Screw compressor and gas compression facility

Abstract

To provide a screw compressor and gas compression facility capable of suppressing discharge loss over an operation region of wide range (range of internal volume ratio).SOLUTION: A screw compressor includes: a slide valve of which a position in an axial direction of a screw rotor is variable to change a volume ratio; and a movable piece disposed along an edge of an opening of a casing and constituted so that it can close a part of the opening. The movable piece is constituted movably between a first position where the movable piece forms a first contour of an axial discharge port with the edge of the opening, and a second position separating from the screw rotor in the axial direction with respect to the first position. When the movable piece is located on the second position, a second contour of the axial discharge port having an opening area larger than that of the first contour is formed by the opening.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present disclosure relates to screw compressors and gas compression equipment. [Background technology]

[0002] A positive displacement screw compressor has excellent advantages such as a simple structure and good durability, and is therefore widely used. Representative methods of capacity control in a screw compressor include a rotation speed control method and a slide valve method, and in large screw compressors, the slide valve method of capacity control is generally adopted.

[0003] In the slide valve system, the volume of the tooth groove space formed between the male rotor and the female rotor at the start of compression can be changed by axially moving the slide valve, which forms the rotor chamber together with the casing, making it possible to continuously adjust the volume of gas to be compressed according to the load of the screw compressor. On the other hand, screw compressors have a volume ratio Vi (=suction volume V1 / discharge volume V2) that is suitable for the operating conditions, and the positions and shapes of the suction port and discharge port are determined so that the discharge of the compressed gas begins at a timing corresponding to the volume ratio Vi that is suitable for the operating conditions. Most existing screw compressors have a fixed internal volume ratio Vi, and therefore have a discharge port with a shape selected for the average internal volume ratio. However, in a screw compressor equipped with the above-mentioned slide valve, the internal volume ratio (the ratio of the volume at the start of compression of the tooth groove space (start of volume reduction) to that at the end of compression (end of volume reduction)) also changes at the same time when the slide valve is moved.

[0004] Patent Document 1 describes a screw compressor that includes the above-mentioned slide valve and is capable of adjusting the internal volume ratio. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] International Publication No. 2016 / 147467 Summary of the Invention [Problem to be solved by the invention]

[0006] However, when trying to increase the size of a screw compressor while maintaining the internal volume ratio of the discharge port, the area ratio of the discharge port to the displacement decreases, and the gas flow rate at the discharge port increases. When the gas flow rate at the discharge port increases in this way, the pressure in the tooth groove space increases due to the passage resistance at the discharge port, causing overcompression, which may increase the discharge loss.

[0007] On the other hand, by increasing the area of ​​the discharge port (low internal volume ratio), the increase in gas flow rate at the discharge port can be suppressed, making the problem of increased discharge loss as described above less likely to occur. However, in an operating range requiring a high internal volume ratio, gas that flows back from the discharge side due to insufficient compression is recompressed and discharged, which may still increase the discharge loss.

[0008] In view of the above circumstances, an object of at least one embodiment of the present invention is to provide a screw compressor and gas compression equipment capable of suppressing discharge loss over a wide operating range (range of internal volume ratio). [Means for solving the problem]

[0009] At least one embodiment of the screw compressor according to the present invention comprises: a screw rotor having a discharge side end surface; a casing having a rotor-opposing surface facing the discharge end surface, and an opening provided on the rotor-opposing surface and communicating with a discharge space into which gas compressed by the screw rotor is discharged; a slide valve whose position in the axial direction of the screw rotor is variable so as to change the internal volume ratio; a movable piece provided along an edge of the opening of the casing and configured to be capable of closing a part of the opening; Equipped with the movable piece is configured to be movable between a first position where the movable piece forms a first contour of the axial discharge port together with an edge of the opening, and a second position that is farther from the screw rotor in the axial direction than the first position, When the movable piece is located at the second position, the opening forms a second contour of the axial discharge port having an opening area larger than the first contour.

[0010] In addition, the gas compression equipment according to at least one embodiment of the present invention includes: a screw compressor as described above configured to compress a gas; an oil separator for separating the oil from a mixture of compressed gas and oil discharged from the screw compressor; Equipped with. Effect of the Invention

[0011] According to at least one embodiment of the present invention, there is provided a screw compressor and a gas compression facility capable of suppressing discharge loss over a wide operating range (range of internal volume ratio). [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a schematic diagram of a gas compression facility according to one embodiment. [Diagram 2] 1 is a schematic cross-sectional side view of a screw compressor according to one embodiment. FIG. [Diagram 3] FIG. 3 is a view showing a cross section taken along line AA of the screw compressor shown in FIG. 2. [Figure 4] FIG. 2 is a schematic cross-sectional view showing the vicinity of an axial discharge port of a screw compressor according to one embodiment. [Diagram 5] FIG. 5 is a schematic diagram showing the contour of the axial discharge port shown in FIG. 4. [Figure 6] FIG. 2 is a schematic cross-sectional view showing the vicinity of an axial discharge port of a screw compressor according to one embodiment. [Figure 7] FIG. 7 is a schematic diagram showing the contour of the axial discharge port shown in FIG. 6. [Figure 8] FIG. 2 is a schematic cross-sectional view showing the vicinity of an axial discharge port of a screw compressor according to one embodiment. [Figure 9] FIG. 9 is a schematic diagram showing the contour of the axial discharge port shown in FIG. 8. [Figure 10] FIG. 2 is a schematic cross-sectional view showing the vicinity of an axial discharge port of a screw compressor according to one embodiment. [Figure 11] FIG. 11 is a schematic diagram showing the contour of the axial discharge port shown in FIG. [Figure 12] FIG. 2 is a schematic cross-sectional view showing the vicinity of an axial discharge port of a screw compressor according to one embodiment. [Figure 13] FIG. 2 is a schematic cross-sectional view showing the vicinity of an axial discharge port of a screw compressor according to one embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, some embodiments of the present invention will be described with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements, etc. of components described as the embodiments or shown in the drawings are merely illustrative examples and are not intended to limit the scope of the present invention.

