WO2022209606A1

WO2022209606A1 - Screw compressor

Info

Publication number: WO2022209606A1
Application number: PCT/JP2022/009701
Authority: WO
Inventors: 聖太谷本; 利明矢部; 航平酒井
Original assignee: 株式会社日立産機システム
Priority date: 2021-03-31
Filing date: 2022-03-07
Publication date: 2022-10-06
Also published as: JP2022157302A

Abstract

This screw compressor is provided with: a plurality of screw rotors; a discharge side bearing that rotatably supports the axial discharge side of the plurality of screw rotors; and a casing which has a storage chamber for storing the plurality of screw rotors, in which the discharge side bearing is disposed at a position on the axial discharge side relative to the storage chamber, and which forms an operation chamber together with the plurality of screw rotors. The casing has: a discharge flow channel that is connected to the axial discharge side of the storage chamber and that guides compressed gas in the operation chamber to the outside; and a cooling flow channel in which a cooling material supplied from the outside of the casing circulates. The cooling flow channel branches off, at a branch part, from the upstream to the downstream. The branch part is present at a position between the discharge side bearing and the discharge flow channel in the axial direction and at a position that overlaps with a region to which the discharge flow channel is axially projected.

Description

screw compressor

The present invention relates to a screw compressor, and more particularly to a screw compressor whose casing is cooled by a coolant.

Some screw compressors have a pair of screw rotors that rotate while meshing with each other, and a casing that houses both screw rotors. This screw compressor sucks and compresses gas by increasing and decreasing the volume of a plurality of working chambers formed by both screw rotors and the inner wall surface of a casing surrounding them as both screw rotors rotate.

Internal leakage of compressed gas is a typical factor that reduces the performance of screw compressors. Internal leakage of compressed gas is the reverse flow of compressed gas from a high-pressure space (working chamber) where compression has progressed and the pressure has risen to a relatively low-pressure space before the start of compression or where compression has not progressed. It refers to the phenomenon of This internal leakage results in a loss of energy as the compressed gas returns to a low pressure state at an energy cost. The internal gaps, which are paths for internal leakage of compressed gas, include the gap between the meshing portions of the two screw rotors, the gap between the tip of the screw rotor and the inner wall surface (inner peripheral surface) of the casing, and the discharge side end face of the screw rotor. and the discharge-side inner wall surface of the casing facing it.

In a screw compressor, the compressed gas becomes hot, so the temperature of the casing and screw rotor rises due to the high temperature of the compressed gas, causing thermal deformation. Due to thermal deformation of the casing and screw rotor, the internal gap tends to expand. In particular, in non-feed type screw compressors that do not supply liquid to the working chamber, the compressed gas is not cooled by the liquid, so the compressed gas becomes hotter than in the case of feed type screw compressors. In addition, the internal clearance increases due to thermal deformation of the casing and screw rotor.

As a measure for reducing an increase in the internal leakage of compressed gas due to thermal deformation of the casing, a technique of cooling the casing by circulating a coolant through cooling channels provided in the casing is known (for example, Patent Document 1 (see FIGS. 1 and 4). In the oil-free screw compressor illustrated in Patent Document 1, a cooling passage is provided in a portion of the casing radially outside the rotor chamber, and the axial discharge side of the screw rotor is rotatably supported. A cooling passage is provided in the peripheral portion of the discharge side bearing.

JP 2016-70145 A

Among the leaks of compressed gas through the above-mentioned internal gaps, it was simulated that the leak of compressed gas through the gaps between the meshing portions of the two screw rotors had the greatest impact on the compressor efficiency. It is clear from Discharge-side bearings that rotatably support the respective screw rotors are arranged in the vicinity of the discharge passage of the casing through which the discharged compressed gas flows. Since the casing around the discharge passage undergoes particularly large thermal deformation due to heat transfer from the high-temperature compressed gas, the increase in the relative distance between the two discharge-side bearings causes the gap between the meshing portions of the two screw rotors to widen. easy to grow.

It is necessary to suppress the expansion of the gap between the meshing portions of both screw rotors caused by such thermal deformation of the casing. In the oil-free screw compressor illustrated in Patent Document 1, a cooling channel is provided in the casing portion between the discharge channel (discharge port) and the discharge-side bearing (ball bearing). Heat transfer of the flowing high temperature compressed gas to the peripheral portion of the discharge side bearing is suppressed. However, even such a cooling method cannot completely prevent thermal deformation of the casing. Therefore, in order to improve the efficiency of the compressor, it is required to further improve the cooling capacity for the casing.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and one of the objects thereof is to improve the efficiency of the compressor by increasing the cooling capacity of the periphery of the discharge-side bearing in the casing. A compressor is provided.

A preferred example of the present invention accommodates a plurality of screw rotors that rotate so as to mesh with each other, discharge-side bearings that rotatably support one axial side of each of the plurality of screw rotors, and the plurality of screw rotors. a casing having an accommodation chamber, wherein the discharge side bearing is disposed at a position on the one side in the axial direction relative to the accommodation chamber, and which forms an operating chamber together with the plurality of screw rotors, the casing comprising: A cooling passage communicating with the one side of the housing chamber in the axial direction and having a discharge passage for guiding the compressed gas in the working chamber to the outside of the casing, and through which a coolant supplied from the outside of the casing circulates. wherein the cooling channel branches from upstream to downstream at a branching portion, the branching portion being located between the discharge channel and the discharge-side bearing in the axial direction, and The screw compressor is positioned so as to overlap the projected area of the discharge passage in the axial direction.

According to a preferred embodiment of the present invention, the cooling flow path is branched at a position between the discharge flow path and the discharge-side bearing in the axial direction of the screw rotor and at a position overlapping an area where the discharge flow path is projected in the axial direction. , the heat transfer coefficient is improved in the branched portion of the cooling channel and in the region immediately downstream thereof. In other words, since the cooling capacity of the casing around the discharge side bearing is enhanced, expansion of the relative distance between the discharge side bearings due to thermal deformation of the casing is suppressed, and the efficiency of the compressor can be improved.
Problems, configurations, and effects other than those described above will be clarified by the following description of the embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional view showing a schematic structure of a screw compressor according to a first embodiment of the present invention, and a system diagram showing an external circulation path of coolant for the screw compressor; FIG. 2 is a cross-sectional view of the screw compressor according to the first embodiment of the present invention, viewed from the II-II arrow direction shown in FIG. 1; FIG. 2 is a cross-sectional view of the screw compressor according to the first embodiment of the present invention, viewed from the line III-III shown in FIG. 1; FIG. 4 is a schematic diagram showing the flow (secondary flow) in the cooling channel when the screw compressor according to the first embodiment of the present invention is viewed from the IV-IV arrows shown in FIG. 3; FIG. 4 is a diagram showing analysis results of the distribution of heat transfer coefficient between the casing and the coolant in the cooling flow path in the screw compressor according to the first embodiment of the present invention; It is a sectional view showing a schematic structure of a screw compressor concerning a 2nd embodiment of the present invention. FIG. 5 is a diagram showing analysis results of a flow velocity distribution of coolant in a bent pipe connected to a cooling flow path of a casing in a screw compressor according to a second embodiment of the present invention; Analysis of the relationship between the distance from the bent portion (bent flow path) of the bent pipe connected to the cooling flow path of the casing and the flow velocity of the coolant at that position in the screw compressor according to the second embodiment of the present invention It is a figure which shows a result. It is a sectional view showing a schematic structure of a screw compressor concerning a 3rd embodiment of the present invention. FIG. 10 is a diagram showing analysis results of a flow velocity distribution of a coolant in a contraction tube connected to a cooling flow path of a casing in a screw compressor according to a third embodiment of the present invention;

