JP6137983B2 - Multistage centrifugal compressor - Google Patents

Description

  The present invention relates to a multistage centrifugal compressor, and more particularly to a multistage centrifugal compressor including an input shaft that is driven by a prime mover and provided with a bull gear, and one or more output shafts that are provided with pinions that mesh with the bull gear.

  As a background art in this technical field, there is JP 2008-231933 A (Patent Document 1). This publication states that “a large gear (bull gear) 12 that is rotationally driven by an external drive device (prime motor), a small gear (pinion) 14 that meshes with the large gear and rotates at high speed, and a small gear shaft (output shaft) 13. An impeller 16 fixed to the shaft and rotating at high speed around its axis, and a thrust collar 18 fixed to the small gear shaft and slidably supported on the side surface of the large gear and transmitting the thrust force of the small gear shaft to the large gear. When the thrust bearing 20 that supports the thrust force acting on the large gear shaft (input shaft) and the small gear shaft 13 supported by the thrust bearing 20 are moved over a predetermined threshold, the shaft movement is limited. A gear-driven turbocompressor comprising a thrust direction travel limiter 30 is disclosed (see summary).

  Further, the publication discloses that “a thrust direction movement amount limiter 30 that restricts the shaft movement when the small gear shaft 13 supported by the thrust bearing 20 of the large gear shaft 11 exceeds the predetermined threshold value a. Therefore, during normal operation, the axial movement of the small gear shaft 13 by the thrust bearing 20 of the large gear shaft 11 is not more than a predetermined threshold value a, the thrust direction movement amount limiter 30 does not function, and the predetermined threshold value a This function is limited only when an excessive shaft movement exceeding the limit occurs, and thus the shaft movement is limited, so that an excessive contact between the impeller 16 and the casing is essential when an excessive shaft movement occurs on the large gear shaft 11. Can be avoided ”(see paragraphs [0031] and [0032]).

JP 2008-231933 A

  However, the multistage centrifugal compressor described in Patent Document 1 focuses on limiting the amount of movement of the small gear shaft, which is the output shaft, in the thrust direction (axial direction), and the thrust load generated on the output shaft ( It does not consider reducing the load in the thrust direction.

  For this reason, the multistage centrifugal compressor described in Patent Document 1 causes a reduction in the efficiency of the compressor due to friction loss in the sliding portion and a reduction in the mechanical reliability of the compressor due to the thrust load generated in the output shaft. There is a fear.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a multi-stage centrifugal compressor having high efficiency and high mechanical reliability by reducing the thrust load generated on the output shaft. .

In order to achieve the above-described object, a multistage centrifugal compressor according to the present invention includes an input shaft driven by a prime mover, a bull gear provided on the input shaft, a pinion meshing with the bull gear, and an output provided with the pinion. A shaft, a first centrifugal impeller provided at one end of the output shaft, and a second centrifugal wheel provided at the other end of the output shaft and positioned on the downstream side of the fluid flow with respect to the first centrifugal impeller. A centrifugal impeller, a second pinion meshing with the bull gear, a second output shaft provided with the second pinion, and a fluid of the second centrifugal impeller provided on the second output shaft comprising of a third centrifugal impeller located downstream stage side of the flow, the outer diameter of the first centrifugal impeller is set larger than the outer diameter of the second centrifugal impeller The third centrifugal impeller includes the second output shaft. The bull gear, the pinion, and the second pinion are helical gears that are provided on the end opposite to the second centrifugal impeller in the axial direction, and are axially connected to the pinion. The gear load acting on the second centrifugal impeller is the same direction as the fluid load acting on the second centrifugal impeller in the axial direction, and the gear load acting on the second pinion axially is the third centrifugal impeller. The helical gear is twisted in the direction opposite to the fluid load acting in the axial direction, and the fluid load acting in the axial direction on the third centrifugal impeller is the second The centrifugal impeller has a direction opposite to the fluid load acting in the axial direction .

  According to the present invention, it is possible to provide a multistage centrifugal compressor with high efficiency and high mechanical reliability by reducing the thrust load generated on the output shaft.

It is a horizontal sectional view showing a schematic structure of a multistage centrifugal compressor concerning a 1st embodiment of the present invention. It is a schematic diagram for demonstrating the fluid load which acts on the centrifugal impeller of the 1st stage in a thrust direction. It is a schematic diagram for demonstrating the fluid load of the thrust direction which generate | occur | produces in an output shaft with the 1st stage | paragraph centrifugal impeller and the 2nd stage | paragraph centrifugal impeller. It is a schematic diagram for demonstrating the gear load which acts on a thrust direction by meshing | engagement of a bull gear and a pinion. It is a horizontal sectional view showing typically the multi stage centrifugal compressor concerning a 1st embodiment. It is a figure which shows the relationship between the ratio of the outer diameter of the 2nd stage | paragraph centrifugal impeller with respect to the outer diameter of the 1st stage | paragraph centrifugal impeller, and the stress which generate | occur | produces in the blade root in the exit part of a 1st stage | paragraph centrifugal impeller. It is a horizontal sectional view showing typically the multi stage centrifugal compressor concerning a 2nd embodiment. It is a horizontal sectional view showing typically the multi stage centrifugal compressor concerning a 3rd embodiment. It is a horizontal sectional view showing typically the multi stage centrifugal compressor concerning a 4th embodiment. It is a horizontal sectional view showing typically the multistage centrifugal compressor concerning a 5th embodiment. It is a horizontal sectional view showing typically the multistage centrifugal compressor concerning a 6th embodiment.

