JP2001214847A - Turbomachinery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide turbomachinery capable of reducing a leakage flow rate at steady operation time and shaft directional thrust without reducing volumetric efficiency. SOLUTION: In this turbomachinery having an impeller for rotating together with a rotary main shaft by being held by the rotary main shaft 1 and a fixed side cover 5 arranged so as to cover this impeller, and being constituted so that the impeller comprises a main plate 2 expanding in a concentric circle shape with the rotary main shaft as the center and plural blades 4 held on a side wall surface of this main plate, and the fixed side cover 5 is adjacently arranged on the main plate 2, and is formed so as to have prescribed clearance 7 between the cover and the main plate, the clearance 7 is provided with an annular clearance part for dividing this clearance into two parts in the radial direction, and a radial directional width of this annular clearance part is formed so as to narrow at shaft directional moving time of the impeller to the fixed cover side.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a turbomachine,
In particular, the present invention relates to a water turbine, a high-speed rotating pump, a blower, and the like used in a large hydroelectric power plant.

[0002]

2. Description of the Related Art A turbo machine of this type, which has been generally employed, includes a rotating spindle, an impeller held by the rotating spindle, and a fixed cover arranged to cover the impeller. Generally, the impeller includes a main plate that extends concentrically around a rotating main shaft, and a plurality of blades held on a side wall surface of the main plate.

[0003] In a turbomachine, for example, a pump or a water wheel, a fluid flows into a back pressure chamber or a side pressure chamber formed between a main plate and a fixed side cover, and has a turning speed due to the rotation of an impeller. This creates a gradient in the radial pressure distribution. An axial thrust acts on the impeller due to the change in the pressure gradient. Therefore, a thrust bearing is generally provided to support the thrust. Therefore, by reducing the thrust caused by the gradient of this pressure distribution, the thrust bearing can be simplified and
The service life can be extended. Further, when excessive thrust is applied, the rotating portion and the fixed portion may come into contact with each other, which may cause damage to the device.

In order to reduce the thrust acting on the impeller in the axial direction, a balancing hole is provided from the back pressure chamber to the inside of the impeller so that the pressure in the back pressure chamber is kept constant. By installing a balance pipe in the draft tube, or by providing a communication pipe connecting the back pressure chamber and the side pressure chamber,
There are known pressure balances.
In addition, a method is also known in which a blade is provided on the back side of the impeller or a radial groove is provided in a fixed portion of the back pressure chamber or the side pressure chamber to control the swirling flow on the back.

[0005]

With a turbomachine formed in this way, that is, a turbomachine that balances pressure with a balancing hole or a balance pipe, it is possible to maintain a certain level of balance and to reduce thrust. Although it is effective, however, there is a lot of leakage flow outside the runner during steady operation, which dislikes that the volumetric efficiency is reduced and the efficiency is reduced. There is a problem that processing is required, which leads to an increase in cost.

[0006] The present invention has been made in view of the above, and an object of the present invention is to reduce the leakage flow rate during steady operation,
It is another object of the present invention to provide a turbomachine of this type capable of reducing axial thrust without lowering volumetric efficiency.

[0007]

That is, the present invention comprises an impeller held by a rotating spindle and rotating with the rotating spindle, and a fixed-side cover arranged to cover the impeller. A main plate that extends concentrically around the rotating main shaft, and a plurality of blades held on a side wall surface of the main plate, and the fixed-side cover is disposed adjacent to the main plate. And a turbo machine formed so as to have a predetermined gap between the main plate and the main plate. In the turbo machine, an annular gap portion that divides the gap into two in the radial direction is provided in the gap, and the annular gap portion in the radial direction is provided. The width is formed so as to be narrow when the impeller is moved in the axial direction toward the fixed cover, so that the intended purpose is achieved.

Further, the present invention comprises a rotating spindle, an impeller held by the rotating spindle and rotating with the rotating spindle, and a fixed-side cover arranged so as to cover the impeller. A main plate extending concentrically around the rotation main shaft, and a plurality of blades held on a side wall surface of the main plate, and the fixed-side cover,
In the turbomachine, which is arranged adjacent to the main plate and is formed so as to have a predetermined gap between the main plate and the main plate, the main plate and the fixed side cover have the gaps formed on the side wall surfaces on the gap side, respectively. An annular projecting ridge that divides into two in the radial direction is provided, and this annular projecting ridge is formed so that the radial gap between the two annular projecting levees becomes narrower when the impeller moves in the axial direction toward the fixed side cover side. It is formed.

