JPH0142659Y2 - - Google Patents

Description

[Detailed Description of the Invention] Technical Field The present invention relates to a gas bearing structure for a gas turbine.

Prior Art In gas bearings, it is necessary to always maintain a minute gap between the bearing and the rotating shaft in order to generate a gas film between the bearing and the rotating shaft to support the rotating shaft. In addition, in gas turbines, the journal part provided between the turbine wheel of the rotating shaft and the compressed impeller has a larger diameter than the rotating shaft part outside the journal part, so that the circumferential speed of the journal part is increased and sufficient It is designed to generate a gas film. However, the rotating shaft of the gas bearing becomes hotter than the bearing portion due to heat transferred from the turbine wheel through which high-temperature gas passes. This causes a difference in thermal expansion, making it impossible to ensure bearing clearance. For this reason, in the prior art, a method has been adopted in which a mechanism is provided on the bearing side to escape the thermal expansion of the rotating shaft. However, this method requires a fairly complicated structure in order to constantly maintain the minute bearing clearance in the operating range from low temperatures to high temperatures, and a perfect structure has not yet been obtained. As a result, bearing performance and durability deteriorate. In addition, cooling the bearing by supplying air in the axial direction to the journal part of the rotating shaft for a high-temperature furnace is
For example, as described in Japanese Utility Model Publication No. 18-1119, in the case of a gas turbine, a journal section is provided between the turbine wheel and the compressor impeller, so that the journal section receives radiant heat from the turbine from a short distance. This caused the problem that the turbine side of the journal section became particularly hot.

Purpose of the invention In view of the above, the purpose of the present invention is to obtain a gas bearing structure that can reduce the influence of thermal expansion.

Composition of the Invention In the gas bearing structure according to the invention, the journal part provided between the turbine wheel of the rotating shaft and the compressor impeller has a larger diameter than the rotating shaft part outside the journal part. The outer rotating shaft portion of the journal portion is connected to a first inner flange located on the turbine wheel side and a second inner flange located on the complex impeller side.
an inner cavity is formed between the first and second inner flanges within the journal part, and a first communication hole is formed in the first inner flange in the axial direction. and a second communication hole is provided in the journal portion in the radial direction, so that a connection with the outside of the rotating shaft enters through the first communication hole, passes through the internal cavity, and exits from the second communication hole. It is characterized in that gas is circulated between the inner cavity and a bearing member is engaged with the journal portion.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows a gas turbine to which the present invention is applied. A turbine wheel 2 is integrally attached to the right end of the rotating shaft 1. A compressed impeller 3 is attached to the left end in FIG. 1, and the rotating shaft 1 can extend further to the left than the compressed impeller. In the gas turbine shown in FIG. 1, air is taken into a compressor along arrow A, compressed there, and sent to a combustor (not shown), and combustion gas from the combustor is sent to a turbine wheel 2 as shown by arrow B. It acts and drives it. This rotating shaft 1 is supported by a gas bearing structure according to the present invention.

An annular flange 5 is fixed to the bearing housing 4, and the inner end of the flange 5 serves as a support 6 for supporting the gas bearing. Referring also to FIGS. 2 and 3 below, the turbine-side side wall of the housing 4 is a flange 8 forming a labyrinth 7, and a heat insulating material 9 is disposed around the outer periphery of the flange 8. A bearing chamber 10 is formed in the housing 4 having such a structure, and fresh air is supplied from the compressor side to this bearing chamber 10 through a gap indicated by 11 or an appropriate port, and the air in the bearing chamber 10 is Fresh air can gradually escape from the labyrinth 7 on the turbine side, so that fresh air can be constantly supplied to the bearing chamber 10.

The rotary shaft 1 also has a diameter substantially equal to that of the compressor portion in its journal portion, and can also be referred to as a rotary shaft main body. An annular journal member 12 is fitted into a journal portion of the rotating shaft 1 to be supported by a gas bearing. The annular journal member 12 has annular inner flanges 13 and 14;
Their inner circumferential surfaces serve as fitting portions. One inner flange 13 is close to the compressed impeller 3, and the other inner flange 14 is engaged with the shoulder 15 of the rotating shaft 1 and is connected to the flange 13 on the left at a distance from the turbine wheel 2. 3
is relatively larger than the distance between them. Therefore, the inner flanges 13 and 14 are arranged offset toward the compressor with respect to the outer cylindrical portion of the annular journal member 12. Further, one end of the outer cylindrical portion of the annular journal member 12 is in contact with the back surface of the compressor impeller 3, but the other end is not in contact with the turbine wheel 2. With this configuration of the rotary shaft journal portion, heat transfer from the turbine wheel 2 is performed only by the rotary shaft main body having a smaller diameter than the journal member 12, and the transfer cross-sectional area is small, so that the amount of heat transfer is small. The amount of heat transferred to the outer cylindrical portion of the journal member 12 via the flanges 13 and 14 is also reduced. Further, due to the aforementioned offset of the inner flanges 13 and 14 toward the compressor side, the thermal gradient of the rotary shaft body becomes uniform in the heat distribution in the outer cylindrical portion of the journal member 12.

