JP2013213558A - Pressure balance land type thrust bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the following problems: when pressure of a working fluid is large, it is difficult to apply a gas bearing with a small load capacity to a rotary machine because a large differential pressure occurs in a turbine moving blade or a compressor impeller and an excessive thrust force acts thereon.SOLUTION: In a thrust bearing structure, the pressure in a space formed between a main thrust bearing and a thrust collar is increased by means of a flow path communicating with the space and with a flow path near a moving blade inlet port or upstream of a nozzle, to increase the thrust load capacity by means of fluid pressure.

Description

Technical field on bearings using gas and air to support the rotating shaft of turbomachine

In recent years, environmental issues have become more important and alternative refrigerants and natural refrigerants have been adopted. Although environmental destruction caused by refrigerants such as refrigeration air conditioners is regarded as a problem, lubricating oil that lubricates bearings is difficult to post-process, and lead and similar additives that are already prohibited are mixed in The use of lubricating oil is not preferable from an environmental point of view. Also, it is difficult to treat the lubricating oil mixed with the refrigerant, and it is often discarded together with the refrigerant, which causes environmental pollution.

It is well known that the lubricating oil mixed in the working fluid adheres to the heat transfer surface when it flows into a heat exchanger or the like, thereby impairing heat transfer characteristics. Efficiency is greatly reduced. In addition, when lubricating oil is used at a temperature of 100 ° C. or higher, it may adhere to or carbonize on a high-temperature wall surface to solidify and prevent fluid flow.

Bearings that support the rotating shafts of rotating machinery are generally lubricated and cooled by lubricants such as oil, but they require additional equipment such as lubricant supply pumps, pressure regulators, and coolers. The system is complicated and large. For this reason, a bearing using a fluid used in a system such as a turbomachine as a lubricant is desired, and a gas bearing using a gas as a lubricant has been developed and put into practical use.

Dynamic pressure type gas bearings have been researched and developed for many years and operate without supplying lubricant and without supplying fluid to the bearing. Practical use in bearings for space and aircraft air conditioning systems Has been. The bearing includes a journal bearing that suppresses the radial displacement of the rotating shaft and a thrust bearing that suppresses the axial displacement.
Journal gas bearings mainly include herringbone type and foil type bearings having grooves on the rotating shaft and bearing surface, and foil type is used for high-speed rotating machines. The foil type is roughly classified into a leaf foil type and a bump foil type.
Thrust gas bearings include herringbone type, tapered land type, and foil type.

In the herringbone type and the taper land type, the thrust surface is a fixed wall, and the amount of axial displacement is set by the gap amount. In the foil type, since the foil is deformed, the displacement is defined by the gap amount and the deformation amount, and the thrust force is changed with the deformation of the foil or the like, so that damage at the time of contact is reduced.

Since a gas bearing has a low load capacity, a thrust force reducing method has been devised. In Okamoto et al., JP-A-7-259855, a thrust balance chamber is provided on the inner diameter side of the thrust bearing, and the thrust force on the thrust bearing is reduced by controlling the pressure in the thrust balance chamber. There are drawbacks such as pressure control required, inability to cope with shaft behavior that is not in the control algorithm, sensor installation space required, expensive control storage and sensors.

In JP-A-8-296584 and JP-A-10-318184, the thrust force is suppressed to a predetermined force or less by adjusting the pressure on both sides of the balance piston. A space for providing the balance piston is required, the distance between the bearings of the rotating shaft is increased, and the natural frequency of the shaft system is reduced, so that high-speed operation becomes difficult. There are disadvantages such as pressure control is necessary, it is not possible to cope with the behavior of the axis that was not assumed when creating the control algorithm, sensor installation space is required, and the price of the control storage and sensor is high.

Japanese Patent Laid-Open No. 2001-227535 is a foil type thrust gas bearing formed by a plurality of fan-shaped curved plates in which unevenness is formed on a thin plate, and damage at the time of contact is reduced, but the thrust load capacity does not increase, It cannot withstand thrust forces.

