JP3873481B2 - Centrifugal compressor with coolant jet nozzle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accelerate mixing of working gas and injection fluid, and suppress the generation of erosion or vibration in a multistage centrifugal compressor equipped with a cooling fluid injection nozzle. SOLUTION: With the centrifugal compressor, plural impellers 12 are arranged in the axial direction of a rotary shaft 11. In this case, a corner part 26a is formed at a maximum diameter part of a return passage for introducing the flow of working gas coming from the front stage impeller to the next stage impeller. Then a fluid inlet 51 from which cooling fluid to be mixed with working gas is injected, is formed at the corner part, and a cooling fluid injection nozzle 52 is attached to the fluid inlet. Since the cooling fluid is injected from the nozzle 52 to a working gas flow-stagnation part, turning of the injection fluid in the circumferential direction is improved, and turbulence of the working gas can be prevented.

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a multistage centrifugal compressor used in a chemical plant or the like, and more particularly to a centrifugal compressor with a cooling liquid injection nozzle that injects an evaporable liquid into the compressor.
[0002]
[Prior art]
When high pressure is required in a centrifugal compressor, the single-stage pressure ratio cannot be increased so much, so a multi-stage centrifugal compressor having a large number of impellers attached to one shaft is used. In particular, when a pressure as high as several tens of atmospheres is required as in an ethylene plant, the compressor itself is configured in multiple stages, and each compressor has several stages to 10 or more stages. When working gas flows through such a multistage centrifugal compressor, depending on the type of gas, a chemical reaction occurs due to the heat generated during compression, resulting in another substance, or reacting with impurities contained in the gas and sludge. It may cause a stain called.
[0003]
In the above-described centrifugal compressor for an ethylene plant, when the naphtha of the working gas is heated to about 140 ° C., the chemical reaction is promoted and naphtha is generated. This sludge adheres to the impeller, which is a rotating body, or enters the seal portion and causes friction. Therefore, in order to reduce the temperature rise of the working gas during compression, there is a wide range of methods that utilize the latent heat of vaporization that draws heat from the working gas when the liquid evaporates by heating when the liquid is directly injected into the working gas during compression. It is used. As the type of this liquid, water is often used.
[0004]
On the other hand, the temperature of the working gas rises due to compression. Before this temperature rise reaches the temperature at which sludge is generated, a method of taking the compressed gas out of the compressor, cooling it, and returning it to the compressor is also conceivable. However, in this method, as a result of operating for a long period of time, the performance of the compressor is gradually lowered, and the temperature rise of the working gas exceeds the design range. If the design temperature is set low to avoid this problem, the machine becomes large and expensive. Therefore, at the beginning of operation, the temperature is set so that sludge is not generated, and liquid injection is used in combination.
[0005]
An example of such a liquid jet is described in US Pat. No. 2,786,626. In the multistage centrifugal compressor described in this publication, liquid refrigerant is injected into the working gas from the top of the return flow path that guides the working gas flowing out from the preceding impeller to the following impeller.
[0006]
Japanese Patent Publication No. 58-135400 and Japanese Patent Application Laid-Open No. 7-127600 are also provided with water injection nozzles for injecting water into the flow path between the stages. In particular, in the case of Japanese Patent Publication No. 58-135400, a nozzle is placed near the diffuser inlet having the largest flow velocity downstream of the impeller, and in a stationary wall surface facing the core plate of the further upstream impeller in Japanese Patent Laid-Open No. 7-127600. It is arranged. Furthermore, Japanese Patent Application Laid-Open No. 10-18976 describes a method for controlling the amount of water ejected from a water ejection nozzle.
