JP2004108336A - Compressor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain stable thrust balance even if each of a low pressure section and a high pressure section takes any pressure conditions. <P>SOLUTION: This compressor comprises a first balance piston 12 receiving second pressure P2 by one side face 12A and receiving third pressure P3 by the other side face 12B to cancel thrust pressure TH (P3-P2) produced by a pressure difference (P3-P2) in a high pressure section. The compressor also comprises a second balance piston 13 receiving first pressure P1 by one side face 13A and the second pressure P2 by the other side face 13B to cancel thrust force TL (P2-P1) produced by a pressure difference (P2-P1) in the low pressure section. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a multistage centrifugal compressor that compresses gas in multiple stages by centrifugal force.
[0002]
[Prior art]
Conventionally, as a compressor of this type, a low-pressure section having a plurality of impellers for increasing a gas from a first pressure to a second pressure and a plurality of impellers for increasing the gas from the low-pressure section to a third pressure are described. A high-pressure section, a rotating shaft having one end supported by the radial bearing and the other end supported by the radial bearing and the thrust bearing such that the third pressure side of the high-pressure section faces the second pressure side of the low-pressure section. There is known a so-called Back To Back type fixed to (for example, see Patent Document 1).
[0003]
Further, in this compressor, the compressor is disposed between the low pressure section and the high pressure section so as to receive the discharge pressure (second pressure) of the gas in the low pressure section on one side and discharge the gas in the high pressure section. A balance piston that receives (third pressure) on the other side is fixed to the rotating shaft. With such a balance piston, a thrust force acting on the rotating shaft due to a pressure difference in the low pressure section and a pressure difference in the high pressure section That is, a stable thrust balance with the thrust force acting on the rotating shaft is obtained.
[0004]
[Patent Document 1]
JP-A-8-303381 (FIG. 3)
[0005]
[Problems to be solved by the invention]
By the way, in recent years, the size and speed of the compressor as described above have been increasing, and along with this, the thrust bearing for supporting one end of a rotating shaft provided on the compressor has also been reduced in size. The demand for high-pressure compression of gas, such as for gas injection, is also increasing.
Therefore, if the pressure difference in the low pressure section is too large or too small, such as during degassing during startup or emergency stop, or if the pressure difference in the high pressure section is too large or too small, The pressure state deviates from the range of the design condition assumed in advance, and the thrust force acting on the rotating shaft cannot be balanced only with the balance piston disposed between the low pressure section and the high pressure section. I will.
As described above, when stable thrust balance cannot be maintained, the surface pressure of the thrust bearing that supports the rotating shaft increases, and the metal temperature increases, thereby limiting the operating state of the compressor. Occurred.
[0006]
The present invention has been made in view of the above-described problems, and has as its object to provide a compressor that can obtain a stable thrust balance even when a low-pressure section and a high-pressure section take any pressure conditions. .
[0007]
[Means for Solving the Problems]
In order to solve the above problems and achieve such an object, the present invention provides a low pressure section having one or more impellers for increasing a gas from a first pressure to a second pressure, And a high-pressure section having one or more impellers for increasing the pressure of the gas to a third pressure, and fixed to a rotating shaft such that the third pressure side of the high-pressure section faces the second pressure side of the low-pressure section. A first balance piston fixed to the rotating shaft, receiving the second pressure on one side and receiving the third pressure on the other side, and fixed to the rotating shaft. And a second balance piston that receives the second pressure on the side surface and receives the first pressure on the other side surface.
According to the present invention having such a configuration, the thrust force acting on the rotating shaft due to the pressure difference in the high pressure section is canceled by the first balance piston, and the thrust force acting on the rotating shaft due to the pressure difference in the low pressure section. The force is canceled by the second balance piston.
That is, each of the first balance piston and the second balance piston cancels the thrust force generated in the high-pressure section and the low-pressure section individually, so that the high-pressure section and the low-pressure section are in any pressure condition. Even so, a stable thrust balance can be obtained.
[0008]
In the present invention, it is preferable that the first balance piston is disposed between the low-pressure section and the high-pressure section. With such a configuration, a conventionally used Back To Back type is used. The compressor of the present invention can be easily configured only by adding the second balance piston to the compressor.
[0009]
Further, in the present invention, it is preferable that the second pressure received by the one side surface of the second balance piston is a second pressure of the gas immediately after the pressure is increased in the low-pressure section and the temperature is increased. With this configuration, even if the gas that has been pressurized to the second pressure and heated at the same time leaks from the second balance piston, it condenses or solidifies in the process of reducing the pressure from the second pressure to the atmospheric pressure. Can be prevented.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
In the compressor according to the embodiment of the present invention, as shown in FIG. 1, a rotating shaft 10 is supported in a casing (not shown) at one end by a radial bearing (not shown) and at the other end by a radial bearing (not shown). (Not shown) and a thrust bearing (not shown).