[0014] (Gas Compression Equipment Configuration) 1 is a schematic diagram of a gas compression facility including a screw compressor according to some embodiments. As shown in the figure, the gas compression facility 1 includes a screw compressor 2, an oil separator 4, a cooler 6, and a pump 8.

[0015] The screw compressor 2 is configured to compress and discharge the sucked gas. In the drawing, the symbol Ps indicates the suction pressure of the screw compressor 2, and the symbol Pd indicates the discharge pressure of the screw compressor 2. Oil is supplied to the screw compressor 2 via an oil supply line 10 for cooling, lubrication, etc. The oil supplied to the screw compressor 2 is discharged together with the compressed gas.

[0016] The oil separator 4 is configured to separate oil from a mixture of compressed gas and oil discharged from the screw compressor 2. The oil separated in the oil separator 4 is supplied again to the screw compressor 2 via an oil supply line 10. Typically, the oil separated in the oil separator 4 is pressurized by a pump 8 and then supplied to the screw compressor 2 via the oil supply line 10. In this case, the pressure Poil of the oil supplied to the screw compressor 2 is higher than the discharge pressure Pd (Poil=Pd+α). The oil separated in the oil separator 4 may be cooled in a cooler 6 and then pressurized by the pump 8.

[0017] (Screw Compressor Configuration) Fig. 2 is a schematic cross-sectional side view of a screw compressor according to one embodiment. Fig. 3 is a view showing a cross section taken along line AA of the screw compressor shown in Fig. 2. As shown in Figs. 2 and 3, the screw compressor 2 includes a pair of screw rotors (a male rotor 15 and a female rotor 17) including a pair of rotor shafts 14, 16, and a casing 12 that houses the pair of screw rotors.

[0018] The pair of rotor shafts 14, 16 are rotatably supported by a radial bearing 18 and a thrust bearing 20. Oil under pressure is supplied to each bearing via an oil supply line 10.

[0019] The male rotor 15 and the female rotor 17 have helical teeth that mesh with each other. A plurality of tooth gap spaces are formed along the axial direction of the rotor shafts 14, 16 by the meshing of the teeth of the male rotor 15 and the female rotor 17 and the casing 12.

[0020] The rotor shaft 14 that constitutes the male rotor 15 is connected to the output shaft of a motor (not shown) and is configured to be rotated and driven by the motor. The female rotor 17 that meshes with the male rotor 15 is rotated and driven by the rotation of the male rotor 15. The female rotor 17 rotates in the opposite direction to the rotation of the male rotor 15. When the male rotor 15 and the female rotor 17 rotate in the meshed state, the cutting edge groove space moves in the axial direction from the suction side to the discharge side.

[0021] A shaft seal 24 for suppressing leakage of gas through the penetration part of the casing 12 by the rotor shaft 14 is provided at the penetration part. Oil under pressure Poil may be supplied to the shaft seal 24 through the oil supply line 10.

[0022] The oil supplied to the bearings and the shaft seal portion 24 is discharged from the casing 12 and returned to a relatively low-pressure space in the screw rotor accommodating portion of the casing 12 via a return line (not shown).

[0023] Gas is sucked into the tooth groove space from the suction space 41 formed in the casing 12 through the suction port 40. When the male rotor 15 and the female rotor 17 rotate, the tooth groove space moves in the axial direction from the suction side to the discharge side in accordance with the rotation of these screw rotors. In this process, when the volume of the tooth groove space reaches its maximum, the suction port 40 is closed and the volume of the tooth groove space is reduced, so that the gas in the tooth groove space is compressed. When the tooth groove space reaches the discharge port 42 and the tooth groove space communicates with the discharge space 43 formed in the casing 12, the compressed gas in the tooth groove space is discharged to the discharge space through the discharge port 42. The discharge port 42 will be described in detail later, but includes a radial discharge port 46 for discharging the compressed gas from the tooth groove space in the radial direction and an axial discharge port 44 for discharging the compressed gas from the tooth groove space in the axial direction.

[0024] As shown in FIG. 2, the screw compressor 2 may include a balance piston 28 provided on at least one of the pair of rotor shafts 14, 16. In the exemplary embodiment shown in FIG. 2, the balance piston 28 is provided on the suction side end of the rotor shaft 14 constituting the male rotor 15. A relatively high-pressure oil is supplied from the oil supply line 10 to a balance piston chamber 29 facing the suction side end face of the balance piston 28. As a result, a force (a force in the axial direction from the suction side to the discharge side) in the opposite direction to the thrust gas load acting on the rotor shaft 14 (a thrust load acting on the rotor shaft 14 in the axial direction from the discharge side to the suction side due to the difference between the suction pressure Ps and the discharge pressure Pd of the screw compressor 2) acts on the rotor shaft 14 via the end face of the balance piston 28. As a result, the load on the thrust bearing 20 can be reduced.