An embodiment of a screw compressor according to the present invention will be described below with reference to the drawings. The present embodiment is an example in which the present invention is applied to an oilless screw compressor.

[First embodiment]
A configuration of a screw compressor according to a first embodiment will be described with reference to FIGS. 1 and 2. FIG. FIG. 1 is a cross-sectional view showing the schematic structure of a screw compressor according to a first embodiment of the present invention, and a system diagram showing an external circulation route of a coolant for the screw compressor. FIG. 2 is a cross-sectional view of the screw compressor according to the first embodiment of the present invention, viewed from the II-II arrow direction shown in FIG. In FIG. 1, the left side is the axial suction side of the screw compressor, and the right side is the axial discharge side. In addition, thick arrows indicate the direction of flow of lubricating oil as a coolant. In FIG. 2, the thick arrow indicates the direction of rotation of the screw rotor.

1 and 2, a screw compressor 1 has a male rotor 2 (male screw rotor) and a female rotor 3 (female screw rotor) that mesh and rotate, and the male and

female rotors

2 and 3 mesh with each other. and a casing 4 that rotatably accommodates it in a state. The male rotor 2 and the female rotor 3 are arranged such that their center axes A1 and A2 are parallel to each other. One side (left side in FIG. 1) and the other side (right side in FIG. 1) of the male rotor 2 in its axial direction (horizontal direction in FIG. 1) are supported by a suction side bearing 6 and

discharge side bearings

7 and 8, respectively. It is rotatably supported and connected to a motor 90 as a rotational drive source. The female rotor 3 is rotatably supported by a suction-side bearing and a discharge-side bearing (both not shown) on one side and the other side in the axial direction. In the oilless screw compressor 1, the male rotor 2 and the female rotor 3 are arranged to rotate in a non-contact state. That is, a gap is formed in the meshing portion between the male rotor 2 and the female rotor 3 .

The male rotor 2 includes a rotor tooth portion 21 having a plurality (four in FIG. 2) of twisted male teeth (lobes) 21a, and a suction side (see FIG. 1 It is composed of a shaft portion 22 on the middle, left side) and a shaft portion 23 on the discharge side (right side in FIG. 1). The suction-side shaft portion 22 , for example, extends outside the casing 4 and is integrated with the shaft portion of the motor 90 . The suction side shaft portion 22 may be configured to be connected to the motor 90 via a gear (not shown). A timing gear 10 is attached to the tip of the shaft portion 23 on the discharge side.

The female rotor 3 has a rotor tooth portion 31 having a plurality (six in FIG. 2) of twisted female teeth (lobes) 31a, and a rotor tooth portion 31 at both ends in the axial direction (perpendicular to the plane of FIG. 2) of the rotor tooth portion 31. It is composed of a suction-side shaft portion (not shown) and a discharge-side shaft portion 33 (see FIG. 3) provided respectively. A female timing gear (not shown) that meshes with the male timing gear 10 is attached to the distal end of the discharge-side shaft portion 33 . The rotational force of the male rotor 2 is transmitted to the female rotor 3 by the male timing gear 10 and the female timing gear, and the male rotor 2 and the female rotor 3 rotate synchronously without contact.

The casing 4 includes a main casing 41, a suction side cover 42 attached to the suction side (left side in FIG. 1) of the main casing 41, and a discharge side cover attached to the discharge side (right side in FIG. 1) of the main casing 41. 43.

Inside the casing 4, an accommodation chamber (bore) 46 is formed to accommodate the rotor teeth 21 of the male rotor 2 and the rotor teeth 31 of the female rotor 3 in a state of being meshed with each other. The storage chambers 46 are two partially overlapping cylindrical spaces formed inside the casing 4 . The

rotor tooth portions

21 and 31 of the male and

female rotors

2 and 3 are arranged with a gap of several tens to several hundreds of μm from the inner wall surface forming the housing chamber 46 of the casing 4 . A plurality of working chambers C are formed by the

rotor tooth portions

21 and 31 of the male and

female rotors

2 and 3 and the inner wall surface of the casing 4 surrounding them (the wall surface of the housing chamber 46). The working gas in the working chamber C is compressed as the working chamber C contracts while moving in the axial direction as the male and

female rotors

2 and 3 rotate.

As shown in FIG. 1, the casing 4 is provided with a suction passage 47 for sucking gas into the working chamber C so as to communicate with the housing chamber 46 . Further, the casing 4 is provided with a discharge passage 48 for guiding and discharging the compressed air in the working chamber C to the outside of the casing 4 so as to communicate with the axial discharge side of the housing chamber 46 .

A suction side bearing 6 on the male rotor 2 side and a suction side bearing on the female rotor 3 side are arranged at the end of the main casing 41 on the motor 90 side. A shaft seal member 12 is arranged on the suction side shaft portion 22 of the male rotor 2 on the motor 90 side of the suction side bearing 6 . A suction side cover 42 is attached to the main casing 41 so as to cover the suction side bearing 6 on the male rotor 2 side, the suction side bearing on the female rotor 3 side, and the shaft seal member 12 .