Further, in this case, the two annular projecting ridges are formed in a concentric shape around the rotating main shaft, and the radius of the side surface of the two annular projecting ridges on the opposed surface side is kept away from the main plate or the fixed cover. In the axial direction so as to be smaller in accordance with the following. Further, the axial change of the two annular projecting levees is a linear change.

That is, according to the turbo machine formed as described above, the gap, that is, the back pressure chamber is provided with an annular gap portion that divides the back pressure chamber into two in the radial direction, and the annular gap portion is formed in the radial direction. Is formed so as to narrow when the impeller moves in the axial direction to the fixed cover side, so that when the thrust in this direction acts on the impeller, the width in the radial direction is reduced, so that the sealing effect is obtained. And the force in the back pressure chamber increases to push the main plate back to its original position.Therefore, the leakage flow rate during steady operation is small, and the axial thrust is maintained without reducing the volumetric efficiency. Can be reduced.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the illustrated embodiments. Here, the case of a Francis type pump-turbine will be described as an example, but the present invention is not necessarily limited to the pump-turbine, and it is needless to say that the present invention can be applied to a blower, a water-turbine, a pump, and the like.

FIG. 1 is a cross-sectional view of a main part of a Francis type pump-turbine. 1 is a main shaft, 2 is a main plate, 3 is a side plate, 4 is a blade, 5 is a fixed-side upper cover, and 6 is a fixed-side lower cover. The rotating body (impeller) of the pump turbine includes a rotating main shaft 1 serving as a rotating shaft, a main plate 2 and a side plate 3 concentrically extending around the main shaft, and a plurality of plates are provided between the main plate 2 and the side plate 3. Are arranged and configured. In addition, a blower or a small pump may be a semi-open impeller without the side plate 3 in some cases.

Around the impeller, ie, a fixed portion, a fixed-side upper cover 5 is disposed on the main plate side, and a fixed-side lower cover 6 is disposed on the side plate side. Leakage fluid flows into a space 7 (hereinafter, back pressure chamber) between the main plate 5 and the upper cover 5 and a space 8 (hereinafter, side pressure chamber) between the side plate 3 and the lower cover 6.

In order to reduce the amount of the leakage fluid, the back pressure chamber 7 is provided with a seal 9 which is an annular gap portion, so that the back pressure chamber is divided into an inner side and an outer side. Also, on the side of the side pressure chamber 8, a seal 10 as an annular gap portion is provided on the inner diameter side to reduce leakage of fluid. Although either one of these seals 9 and 10 functions, it is needless to say that providing both seals 9 and 10 is more effective.

In the seals 9 and 10 formed by the annular gaps, the leakage flow rate of the fluid can be controlled by the length, width, and number of stages of the gaps, but the influence of the length is considered to be smaller than the width. For this reason, in the present invention, the leakage flow rate by changing the width of the annular gap is controlled. That is,
It is configured as shown enlarged in FIG. That is, the seal 9 is composed of annular projecting ridges 9a and 9b which project from the main plate 2 and the upper cover 5 respectively to the back pressure chamber, and their side walls face each other. It is formed as follows.

That is, the annular projecting ridge 9a is
And the radius R of the side surface on the opposite surface side of the annular projecting bank becomes smaller as the distance from the main plate 2 (the annular projecting bank 9b is the fixed side cover 5) becomes smaller. It is formed in a changed shape. That is, the side wall surface of the annular projecting ridge 9a on one side is formed on an inclined surface, and the side wall surface on the other side is formed so as to oppose this inclined surface.

With such a configuration, when an axial thrust acts, for example, the impeller is moved from the side plate 3 side to the main plate 2.
Side direction (arrow Q direction), the back pressure chamber 7
Since the width of the seal gap 9g becomes small, the sealing effect is increased, and the leakage flow rate flowing on the back surface is reduced. As the leakage flow rate decreases, the swirling direction component of the back flow decreases. Here, the pressure gradient in the radial direction of the back pressure chamber is proportional to the square of the swirl speed of the back flow, and is determined based on the outer peripheral end of the back pressure chamber as a boundary condition. Therefore, the lower the swirl speed, the greater the pressure in the back pressure chamber. Due to the increase in the pressure in the back pressure chamber, the force for pushing the impeller from the main plate 2 to the side plate 3 increases, and as a result, the impeller is pushed back to the original position, that is, the excessive thrust force is eliminated.

