JPH0720399Y2 - Turbo compressor thrust force adjustment mechanism - Google Patents

Description

[Detailed Description of the Invention] [Industrial field of application] The present invention effectively improves the start-up characteristics at the time of starting of a turbo compressor used for a dynamic pressure gas bearing,
The present invention relates to a thrust force adjusting mechanism for a turbo compressor.

[Prior Art] In a turbo compressor, since a rotor rotates at an extremely high speed, a dynamic pressure gas bearing, which is one of non-contact type bearings, is used as an effective bearing with less friction.

[Problems to be Solved by the Invention] However, a problem with turbo compressors that use dynamic pressure self-gas bearings is that their start-up characteristics are poor at the start. As is well known, a dynamic pressure gas bearing is one in which a gas film is effectively formed between the rotor and the bearing surface due to the high speed rotation of the rotor to generate a load capacity. Therefore, since the rotor is stationary at the time of starting, the gas film is not yet formed, and the rotor makes solid contact with the bearing surface,
The friction coefficient is large. Then, in this state, for example, when high-pressure (starting) gas is introduced from the compressor side, the magnitude of the pressure distribution applied to the compressor side and the turbine side is different, and this is applied to the rotor in the axial direction due to the differential pressure on both sides of the blade. Thrust force will be generated.

However, at the time of starting the turbo compressor, as mentioned above, the rotor is in solid contact with its bearing surface, so if a thrust force is applied in this state, a very large rotational resistance will be generated in the rotor, which will be easy. The rotation speed cannot be increased. Further, the PV value becomes high, which causes the disadvantage that the wear of the bearing surface increases.

The present invention focuses on such a problem and reduces the imbalance of the thrust force generated in the rotor at the time of starting the turbo compressor, thereby facilitating the formation of a gas film between the bearing surface and the start characteristics. Intended to improve.

[Means for Solving the Problems] In order to achieve such an object, the present invention provides a seal that seals a rotor, which couples a turbine and a compressor, in a housing through a minute gap and makes the gap airtight. In the turbo compressor, wherein the rotor is supported by the housing by a dynamic pressure gas bearing that forms a film of fluid existing in the gap by utilizing relative rotation between the rotor and the housing, The diameter near the turbine is changed in a stepwise manner to form a step that forms a pressure receiving surface in the thrust direction perpendicular to the rotor axis, and faces the housing from the inner diameter side to the outer diameter side of the step. The gap is configured to be closed by a seal provided on the inner diameter side and a seal provided on the outer diameter side, and the pressure receiving surface in the thrust direction is exposed. A pressure introducing path for introducing a pressure against an thrust force applied to the rotor from an external pressure source is opened in the inner wall of the housing.

[Operation] With such a means, an appropriate pressure can be introduced only from the pressure introduction path to the pressure receiving surface of the rotor. Therefore, this pressure utilizes the thrust force that urges the rotor, It is possible to counter the thrust force generated at the time of starting the compressor.

[Embodiment] An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows that the thrust force adjusting mechanism according to the present invention is
The one used for the compressor is shown.

The turbo compressor 1 is configured by uniaxially coupling a radial turbine 2 and a radial compressor 3 with a rotor 4 and holding the same in a housing 5. The radial turbine 2 has a turbine blade 2a, is introduced from a fluid inlet 6 provided on the side of the turbine blade 2a, and is discharged to a fluid outlet 7 provided in the axial direction.
Is adiabatically expanded, and is rotationally driven by the energy of the working fluid M1. The rotational force obtained in the turbine blade is transmitted to the compressor blade 3a via the rotor 4 and adiabatically compresses the working fluid M2 introduced from the fluid inflow port 8 provided in the axial direction of the compressor 3 to form a fluid. Outlet 9
It is used for work sent to.

