WO2017013922A1

WO2017013922A1 - Non-contact annular seal and rotary machine provided with same

Info

Publication number: WO2017013922A1
Application number: PCT/JP2016/063530
Authority: WO
Inventors: 裕輔渡邊
Original assignee: 株式会社荏原製作所
Priority date: 2015-07-17
Filing date: 2016-05-02
Publication date: 2017-01-26
Also published as: CN107850221B; CN107850221A; JP6772136B2; JPWO2017013922A1

Abstract

The increase in the flow rate of a fluid passing through a seal interior is minimized, while the effect of minimizing unstable vibration caused by circumferential swirl flow about an axis of rotation is improved. According to the present invention, a non-contact annular seal is provided which has a rotational solid provided to a rotating section of a rotary machine, and a fixed solid provided to a fixed section of the rotary machine, and which is configured so as to seal a fluid flowing through a gap between the rotational solid and the fixed solid. The non-contact annular seal has a screw groove provided to the surface of the rotational solid and/or the surface of the fixed solid that form the gap, a lead angle of the screw groove relative to a plane intersecting the axial direction of the rotational solid is established, and the lead angle of the screw groove on a seal inlet side is greater than the lead angle of the screw groove on a seal outlet side.

Description

Non-contact annular seal and rotating machine equipped with the same

The present invention relates to a non-contact annular seal and a rotary machine including the same, and in particular, in a rotary machine that handles an incompressible fluid, the amount of fluid leakage between an impeller and a casing and a casing is reduced and vibration is reduced. The present invention relates to a non-contact annular seal that exhibits stable shaft seal characteristics and a rotary machine including the same.

Rotating machines that transfer liquids (hereinafter referred to as “pumps”) are widely used in plants or facilities for power generation, chemical processes, sewerage, waterworks, and the like. The pump has a casing and a rotating shaft on which an impeller is mounted. A rotating shaft is arrange | positioned inside a casing and is rotatably supported by a bearing. The liquid sucked from the suction port of the casing is pressurized by the rotation of the impeller and discharged from the discharge port of the casing. That is, in the flow path inside the pump, a high pressure region and a low pressure region are formed, and fluid flows from the high pressure region to the low pressure region. Here, in a slight gap between the casing (fixed portion) and the rotating shaft (rotating portion), if the fluid moves (leaks) from the high pressure region to the low pressure region through this gap, the pump efficiency decreases. For this reason, the clearance gap between a casing and a rotating shaft is sealed by the non-contact annular seal. Thereby, it is suppressed that the pressurized liquid leaks to the low pressure side.

For example, in the typical multi-stage centrifugal pump shown in FIG. 1 (cited from JIS Handbook Pump 1st Edition, page 74), the non-contacting annular seal is used in the part circled in the figure. That is, it is used between the inlet part of the impeller, between the front stage impeller and the rear stage impeller, between the last stage impeller outlet part and the low pressure side (pump inlet pressure), and the like. In particular, since the differential pressure is large between the impeller outlet and the low pressure side, and fluid leakage is large, the fluid leakage at this portion has a great influence on the pump performance. For this reason, non-contact annular seals of various structures that can reduce the amount of fluid leakage are known.

The smooth seal is known as the most basic non-contact annular seal. The smooth seal is a seal formed by arranging double cylinders having smooth surfaces. In order to reduce the leakage amount of a non-contact annular seal such as a smooth seal, it is effective to reduce the radial gap between the rotating side and the stationary side of the non-contact annular seal. However, due to practical problems such as vibration and deflection of the rotating shaft, the radial gap cannot be made extremely small. For this reason, a non-contact annular seal that reduces the leakage amount without reducing the radial gap is required. As such a non-contact annular seal, a parallel groove seal, a damper seal, a thread groove seal and the like are known. Hereinafter, an example of a conventional non-contact annular seal will be described.

FIG. 18 is a partial sectional view of a conventional parallel groove seal. In FIG. 18, the fixed body 131 is shown in a sectional view, and the rotating shaft 121 is shown in a side view. The parallel groove seal 111 includes a rotating shaft 121 that is a rotating body having a smooth outer peripheral surface, and a fixed body 131 in which a plurality of concentric grooves 141 are provided on a surface facing the rotating shaft 121. This parallel groove seal 111 has energy loss due to vortices generated when the fluid flowing through the gap between the rotating shaft 121 and the fixed body 131 passes through the groove 141, pressure loss caused by sudden expansion and contraction of the flow path, and the like. Thus, the leakage amount (movement amount) of the fluid can be reduced.

19 and 20 are partial cross-sectional views of a conventional damper seal. FIG. 19 shows a damper seal that employs a honeycomb pattern as a damper structure. In FIG. 19, the fixed body 132 is shown in a sectional view, and the rotating shaft 122 is shown in a side view. The damper seal 112 includes a rotating shaft 122 that is a rotating body having a smooth outer peripheral surface, and a fixed body 132 having a plurality of concave portions 142 provided on a surface facing the rotating shaft 122. In the illustrated example, a hexagonal honeycomb pattern is used as the recess 142. The damper seal 112 can reduce the amount of fluid leakage due to the pressure loss of the fluid generated when the fluid flowing through the gap between the rotating shaft 122 and the fixed body 132 flows through the recess 142.

FIG. 20 shows a damper seal that employs a hole pattern as a damper structure. In FIG. 20, the fixed body 133 is shown in a sectional view, and the rotating shaft 123 is shown in a side view. The damper seal 113 includes a rotating shaft 123 that is a rotating body having a smooth outer peripheral surface, and a fixed body 133 that is provided with a plurality of recesses 143 on a surface facing the rotating shaft 123. In the illustrated example, a circular concave hole pattern is used as the concave portion 143. The damper seal 113 can reduce the amount of fluid leakage due to the pressure loss of the fluid that occurs when the fluid flowing through the gap between the rotating shaft 123 and the fixed body 133 flows through the recess 143.

