JPS601306A - Axial flow turbine - Google Patents

Abstract

PURPOSE:To enhance the reliability by making a spill strip fixed to the casing in eccentricity with respect to the rotor blade in the direction in which the spill strip displaces, and thereby preventing contact of the spill strip with the tip of rotor blade caused by thermal deformation of the casing. CONSTITUTION:This axial flow type steam turbine has a rotor 2, on which rotor blades 3 in many rows at a certain spacing in axial direction are installed at the periphery in such a way as planted, and a nozzle diaphragm 4 for spraying steam to the rotor blades 3 is fixed to the inner casing 5. Facing this nozzle diaphragm 4 a plurality of spil strips 10 are formed projectingly in such an arrangement as facing the periphery of a shroud 7 to couple the tips of rotor blades 3 with a certain spacing reserved, so as to prevent leak of steam. Here each spill strip 10 is formed so as to be located with its center eccentric downward from the center of the rotor blade 3, and the gap @ra to the rotor blade 3 shall be larger than conventional construction in the lower half of the spill strip 10.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to axial flow turbines such as steam turbines and gas turbines, and particularly relates to rotor blade tips and labyrinths or radial spill strips (hereinafter simply referred to as spill strips).
This invention relates to an axial flow turbine that significantly reduces contact with the axial flow turbine.

[Technical background of the invention and its problems]

Generally, the rotor blades of a steam turbine are the part that converts the energy of the high-temperature, high-pressure steam emitted from the nozzle into rotational force.
As a rotating body, it is exposed to severe stress. In recent years, as the capacity of steam turbines has increased, the size of the rotor blades has also increased, and improvements in the reliability of these rotor blades are increasingly required to prevent scheduled operation.

FIG. 1 is a longitudinal sectional view showing the overall configuration of a conventional axial flow steam turbine, and reference numeral 1 in the figure indicates an outer casing. A rotor 2 is housed in the outer casing 1, and a large number of rotor blades 3 are installed on the outer periphery of the rotor 2 at appropriate intervals in the axial direction of the rotor 2. The nozzle diaphragm 4 that spouts high-temperature, high-pressure steam to this dynamic R3 is the nozzle diaphragm 4 and the work! It is fixed to an internal casing 5 that accommodates A3 etc.

A convex tenon 6 is formed at the tip of the six T↓3 as shown in Figure 2 (enlarged view of part A in Figure 1), and the shroud 7 is fitted into the convex part of the tenon 6. A suitable number of rotor blades 3 are placed in one group surrounding the outer periphery of the Hg3 to structurally reinforce the Hg3. For this reason, the tip of the rotor blade is surrounded by a shroud 7 that is divided into two parts. A spill strip 8 is provided on the outer periphery of this shroud 7 (upper part in FIG. 2).
are disposed facing the shroud 7 at appropriate intervals, and the spill strip 8 is made up of two protrusions arranged annularly in parallel on the nozzle diaphragm 4 so as to sandwich the convex portion of the tenon 6 at nine intervals. , which prevents steam from collapsing at the tips of the rotor blades. The gap between the tip of the spill strip 8 and the tip of the shroud 7 is uniform over the entire circumference of the shroud 7. That is, as shown in FIG.
The fi (J gap Δr) with the outer diameter R2 is formed concentrically with these 7.8, and is uniform over the entire outer circumference of the shroud 7.

By the way, in the process of starting and stopping a steam turbine, a temperature difference occurs between the upper and lower halves of the inner and outer casings 5.1, which are stationary parts. At the time of startup, water droplets remain on the T halves of the internal and external casings 5 and 1 (this water droplet cannot be removed structurally even with the piping of the drain plate (not shown)). The lower half has a lower temperature than the upper half. On the other hand, when the engine is stopped, the upper half cools faster than the lower half due to thermal convection, and the upper half is still higher in temperature than the lower half. This temperature difference between the upper and lower halves is within the steam turbine.

This is an unavoidable problem when structures such as the outer casing 5,1 are damaged. Then, when the temperature of the upper half of the inner and outer casings 5, 1 becomes higher than that of the lower half, the segmental casing 5 undergoes a convex thermal deformation and becomes a so-called hunched back shape. As the internal casing 5 thermally deforms, the spill strip 8 fixed to the internal casing 5 via the diaphragm 4 is displaced upward in a direction perpendicular to the axial direction of the internal casing 5. For this purpose, the gap Δr between the inner diameter R1 of the spill strip 8 and the outer diameter Iζ2 of the shroud 7 is
is no longer uniform over the entire circumference, and the gap on the vertically upper side of the inner casing 5 becomes larger, while the gap on the lower side becomes correspondingly smaller. If this lower gap 4 (' only) was removed, the outer circumferential edge of the shroud 7 and the tip (inner circumferential edge) of the spill strip 8 would come into contact, resulting in a loss of 1D.