JP 7-259855 A JP-A-8-296584 JP 10-318184 A JP2001-227535

In order to increase the thrust load capacity of the dynamic pressure type gas bearing, it is necessary to increase the outer diameter of the thrust bearing and the thrust collar, which increases windage loss and raises the ambient temperature. It is necessary to insert. Further, the loss increases. Further, when the outer diameter of the thrust collar is increased, the peripheral speed increases, and the centrifugal stress acting on the thrust collar increases, so that it is difficult to maintain reliability and reduce costs.

In order to increase the load capacity of the thrust bearing, a balance piston is provided. However, if a balance piston is provided, the space in the axial direction is increased. As the space increases, the length of the rotating shaft increases, the natural frequency of the shaft system decreases, and operation at high speed becomes difficult. In addition, it is necessary to adjust the pressure on both sides of the balance piston, which has the disadvantage of requiring expensive control devices and sensors.

A sensor required for adjusting the pressure of the balance piston requires a predetermined space and wiring for taking out a signal from the sensor. This increases the space, that is, the size and the number of man-hours, and causes an increase in cost.

Since thrust gas bearings have a small thrust load capacity, a disc-shaped balance piston is provided separately from the thrust bearing thrust collar to suppress the increase in the outer diameter of the thrust collar, but the balance piston and thrust collar are separate. Wind rotation increases, and the temperature in the space rises. In order to suppress this temperature rise, it is necessary to introduce a cooling gas into both.

A thrust bearing composed of a main thrust bearing, an anti-thrust bearing and a spacer provided therebetween, and a thrust collar installed therein, are formed between the inner and outer banks of the main thrust bearing and the thrust collar. The thrust collar is formed by connecting the space to the high-pressure part in the system with the conduction channel, and the circumferential cavity formed in the outer periphery of the thrust collar and the low-pressure part in the system are connected with the conduction channel. Differential pressure acts on both sides of the cylinder, and both the thrust bearing and balance piston function.

The main thrust bearing and the anti-thrust bearing are formed as a plurality of thrust bearing patterns inside the inner circumferential bank portion and the outer circumferential bank portion, and one thrust bearing pattern has one radial deep groove and one radial deep groove. It is composed of a plurality of lands extending in the circumferential direction from the direction edge, and the radial deep groove and the outer peripheral surface or side surface of the thrust bearing are electrically connected by a conduction flow path. A thrust force is generated by rotation, and the movement of the rotating shaft is suppressed.

  By arranging a plurality of the thrust bearing patterns between the inner circumferential bank portion and the outer circumferential bank portion, fluctuations in the circumferential pressure are suppressed.

The radial movement of the rotary shaft 500 installed in the center of the casing 900 is regulated by a journal bearing (not shown), and the axial movement is the main thrust that moves the thrust collar 400 fixed to the rotary shaft 500. It is regulated by regulating with bearing 100 and anti-thrust bearing 200.

Hereinafter, the force acting on the thrust collar 400 will be described by dividing it into a differential pressure caused by the pressure difference and a thrust force caused by the wedge effect of the bearing. In addition, a force acting on the rotating shaft from other than the bearing is referred to as an axial force.

The gas that has flowed from the radial deep groove 120 through the insertion hole 131 and the air supply hole 130 is pressurized by the deep land 115 and the shallow land 110 by rotation and pushes the thrust collar 400. This pushing force (thrust force) increases as the rotational speed increases, but in the case of a compressor or turbine operating in a high-pressure fluid, the axial force acting on the compressor impeller and turbine blades is increased. When the load capacity of the thrust bearing is exceeded, the thrust collar 400 and the base surface 160 of the main thrust bearing 100 come into contact with each other.

