JPH10318184A - Thrust load reducing structure for compressor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thrust load reducing structure for compressor, which can suitably reduce a load exerted to a thrust bearing when a variation in load of the thrust bearing is large during the steady-state operation, starting, stopping or the like, and which can eliminate the necessity of increasing the size of the thrust bearing even though a magnetic bearing, a gas bearing or the like having a relatively small allowable bearing pressure value is used as the thrust bearing. SOLUTION: In this thrust load reducing structure for compressor, a pressure adjusting valve 20 is located in a balance connector line 15, and a controller 21 controls the pressure adjusting valve 20 in accordance with a degree of a thrust load exerted to a thrust bearing 4 for a rotary shaft so as to adjust a differential pressure acting upon a balance piston 11 in order to balance the thrust load exerted to the thrust bearing 4 with a thrust force exerted to the blance piston 11.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure for reducing a thrust load of a compressor, and more particularly, to a structure for reducing a thrust load of a compressor using a magnetic bearing or a gas bearing which can tolerate only a low load as a thrust bearing for a rotary shaft. It is preferable.

[0002]

2. Description of the Related Art FIG. 4 shows a structure for reducing a thrust load in a conventional centrifugal compressor.
Is a rotary shaft connected to a driving machine such as a turbine, 2 is a plurality of impellers coaxially mounted on the rotary shaft 1, and 3 is a rotating body (rotor) including the rotary shaft 1 and a plurality of impellers 2. A housing 4 to be accommodated therein is a thrust bearing (oil-lubricated bearing in FIG. 4) that receives a load in the thrust direction of the rotary shaft 1, and 5 a and 5 b are journal bearings that rotatably support the rotary shaft 1 in the housing 3. , 6a and 6b are sealing members for sealing between the rotating shaft 1 and the housing 3. The above-mentioned housing 3 is provided with a chamber 7 for accommodating a plurality of impellers 2 and a communication passage 8 for communicating the adjacent chambers 7, respectively, and a suction section 9 for supplying air to the impeller 2 and discharging compressed air. Each of the ejection units 10 is provided.

[0003] A balance piston 11 is mounted on the rotating shaft 1 for transmitting a rotational driving force to the impeller 2, and the balance piston 11 is disposed on the discharge portion 10 of the housing 3 and has a pressure receiving surface on one side thereof. It is configured such that the discharge pressure acts on 12a. A port 13 is provided in a housing portion corresponding to the pressure receiving surface 12 b on the other side of the balance piston 11.
Is connected to the suction portion 8 of the housing 3 to form a balance connector line 15 composed of the port 13 and the conduit 14. Thus, it supplied to the impeller 2 through with ejection to the pressure receiving surface 12a of the one side the pressure P _d is acted its other pressure receiving surface 12b side of the balance connector line 15 of the balance piston 11 as a suction pressure P _S is configured so that, thereby, the direction of the thrust load is the differential pressure between the discharge pressure P _d and the suction pressure P _S acting on the balance piston 11 acting thrust force of the rotating shaft 1 (from the impeller 2 to the rotary shaft 1 is configured to be allowed occur as opposite direction of the force) f _b, thrust load acting on the thrust bearing 4 of the rotary shaft 1 is reduced by the thrust force and.

Here, the action of reducing the thrust load will be specifically described as follows. First, the thrust load F that acts on the rotary shaft 1 from the impeller 2 is a sum of the load f _i applied from the n of the impeller 2, each rotary shaft 1 (the load indicated by the leftward arrow in FIG. 4), the following Equation (1)

[0005]

(Equation 1)

On the other hand, the thrust force f _b composed of the differential pressure acting on the balance piston is generated in a direction exactly opposite to the thrust load F, so that the thrust load F and the thrust force f _b
Will cancel each other out. As a result, the rotating shaft 1
Is the magnitude of the thrust load F ′ acting on the following equation (2).