[0007]
[Problems to be solved by the invention]
In a multistage centrifugal compressor with liquid injection, it is necessary to control the liquid to be injected in order to control the temperature of the working gas. By the way, when liquid injection is performed between the stages of the compressor using the injection nozzle, the flow of the working gas is not uniform in the circumferential direction, and thus there is a possibility that the liquid injection effect does not necessarily occur. This is because the working gas flowing into the compressor in the return flow path is distributed to the next stage impeller flow path. The non-uniform flow causes a partial increase in the working gas temperature and causes sludge. Further, if the non-uniformity of the liquid ejected from the liquid ejection nozzle is too strong, the flow becomes uneven in the circumferential direction, and the impeller is vibrated when the particles of the ejected liquid flow into the impeller, May cause unstable vibration.
[0008]
In order to increase the uniformity of the jet liquid in the circumferential direction, if the quantity of the jet liquid is increased and the particles of the jet liquid are reliably diffused in the circumferential direction, the liquid remaining without being evaporated in the flow path downstream from the jet position Particles can cause erosion. As another method of increasing the uniformity of the propellant, a method of increasing the jet speed of the propellant can be considered, but in this case, the flow of the propellant affects the flow of the working gas, and the fluid performance of the compressor is reduced. There is a risk of lowering.
[0009]
That is, in the centrifugal compressor described in the above-mentioned U.S. Pat. No. 2,786,622, the working gas must flow through a section with a large curvature, but in the section with a large curvature, the working gas is biased toward the outer peripheral side wall surface by centrifugal action. Flowing. For this reason, even if it is going to inject liquid from the top part of a return channel, injection is difficult. Further, the injection liquid must be injected obliquely or vertically with respect to the flow of the working gas, resulting in a mixing loss in the flow of the working gas and the injection liquid. These can cause noise and vibration, and particularly when the injection position can be taken only at one place in the circumferential direction, the adverse effect is significant.
[0010]
Moreover, in the centrifugal compressor described in Japanese Examined Patent Publication No. 58-135400, an injection nozzle is provided on the side plate side diffuser wall surface. Since the working gas has a flow velocity in the diffuser portion, the mixing loss of the working gas and the injected liquid increases during the liquid injection. Further, if a diffuser with blades is used as the diffuser, erosion may occur, so that only a diffuser without blades can be used.
[0011]
Furthermore, in the centrifugal compressor described in JP-A-7-127600, liquid injection is possible with a vaned diffuser having diffuser blades, but the distance of the liquid injection path from the outside of the compressor to the liquid injection position is long. The structure is complicated. It should be noted that since the dirt is generated in the liquid jet passage as the operation time elapses, it is necessary to perform maintenance even during operation, but with this structure, maintenance during operation is difficult.
[0012]
In the centrifugal compressor described in Japanese Patent Laid-Open No. 10-18976, liquid injection nozzles are provided between the stages and the suction pipe. Although the flow of the jet liquid in the circumferential direction is improved by jetting the liquid through the suction pipe, the jet nozzle between stages is the same as that described in the above-mentioned US Pat. No. 2,786,626, and the jet liquid from the stage is There is still a need for improved flow.
[0013]
The present invention has been made in view of the above-described problems of the prior art, and an object thereof is to efficiently mix an injection liquid with a working gas in a multistage centrifugal compressor that involves liquid injection. Another object of the present invention is to realize a liquid ejection system having a simple structure. Still another object of the present invention is to realize a highly reliable liquid ejection system that does not cause erosion or vibration. Still another object of the present invention is to provide an inexpensive liquid ejection system.
[0014]
[Means for Solving the Problems]
In order to achieve the above object, the first feature of the present invention is that a plurality of impellers are mounted on a rotating shaft, and a return flow path is formed for guiding the flow of the working gas exiting the front impeller to the rear impeller. In the multistage centrifugal compressor, a corner portion is formed at the maximum diameter position of the return flow path, and a coolant injection nozzle for injecting the coolant from the corner portion is provided.