Conversely, when the impeller moves in the direction from the main plate 2 to the side plate 3, the width of the seal 9 in the back pressure chamber 7 is increased, thereby reducing the sealing effect and increasing the leakage flow rate flowing through the back surface. As a result, the swirling speed of the back flow increases, and the pressure in the back pressure chamber decreases. For this reason, the impeller is
, The pushing force in the direction toward the side plate 3 decreases, and as a result, it is returned to the original position.

In this case, the control amount changes according to the displacement of the impeller at that time. Further, since the effect can be increased by the number of stages, the effect can be further increased by using not only a single stage but also a plurality of stages. In the case of a plurality of stages, various arrangements such as arranging in a stepwise manner, arranging in parallel, or a mixture thereof are conceivable.

A cylindrical seal having a cylindrical surface shape is often used in ordinary turbomachines. By simply changing the shape, the seal is almost the same as the conventional one without requiring other structures. Since the thrust control can be performed only by performing the machining, the cost is reduced.

In the above description, in forming the annular gap portion, that is, the annular projecting ridges 9a and 9b, the side wall surface of one annular projecting ridge 9a is formed as an inclined surface, and the other side wall surface is formed as an inclined surface. The inclined surface is formed so as to oppose the inclined surface, but this inclined surface is the most effective in that the control amount of the leakage flow rate is easily predicted and the processing is easy, but the shape is various. Would be considered.

FIG. 3 shows an example of the sectional shape of the annular gap portion. FIGS. 3A and 3B show curves such as a paraboloid of revolution and a hyperboloid of revolution. By doing so, the amount of leakage flow control can be changed according to the axial displacement. it can. FIG. 3C shows a plurality of steps in a stepwise manner. FIG. 3D shows a plurality of stages arranged in parallel. Further, FIG. 4 shows an example of the inner peripheral seal shape of the side pressure chamber. By reducing the radius of the seal 10 on the side remote from the side plate 3, the impeller and the upper cover
Processing of the lower cover becomes easy.

According to the present invention, by employing the structure of the above-described embodiment, the following operation works, that is, FIG.
3 shows a pressure distribution simulation diagram of the back pressure chamber or the side pressure chamber. R0 indicates the radius of the outermost peripheral portion of the main plate or the side plate, and R1 indicates the radius of the inner seal portion. Pout indicates the pressure at the outermost peripheral portion, and Pin indicates the pressure at the outer peripheral portion of the seal portion. The flow of the fluid in the back pressure chamber or the side pressure chamber is a swirling flow because the impeller is rotating. For this reason,
The pressure distribution can be represented by a quadratic curve where the outer circumference is higher than the inner circumference. The pressure Pout at the outermost peripheral portion is determined by the specifications of the turbo machine such as the rotation speed and output of the impeller. The pressure Pin on the outer periphery of the seal portion is determined by the magnitude of the sealing effect of the inner seal. When the sealing effect is large, the pressure increases, and when the sealing effect is small, the pressure decreases.

When the pressure distribution in the back pressure chamber is given by the distribution shown in FIG. 5, the thrust force acting in the axial direction is obtained by the area integral of the pressure distribution, and the force acts in the direction from the main plate to the side plate. In the case of a side pressure chamber, on the contrary, it works in the direction from the side plate to the main plate. When a difference occurs in the pressure distribution between the back pressure chamber and the side pressure chamber, excessive thrust occurs.

In other words, in a state where excessive thrust occurs, the pressure balance between the back pressure chamber and the side pressure chamber is lost.
It is necessary to make this pressure distribution similar. For example, when excessive thrust occurs in the direction from the side plate to the main plate, it is necessary to increase the pressure in the back pressure chamber or decrease the pressure in the side pressure chamber. To increase the pressure in the back pressure chamber, strengthen the sealing effect of the inner seal and increase the pressure Pin on the outer periphery of the seal to P '. To decrease the pressure in the side pressure chamber, weaken the sealing effect of the inner seal and increase the pressure Pin on the outer periphery of the seal to P'. '

Conversely, if the sealing position is moved during operation to change the sealing effect from the viewpoint of volumetric efficiency and leakage flow rate, the pressure distribution of the back pressure chamber and the side pressure chamber changes at the same time, The imbalance in pressure in the side pressure chamber suggests that it may cause excessive thrust. In the mechanism for keeping the seal gap constant, the thrust suppression effect does not work at all because the sealing effect is kept constant.