At the end of the main casing 41 opposite to the motor 90, the

discharge side bearings

7, 8 and timing gear 10 on the male rotor 2 side and the discharge side bearing and timing gear on the female rotor 3 side are arranged. The discharge-

side bearings

7, 8 and timing gear 10 on the male rotor 2 side and the discharge-side bearing and timing gear on the female rotor 3 side are arranged at positions on the axial discharge side (right side in FIG. 1) of the housing chamber 46. ing. An air seal 13 and an oil seal 14 are arranged in order from the rotor tooth portion 21 in the portion from the rotor tooth portion 21 side to the

discharge side bearings

7 and 8 in the shaft portion 23 on the discharge side of the male rotor 2 . . Similarly to the discharge-side shaft portion 23 of the male rotor 2, the shaft portion 33 on the discharge side of the female rotor 3 is also provided with an air seal and an oil seal (both not shown) in order from the rotor tooth portion 31. ing. The air seal 13 prevents the compressed gas in the working chamber C from leaking toward the

discharge side bearings

7 and 8 . The oil seal 14 prevents the lubricating oil supplied to the discharge-

side bearings

7 and 8 from entering the housing chamber 46 (working chamber C). An oil supply passage 49 for supplying lubricating oil to the suction side bearing 6 and the

discharge side bearings

7 and 8 is provided in the casing 4 . A discharge side cover 43 is attached to the main casing 41 so as to cover the

discharge side bearings

7 and 8 and the timing gear 10 .

In addition, as shown in FIGS. 1 and 2, the casing 4 is provided with a cooling channel 60 for circulating the coolant. The cooling channel 60 is for cooling the casing 4 to which the heat generated by the gas compression is transferred. This embodiment is characterized by the structure of the cooling channel 60, and the details of the configuration and structure of the cooling channel 60 will be described later. As the coolant, gas can be used in addition to liquid such as cooling water and lubricating oil.

An external cooling system 100 for circulating a coolant is connected to the cooling channel 60 of the casing 4 . The external cooling system 100 is configured, for example, to use lubricating oil for lubricating the suction side bearings 6 and the

discharge side bearings

7 and 8 of the male and

female rotors

2 and 3 as a coolant for the casing 4 as well. be. Specifically, the external cooling system 100 includes a pump 101 that sends lubricating oil (coolant) to the suction side bearing 6, the

discharge side bearings

7 and 8, and the casing 4, and a cooler that cools the lubricating oil (coolant). 102, auxiliary equipment 103 such as a filter and a check valve, and piping 104 connecting them. The cooler 102 is, for example, an air-cooled type that uses outside air around the cooler 102 for cooling. The pipe 104 branches into a coolant supply pipe 104a that supplies lubricating oil as a coolant to the cooling flow path 60, and a lubricating oil supply pipe 104b that supplies lubricating oil to the suction side bearing 6 and the

discharge side bearings

7 and 8. is doing.

In the present embodiment, lubricating oil is used as a cooling material for the casing 4, so that a system for supplying lubricating oil to the suction side bearing 6 and the

discharge side bearings

7 and 8 and the external cooling system 100 are shared. example. However, a configuration is also possible in which an external cooling system is provided separately from the system for supplying lubricating oil to the suction side bearing 6 and the

discharge side bearings

7 and 8 . For example, a configuration is possible in which cooling water as a coolant is introduced into the casing 4 and the motor 90 via an external cooling system.

Next, the configuration and structure of the casing cooling flow path in the screw compressor according to the first embodiment will be described with reference to FIGS. 1 to 3. FIG. FIG. 3 is a cross-sectional view of the screw compressor according to the first embodiment of the present invention, viewed from the line III--III shown in FIG.

The temperature around the discharge passage 48 and around the working chamber C (accommodating chamber 46) in the casing 4 shown in FIG. This heat transfer causes the casing 4 to be thermally deformed. In particular, the thermal deformation of the peripheral portion of the discharge passage 48 through which the high-temperature compressed gas flows becomes large. The relative distance to the discharge-side bearing may increase. If the gap between the meshing portions of the male and

female rotors

2 and 3 shown in FIG. 2 becomes large due to the increase in the relative distance, internal leakage of the compressed gas increases through the gap.

Therefore, in this embodiment, as shown in FIGS. Cooling passages 60 are provided at radially outer positions of the

shaft portions

23 and 33 on the discharge side of the

female rotors

2 and 3 . Specifically, the cooling flow path 60 is an introduction flow path for introducing a coolant (lubricating oil) supplied from an external cooling system 100 outside the casing 4 into the casing 4, as shown in FIGS. 1 to 3, for example. 61, a discharge channel 62 that discharges the coolant that has cooled the casing 4 to the external cooling system 100 outside the casing 4, a first branch channel 63 that branches from the introduction channel 61, and a second branch flow It is composed of a channel 64 and a third branch channel 65 arranged radially outside the accommodation chamber 46 .

The introduction channel 61 has an introduction port 61a at its upstream end that is connected directly or via a connecting pipe to the external cooling system 100, and is bifurcated into a first branch channel 63 and a second branch channel 64. has a branching portion 61b at the downstream end. An introduction passage 61 including an introduction port 61a and a branch portion 61b is arranged at a position between the discharge passage 48 and the discharge-

side bearings

7, 8 in the axial direction of the male and

female rotors

2, 3. It is arranged at a position overlapping with a region 48p obtained by projecting the flow path 48 in the axial direction of both the male and

female rotors

2 and 3 .

The discharge channel 62 has a discharge port 62a at its downstream end that is directly or indirectly connected to the external cooling system 100 via a connecting pipe, and has a first branch channel 63 and a second branch channel 64. has a confluence portion 62b at the upstream end where the two flow paths merge. A discharge passage 62 including a discharge port 62a and a merging portion 62b is arranged at a position between the housing chamber 46 and the

discharge side bearings

7, 8 in the axial direction of the male and

female rotors

2, 3. 2 and the center axis A2 of the female rotor 3 on the opposite side of the introduction passage 61 .

The first branch channel 63 and the second branch channel 64 branch into two from the branch portion 61b in the upstream introduction channel 61 and extend in opposite directions along the circumferential direction of the casing 4, It is configured to merge at a confluence portion 62 b in the discharge flow path 62 . The first branch flow path 63 extends along the circumferential direction at a portion radially outside the shaft portion 23 on the discharge side of the male rotor 2 . The second branch flow path 64 extends along the circumferential direction at a portion radially outside the shaft portion 33 on the discharge side of the female rotor 3 . That is, the first branch flow path 63 and the second branch flow path 64 are arranged at positions between the axial discharge flow paths 48 of the male and

female rotors

2 and 3 and the

discharge side bearings

7 and 8. 2 and 3 are provided so as to surround the

shaft portions

23 and 33 on the discharge side from the outside in the radial direction. The first branched flow path 63 and the second branched flow path 64 and their branching portion 61b and merging portion 62b cool the casing portion between the discharge flow path 48 through which the high-temperature compressed gas flows and the

discharge side bearings

7 and 8. It is.

The third branch flow path 65 communicates with at least one of the first branch flow path 63 and the second branch flow path 64, and as shown in FIG. It extends in the circumferential direction. The third branch flow path 65 cools the peripheral portion of the inner peripheral surface of the casing 4 (the wall surface of the accommodation chamber 46 ) facing the tips of the male and

female rotors

2 and 3 .