[0007]

(Equation 2)

Accordingly, the thrust load F acting on the rotating shaft 1 as a reaction force of the impeller 2 is offset by the magnitude of the thrust force f _b acting on the rotating shaft 1 via the balance piston 11 to a small value. Reduced. Thus, the thrust force (the thrust load F ′ having the size represented by the equation (2)) that is large enough that the thrust load F and the thrust force f _b cannot be balanced is applied to the thrust bearing 4 described above. I try to support it. By the way, when an oil lubricated bearing is used as the thrust bearing 4, a maximum of 30 to 50Kg · f
/ Cm ² can be tolerated.

[0009]

However, the conventional thrust load reducing structure as described above has the following problems. That is, when a magnetic bearing or a gas bearing is used as the thrust bearing 4 by utilizing the conventional structure in which the oil-lubricated bearing is used as the thrust bearing 4, both the magnetic bearing and the gas bearing are compared with the oil-lubricated bearing. However, since the load capacity is about 1/10 or less of the permissible load capacity per unit area, the shape becomes very large in order to obtain the same load capacity, and the rotor size is severely restricted in terms of rotor dynamics. Also, if so assume a balancing unlimitedly and thrust load F generated from the thrust force f _b and the impeller 2 generated on the balance piston 11 during normal operation, it is structured as in the prior art shape However, considering the case of start / stop operation with large load fluctuation, it is very difficult to make the structure of the conventional shape, and the structure becomes larger than that of the oil lubricated bearing.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and an object of the present invention is to provide a thrust bearing in which the thrust bearing is subjected to a large load fluctuation at the time of steady operation and start / stop. A compressor that can appropriately reduce the load acting on the bearing and does not need to make the shape of the thrust bearing large even when a magnetic bearing or gas bearing with a relatively small allowable surface pressure value is used as the thrust bearing. Another object of the present invention is to provide a thrust load reducing structure.

[0011]

In order to achieve the above-mentioned object, according to the present invention, a discharge pressure is applied to one side of a balance piston mounted on a rotary shaft, and a pressure of a balance connector line is applied to the other side. And the suction pressure is supplied as a suction pressure through the balance piston, so that a differential pressure between the discharge pressure and the suction pressure acting on the balance piston is generated as a thrust force of the rotating shaft, and a thrust load acting on a thrust bearing of the rotating shaft is generated. In the thrust load reducing structure of the compressor in which the thrust force is reduced, a control valve is provided in the balance connector line, and the thrust load is applied to the thrust bearing of the rotating shaft according to the magnitude of the thrust load. A controller for controlling the control valve is provided, and the controller controls the control valve to control the balance piston. By adjusting the differential pressure use, and so as to reduce the thrust load acting on the thrust bearing and the thrust force to balance with each other to act as the thrust load on the balance piston which acts on the thrust bearing.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. In FIG. 1,
The same parts as those in FIG. 4 are denoted by the same reference numerals, and redundant description will be omitted.

FIG. 1 shows an embodiment in which the present invention is applied to a structure for reducing a thrust load of a centrifugal compressor. In the thrust load reduction structure of the present embodiment, as shown in FIG. 1, a pressure control valve 20 is provided on the balance connector line 15, and the pressure control valve 20 is controlled based on a control signal from a controller 21. As a result, the pressure on the upstream side of the balance connector line 15, that is, the pressure P _S ′ acting on the pressure receiving surface 12b on the other side of the balance piston 11 (the surface opposite to the pressure receiving surface 12a on one side receiving the discharge pressure) is increased. It is configured to be adjusted.

The controller 21 is configured to receive a signal from a thrust load measuring device 22 such as a load cell for measuring the thrust load on the thrust bearing 4 or a strain gauge. The control signal is supplied from the controller 21 to the pressure control valve 20 based on the signal from the
0 is controlled. Thus, by controlling the pressure control valve 20, the differential pressure acting on the balance piston 11 is adjusted.