According to the present invention, the excessive axial thrust acts to move the impeller from the side plate 3 to the main plate 2 as described above.
When moving in the direction toward, the width of the seal 9 of the back pressure chamber 7 is reduced, so that the sealing effect is increased, and the leakage flow rate flowing through the back surface can be reduced. When the leakage flow rate is reduced, the swirling direction component of the back flow becomes smaller and is pushed back to the original position.

The effect of the seal 10 of the side pressure chamber 6 is the same, and the direction of the seal 9 of the back pressure chamber 7 is reversed. In other words, when the impeller moves from the side plate 3 toward the main plate 2, the width of the side pressure chamber seal 10 is increased, so that the leakage flow rate flowing through the side pressure chamber 8 increases, and the rotational speed of the leakage flow flowing through the side pressure chamber increases. The pressure in the side pressure chamber decreases, the force acting in the direction from the side plate 3 to the main plate 2 decreases, and as a result, the impeller is pulled back. Also,
When the impeller moves in the direction from the main plate 2 to the side plate 3, the width of the side pressure chamber seal 10 is reduced, so that the leakage flow rate flowing through the side pressure chamber 6 is reduced, and the rotational speed of the leakage flow is reduced, so that the pressure in the side pressure chamber is reduced. Increases, and the force for pushing the impeller from the side plate 3 to the main plate 2 increases, and as a result, the impeller is pushed back.

In response to such an excessive thrust with a slight axial displacement, a drag corresponding to the axial displacement can be generated by itself, and the thrust can be controlled / suppressed by taking self-adjustment. With this, the impeller can be kept at an appropriate position. Since the drag can be changed by the displacement, conventionally, even if a large displacement occurs, such that the rotating part and the fixed part come into contact with each other, it is possible to generate a correspondingly large drag, thereby reducing the possibility of contact. can do.

Therefore, the provision of this structure can be expected to have a sufficient effect in either the back pressure chamber 7 or the side pressure chamber 8, but a greater effect can be expected in the case where both are provided.

In the above-described embodiment, the case where one impeller is provided for the main shaft is described. However, in the case of another stage having a plurality of impellers for one main shaft, the back pressure chamber or the side pressure chamber of each impeller is also used. And an effect corresponding to it can be expected. In addition, the same effect can be expected when the main axis is the vertical axis or the horizontal axis, but in the case of the vertical axis, the direction of thrust acting on the impeller and the direction of gravity may be the same, so it supports its own weight due to gravity. The effect works. Although the working fluid is water in the above-described embodiment, it may be a gas instead of a liquid such as another fluid such as oil or air.

Further, with such a configuration, there is no limitation by the number of rotations of the impeller, and the pressure distribution according to the number of rotations is naturally balanced, so that it can be used for equipment having a high number of rotations. Therefore, when the rotation speed becomes high transiently, an effect depending on the rotation speed can be expected.

[0033]

As described above, according to the present invention, there is provided a turbomachine of this kind capable of reducing the axial flow thrust without lowering the flow rate during steady operation and reducing the volumetric efficiency. Obtainable.

[Brief description of the drawings]

FIG. 1 is a vertical sectional side view showing one embodiment of a turbomachine of the present invention.

FIG. 2 is a longitudinal sectional side view showing an enlarged main part of the turbomachine of the present invention.

FIG. 3 is a longitudinal sectional side view showing an enlarged main part of the turbomachine of the present invention.

FIG. 4 is a longitudinal sectional side view showing an enlarged main part of the turbomachine of the present invention.

FIG. 5 is a thrust characteristic diagram of the turbomachine of the present invention.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 rotating main shaft 2 main plate 3 side plate 4 blade 5 fixed upper cover 6 fixed lower cover 7 back pressure chamber 8
Side pressure chamber, 9: annular gap, 9a, 9b: annular projecting embankment, 10
… An annular gap.