FIG. 21 is a partial cross-sectional view of a conventional thread groove seal. In FIG. 21, the fixed body 134 is shown in a sectional view, and the rotating shaft 124 is shown in a side view. The thread groove seal 114 includes a cylindrical fixed body 134 having a smooth inner peripheral surface, and a rotating shaft 124 having a thread groove 144 formed on a surface facing the fixed body 134. When the rotating shaft 124 rotates, the thread groove seal 114 has an effect of pushing back the fluid to the high pressure side by a pumping effect according to the rotation direction, and reducing the amount of leakage. The thread groove 144 is a continuous groove from the seal inlet side (high pressure side) to the seal outlet side (low pressure side). When the pressure difference between the inlet side and the outlet side of the thread groove seal 114 is large, the leakage flow due to the pressure difference becomes large. Therefore, it is often possible to reduce the leakage amount by reducing the lead angle.

A non-contact annular seal used in a fluid machine such as a turbo molecular pump is disclosed in Japanese Utility Model Publication No. 62-98798 (Patent Document 1).

Japanese Utility Model Publication No. 62-98798

By the way, in the non-contact annular seal, the fluid passing through the inside of the seal swirls around the outer periphery of the rotating shaft, so that unstable vibration (also referred to as self-excited vibration) occurs in the rotating shaft, and an abnormal vibration state occurs in the rotating shaft. May occur. The difficulty of generating this unstable vibration is one of the important characteristics of the non-contact annular seal. It has been found that this unstable vibration is more likely to occur as the swirl flow in the circumferential direction of the rotation shaft inside the seal increases.

In the case of a thread groove seal, it is possible to reduce the swirling flow of the fluid inside the seal accompanying the rotation of the rotating shaft by providing an appropriate groove in the fixed body. For this reason, the thread groove seal which has a thread groove in a fixed body is often used as a means to suppress unstable vibration. It has been found that the effect of suppressing unstable vibration due to the screw groove provided in the fixed body is more remarkable as the lead angle of the screw groove is larger. However, as described above, when the lead angle of the thread groove is increased, the amount of leakage often increases, and it can be said that there is a trade-off relationship between the effect of suppressing unstable vibration and the effect of reducing the amount of leakage. Therefore, it has been difficult to achieve both a reduction in leakage and suppression of unstable vibration at a high level.

The present invention has been made in view of the above-described conventional problems, and one of its purposes is to improve the effect of suppressing unstable vibration caused by the swirling flow in the circumferential direction of the rotating shaft, while improving the effect of suppressing the inside of the seal. Is to suppress an increase in the amount of fluid leaking through the fluid.

Another object of the present invention is to reduce the leakage of the fluid pressurized by the impeller to the low pressure side in a rotary machine that rotates the rotating shaft to which the impeller is attached and transfers the fluid. It is to suppress the unstable vibration caused by the fluid passing through the inside of the seal while increasing the efficiency.

As a result of intensive studies on the above problems, the present inventors have obtained the following knowledge. That is, in a thread groove seal with a relatively large lead angle of the thread groove, the action of suppressing unstable vibration on the high pressure side (seal inlet side) is more effective than the action of suppressing unstable vibration on the low pressure side (seal outlet side). Was found to be large. It has also been found that a thread groove seal with a relatively small lead angle of the thread groove has an effect of reducing substantially the same amount of leakage between the low pressure side and the high pressure side.

The present invention was made based on the above findings. According to an aspect of the present invention, the rotating body includes a rotating body provided in a rotating portion of the rotating machine and a fixing body provided in a fixing portion of the rotating machine, and flows through a gap between the rotating body and the fixing body. A non-contact annular seal configured to seal fluid is provided. The non-contact annular seal has a thread groove provided on at least one of the surface of the rotating body and the surface of the fixed body forming the gap, and the thread groove is a plane orthogonal to the axial direction of the rotating body. The lead angle of the screw groove with respect to the seal is defined, and the lead angle of the screw groove on the seal inlet side is larger than the lead angle of the screw groove on the seal outlet side. According to this, since the lead angle of the thread groove is relatively increased on the high pressure side (seal inlet side) that has a large effect of suppressing the destabilizing vibration, the effect of suppressing the destabilizing vibration is improved. be able to. In addition, since the lead angle of the thread groove is relatively small on the low pressure side (seal outlet side), an increase in the amount of fluid leaking through the seal can be suppressed. Therefore, according to one aspect of the present invention, it is possible to achieve both the effect of suppressing unstable vibration of the non-contact annular seal and high shaft sealing performance.

According to another aspect of the present invention, in one form of the non-contact annular seal, the thread groove has a lead angle of the thread groove that gradually decreases from the seal inlet side toward the seal outlet side. It is formed. According to this, the non-contact annular seal can be manufactured by joining together a plurality of non-contact annular seals having thread grooves with different lead angles. For this reason, the said non-contact annular seal can be easily manufactured, for example using the non-contact annular seal which exists conventionally.

According to another aspect of the present invention, in the one form of the non-contact annular seal, the thread groove has a lead angle of the thread groove that continuously decreases from the seal inlet side toward the seal outlet side. It is formed. According to this, the lead angle of the thread groove can be finely set to an appropriate angle according to the axial position. As a result, the effect of suppressing the unstable vibration of the non-contact annular seal and the shaft sealing performance can be further improved.

According to another embodiment of the present invention, in one embodiment of the non-contact annular seal, the depth of the thread groove on the seal inlet side is greater than the depth of the thread groove on the seal outlet side. When the lead angle of a thread groove having a predetermined number of threads in the non-contact annular seal is increased, the width of the thread groove has to be increased, and the sum of the cross-sectional areas of the thread grooves is increased. Further, when the lead angle of the thread groove having a predetermined width is increased, the number of strips must be increased, and the sum total of the cross-sectional areas of the thread grooves is increased. When the total sum of the cross-sectional areas of the thread grooves increases, the fluid easily flows between the seals. According to one aspect of the present invention, the total cross-sectional area of the thread grooves of the non-contact annular seal can be reduced, so that the amount of fluid leaking between the seals can be further reduced.

