JPS5974307A - Shaft sealing device of axial-flow rotary machine - Google Patents

Abstract

PURPOSE:To prevent contact of an axis of rotation with a packing by forming contour of a packing inner edge from arcs of the first and the second circles with their centers at different points on a mobile line passing the center of the axis of rotation in the state of repose. CONSTITUTION:The center of rotation of a turbine rotor 11 moves from the center OB during a repose to the center OB' during rotation of ordinary use. For this purpose, contour of an inner edge of a packing 20 is formed from arcs of the first and the second circles with their centers at different points, that is, points OB, OB' on a mobile line C passing the rotational center OB in the state of repose. Thus, through functioning of gaps Cl1 and Cl2 during starting and/or low speed rotation and also functioning of gaps Cl3 and Cl4 in a range of rotation of ordinary use, contact between the rotor and the packing is prevented.

Description

[Detailed description of the invention] [Invention technology field] The present invention relates to a shaft sealing device for an axial flow rotating machine.

[Technical background of the invention and its problems]

BACKGROUND ART In axial flow rotating machines such as steam turbines and gas turbines, a gap of at least a certain level is maintained between the turbine rotor, which is configured as a rotating body, and the casing, for example, in the gland part, so that it does not come into contact with the outside of the stationary part. At first glance, it would seem that this gap should be made larger than a certain level if only issues such as photography that arise when the two ministries come into contact are considered. However, the situation changes completely when considering the problem of internal fluid leakage. In other words, leakage of internal fluid is prevented by a gasket interposed between the turbine rotor and the casing, but in order for this type of device to function effectively, it is necessary to narrow the space between the turbine rotor and the casing as much as possible. , the gap cannot be increased arbitrarily.

Thus, this type of design has the contradictory requirements of widening the radial gap between the turbine rotor and packing in terms of vibration suppression, while narrowing this gap in terms of leakage suppression. There are other difficulties.

Conventionally, in this type of design, the problem that is considered to have the greatest influence is the problem of thermal deformation of the casing. However, recently there is a tendency to think that it is necessary to accurately understand the behavior of the turbine rotor inside the bearing.91 In steam turbines where this point is not considered, vibration accidents that appear to be caused by contact between the turbine rotor and the packing often occur. There is.

[Purpose of the invention]

An object of the present invention is to provide a shaft sealing device for an axial flow rotating machine that can prevent vibration phenomena caused by contact between a turbine rotor and a packing tonnage, and can also keep internal fluid leakage to a minimum. This is what we are trying to provide.

[Summary of the invention]

A feature of the present invention is a shaft sealing device for an axial flow rotating machine in which a packing is arranged to form a seal gap around the circumference of a rotating shaft, in which the inner edge contour of the packing passes through the center of the rotating shaft in a stationary state, and 20 in the direction of rotation of the rotation axis from the horizontal reference line
The polygon is formed by closing first and second circular arcs having their centers of curvature at different points on the line of movement in the range of 70 degrees, and the center of curvature of the first arc is the axis of rotation in a stationary state. The center of curvature of the second circular arc is set at a point eccentrically upward on the movement line within a range of p O,1 to Q,7+im from the center of the rotation axis.

[Embodiments of the invention]

First, the design principle of the present invention will be explained.

An investigation into the behavior of the turbine rotor from steam turbine startup to normal (rated) operation revealed the following points: That is, in FIG. 1, when the steam turbine is at rest, the turbine rotor 1 has its center of rotation at a point OB, which is located downward from the center point OA of the gasket 2, which is indicated by the intersection of the X and Y axes. Here, when the turbine rotor 1 starts rotating counterclockwise, the center of rotation starts moving upward and to the right from point OB, and when the rotation speed reaches the normal rotation speed, the center moves to point OB'. Tsumashi, Patsukin 2
Assuming that is immobile, the turbine rotor 1 will move to the right by ΔX and ΔY as shown in FIG. The present invention sets the gap between the turbine rotor 1 and the packing 2 based on these ΔX and ΔY values. The shape of No. 2 will be explained below.