Thus, in the present embodiment, the cooling flow path 60 of the casing 4 is configured to bifurcate from upstream to downstream and then merge again. The branch portion 61b of the cooling channel 60 is positioned between the discharge channel 48 and the

discharge side bearings

7 and 8 in the axial direction of the male and

female rotors

2 and 3, It is located at a position overlapping the axially projected area 48p of the

rotors

2,3. By arranging the branch portion 61b of the cooling channel 60 at the position described above, the inventors found that the heat transfer coefficient of the branch portion 61b located near the discharge channel 48 and the discharge-

side bearings

7 and 8 and the peripheral portion thereof is found to improve.

Next, the action and effect of the cooling passage in the screw compressor according to the first embodiment will be explained using FIGS. 1 to 5. FIG. FIG. 4 is a schematic diagram showing the flow (secondary flow) in the cooling channel when the screw compressor according to the first embodiment of the present invention is viewed from the IV-IV arrows shown in FIG. FIG. 5 is a diagram showing analysis results of distribution of heat transfer coefficient between the casing and the coolant in the cooling flow path in the screw compressor according to the first embodiment of the present invention. In FIGS. 3 and 5, white arrows indicate the direction of flow of the coolant (lubricating oil). In FIG. 4, arrows indicate the direction of the secondary flow of the coolant (lubricating oil).

In the screw compressor 1 having the above configuration, when the male rotor 2 is driven by the motor 90 shown in FIG. 1, the male rotor 2 rotates the female rotor 3 shown in FIG. As a result, the working chamber C shown in FIGS. 1 and 2 moves axially as the male and

female rotors

2 and 3 rotate. At this time, the working chamber C sucks gas (for example, air) from the outside of the casing 4 through the suction passage 47 shown in FIG. Compress to a pressure of When the working chamber C communicates with the discharge passage 48 , the compressed gas in the working chamber C passes through the discharge passage 48 and is discharged to the outside of the casing 4 . As the gas heats up when compressed, the heat of the gas is transferred to the casing 4 .

Therefore, in the screw compressor 1 according to the present embodiment, lubricating oil is supplied from the external cooling system 100 shown in FIG. The coolant that cools the casing 4 and rises in temperature is discharged from the cooling flow path 60 to the external cooling system 100 . The coolant discharged to the external cooling system 100 is sent to the cooler 102 by the pump 101 of the external cooling system 100 and cooled by the cooler 102 . The coolant whose temperature has been lowered by the cooler 102 is again introduced into the cooling flow path 60 via the auxiliary machine 103 and the coolant supply pipe line 104a.

By the way, as one of measures to improve the cooling capacity for the casing 4, it is conceivable to lower the temperature of the coolant in the casing 4. However, in this case, the size of the cooler 102 of the external cooling system 100 needs to be increased, which increases the cost. In addition, if the cooler 102 is an air-cooled type, the temperature of the coolant is restricted to be higher than the outside air temperature, so it is difficult to improve the cooling capacity by lowering the temperature of the coolant.

Another measure to improve the cooling capacity is to increase the flow rate of the coolant in the casing 4. As a result, the flow velocity of the coolant increases, and the heat transfer coefficient in the vicinity of the wall surface of the cooling channel 60 improves. However, in this case, it is necessary to increase the size of the pump 101 of the external cooling system 100, and the power of the pump 101 increases accordingly. As a result, the overall power of the compressor system may increase.

On the other hand, in the present embodiment, as shown in FIG. 3, the cooling flow path 60 of the casing 4 is divided from the upstream introduction flow path 61 via the branch portion 61b to the downstream first branch flow path 63 and the second flow path. It is configured to be bifurcated with the branch flow path 64 . In other words, even when the temperature and flow rate of the coolant in the casing 4 are set to the same values as in the conventional case, the characteristic part of the structure of the cooling flow path 60 is intended to improve the cooling performance for the casing 4 .

The main direction of the coolant flowing through the introduction channel 61 is changed by the branching of the first branch channel 63 and the second branch channel 64 . For this reason, centrifugal force acts on the main stream of the coolant to generate a pressure gradient in the region of the branching portion 61b and the first branching flow channel 63 and the second branching flow channel 64 immediately downstream thereof. As a result, in the region of the branched portion 61b and the first branched flow passage 63 and the second branched flow passage 64 immediately downstream thereof, a secondary flow as shown in FIG. . The generation of the secondary flow thins the thermal boundary layer of the coolant near the wall surface of the region, thereby increasing the heat transfer coefficient between the wall surface of the region and the coolant. From the analysis results shown in FIG. 5 as well, it can be seen that the heat transfer coefficient is improved in the region of the branch portion 61b and the first branch channel 63 and the second branch channel 64 immediately downstream thereof. In FIG. 5, black and white shading indicates the level of the heat transfer coefficient, and indicates that the heat transfer coefficient increases as the color approaches black from white. When the heat transfer coefficient is improved, the amount of heat exchanged between the wall surfaces of the cooling passages 60 in the casing 4 and the coolant flowing through the cooling passages 60 increases, so it is possible to suppress the temperature rise of the casing 4 during operation.

In the present embodiment, the branch portion 61b of the cooling passage 60 of the casing 4, which has an improved heat transfer coefficient, is arranged between the discharge passage 48 and the

discharge side bearings

7, 8 in the axial direction of the male and

female rotors

2, 3. and a position overlapping a region 48p where the discharge flow path 48 is projected in the axial direction. As a result, even if the temperature and flow rate of the coolant supplied to the casing 4 are set to be the same as before, the portion between the discharge passage 48 and the

discharge side bearings

7 and 8, which is at the highest temperature in the casing 4, can be cooled. Since the capacity is improved, thermal deformation of the relevant portion of the casing 4 can be suppressed. Therefore, expansion of the relative distance between the

discharge side bearings

7, 8 on the male rotor 2 side and the discharge side bearings on the female rotor 3 side due to thermal deformation of the casing 4 is suppressed. Internal leakage of the screw compressor 1 is reduced by suppressing expansion of the gap between the meshing portions. As a result, compressor efficiency is improved.

The screw compressor 1 of the present embodiment described above includes the male rotor 2 and the female rotor 3 (plurality of screw rotors) that rotate so as to mesh with each other, and the shafts of the male rotor 2 and the female rotor 3 (plurality of screw rotors). It has

discharge side bearings

7 and 8 that rotatably support the discharge side (one side) of the direction, and an accommodation chamber 46 that accommodates the male rotor 2 and the female rotor 3 (a plurality of screw rotors). Discharge-

side bearings

7 and 8 are arranged at positions on the discharge side (one side) in the axial direction. The casing 4 has a discharge passage 48 that communicates with the discharge side (one side) of the housing chamber 46 in the axial direction and guides the compressed gas in the working chamber C to the outside of the casing 4 . It has a cooling channel 60 through which a coolant circulates. The cooling channel 60 branches from upstream to downstream at a branch portion 61b. The branching portion 61b is located between the discharge flow path 48 and the

discharge side bearings

7 and 8 in the axial direction, and overlaps a region 48p where the discharge flow path 48 is projected in the axial direction.