According to another embodiment of the present invention, in one embodiment of the non-contact annular seal, the thread groove is formed at least on the surface of the fixed body. By forming the thread groove at least on the surface of the fixed body, it is possible to suppress an increase in leakage while improving the effect of suppressing unstable vibration. By the way, when the screw groove is provided also in the rotating body of the non-contact annular seal, the pumping effect of pushing back the fluid to the high pressure side by the rotation of the rotating body increases. On the other hand, there is a possibility that fluid around the rotating body swirls due to the rotation of the rotating body, and unstable vibration is promoted. Here, if the thread groove is formed on the surface of the fixed body, even if the thread groove is formed on the surface of the rotating body, the swirling of the fluid caused by the rotation of the rotating body is caused by the thread groove on the surface of the fixed body. Can be suppressed. In this case, the amount of fluid leakage can be further reduced by the pumping effect of the thread groove formed on the surface of the rotating body. Therefore, when the thread groove is formed on both the fixed body and the rotating body, the amount of leakage can be further suppressed while suppressing unstable vibration.

According to another aspect of the present invention, a rotating machine is provided. The rotating machine includes an electric motor, a main shaft connected to the electric motor and configured to be rotatable, an impeller that is fitted to the main shaft and configured to be rotatable together with the main shaft, and a casing that houses the impeller. And a bearing attached to the casing and rotatably supporting the main shaft, the main shaft has a rotating portion, the casing has a fixing portion, and the rotating portion and the fixing portion are It has a non-contact annular seal.

According to one aspect of the present invention, it is possible to suppress an increase in the amount of leakage of fluid passing through the inside of the seal while improving the effect of suppressing unstable vibration due to the swirling flow in the circumferential direction of the rotating shaft.

Further, according to one aspect of the present invention, in a rotary machine that rotates a rotating shaft to which an impeller is attached to transfer a fluid, the fluid boosted by the impeller is prevented from leaking to the low pressure side, thereby improving pump efficiency. The unstable vibration caused by the fluid passing through the inside of the seal can be suppressed while increasing.

Sectional drawing of the high pressure pump which can apply the non-contact annular seal which concerns on this embodiment is shown. FIG. 2 is an enlarged sectional view of a first stage impeller of the high pressure pump shown in FIG. 1. It is a fragmentary sectional view which shows the non-contact annular seal of this embodiment applicable to the non-contact annular seal shown in FIG. It is a figure which shows the other example of the cross-sectional shape of the screw groove formed in a fixing body. It is a figure which shows the other example of the cross-sectional shape of the screw groove formed in a fixing body. It is a figure which shows the other example of the cross-sectional shape of the screw groove formed in a fixing body. It is sectional drawing at the time of cut | disconnecting by the plane containing the central axis of the fixing body shown in FIG. It is sectional drawing which shows the other example of the fixing body used for the non-contact annular seal shown in FIG. It is sectional drawing which shows the further another example of the fixing body used for the non-contact annular seal shown in FIG. It is sectional drawing which shows the further another example of the fixing body used for the non-contact annular seal shown in FIG. It is sectional drawing which shows the further another example of the fixing body used for the non-contact annular seal shown in FIG. It is sectional drawing which shows the further another example of the fixing body used for the non-contact annular seal shown in FIG. It is sectional drawing which shows the further another example of the fixing body used for the non-contact annular seal shown in FIG. It is sectional drawing which shows the further another example of the fixing body used for the non-contact annular seal shown in FIG. It is a fragmentary sectional view which shows the non-contact annular seal of other embodiment applicable to the non-contact annular seal shown in FIG. It is a fragmentary sectional view which shows the non-contact annular seal of other embodiment applicable to the non-contact annular seal shown in FIG. It is a fragmentary sectional view which shows the non-contact annular seal of other embodiment applicable to the non-contact annular seal shown in FIG. It is a fragmentary sectional view which shows the non-contact annular seal of other embodiment applicable to the non-contact annular seal shown in FIG. It is a graph which shows the result of an evaluation test. It is a fragmentary sectional view of the conventional parallel groove seal. It is a fragmentary sectional view of the conventional damper seal. It is a fragmentary sectional view of the conventional damper seal. It is a fragmentary sectional view of the conventional thread groove seal.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the drawings described below, the same or corresponding components are denoted by the same reference numerals, and redundant description is omitted. In the embodiment described below, a high-pressure pump is described as an example of the rotating machine of the present invention.

FIG. 1 shows a cross-sectional view of a high-pressure pump (multistage centrifugal pump) to which a non-contact annular seal according to this embodiment can be applied. The high-pressure pump 1 includes a main shaft 11 that is connected to an electric motor (not shown) and rotates,

impellers

21a, 21b, and 21c fitted to the main shaft 11, a casing 31 that houses the

impellers

21a, 21b, and 21c, and a casing. And

bearings

45a and 45b attached to 31. The

bearings

45a and 45b support the main shaft 11 to be rotatable. An electric motor (not shown) for rotationally driving the high-pressure pump 1 is connected to the main shaft 11 via a coupling 13 fitted to the left end of the main shaft 11.

The casing 31 has a suction port 33 for sucking incompressible fluid such as water (hereinafter simply referred to as fluid) from the outside, and a discharge port 37 for discharging the sucked fluid. The first stage impeller 21 a fitted to the main shaft 11 rotates as the main shaft 11 rotates, and sucks fluid into the casing 31 from the suction port 33. The fluid sucked and pressurized by the first stage impeller 21a passes through the first flow path 35a and reaches the second stage impeller 21b. The fluid pressurized by the second stage impeller 21b passes through the second flow path 35b and reaches the third stage impeller 21c. The fluid is further pressurized by the third stage impeller 21c, discharged from the discharge port 37, and transferred through a pipe (not shown). That is, the fluid is pressurized by the first stage impeller 21a, the second stage impeller 21b, and the third stage impeller 21c.