Here, the method of setting the diameter (pressure receiving area) of the balance piston 11 will be specifically described as follows. In the following description, the suction pressure at the suction unit 9 is P _S , and the discharge pressure at the discharge unit 10 is P _d
And First, the differential pressure of the rotary shaft 1 from the impeller 2 and acts each thrust load f _i in the left direction (positive direction) in FIG. 1, the balance piston 11 rightward in FIG. 1 (negative) (P _d -P _S ') is acting as a thrust force. Therefore, when the pressure P _S ′, which is the pre-pressure of the pressure control valve 20 during the steady operation of the centrifugal compressor, is set to a value as shown in the following equation (3) by the control of the controller 21, each impeller setting the diameter of the thrust force f _b and balanced piston 11 so as to balance each other to generate the thrust load F and the balance piston 11 consisting of the sum of the load f _i acting respectively on the rotary shaft 1 (pressure receiving area) from 2.

[0016]

(Equation 3)

The reason for setting P _S '= P _S + α (P _d -P _S ) is as follows. α is a coefficient of the degree of opening and closing of the pressure control valve 20. When α = 0, the valve is fully open, and when α = 1, it is fully closed. That is, in the above equation (3), α = 0
Then, P _S '= P _S , and if α = 1, P _S ' = P _d . Then, the opening / closing degree of the pressure control valve 20 is 0 to 1 (in this example, α
= 0.5 to 0.75) so that the thrust bearing 4 is hardly subjected to a thrust load.
_S 'is set.

With such a setting, during normal operation,
Since the and the thrust load F and the thrust force f _b cancel each other, so that the not applied almost thrust load on the thrust bearing 4. That is, at the time of steady operation, the pressure control valve 20 is controlled by the control signal from the controller 21, and the pressure P _S ′ (the pressure acting on the pressure receiving surface 12b on the other side of the balance piston 11) which is the pre-pressure of the pressure control valve 20. Is set to the value shown in the above equation (3), and the steady operation is performed in a state where the thrust bearing 4 hardly receives a thrust load. For this reason, even when the thrust bearing 4 is a magnetic bearing or a gas bearing having a small allowable pressure, it is possible to sufficiently support the load in the thrust direction.

On the other hand, when there is a change in the operating state,
Since the thrust load generated from the impeller 2 changes at the time of stop or the like, the pressure control valve 20 is opened (by increasing the opening degree) by the operation shown in the flowchart of FIG. by _{(P d -P S '= f} b) be increased, it is possible to reduce the thrust load applied to the thrust bearing 4 comprising magnetic bearings or gas bearings, etc. appropriately. Here, the operation of the flowchart shown in FIG. 2 will be briefly described. The magnitude of the thrust load F ₁ measured by the thrust load measuring device 22 such as a load cell or a strain gauge is determined by a thrust bearing such as a magnetic bearing or a gas bearing. allowable thrust force of 4 when either (allowable surface pressure value) is smaller than F _a or equal to this, the controller 2 during the steady operation
A predetermined control signal output from 1 is supplied to the pressure control valve 20, and the same operation as in the steady operation described above is performed. Further, when the magnitude of the thrust load F ₁ is larger than the allowable thrust force F _a is relatively decreased the upstream side of the pressure or leading pressure P _S 'by opening the pressure regulating valve 20 As a result, the differential pressure (P
_d− P _S ′ = f _b ) is set larger. Accordingly, the thrust load F ₁ is reduced accordingly, it is kept less than the allowable thrust force F _a.

Also, in this embodiment, the controller 21 for controlling the control valve sends a signal to a drive control system of a drive device (not shown) such as a steam turbine or a gas turbine to determine whether or not the rotation speed can be increased. Is configured to be input. The operation control based on the information signal is performed according to, for example, an operation procedure shown in a flowchart of FIG. The operation procedure will be briefly described as follows. First, when the rotational speed increase command to the drive motor is inputted, thrust load F ₁ at that time is measured by the thrust load measuring device 22, the thrust load F ₁ is the allowable thrust force F _a of the thrust bearing 4 Comparison Is done. Then, the thrust load F ₁ is permissible thrust force F
If it is confirmed equal small or thereto than _a, a signal indicating that it may be speed-up to the drive control system of the drive motor is inputted, the rotational speed driving device of the target in accordance with this Speed up to On the other hand, if the thrust load F ₁ is larger than the allowable thrust force F _a, the pressure regulating valve opens the pressure regulating valve 20 by a control signal from the controller 21 20
'Differential pressure balance piston 11 by relatively smaller that the (P _d -P _S' before pressure P _S in = f _b) a larger set. Accordingly, the thrust load F ₁ is reduced, and can be suppressed smaller than the allowable thrust force F _a. After this state, the driving machine is accelerated to the required target rotational speed.