[0011]
A plurality of impellers 11A constituting a low-pressure section are sequentially arranged on the rotating shaft 10 from the one end side to a substantially central portion so that each gas inlet faces one end side (left side in the figure). A plurality of impellers 11B, which are fixed and constitute a high-pressure section, are sequentially arranged from the other end side to the substantially central portion with their respective gas inlets facing the other end side (right side in the figure). Is fixed.
[0012]
The low pressure section discharges the gas of the first pressure P1 sucked from the low pressure section side suction port to the second pressure P2 by the plurality of impellers 11A and then discharges the gas from the low pressure section side discharge port. After the gas of the second pressure P2 discharged from the low-pressure section-side discharge port is sucked from the high-pressure section-side suction port, the gas is raised to the third pressure P3 by the plurality of impellers 11B and then discharged from the high-pressure section-side discharge port. (P1 <P2 <P3).
[0013]
Here, each gas inlet in the plurality of impellers 11A of the low-pressure section is directed to one end side (left side in the figure), and each gas inlet in the plurality of impellers 11B of the high-pressure section is directed to the other end side (right side in the figure). Therefore, the second pressure P2 side of the low-pressure section and the third pressure P3 side of the high-pressure section are disposed so as to face each other with a substantially central portion of the rotating shaft 10 interposed therebetween (the impeller 11A of the low-pressure section). The rear side and the rear side of the impeller 11B of the high-pressure section are disposed so as to face each other), and are of a so-called Back To Back type.
[0014]
Further, a partition plate 14 is arranged between the low-pressure section and the high-pressure section, and the partition plate 14 forms a space between the low-pressure section and the high-pressure section.
In a space located between the partition plate 14 and the periphery of the rotary shaft 10, a first balance piston 12 is fixed to the rotary shaft 10 so as to be interposed in the space. The piston 12 receives the second pressure P2 on one side surface 12A directed to the low pressure section side (one end side), and generates the third pressure P3 on the other side surface 12B directed to the high pressure section side (the other end side). I am going to receive it.
[0015]
Further, on the outer side of the high-pressure section, that is, on the other end side (right side in the drawing) of the high-pressure section, partition plates 15, 16, 17 are sequentially arranged toward the other end side. The partition plate 16 of 15, 16, 17 forms a space between the partition plate 16 and the periphery of the rotating shaft 10.
The second balance piston 13 is fixed to the rotating shaft 10 in a space located between the partition plate 16 and the periphery of the rotating shaft 10 so as to be interposed in this space.
[0016]
Here, in the present embodiment, of the two side surfaces 13A and 13B of the second balance piston 13, one side surface 13A facing one end side (the left side in the drawing) and facing the partition plate 15 and the partition plate 15 are formed. A flow path for introducing a part of the gas immediately after the pressure has been raised from the first pressure P1 to the second pressure P2 in the low pressure section is connected to the space between them, and is directed to the other end (right side in the figure). In the space between the other side surface 13B facing the partition plate 17 and the partition plate 17, a flow path for introducing the gas of the first pressure P1 sucked from the low-pressure section side suction port is connected.
Therefore, the second balance piston 13 receives the second pressure P2 on one side surface 13A directed to one end side (left side in the drawing), and receives the second pressure P2 on the other side surface 13B directed to the other end side (right side in the drawing). The first pressure P1 is received.
[0017]
In the step of compressing the gas using the compressor as described above, first, as shown in FIG. 1, by rotating the rotating shaft 10, the gas at the first pressure P1 is supplied from the low-pressure section side suction port to the low-pressure section. It is sucked in.
The gas of the first pressure P1 sucked into the low-pressure section passes through the plurality of impellers 11A provided in the low-pressure section sequentially from one end side to the substantially central portion side, and is subjected to centrifugal force. It is compressed in multiple stages and is raised to the second pressure P2.
[0018]
The gas whose pressure has been raised to the second pressure P2 in the low-pressure section is discharged from the low-pressure section side discharge port, and after being intercooled, for example, by an intercooler (not shown), is sucked into the high-pressure section from the high-pressure section side suction port.
The gas of the second pressure P2 sucked into the high-pressure section sequentially passes through the plurality of impellers 11B provided in the high-pressure section from the other end side toward the substantially central portion, thereby causing a centrifugal force. Thus, after being compressed in multiple stages, the pressure is increased to the third pressure P3, and then discharged from the high-pressure section side discharge port.