Embodiments of the present invention will be described in detail with reference to the drawings as appropriate.
Note that, in the drawings shown below, the same members or corresponding members are denoted by the same reference numerals, and redundant description is omitted as appropriate. In addition, the size and shape of the member may be schematically represented by being modified or exaggerated for convenience of explanation.

[First Embodiment]
First, a first embodiment of the present invention will be described with reference to FIGS.
FIG. 1 is a horizontal sectional view showing a schematic configuration of the multistage centrifugal compressor according to the first embodiment of the present invention.

  The multistage centrifugal compressor shown in FIG. 1 includes a prime mover (not shown), a speed increasing unit 100 that transmits the rotational driving force of the prime mover, and a first stage to a third stage that compress a fluid (gas) in stages. The compressor units 1 to 3 of the eyes, a cooling device (not shown) for cooling the compressed fluid (gas), and a control unit (not shown) for overall control are provided. Yes.

  The input shaft 4 of the gearbox 100 is connected to a rotating shaft (not shown) of the prime mover via a coupling (not shown). A bull gear 20 that is a large gear is attached to the input shaft 4. A pinion 21 and a pinion 22 (second pinion), which are two small gears, mesh with the bull gear 20. Here, for the bull gear 20 and the pinions 21 and 22, helical gears having a larger meshing ratio than the spur gear are used from the viewpoint of reducing vibration and noise.

  The pinion 21 and the output shaft 6 (second output shaft) are integrally formed with the output shaft 5 and the output shaft 6 (second output shaft), respectively. The input shaft 4 and the two output shafts 5 and 6 are arranged in parallel to each other. The pinions 21 and 22 may be provided separately from the output shafts 5 and 6 and fixed to the output shafts 5 and 6, respectively. On the two output shafts 5 and 6, substantially cylindrical thrust collars 66 to 69 are fixed by being shrink-fitted.

  The input shaft 4, the two output shafts 5 and 6, the bull gear 20, the pinions 21 and 22, and the thrust collars 66 to 69 are components of the speed increasing unit 100 and are accommodated in the casing 101. The casing 101 has a horizontal plane division structure, and is divided into an upper casing and a lower casing on a plane substantially equal to a horizontal plane including the central axes of the input shaft 4 and the output shafts 5 and 6. The upper casing and the lower casing are coupled using bolts (not shown).

  The input shaft 4 and the bull gear 20 are rotatably supported by compound bearings 60 and 61 held by the casing 101. The composite bearings 60 and 61 are bearings that receive and support a load in the radial direction (radial direction) (radial load) and a load in the thrust direction (axial direction) (thrust load).

  On the other hand, the two output shafts 5 and 6 provided with the pinions 21 and 22 are rotatably supported by radial bearings 62 to 65 held by the casing 101. The thrust load generated in the output shafts 5 and 6 is received and supported by thrust collars 66 to 69 configured to sandwich the bull gear 20 via gaps 71 and 72 (see FIG. 5).

  Lubricating oil is supplied from a lubricating oil system (not shown) to lubricate the composite bearings 60, 61, radial bearings 62-65, thrust collars 66-69, bull gear 20, and pinions 21, 22. Lubricating oil used to lubricate the composite bearings 60, 61, radial bearings 62-65, thrust collars 66-69, bull gear 20, pinions 21, 22 and the like is an oil tank (see FIG. (Not shown).

  A gap 70 (see FIG. 5) on the sliding surface in the thrust direction between the input shaft 4 and the bull gear 20 and the composite bearings 60 and 61 is, for example, about 0.2 mm. During steady operation of the multistage centrifugal compressor, either the composite bearing 60 or the composite bearing 61 is in contact with the sliding surface of the bull gear 20, and the other composite bearing and the sliding surface of the bull gear 20 maintain a gap. ing. However, when the multistage centrifugal compressor is started and stopped, or when the multistage centrifugal compressor is operated beyond the operating limit range in a small flow rate region called surging, the compound bearing that slides in contact with the bull gear 20 is: It depends on the operating condition at that time.

  The output shafts 5 and 6 and the pinions 21 and 22 are supported in the radial direction by radial bearings 62 to 65. On the other hand, support of the output shafts 5 and 6 and the pinions 21 and 22 in the thrust direction is performed by thrust collars 66 to 69 configured to sandwich the bull gear 20 via gaps 71 and 72 (see FIG. 5).

  The thrust collars 66 and 67 are shrink-fitted on the output shaft 5 so as to sandwich the bull gear 20 through the gap 71 (see FIG. 5), and contact the bull gear 20 on the sliding surfaces located on the inner sides in the axial direction. It has a structure. The inter-surface distance between the sliding surface of the thrust collar 66 and the sliding surface of the thrust collar 67 is, for example, about 0.2 mm larger than the inter-surface distance between both sliding surfaces of the bull gear 20. That is, the gap 71 (see FIG. 5) on the sliding surface in the thrust direction between the bull gear 20 and the thrust collars 66 and 67 is, for example, about 0.2 mm. During steady operation of the multistage centrifugal compressor, either the thrust collar 66 or the thrust collar 67 is in contact with the sliding surface of the bull gear 20, and the sliding surface of the other thrust collar and the sliding surface of the bull gear 20 are in contact with each other. Keeps the gap. In addition, the thrust collars 66 and 67 maintain a gap of about 2 to 3 mm with the casing 101 and do not come into contact therewith. Note that the thrust collars 68 and 69 fixed to the output shaft 6 have the same structure as the thrust collars 66 and 67 fixed to the output shaft 5, and thus description thereof is omitted.

