JPH07174001A - Moving blade chip clearance controller - Google Patents

Abstract

PURPOSE:To minimize a moving blade chip clearance at a steady operation time, and prevent occurrence of contact between the and a casing inner surface facing thereto even at transient times during start and stop. CONSTITUTION:A moving blade chip clearance controller is provided with a segment 6 which is provided on a casing 4 opposing to a moving blade 2 and movable in the radial direction of the casing 4, a transmission piece 7 to adjust the radial position by transmitting external force to the segment 6, a driving pressure source P to apply pressure to the transmission piece 7, and a transmission piece elastic body 9 to regulate the positions of the segment 6 and the transmission piece 7 by means of balance with operating pressure of the driving pressure source P so that chip clearance may be controlled in the radial position of the segment 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotor blade tip clearance controller for controlling a clearance between a rotor blade which is a rotating portion and a stationary portion which faces the rotor blade in a fluid machine such as an axial compressor or an axial turbine. .

[0002]

2. Description of the Related Art In a fluid machine such as an axial flow compressor and an axial flow turbine having rotary vanes, the rotary vanes, that is, the moving blades, do not come into contact with a stationary portion such as a casing during rotation and are not damaged. As described above, the tip gap is provided between the blade tip and the corresponding inner surface of the casing.

However, this tip gap causes a fluid leakage loss, resulting in deterioration of performance. This tendency is remarkable in the case of the axial compressor, and the degree of performance deterioration may be 1 to 2%. As a result, the degree of efficiency reduction of the entire gas turbine plant is about twice that, which is very remarkable.

Further, it is known that the increase of the tip clearance greatly affects the overall characteristics of the fluid machine such as the decrease of the pressure rise in other paragraphs and the decrease of the surge margin. Therefore, it is necessary to make the tip clearance as small as possible.

A conventional blade tip clearance control device will be described with reference to FIGS. Generally, the passage portion of the axial compressor is constituted by the rotor 1, the moving blades 2, the stationary blades 3 and the casing 4 as shown in FIG. The tip clearance δ is set at the time of assembly so that the tip of the moving blade 2 and the inner surface of the casing 4 facing it do not come into contact with each other due to the deformation of each part during rotation. .

The details of the tip gap δ are as shown in FIG. That is, the centrifugal force elongation δ ₁ of the rotating portion,
Rotor deflection amount δ ₂ , Rotor lift amount due to bearing oil film formation δ ₃ , Steady thermal expansion difference δ ₄ between rotating and stationary parts, Unsteady expansion difference δ ₅ expected at start and stop, calculation error and machining accuracy And a margin δ ₆ due to In this way, assuming all deformations from startup to rated time,
The tip gap δ is set.

On the other hand, FIG. 6 shows an example in which a wear material 5 is attached to the inner surface of the casing 4 facing the tip of the moving blade 2. Even if the tip of the moving blade 2 comes into contact with the casing 4, the abrasion material 5 wears the abrasion material 5 itself to minimize damage to the moving blade 2. In the case of this conventional example, the set chip gap δ can be made smaller than the above-mentioned value. For example, in the breakdown of the chip gap δ, the margin δ ₆ minutes is removed to set a narrower gap.

However, also in the structure of this conventional example, when the deformation due to the transitional thermal expansion difference occurs more than expected and the tip of the moving blade 2 comes into contact with the casing 4, the wear material 5 is scraped off, resulting in the chip clearance. δ becomes large. Moreover, there is a problem that the once expanded chip gap δ cannot be restored, and performance deterioration cannot be avoided in subsequent operations.

[0009]

By the way, in the breakdown of the tip clearance δ shown in FIG. 7, the elongation δ of the centrifugal force of the rotating part is shown.
₁ , the rotor deflection amount δ ₂ , the rotor floating amount δ ₃ due to the formation of bearing oil film, and the steady thermal expansion difference δ ₄ between the rotating part and the stationary part, for example, during continuous operation of a gas turbine used for power generation under a normal load. That is, it should be considered when assuming a steady state.