[0019]
By the way, in such a gas compression process, in order to raise the gas from the first pressure P1 to the second pressure P2 in the low-pressure section, the second pressure P2 and the first pressure P1 are increased as shown by white arrows in the drawing. A thrust force TL (P2-P1) resulting from the pressure difference (P2-P1) acts on the rotating shaft 10 toward one end.
Further, in order to increase the pressure of the gas from the second pressure P2 to the third pressure P3 in the high-pressure section, as shown by a white arrow in the drawing, a pressure difference (P3-P2) between the third pressure P3 and the second pressure P2. The thrust force TH (P3-P2) due to the above acts on the rotating shaft 10 toward the other end.
[0020]
Here, in the present embodiment, the first balance piston 12 fixed to the rotating shaft 10 receives the second pressure P2 on one side surface 12A facing one end side, and receives the second pressure P2 on the other side surface 12B facing the other end side. 3, the thrust force TcH (P3-P2) due to this pressure difference (P3-P2) is located at one end with respect to the rotating shaft 10 as indicated by the bold arrow in the drawing. Acts toward.
Further, the second balance piston 13 fixed to the rotating shaft 10 receives the second pressure P2 on one side surface 13A facing one end, and receives the first pressure P1 on the other side surface 13B facing the other end side. Therefore, the thrust force TcL (P2-P1) caused by the pressure difference (P2-P1) acts on the rotating shaft 10 toward the other end, as indicated by the thick arrow in the drawing.
[0021]
Thus, the thrust force TH (P3-P2) to the other end generated by the pressure difference (P3-P2) in the high pressure section is changed to the thrust to one end generated by the pressure difference (P3-P2) in the first balance piston 12. The thrust force TL (P2-P1) to one end generated by the pressure difference (P2-P1) in the low-pressure section can be canceled by the force TcH (P3-P2) and the pressure difference in the second balance piston 13 It can be canceled by the thrust force TcL (P2-P1) to the other end generated by (P2-P1).
[0022]
That is, each of the first balance piston 12 and the second balance piston 13 has a function of individually canceling the thrust force generated in the high-pressure section and the low-pressure section.
For this reason, the pressure difference in the low-pressure section may be too large or too small, such as when starting the compressor or degassing during an emergency stop, or the pressure difference in the high-pressure section may be too large or too small. Irrespective of the pressure condition, a stable thrust balance can be obtained, and a situation in which the operating state of the compressor is limited does not occur.
[0023]
Further, in the present embodiment, the first balance piston 12 is provided at a substantially central portion located between the low-pressure section and the high-pressure section, so that the second balance piston 12 is different from the conventional Back To Back type compressor. The compressor of the present embodiment can be easily obtained simply by adopting a configuration in which the balance piston 13 is added.
[0024]
Further, in the present embodiment, a part of the gas immediately after the pressure is raised to the second pressure P2 in the low-pressure section is introduced into the space on one side surface 13A side of the second balance piston 13 before the intermediate cooling. The second pressure P2 is applied to one side surface 13A of the second balance piston 13.
Since the gas immediately after the pressure is increased to the second pressure P2 in the low-pressure section is heated at the same time as the pressure is increased, even if the gas leaks from the second balance piston 13, the pressure is reduced from the second pressure P2 to the atmospheric pressure. To prevent condensation or solidification.
[0025]
【The invention's effect】
As described above, according to the present invention, each of the first balance piston and the second balance piston cancels each of the thrust forces generated in the high-pressure section and the low-pressure section. Regardless of the pressure condition of the section, a stable thrust balance can be obtained, and the operating state of the compressor is not limited.
[Brief description of the drawings]
FIG. 1 is a schematic diagram for explaining a configuration of a compressor according to an embodiment of the present invention.
[Explanation of symbols]
Reference Signs 10 Rotating shaft 11A, 11B Impeller 12 First balance piston 12A One side surface 12B The other side surface 13 Second balance piston 13A One side surface 13B The other side surface 14, 15, 16, 17 Partition plate

Claims (3)

A low pressure section having one or more impellers for increasing gas from a first pressure to a second pressure, and a high pressure section having one or more impellers for increasing gas from the low pressure section to a third pressure; A compressor fixed to a rotating shaft such that the third pressure side of the high pressure section faces the second pressure side of the low pressure section,
A first balance piston fixed to the rotating shaft and receiving the second pressure on one side and receiving the third pressure on the other side;
A second balance piston fixed to the rotating shaft and receiving the second pressure on one side and receiving the first pressure on the other side. The compressor according to claim 1,
The compressor according to claim 1, wherein the first balance piston is disposed between the low-pressure section and the high-pressure section. In the compressor according to claim 1 or 2,
The compressor according to claim 1, wherein the second pressure received by the one side surface of the second balance piston is a second pressure of the gas immediately after the pressure is increased in the low-pressure section and the temperature is increased.

Images