  As described above, the multistage centrifugal compressor according to this embodiment includes the input shaft 4 driven by the prime mover, the bull gear 20 provided on the input shaft 4, the pinions 21 and 22 meshing with the bull gear 20, and the pinions 21 and 22. Are provided with output shafts 5 and 6, respectively. A first-stage centrifugal impeller (first centrifugal impeller) 11 is provided at one end of the output shaft 5, and the fluid is more fluid than the first-stage centrifugal impeller 11 at the other end of the output shaft 5. A second-stage centrifugal impeller (second centrifugal impeller) 12 is provided on the downstream side of the flow of. Further, a third-stage centrifugal impeller 13 is provided at one end of the output shaft 6 and is located on the most downstream stage side of the fluid flow.

  FIG. 2 is a schematic diagram for explaining a fluid load (fluid force) acting on the first stage centrifugal impeller 11 in the thrust direction.

  As shown in FIG. 2, a first stage centrifugal impeller 11 is provided at the tip of the output shaft 5. The shroud casing 111 covers the outside of the centrifugal impeller 11, and the casing 101 covers the back surface 16 of the centrifugal impeller 11. A shaft sealing device 15 is installed between the casing 101 and the output shaft 5 to prevent the compressed fluid from leaking outside the compressor.

  Since the pressure of the fluid in the compressor is increased by the centrifugal impeller 11, the pressure on the downstream side is higher than the upstream side of the centrifugal impeller 11. Further, the pressure P1 of the fluid acting on the back surface 16 of the centrifugal impeller 11 is substantially the same as the pressure on the downstream side of the centrifugal impeller 11. Therefore, the fluid load acting on the centrifugal impeller 11 in the thrust direction is caused by the pressure P1 of the compressed fluid acting on the back surface 16 of the centrifugal impeller 11 being a dominant factor. Therefore, a fluid load Fi in the thrust direction by the centrifugal impeller 11 is generated on the output shaft 5 provided with the centrifugal impeller 11 in the direction opposite to the fluid flow direction A on the upstream side of the centrifugal impeller 11. A symbol B in FIG. 2 indicates the flow direction of the fluid on the downstream side of the centrifugal impeller 11. The fluid load acting in the thrust direction on each of the second-stage centrifugal impeller 12 and the third-stage centrifugal impeller 13 is caused by the same principle as the first-stage centrifugal impeller 11, and therefore will be described. Omitted.

  FIG. 3 is a schematic diagram for explaining the fluid load in the thrust direction generated on the output shaft 5 by the first stage centrifugal impeller 11 and the second stage centrifugal impeller 12. In FIG. 3, the pinion 21 and the like are not shown.

  As shown in FIG. 3, a first stage centrifugal impeller 11 is provided at one end of the output shaft 5, and a second stage centrifugal impeller 12 is provided at the other end of the output shaft 5. In this case, the pressure P1 of the compressed fluid acts on the back surface 16 of the centrifugal impeller 11, and the pressure P2 of the compressed fluid acts on the back surface 17 of the centrifugal impeller 12. Here, the pressure P2 of the compressed fluid acting on the back surface 17 of the downstream centrifugal impeller 12 is higher than the pressure P1 of the compressed fluid acting on the rear surface 16 of the upstream centrifugal impeller 11. This is because the fluid compressed by the centrifugal impeller 11 on the upstream stage side is further pressurized by the centrifugal impeller 12 on the downstream stage side. However, the fluid compressed by the centrifugal impeller 11 on the upstream stage side can be boosted by another centrifugal impeller (not shown) and further boosted by the centrifugal impeller 12 on the downstream stage side. is there. Thereby, the fluid load Fi1 in the thrust direction generated in the entire output shaft 5 is generated in the direction from the centrifugal impeller 11 on the upstream stage side to the centrifugal impeller 12 on the downstream stage side.

  FIG. 4 is a schematic diagram for explaining a gear load (gear force) acting in the thrust direction due to the engagement of the bull gear 20 and the pinion 21.

  FIG. 4 is a top view of how the bull gear 20 provided on the input shaft 4 and the pinion 21 provided on the output shaft 5 are engaged with each other at a portion 40 indicated by a thick line in the drawing. Here, the bull gear 20 rotates clockwise as seen from the anti-motive motor side as indicated by an arrow in the figure. Also, as shown in FIG. 4, for the reasons described later, the bull gear 20 has a left-handed helical shape whose teeth are inclined upward when viewed from the side with the axis serving as the center of rotation facing the top-to-bottom direction. The pinion 21 is a right-handed helical gear whose teeth are inclined upward when viewed from the side with the axis serving as the center of rotation directed in the vertical direction. Therefore, the pinion 21 receives the gear load Fp1 in the thrust direction from the bull gear 20 to the right. As a reaction, the bull gear 20 receives a gear load Fb in the thrust direction from the pinion 21 in the left direction. The gear load acting in the thrust direction due to the engagement between the bull gear 20 and the pinion 22 is generated by the same principle as the gear load due to the engagement between the bull gear 20 and the pinion 21, and the description thereof is omitted.

  FIG. 5 is a horizontal sectional view schematically showing the multistage centrifugal compressor according to the first embodiment.