[0025] 2, the screw compressor 2 is provided with a slide valve 30 for adjusting the capacity according to the load of the screw compressor 2. In the illustrated embodiment, the slide valve 30 is driven by a hydraulic piston 32 and is capable of changing its axial position.

[0026] When the slide valve 30 is moved from the suction side to the discharge side in the axial direction, the bypass passage opens facing the tooth groove space during the compression stroke, and the gas in the tooth groove space is returned to the suction chamber with the rotation of the screw rotor, and the compression in the tooth groove space starts when the bypass passage is closed. The more the slide valve moves to the discharge side, the smaller the tooth groove space volume at the start of compression. In this way, by changing the axial position of the slide valve 30, the volume Vs at the start of compression of each tooth groove space (i.e., when the volume reduction of each tooth groove space starts and the suction port 40 is closed) can be changed. This changes the internal volume ratio Vi of the screw compressor 2 (the ratio Vs / Vd of the volume Vs at the start of compression in the tooth groove space and the volume Vd at the end of compression (when the volume reduction of the tooth groove space ends and the discharge port 42 is opened)). In other words, the more the slide valve 30 is positioned on the discharge side, the smaller the tooth groove space volume Vs at the start of compression. For this reason, the positioning of the slide valve 30 closer to the discharge side is a factor in the reduction of the internal volume ratio Vi (=Vs / Vd).

[0027] The discharge ports 42 include the radial discharge port 46 and the axial discharge port 44, as described above.

[0028] The radial discharge port 46 is formed by the notch 31 of the slide valve 30. The opening area of ​​the radial discharge port 46 is maximum when the slide valve 30 is located at the suction side in the axial direction, and becomes smaller as the position of the slide valve 30 approaches the discharge side. When the slide valve 30 reaches a predetermined axial position, the radial discharge port 46 is closed, and the opening area of ​​the radial discharge port 46 becomes zero. The smaller the opening area of ​​the radial discharge port 46, the smaller the volume Vd at the timing when the discharge port 42 opens for each tooth groove space. Therefore, the fact that the opening area of ​​the radial discharge port 46 becomes smaller by moving the slide valve 30 to the discharge side is a factor in the increase of the internal volume ratio Vi (=Vs / Vd).

[0029] The axial discharge port 44 is at least partially defined by an opening 52 (see FIG. 3) provided in the end face of the casing 12. The opening 52 is provided in a rotor-opposing surface 50 (end face of the casing 12) of the casing 12 that faces the discharge-side end face 48 of the screw rotors (the male rotor 15 and the female rotor 17) so as to communicate with the discharge space 43.

[0030] Here, Fig. 4 and Fig. 6 are schematic cross-sectional views showing the vicinity of the axial discharge port 44 of the screw compressor according to one embodiment, and are views corresponding to the BB cross section of Fig. 3. Fig. 5 and Fig. 7 are schematic views showing the contour of the axial discharge port 44 shown in Fig. 4 and Fig. 6, respectively. Fig. 8 to Fig. 11 are views showing the vicinity of the axial discharge port 44 of the screw compressor according to another embodiment, and are views corresponding to Fig. 4 to Fig. 7 described above. Note that Fig. 4, Fig. 6, Fig. 8, Fig. 10, and Fig. 12 and Fig. 13 described later are cross-sectional views of the vicinity of the discharge port 42 on the male rotor 15 side, and the oblique lines shown in the screw rotor in these figures indicate the tooth tips of the screw rotor around the axial discharge port. That is, these figures show how the volume of the tooth groove space decreases toward the discharge port 42.

[0031] As shown in Figures 3, 4, 6, 8 and 10, in some implementations, the screw compressor 2 includes a movable piece 54 provided along the edge of the opening 52 provided in the casing 12. The movable piece 54 is capable of blocking a part of the opening 52.

[0032] The movable piece 54 includes a first end face 54a and a second end face 54b which are both end faces in the axial direction. The first end face 54a is an end face facing the discharge side end face 48 of the screw rotor (the male rotor 15 and the female rotor 17), and the second end face 54b is an end face opposite to the first end face 54a in the axial direction.

[0033] 4 to 11, the movable piece 54 includes a piston 56 that is movable back and forth in the axial direction. The piston 56 is inserted into a hole 68 that is provided in the casing 12 and extends along the axial direction, and is prevented from slipping out of the hole 68 by a plug 66.

[0034] In the exemplary embodiment shown in FIGS. 4 to 7, the first end surface 54a and the second end surface 54b of the movable piece 54 are formed by both end surfaces of the piston 56. As shown in FIG.

[0035] 8 to 11, the movable piece 54 includes, in addition to the piston 56 which is movable axially back and forth, a plate-like member 78 attached to an end portion on the suction side in the axial direction of the piston 56. A first end surface 54a of the movable piece 54 is formed by an end surface on the suction side in the axial direction of the plate-like member 78, and a second end surface 54b of the movable piece 54 is formed by an end surface on the discharge side in the axial direction of the piston 56.

[0036] The movable piece 54 is configured to be movable between a first position in the axial direction (see Figs. 4-5 and 8-9) and a second position in the axial direction that is farther away from the screw rotor than the first position (see Figs. 6-7 and 10-11). That is, the movable piece 54 in the second position is located closer to the discharge side in the axial direction than the movable piece 54 in the first position.