[0015]
In order to achieve the above object, the second feature of the present invention is that a rotating shaft, a plurality of impellers mounted on the rotating shaft, bearing means for rotatably supporting the rotating shaft, and an impeller at the front stage In the centrifugal compressor comprising a plurality of inner casings and diaphragms that form a plurality of return flow paths for guiding the flow of the working gas that has exited to a subsequent impeller, and a casing that houses these members, at least one of the above-described centrifugal compressors The return flow path has a corner portion formed by the casing formed with a cylindrical surface parallel to the axial direction and an inner casing having one surface perpendicular to the rotation axis. A mounting hole is formed in the casing for mounting the coolant spray nozzle.
[0016]
The opening is formed on the downstream side of the maximum diameter position of the diaphragm; the opening is formed on the upstream side of the maximum diameter position of the diaphragm, and the injection direction of the cooling liquid injection nozzle is substantially axial; The coolant sprayed from the spray nozzle is water, and its temperature is not less than the suction temperature of the working gas and not more than 140 ° C .; the coolant spray nozzles are provided at a plurality of locations in the circumferential direction; on the suction side of the first stage impeller A coolant injection nozzle is provided.
[0019]
In any of the above features, the working gas is preferably a naphtha for producing ethylene.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, some embodiments of the present invention will be described with reference to the drawings. 1 and 2 are longitudinal sectional views showing an embodiment of a multistage centrifugal compressor provided with a liquid injection nozzle according to the present invention. FIG. 1 is an overall view thereof, and FIG. It is an enlarged view.
[0021]
In FIG. 1, in a multistage centrifugal compressor for an ethylene plant having four stages of impellers, for example, the rotating shaft 11 is rotatably supported and accommodated in a casing 21 by bearings 41a and 41b. A plurality of impellers 12 are attached in the axial direction of the rotating shaft 11. A diffuser 22 having a diffuser vane for pressure recovery is formed downstream of the impeller 12 in the radial direction of the impeller, and the working gas is further downstream of the diffuser to the next impeller. In order to guide, a return flow path 24 is formed to return the radially outward flow back radially inward.
[0022]
A return vane 25 is formed in the return flow path 24 in order to make the flow of working gas to the next stage impeller uniform. The return channel 24 is further radially outwardly covered with a casing 21, and the casing 21 defines the return channel 24. That is, the return flow path 24 includes a portion extending radially outward, an arc-shaped return bend portion 26, a portion extending radially inward, and a corner portion 26 a located on the shoulder of the return bend portion 26. I have. As will be described in detail below, the corner portion 26a is newly provided in the present invention in order to attach the liquid injection nozzle. A liquid injection port 51 for injecting a coolant is formed on the wall surface of the casing 2 facing the corner portion 21a, and a liquid injection nozzle 52 is attached to the liquid injection port.
[0023]
After the working gas exiting the impeller recovers its pressure in the diffuser section and is boosted, the main flow 61 flows substantially along the flow path. On the other hand, since the return bend portion 26 of the return flow path 24 is a curved flow path, the flow separated from the main flow generates a vortex and forms a wake 62. The wake 62 stays in the corner 24a stably due to the presence of the corner 26a.
[0024]
Cooling liquid is jetted from the liquid jet nozzle 52 into the stagnant wake 62, and the staying wake 62 is flowed together with the main stream 61. At this time, the cooling liquid is mixed with the main flow 61 while being turned in the circumferential direction. Therefore, the mixing loss of the working gas and the cooling liquid can be reduced during the liquid injection. Moreover, since the momentum of the jet liquid is much smaller than the momentum of the main flow 61, the flow direction and the flow speed of the main flow are not changed by the liquid jet. Therefore, the fluid performance of the compressor is not deteriorated. Further, the wake 62 staying in the corner portion 26a has almost no velocity component in the main flow direction, but has a circumferential velocity component, so that the circumferential direction can be obtained without increasing the liquid ejecting means in the circumferential direction. Coolant can be supplied to the whole. According to an experimental study by the present inventor, even when only one liquid ejecting means is attached in the circumferential direction, the circulation of the cooling liquid in the circumferential direction is improved as compared with the conventional one.