Since the journal portion of the rotating shaft 1 has a fitting structure, ceramic with low thermal conductivity is formed on these fitting portions, the shoulder portion 15, the inner surface of the outer cylindrical portion, and the surface of the flange 14 facing the turbine wheel 2. can be coated to further reduce thermal expansion of the journal member 12. Preferred examples of ceramic coatings include thermal spraying of chromium oxide (Cr ₂ O ₃ ).

In FIG. 3, an annular chamber 16 formed into an internal cavity by the above-mentioned rotating shaft body and journal member 12.
is formed, and the annular chamber 16 and the bearing chamber 10 are
A communication hole 17 provided in the inner flange 14 in the axial direction
and communicate with each other through communication holes 18 provided in the journal member 12 in the radial direction. Due to the rotation of the rotating shaft 1 and the journal member 12, the annular chamber 16
The air inside is blown outward by centrifugal force and flows out from the radial communication hole 18 into the bearing chamber 10, and the corresponding amount of air flows from the axial communication hole 17 into the chamber 16.
flow inside. Therefore, the annular chamber 16 and the bearing chamber 10
Circulating flow occurs between the
The air temperature within the annular chamber 16 will decrease.
As a result, the temperature difference between the inner and outer surfaces of the journal member 12 and the temperature difference between the journal member 12 and a bearing to be described later are reduced, and changes in the gap therebetween can be reduced. In particular, the axial communication hole 17 is provided in the inner flange 14 located on the turbine wheel 2 side, and the circulating air flow enters through the axial communication hole 17 and passes through the annular chamber 16 which is an internal cavity. It is formed so as to exit from the communication hole 18 in the radial direction. Therefore, the air outside the rotating shaft 1 in the bearing chamber 10 flows through the axial communication hole 17.
When entering the annular chamber 16, it first passes between the turbine wheel 2 and the inner flange 14, and while effectively cooling the inner flange 14, which tends to become extremely hot due to radiant heat from the turbine. I will be entering.

Although a known gas bearing can be used as the bearing that engages the annular journal member 12,
This embodiment employs a tailing pad gas bearing. As shown in FIGS. 1 and 2, bearing pads 20 are arranged at equal intervals around the outer circumference of the journal member 12. As shown in FIGS. The lower two pads 20 in FIG.
It is attached to a pivot 22 which is screwed to the.
Each pivot 22 is further locked by a nut. The upper pivot 22 is slidably fitted into a beam 23 supported by two supports 6, abuts on an adapter 25 attached to a beam 24 extending from one of the supports 6, and is further spring loaded. With this configuration, when the rotating shaft 1 rotates, gas pressure is generated due to the wedge film action of the gas dragged into the gap between the journal member 12 and the pad 20, thereby performing the action of a gas bearing.

Effects of the invention As explained above, according to the invention, gas circulation occurs between the outside and the internal cavity, which promotes cooling of the journal part and reduces the difference in thermal expansion between the journal part and the bearing member. , a predetermined minute clearance can be maintained. Particularly, a first communication hole is provided in the axial direction in the first inner flange located on the turbine wheel side, and a second communication hole is provided in the journal part in the radial direction, so that the gas circulation can be carried out in the same direction. The gas enters through the first communication hole, passes through the internal cavity, and exits through the second communication hole, so that when the gas enters the first communication hole, the first turbine wheel and the first inner flange are connected to each other. This effectively cools the first inner flange, which is likely to become extremely hot due to radiant heat from the turbine. Local thermal expansion of the journal portion is alleviated, and a gas turbine gas bearing structure with excellent performance and durability can be obtained.

[Brief explanation of the drawing]

Figure 1 shows the second part of the gas turbine to which the present invention is applied.
A cross-sectional view taken along the line - in the figure, Figure 2 is the first
A cross-sectional view taken along the line - in the figure, Figure 3 is the first
It is an enlarged view of the main part of the figure. 1...Rotating shaft, 2...Turbine wheel, 4...
... Bearing housing, 10 ... Bearing chamber, 12 ... Journal member, 16 ... Annular chamber, 17, 18, 3
2, 33...Communication hole, 30...Journal part, 3
1...Internal cavity.

Claims (1)

[Scope of utility model registration request] A journal portion provided between the turbine wheel and the compressed impeller of the rotating shaft has a diameter larger than a rotating shaft portion outside the journal portion, and the journal portion and the rotating shaft portion outside the journal portion are connected to each other. joined by a first inner flange located on the turbine wheel side and a second inner flange located on the complex impeller side, and between the first and second inner flanges within the journal part. an internal cavity is formed, the first inner flange is provided with a first communication hole in the axial direction, and the journal portion is provided with a second communication hole in the radial direction; Gas is circulated between the outside of the rotating shaft and the internal cavity so as to enter through the hole, pass through the internal cavity, and exit from the second communication hole, and further, the annular journal member is engaged with the bearing member. gas turbine gas bearing structure.