 and the gap between the fin 26 and the platform 29 to cool the first stage wheel 4, and the other part passes through the gap 35 between the labyrinth packing 9 and the wheel, and then flows as shown by the arrow 33, cooling the second stage wheel 5 while flowing through the gap between the platform 31 and the fins 28.

On the other hand, the high-temperature combustion gas 11 of 750° C. that has passed through the first stage bucket 22 has a direct high temperature effect on the second stage nozzle 7, the nozzle inner wall 25, and the nozzle outer wall 24 while passing through them, and also causes startup and shutdown. Sometimes, the temperature changes from room temperature to around 750℃ in a few minutes, and as it expands and contracts rapidly, thermal stress is generated, and permanent deformation occurs due to repeated startup and shutdown (twice a day). As a result, in the cold state during stoppage, the inner wall 25 side becomes open about 6 to 12 degrees on the horizontal plane, and in the hot state during load operation, this open state returns to the original state. It's being repeated.

As a result of this phenomenon, the diaphragm 8 moves up and down as will be explained below with reference to FIG.

That is, the nozzle 7 (7a and 7b are upper and lower half nozzles, respectively) and the diaphragm 8 (8a + 8b are upper and lower half diaphragms, respectively) are connected to four pins 36a to 36.
6d, the diaphragm 8 is connected in such a way that a slight change in the radial direction can be tolerated, and the vertical support of the diaphragm 8 is provided by a horizontal plane (the upper half turbine shell 21a and the lower half turbine shell 21
pins 36b and 36a slightly below 39 (junction surface with b)
, the center of the diaphragm 8 is directly affected by the deformation of the upper and lower nozzles 7a and 7b, and in the stopped cold state, the center of the diaphragm 8 is on the horizontal plane 3.
9, it sinks by about 3 to 8 mrn (37) L, and conversely, in a hot state, it rises about 1.5 mm above the horizontal surface 39 (38).

During this time, the center position of the diaphragm 8 will move by about 4.5 to 9.5 degrees.

For this reason, the fins 26-28 and the platforms 29-3
10 The gap also changes accordingly, and the upper half diaphragm 8a
In this case, due to the center position sinking when cold, the gap is significantly reduced, resulting in contact and sliding between the two.

Therefore, when starting from a cold state and stopping from a hot state, the rotor is turned at a low speed in order to equalize the temperature to prevent bending of the rotating part.

However, since there is no gap between the fins protruding from the stationary part and the platform of the rotating part, the capacity of this turning motor is insufficient due to frictional force generated by contact, resulting in a situation where turning is impossible. , Therefore, the turbine cannot be started.

In addition, when the diaphragm is hot, the gap expands due to the rising and falling of the diaphragm, and when it is cold, the gap becomes extremely large due to the expansion caused by withering.

On the other hand, the lower half diaphragm 8b exhibits a phenomenon opposite to the above-mentioned upper half diaphragm 8a, and the gap is large when it is cold, leading to a situation where it dries out a little when it is hot.

Such a change in the gap between the fins 26 to 28 and the rotor side and the possibility of trouble associated with it are caused by the diaphragm 8
This is a problem that can always occur where the nozzle is supported by the nozzle 7.

In the example shown in Fig. 3, the diaphragm 8 is connected to the lower nozzle half 7b by the pins 36b and 36d, and the diaphragm 8 is supported in the vertical direction mainly by this. Even if the structure is such that the connection is made using well-known means such as
This problem occurs in any configuration in which the diaphragm 8 is supported by b.

In either case, the lower half nozzle 7b is deformed due to the thermal expansion difference of the lower half nozzle 7b as described above, and the diaphragm 8 supported by it is also deformed, and the diaphragm 8 moves up and down accordingly. This is because a difference occurs between the vertical and horizontal gaps.

In order to avoid changes in the gaps between the fins 26 to 28 and the rotor sides and the resulting troubles, conventionally, as a countermeasure, the inner diameters of the diaphragm side fins 26 to 28 were made sufficiently larger than the outer diameters of the plant forms 29 to 31. The fins were set large to prevent contact between the fins and the platform even if the diaphragm deformed.