According to this configuration, the cooling flow path is formed at the branch portion 61b located between the discharge flow path 48 and the

discharge side bearings

7 and 8 in the axial direction and overlapping the area 48p where the discharge flow path 48 is projected in the axial direction. By branching the cooling channel 60, the heat transfer coefficient is improved in the branched portion 61b of the cooling channel 60 and the region immediately downstream thereof. Thereby, the cooling ability of the coolant to the casing 4 is improved. That is, since the cooling capacity of the casing 4 around the

discharge side bearings

7 and 8 is enhanced, the increase in the relative distance between the

discharge side bearings

7 and 8 due to thermal deformation of the casing 4 is suppressed, and the efficiency of the compressor is improved. can be achieved.

Further, the cooling flow path 60 of the casing 4 according to the present embodiment has an introduction port 61a for introducing a coolant from the outside of the casing 4 at its upstream end and extends from the introduction port 61a to a branch portion 61b (predetermined position). It includes an existing inlet channel 61 . The introduction flow path 61 is arranged at a position between the discharge flow path 48 and the

discharge side bearings

7 and 8 in the axial direction and at a position overlapping a region 48p where the discharge flow path 48 is projected in the axial direction.

According to this configuration, the coolant introduced from the outside of the casing 4 through the introduction port 61a flows through the region between the discharge flow path 48 and the

discharge side bearings

7, 8, which becomes hot. Thermal deformation of the casing around 8 can be suppressed.

Further, the cooling channel 60 according to the present embodiment includes a first branch channel 63 and a second branch channel 64 that are bifurcated at the branch portion 61b. The first branched flow path 63 and the second branched flow path 64 are configured to extend in opposite directions from each other along the circumferential direction of the casing 4 from the branched portion 61b.

According to this configuration, the first branch flow path 63 and the second branch flow path 64 are extended from the branch portion 61b in opposite directions along the circumferential direction of the casing 4, so that the

discharge side bearings

7 and 8 is cooled, it is possible to suppress expansion of the relative distance between the

discharge side bearings

7 and 8 of the male rotor 2 and the discharge side bearing of the female rotor 3 due to thermal deformation of the casing 4 . Therefore, expansion of the gap between the meshing portions of the male rotor 2 and the female rotor 3 (plurality of screw rotors) is suppressed, so that the efficiency of the compressor can be improved.

[Second embodiment]
A screw compressor according to a second embodiment will be described by way of illustration. First, the configuration and structure of a screw compressor according to the second embodiment will be described with reference to FIG. FIG. 6 is a sectional view showing a schematic structure of a screw compressor according to a second embodiment of the invention. In FIG. 6, parts having the same reference numerals as those shown in FIGS. 1 to 5 are the same parts, and detailed description thereof will be omitted.

A screw compressor 1A according to the second embodiment shown in FIG. (See Fig. 1). The bent tube 66 includes a bent channel that turns the flow direction of the main flow of coolant and causes separation of the coolant flow. In this embodiment, the bent flow path is arranged within a certain range upstream of the branch portion 61b (see FIG. 3) of the cooling flow path 60. FIG.

Specifically, the bent pipe 66 includes a first straight pipe portion 66a having a linearly extending flow path and a second straight pipe having a linearly extending flow path located downstream of the first straight pipe portion 66a. and a bent portion 66c connecting the first straight pipe portion 66a and the second straight pipe portion 66b. The first straight pipe portion 66a is a portion connected to the external cooling system 100 side. The second straight pipe portion 66b is a portion connected to the introduction port 61a of the cooling channel 60 of the casing 4. As shown in FIG. The bent portion 66c is a portion that functions as a bent flow path that turns the flow direction of the main flow of the coolant to cause flow separation.

The configuration, structure, position, etc. of the cooling channel 60 of the casing 4 are the same as those of the first embodiment (see FIG. 3). That is, the cooling channel 60 is configured to bifurcate from an upstream introduction channel 61 into a downstream first branch channel 63 and a second branch channel 64 via a branch portion 61b. Further, the branch portion 61b is located between the discharge flow passage 48 and the

discharge side bearings

7 and 8 in the axial direction of the male and

female rotors

2 and 3, 3 overlaps the axially projected area 48p.

Next, the action and effect of this embodiment in which the coolant is introduced into the cooling flow path of the casing through the bent pipe will be described with reference to FIG. FIG. 7 is a diagram showing analysis results of the flow velocity distribution of the coolant in the bent pipe connected to the cooling flow path of the casing in the screw compressor according to the second embodiment of the present invention. In FIG. 7, black and white shading represents the level of the flow velocity of the coolant, and indicates that the flow velocity increases as the color approaches black from white. In addition, the white arrow indicates the direction of the mainstream of the coolant.

As shown in FIG. 7, the flow velocity of the coolant flowing through the bent pipe 66 is such that the flow velocity in the second straight pipe portion 66b on the downstream side of the bent portion 66c (bent flow path) is the same as that in the first straight pipe portion 66a on the upstream side. greater than the flow velocity inside Therefore, when the coolant is introduced into the cooling channel 60 of the casing 4 via the bent pipe 66, the flow velocity of the coolant introduced into the cooling channel 60 increases. Therefore, the flow velocity of the main flow of the coolant also increases in the region of the branch portion 61b of the cooling channel 60 and the first branch channel 63 and the second branch channel 64 immediately downstream thereof (see FIG. 3). This facilitates the generation of a secondary flow in the cross-section perpendicular to the main flow of coolant, further increasing the heat transfer coefficient between the coolant and the wall surface of that region of the casing 4 . Therefore, since the cooling ability of the coolant for the casing 4 is further improved, the thermal deformation of the casing 4 is further suppressed, and the

discharge side bearings

7 and 8 on the male rotor 2 side and the female rotor 3 side due to the thermal deformation of the casing 4 are reduced. expansion of the relative distance from the discharge side bearing can be further suppressed.

Here, the principle of increasing the flow velocity of the coolant inside the bent tube 66 will be explained. On the downstream side of the bent portion 66c (bent flow path) of the bent pipe 66, a stagnation region where the flow velocity is remarkably low is generated due to separation of the flow of the coolant. In the second straight pipe portion 66b on the downstream side of the bent portion 66c, the coolant flow (flow rate) is concentrated in a region other than the stagnation region, so the flow velocity of the coolant increases. In FIG. 7, the white portion corresponds to the stagnation area.