When the rotary shaft 500 moves to the main thrust bearing 100 side, the main thrust bearing 100 and the thrust collar 400 approach each other, and the gap becomes narrow. When the gap becomes narrow, the amount of fluid flowing out from the space formed between the main thrust bearing 100 and the thrust collar 400 decreases, and the pressure increases. As the pressure increases, the differential pressure acting in the direction in which the thrust collar 400 and the main thrust bearing 100 move away increases, and the gap between the main thrust bearing 100 and the thrust collar 400 increases. When the gap increases, the amount of fluid flowing out increases, the pressure decreases, and the gap narrows. Thus, the gap between the main thrust bearing 100 and the thrust collar 400 is automatically adjusted.

When the rotary shaft 500 moves to the anti-thrust bearing 200 side, the anti-thrust bearing 200 and the thrust collar 400 approach each other and the gap becomes narrow. When the gap becomes narrow, the amount of fluid flowing out from the space formed between the anti-thrust bearing 200 and the thrust collar 400 decreases, and the pressure increases. As the pressure increases, the differential pressure acting in the direction in which the thrust collar 400 and the anti-thrust bearing 200 move away increases, and the gap between the anti-thrust bearing 200 and the thrust collar 400 increases. When the gap increases, the amount of fluid flowing out increases, the pressure decreases, and the gap narrows. Thus, the clearance between the anti-thrust bearing 200 and the thrust collar 400 is automatically adjusted.

The relationship between the main thrust bearing 100 and the thrust collar 400 and the anti-thrust bearings 200 and 400 with respect to the movement of the rotary shaft 500 has been described individually. However, if the gap between the main thrust bearing 100 and the thrust collar 400 becomes narrower, the anti-thrust bearing 200 and the thrust collar The gap between the collars 400 has a wide geometric relationship, and the individual relationships described above are inconsistent with each other.

In the case of the first embodiment, the fluid downstream of the nozzle 630 flows into the insertion hole 131 of the main thrust bearing 100 as shown in FIGS. This is offset by the thrust force on the back of the moving blade 600, which is equivalent to 400 areas. At this time, the gap between the anti-thrust bearing 200 and the thrust collar 400 is wide, and the differential pressure acting on the thrust collar 400 on the anti-thrust bearing 200 side is small. The thrust force of the back surface portion of the moving blade 600 that is larger than the outer periphery of the thrust collar 400 is offset by the bearing load capability of the thrust bearing 100.

The fluid flowing out from the outer periphery of the thrust collar 400 and the gap between the main thrust bearing 100 and the anti-thrust bearing 200 enters the circumferential cavity 175 and flows out from the vent hole 271 to the low pressure portion in the system.

In the second embodiment, the high-pressure gas upstream of the nozzle 630 is inserted into the main thrust bearing 100, the pressure on the main thrust bearing 100 side rises, and the thrust load capacity increases.

The gas can be fed into the insertion hole 131 and the insertion hole 231 by piping or pipes provided separately.

Thrust bearing layout Main thrust bearing Spacer 3D Anti-thrust bearing Thrust bearing assembly drawing Conduction flow diagram

The compression or expansion of high-pressure gas such as ammonia, hydrocarbon gas, CO2, or CFC facilitates the application of dynamic pressure gas bearings to compressors and turbines that transfer energy.

The configuration of Example 1 is shown in FIG. The rotating shaft 500, the main thrust bearing 100, and the anti-thrust bearing 200 are housed in the central portion of the bearing casing 950. The anti-thrust bearing 200 is fixed to the bearing casing 950, and the main thrust bearing 100 is fixed to the bearing casing 950 via the spacer 300. The bearing casing 950 is fixed to the casing 900.

A gap is formed between the outer peripheral surfaces of the main thrust bearing 100, the spacer 300, and the anti-thrust bearing 200 and the bearing casing 950.

The rotary shaft 500 is provided with a space shaft portion 510 and an attachment screw portion 520, and a thrust collar 400 and a moving blade 600 are attached with a tension bolt 540 and an attachment screw 530.