In the fluid, a pressure difference is generated between the suction side and the discharge side of each

impeller

21a, 21b, 21c. That is, the suction side is the low pressure side and the discharge side is the high pressure side. When this pressure difference occurs, a part of the fluid on the high pressure side leaks to the low pressure side through a slight gap. The non-contact annular seal of this embodiment reduces the leakage. In the high-pressure pump 1 shown in FIG. 1, the non-contact annular seal of this embodiment is provided at a site surrounded by a circle. Since the high-pressure pump 1 shown in FIG. 1 is a multi-stage centrifugal pump, the fluid pressure is higher than that of a single-stage centrifugal pump, and the amount of fluid leakage inevitably increases. If the amount of leakage is large, the pump efficiency decreases.

FIG. 2 is an enlarged cross-sectional view of the first stage impeller 21a of the high-pressure pump 1 shown in FIG. As illustrated, the first stage impeller 21a includes a suction port 23 for sucking fluid and a discharge port 25 for discharging fluid. Here, the pressure of the fluid is low on the suction port 23 side and high on the discharge port 25 side. That is, the suction port 23 is a low pressure part 36, and the discharge port 25 is a high pressure part 38. Here, the fluid leaking portion in the high-pressure pump 1 is mainly a facing portion X between the outer peripheral surface of the suction port 23 and the casing 31a, and a facing portion Y between the outer peripheral surface of the rear surface of the impeller 21a and the casing 31b. Non-contact annular seals 41 and 43 according to the present embodiment are provided in the gaps formed in the facing portions X and Y, respectively.

The non-contact annular seals 41 and 43 include rotating bodies 41a and 43a provided on the impeller 21a that is a rotating part of the high-pressure pump 1, and fixed bodies 41b and 43b provided on the

casings

31a and 31b that are fixed parts. . In the illustrated example, the rotating bodies 41a and 43a are provided as members different from the impeller 21a, but the rotating bodies 41a and 43a may be formed integrally with the impeller 21a. Similarly, although the fixed bodies 41b and 43b are provided as members different from the

casings

31a and 31b in the illustrated example, the fixed bodies 41b and 43b may be formed integrally with the

casings

31a and 31b.

FIG. 3 is a partial cross-sectional view showing the non-contact annular seal of this embodiment applicable to the non-contact annular seals 41 and 43 shown in FIG. In FIG. 3, the fixed body 71 is shown in a sectional view, and the rotating body 61 is shown in a side view.

As shown in the figure, the non-contact annular seal 51 of the present embodiment is provided on the rotating body 61 provided on the impeller 21a which is the rotating part shown in FIG. 2 and the

casings

31a and 31b which are the fixing parts shown in FIG. And a fixed body 71 provided. The rotating body 61 is configured to be rotatable together with the impeller 21a. The rotating body 61 rotates in a predetermined direction around the central axis 151. The center axis 151 coincides with the axis of the main shaft 11 shown in FIGS. 1 and 2, for example.

Further, the fixed body 71 includes a screw groove 81 formed in a spiral shape on the inner surface thereof. That is, the non-contact annular seal 51 of this embodiment is a thread groove seal. The fixed body 71 is formed in a substantially cylindrical shape. The rotating body 61 is a substantially cylindrical member having an outer diameter smaller than the inner diameter of the fixed body 71. The rotating body 61 is disposed inside the fixed body 71 so as to have a predetermined gap with respect to the inner surface of the fixed body 71.

When the non-contact annular seal 51 is applied to the high pressure pump 1 shown in FIG. 1, the fluid passes through the gap between the fixed body 71 and the rotating body 61 from the high pressure side 155 (seal inlet side) to the low pressure side 156 (seal outlet). Side), that is, in the direction of arrow A in the figure.

As shown in FIG. 3, the cross-sectional shape of the thread groove 81 formed in the fixed body 71 is substantially rectangular. However, the present invention is not limited to this, and the cross-sectional shape of the thread groove 81 may be substantially triangular as shown in FIG. 4A. Moreover, as shown to FIG. 4B, the cross-sectional shape of the thread groove 81 may be a substantially U shape. Furthermore, as shown in FIG. 4C, the cross-sectional shape of the thread groove 81 may be a substantially semicircular shape. As the cross-sectional shape of the thread groove 81, any cross-sectional shape other than the cross-sectional shapes shown in FIGS. 3 and 4A-4C can be adopted.

As described above, the present inventors have obtained the following knowledge through intensive studies. That is, in a thread groove seal with a relatively large lead angle of the thread groove, the action of suppressing unstable vibration on the high pressure side (seal inlet side) is more effective than the action of suppressing unstable vibration on the low pressure side (seal outlet side). Was found to be large. It has also been found that a thread groove seal with a relatively small lead angle of the thread groove has an effect of reducing substantially the same amount of leakage between the low pressure side and the high pressure side.

Therefore, in the non-contact annular seal 51 according to the present embodiment shown in FIG. 3, the lead angle of the screw groove 81 on the high pressure side 155 (seal inlet side) is the same as that of the screw groove 81 on the low pressure side 156 (seal outlet side). A screw groove 81 is formed so as to be larger than the lead angle. That is, in the non-contact annular seal 51 according to the present embodiment, unstable vibration is efficiently suppressed by the screw groove 81 on the high pressure side, and the amount of leakage is reduced by the screw groove 81 on the low pressure side. Therefore, the non-contact annular seal 51 according to the present embodiment can achieve both the effect of suppressing unstable vibration and high shaft seal performance.

FIG. 5 is a cross-sectional view of the fixed body 71 shown in FIG. 3 cut along a plane including the central axis 151. As shown in the drawing, the fixed body 71 includes a screw groove 81A located on the high pressure side 155 (seal inlet side), a screw groove 81C located on the low pressure side 156 (seal outlet side), and a screw groove 81A and a screw groove 81C. And a screw groove 81B positioned therebetween. Here, the screw groove 81 is referred to as a general term for the

entire screw grooves

81A, 81B, and 81C. The

thread grooves

81A, 81B, and 81C define lead angles θ1A, θ1B, and θ1C with respect to a plane orthogonal to the axial direction of the rotating body 61 (see FIG. 3) (the axial direction of the central axis 151), respectively. The

screw grooves

81A, 81B, 81C have widths W1A, W1B, W1C, respectively. Here, the widths W1A, W1B, and W1C indicate the shortest distances in the width direction from arbitrary points on the side surfaces of the

thread grooves

81A, 81B, and 81C. The depths of the

thread grooves

81A, 81B, 81C are all the same.

