JP7146364B2 - centrifugal compressor - Google Patents

Description

The present invention relates to centrifugal compressors.

A centrifugal compressor is known in which a spiral scroll is arranged around an impeller via a diffuser. In this type of centrifugal compressor, the fluid compressed by the impeller is introduced into the scroll through the diffuser, and is appropriately decelerated by the scroll to recover the static pressure. A spiral scroll flow path is formed in the scroll, and a discharge flow path is connected to the end point of the scroll flow path in the flow direction. A starting portion of the scroll channel is connected to a side portion of the discharge channel to form a tongue, and part of the fluid flowing through the discharge channel is guided by the tongue to reenter the scroll channel. inflow and circulate. The scroll flow path is generally formed such that the area is gradually increased in the flow direction from the start point to the end point while keeping the centroid constant (see Patent Literatures 1 and 2).

WO2012/090649 WO2012/132528

In a conventional centrifugal compressor, there is a possibility of causing pressure loss due to reverse flow in the discharge passage, especially when operating at a small flow rate.

An object of the present invention is to provide a centrifugal compressor capable of reducing pressure loss in a discharge passage.

The inventors have found that there is a portion downstream of the tongue portion of the discharge channel where backflow occurs due to separation, and that this backflow causes pressure loss. This separation reduces the flow through the discharge channel by increasing the proportion of the flow that recirculates through the scroll channel rather than into the discharge channel during low flow operation, thereby reducing the flow through the scroll channel. It is thought that this is caused by the rapid expansion of the cross-section of the flow path at the confluence connecting the portion and the discharge flow path. Here, considering the flow rate that decreases due to recirculation, we came up with the idea that backflow can be prevented by narrowing the cross-section of the flow channel to an appropriate cross-sectional area. Conversely, there was concern about an increase in pressure loss during operation. Therefore, when we compared and verified the reduction in pressure loss during low flow rate operation and the increase in pressure loss during high flow rate operation, it was found that even if the cross section of the flow path was narrowed, the decrease in pressure loss during low flow rate operation was relatively large. The present invention was conceived based on the knowledge that the degree of increase in pressure loss during flow rate operation is small.

One aspect of the present invention includes an impeller, and a scroll disposed around the impeller and formed with a flow path, the flow path being a scroll flow path along the rotation direction of the impeller and a scroll flow path. A discharge channel connected to an end point in the rotation direction, and a confluence port connecting a start point portion in the rotation direction of the scroll channel and a side portion of the discharge channel, wherein the flow path extends from the start point along the rotation direction to the confluence port. When the maximum cross-sectional area is defined as the maximum area of the cross-sectional area of the flow path perpendicular to the center line of the flow path in the area up to The centrifugal compressor is provided with a throttle cross-section portion that reduces the cross-sectional area of the flow passage.

In this centrifugal compressor, a throttle cross-section is provided in the region downstream of the confluence port in the discharge flow path. Become.

In some aspects, when the area of the maximum cross section is defined as S1, the area of the throttle cross section is defined as S2, and the area of the minimum cross section where the cross section of the scroll flow path is the smallest is defined as S3, the following formula 1 can be a centrifugal compressor that satisfies
S1-S3≤S2 (Formula 1)

According to this centrifugal compressor, it becomes easy to effectively reduce pressure loss during low flow rate operation while suppressing an increase in pressure loss during high flow rate operation.

In some aspects, the discharge passage comprises an inner portion closer to the axis of rotation of the impeller and an outer portion farther from the axis of rotation, and the restrictor cross-section portion has the inner portion closer to the centerline of the passage. It can be an inwardly recessed centrifugal compressor. Backflow in the ejection channel is considered to be caused by peeling occurring on the inner side of the ejection channel. Further, by recessing the inner portion inwardly, it is possible to reduce the area where separation is likely to occur, which is advantageous for effectively suppressing backflow.

In some aspects, the scroll includes a volute portion in which a scroll channel is formed, a discharge portion in which a discharge channel is formed, and a tongue portion provided along the downstream edge of the confluence port, The throttling section can be a centrifugal compressor that is provided at the portion that contacts the tongue. If the portion in contact with the tongue is a throttled cross-section, the throttled cross-section is provided along the downstream edge of the confluence. As a result, the throttled cross-section is provided close to the confluence. is possible, which is advantageous for effective suppression of backflow. Furthermore, by making the portion in contact with the tongue portion a constricted cross-section portion, the function of guiding the fluid to the confluence port by the tongue portion is improved. As a result, it is advantageous for maintaining and expanding the recirculation flow rate through the scroll flow path, and is advantageous for optimizing the flow rate through the discharge flow path.