At this time, the rotor 4 is rotatably supported by the housing 5 by a dynamic pressure gas bearing 10 between the rotor 4 and the housing 5. As described above, the dynamic pressure gas bearing 10 forms a gas film between the rotor 4 and the bearing surface formed by the inner wall of the housing 5 to support the rotor 4 by floating from the bearing surface. It is a thing.

This dynamic pressure gas bearing 10 is a thrust bearing 10 that supports a thrust runner protruding from the center of the rotor from both sides through a gap.
and a journal (radial) bearing 10b supporting both sides of the rotor sandwiching the thrust bearing 10a.

In addition, the working fluids M1 and M2 circulated on the turbine 2 side and the compressor 3 side are prevented from leaking into the dynamic pressure gas bearing 10 through the space behind the main plate of each blade. A labyrinth seal 11 is provided between the turbine 2 and the compressor 3 in the vicinity of a connecting portion of the turbine 2 and the compressor 3 with the rotor 4.

The turbo compressor having such a structure is provided with the following mechanism according to the present invention. First, by forming a step in the rotor 4 provided with the labyrinth seal 11 on the turbine side to change the shaft diameter of the rotor 4, a pressure receiving surface A having an area orthogonal to the axial direction is provided. I am trying. Further, on the inner wall 5a of the housing facing the labyrinth seal 11, a pressure source (not shown) or a pressure introducing path 12 for introducing gas of pressure P1 is opened, while the journal bearings 10 on both sides are formed.
A pressure introducing path 13 for introducing a gas of pressure P2 from a pressure source (not shown) is opened in the housing inner wall 5b of the thrust bearing 10a communicating with b. As a result, the pressure receiving surface A of the rotor 4 located between the seals 11 is
The pressure of P1 and the pressure of P2 act on the other rotor end surface B, respectively.

The reason for positively forming the step in the rotor 4 in this manner is that it is the most direct means for forming the pressure receiving surface A in the rotor 4 which is separated from other gap regions.

With this structure, when the turbo compressor starts rotating, the imbalance of the thrust force applied to the rotor 4 can be adjusted as follows.

Now, FIG. 2 shows the relationship of forces acting in the axial direction of the rotor 4. As is apparent from the figure, the pressure P1 acts on the pressure receiving surface A, while the pressure P2 acts on the end surface B on the compressor side corresponding to the pressure receiving surface A. Therefore, in this case, the rotor 4 as a whole is assumed to be positive in the right direction in the drawing,
= (P1-P2) ・ (S2-S1) biasing force is generated.

However, since this urging force acts in the direction to counteract and cancel the thrust force F0 applied to the compressor side at the time of starting the rotation of the turbo compressor, the thrust force F0
It is possible to completely cancel this by reducing FC or setting FC = F0 by appropriate adjustment. That is, here, in the turbo compressor, the problem that the thrust runner comes into solid contact with the housing 1 and is rotationally activated in a state of being strongly pressed against the housing 1 is effectively removed, and a smooth start-up of rotation is obtained. A gas film is formed between the bearing surface and the number of rotations easily increases. Further, as a result of reducing the PV value at the time of solid contact, wear is reduced and durability is improved.

FIG. 3 shows a bootstrap type air cycle machine used for air conditioning of an aircraft as a specific practical example of the turbo compressor 1. The parts corresponding to those in FIG. 1 are designated by the same reference numerals. This one supplies high-temperature and high-pressure bleed air extracted from an engine to a compressor 3 through a fluid inlet 8, and after being compressed by the compressor 3 it is used for heat exchange with ram air (outside air) in a heat exchanger 20. The fluid is continuously supplied to the turbine 2 and adiabatically expanded by the turbine 2 to produce cold air for air conditioning. The cold air is mixed with bleed air to have an appropriate temperature, and is supplied to the cabin, cockpit, or other room. Then, the turbo compressor 1
Is configured to supply a part of the working fluid from the compressor 3 to the turbine 2 to the introduction pressure gas bearing 10 via the compression force introduction path 13, and the pressure provided with a valve at the fluid inlet 8 of the copressor 3. One end of the introduction path 12 is connected, and the other end of the path 12 is opened at a portion facing the pressure receiving surface A.