In order to cause flow separation in the bent pipe 66, it is necessary to change the flow direction of the coolant abruptly to some extent. That is, a curved channel that causes flow separation must change its direction abruptly. Here, the direction of the flow path will be explained. The centerline of the channel is defined as a line connecting the center of gravity points in the cross section where the cross-sectional area of the channel is the smallest. When the center line is a curve, the direction in which the center line faces is defined as the direction of the flow channel, with the tangent line at each point on the curve being the center line. As a condition of the curved channel in which the flow speed is increased on the downstream side than on the upstream side due to flow separation, for example, the length of the curved center line of the curved channel is the length of the inlet 61a of the cooling channel 60 of the casing 4. It is desirable that the direction of the flow path changes from upstream to downstream within a range of 45° or more and 90° or less within the range of diameter or hydraulic diameter or less. The bending point is defined as the position of the center line when the direction of the curved flow path (the direction in which the center line faces) changes by 45° viewed from the upstream. As a condition of the curved channel, the direction of the channel (the direction in which the center line faces) is set to 90° or less. This is because the pressure loss of the flow increases.

When the coolant accelerated by the curved channel continues to flow in the downstream straight channel, the stagnation area disappears and the flow velocity returns to the upstream side of the curved channel. That is, if the length of the second straight pipe portion 66b of the bent pipe 66 is too long, the effect of accelerating the coolant by the bent portion 66c disappears. Therefore, the distance from the bent portion 66c (bending point) of the bent pipe 66 to the branch portion 61b of the cooling flow path 60 of the casing 4 or the length of the second straight pipe portion 66b of the bent pipe 66 is set within a certain range. need to be limited.

Here, the setting range of the distance from the bent portion 66c of the bent pipe 66 as the bent channel to the branch portion 61b of the cooling channel 60 of the casing 4 will be described with reference to FIG. FIG. 8 shows the relationship between the distance from the bent portion (bent flow path) of the bent tube connected to the cooling flow path of the casing and the flow velocity of the coolant at that position in the screw compressor according to the second embodiment of the present invention. It is a figure which shows the analysis result of relationship. In FIG. 8, the horizontal axis L/d represents the ratio of the distance downstream from the bent portion 66c (bending point) of the bent pipe 66 to the diameter of the inlet 61a of the cooling channel 60, and the vertical axis V/V0 represents the ratio of the bent pipe. 66 represents the ratio of the main flow rate of the coolant in the second straight pipe portion 66b on the downstream side to the main flow velocity of the coolant in the first straight pipe portion 66a on the upstream side of the bent portion 66c.

As shown in FIG. 8, the main stream velocity of the coolant in the second straight pipe portion 66b gradually increases from the bent portion 66c (bent flow path) toward the downstream side, and reaches a certain position (approximately 1). After that, the flow velocity of the coolant in the second straight pipe portion 66b decreases as it goes downstream. At a position where the distance from the bent portion 66c (bent flow path) is about 10 times the diameter of the introduction port 61a of the cooling flow path 60, the main stream of coolant in the first straight pipe portion 66a on the upstream side of the bent portion 66c Same speed as speed.

From this, the maximum length of the flow path from the bending point of the bent portion 66c (bent flow path) of the bent tube 66 to the branching portion 61b of the cooling flow path 60 is determined by the diameter of the inlet 61a of the cooling flow path 60 or hydraulic power. By setting the diameter to less than 10 times the diameter, it is possible to obtain the effect of accelerating the coolant by the bent portion 66c (bent flow path) of the bent pipe 66 . Note that, as in the present embodiment, the flow path from the bending point of the bent portion 66c (bent flow path) of the bent tube 66 to the branching portion 61b of the cooling flow path 60 is in the axial direction of the male rotor 2 and the female rotor 3. In the case of the radial direction, the shortest distance between the plane P including the central axis A1 of the male rotor 2 and the central axis A2 of the female rotor 3 and the bending point of the bent portion 66c of the bent pipe 66 is defined as It is also possible to set the diameter to 10 times or less the diameter of the inlet 61a or the hydraulic diameter. Since the shortest distance is definitely longer than the length of the flow path from the bending point of the bent portion 66c (bent flow path) of the bent pipe 66 to the branched portion 61b of the cooling flow path 60, the branched portion 61b of the cooling flow path 60 , the effect of accelerating the coolant by the bent portion 66c (bent flow path) of the bent tube 66 can be reliably obtained.

In addition, in the present embodiment, an example of a configuration in which the bent pipe 66 is connected to the casing 4 to arrange the bent flow path upstream of the branch portion 61b of the cooling flow path 60 is shown. However, instead of connecting the bent tube 66 to the casing 4 , it is also possible to provide a bent channel inside the casing 4 . That is, the bent flow path is arranged at a position within a predetermined range on the upstream side of the branch portion 61b of the cooling flow path 60 inside the casing 4 . As a result, the curved flow path in the cooling flow path 60 can increase the speed of the coolant, and the heat transfer coefficient at the branch portion 61b of the cooling flow path 60 is improved.

In the second embodiment described above, similarly to the first embodiment, the position between the discharge flow path 48 and the

discharge side bearings

7 and 8 in the axial direction and the projection of the discharge flow path 48 in the axial direction By branching the cooling channel 60 at the branching portion 61b that overlaps the region 48p, the heat transfer coefficient is improved in the branching portion 61b of the cooling channel 60 and the region immediately downstream thereof. Thereby, the cooling ability of the coolant to the casing 4 is improved. That is, since the cooling capacity of the casing 4 around the

discharge side bearings

7 and 8 is enhanced, the increase in the relative distance between the

discharge side bearings

Further, in the screw compressor 1A according to the present embodiment, the bent portion 66c of the bent pipe 66 as a bent passage for turning the flow direction of the coolant is arranged upstream of the branch portion 61b of the cooling passage 60. , and the cooling channel 60 has an inlet 61 a through which the coolant is introduced from the outside of the casing 4 . The curved flow path has a centerline length within a range equal to or less than the diameter of the inlet 61a or the hydraulic diameter, and the direction of the centerline changes from upstream to downstream within a range of 45° or more and 90° or less. is configured as The maximum length of the channel from the bending point of the curved channel to the branch portion 61b of the cooling channel 60 is set to be less than 10 times the diameter or hydraulic diameter of the inlet 61a.

According to this configuration, due to the bent portion 66c of the bent pipe 66 as the bent channel, the main stream velocity of the coolant in the branch portion 61b of the cooling channel 60 is increased to the upper stream speed of the coolant upstream of the bent channel (bent portion 66c). Faster than speed. The cooling effect of the coolant on the casing 4 is improved because the heat transfer coefficient of the branched portion 61b and its immediate downstream side is improved by the speed increase of the main stream of the coolant.