  In FIG. 5, the casing 101, the input shaft 4, the bull gear 20, the composite bearings 60 and 61, the output shafts 5 and 6, the pinions 21 and 22, the thrust collars 66 to 69, and the centrifugal impellers 11 to 100 in the speed increasing unit 100. Only the number 13 is illustrated, and the radial bearings 62 to 65, the shaft seal device 15 and the like are not illustrated for convenience of explanation. Further, the compound bearings 60 and 61 show only a portion that receives a load in the thrust direction, and a portion that receives a load in the radial direction is omitted.

  In the present embodiment, first and second-stage centrifugal impellers 11 and 12 are provided at both ends of one of the two output shafts 5 and 6, respectively. The output shaft 5, the pinion 21, the thrust collars 66 and 67, and the centrifugal impellers 11 and 12 form a low-pressure stage pinion shaft 80. A third-stage centrifugal impeller 13 is provided at one end of the other output shaft 6. The output shaft 6, the pinion 22, the thrust collars 68 and 69, and the centrifugal impeller 13 form a high-pressure stage pinion shaft 81. In FIG. 5, in order to facilitate understanding of the operating state of the multistage centrifugal compressor, the thrust shaft gap 70 between the input shaft 4 and the bull gear 20 and the composite bearings 60 and 61, the bull gear 20 and the thrust collars 66 and 67. The thrust direction gap 71 between them and the thrust direction gap 72 between the bull gear 20 and the thrust collars 68, 69 are exaggerated and enlarged.

  The thrust-direction fluid load Fi2 generated on the high-pressure stage pinion shaft 81 is larger than the thrust-direction fluid load Fi1 generated on the low-pressure stage pinion shaft 80. This is because the thrust-direction fluid load Fi1 generated in the low-pressure stage pinion shaft 80 is equal to the pressure P1 (see FIG. 3) acting on the back surface 16 of the first stage centrifugal impeller 11 and the second stage centrifugal impeller 12. This is because the direction of the pressure P2 (see FIG. 3) acting on the back surface 17 is the opposite direction and cancels each other. Further, the pressure acting on the back surface of the third stage centrifugal impeller 13 is higher than the pressures P1 and P2 acting on the back surfaces 16 and 17 of the first and second stage centrifugal impellers 11 and 12. . Therefore, the helical direction of the helical gears of the bull gear 20 and the pinions 21 and 22 of the multi-stage centrifugal compressor is set considering firstly the thrust load generated on the high-pressure stage pinion shaft 81.

  In the present embodiment, the fluid load Fi2 in the thrust direction generated on the high-pressure stage pinion shaft 81 is generated in the direction from the prime mover side to the counter prime mover side. Therefore, in order to cancel out the fluid load Fi2, the twist direction of the helical gears of the bull gear 20 and the pinion 22 is determined so that the gear load Fp2 is generated in the direction from the anti-motor side to the motor side. In the present embodiment, the input shaft 4 and the bull gear 20 rotate clockwise as viewed from the counter prime mover side. Therefore, the bull gear 20 must be a left-twisted helical gear, and the pinion 22 of the high-pressure stage pinion shaft 81 must be a right-twisted helical gear. On the other hand, the pinion 21 of the low-pressure stage pinion shaft 80 is uniquely a right-handed helical gear, and the gear load Fp1 is generated in the direction from the anti-motor side to the motor side. Further, as described above, the direction of the fluid load Fi1 in the thrust direction generated in the low-pressure stage pinion shaft 80 is the direction from the anti-motor side to the prime mover side (see FIG. 3).

  The thrust load generated on the low-pressure stage pinion shaft 80 is the resultant force of the thrust-direction gear load Fp1 received from the bull gear 20 by the pinion 21 of the low-pressure stage pinion shaft 80 and the thrust-direction fluid load Fi1 acting on the low-pressure stage pinion shaft 80. is there. Therefore, the thrust load acting on the low-pressure stage pinion shaft 80 is in the direction from the anti-motor side to the prime mover side, and is supported by the thrust collar 66.

  On the other hand, the thrust load generated on the high-pressure stage pinion shaft 81 is a thrust-direction gear load Fp2 received by the pinion 22 of the high-pressure stage pinion shaft 81 from the bull gear 20 and a thrust-direction fluid load Fi2 acting on the high-pressure stage pinion shaft 81. It is a power. Since the fluid load Fi2 is usually considerably larger than the gear load Fp2, the thrust load acting on the high-pressure stage pinion shaft 81 is in the direction from the prime mover side to the anti-prime mover side and is supported by the thrust collar 69.

  The thrust load acting on the bull gear 20 is a combined load F of the thrust load received from the thrust collar 66 of the low-pressure stage pinion shaft 80 and the thrust load received from the thrust collar 69 of the high-pressure stage pinion shaft 81. Here, the thrust load acting on the high-pressure stage pinion shaft 81 is larger than the thrust load acting on the low-pressure stage pinion shaft 80. Therefore, the entire gear system including the low-pressure stage pinion shaft 80, the high-pressure stage pinion shaft 81, and the bull gear 20 receives a thrust load (synthetic load F) in the direction from the prime mover side to the anti-prime mover side.