[Purpose of the invention]

``Honkoyu'' was created in consideration of the above-mentioned considerations, and by taking thermal deformation of the casing into consideration, the gap between the tip of the rotor blade and the spill strip was set, and the distance between the tip of the rotor blade and the spill strip was set. An object of the present invention is to provide an axial flow turbine that can prevent contact between the rotor blades and damage to the rotor blades caused by the contact, thereby improving the health and reliability of the turbine rotor blades.

[Summary of the invention]

The present invention is configured as follows to achieve the above-mentioned object.

A spill strip is placed around the outer periphery of the tip of the movable blade installed on the rotating shaft with a gap of 79 mm, so that when the spill strip is displaced, it does not come into contact with the tip of the rotor blade. The spill strip is eccentrically arranged with respect to the above-mentioned motion microscope in the direction of the tilt direction.

[Embodiments of the invention]

An embodiment of an axial flow turbine according to the present invention will be described below with reference to the drawings.

FIG. 4 is an explanatory diagram illustrating an embodiment of a rotor blade tip pool structure in an axial flow turbine according to the present invention,
In the figure, ladle number 10 is a spill stick. This spill strip 101d: its center is as shown in Figure 4,
It is formed so as to be eccentric downward from the center of the dynamic R3 in the vertical direction of this center.

That is, in the upper half of the spill strip 10, the gap between the inner diameter R3 of the spill strip 10 and the outer diameter R4 of the tip end (shroud 7) of the moving arm 3 is set to Δr as in the conventional spill strip 8. In the lower half of the spill strip 10, the spill strip 10 is eccentrically machined so that the gap is set to Δra, which is larger than the above-mentioned gap Δr. Therefore, the spill strip 10 is formed into a kind of circular shape as shown in FIG. 4(B), and is fixed so that its major axis coincides with the vertical direction of the inner casing 5. By performing conversion-8, the center of the spill strip 10 is eccentrically downward in the vertical direction from the center of the rotor blade 3 by ω. A method of calculating this displacement ω in the vertical direction will be explained based on FIG. 5. FIG. 5 is a longitudinal cross-sectional view of the thick-walled cylinder, 1li of the inner casing 5.
L length f: t, the same outer diameter is replaced by d.

Here, assuming that the temperature distribution in the circumferential direction of the thick-walled cylinder is linear, the maximum deformation amount ωmax can be expressed by the following equation (1).

However, t: Length of the cylinder d: Outer diameter of the cylinder β: Coefficient of linear expansion at average temperature Tmu: Temperature on the upper half side Tmt: Temperature on the lower half side This equation (1) can be expressed as shown in Figure 1. I like complicated 4M construction.
When applying this method to a casing, the influence of the horizontal flange (not shown) and its axial temperature distribution must be considered. Therefore, 1°K2 is added to the coefficient in equation (1).

However, K1 is a coefficient due to the rigidity of the horizontal flange, and 2 is a coefficient due to the axial temperature distribution of the casing. Measurement data on the casing and FEM (Finite Element
ent Metbod + finite element method) analysis is required. Further, the relation pK□ can be determined by the following equation (3).

+ R@W-H) However, in the above formula (3), d, , d2. R.

W and I-1 represent the dimensions of each part shown in Figure 856.

By the way, it is known that the temperature difference between the upper half and the lower half of the casing during operation of recent large-scale steam turbines can be as large as about 5,000 degrees during transient conditions such as when the turbine is started. So - for example d=2200a, t=50
In the case of a large casing of 00W-A, when the vertical displacement ω is calculated using the above equation (3), the following is obtained.

=KI K2 x O, g mm Here, the coefficient is 1. 2 is 1 = 0.6 to 1.0°K2 in the casing structure of steam turbines currently manufactured.
Since the key is 0.8, K = Klm K2 = 0.5-
(), becomes 8. Therefore, in a large casing with the above dimensions, the vertical displacement ω can be expected to be in the range of about 0.45 to 0.72 mrn. However, this range of vertical displacement ω is only a rough guideline, and H'(' Ji
In order to determine li, it is necessary to refer to test data, FEM analysis, or operating records of the machine, for example, 0.15.
If the distance is set to 1.0 m or 1.0 m, it is possible to deal with various types of power turbines, from thermal power turbines to nuclear power turbines, as shown in Fig. 7. Figure 7 (the rectangles with fF lines are for each I
The eccentricity ω(fi) of the spill strip 10, which is set according to each capacity of Jmethane, is shown in the vertical axis direction, *
A shows a steam turbine that is normally operated. In addition, in the case of so-called intermediate negative power generation such as during night-time shutdowns, the internal and external casings 5 and 1 have a large transient temperature difference between the upper and lower halves, so the eccentricity of the spill strip 0 The amount can also be increased accordingly. In addition, when changing the one used for base load to intermediate load, as shown in Fig. 7, the spill strip 10 is
If t p+ processing is done, there will be no damage to the shroud 7 and rotor blade 3; 3
can be prevented.