[0025]
The state of this circumferential flow will be described with reference to FIGS. FIG. 3 shows a case where the coolant injection nozzle is provided at the center of the return bend 26 part of the return flow path 24, and FIG. 4 shows a case where the coolant injection nozzle is provided at the corner of the return bend 26 part of the return flow path 24. . In FIG. 3, the jetted coolant particles 63 are mixed with the main flow existing in the vicinity of the jet nozzle in a relatively short time, and are moved along the main flow 61 of the working gas to the flow path provided with the return vane 25. Carried. Since the swirl velocity component of the main flow of the working gas is smaller than the radial velocity component, only the two or three return channels formed between the return vanes 25 using the return vane 25 in the vicinity of the coolant injection nozzle 52 as a guide. Flow into. For this reason, the coolant cannot be supplied to a position far from the position where the coolant spray nozzle 52 is provided, for example, on the opposite side in the circumferential direction, and the working gas flowing through this portion is not mixed with the coolant, and the next It flows into the stage impeller 12. Accordingly, the cooling effect of the working gas is small, and the temperature of the working gas is unevenly distributed in the circumferential direction, which causes generation of vibration noise.
[0026]
On the other hand, when the coolant injection nozzle is provided at the corner of the return channel 24 shown in FIG. 4, most of the liquid particles 63 are corners except for some of the coolant particles injected up to the main flow side. The circumferential speed component staying in the part is dragged by the flow 62a of the stagnation part where the majority is swirled in the circumferential direction. Some liquid particles collide with the vertical walls forming the corners and bounce off, and then join the stagnation part flow 62a. The ejected liquid particles 63 gradually move inward in the radial direction so as to be dragged by the mainstream while continuing to turn. As a result, the coolant can be supplied to most of the return channels formed between the return vanes 25. By providing the working gas stagnation portion in the return bend portion in this manner, the circumferential distribution of the liquid particles is made uniform, and the temperature distribution of the working gas flowing into the next stage impeller 12 is also improved. Thereby, the cooling effect of the working gas is enhanced, generation of sludge can be suppressed, and generation of unstable vibration and noise can be reduced.
[0027]
Next, the manufacturing method of this corner | angular part is demonstrated. The casing 21 is manufactured in a cylindrical shape, and an inner casing 27 having a fitting portion is attached to the cylindrical casing 21. A front surface side of the inner casing 27 forms a return portion of the return flow path 24, and an outer diameter side thereof is a plane perpendicular to the rotation shaft 11. The back surface side of the inner casing 27 forms a flow portion radially outward of the return flow path 24, and is formed in an arc shape or a smooth curved shape. A diaphragm 28 is disposed between two successive inner casings 27.
[0028]
A diffuser vane 23 of a diffuser with vanes is formed on the front side of the diaphragm 28, and a return vane 25 of the return flow path 24 is formed on the back side. The diffuser vane 23 and the return vane 25 may be manufactured in advance by NC processing or the like, and may be welded to the diaphragm 28 or may be integrally processed with the diaphragm 28. The outermost diameter portion of the diaphragm 28 is formed in an arc shape or a smooth curved shape according to the shape of the return flow path.
[0029]
A stage labyrinth 32 is attached to the inner diameter side of the diaphragm 28, and an impeller labyrinth 31 is attached to the inner diameter side of the inner casing 27. The impeller labyrinth 31 is provided so as to face the bell mouth portion on the suction side of each impeller 12 and is composed of a non-contact type labyrinth seal. Moreover, the stage labyrinth 32 is provided in the back side of each impeller 12, and this also consists of a labyrinth seal. A minute gap is formed between the impeller labyrinth 31 and the stage labyrinth 32 and the impeller 12. This sealing means prevents leakage of working gas compressed by the impeller to the suction side, leakage of working gas before compression to the discharge side of the impeller, and the like.
[0030]
Since the outer diameter part on the front side of the inner casing 27 constituting the return bend 26 part has a flat shape, the shape becomes simple and complicated circular solid processing is unnecessary, and the cost can be reduced by reducing the number of processing steps. Become. Furthermore, since the corner 26a is formed in the return bend 26, even if a machining error occurs in the axial position of the coolant injection nozzle, there is no effect on the radial position of the return flow path. Can be supplied in all directions.