However, the unsteady elongation difference δ ₅ that is expected at the time of starting and stopping, that is, the required chip clearance due to the unsteady difference in thermal expansion due to the difference in heat transfer coefficient between the rotor 1 and the surface of the casing 4, is There is no need to consider during continuous operation under load, that is, in steady state.

In other words, the conventional chip gap setting is
During continuous operation under normal load where the highest performance as a fluid machine is expected, it includes the chip clearance amount that is required only when starting and stopping, and as a result, it has more chip clearance than necessary. . Further, it is very difficult to predict the above-mentioned unsteady thermal expansion difference, and the unsteady thermal expansion difference δ ₅ is set to be considerably larger than the actual value because reliability is prioritized.

On the other hand, even in the structure in which the wear member 5 shown in FIG. 6 is mounted, as described above, the deformation due to the transient thermal expansion difference more than expected occurs, and the tip of the moving blade 2 comes into contact with the casing 4. In this case, the wear material 5 is scraped off, and as a result, the chip gap δ becomes large. Moreover, the tip gap δ once expanded
However, there is a problem in that it is necessary to disassemble the wear material 5 once in order to correct it, and the wear material 5 must be replaced, which is troublesome.

Further, it is a well-known fact that contact between the rotating part and the stationary part, that is, rubbing is likely to occur during a sudden change in the operating state such as an emergency stop.

The present invention has been made in consideration of the above circumstances, and minimizes the blade tip clearance during steady operation, and also allows the contact between the blade and the corresponding inner surface of the casing during a transition at the time of start / stop. It is an object of the present invention to provide a blade tip clearance control device that is less likely to generate.

[0015]

In order to solve the above-mentioned problems, the first aspect of the present invention is to provide a segment, which is provided in a casing facing a rotor blade and is movable in a radial direction thereof,
A transmission top for transmitting an external force to the segment to adjust its radial position, a drive pressure source for applying pressure to the transmission top, and the positions of the segment and the transmission top to balance the operating pressure of the drive pressure source. And a transmission top elastic body defined by the above, and the tip gap is controlled at the radial position of the segment.

A second aspect of the present invention is characterized in that the operating pressure of the driving pressure source according to the first aspect uses either the discharge air pressure of the compressor or the bleed air pressure from the middle stage.

Further, a third aspect of the present invention is characterized in that the segment according to the first aspect is fitted into a dovetail groove formed in the casing.

According to a fourth aspect of the present invention, an initial clearance is provided between the segment according to the first or third aspect of the invention and the transmission frame, in which the blade tip clearance is maintained at a value that avoids rubbing during a transition at the time of starting and stopping. It is characterized by having.

[0019]

In the present invention having the above-mentioned structure, the tip gap is kept in the initial state until the operating pressure of the driving pressure source reaches a certain value, and when the operating pressure exceeds a certain value, the transmission top comes into contact with the segment, As the operating pressure rises, the segment is moved to the rotor blade side to reduce the tip clearance. As a result, the reliability at the time of starting and stopping is improved and the performance at the rated time is improved.

[0020]

Embodiments of the present invention will be described below with reference to the drawings.

1 and 2 are sectional views showing an embodiment of a moving blade tip clearance controller according to the present invention. It should be noted that the same or corresponding portions as those of the conventional configuration will be described using the same reference numerals as those in FIG.

This embodiment shows an example applied to an axial flow compressor. FIG. 1 shows the positional relationship of the constituent elements in the range where the unsteady elongation difference between the start-up and the start-up of the compressor is large, and FIG. The positional relationship of the components in the vicinity of the rated point where the unsteady expansion difference of the compressor becomes small is shown. In these figures, some paragraphs are extracted and shown.

As shown in FIG. 1, a rotor 1 has a rotor blade 2 fixed thereto, and a casing 4 facing the rotor blade 2 has a groove 4a formed in its radial direction. A segment 6 is fitted in the dovetail groove 4a so as to be movable in the radial direction of the casing 4. A segment elastic body 10 is interposed between the segment 6 and the dovetail groove 4a to position the segment 6 in the radial direction.