[0037] For example, as shown in Figures 4 to 5 and 8 to 9, a first contour 101, which is the contour of the axial discharge port 44 when the movable piece 54 is in the first position, is formed by the movable piece 54 and the edge of the opening 52 provided in the casing 12 (see Figures 5 and 9). That is, the movable piece 54 in the first position closes a part of the opening 52 provided in the casing 12, and therefore the opening area of ​​the axial discharge port 44 when having the first contour 101 is smaller than the opening area of ​​the opening 52 of the casing 12. Note that, when the movable piece 54 is in the first position, the first end surface 54a of the movable piece 54 is flush with the rotor-facing surface 50 of the casing 12.

[0038] 6 to 7 and 10 to 11, when the movable piece 54 is in the second position, a second contour 102, which is the contour of the axial discharge port 44, is formed by the edge of the opening 52 provided in the casing 12 (see FIGS. 7 and 11). That is, the opening area of ​​the axial discharge port 44 when it has the second contour 102 is larger than the opening area of ​​the axial discharge port 44 when it has the above-mentioned first contour 101. When the movable piece 54 is in the second position, the first end surface 54a of the movable piece 54 is located on the discharge side in the axial direction relative to the rotor-opposing surface 50 of the casing 12.

[0039] In the exemplary embodiment shown in Figures 4 to 7, when the movable piece 54 is in the first position described above, the axial end face of the piston 56 on the intake side (first end face 54a of the movable piece 54) is flush with the rotor-facing surface 50 of the casing 12 (see Figure 4), and the piston 56 forms part of the first contour 101 (see Figure 5).

[0040] In the exemplary embodiment shown in Figures 8 to 11, when the movable piece 54 is in the above-mentioned first position, the suction side end face of the plate-shaped member 78 in the axial direction (first end face 54a of the movable piece 54) is flush with the rotor-facing surface 50 of the casing 12 (see Figure 8), and the plate-shaped member 78 forms part of the first contour 101 (see Figure 9).

[0041] In the above-described embodiment, the movable piece 54 provided along the edge of the opening 52 of the casing 12 forming the axial discharge port 44 is movable between a first position in the axial direction and a second position that is farther away from the screw rotors (the male rotor 15 and the female rotor 17) than the first position. When the movable piece 54 is located at the second position, the opening area of ​​the axial discharge port 44 is larger than when the movable piece 54 is located at the first position. Therefore, under an operating condition in which the internal volume ratio Vi of the screw compressor 2 is relatively high (for example, when the slide valve 30 is located relatively closer to the suction side in the axial direction), the movable piece 54 is located at the second position to relatively increase the opening area of ​​the axial discharge port 44, thereby suppressing an increase in the gas flow velocity at the discharge port 42 and suppressing an increase in discharge loss. Furthermore, under operating conditions where the internal volume ratio Vi of the screw compressor 2 is relatively low (for example, when the slide valve 30 is located relatively closer to the discharge side in the axial direction), the opening area of ​​the axial discharge port 44 is relatively small by positioning the movable piece 54 at the first position, thereby suppressing an increase in discharge loss due to insufficient compression. Therefore, according to the above-described embodiment, by switching the position of the movable piece 54 between the first position and the second position according to the internal volume ratio Vi, it is possible to suppress discharge loss over a wide range of operating regions (internal volume ratios Vi).

[0042] In the above embodiment, the movable piece 54 includes a piston 56 that is movable forward and backward in the axial direction. That is, the movable piece 54 (piston 56) advances and retreats in a direction perpendicular to the discharge end face 48 of the screw rotor, so that interference between the movable piece 54 and the screw rotor is unlikely to occur, and damage due to contact between them can be suppressed.

[0043] Furthermore, in the exemplary embodiment shown in Figures 4 to 7, when the movable piece 54 including the piston 56 is in the first position, the end face of the piston 56 (first end face 54a of the movable piece 54) is flush with the rotor-facing surface 50 of the casing 12, and the piston 56 itself forms the contour (first contour) of the axial discharge port 44, so that the screw compressor 2 including the above-mentioned movable piece 54 can be realized with a simple configuration.

[0044] 8 to 11, when the movable piece 54 including the plate-like member 78 attached to the end of the piston 56 is in the first position, the end face of the plate-like member 78 (the first end face 54a of the movable piece 54) is flush with the rotor-facing surface 50 of the casing 12, and the plate-like member 78 forms the contour (first contour) of the axial discharge port 44. Here, since any shape can be used as the plate-like member 78, by selecting an appropriate shape for the plate-like member 78, it becomes easier to optimize the shape of the first contour of the axial discharge port 44 according to the tooth shape of the screw rotor, etc.

[0045] 4, 6, 8, and 10, the piston 56 has a first portion 58 and a second portion 60 that is adjacent to the first portion 58 in the axial direction, is located on the discharge side of the first portion 58 in the axial direction, and has a larger diameter than the first portion 58. A step portion 61 is formed between the first portion 58 and the second portion 60 in the axial direction, and this step portion 61 restricts movement of the piston 56 in a direction from the second position toward the first position (i.e., a direction from the discharge side toward the suction side in the axial direction).

[0046] In the illustrated embodiment, the casing 12 is provided with a position control surface 76 facing the discharge side in the axial direction, and the surface of the second part 60 of the piston 56 forming the step portion 61 abuts against the position control surface 76, thereby regulating the axial position of the piston 56.