[0031]
In the present embodiment, the cooling liquid injection nozzles 52 are provided in all the return flow paths between the stages, but may be provided only between the stages at the highest temperature or only between the stages close to the suction. Moreover, you may combine with the cooling fluid injection in a suction part. Furthermore, it goes without saying that it may be provided between two or more stages. Further, if the coolant injection nozzles are provided at a plurality of locations in the circumferential direction, the distribution of the coolant in the circumferential direction can be made more uniform. Furthermore, if the circumferential direction positions of the front-stage cooling liquid injection nozzle and the rear-stage cooling liquid injection nozzle are changed in consideration of the trajectory of the flow exiting the front-stage impeller and flowing into the rear-stage impeller, further cooling liquid can be obtained. The distribution in the circumferential direction can be made uniform.
[0032]
In the present embodiment, the axial position of the coolant injection nozzle 52 is set at an almost intermediate position of the return flow path, but the effect of the present invention can be obtained as long as it is downstream of the maximum diameter portion of the diaphragm 28. Further, although the coolant injection nozzle 52 is guided from the radial direction of the casing 21, it may be guided from a direction inclined with respect to the radial direction. That is, the effect of the present invention can be obtained if the coolant is injected into the stagnation part of the working gas. Since the tip of the coolant injection nozzle 52 may be contaminated by sludge, it is desirable to have a structure that allows the coolant injection nozzle 52 to be replaced even during operation.
[0033]
Another embodiment of the present invention is shown in FIG. In this embodiment, the position of the coolant injection nozzle 52 in the axial direction is different from the above embodiment. Therefore, the corner portion of the return channel is formed in the radially outward flow portion. Furthermore, the jet direction of the coolant is the axial direction. In the present embodiment, since the direction of the main flow 61 of the working gas and the injection direction of the coolant substantially coincide with each other at the maximum diameter portion of the return bend 26, mixing with the main flow is promoted. In addition, since the stagnation part of the working gas flow is formed at the corner part, the coolant may circulate in the circumferential direction. And since the distance from an injection position to a return channel can be taken long, the cooling fluid particle 63 is spread | diffused in the circumferential direction, and cooling performance improves.
[0034]
FIG. 6 shows still another embodiment of the present invention. In this embodiment, in addition to injecting the coolant from between the stages, the coolant is also injected from the suction pipe. When the coolant is injected from the suction pipe, the circumferential distribution of the coolant is remarkably improved. However, in this case, if the amount of the coolant increases, erosion may occur in the first stage impeller. Therefore, the amount of the cooling liquid supplied from the suction pipe is set to be less than the amount of liquid that may cause erosion, and the shortage is supplied from between the stages. According to the present embodiment, the circumferential distribution of the coolant can be made uniform and the occurrence of erosion can be suppressed.
[0035]
In any of the above embodiments, water can be used as the cooling liquid, and the cooling at the supply source is between 30 ° C. and 140 ° C. which is the standard suction temperature. Available as a source. This is because when the spray liquid is heated and evaporated by the working gas, the temperature is lowered by the latent heat of vaporization.
[0036]
As described above, according to each of the above embodiments, in the multistage centrifugal compressor with a liquid injection nozzle, the injection nozzle is attached to the corner of the return bend provided between the stages. A centrifugal compressor can be provided at low cost. Further, since the liquid is ejected from the corner portion, it is possible to reduce the loss due to the mixture of the propellant and the working gas. Furthermore, since the wraparound of the spray liquid in the circumferential direction is improved, the uniformity of the mixture of the spray liquid and the working gas over the circumferential direction is improved, and the generation of sludge can be suppressed. Further, since the jetting speed of the jet liquid is small, it is possible to provide a centrifugal compressor having high fluid efficiency without adversely affecting the flow of the working gas. Furthermore, it is not necessary to increase the amount of the spray liquid excessively.