The screw groove 81 has

boundary portions

161 and 162 where the lead angle of the screw groove 81 changes. Specifically, the lead angle θ1A of the screw groove 81A changes to the lead angle θ1B of the screw groove 81B at the boundary portion 161. Further, the lead angle θ1B of the screw groove 81B changes to the lead angle θ1C of the screw groove 81C at the boundary portion 162. Since the

boundary portions

161 and 162 do not have a substantial width, the thread groove 81 is continuously formed on the surface of the fixed body 71. In the present embodiment, the

boundary portions

161 and 162 are formed in parallel with a plane orthogonal to the central axis 151. However, the

boundary portions

161 and 162 are not limited to being formed in a planar shape or a straight shape, and may have any shape. Further, as will be described later, the number of the

boundary portions

161 and 162 is not limited to two, and may be one or three or more (see FIGS. 10 and 11).

Here, the lead angle θ1A is larger than the lead angle θ1B. Further, the lead angle θ1B is larger than the lead angle θ1C. Accordingly, the lead angle of the thread groove 81 is formed so as to decrease stepwise from the high pressure side 155 toward the low pressure side 156. That is, since the lead angle θ1A of the thread groove 81A is relatively large on the high-pressure side 155 that has a large effect of suppressing the destabilizing vibration, the effect of suppressing the destabilizing vibration can be improved. Further, on the low-pressure side 156, the lead angle θ1B of the screw groove 81B and the lead angle θ1C of the screw groove 81C are relatively small, so that an increase in the amount of fluid leaking through the non-contact annular seal 51 is suppressed. Can do.

Further, since the thread groove 81 is formed so that its lead angle gradually decreases from the high pressure side 155 toward the low pressure side 156, the thread groove 81 can be easily processed in the fixed body 71. Specifically, the thread groove 81 can be formed by

processing thread grooves

81A, 81B, 81C having a certain width on the inner peripheral surface of the fixed body 71, respectively. Alternatively, for example, a fixed body having a screw groove 81A, a fixed body having a screw groove 81B, and a fixed body having a screw groove 81C are manufactured, and the fixed body 71 is easily manufactured by combining these fixed bodies. Can do.

The number of thread grooves 81A, the number of thread grooves 81B, and the number of thread grooves 81C are the same. When the number of threads is constant, the width of the thread groove 81 decreases as the lead angle decreases. For this reason, the width W1A of the screw groove 81A on the high pressure side 155 from the boundary portion 161 is larger than the width W1B of the screw groove 81B on the low pressure side 156 from the boundary portion 161. Further, the width W1B of the screw groove 81B on the high pressure side 155 from the boundary portion 162 is larger than the width W1C of the screw groove 81C on the low pressure side 156 from the boundary portion 162. That is, the width of the thread groove 81 is formed so as to decrease stepwise from the high pressure side 155 toward the low pressure side 156. As will be described later, the number of threads 81A, the number of threads 81B, and the number of threads 81C may be different (see FIG. 7). Further, as will be described later, the width W1A, the width W1B, and the width W1C may be the same size (see FIG. 7).

As shown in the drawing, the cross-sectional area of the thread groove 81A on the high-pressure side 155 is the same as the cross-sectional area of the thread groove 81B on the low-pressure side 156 at the boundary 161. Similarly, in the boundary portion 162, the cross-sectional area of the screw groove 81B on the high-pressure side 155 is the same as the cross-sectional area of the screw groove 81C on the low-pressure side 156. As will be described later, the cross-sectional area of the screw groove 81 on the high-pressure side 155 in the

boundary portions

161 and 162 may be different from the cross-sectional area of the screw groove 81 on the low-pressure side 156 (see FIG. 7).

Also, as shown in the drawing, the screw groove 81 on the high pressure side 155 is formed continuously with the screw groove 81 on the low pressure side 156 at the

boundary portions

161 and 162. In other words, the cross section of the thread groove 81 on the high pressure side 155 coincides with the cross section of the thread groove 81 on the low pressure side 156 at the

boundary portions

161 and 162. Specifically, at the boundary 161, the cross section of the screw groove 81A on the high pressure side 155 coincides with the cross section of the screw groove 81B on the low pressure side 156. Further, in the boundary portion 162, the cross section of the thread groove 81B on the high pressure side 155 coincides with the cross section of the thread groove 81C on the low pressure side 156. Thereby, it can suppress that the pumping effect is inhibited by the screw groove 81 in the

boundary parts

161 and 162. As will be described later, in the

boundary portions

161 and 162, the screw groove 81 on the high pressure side 155 may be formed so as not to be continuous with the screw groove 81 on the low pressure side 156 (see FIGS. 6 and 7).

As described above, the non-contact annular seal 51 shown in FIG. 3 has the fixed body 71 in which the lead angle of the screw groove 81 on the high pressure side 155 is larger than the lead angle of the screw groove 81 on the low pressure side 156. This non-contact annular seal 51 can also be provided with other fixed bodies as described below, for example.

FIG. 6 is a cross-sectional view showing another example of a fixed body used in the non-contact annular seal 51 shown in FIG. 6 shows a cross-sectional view of the fixed body when cut along a plane including the central axis 151 shown in FIG. The fixed body 72 shown in FIG. 6 differs from the fixed body 71 shown in FIG. 5 in that the thread groove 81 is discontinuous at the

boundary portions

161 and 162. The other parts of the fixed body 72 are the same as the fixed body 71 shown in FIG.

As shown in the drawing, the cross section of the screw groove 81 on the high pressure side 155 is formed so as not to coincide with the cross section of the screw groove 81 on the low pressure side 156 at the

boundary portions

161 and 162. Specifically, in the boundary portion 161, the cross section of the thread groove 81A on the high pressure side 155 does not coincide with the cross section of the thread groove 81B on the low pressure side 156. Further, at the boundary 162, the cross section of the screw groove 81B on the high pressure side 155 does not coincide with the cross section of the screw groove 81C on the low pressure side 156.