[0047] By providing the above-mentioned step portion 61, the movement of the piston 56 in the direction from the second position toward the first position is restricted, so that it is possible to prevent the end face of the piston 56 (the first end face 54a of the movable piece 54) from protruding toward the screw rotor from the position of the rotor-opposing surface 50 of the casing 12. Therefore, it is possible to suppress contact between the piston 56 and the discharge side end face 48 of the screw rotor.

[0048] 4, 6, 8, and 10, the screw compressor 2 includes a communication passage 74 that communicates a back space 72, to which the second end surface 54b of the movable piece 54 is exposed, with the discharge space 43. In the illustrated embodiment, the back space 72 is formed between the second end surface 54b of the movable piece 54 and the plug 66.

[0049] As shown in Figures 4, 6, 8 and 10, a biasing member 62 (e.g., a spring) may be provided between the movable piece 54 (piston 56) and the plug 66 in the axial direction to apply a preload to the movable piece 54 in the axial direction from the discharge side to the suction side (i.e., the direction from the movable piece 54 to the screw rotor).

[0050] According to the above-described embodiment, the first end face 54a of the movable piece 54 faces the tooth groove space immediately before the axial discharge port 44 (i.e., the tooth groove space immediately before discharge), and the second end face 54b of the movable piece 54 faces the back side space 72 communicating with the discharge space 43, so that the movable piece 54 can be automatically driven by the pressure difference between the tooth groove space immediately before the axial discharge port 44 and the discharge space 43.

[0051] That is, under operating conditions where the internal volume ratio Vi is relatively low, the tooth groove space immediately before the axial discharge port 44 has a pressure equal to or lower than that of the discharge space 43, and at this time, the movable piece 54 is located at the first position due to the difference in pressure acting on both end faces (the first end face 54a and the second end face 54b). On the other hand, under operating conditions where the internal volume ratio Vi is relatively high, the tooth groove space immediately before the axial discharge port 44 has a higher pressure than the discharge space 43, and therefore a force from the first end face 54a toward the second end face 54b acts on the movable piece 54 due to the difference in pressure acting on the first end face 54a and the second end face 54b, so that the movable piece 54 is located at the second position.

[0052] As described above, according to the embodiment described above, the movable piece 54 can be automatically and appropriately driven in accordance with the difference in pressure acting on both end faces (the first end face 54a and the second end face 54b) of the movable piece 54 so that the movable piece 54 is located at the first position when the internal volume ratio Vi is relatively low, and is located at the second position when the internal volume ratio Vi is relatively high. This makes it possible to suppress discharge loss over a wide operating range (internal volume ratio Vi).

[0053] Figures 12 and 13 are schematic cross-sectional views showing the vicinity of the axial discharge port 44 of a screw compressor according to one embodiment, and show modified examples of the embodiment shown in Figures 4 to 11. Note that Figures 12 and 13 are views corresponding to Figure 4 (views including the movable piece 54 located at the first position), and views including the movable piece 54 located at the second position (views corresponding to Figure 6) are omitted. In Figures 12 and 13, descriptions of elements with the same reference numerals as those shown in Figures 4 to 11 will be omitted to avoid repetition.

[0054] 12 and 13, the above-mentioned communication passage 74 is not provided. Instead, the screw compressor 2 according to this embodiment includes a high-pressure line 82 for introducing a high-pressure fluid having a higher pressure than the discharge space 43 into the rear space 72 facing the second end face 54b of the movable piece 54, and a valve 84 provided in the high-pressure line 82. Note that, in the illustrated embodiment, the high-pressure fluid from the high-pressure line 82 is introduced into the rear space 72 via an internal flow path 80 provided in the casing 12.

[0055] In one embodiment, oil pressurized by the pump 8 in the oil supply line 10 (pressure Poil: Pd+α) may be supplied to the rear side space 72 via a high pressure line 82.

[0056] In the above-described embodiment, by appropriately operating the valve 84, it is possible to introduce high-pressure fluid through the high-pressure line 82 into the rear space 72 where the second end face 54b of the movable piece 54 is exposed. This makes it possible to forcibly move the movable piece 54 from the second position to the first position.

[0057] For example, even when the load on the screw compressor 2 is relatively high and the pressure in the tooth groove space immediately before the axial discharge port 44 is relatively high, the valve 84 can be appropriately operated as necessary to introduce high-pressure fluid from the high-pressure line 82 into the back side space 72 and forcibly move the movable piece 54 from the second position to the first position, thereby narrowing the opening area of ​​the axial discharge port 44 and increasing the internal volume ratio Vi.

[0058] The exemplary embodiment shown in FIG. 12 further includes an orifice 88 that connects the above-mentioned rear side space 72 and the discharge space 43 .

[0059] In the above embodiment, the rear space 72 and the discharge space 43 are connected via the orifice 88. Therefore, while the valve 84 is opened and high-pressure fluid is supplied from the high-pressure line 82 to the rear space 72, the pressure in the rear space 72 is maintained at an appropriate pressure higher than the discharge space 43, and the movable piece can be maintained at the first position. The high-pressure oil in the rear space 72 is appropriately discharged to the discharge space 43 via the orifice 88. Also, while the valve 84 is closed and the supply of high-pressure fluid from the high-pressure line 82 to the rear space 72 is stopped, the pressure in the rear space 72 becomes equal to the pressure in the discharge space 43. Therefore, as already described, the movable piece 54 can be automatically driven to move between the first position and the second position by the pressure difference between the tooth groove space immediately before the axial discharge port 44 and the discharge space 43 (i.e., the pressure difference acting on the first end face 54a and the second end face 54b of the movable piece 54).