  In this way, the entire gear system of the multistage centrifugal compressor according to this embodiment receives a thrust load in the left direction of FIG. As a result, an operating state as shown in FIG. 5 is obtained. That is, the thrust load of the entire gear system is supported by the composite bearing 61 on the anti-motor side. The thrust load acting on the low-pressure stage pinion shaft 80 is supported by contact / sliding of the thrust collar 66 and the bull gear 20 on the first stage centrifugal impeller 11 side. Further, the thrust load acting on the high-pressure stage pinion shaft 81 is supported by contact / sliding of the thrust collar 69 and the bull gear 20 opposite to the third stage centrifugal impeller 13.

  Here, if the fluid load Fi1 in the thrust direction generated on the low-pressure stage pinion shaft 80 can be reduced, the contact surface pressure at the contact / sliding surface between the thrust collar 66 of the low-pressure stage pinion shaft 80 and the bull gear 20 is reduced. As a result, friction loss is reduced and the efficiency of the entire multistage centrifugal compressor is improved.

In the present embodiment, in order to reduce the fluid load Fi1 in the thrust direction generated in the low-pressure stage pinion shaft 80, the outer diameter D1 (see also FIGS. 2 and 3) of the first stage centrifugal impeller 11 is two stages. It is set larger than the outer diameter D2 (see also FIG. 3) of the centrifugal impeller 12 of the eye. The ratio of the outer diameter D2 of the second-stage centrifugal impeller 12 to the outer diameter D1 of the first-stage centrifugal impeller 11, that is, the outer diameter ratio (D2 / D1) is 0.8 or more and less than 1.0. It is preferable that it is set.

Next, the function and effect of the multistage centrifugal compressor configured as described above will be described.
In the present embodiment, the outer diameter D1 of the first stage centrifugal impeller 11 is made larger than the outer diameter D2 of the second stage centrifugal impeller 12. Therefore, the pressure receiving area of the pressure P1 of the fluid acting on the back surface 16 of the first stage centrifugal impeller 11 is increased, so that the first stage centrifugal impeller 11 is moved in the thrust direction from the prime mover side to the counter prime mover side. The acting fluid load increases. Further, when the outer diameter D1 of the first stage centrifugal impeller 11 is increased, the pressure increase in the first stage compressor section 1 is increased, so the pressure increase in the second stage compressor section 2 is decreased. be able to. That is, the outer diameter D2 of the second stage centrifugal impeller 12 can be reduced. As a result, the pressure receiving area of the pressure P2 acting on the back surface 17 of the second-stage centrifugal impeller 12 is reduced, thereby acting on the second-stage centrifugal impeller 12 in the thrust direction from the anti-motor side to the prime mover side. Fluid load to be reduced.

Accordingly, the fluid load in the thrust direction from the anti-motor side to the motor side acting on the low-pressure stage pinion shaft 80 by the first stage centrifugal impeller 11 and the second stage centrifugal impeller 12 becomes relatively small. That is, the thrust load generated on the output shaft 5 is reduced.
Thereby, the friction loss in the contact / sliding portion between the thrust collar 66 and the bull gear 20 is reduced, and the efficiency of the multistage centrifugal compressor is improved. Further, the mechanical reliability of the thrust collar 66 that is shrink-fitted on the output shaft 5 is improved, and the amount of wear on the sliding surface of the thrust collar 66 and the bull gear 20 is reduced. Reliability is also improved.
That is, according to the present embodiment, it is possible to provide a multistage centrifugal compressor with high efficiency and high mechanical reliability by reducing the thrust load generated on the output shaft 5.

In the present embodiment, the ratio of the outer diameter D2 of the second stage centrifugal impeller 12 to the outer diameter D1 of the first stage centrifugal impeller 11 is preferably set to be 0.8 or more and less than 1.0. Yes.

  FIG. 6 shows the ratio of the outer diameter D2 of the second stage centrifugal impeller 12 to the outer diameter D1 of the first stage centrifugal impeller 11, that is, the outer diameter ratio (D2 / D1) and the first stage centrifugal impeller 11. It is a figure which shows the relationship with the stress (sigma) which generate | occur | produces in the blade root C (refer FIG. 2) in the exit part. Here, the stress generated in the centrifugal impeller 11 by the centrifugal force becomes maximum at the blade root C.

  From the viewpoint of reducing the fluid load in the thrust direction acting on the low-pressure stage pinion shaft 80, the outer diameter D1 of the first stage centrifugal impeller 11 is as large as possible. The diameter D2 is preferably as small as possible. That is, from the viewpoint of reducing the thrust load acting on the output shaft 5, the outer diameter ratio (D2 / D1) is preferably as small as possible. However, as shown in FIG. 6, as the outer diameter ratio (D2 / D1) decreases, the stress σ due to the centrifugal force generated at the blade root C at the outlet of the first stage centrifugal impeller 11 increases. When the outer diameter ratio (D2 / D1) is less than 0.8, the allowable value (allowable stress) of the material is exceeded. For example, stainless steel is used as the material of the centrifugal impeller. The conventional value shown in FIG. 6 is a stress value generated when the outer diameter ratio (D2 / D1) = 1.

From FIG. 6, the outer diameter D1 of the first stage centrifugal impeller 11 is set to the second stage centrifugal impeller as long as the stress σ does not exceed the allowable value of the material unless the conditions regarding the strength of the material and the like are changed. In order to make it larger than the outer diameter D2 of 12, it is understood that the outer diameter ratio (D2 / D1) should be 0.8 or more and less than 1.0. If comprised in this way, while suppressing the increase in the stress which generate | occur | produces in the centrifugal impeller 11, the thrust load which generate | occur | produces in the output shaft 5 is reduced, and a highly efficient and highly reliable mechanical multistage centrifugal compressor is provided. be able to.