In this way, as shown in Figure 4 (g)), the amount of eccentricity
The spill strip 10 is formed to be eccentric with respect to the spill strip 10.
As shown in rev. 41, the center of the rotor blade 3 is eccentric downwardly on a vertical line passing through these centers by an eccentric amount ω, and the gap Δra in the lower half of the spill strip 10 is smaller than the upper half. It is fixed to the diaphragm 4 so that the gap Δr between the parts is also large. As a result, a convex thermal deformation occurs in the internal casing 5 to which this diaphragm 4 is further fixed, and even if the spill strip [-] is displaced upward in the vertical direction of its center, this spill The lower half of the strip 10 has a gap Δra with the tip of the rotor blade 3
While the spill strip is above 10, it is 11 and 1.
Therefore, contact with or damage to the tip of the rotor blade 3 is reliably prevented.

In the above embodiment, the spill strip 10 is 1ii1
Although an example has been described in which the spill strip 11 is eccentrically downward in the vertical direction with respect to the center of 7R3, the present invention is not limited to this. For example, as shown in FIG. The rotor blade 3 may be eccentric upwardly on a vertical line passing through the center thereof. This is suitable for special cases where the thermal fatigue of the lower half of the inner and outer casings 1 is higher than that of the upper half. Furthermore, as shown in FIG. 9(4), the spill strip 12 may be eccentric in both up and down directions on a vertical line passing through the center of the moving frame 3. In this case, as shown in FIG. 9B, the eccentricity ω1 in both the vertical and vertical directions. ω2 does not necessarily have the same center and back, and may be formed to be different from each other. Depending on the operating conditions of the steam turbine, the inner and outer casings 5,
This is suitable for cases where high temperatures occur in both the upper and lower halves of the device.

〔Effect of the invention〕

As described above, the present invention allows for the deformation of the casing due to a difference of 1g and 1 degree between the upper and lower halves of the casing, and the spill strip fixed to the casing is approximately 2Y/Hc. Move the spill strip in the direction of displacement of the spill strip so as not to contact the tip of the spill strip as described above.
Since it is eccentric in the vertical direction passing through the center of the rotor blade, it is possible to reliably prevent contact between the spill strip and the tip of the rotor blade and damage caused by contact, thereby improving the integrity and reliability of the rotor blade of an axial flow turbine. It has the effect of increasing sex.

[Brief explanation of drawings]

Figure 1 is a vertical sectional view showing the overall structure of a steam turbine to explain the structure of rotor blade tip seals in a conventional axial flow turbine; Figure 2 is an enlarged view of part A in Figure 1; Figure 3 is an explanatory diagram for explaining the gap between the rotor blade tip and the spill strip, and Figure 4 shows an embodiment of the present invention.
A) is an explanatory diagram showing the state where the spill strip is eccentric in the vertical direction with respect to the rotor blade, A) is an explanatory diagram showing the shape and eccentricity of the spill strip shown in No. 41, Figure 5 e fhj, In order to obtain the maximum displacement t3'4 of the turbine casing (t), the longitudinal and transverse cross-sectional views of the thick-walled cylinder that serve as the basis for the initial amount. An explanatory diagram, FIG. 7 is a graph showing the eccentric path of the spill strip set according to the output of various turbines, and FIG. 8 is a graph showing another embodiment of the spill strip. 58 (5)
FIG. 9 is an explanatory diagram showing the shape and eccentricity tIji of the spill strip shown in FIG. (I3) is the shape of the IJ tube and (fi)t>, %
It is an explanatory diagram showing i. 1... External casing, 2... Rotor, 3... Moving blade, 4... Nozzle diaphragm, 5... Inner casing, 6°... Tenon, 7... Shushiudo, 8, 1
0, 11, 12... Spill strip. Representative patent attorney Kensuke Chika (and 1 other person) Figure 2 Figure 3 Figure 4 Figure 5 Figure 8 Figure 9

Claims (1)

[Claims] 1. A spill strip is provided around the outer periphery of the tip of the rotor blade installed on the rotating shaft with a required gap, and when the spill strip is displaced, it comes into contact with the tip of the rotor blade. Avoid this spill in the direction of displacement of the strip above the spill)
An axial flow turbine characterized in that the IJ knob is eccentric with respect to the rotor blade. 2. The axial flow turbine 03 according to claim 1, wherein the eccentric direction of the spill strip is downward on a vertical line passing through the center of the rotor blade. The axial flow turbine 04 according to claim 1 is above a vertical line passing through the center of the spill strip, and the vertical eccentricity of the spill strip is 0.
The axial flow turbine according to any one of claims 1 to 3, characterized in that the length is set to 15 m to 1.0 m.