The radial position of the segment 6 is adjusted by the external force from the transmission top 7, and the external force of the transmission top 7 is applied with the discharge air pressure of the compressor, which is a driving pressure source, through the pressure pipe 8. . The positions of the transmission top 7 and the segment 6 are defined by the balance between the operating pressure P from the compressor and the elastic force of the transmission top elastic body 9.

In this embodiment, the operating pressure P is the discharge air pressure of the compressor, and the tip clearance δ _T at the time of transition includes the unsteady expansion difference δ ₅ as described in the prior art, and the reliability of the fluid machine is improved. A setting value with a margin giving priority to δ ≦ δ _T , while the tip clearance δ _S at the time of rating is a setting value not considering the unsteady elongation difference δ ₅ in the breakdown shown in FIG. δ ₅ ≧
_Let δ _S.

The segment elastic body 10 presses the segment 6 in the radial direction when the external force from the transmission top 7 is not applied, and maintains the gap between the segment 6 and the tip of the moving blade 2 at the tip gap δ _T during the transition. Is an elastic body having a spring constant K ₁ sufficient for the above, and having a deformation amount such that the gap between the segment 6 and the tip of the moving blade 2 at the rated point operating pressure P ₀ becomes the tip gap δ _S at the rated time.

The transmission top elastic body 9 has a transmission top operating pressure P.
_{At 1,} the spring constant K ₂ is deformed by the clearance CL. That is, when the pressure receiving area of the transmission top 7 is A ₁ ,

[Formula 1] P ₁ · A ₁ = K ₂ · CL.

Further, between these,

## EQU2 ## δ _T −δ _S = X

[Formula 3] P ₀ · A ₁ = K ₂ (CL + X) + K ₁ · X There is a relationship, and the transmission top operating pressure P ₁ is set to the pressure value at the point where the unsteady elongation difference converges within the allowable range. ing.

Next, the operation of this embodiment will be described.

In the rotor blade tip clearance controller for the axial compressor of this embodiment, the operating pressure P is the compressor discharge pressure,
Since the transmission top operating pressure P ₁ is set to a pressure value at a point where the unsteady expansion difference converges to an allowable range, the unsteady expansion difference between the start of the compressor and the start of the compressor is large, that is, the discharge pressure. When the transmission top operating pressure P _{1 is} lower than the transmission top operating pressure P ₁ , although the compressor discharge pressure deforms the transmission top elastic body 9 as the number of rotations increases and the load increases, the transmission top 7 is pushed down. Since there is a clearance CL between the top 7 and the segment 6, an external force is not applied to the segment 6, and the action of the segment elastic body 10 maintains the tip clearance δ _T during the transition in the initial state.

Further, in the vicinity of the rated point in the range where the unsteady elongation difference is allowable, the compressor discharge pressure is the transmission top operating pressure P ₁
As shown in FIG. 2, the operating pressure P moves the segment 6 to the moving blade 2 side through the transmission top 7, and acts to reduce the chip gap. It becomes δ _S.

The series of operations will be described with reference to FIGS. 3 and 4. In FIG. 3, the horizontal axis shows the rated operating pressure, in this embodiment the operating pressure made dimensionless by the rated point discharge pressure, and the vertical axis shows the tip clearance δ which is the clearance with the tip of the moving blade 2. In FIG. 4, the horizontal axis is the same as in FIG. 3, but the vertical axis shows the movement amount of the transmission top 7.

As shown in FIGS. 3 and 4, the operating pressure P
The transmission top 7 moves by the clearance CL with the increase of. However, during this movement, due to the clearance CL, no external force acts on the segment 6, and as a result, the tip gap δ retains the tip gap δ _T at the transition of the initial state. Further, when the operating pressure P exceeds the transmission top operating pressure P ₁ , the transmission top 7 comes into contact with the segment 6, the segment 6 starts moving to the moving blade 2 side, and the operating pressure P finally reaches the rated point operation. Segment 6 when the pressure reaches P ₀
Moves by δ _T −δ _S, and the chip gap δ is set to the rated chip gap δ _S.