  In the present embodiment, the bull gear 20 and the pinions 21 and 22 are helical gears. The bull gear 20 and the gear load Fp2 acting in the axial direction on the pinion 22 are opposite to the fluid load Fi2 acting in the thrust direction on the third stage centrifugal impeller 13 located on the most downstream side. The helical direction of the helical gears of the pinions 21 and 22 is set.

  If comprised in this way, while using a helical gear, vibration and noise can be reduced, the fluid load Fi2 and the gear load Fp2 cancel each other, and the output provided with the most downstream centrifugal impeller 13 The thrust load generated on the shaft 6 can be reduced. Thereby, the friction loss in the contact / sliding portion between the thrust collar 69 and the bull gear 20 is reduced, and the efficiency of the multistage centrifugal compressor is improved. Further, the mechanical reliability of the thrust collar 69 and the bull gear 20 that are shrink-fitted on the output shaft 6 is improved, and the amount of wear on the sliding surfaces of the thrust collar 69 and the bull gear 20 is reduced. Further, since the thrust load (combined load F) generated in the entire gear system is reduced, the friction loss at the contact / sliding portion between the bull gear 20 and the composite bearing 61 is also reduced. Therefore, the mechanical reliability of the multistage centrifugal compressor can be further increased.

[Second Embodiment]
Next, with reference to FIG. 7, the second embodiment of the present invention will be described with a focus on differences from the first embodiment described above, and description of common points will be omitted as appropriate.
FIG. 7 is a horizontal sectional view schematically showing the multistage centrifugal compressor according to the second embodiment.

  As shown in FIG. 7, the multistage centrifugal compressor according to the second embodiment is different from the first embodiment, which is a three-stage compressor, in that it is a four-stage compressor. That is, a third stage centrifugal impeller 13 is provided at one end of the output shaft 6, and a fourth stage centrifugal blade located at the most downstream stage side of the fluid flow is provided at the other end of the output shaft 6. A car 14 is provided.

  In the second embodiment, similarly to the first embodiment, the outer diameter D1 of the first stage centrifugal impeller 11 is set larger than the outer diameter D2 of the second stage centrifugal impeller 12. The outer diameter D3 of the third-stage centrifugal impeller 13 is set larger than the outer diameter D4 of the fourth-stage centrifugal impeller 14. Therefore, the fluid load Fi1 in the thrust direction acting on the output shaft 5 by the first-stage centrifugal impeller 11 and the second-stage centrifugal impeller 12 becomes relatively small, and the thrust load generated on the output shaft 5 is reduced. The The third-stage centrifugal impeller 13 and the fourth-stage centrifugal impeller 14 relatively reduce the thrust-direction fluid load Fi2 acting on the output shaft 6, and the thrust load generated on the output shaft 6 is reduced. The

  In the second embodiment, the gear load Fp2 acting on the pinion 22 in the axial direction is the same as the fluid load acting on the fourth stage centrifugal impeller 14 located on the most downstream side in the thrust direction. In addition, the twist direction of the helical gears of the bull gear 20 and the pinions 21 and 22 is set. This is based on the premise that the same bull gear and pinion as in the first embodiment are used. Here, the fluid load acting on the fourth stage centrifugal impeller 14 in the thrust direction is larger than the fluid load acting on the third stage centrifugal impeller 13 in the thrust direction. For this reason, the direction of the fluid load Fi2 in the thrust direction acting on the output shaft 6 as a whole is the same as the direction of the fluid load acting in the thrust direction on the fourth stage centrifugal impeller 14, and from the anti-motor side to the motor side Is the direction to.

  As described above, according to the second embodiment, the present invention can be applied to a four-stage compressor, and the same effects as those of the first embodiment can be obtained.

[Third Embodiment]
Next, with reference to FIG. 8, the third embodiment of the present invention will be described with a focus on differences from the second embodiment described above, and description of common points will be omitted as appropriate.
FIG. 8 is a horizontal sectional view schematically showing the multistage centrifugal compressor according to the third embodiment.

  As shown in FIG. 8, the multistage centrifugal compressor according to the third embodiment is different from the second embodiment in that the twisting directions of the bull gear and the pinion are opposite. That is, the bull gear is a right-handed helical gear, and the pinion is a left-handed helical gear.

  In the third embodiment, as in the second embodiment, the outer diameter D1 of the first stage centrifugal impeller 11 is set larger than the outer diameter D2 of the second stage centrifugal impeller 12. The outer diameter D3 of the third-stage centrifugal impeller 13 is set larger than the outer diameter D4 of the fourth-stage centrifugal impeller 14. Therefore, the fluid load Fi1 in the thrust direction acting on the output shaft 5 by the first-stage centrifugal impeller 11 and the second-stage centrifugal impeller 12 becomes relatively small, and the thrust load generated on the output shaft 5 is reduced. The The third-stage centrifugal impeller 13 and the fourth-stage centrifugal impeller 14 relatively reduce the thrust-direction fluid load Fi2 acting on the output shaft 6, and the thrust load generated on the output shaft 6 is reduced. The