However, after the cooling air 32, 33 (FIG. 2) passing through the platform and fins cools the wheel,
It joins the mainstream of combustion gases 11 and 12, but since this air is at a low temperature, it is not converted into mechanical work, which not only results in a loss in terms of thermal efficiency, but also disturbs the flow of the mainstream gas, further contributing to a decrease in efficiency. I'm letting you do it.

Therefore, it is necessary to control the amount of cooling air to the minimum required for cooling the wheels.

However, if a large gap is provided between the fins and the platform as in the past, the amount of cooling air passing through will be larger than the minimum amount of air required for wheel cooling, resulting in an increased reduction in efficiency.

An object of the present invention is to provide a seal fin device that eliminates the above-mentioned drawbacks, and that can prevent the plant home of the wheel from coming into contact with the fins of the diaphragm in any operating state, and can also minimize the decrease in efficiency. It is in.

The present invention achieves the above object by providing a structure in which bulges are formed at the upper and lower portions of the diaphragm side fins to increase the gap with the platform.

FIG. 4 shows diaphragm side fins 26 and 27 according to the present invention.
．． 28, the upper part of the upper half and the lower part of the lower half of the diaphragm-side fin are provided with angular ranges indicated by θ so as to sandwich a vertical line 50 passing through the rotor axis.
Arc-shaped bulges 46a + 46b are formed respectively.

In this case, the angular range θ in which the bulges 46a and 46b are provided
is approximately 90 degrees to 100 degrees.

The bulges 46a and 46b are constructed as follows.

That is, the circular turbine wheel side fins 29°30
．． A point P2.31 is a point P2.31 which is centered at the center O of the parallel response, and the −L portion and the lower part of the arcuate portion 46c, whose radius is Ro, are eccentrically upward and downward from the center 0. Centered on R2', radius R
an arcuate bulge 46a whose radius is R2, which is smaller than 6;
This is provided by forming 46b, respectively.

In this case, the horizontal gap 41 between the outer diameter 49 of the plant form, which is the wheel side fin, and the inner diameter of the arcuate portion 46c of the diaphragm side fin, whose center is at point O, is a gap for cooling air to pass through, and whose center is at point P2. ．． The vertically increased gap 42 provided by the arcuate bulges 46a and 46b, denoted P2', is a gap that takes into consideration the ups and downs of the diaphragm.

It is sufficient that the entire annular gap constituted by both gaps ensures a minimum amount of air corresponding to the amount of air required for cooling.

The top of the bulging portion 4'6a and the bottom of the bulge 46b are located between the center O and points P2 and P2', and are located at the top of the elliptical diaphragm side fin 45 shown by the broken line with radius R1 being the same as Ro. Form to match the top and bottom.

Figure 5 shows the range of θ, which is the arc-shaped bulge in the fin configuration shown in Figure 4, and the minimum gap at the time of maximum deformation (the relative position of the plant form outer diameter at this time is indicated by 49'). 43 and the relationship between the range of θ and the amount of efficiency improvement.

The minimum gap 43 is 0 (mm) in order to prevent contact.
) or more, and therefore O (mm) is the contact limit.

However, even if it is 0 (mm) or more, when the minimum gap 43 becomes large, the efficiency deteriorates as described above.

Therefore, in order not to reduce the efficiency and also to prevent contact, it is most desirable to set the thickness to the minimum O (mm).

From FIG. 5, the angle that makes the minimum gap 43 zero is θ-9
It can be seen that the angle is close to 0 degrees.

Therefore, it is ideal to set it near 90 degrees, but even when designing with the aim of making the minimum gap 43 O (mm) near 90 degrees, in practice, there must be a processing tolerance. , it is necessary to take this into consideration in the design.

Referring to FIG. 5, the minimum gap 43 during deformation when θ is 100 degrees is 0.05 mm, which is an indispensable level for practical machining tolerances.