One aspect of the present invention includes an impeller, and a scroll disposed around the impeller and formed with a flow path, the flow path being a scroll flow path along the rotation direction of the impeller and a scroll flow path. The scroll has a discharge channel connected to the end point in the direction of rotation, and a confluence port connecting the start point in the direction of rotation of the scroll channel and the side part of the discharge channel. A volute portion, a discharge portion in which a discharge channel is formed, and a tongue portion provided along the downstream edge of the confluence port, the tongue portion protruding inward, which is the center line side of the channel. It can be a centrifugal compressor. In this centrifugal compressor, the tongue protrudes inward on the centerline side of the discharge flow path. As a result, it is easy to prevent backflow of the fluid, especially during operation with a small flow rate, which is advantageous for reducing pressure loss. .

According to some aspects of the present invention, it is possible to reduce pressure loss in the discharge flow path.

1 is a cross-sectional view of a turbocharger provided with a compressor according to an embodiment; FIG. It is a perspective view which shows a scroll. FIG. 3 is a cross-sectional view of the scroll cut along a plane perpendicular to the axis of rotation; FIG. 3 is a virtual perspective view mainly showing the vicinity of a confluence of flow paths formed in a scroll; FIG. 5 is a virtual plan view of a portion corresponding to FIG. 4; It is a figure which shows typically the flow of the discharge flow path which concerns on embodiment. It is a figure which shows typically the flow of the discharge flow path which concerns on a comparative form.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted.

The supercharger 1 is applied, for example, to internal combustion engines of ships and vehicles. As shown in FIG. 1 , the supercharger 1 includes a turbine 2 and a compressor (centrifugal compressor) 3 . The turbine 2 includes a turbine housing 4 and a turbine wheel 16 housed in the turbine housing 4 . The compressor 3 includes a compressor housing 5 and a compressor wheel (impeller) 17 housed in the compressor housing 5 . A turbine wheel 16 is provided at one end of the rotating shaft 14 , and a compressor wheel 17 is provided at the other end of the rotating shaft 14 . A bearing housing 13 is provided between the turbine housing 4 and the compressor housing 5 . The rotary shaft 14 is rotatably supported by the bearing housing 13 via bearings, and the rotary shaft 14 , the turbine wheel 16 and the compressor wheel 17 rotate about the rotation axis X as the integral rotating body 12 .

The turbine housing 4 is provided with an exhaust gas inlet (not shown) and an exhaust gas outlet 10 . Exhaust gas discharged from an internal combustion engine (not shown) flows into the turbine housing 4 through the exhaust gas inlet, rotates the turbine wheel 16, and then flows out of the turbine housing 4 through the exhaust gas outlet 10. do.

The compressor housing 5 is provided with a suction portion 9 and a discharge portion (not shown). When the turbine wheel 16 rotates, the compressor wheel 17 rotates via the rotating shaft 14 . The rotating compressor wheel 17 sucks an external fluid (fluid) such as air through the suction portion 9, compresses it, and discharges (pumps) it from the discharge portion. The compressed fluid discharged from the discharge section is supplied to the aforementioned internal combustion engine.

The compressor housing 5 includes a diffuser 6 arranged around the compressor wheel 17 and a scroll 7 arranged around the diffuser 6 . The scroll 7 includes a volute portion 71 (see FIG. 2) arranged in a single spiral around the compressor wheel 17 and a discharge portion 72 integrally provided with the volute portion 71 . The scroll 7 is formed with a channel 53 through which fluid such as gas introduced from the diffuser 6 passes. The scroll 7 has an inner wall surface facing the flow path 53 .

3 and 4, the flow path 53 of the scroll 7 communicates with the scroll flow path 54 formed inside the volute portion 71 and the scroll flow path 54, and is formed inside the discharge portion 72. and a discharge flow path 55 that is formed. The scroll channel 54 is a channel along the rotation direction Rd of the compressor wheel 17 . A start point portion 54a of the scroll flow path 54 is an upstream end opposite to the rotational direction Rd, and an end point portion 54b is a downstream end along the rotational direction Rd. The starting point 54a of the scroll flow path 54 is positioned at the winding start part 71a of the volute part 71, and the part at which the end point part 54b is positioned is the winding ending part 71b of the volute part 71.