[0060] 13, the screw compressor 2 includes a low-pressure line 90 connected to a low-pressure source having a lower pressure than the discharge space 43. The valve 84 is configured to be able to switch the connection destination of the rear space 72 between the high-pressure line 82 and the low-pressure line 90.

[0061] The low pressure source may be a gas having a suction pressure Ps, and the low pressure line 90 may be branched off from a suction line (not shown) for introducing suction gas (pressure: Ps) to the screw compressor 2. The valve 84 may include a three-way valve provided between the rear space 72 and the high pressure line 82 and low pressure line 90.

[0062] In the above embodiment, by appropriately operating the valve 84, the connection destination of the back side space 72, to which the second end surface 54b of the movable piece 54 is exposed, can be switched between the high pressure line 82 and the low pressure line 90. By connecting the back side space 72 to the high pressure line 82, a high pressure fluid can be introduced into the back side space 72 to forcibly move the movable piece 54 from the second position to the first position, and by connecting the back side space 72 to the low pressure line 90, a low pressure fluid from a low pressure source can be introduced into the back side space 72 to forcibly move the movable piece 54 from the first position to the second position. That is, by operating the valve 84 to switch the connection destination of the back side space 72 between the high pressure line 82 and the low pressure line 90 according to the operating condition of the screw compressor 2, the position of the movable piece 54 can be appropriately changed between the first position and the second position. Therefore, more flexible operation of the screw compressor 2 is possible, and it is easy to suppress the discharge loss over a wide operating range (internal volume ratio).

[0063] As described above, according to the exemplary embodiment shown in Figs. 12 and 13, the screw compressor 2 can be operated more flexibly, and the discharge loss can be easily suppressed over a wide range of operating regions (internal volume ratios).

[0064] The contents described in each of the above embodiments can be understood, for example, as follows.

[0065] [1] At least one embodiment of the screw compressor (2) of the present invention comprises: A screw rotor (e.g., a male rotor 15 and a female rotor 17) having a discharge end surface (48); a casing (2) having a rotor-opposing surface (50) facing the discharge side end surface, and an opening (52) provided in the rotor-opposing surface and communicating with a discharge space (43) into which gas compressed by the screw rotor is discharged; a slide valve (30) whose position in the axial direction of the screw rotor is variable so as to change the internal volume ratio; a movable piece (54) provided along an edge of the opening of the casing and configured to be able to close a part of the opening; Equipped with the movable piece is configured to be movable between a first position where the movable piece forms a first contour (101) of the axial discharge port (44) together with an edge of the opening, and a second position that is farther away from the screw rotor in the axial direction than the first position, When the movable piece is located at the second position, the opening forms a second contour (102) of the axial discharge port having an opening area larger than that of the first contour.

[0066] In the above configuration [1], the movable piece provided along the edge of the opening of the casing forming the axial discharge port can move between a first position in the axial direction and a second position that is farther from the screw rotor than the first position. When the movable piece is located at the second position, the opening area of ​​the axial discharge port is larger than when the movable piece is located at the first position. Therefore, under operating conditions in which the internal volume ratio of the screw compressor is relatively high, the opening area of ​​the axial discharge port can be relatively large by positioning the movable piece at the second position, and the increase in the gas flow rate at the discharge port can be suppressed to suppress the increase in the discharge loss. Also, under operating conditions in which the internal volume ratio of the screw compressor is relatively low, the opening area of ​​the axial discharge port can be relatively small by positioning the movable piece at the first position, and the increase in the discharge loss due to insufficient compression can be suppressed. Therefore, according to the above configuration [1], the position of the movable piece can be switched between the first position and the second position depending on the internal volume ratio to suppress the discharge loss over a wide range of operating regions (internal volume ratios).

[0067] [2] In some embodiments, in the configuration of [1] above, The movable piece includes a piston (56) that is movable forward and backward in the axial direction.

[0068] According to the configuration [2] above, it is possible to realize a screw compressor including the movable piece described in [1] above with a simple configuration using a piston that can advance and retreat in the axial direction.

[0069] [3] In some embodiments, in the configuration of [2] above, The screw compressor comprises: When the movable piece is in the first position, an end face of the piston in the axial direction (e.g., a first end face 54a of the movable piece 54) is flush with the rotor-facing surface of the casing and the piston is configured to form part of the first contour.

[0070] According to the configuration [3] above, when the movable piece including the piston is in the first position, the end face of the piston is flush with the rotor-facing surface of the casing, and the piston itself forms the contour (first contour) of the axial discharge port. Therefore, with a simple configuration, it is possible to realize a screw compressor including the movable piece described in [1] above.

[0071] [4] In some embodiments, in the configuration of [2] above, The movable piece includes a plate-like member (78) attached to an end of the piston in the axial direction, The screw compressor comprises: When the movable piece is in the first position, an end face of the plate-shaped member in the axial direction (e.g., the first end face 54a of the movable piece 54) is flush with the rotor-facing surface of the casing, and the plate-shaped member is configured to form part of the first contour.

[0072] According to the configuration [4] above, when the movable piece including the plate-shaped member attached to the end of the piston is in the first position, the end face of the plate-shaped member is flush with the rotor-facing surface of the casing, and the plate-shaped member forms the contour (first contour) of the axial discharge port. Here, any shape of plate-shaped member can be used, so that the shape of the first contour of the axial discharge port can be optimized easily according to the tooth shape of the screw rotor, etc.