Therefore, θ is set in a range from around 90 degrees to around 100 degrees.

(90 degrees is possible if you have technology with zero processing tolerances).

In this way, if the angle θ is approximately 90 degrees or more, the plan 1 form and the diaphragm side fins will not come into contact with each other and wither, even during maximum thermal deformation (when the diaphragm is at its highest level). On the other hand, as the angle θ increases, the amount of efficiency improvement decreases, so the upper limit is set at around 100 degrees.

Looking at the amount of efficiency improvement in the figure, if θ is within this range, the inner diameter of the conventional diaphragm side fin can be simply changed to plant form 2.
When compared with a device in which contact between the two is prevented by setting the outer diameter to be sufficiently larger than the outer diameter of No. 9 to No. 31, it will be clear that the efficiency of this configuration is much improved.

Assuming a technique in which the fins are configured as shown by the dotted line 45, the gap is reduced by the portion surrounded by this and the solid lines 46a to 46c, and based on this, the effect of improving efficiency can be brought about.

For example, if θ is set to 100 degrees, the efficiency improves by 0.05% compared to the technique indicated by the dotted line 45.

From now on, it will be understood that the efficiency is better than the conventional technology.

FIG. 6 is a diagram showing another embodiment of the present invention.

In this embodiment, a bulge is formed over an angular range of θ degrees (near 100 degrees) around the center O of the diaphragm, and the bulge is formed as shown in FIG. An arcuate portion 46d centered at (this portion is α centered at point O)
(formed in the range of approximately 60 degrees) and the curved portion 46
Consists of e.

49 indicates the outside diameter of the plant form when the center O of the diaphragm coincides with the rotor axis, and 49' indicates the outside diameter of the plant form when the diaphragm has maximum floating (when the rotor axis coincides with the point σ). Indicates diameter.

With this configuration, the gaps between the platform and the diaphragm fins are 48a and 48b along the rotational direction of the rotor shown by the arrow.

The cycle of changing to 48c, narrowing at 48b, and increasing at 48c is performed at two places on the left and right in one rotation, and the rate of leakage of cooling air is further reduced than in the embodiment shown in Fig. 4. Greater efficiency.

Note that even when configured as in this embodiment, θ is 90 for the same reason as explained in the embodiment of FIG.
The range is from around 100 degrees to around 100 degrees.

The range of the curved portion 46e is determined corresponding to this θ.

As explained above, the seal fin device of the present invention has a configuration in which the nozzle and the diaphragm are each divided on a horizontal plane, and the diaphragm is supported by the nozzle, so that the diaphragm is supported in the vertical direction by the lower half nozzle. Although the device is used in a turbine, even if the diaphragm supported by the nozzle floats or sinks due to thermal deformation of the nozzle (particularly the deformation of the lower half nozzle), the relationship between the fins and the rotating gauntlet will be maintained. No contact occurs, and the decrease in efficiency can be kept to a minimum.

That is, in the present invention, the amount of air necessary for cooling is secured in the annular gap, and the upper and lower portions of the gap are bulged at the upper and lower portions of the diaphragm side fins so that the upper and lower portions are gaps that take into consideration the ups and downs of the diaphragm. The angular range of this bulge is approximately 90 degrees to 100 degrees, and in this case, the bulge is located on the wheel with the center of the fin being offset above and below the center of the fin on the wheel side. By providing an arcuate portion with a smaller radius than the side fins,
Either the upper and lower parts of the fins on the diaphragm side are bulged in two directions and downwards, respectively, or the upper and lower parts of the fins on the diaphragm side are provided with bulged arcuate parts, and the ends of these arcuate parts are not swollen. Since the protruding part is configured to be connected to the end of the fin by a curved part, the risk of the fin withering is reliably prevented by the bulging part, and there is no need for repair due to the withering. Naturally, there is no vibration due to fin deterioration, and the lack of capacity of the turning motor due to increased frictional force due to fin contact can be resolved, making smooth starting and stopping possible.