As described above, according to the present embodiment, by maintaining the tip clearance δ at the transient tip clearance δ _T in the range where the unsteady elongation difference is large, the reliability of the fluid machine can be ensured and the steady state can be ensured. In this state, the tip gap δ is set to the minimum required gap, that is, the tip gap δ _S at the time of rating, so that the performance improvement of the rated point of the fluid machine can be secured.

Further, at the time of an emergency stop in which the occurrence of rubbing is expected or during the occurrence of surging, the discharge pressure drops,
The abnormality can be promptly detected by the operating pressure P, the tip gap δ can be expanded, and rubbing that causes a serious accident such as damage to the moving blade 2 can be avoided.

Further, since there is a clearance CL between the segment 6 and the transmission top 7, the blade tip clearance can be maintained at a value that avoids rubbing during a transition at the time of starting and stopping. Further, by directly introducing the discharge pressure of the compressor itself to the operating pressure P by piping, a complicated control mechanism by an electric system is unnecessary, and the structure can be simplified.

In the above embodiment, the operating pressure P quickly detects the abnormality due to the drop in the discharge pressure even during the emergency stop or the surging. Therefore, the extracted air pressure from the middle stage is used as the operating pressure P. However, the same effect as that of the above-described embodiment can be obtained.

Further, in the above-mentioned embodiment, the case where the present invention is applied to a single paragraph is shown, but it is naturally applicable to a plurality of paragraphs. Further, by disposing a wear material in the segment 6 for adjusting the blade tip clearance, the reliability can be further improved.

[0039]

As described above, according to the blade tip clearance control device of the present invention, the segment provided in the casing facing the blade and movable in the radial direction thereof,
The balance between the transmission top that transfers external force to this segment and adjusts its radial position, the drive pressure source that applies pressure to this transmission top, and the position of the segment and the transmission top by the operating pressure of the drive pressure source Equipped with a transmission top elastic body, by controlling the tip gap at the radial position of the segment, the tip gap is kept relatively large in the range where the unsteady elongation difference is large, thereby ensuring the reliability of the fluid machine. In addition, by setting the tip clearance to the minimum necessary in the steady state, the performance improvement of the rated point of the fluid machine is ensured.

Also, at the time of an emergency stop in which rubbing is expected to occur or when surging occurs, the operating pressure decreases,
By quickly detecting the abnormality and widening the tip clearance, it is possible to avoid the occurrence of rubbing that may cause a serious accident such as damage to the moving blade.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of a moving blade tip clearance control device according to the present invention.

FIG. 2 is a cross-sectional view showing a state where the chip gap is small in FIG.

FIG. 3 is a diagram showing a relationship between a rated operating pressure and a tip gap.

FIG. 4 is a diagram showing a relationship between a rated operating pressure and a movement amount of a transmission top.

FIG. 5 is a partial sectional view showing a passage portion of a general axial flow compressor.

FIG. 6 is a sectional view showing a conventional blade tip clearance control device.

FIG. 7 is a diagram showing a breakdown of a set tip gap.

[Explanation of symbols]

 1 rotor 2 rotor blade 4 casing 6 segment 7 transmission top 8 pressure tube 9 transmission top elastic body 10 segment elastic body CL clearance P operating pressure δ tip gap

Claims (4)

[Claims] 1. A segment, which is provided in a casing facing a rotor blade and is movable in a radial direction thereof, a transmission top for transmitting an external force to the segment to adjust its radial position, and a drive for applying a pressure to the transmission top. A pressure source, and a transmission top elastic body that defines the position of the segment and the transmission top by the operating pressure of the drive pressure source, and controlling the tip clearance at the radial position of the segment. Characteristic blade tip clearance control device. 2. The moving blade tip clearance control device according to claim 1, wherein the operating pressure of the driving pressure source is either the discharge air pressure of the compressor or the bleed air pressure from the middle stage. . 3. The blade tip clearance control device according to claim 1, wherein the segment is fitted in a dovetail groove formed in the casing. 4. The initial clearance between the segment and the transmission frame has an initial clearance that holds a blade tip clearance at a value that avoids rubbing during a transition at the time of start and stop. A blade tip clearance control device as described.