A main thrust bearing 100 of Example 1 is shown in FIG. The main thrust bearing 100 of the first embodiment is an example in which six thrust bearing patterns are developed in the circumferential direction. The thrust bearing pattern of the main thrust bearing 100 includes a shallow land 110 and a deep land 115, a radial deep groove 120, an air supply hole 130, an insertion hole 131, an outer peripheral bank portion 140 and an inner peripheral bank portion 150 that form a part of the base surface 160, A circumferential groove 170, a center hole 180, and a contact surface 190 are included. A screw hole 191 is provided on the contact surface 190. A deep land 115 deeply dug in a fan shape with the circumferential edge 122 of the radial deep groove 120 as a starting line, and a shallow land 110 dug shallowly in a form extending the deep land 115 in the circumferential direction are provided.

A three-dimensional view of the spacer of Example 1 is shown in FIG. The spacer 300 is disposed between the main thrust bearing 100 and the anti-thrust bearing 200 to define a gap between the thrust collar 400 and the main thrust bearing 100 and the anti-thrust bearing 200. The spacer side surfaces 330 and 340 are in close contact with the contact surface 190 of the main thrust bearing 100 and the contact surface 290 of the anti-thrust bearing 200, and the screw holes 310 are assembled so as to coincide with the screw holes 191 and 291.

An anti-thrust bearing 200 of Example 1 is shown in FIG. The shape of the anti-thrust bearing 200 is the same as the mirror image of the main thrust bearing 100. Compared to the main thrust bearing 100, the outer diameter of the outer circumferential bank 240 is smaller, the inner diameter of the circumferential groove 270 is smaller, and the vent hole 271 is provided. This is the point. The outer diameter of the outer circumferential bank 240 and the inner diameter of the circumferential groove 270 of the anti-thrust bearing 200 are set by design.

A thrust bearing assembly diagram of Example 1 is shown in FIG. The main thrust bearing 100 and the anti-thrust bearing 200 are assembled via a spacer 300. A thrust collar 400 is housed in a space formed by the spacer 300. The anti-thrust bearing 200 is provided with an air supply hole 230, an insertion hole 231, a vent hole 271, and a screw hole 291, and the spacer 300 is provided with a screw hole 310. The circumferential cavity 175 is a space in which the outer peripheral surface of the thrust collar 400 is an inner cylindrical surface, the main thrust bearing 100 and the anti-thrust bearing 200 are side surfaces, and the inner diameter surface of the spacer 300 is an outer cylindrical surface. The vent hole 271 is electrically connected to the circumferential cavity 175.

FIG. 6 shows the configuration of the second embodiment. The second embodiment includes a scroll surrounding the outer periphery of the nozzle 630 provided on the outer periphery of the rotor blade 600 of the turbine, and a gas guide 620 provided in contact with the nozzle 630. The fluid flowing into the scroll 700 flows in the circumferential direction of the nozzle 630 in the circumferential direction, flows into the nozzle 630, is accelerated, flows into the moving blade 600, drives the moving blade 600, and the rotating shaft 500 rotates. The high-pressure fluid in the scroll 700 passes through the guide flow path 620 and the guide circumferential flow path 622 provided in the gas guide 620, and from the insertion hole 131 drilled inward from the outer peripheral portion of the main thrust 100 to the air supply hole 130. enter.

The gas can be fed into the insertion holes 131 and 231 by piping or pipes provided separately.

In the embodiment, a nozzle with nozzle blades is illustrated, but a vaneless nozzle is also applicable. In the case of a compressor or a fan, the same structure can be applied by replacing the nozzle with a diffuser and the moving blade with an impeller. Similarly, the pump can be applied with the same structure.

The conduction flow path 135 represents a series of flow paths along several flows such as the guide flow path 621, the guide circumferential path 622, the insertion hole 131, the air supply hole 130, and the like.