Claims (7)

[Claims] 1. A rotating spindle, an impeller held by the rotating spindle and rotating with the rotating spindle, and a fixed-side cover arranged to cover the impeller, wherein the impeller includes the rotating spindle. A main plate extending concentrically around the center and a plurality of blades held on a side wall surface of the main plate, and the fixed side cover is arranged adjacent to the main plate, and the main plate and In the turbomachine formed so as to have a predetermined gap therebetween, an annular gap portion that divides the gap into two in the radial direction is provided in the gap, and the radial width of the annular gap portion is set to A turbomachine formed so as to be narrowed when the vehicle moves in the axial direction toward the fixed side cover. 2. A blade comprising: a rotating spindle; an impeller held by the rotating spindle and rotating with the rotating spindle; a fixed upper cover and a fixed lower cover arranged to cover the impeller; The vehicle is provided with a main plate and side plates extending concentrically about the rotary main shaft, and a plurality of blades held between the main plates and the side plates, and the fixed upper cover is adjacent to the main plate. Arranged, and is formed so as to have a predetermined gap between the main plate, and the fixed lower cover is disposed adjacent to the side plate,
And a turbo machine formed so as to have a predetermined gap between the side plate and the side plate. In the turbo machine, a gap between the fixed upper cover and the main plate is provided with an annular gap portion that bisects the gap in the radial direction. A turbomachine characterized in that a radial width of an annular gap portion is narrowed when the impeller is moved axially toward the fixed side cover. 3. A blade comprising: a rotating spindle; an impeller held by the rotating spindle and rotating with the rotating spindle; a fixed upper cover and a fixed lower cover arranged to cover the impeller; A vehicle configured to include a main plate extending concentrically around the rotating main shaft and a plurality of blades held on a side plate, wherein the fixed-side cover is arranged adjacent to the main plate, and And a fixed-side lower cover, which is formed to have a predetermined gap between the side plate and the fixed-side lower cover, wherein the fixed-side lower cover is disposed adjacent to the side plate. A turbomachine wherein a circumferential annular gap is formed so that a radial gap between annular projecting ridges is narrowed when the impeller is moved axially to a fixed lower cover side. 4. A rotating spindle, an impeller held by the rotating spindle and rotating with the rotating spindle, and a fixed-side cover arranged to cover the impeller, wherein the impeller includes the rotating spindle. A main plate extending concentrically around the center and a plurality of blades held on a side wall surface of the main plate, and the fixed side cover is arranged adjacent to the main plate, and the main plate and In the turbomachine formed so as to have a predetermined gap between the main plate and the fixed-side upper cover on the gap-side surface, provided with an annular projecting levee that divides the gap into two in the radial direction, When the gap between the main plate and the fixed upper cover is narrowed by the impeller moving in the axial direction, the radial gap width between the two annular projecting ridges is reduced, and the annular projecting ridge is fixed to the main plate. Wide gap between upper covers In this case, the gap in the radial direction between the two annular projecting levees is widened, or the inner peripheral annular clearance between the side plate and the fixed lower cover is moved by the impeller in the axial direction, so that the side plate and the fixed side are fixed. When the gap between the lower covers is narrow, the radial width of the inner circumferential annular clearance is narrower, and when the gap between the side plate and the fixed lower cover is wider, the radial width of the inner circumferential gap is wider. A turbomachine characterized by being formed. 5. A blade comprising: a rotating main shaft; an impeller held by the rotating main shaft and rotating with the rotating main shaft; a fixed upper cover and a fixed lower cover arranged to cover the impeller; The vehicle is configured to include a main plate and side plates extending concentrically about the rotating main shaft, and a plurality of blades held between the main plate and the side plates, and the fixed-side upper cover is provided on the main plate. The fixed lower cover is arranged adjacent to the main plate and has a predetermined gap therebetween, and the fixed lower cover is arranged adjacent to the side plate and has a predetermined gap between the side plate and the main plate. In the turbomachine formed as described above, the annular projecting ridge is provided on the side of the fixed side upper cover and the main plate and on the side of the gap between the fixed side lower cover and the side plate when the gap is narrowed. Radius between Turbomachine being characterized in that formed as gap width direction is narrowed. 6. The two annular projecting ridges are formed concentrically around the rotating main shaft, and the radius of the side surface of the two annular projecting ridges on the facing surface side decreases as the distance from the main plate or the fixed cover increases. 6. The turbomachine according to claim 3, wherein the turbomachine is changed in the axial direction as described above. 7. The turbomachine according to claim 6, wherein the change in the axial direction of the two annular protrusions is a linear change.