  In the third embodiment, the gear load Fp2 acting on the pinion 22 in the axial direction is opposite to the fluid load acting on the fourth stage centrifugal impeller 14 located on the most downstream side in the thrust direction. In addition, the twist direction of the helical gears of the bull gear 20 and the pinions 21 and 22 is set. Here, the fluid load acting on the fourth stage centrifugal impeller 14 in the thrust direction is larger than the fluid load acting on the third stage centrifugal impeller 13 in the thrust direction. For this reason, the direction of the fluid load Fi2 in the thrust direction acting on the output shaft 6 as a whole is the same as the direction of the fluid load acting in the thrust direction on the fourth stage centrifugal impeller 14, and from the anti-motor side to the motor side Is the direction to. Therefore, in the third embodiment, the bull gear 20 is a right-handed helical gear, and the pinions 21 and 22 are left-handed helical gears. Thereby, the fluid load Fi2 and the gear load Fp2 cancel each other, and the thrust load generated on the output shaft 6 including the centrifugal impeller 14 at the most downstream stage can be reduced. In the third embodiment, the gear load Fp1 acting on the pinion 21 in the axial direction is opposite to the fluid load acting on the second stage centrifugal impeller 12 in the thrust direction. Thereby, the fluid load Fi1 and the gear load Fp1 cancel each other, and the thrust load generated in the output shaft 5 including the second stage centrifugal impeller 12 can be reduced.

[Fourth Embodiment]
Next, with reference to FIG. 9, the fourth embodiment of the present invention will be described with a focus on differences from the second embodiment described above, and description of common points will be omitted as appropriate.
FIG. 9 is a horizontal cross-sectional view schematically showing a multistage centrifugal compressor according to the fourth embodiment.

  As shown in FIG. 9, the multistage centrifugal compressor according to the fourth embodiment is different from the second embodiment in that the positions where the third stage impeller 13 and the fourth stage impeller 14 are provided are reversed. It is different.

  In the fourth embodiment, similarly to the second embodiment, the outer diameter D1 of the first stage centrifugal impeller 11 is set larger than the outer diameter D2 of the second stage centrifugal impeller 12. The outer diameter D3 of the third-stage centrifugal impeller 13 is set larger than the outer diameter D4 of the fourth-stage centrifugal impeller 14. Therefore, the fluid load Fi1 in the thrust direction acting on the output shaft 5 by the first-stage centrifugal impeller 11 and the second-stage centrifugal impeller 12 becomes relatively small, and the thrust load generated on the output shaft 5 is reduced. The The third-stage centrifugal impeller 13 and the fourth-stage centrifugal impeller 14 relatively reduce the thrust-direction fluid load Fi2 acting on the output shaft 6, and the thrust load generated on the output shaft 6 is reduced. The

In the fourth embodiment, the gear load Fp2 acting on the pinion 22 in the axial direction is opposite to the fluid load acting on the fourth stage centrifugal impeller 14 located on the most downstream side in the thrust direction. In addition, the twist direction of the helical gears of the bull gear 20 and the pinions 21 and 22 is set. Here, the fluid load acting on the fourth stage centrifugal impeller 14 in the thrust direction is larger than the fluid load acting on the third stage centrifugal impeller 13 in the thrust direction. For this reason, the direction of the fluid load Fi2 in the thrust direction acting on the output shaft 6 as a whole is the same as the direction of the fluid load acting in the thrust direction on the fourth stage centrifugal impeller 14, and from the prime mover side to the anti prime mover side Is the direction to. Therefore, in the fourth embodiment, the bull gear 20 is a right-handed helical gear, and the pinions 21 and 22 are left-handed helical gears. Thereby, the fluid load Fi2 and the gear load Fp2 cancel each other, and the thrust load generated on the output shaft 6 including the centrifugal impeller 14 at the most downstream stage can be reduced.
In the fourth embodiment, the fluid load acting in the axial direction on the fourth stage centrifugal impeller 14 located on the most downstream stage side is the fluid load acting on the second stage centrifugal impeller 12 in the axial direction. The opposite direction. Thereby, similarly to 1st Embodiment, the fluid load Fi1 and the fluid load Fi2 mutually cancel each other, and the thrust load which generate | occur | produces in the input shaft 4 can be made small.

[Fifth Embodiment]
Next, with reference to FIG. 10, the fifth embodiment of the present invention will be described with a focus on differences from the first embodiment described above, and descriptions of common points will be omitted as appropriate.
FIG. 10 is a horizontal sectional view schematically showing a multistage centrifugal compressor according to the fifth embodiment.

  As shown in FIG. 10, the multistage centrifugal compressor according to the fifth embodiment is different from the first embodiment, which is a three-stage compressor, in that it is a two-stage compressor. That is, the first embodiment includes two output shafts 5 and 6, whereas the fifth embodiment includes one output shaft 5.

  In the fifth embodiment, as in the first embodiment, the outer diameter D1 of the first stage centrifugal impeller 11 is set larger than the outer diameter D2 of the second stage centrifugal impeller 12. Therefore, the fluid load Fi1 in the thrust direction acting on the output shaft 5 by the first-stage centrifugal impeller 11 and the second-stage centrifugal impeller 12 becomes relatively small, and the thrust load generated on the output shaft 5 is reduced. The

  In the fifth embodiment, the gear load Fp1 acting on the pinion 21 in the axial direction is the same as the fluid load acting on the second centrifugal impeller 12 positioned on the most downstream side in the thrust direction. In addition, the helical direction of the helical gear of the bull gear 20 and the pinion 21 is set. This is based on the premise that the same bull gear and pinion as in the first embodiment are used. Here, the fluid load acting on the second stage centrifugal impeller 12 in the thrust direction is larger than the fluid load acting on the first stage centrifugal impeller 11 in the thrust direction. Therefore, the direction of the fluid load Fi1 in the thrust direction acting on the output shaft 5 as a whole is the same as the direction of the fluid load acting in the thrust direction on the second stage centrifugal impeller 12, and from the anti-motor side to the motor side Is the direction to.