[0073] [5] In some embodiments, in any of the configurations [2] to [4] above, The piston is A first portion (58); a second portion (60) that is provided on the opposite side of the screw rotor with the first portion in the axial direction and has a larger diameter than the first portion, The screw compressor comprises: A step portion (61) formed by the first portion and the second portion is configured to restrict movement of the piston in a direction from the second position toward the first position.

[0074] According to the configuration [5] above, the step of the piston restricts the movement of the piston from the second position toward the first position, so that the end face of the piston can be prevented from protruding toward the screw rotor from the position of the rotor-facing surface of the casing, thereby suppressing contact between the piston and the end face of the screw rotor.

[0075] [6] In some embodiments, in any one of the configurations [1] to [5] above, The movable piece has a first end surface (54a) facing the screw rotor and a second end surface (54b) opposite to the first end surface in the axial direction, The screw compressor comprises: The nozzle includes a communication passage (74) that connects the discharge space to a rear space (72) to which the second end face is exposed.

[0076] According to the configuration [6], the first end face of the movable piece faces the tooth groove space immediately before the axial discharge port (i.e., the tooth groove space immediately before discharge), and the second end face of the movable piece faces the back side space communicating with the discharge space, so that the movable piece can be automatically driven by the pressure difference between the tooth groove space and the discharge space. That is, the movable piece can be automatically and appropriately driven in accordance with the pressure difference so that the movable piece is located at the first position when the internal volume ratio is relatively low, and is located at the second position when the internal volume ratio is relatively high.

[0077] [7] In some embodiments, in any one of the configurations [1] to [5] above, The movable piece has a first end surface (54a) facing the screw rotor and a second end surface (54b) opposite to the first end surface in the axial direction, The screw compressor comprises: a high-pressure line (82) for introducing a high-pressure fluid having a higher pressure than the discharge space into a rear space (72) to which the second end surface is exposed; a valve (84) provided between the rear space and the high pressure line; Equipped with.

[0078] According to the above configuration [7], by appropriately operating the valve, a high-pressure fluid can be introduced through the high-pressure line into the back space where the second end face of the movable piece is exposed, and the movable piece can be forcibly moved from the second position to the first position. Therefore, even when the load of the screw compressor is relatively high and the pressure in the tooth groove space immediately before the axial discharge port is relatively high, the opening area of ​​the discharge port can be narrowed and the internal volume ratio can be increased by introducing the high-pressure fluid into the back space by operating the valve as necessary to forcibly move the movable piece from the second position to the first position. Therefore, more flexible operation of the screw compressor is possible, and discharge loss can be easily suppressed over a wide range of operating ranges (internal volume ratios).

[0079] [8] In some embodiments, in the configuration of [7] above, The nozzle includes an orifice (88) that connects the rear space, to which the second end face is exposed, and the discharge space.

[0080] According to the configuration [8] above, since the rear space and the discharge space are connected via an orifice, while the valve is open and high-pressure fluid is being supplied from the high-pressure line to the rear space, the pressure in the rear space is maintained at an appropriate pressure higher than that of the discharge space, and the movable piece can be maintained in the first position. Also, while the valve is closed and the supply of high-pressure fluid from the high-pressure line to the rear space is stopped, the pressure in the rear space becomes equal to that of the discharge space, so that the movable piece can be automatically driven by the pressure difference between the tooth groove space immediately before the axial discharge port and the discharge space, as explained in [6] above.

[0081] [9] In some embodiments, in the configuration of [7] above, a low pressure line (90) connected to a low pressure source having a lower pressure than the discharge space; The valve is configured to be able to switch the connection destination of the rear side space between the high pressure line and the low pressure line.

[0082] According to the above-mentioned configuration [9], the connection destination of the back side space where the second end face of the movable piece is exposed can be switched between the high pressure line and the low pressure line by appropriately operating the valve. Here, by connecting the back side space to the high pressure line, a high pressure fluid can be introduced into the back side space to forcibly move the movable piece from the second position to the first position, and by connecting the back side space to the low pressure line, a low pressure fluid from a low pressure source can be introduced into the back side space to forcibly move the movable piece from the first position to the second position. That is, by operating the valve to switch the connection destination of the back side space between the high pressure line and the low pressure line according to the operating condition of the screw compressor, the position of the movable piece can be appropriately changed between the first position and the second position. Therefore, more flexible operation of the screw compressor is possible, and it becomes easier to suppress the discharge loss over a wide operating range (internal volume ratio).

[0083]

[10] At least one embodiment of the gas compression equipment (1) of the present invention comprises: A screw compressor (2) according to any one of the above [1] to [9] configured to compress a gas; an oil separator (4) for separating the oil from a mixture of compressed gas and oil discharged from the screw compressor; Equipped with.