Further, the screw compressor 1A according to the present embodiment further includes a bent pipe 66 connected to the introduction port 61a of the casing 4. The bent pipe 66 includes a first straight pipe portion 66a having a linearly extending flow path, and a second straight pipe portion 66a having a linearly extending flow path and positioned downstream of the first straight pipe portion 66a and connected to the inlet 61a. It has two straight pipe portions 66b and a bent portion 66c connecting the first straight pipe portion 66a and the second straight pipe portion 66b. The flow path of the bent portion 66c is configured as a bent flow path that satisfies the conditions described above.

According to this configuration, by introducing the coolant into the cooling flow path 60 of the casing 4 of the screw compressor 1A through the bent pipe 66, the effect of increasing the speed of the main flow of the coolant at the branch portion 61b can be simplified. can be obtained by configuration.

[Third embodiment]
A screw compressor according to the third embodiment will be described by way of illustration. First, the configuration and structure of a screw compressor according to the third embodiment will be described with reference to FIG. FIG. 9 is a sectional view showing a schematic structure of a screw compressor according to a third embodiment of the invention. In FIG. 9, parts having the same reference numerals as those shown in FIGS. 1 to 8 are the same parts, and detailed description thereof will be omitted.

The screw compressor 1B according to the third embodiment shown in FIG. 9 differs from the first embodiment in that the cooling flow path 60 of the casing 4 is connected to the external cooling system 100 ( (See Fig. 1). The channel of the contraction tube 67 is configured as a contraction channel in which the channel cross-sectional area decreases from upstream to downstream. In the present embodiment, a reduced flow path is arranged on the upstream side of the branch portion 61b (see FIG. 3) of the cooling flow path 60. As shown in FIG.

Specifically, the reduced pipe 67 includes a large-diameter pipe portion 67a connected to the external cooling system 100, a small-diameter pipe portion 67b connected to the inlet 61a of the cooling flow path 60 of the casing 4, and a large-diameter pipe portion 67a and a tapered tube portion 67c connecting the small-diameter tube portion 67b. The large-diameter pipe portion 67a and the small-diameter pipe portion 67b are straight pipe portions extending linearly with a constant flow passage cross-sectional area. set to be large. The tapered pipe portion 67c is a portion in which the channel cross-sectional area decreases from upstream to downstream. It should be noted that the reduction tube 67 can also be configured to directly connect the large-diameter tube portion 67a and the small-diameter tube portion 67b without passing through the tapered tube portion 67c.

discharge side bearings

7 and 8 in the axial direction of the male and

female rotors

2 and 3, 3 overlaps the axially projected area 48p.

Next, the action and effect of this embodiment in which the coolant is introduced into the cooling flow path of the casing through the contraction tube will be described with reference to FIG. FIG. 10 is a diagram showing analysis results of the flow velocity distribution of the coolant in the contraction tube connected to the cooling flow path of the casing in the screw compressor according to the third embodiment of the present invention. In FIG. 10, black and white shading represents the level of the flow velocity of the coolant, and indicates that the flow velocity increases as the color approaches black from white. In addition, the white arrow indicates the direction of the mainstream of the coolant.

As shown in FIG. 10, the flow velocity of the coolant flowing through the contraction pipe 67 is such that the flow velocity in the small diameter pipe portion 67b on the downstream side of the tapered pipe portion 67c is higher than the flow speed in the upstream large diameter pipe portion 67a. . This is because the flow rate of the coolant concentrates in the flow path with the narrowed cross-sectional area. Therefore, when the coolant is introduced into the cooling channel 60 of the casing 4 via the contraction tube 67, the flow velocity of the coolant introduced into the cooling channel 60 increases. Therefore, the flow velocity of the main flow of the coolant also increases in the region of the branch portion 61b of the cooling channel 60 and the first branch channel 63 and the second branch channel 64 immediately downstream thereof (see FIG. 3). This facilitates the generation of a secondary flow in the cross-section perpendicular to the main flow of coolant, further increasing the heat transfer coefficient between the coolant and the wall surface of that region of the casing 4 . Therefore, since the cooling ability of the coolant for the casing 4 is further improved, the thermal deformation of the casing 4 is further suppressed, and the

discharge side bearings

However, if the flow path on the downstream side of the tapered tube portion 67c of the contraction tube 67 is branched, the coolant is divided into the branched flow paths, so the flow velocity in each branched flow path is reduced. . Therefore, it is necessary to provide a configuration in which the flow path does not branch between the tapered tube portion 67c of the contraction tube 67 and the introduction port 61a of the cooling flow path 60 of the casing 4. FIG. That is, it is required not to branch the small-diameter tube portion 67b.

In this embodiment, the reduced pipe 67 connected to the cooling flow path 60 of the casing 4 is space-saving compared to the bent pipe 66 connected to the cooling flow path 60 of the casing 4 in the second embodiment. Therefore, it is more advantageous than the second embodiment when the space in the package containing the screw compressor 1B, the motor 90, etc. is limited.

In addition, in the present embodiment, an example of a configuration in which the contraction pipe 67 is connected to the casing 4 to arrange the contraction passage on the upstream side of the branch portion 61b of the cooling passage 60 is shown. However, instead of connecting the contraction tube 67 to the casing 4 , a configuration is also possible in which a contraction flow path is provided inside the casing 4 . That is, the reduced flow path is arranged at a position upstream of the branch portion 61 b of the cooling flow path 60 inside the casing 4 . As a result, the reduced flow path in the cooling flow path 60 can increase the speed of the coolant, and the heat transfer coefficient at the branch portion 61b of the cooling flow path 60 is improved.

In the third embodiment described above, similarly to the first embodiment, the position between the discharge flow path 48 and the

discharge side bearings

7 and 8 in the axial direction of the male rotor 2 and the female rotor 3 and the discharge By branching the cooling channel 60 at the branching portion 61b that overlaps with the region 48p projected in the axial direction of the channel 48, the heat transfer coefficient is improved in the branching portion 61b of the cooling channel 60 and the region immediately downstream thereof. do. Thereby, the cooling ability of the coolant to the casing 4 is improved. That is, since the cooling capacity of the casing 4 around the

discharge side bearings

7 and 8 is enhanced, the increase in the relative distance between the

discharge side bearings

Further, in the screw compressor 1B according to the present embodiment, the contraction pipe 67 as a contraction passage whose passage cross-sectional area decreases from upstream to downstream is located upstream of the branch portion 61b of the cooling passage 60. The flow path between the reduced flow path and the branch portion 61b of the cooling flow path 60 is configured by a single flow path without branching.