FIG. 7 is a cross-sectional view showing still another example of a fixed body used in the non-contact annular seal 51 shown in FIG. FIG. 7 shows a cross-sectional view of the fixed body when cut along a plane including the central axis 151 shown in FIG. The fixing body 73 shown in FIG. 7 differs from the fixing body 71 shown in FIG. 5 in that the cross-sectional area of the screw groove 81 on the high-pressure side 155 is different from that on the low-pressure side 156. Are different from each other in that the width of the screw groove 81 is constant.
The other parts of the fixed body 73 are the same as the fixed body 71 shown in FIG.

As shown in the figure, at the boundary 161, the cross-sectional area of the thread groove 81A on the high-pressure side 155 is different from the cross-sectional area of the thread groove 81B on the low-pressure side 156. Further, in the boundary portion 162, the cross-sectional area of the screw groove 81B on the high-pressure side 155 is different from the cross-sectional area of the screw groove 81C on the low-pressure side 156. Since the screw groove 81 is formed such that the cross-sectional area of the screw groove 81 changes at the

boundary portions

161 and 162, the number of threads of the screw groove 81 can be changed before and after the

boundary portions

161 and 162. For this reason, the lead angles θ1A, θ1B, and θ1C of the

thread grooves

81A, 81B, and 81C can be set more flexibly.

Also, in the

boundary portions

161 and 162, the cross section of the screw groove 81 on the high pressure side 155 is formed so as not to coincide with the cross section of the screw groove 81 on the low pressure side 156. Specifically, in the boundary portion 161, the cross section of the thread groove 81A on the high pressure side 155 does not coincide with the cross section of the thread groove 81B on the low pressure side 156. Further, at the boundary 162, the cross section of the screw groove 81B on the high pressure side 155 does not coincide with the cross section of the screw groove 81C on the low pressure side 156.

Further, as illustrated, in the fixed body 73, the width W1A of the screw groove 81A on the high-pressure side 155 from the boundary portion 161 is the same as the width W1B of the screw groove 81B on the low-pressure side 156 from the boundary portion 161. Further, the width W1B of the screw groove 81B on the high pressure side 155 from the boundary portion 162 is the same as the width W1C of the screw groove 81C on the low pressure side 156 from the boundary portion 162. As a result, the number of threads 81A, the number of threads 81B, and the number of threads 81C are different. Specifically, the number of threads of the screw groove 81A is larger than the number of threads of the screw groove 81B, and the number of threads of the screw groove 81B is larger than the number of threads of the screw groove 81C.

FIG. 8 is a cross-sectional view showing still another example of a fixed body used in the non-contact annular seal 51 shown in FIG. FIG. 8 shows a cross-sectional view of the fixed body when cut along a plane including the central axis 151 shown in FIG. The fixed body 74 shown in FIG. 8 is different from the fixed body 71 shown in FIG. 5 in that the

boundary portions

161 and 162 have a predetermined width. The other parts of the fixed body 74 are the same as the fixed body 71 shown in FIG.

As shown in FIG. 8, the boundary 161 between the screw groove 81A and the screw groove 81B has a predetermined width. Further, the boundary portion 162 between the screw groove 81B and the screw groove 81C has a predetermined width. In other words, the thread groove 81 is intermittently formed on the surface of the fixed body 74. Thus, even if the thread groove 81 is intermittently formed on the surface of the fixed body 74, the same operation as that of the fixed body 71 shown in FIG.

FIG. 9 is a cross-sectional view showing still another example of a fixed body used in the non-contact annular seal 51 shown in FIG. 9 shows a cross-sectional view of the fixed body when cut along a plane including the central axis 151 shown in FIG. The fixing body 75 shown in FIG. 9 is different from the fixing body 71 shown in FIG. 5 in that the depth of the screw groove 81 is gradually reduced. The other parts of the fixed body 75 are the same as the fixed body 71 shown in FIG.

As shown in the figure, the

thread grooves

81A, 81B, 81C have depths D1A, D1B, D1C, respectively. The depth D1A of the screw groove 81A on the high pressure side 155 from the boundary portion 161 is larger than the depth D1B of the screw groove 81B on the low pressure side 156 from the boundary portion 161. Further, the depth D1B of the screw groove 81B on the high-pressure side 155 from the boundary portion 162 is larger than the depth D1C of the screw groove 81C on the low-pressure side 156 from the boundary portion 162.

Generally, in a non-contact annular seal, when the lead angle of a thread groove having a predetermined number of threads is increased, the width of the thread groove has to be increased, and the sum of the sectional areas of the thread grooves is increased. Further, when the lead angle of the thread groove having a predetermined width is increased, the number of strips is inevitably increased, and the sum of the cross-sectional areas of the thread grooves is increased. When the total sum of the cross-sectional areas of the thread grooves increases, the fluid easily flows between the seals.

As in the fixed body 75 shown in FIG. 9, when the lead angle θ1A of the screw groove 81A is relatively large among the screw grooves 81 having a predetermined number of threads, the width of the screw groove 81A is relatively large, The sum total of the cross-sectional areas of the screw grooves 81 is increased. Therefore, as in the fixed body 75 shown in FIG. 9, the depth of the thread groove 81 is gradually decreased from the high pressure side 155 toward the low pressure side 156, thereby reducing the cross-sectional area of the thread groove 81. The sum can be reduced. Thereby, the leakage amount of the fluid passing between the seals can be further reduced.

7, when the lead angle θ 1 A of the screw groove 81 A is relatively large among the screw grooves 81 having a predetermined width, the number of threads of the screw groove 81 A is relatively Become more. Even in such a case, in order to further reduce the amount of leakage of the fluid passing between the seals, it is effective to form the thread groove 81 so that the depth of the thread groove 81 is gradually reduced. .