  As described above, according to the fifth embodiment, the present invention can also be applied to the two-stage compressor, and the same effect as in the first embodiment can be obtained.

[Sixth Embodiment]
Next, with reference to FIG. 11, the sixth embodiment of the present invention will be described with a focus on differences from the fifth embodiment described above, and descriptions of common points will be omitted as appropriate.
FIG. 11 is a horizontal sectional view schematically showing a multistage centrifugal compressor according to the sixth embodiment.

  As shown in FIG. 11, the multistage centrifugal compressor according to the sixth embodiment is different from the fifth embodiment in that the twisting directions of the bull gear and the pinion are opposite. That is, the bull gear is a right-handed helical gear, and the pinion is a left-handed helical gear.

  In the sixth embodiment, similarly to the fifth embodiment, the outer diameter D1 of the first stage centrifugal impeller 11 is set larger than the outer diameter D2 of the second stage centrifugal impeller 12. Therefore, the fluid load Fi1 in the thrust direction acting on the output shaft 5 by the first-stage centrifugal impeller 11 and the second-stage centrifugal impeller 12 becomes relatively small, and the thrust load generated on the output shaft 5 is reduced. The

  In the sixth embodiment, the gear load Fp1 acting on the pinion 21 in the axial direction is opposite to the fluid load acting on the second stage centrifugal impeller 12 located on the most downstream side in the thrust direction. In addition, the helical direction of the helical gear of the bull gear 20 and the pinion 21 is set. Here, the fluid load acting on the second stage centrifugal impeller 12 in the thrust direction is larger than the fluid load acting on the first stage centrifugal impeller 11 in the thrust direction. Therefore, the direction of the fluid load Fi1 in the thrust direction acting on the output shaft 5 as a whole is the same as the direction of the fluid load acting in the thrust direction on the second stage centrifugal impeller 12, and from the anti-motor side to the motor side Is the direction to. Therefore, in the sixth embodiment, the bull gear 20 is a right-handed helical gear, and the pinion 21 is a left-handed helical gear. Thereby, the fluid load Fi1 and the gear load Fp1 cancel each other, and the thrust load generated in the output shaft 5 including the centrifugal impeller 12 at the most downstream stage can be reduced.

  As mentioned above, although this invention was demonstrated based on embodiment, this invention is not limited to above-described embodiment, Various modifications are included. For example, the above-described embodiment has been described in detail for easy understanding of the present invention, and is not necessarily limited to one having all the configurations described. Further, a part of the configuration of an embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of an embodiment. In addition, it is possible to add, delete, and replace other configurations for a part of the configuration of each embodiment.

  For example, in the above-described embodiment, the case where the multistage centrifugal compressor is a 2-4 stage compressor has been described, but the present invention is not limited to these. That is, the present invention can be applied to a multistage centrifugal compressor including an input shaft driven by a prime mover and provided with a bull gear, and one or more output shafts provided with a pinion meshing with the bull gear. It is applicable also to a multistage centrifugal compressor.

4 Input shaft 5 Output shaft 6 Output shaft (second output shaft)
11 First-stage centrifugal impeller 12 Second-stage centrifugal impeller 13 Third-stage centrifugal impeller 14 Fourth-stage centrifugal impeller 20 Bull gear 21 Pinion 22 Pinion (second pinion)
60, 61 Compound bearing 66-69 Thrust collar D1-D4 Outer diameter Fi1, Fi2 Fluid load Fp1, Fp2 Gear load

Claims (2)

An input shaft driven by a prime mover;
A bull gear provided on the input shaft;
A pinion meshing with the bull gear;
An output shaft provided with the pinion;
A first centrifugal impeller provided at one end of the output shaft;
A second centrifugal impeller provided at the other end of the output shaft and positioned on the downstream side of the fluid flow with respect to the first centrifugal impeller;
A second pinion meshing with the bull gear;
A second output shaft provided with the second pinion;
A third centrifugal impeller provided on the second output shaft and positioned on the most downstream stage side of the fluid flow of the second centrifugal impeller ,
The outer diameter of the first centrifugal impeller is set larger than the outer diameter of the second centrifugal impeller ,
The third centrifugal impeller is provided at an end portion opposite to the second centrifugal impeller in the axial direction of the second output shaft,
The bull gear, the pinion, and the second pinion are helical gears,
The gear load acting in the axial direction on the pinion is the same direction as the fluid load acting in the axial direction on the second centrifugal impeller, and the gear load acting on the second pinion in the axial direction is The helical direction of the helical gear is set to be opposite to the fluid load acting in the axial direction on the third centrifugal impeller,
The multistage centrifugal compressor characterized in that the fluid load acting in the axial direction on the third centrifugal impeller is opposite to the fluid load acting in the axial direction on the second centrifugal impeller . 2. The multistage centrifugal according to claim 1, wherein a ratio of an outer diameter of the second centrifugal impeller to an outer diameter of the first centrifugal impeller is set to be 0.8 or more and less than 1.0. Compressor.

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