In this air cycle machine, the compressor 3 is not boosted at startup and P2 <M2 due to pressure loss. Therefore, when pressure P1 is not applied to the pressure receiving surface A, M2> P2 = M1> P1 The relationship is established. Therefore, due to this pressure distribution,
Thrust force is generated from the compressor 3 in the direction of the turbine 2, and the rising characteristics deteriorate.

On the other hand, when the fluid having the pressure P1 is directly supplied to the pressure receiving surface A through the pressure introduction path 12, P1 = M2> P2 = M1 and the thrust force at the time of starting can be reduced and the rising characteristic can be improved. If the turbo compressor in the aircraft fails to start or fails to start, air conditioning air cannot be supplied to the cabin or the cockpit, which is extremely dangerous, but the present invention effectively eliminates such a problem. You can

After starting, close the valve of the pressure introduction path 12, control the appropriate pressure by the valve,
It is possible to adopt a mode in which P1 is almost always matched with M2 without the valve or in the fully opened state.

Although one embodiment of the present invention has been described above, the present invention is not limited to the above embodiment and various modifications can be made. For example, the pressure receiving surface formed in the middle of the seal may have several steps. The area of the pressure receiving surface and the pressure of each pressure source can be arbitrarily set as long as the required pressure relationship is maintained. The pressure introduction path communicating with the pressure receiving surface may be provided at the position of the inner wall of the housing facing the pressure receiving surface.

The both pressure sources may be provided outside, or the working fluid inside the line may be used via a valve. The pressure P2
As for the above, the present invention can be implemented even in a mode in which this is not introduced.

Further, the thrust force adjusting mechanism of the present invention is mainly intended to improve the starting and characteristics at the time of starting the turbo compressor, but it can be continuously used even after the starting. In this case, it is conceivable to use the pressure of the fluid to be introduced in accordance with the thrust force that changes according to the operating state, such as controlling the pressure of the fluid or adjusting it appropriately with a valve or the like. In addition, if it is used in this way, the thrust runner can be made smaller than the conventional one.

[Advantages of the Invention] The present invention having such a configuration makes it possible to effectively adjust and reliably remove the thrust force that has caused problems such as a start failure at the time of starting, etc. The thrust force adjusting mechanism can be provided.

Further, with this configuration, the thrust force after starting can be reduced, so that the effect of reducing the thrust runner and the thrust bearing can be obtained at the same time.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of a thrust compressor which is an embodiment of the present invention used in a turbo compressor. FIG. 2 schematically shows the relationship of pressures acting in the thrust direction of FIG. FIG. 3 is a diagram showing a practical example in which the turbo compressor is applied to an air conditioning machine for air conditioning of an aircraft. 1 ... Turbo compressor 4 ... Rotor 5 ... Housing 10 ... Dynamic pressure gas bearing 12 ... Pressure introduction path A ... Pressure receiving surface

Claims (1)

[Scope of utility model registration request] 1. A rotor for connecting a turbine and a compressor is housed in a housing through a minute gap, and a seal is provided to make the gap airtight, and the rotor is utilized by relative rotation between the rotor and the housing. In a turbo compressor in which the fluid existing in the gap is supported by the housing by a dynamic pressure gas bearing that forms a gas film, the diameter of the rotor near the turbine is changed stepwise, Form a step forming a pressure receiving surface in the thrust direction that is perpendicular to the rotor axis, and the seal facing the housing from the inner diameter side to the outer diameter side of the step is provided on the inner diameter side and the seal provided on the outer diameter side. The rotor is configured to be closed by an external pressure source on the inner wall of the housing facing the pressure receiving surface in the thrust direction. Thrust force adjustment mechanism of the turbo-compressor, characterized in that is opened a pressure introduction path for introducing a pressure against the thrust force.