FIG. 10 is a cross-sectional view showing still another example of a fixed body used in the non-contact annular seal 51 shown in FIG. 10 shows a cross-sectional view of the fixed body when cut along a plane including the central axis 151 shown in FIG. The fixed body 76 shown in FIG. 10 is different from the fixed body 71 shown in FIG. 5 in that there are many lead angle change positions (boundary portions). The other parts of the fixed body 76 are the same as the fixed body 71 shown in FIG.

As shown in FIG. 10, the fixed body 76 has a boundary portion 163 on the high-pressure side 155 in addition to the

boundary portions

161 and 162. Accordingly, the fixed body 76 has a thread groove 81D on the high-pressure side in addition to the

thread grooves

81A, 81B, 81C. The lead angle θ1D of the screw groove 81D is larger than the lead angle θ1A of the screw groove 81A. As described above, the lead angles of the thread groove 81 change at more positions than the fixed body 71 shown in FIG. 5 due to the

boundary portions

161, 162, and 163. Therefore, the lead angle of the thread groove 81 can be finely set to an appropriate angle according to the axial position. As a result, the effect of suppressing unstable vibration of the non-contact annular seal 51 and the shaft seal performance can be further improved. The number of

boundary portions

161, 162, and 163 is not limited to three, and may be four or more.

FIG. 11 is a cross-sectional view showing still another example of a fixed body used for the non-contact annular seal 51 shown in FIG. 11 shows a cross-sectional view of the fixed body when cut along a plane including the central axis 151 shown in FIG. The fixed body 77 shown in FIG. 11 is different from the fixed body 71 shown in FIG. 5 in that the change position (boundary portion) of the lead angle is small. The other parts of the fixed body 77 are the same as the fixed body 71 shown in FIG.

As shown in FIG. 11, the fixed body 77 has only the boundary portion 161. Therefore, the fixed body 77 does not have the screw groove 81C shown in FIG. 5, but has only the screw groove 81A and the screw groove 81B. Thus, if the fixed body 71 has at least one boundary portion 161 and has at least two screw grooves 81A and screw grooves 81B, the same operation as the fixed body 71 shown in FIG. 5 is achieved. obtain.

FIG. 12 is a cross-sectional view showing still another example of a fixed body used in the non-contact annular seal 51 shown in FIG. 12 shows a cross-sectional view of the fixed body when cut along a plane including the central axis 151 shown in FIG. The fixing body 78 shown in FIG. 12 is different from the fixing body 71 shown in FIG. 5 in that the lead angle θ1 of the screw groove 81 is continuously reduced.

As shown in FIG. 12, the fixing body 78 is formed with a thread groove 81 so that the lead angle θ1 continuously decreases from the high pressure side 155 toward the low pressure side 156. Therefore, the fixed body 78 does not have a boundary portion where the lead angle θ1 changes like the

boundary portions

161 and 162 shown in FIG.

In the fixed body 78 shown in FIG. 12, the number of threads of the thread groove 81 does not change between the high pressure side 155 and the low pressure side 156, and the width of the thread groove 81 is from the high pressure side 155 toward the low pressure side 156. A screw groove 81 is formed so as to be continuously reduced.

12, the lead angle θ 1 of the screw groove 81 changes at more positions than the fixed body 71 shown in FIG. 5. Therefore, the lead angle θ1 of the screw groove 81 can be finely set to an appropriate angle according to the axial position. As a result, the effect of suppressing unstable vibration of the non-contact annular seal 51 and the shaft seal performance can be further improved. It is also possible to incorporate a portion where the lead angle continuously changes like the screw groove 81 shown in FIG. 12 into the fixed body shown in FIGS.

The screw groove 81 described above is described as being provided on the fixed body, but is not limited thereto, and may be provided on the outer peripheral surface of the rotating body 62 shown in FIG. However, the screw groove 81 is preferably formed at least on the surface of the fixed body. By forming the screw groove 81 at least on the surface of the fixed body, it is possible to suppress an increase in leakage while improving the effect of suppressing unstable vibration.

Next, an example of a non-contact annular seal different from the non-contact annular seal 51 shown in FIG. 3 will be described. FIG. 13 is a partial cross-sectional view showing a non-contact annular seal of another embodiment applicable to the non-contact annular seals 41 and 43 shown in FIG. The non-contact annular seal 52 shown in FIG. 13 is different from the non-contact annular seal 51 shown in FIG. The other parts of the non-contact annular seal 52 are the same as the non-contact annular seal 51 shown in FIG. The non-contact annular seal 52 shown in FIG. 13 has one of the fixed

bodies

72, 73, 74, 75, 76, 77, and 78 shown in FIGS. Also good.

The non-contact annular seal 52 has a rotating body 62 having

screw grooves

91A, 91B, 91C formed on the surface thereof. Here, the

screw grooves

91A, 91B, and 91C are collectively referred to as a screw groove 91. The

thread grooves

91A, 91B, 91C have the same shape as the

thread grooves

81A, 81B, 81C formed in the fixed body 71. That is, the thread groove 91 has

boundary portions

164 and 165 where the lead angle of the thread groove 91 changes, and the lead angle of the thread groove 91 is gradually reduced from the high pressure side 155 toward the low pressure side 156. It is formed.

When the screw groove 91 is provided in the rotating body 62 of the non-contact annular seal 52, the pumping effect of pushing back the fluid to the high pressure side 155 by the rotation of the rotating body 62 increases. On the other hand, the rotation of the rotator 62 may cause the fluid around the rotator 62 to swirl and promote unstable vibration. However, since the screw groove 81 is formed on the surface of the fixed body 71, even if the screw groove 91 is formed on the surface of the rotating body 62, the swirling of the fluid generated by the rotation of the rotating body 62 is performed. The screw groove 91 can be suppressed. In this case, the amount of fluid leakage can be further reduced by the pumping effect of the thread groove 91 formed on the surface of the rotating body 62. Accordingly, when the fixed body 71 and the rotating body 62 are formed with the thread grooves 81 and 91 in which the lead angle on the high-pressure side 155 is larger than the lead angle on the low-pressure side 156, leakage is suppressed while suppressing unstable vibration. The amount can be further suppressed.