[0037]
【The invention's effect】
As described above, according to the present invention, in the multistage centrifugal compressor with a liquid injection nozzle, since the injection nozzle is attached to the corner portion of the return bend portion provided between the stages, the occurrence of erosion and vibration can be prevented. Can provide a highly reliable centrifugal compressor.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view of an embodiment of a multistage centrifugal compressor provided with a liquid jet nozzle according to the present invention.
FIG. 2 is a partial detailed sectional view of FIG. 1;
FIG. 3 is a diagram for explaining the action of a spray liquid from a liquid spray nozzle.
FIG. 4 is a diagram for explaining the action of a jet liquid from a liquid jet nozzle.
FIG. 5 is an enlarged cross-sectional view of a liquid jet nozzle portion according to another embodiment of the present invention.
FIG. 6 is a longitudinal sectional view of still another embodiment of a multistage centrifugal compressor provided with a liquid injection nozzle according to the present invention.
[Explanation of symbols]
11 ... Rotating shaft, 12 ... Impeller, 12a ... Impeller side version,
12b ... Core plate, 13 ... Next stage impeller, 21 ... Casing,
22 ... Diffuser,
22a ... impeller core plate side diffuser wall,
22b ... impeller side plate side diffuser wall,
23 ... Diffuser vane,
24 ... return channel, 25 ... return vane,
26 ... Return bend,
26a ... return bend corner,
27 ... Inner casing,
28 ... Diaphragm,
31 ... Imperial labyrinth,
32 ... Stage labyrinth,
51 ... Liquid inlet, 52 ... Coolant injection nozzle,
61 ... Mainstream, 62 ... Backstream,
62a ... Flow of the stagnation part, 63 ... Liquid particles.

Claims (8)

  In a multistage centrifugal compressor in which a plurality of impellers are mounted on a rotating shaft and a return flow path is formed to guide the flow of working gas exiting the preceding impeller to the subsequent impeller, the maximum diameter of the return flow path A centrifugal compressor with a coolant injection nozzle, characterized in that a corner portion is formed at a position, and a coolant injection nozzle for injecting coolant from the corner portion is provided.   A rotating shaft, a plurality of impellers mounted on the rotating shaft, bearing means for rotatably supporting the rotating shaft, and a plurality of guides for guiding the flow of working gas exiting the preceding impeller to the following impeller In a centrifugal compressor including a plurality of inner casings and diaphragms that form a return flow path, and a casing that houses these members, at least one of the return flow paths has a cylindrical surface parallel to the axial direction. The casing has a corner portion made of an inner casing having a surface perpendicular to the rotation axis, and has a mounting hole that opens at a corner portion of the return flow path to which the coolant injection nozzle is attached. A centrifugal compressor equipped with a coolant injection nozzle.   3. The centrifugal compressor with a coolant injection nozzle according to claim 2, wherein the opening is formed on the rear stage side from the maximum diameter position of the diaphragm.   3. The centrifugal compressor with a coolant injection nozzle according to claim 2, wherein the opening is formed on the upstream side of the maximum diameter position of the diaphragm, and an injection direction of the coolant injection nozzle is substantially an axial direction. .   5. The coolant according to claim 2, wherein the coolant sprayed from the coolant spray nozzle is water, and the temperature thereof is not less than the suction temperature of the working gas and not more than 140 ° C. 5. Centrifugal compressor with injection nozzle.   The centrifugal compressor with a coolant injection nozzle according to claim 3 or 4, wherein the coolant injection nozzle is provided at a plurality of locations in the circumferential direction.   The centrifugal compressor with a coolant injection nozzle according to claim 3 or 4, wherein the coolant injection nozzle is provided on the suction side of the first stage impeller. The centrifugal compressor with a coolant injection nozzle according to any one of claims 1 to 7 , wherein the working gas is a naphtha for producing ethylene.

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