According to this configuration, the main stream velocity of the coolant in the branch portion 61b of the cooling channel 60 is reduced by the contraction pipe 67 as the contraction channel so that the coolant upstream of the contraction channel (the tapered pipe portion 67c of the contraction pipe 67) faster than the mainstream speed of The cooling effect of the coolant on the casing 4 is improved because the heat transfer coefficient of the branched portion 61b and its immediate downstream side is improved by the speed increase of the main stream of the coolant.

Further, in the present embodiment, the cooling flow path 60 has an inlet 61a for introducing a coolant from the outside of the casing 4, and the screw compressor 1B has a reduction pipe 67 connected to the inlet 61a of the casing 4. Prepare more. The channel of the contraction tube 67 is configured as a contraction channel.

According to this configuration, by introducing the coolant into the cooling flow path 60 of the casing 4 of the screw compressor 1B through the contraction pipe 67, the effect of increasing the speed of the main flow of the coolant at the branch portion 61b can be simplified. can be obtained by configuration.

[Other embodiments]
In addition, the present invention is not limited to the above-described embodiments, and includes various modifications. The above-described embodiments have been described in detail for easy understanding of the present invention, and are not necessarily limited to those having all the described configurations. That is, part of the configuration of one embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of one embodiment. Moreover, it is also possible to add, delete, or replace a part of the configuration of each embodiment with another configuration.

In the first to third embodiments described above, the oil-

free screw compressors

1, 1A, and 1B have been described as examples. The present invention can also be applied to a type screw compressor.

Further, in the above-described embodiments, the twin-screw

type screw compressors

1, 1A, and 1B provided with a pair of screw rotors have been described as examples, but multi-screw type screw compressors provided with three or more screw rotors The present invention can also be applied to compressors.

Further, in the embodiment described above, an example of a configuration in which the cooling channel 60 of the casing 4 bifurcates from the introduction channel 61 into the first branch channel 63 and the second branch channel 64 is shown. However, the cooling channel can also be configured to branch from the introduction channel 61 into a plurality of branch channels of three or more. Even with such a configuration, the branching portion 61b where the plurality of branched flow paths branch is positioned between the discharge flow path 48 and the

discharge side bearings

7 and 8 in the axial direction of the male and

female rotors

2 and 3. In addition, by arranging the discharge passage 48 at a position overlapping with the region 48p projected in the axial direction of the male and

female rotors

2 and 3, the discharge passage 48 and the

discharge side bearings

7 and 8 in the casing 4 are separated from each other. It is possible to promote cooling of the region of the hot part in between.

It is also possible to arrange the bent tube 66 of the second embodiment on the downstream side of the contraction tube 67 of the third embodiment described above. In other words, it is possible to arrange the curved flow path downstream of the flow path whose cross-sectional area decreases toward the downstream side upstream of the branch portion 61 b of the cooling flow path 60 . In this configuration, the effect of improving the heat transfer coefficient of the branch portion 61b of the cooling channel 60 can be enhanced by obtaining the speed-increasing effect of the curved channel in addition to the speed-increasing effect of the coolant by the contracted channel.

1, 1A, 1B... screw compressor, 2... male rotor (screw rotor), 3... female rotor (screw rotor), 4... casing, 7, 8... discharge side bearing, 46... storage chamber, 48... discharge flow path 48p... area where the discharge channel is projected in the axial direction, 60... cooling channel, 61... introduction channel, 61a... introduction port, 61b... branch portion, 63... first branch channel, 64... second branch flow Path, 66... curved pipe, 66a... first straight pipe line, 66b... second straight pipe line, 66c... bent portion (bent flow path), 67... reduced pipe (reduced flow path), C... working chamber

Claims

a plurality of screw rotors that rotate to mesh with each other;
a discharge-side bearing that rotatably supports one axial side of each of the plurality of screw rotors;
a casing having an accommodation chamber for accommodating the plurality of screw rotors, the discharge-side bearing being arranged at a position on the one side of the accommodation chamber in the axial direction, and forming an operating chamber together with the plurality of screw rotors; with
The casing is
having a discharge passage that communicates with the one side of the housing chamber in the axial direction and guides the compressed gas in the working chamber to the outside of the casing;
Having a cooling channel through which a coolant supplied from the outside of the casing circulates,
The cooling channel branches from upstream to downstream at the branching portion,
The branching portion is positioned between the discharge flow path and the discharge-side bearing in the axial direction, and is positioned to overlap a region obtained by projecting the discharge flow path in the axial direction.
A screw compressor according to claim 1,
The cooling channel includes an inlet at an upstream end for introducing a coolant from the outside of the casing, and an inlet channel extending from the inlet to the branch,
The screw compressor, wherein the introduction passage is arranged at a position between the discharge passage and the discharge-side bearing in the axial direction and at a position overlapping a region obtained by projecting the discharge passage in the axial direction.
A screw compressor according to claim 1,
The cooling channel includes a first branch channel and a second branch channel that are bifurcated at the branching portion,
The screw compressor, wherein the first branched flow path and the second branched flow path are configured to extend from the branched portion in directions opposite to each other along the circumferential direction of the casing.
A screw compressor according to claim 1,
The cooling channel has an inlet for introducing a coolant from the outside of the casing,
A curved channel for changing the flow direction of the coolant is arranged upstream of the branch portion of the cooling channel,
The bent channel has a centerline length within a range equal to or less than the diameter of the inlet port or a hydraulic diameter, and the direction of the centerline changes from upstream to downstream within a range of 45° or more and 90° or less. is configured to
The screw compressor, wherein the maximum length of the flow path from the bending point of the bending flow path to the bifurcation of the cooling flow path is set to be less than 10 times the diameter or hydraulic diameter of the inlet.
A screw compressor according to claim 4,
further comprising a bent tube connected to the inlet of the casing;
The bent tube is
a first straight pipe portion in which the channel extends linearly;
a second straight pipe portion having a flow path extending linearly, positioned downstream of the first straight pipe portion and connected to the introduction port;
a bending portion connecting the first straight pipe portion and the second straight pipe portion;
The screw compressor, wherein the flow path of the bent portion is configured as the bent flow path.
A screw compressor according to claim 1,
A reduced flow path whose flow path cross-sectional area decreases from upstream to downstream is arranged upstream of the branch portion of the cooling flow path,
The screw compressor, wherein a flow path from the reduced flow path to the branched portion of the cooling flow path is composed of a single flow path without branching.
A screw compressor according to claim 6,
The cooling channel has an inlet for introducing a coolant from the outside of the casing,
further comprising a contraction tube connected to the inlet of the casing;
The screw compressor, wherein the flow path of the reduction tube is configured as the reduction flow path.