Further, the non-contact annular seal 52 may have a parallel groove 92 on the surface of the rotating body 62 as shown in FIG. Further, the non-contact annular seal 52 may have a damper seal 93 adopting a honeycomb pattern on the surface of the rotating body 62 as shown in FIG. 15, and on the surface of the rotating body 62 as shown in FIG. You may have the damper seal | sticker 94 which employ | adopted the hole pattern.

Next, the result of the evaluation test of the destabilizing force and the leakage amount in the pump using the non-contact annular seal according to the present embodiment will be described. In this evaluation test, the destabilizing force (unstable vibration) when operating the pump (example) using the non-contact annular seal 51 shown in FIG. 3 and the amount of liquid leaking between the seals (leakage amount) Evaluated. The conditions of the evaluation test are as follows. The minimum inner diameter of the fixed body 71 means the inner diameter of the fixed body 71 at the screw thread position.
Axial length of fixed body 71 / minimum inner diameter of fixed body 71: 0.817
Clearance between inner peripheral surface of fixed body 71 and outer peripheral surface of rotating body 61 / minimum inner diameter of fixed body 71: 0.004
Number of screw threads: 8
Pump rotation speed: 3000rpm
Differential pressure between seal inlet side and seal outlet side: 1.0 MPa

The axial lengths of the thread groove 81A, the thread groove 81B, and the thread groove 81C are the same. That is, the thread groove 81A is formed in the 1/3 region on the high pressure side 155 of the inner peripheral surface of the fixed body 71, the screw groove 81C is formed in the 1/3 region on the low pressure side 156, and the screw groove 81C is formed in the remaining 1/3 intermediate region. A groove 81B is formed. The relationship between the lead angle θ1A of the screw groove 81A of the fixed body 71, the lead angle θ1B of the screw groove 81B, and the lead angle θ1C of the screw groove 81C was as follows.
Lead angle θ1B = 1/2 × Lead angle θ1A = 2 × Lead angle θ1C

As a comparative example, the destabilizing force and the amount of leakage when a pump using a non-contact annular seal in which the lead angle of the thread groove 81 of the non-contact annular seal 51 shown in FIG. Comparative Example 1 is a pump using a non-contact annular seal in which the lead angle of the thread groove 81 is the lead angle θ1B. Comparative Example 2 is a pump using a non-contact annular seal in which the lead angle of the thread groove 81 is the lead angle θ1A. Comparative Example 3 is a pump using a non-contact annular seal in which the lead angle of the thread groove 81 is the lead angle θ1C.

FIG. 17 is a graph showing the results of this evaluation test. In order to compare the results of this evaluation test, the destabilizing force and leakage amount of Comparative Example 2, Comparative Example 3, and Example are shown with the destabilizing force and leakage amount of Comparative Example 1 being 100%.

As shown in FIG. 17, in the comparative example 2 having a relatively large lead angle θ1A, the destabilizing force is suppressed to 31%, and the unstable vibration is reduced compared to the comparative example 1. The amount has increased to 128%. Further, in Comparative Example 3 having a relatively small lead angle θ1C, the leakage amount is reduced to 92%, and the leakage amount is suppressed as compared with Comparative Example 1, but the destabilizing force is 200%. It can be seen that it has increased.

On the other hand, in the embodiment, the destabilizing force is 42% and the leakage amount is 100%. In other words, in the example, it is understood that the increase in the amount of fluid leaking through the seal can be suppressed while the unstable vibration is effectively suppressed.

As mentioned above, although embodiment of this invention was described, embodiment of the invention mentioned above is for making an understanding of this invention easy, and does not limit this invention. The present invention can be changed and improved without departing from the gist thereof, and the present invention includes the equivalents thereof. In addition, any combination or omission of each component described in the claims and the specification is possible within a range where at least a part of the above-described problems can be solved or a range where at least a part of the effect can be achieved. is there.

DESCRIPTION OF SYMBOLS 1 High pressure pump 155 High pressure side 156 Low pressure side 161,162,163,164

Boundary part

61,62

Rotating body

71,72,73,74,75,76,77,78

Fixed body

51,52 Non-contact

annular seal

81,81A , 81B, 81C, 81D, 91, 91A Thread groove θ1, θ1A, θ1B, θ1C, θ1D Lead angle W1A, W1B, W1C Width D1A, D1B, D1C Depth 11

Spindle

21a, 21b,

21c Impeller

31, 31,

31b Casing

45a, 45b Bearing

Claims

A rotating body provided in a rotating portion of the rotating machine; and a fixed body provided in a fixing portion of the rotating machine, configured to seal a fluid flowing through a gap between the rotating body and the fixed body. A non-contact annular seal,
A screw groove provided on at least one of the surface of the rotating body and the surface of the fixed body forming the gap;
The thread groove defines a lead angle of the thread groove with respect to a plane perpendicular to the axial direction of the rotating body;
The non-contact annular seal wherein the lead angle of the thread groove on the seal inlet side is larger than the lead angle of the thread groove on the seal outlet side.
The non-contact annular seal according to claim 1, wherein
The thread groove is a non-contact annular seal formed such that a lead angle of the thread groove is gradually reduced from a seal inlet side toward a seal outlet side.
The non-contact annular seal according to claim 1, wherein
The thread groove is a non-contact annular seal formed such that the lead angle of the thread groove continuously decreases from the seal inlet side toward the seal outlet side.
The non-contact annular seal according to any one of claims 1 to 3,
The non-contact annular seal, wherein the depth of the thread groove on the seal inlet side is larger than the depth of the thread groove on the seal outlet side.
The non-contact annular seal according to any one of claims 1 to 4,
The thread groove is a non-contact annular seal formed on at least the surface of the fixed body.
An electric motor,
A main shaft connected to the electric motor and configured to be rotatable;
An impeller fitted to the main shaft and configured to be rotatable with the main shaft;
A casing for housing the impeller,
A bearing attached to the casing and rotatably supporting the main shaft;
The main shaft has a rotating part,
The casing has a fixed portion;
The rotating machine and the fixed part are rotating machines having a non-contact annular seal according to any one of claims 1 to 5.