The present invention relates to the gland section shown in FIG. 3, that is, the turbine rotor 11 in which a gland packing consisting of a packing head 12, a packing holder 13, and a fin 14 is provided on the outer circumference of the turbine rotor 11, and furthermore, the turbine rotor shown in FIG. The present invention is also applied to a structure in which a diaphragm packing 1 consisting of a packing holder 17 and fins 18 is arranged on a nozzle diaphragm 16 adjacent to the rotor 11. (Hereinafter, the gland packing scale and the diaphragm packing p will be collectively referred to as the packing 20.) Therefore, the two circular arcs forming the inner edge contour of the packing 20 are in a stationary state as shown in FIGS. 5 and 6. The centers of curvature are set at different points on the movement line that passes through the center of a certain turbine rotor 11 and is within an angle θ from the horizontal reference line H in the rotational direction of the turbine rotor 11. That is, the first circular arc has a radius I (,) at a point that coincides with the instep of the turbine rotor 11 in a stationary state. The angle θ and the amount of eccentricity E are shown in Fig. 7, which shows the results of investigating ΔX and ΔY values for many steam turbines in practical use. From Fig. 2, it is determined as follows: ΔX−E cosθ,
ΔY=Bsinθ, B= (JX)”+(JY)”
Since the relational expression holds true, if the ΔX and ΔY values are in the range shown by the diagonal lines in FIG. Become a friend.

Since the present invention is configured as described above, the gap (J) and the gap C12 function effectively in the low rotational speed range when starting or stopping the steam turbine to prevent contact between the turbine rotor 11 and the packing 20. On the other hand, in the normal rotation speed range, the gap C13 and the gap CI4 function to prevent contact between the two.During this period, the gap widens somewhat in the other areas mentioned above, but the vertical Since the amount is kept to a minimum, the leakage of internal fluid does not increase so much.

〔Effect of the invention〕

As described above, according to the present invention, contact between the rotating body and the outside of the stationary part is not caused in any state in the low rotational speed range or the normal rotational speed range of the axial flow rotating machine, so vibrations can be prevented. This has the advantage of being able to prevent accidents. Moreover, leakage of internal fluid can be minimized,
There is no need to worry about a decrease in mechanical efficiency.

[Brief explanation of drawings]

Figure 1 is an explanatory diagram of the rotor f method to explain the behavior of the turbine rotor from startup to rated operation of the steam turbine, Figure 2 is a schematic diagram for calculating the motion of the turbine rotor, and Figure 3 , and FIG. 4 show an example of the iM range of the present invention, and FIGS. 5 and 6 are sectional views showing the gland packing part and the diaphragm packing part, and FIG. Show M! FIG. 7 is an explanatory diagram showing the magnitude of the movement value when the center moves due to the increase in rotation of the turbine rotor. 11...Turbine rotor 20...Packing OB...-Turbine rotor center 01 in a stationary state
3'...Turbine rotor center 1-i in normal operating range
・・Horizontal reference line C・・Movement line θ・・Movement angle E・・Eccentricity (7317) Attorney Noriyuki Chika (and 1 other person) Fig. 1 ψ γ Fig. 2 Fig. 3 Fig. 4

Claims (1)

[Claims] In a shaft sealing device for an axial flow rotating machine in which a packing is arranged to form a seal gap around a rotating shaft, the inner edge contour of the packing passes through the center of the rotating shaft in a still state, and is horizontal. 20 in the direction of rotation of the same rotation axis from the reference line
The center of curvature of the first arc is formed by closing a first circular arc and a second circular arc having centers of curvature at different points on the line of movement in the range of 70 degrees to 70 degrees. 1) The center of curvature of the second circular arc is aligned with the center of the rotation axis, and the center of curvature of the second circular arc is 0.1 to 0 from the center of the rotation axis.
．． A shaft sealing device for an axial flow rotating machine, characterized in that the shaft sealing device is set at a point eccentrically upward on the movement line within a range of 7.