In both conventional bearings using lubricating oil and gas bearings, when the pressure of the working fluid increases, the thrust force acting on the turbine blades and compressor impeller increases, exceeding the load capacity of the thrust bearing. A piston was provided. By using the thrust bearing of the present invention, the balance piston can be eliminated, the structure is simplified, the length of the rotating shaft is shortened, and the natural frequency is increased. It is thought that it will be adopted by machines.
High-pressure CO2, hydrocarbon gases, ammonia, chlorofluorocarbon, etc. are used in chemical process compressors that use centrifugal compressors and power generation turbines that use geothermal and exhaust heat that employ radial turbines. Since the thrust force is large, it is difficult to adopt a gas bearing having a small load capacity, in addition to the balance piston. The present invention makes it possible to apply a hydrodynamic gas bearing alone to the turbomachine using the high-pressure gas, realizing an oil-free turbomachine, reducing heat exchange efficiency due to lubricating oil and eliminating oil separation, Since the increase in loss due to stirring is suppressed, it contributes greatly to energy and resource saving.

100 main thrust bearings
110 Shallow Land
112 circumferential edge
115 Shenzhen
120 radial deep groove
130 Air supply holes
131 Insertion hole
135 conduction channel; means a series of channels along several flows such as a guide channel, a guide circumferential channel, an insertion hole, and an air supply hole.
140 Outer bank
150 Inner bank
160 base
170 Circumferential groove
175 circumferential cavity
180 center hole
190 Contact
191 Screw hole
200 Anti-thrust bearing
230 Air supply hole or outer peripheral surface
231 insertion hole,
271 Vent
291,310 Screw hole
300 spacer
320 O-ring groove
330, 340 Spacer side
400 Thrust color
500 rotation axis
510 Space shaft
520 Mounting screw
530 mounting screws
540 tension bolt
600 blades
610 Shroud
620 Guide
621 Guide channel
622 Guide Circle
630 nozzle
670 Moving blade rear
700 scroll
710 scroll body
720 flange
730 outlet pipe
900 casing
950 Bearing casing

Claims (7)

The thrust collar is composed of a main thrust bearing, an anti-thrust bearing, a thrust bearing composed of a spacer that holds a space between them, and a thrust collar disposed between the main thrust bearing and the anti-thrust bearing and fixed to the rotary shaft. The outer peripheral bank portion of the main thrust bearing located near the outer edge of the thrust collar that contacts when moving in the rotation axis direction and the inner peripheral bank portion near the inner periphery of the main thrust bearing are the inner and outer periphery, and between the main thrust bearing and the thrust collar. A thrust bearing, characterized in that a conductive passage is provided to be electrically connected to the space formed and the outer peripheral surface or side surface of the main thrust bearing. 2. The thrust bearing according to claim 1, wherein at least one conducting channel is provided to communicate with a space formed between the anti-thrust bearing and the thrust collar and an outer peripheral surface or a side surface of the anti-thrust bearing. 3. The thrust according to claim 1, wherein the outer peripheral surface or the side surface of the anti-thrust bearing is electrically connected by the circumferential cavity formed in the outer periphery of the thrust collar and the air vent, and is not electrically connected to the conduction channel. bearing. 4. The thrust bearing according to claim 1, wherein the insertion hole 131 of the main thrust bearing 100 is electrically connected to any one of the nozzle 630 outlet, the moving blade 600 inlet, and the moving blade rear surface portion 670. . 4. The thrust bearing according to claim 1, wherein the insertion hole 131 of the main thrust bearing 100 is electrically connected to the flow path upstream of the nozzle 630. Claim 1, claim 2, claim 3, claim 4 and claim 5, in the surface of the thrust bearing facing the thrust collar, the deep groove digged radially, the circumferential direction from one circumferential edge of the deep groove A thrust bearing, characterized in that a conduction channel that conducts to an outer peripheral surface or a side surface is provided in a deep groove of a multi-stage land type thrust bearing composed of a deep land extending in the direction and a shallow land following the deep land. In claim 1, claim 2, claim 3, claim 4 and claim 5, in the surface facing the thrust collar of the thrust bearing, deep grooves that are digged radially, and gradually become shallower from the circumferential edge. A thrust bearing comprising a deep groove of a taper land type thrust bearing constituted by a dug land, and a conduction channel that is connected to an outer peripheral surface or a side surface.

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