Furthermore, since it is possible to reduce the increase in the amount of gap in consideration of diaphragm floating and sinking, it has the effect of achieving an improvement in efficiency compared to the conventional one.

[Brief explanation of the drawing]

Figure 1 is a schematic system diagram for cooling the rotating wheel part with low-temperature cooling air, Figure 2 is a detailed diagram of the seal fin part, and Figure 3 is a detailed diagram of the seal fin part.
The figure is a cross-sectional view of the second stage nozzle and the diaphragm, FIG. 4 is a diagram showing the configuration of an embodiment of the diaphragm fin according to the present invention in comparison with a conventional example, and FIG. 5 shows the effect of the embodiment of FIG. 4. The figure shown in FIG. 6 is a diagram showing another embodiment of the present invention. 4... 1st stage wheel, 5... 2nd stage wheel, 7... 2nd stage nozzle, 8...
・Second stage diaphragm, 14... Cooling air, 2
6-28...Diaphragm side fin, 29-3
1...Wheel side fin, 41...Gap required for passage of cooling air, 42...Gap enlarged in consideration of diaphragm ups and downs, 46 a, 46 b...
...Arc-shaped bulge, 46c...Arc-shaped part (non-bulge), 46d...Arc-shaped part (part of the bulge), 46
e...Curved part (part of the bulge), θ...
・Angle range.

Claims (1)

[Scope of Claims] 1. A device used in a turbine in which a nozzle and a diaphragm are each divided in a horizontal plane, and the diaphragm is supported by a nozzle, so that the diaphragm is supported in the vertical direction by a lower half nozzle. , a seal fin device in which annular fins, the one on the diaphragm side having a larger diameter, are provided on mutually opposing surfaces of the turbine wheel and the diaphragm, and cooling air flows into the gap between the two fins, The upper and lower portions of the diaphragm-side fins are bulged so that the annular gap between them is suitable for the amount of air required for cooling, and the upper and lower portions of the annular gap are gaps that take into consideration the ups and downs of the diaphragm. The bulges at the top and bottom of the diaphragm side fins are formed over an angular range of approximately 90 degrees to 100 degrees across a vertical line passing through the rotor axis,
The bulging portion is formed by forming the upper and lower portions of the diaphragm side fins into arcuate portions having a radius smaller than that of the wheel side fins, with the centers being at points offset upward and downward, respectively, from the center of the wheel side fins. A seal fin device for a turbine wheel and a diaphragm, characterized in that the upper and lower portions of the diaphragm side fins are bulged upward and downward, respectively. 2. A device used in a turbine having a configuration in which a nozzle and a diaphragm are each divided in a horizontal plane, and the diaphragm is supported by a nozzle, so that the diaphragm is supported in the vertical direction by a lower half nozzle, and the turbine wheel and diaphragm are In a seal fin device in which annular fins, the one on the diaphragm side having a larger diameter, are protruded from mutually opposing surfaces of the fins, and cooling air is flowed into the gap between the two fins, the annular gap between the two fins is A bulge is provided at the upper and lower parts of the diaphragm side fin so that the upper and lower parts of the annular gap correspond to the amount of air required for cooling, and the upper and lower parts of the annular gap take into consideration the ups and downs of the diaphragm. The bulges bulging at the top and bottom of the side fins are formed over an angular range of approximately 90 degrees to 100 degrees between the vertical line passing through the rotor axis,
The bulging portion is formed into an arcuate portion by bulging the upper and lower portions of the diaphragm side fin, and the end of the arcuate portion is connected to the end of the non-bulging portion by a curved portion. In this case, the arcuate portion and the curved portion correspond to an angular range of around 60° and a bulging angle of the bulging portion, respectively, sandwiching a vertical line passing through the rotor axis. A seal fin device for a turbine wheel and a diaphragm, characterized in that the seal fin device is formed over an angular range of approximately 90 degrees to 100 degrees.