[0084] In the configuration of

[10] above, the movable piece provided along the edge of the opening of the casing forming the discharge port can move between a first position in the axial direction and a second position farther from the screw rotor than the first position. When the movable piece is located at the second position, the opening area of ​​the axial discharge port is larger than when the movable piece is located at the first position. Therefore, under operating conditions in which the internal volume ratio of the screw compressor is relatively high, the opening area of ​​the axial discharge port is relatively large by positioning the movable piece at the second position, thereby suppressing an increase in the gas flow rate at the discharge port and suppressing an increase in the discharge loss. Also, under operating conditions in which the internal volume ratio of the screw compressor is relatively low, the opening area of ​​the axial discharge port is relatively small by positioning the movable piece at the first position, thereby suppressing an increase in the discharge loss due to insufficient compression. Therefore, according to the configuration of

[10] above, the position of the movable piece can be switched between the first position and the second position depending on the internal volume ratio, thereby suppressing the discharge loss over a wide range of operating regions (internal volume ratios).

[0085] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and also includes modifications to the above-described embodiments and appropriate combinations of these modifications.

[0086] In this specification, expressions expressing relative or absolute configuration, such as "in a certain direction," "along a certain direction," "parallel," "orthogonal," "center," "concentric," or "coaxial," do not only strictly represent such a configuration, but also represent a state in which there is a relative displacement with a tolerance or an angle or distance to the extent that the same function is obtained. For example, expressions indicating that things are in an equal state, such as "identical," "equal," and "homogeneous," not only indicate a state of strict equality, but also indicate a state in which there is a tolerance or a difference to the extent that the same function is obtained. Furthermore, in this specification, expressions describing shapes such as a rectangular shape or a cylindrical shape do not only refer to shapes such as a rectangular shape or a cylindrical shape in the strict geometric sense, but also refer to shapes that include uneven portions, chamfered portions, etc., to the extent that the same effect can be obtained. In addition, in this specification, the expressions "comprise," "include," or "have" a certain element are not exclusive expressions that exclude the presence of other elements. [Explanation of symbols]

[0087] 1 Gas compression equipment 2 Screw compressor 4 Oil separator 6 Cooler 8. Pump 10 Oil supply line 12 Casing 14 Rotor shaft 15 Male Rotor 16 Rotor shaft 17 Female Rotor 18 Radial bearings 20 Thrust bearing 24 Shaft seal 28 Balance piston 29 Balance piston chamber 30 Slide valve 31 Notch 32 Hydraulic piston 40 Intake port 41 Inhalation space 42 Discharge port 43 Discharge space 44 Axial discharge port 46 Radial discharge port 48 Discharge side end face 50 Rotor facing surface 52 Aperture 54 Movable piece 54a 1st end face 54b 2nd end face 56 Piston 58 Part 1 60 Part 2 61 Step 62 Pressing member 66 Plug 68 holes 72 Rear space 74 Communication path 76 Position Control Surface 78 Plate-shaped members 80 Internal flow path 82 High Pressure Line 84 Valve 88 Orifice 90 Low Pressure Line 101 First Contour 102 Second Contour Pd Discharge pressure Ps Intake pressure

Claims

1. a screw rotor having a discharge side end surface; a casing having a rotor-opposing surface facing the discharge end surface, and an opening provided on the rotor-opposing surface and communicating with a discharge space into which gas compressed by the screw rotor is discharged; ds compresses the screw rotor so as to change the internal volume ratio; a slide valve whose axial position of the screw rotor is variable; a movable piece provided along an edge of the opening of the casing and configured to be capable of closing a part of the opening; Equipped with the movable piece is configured to be movable between a first position where the movable piece forms a first contour of the axial discharge port together with an edge of the opening, and a second position that is farther away from the screw rotor in the axial direction than the first position, When the movable piece is located at the second position, the opening forms a second contour of the axial discharge port having an opening area larger than the first contour. Screw compressor.

2. The movable piece includes a piston that is movable forward and backward in the axial direction. The screw compressor according to claim 1.

3. When the movable piece is in the first position, an end face of the piston in the axial direction is flush with the rotor-facing surface of the casing, and the piston forms a part of the first contour. The screw compressor according to claim 2.

4. the movable piece includes a plate-like member attached to an end portion of the piston in the axial direction, When the movable piece is in the first position, an end surface of the plate-like member in the axial direction is flush with the rotor-opposing surface of the casing, and the plate-like member forms a part of the first contour. The screw compressor according to claim 2.

5. The piston is A first portion; and a second portion having a larger diameter than the first portion, the second portion being provided on the opposite side of the screw rotor with the first portion interposed therebetween in the axial direction; A step portion formed by the first portion and the second portion is configured to restrict movement of the piston in a direction from the second position toward the first position. A screw compressor according to any one of claims 2 to 4.

6. The movable piece has a first end surface facing the screw rotor and a second end surface opposite to the first end surface in the axial direction, a communication passage that communicates between a rear side space to which the second end surface is exposed and the ejection space; A screw compressor according to any one of claims 1 to 4.

7. The movable piece has a first end surface facing the screw rotor and a second end surface opposite to the first end surface in the axial direction, a high pressure line for introducing a high pressure fluid having a higher pressure than the discharge space into a rear side space to which the second end surface is exposed; a valve provided between the rear space and the high pressure line; Equipped A screw compressor according to any one of claims 1 to 4.

8. an orifice that connects the rear side space to which the second end surface is exposed and the ejection space; The screw compressor according to claim 7.

9. a low pressure line connected to a low pressure source having a lower pressure than the discharge space; The valve is configured to be able to switch the connection destination of the rear side space between the high pressure line and the low pressure line. The screw compressor according to claim 7.

10. A screw compressor according to any one of claims 1 to 4 configured to compress a gas; an oil separator for separating the oil from a mixture of compressed gas and oil discharged from the screw compressor; Gas compression equipment.

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