According to the above-described configuration, when the centrifugal compressor is in a steady operation, and when the load acting on the thrust bearing 4 is large at the time of starting and stopping, the pressure of the balance connector line 15 and the balance piston are reduced. By adjusting and controlling the acting differential pressure by the pressure control valve 20 and the controller 21, it is possible to balance the thrust load acting on the rotating shaft 1 from each impeller 2 with the thrust force acting on the balance piston 11. As a result, the thrust load applied to the thrust bearing 4 can be appropriately reduced.

Although the embodiment of the present invention has been described above, the present invention is not limited to this embodiment.
Various modifications and changes are possible based on the technical concept of the present invention. For example, in the embodiment described above, the present invention is applied to the thrust load reduction structure of the centrifugal compressor.
It goes without saying that the present invention can be applied to a structure for reducing the thrust load of an axial compressor. Further, the thrust load reducing structure of the present invention can be applied to a blower, a pump, a vacuum pump, and the like having substantially the same configuration as the compressor.

[0023]

As described above, the present invention provides a controller which arranges a control valve on a balance connector line and adjusts and controls the control valve according to the magnitude of a thrust load applied to a thrust bearing of the rotary shaft. A thrust load acting on the thrust bearing and a thrust acting on the balance piston by adjusting the differential pressure (pressure of the balance connector line) acting on the balance piston by controlling the control valve by the controller. Since the thrust load acting on the thrust bearing is reduced by balancing the forces with each other, during steady operation of the compressor, and when the load variation of the thrust is large at the start / stop, the thrust bearing The thrust load applied to the member can be appropriately reduced. Therefore, a magnetic bearing or a gas bearing having a relatively small allowable thrust force (allowable surface pressure value) can be used as the thrust bearing. In addition, it is not necessary to use a magnetic bearing or a gas bearing having a large shape. Even if the conventional structure using the lubricated bearing is applied as it is, it is possible to avoid a problem that the shape of the thrust bearing becomes large.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a structure for reducing a thrust load of a centrifugal compressor according to one embodiment of the present invention.

FIG. 2 is a flowchart showing an operation procedure for performing adjustment control of a pressure adjustment valve when a change occurs in an operation state or when starting or stopping;

FIG. 3 is a flowchart showing an operation procedure when the control system of the driving machine supplies an information signal as to whether or not the rotation speed may be increased.

FIG. 4 is a sectional view showing a structure for reducing a thrust load of a conventional centrifugal compressor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Rotary shaft 2 Impeller 3 Housing 4 Thrust bearing 9 Suction part 10 Discharge part 11 Balance piston 12a, 12b Pressure receiving surface 15 Balance connector line 20 Pressure regulating valve 21 Controller 22 Thrust load measuring device

Claims (1)

[Claims] 1. A structure in which a discharge pressure is applied to one side of a balance piston mounted on a rotating shaft and a pressure on the other side is supplied as suction pressure through a balance connector line, so that the balance piston is supplied to the balance piston. A thrust load reduction of a compressor in which a differential pressure between an acting discharge pressure and a suction pressure is generated as a thrust force of the rotating shaft, and a thrust load acting on a thrust bearing of the rotating shaft is reduced by the thrust force. In the structure, a control valve is disposed on the balance connector line,
Providing a controller that controls the control valve according to the magnitude of the thrust load applied to the thrust bearing of the rotating shaft,
The controller controls the control valve to adjust the differential pressure acting on the balance piston, so that the thrust load acting on the thrust bearing and the thrust force acting on the balance piston are balanced with each other so that the thrust A thrust load reducing structure for a compressor, wherein a thrust load acting on a bearing is reduced.