A discharge channel 55 is connected to the end point portion 54b of the scroll channel 54 so as to follow the flow of the fluid. The discharge channel 55 is a channel in which the flow is mainly formed in a direction other than the direction along the rotation direction Rd. The flow in a direction other than along the direction of rotation Rd is, for example, a flow in a direction tangential to the direction of rotation Rd, but is not limited to this flow. and the direction may change. That is, the end point portion 54b of the scroll flow path 54 to which the discharge flow path 55 is connected can also be expressed as a portion where the flow direction of the fluid is switched from the rotation direction Rd to another direction.

A winding start portion 71a of the volute portion 71 is connected to a side portion of the discharge portion 72, and a starting portion 54a of the scroll flow path 54 is connected to a side portion 56 of the discharge flow path 55 so as to be communicable. A connection portion between the starting point portion 54a of the scroll flow path 54 and the side portion 56 of the discharge flow path 55 is a confluence port where part of the fluid flowing through the discharge flow path 55 reenters the scroll flow path 54 and becomes a recirculation flow. 57. When the side portion 56, which is the outer periphery of the discharge passage 55, is divided into a side closer to the compressor wheel 17 and a side farther from the compressor wheel 17, the closer side is the inner side 56a and the far side is the outer side 56b. . The confluence port 57 is provided in the inner portion 56a.

A tongue portion 73 is formed at the winding start portion 71a. The tongue portion 73 is provided along the downstream edge of the confluence port 57, and is directed inward toward the center line La side (see FIG. 5) of the flow path 53 compared to the downstream edge of the confluence port 57. protruding. The center line La of the channel 53 means a line connecting centroids of respective channel cross sections when channel cross sections that are continuous in the flow direction are defined. The edge of the confluence port 57 on the downstream side is defined by dividing the entire outer edge (edge) of the confluence port 57 into two parts, for example, an upstream side and a downstream side, based on the flow of fluid passing through the discharge flow path 55 . divide, meaning the portion of the downstream edge in that case. In addition, the tongue portion 73 may be formed on the entire edge of the downstream side, or may be formed on a part of the edge.

As described above, the flow path 53 formed in the scroll 7 includes the scroll flow path 54 and the discharge flow path 55. , its cross-sectional shape and cross-sectional area change according to each position along the direction of fluid flow. Specifically, the flow passage cross section of the scroll flow passage 54 has the smallest cross-sectional area in the vicinity of the starting point portion 54a, and gradually expands along the rotation direction Rd. The discharge channel 55 gradually expands from the end point 54 b of the scroll channel 54 to the confluence port 57 along the flow direction, but once shrinks at the position of the tongue portion 73 provided along the confluence port 57 . The cross section of the discharge channel 55 on the downstream side of the tongue portion 73 may be constant in the flow direction or may be gradually enlarged.

As described above, in the flow path 53 according to the present embodiment, the maximum cross-sectional portion 53a, which has the maximum flow path cross section, is larger than the confluence port 57 in the region from the starting point portion 54a to the confluence port 57 along the rotation direction Rd. It is the upstream side in the flow direction and the portion immediately before the confluence port 57 . On the other hand, the portion where the tongue portion 73 is provided is the throttle cross-section portion 53b having a flow passage cross-sectional area smaller than that of the maximum cross-section portion 53a. In addition, in the vicinity of the starting point portion 54 a of the scroll flow path 54 , at least in the scroll flow path 54 , a minimum cross-sectional area 53 c having the smallest cross-sectional area of the flow path is provided.

When the main goal is to reduce the pressure loss during operation with a small flow rate, the area ratio of the throttle cross section 53b to the area of the maximum cross section 53a (100%) can be, for example, 95% or less, or 80%. The following are desirable. On the other hand, it is desirable that the area ratio of the narrowed cross-section portion 53b to the area (100%) of the maximum cross-section portion 53a is 75% or more.

Next, the technical significance of providing the narrowed cross-sectional portion 53b in the downstream region of the discharge flow path 55 from the confluence port 57 will be described with reference to FIGS. 6 and 7. FIG. FIG. 6 is a diagram schematically showing the flow of the discharge channel 55 according to this embodiment, and FIG. 7 is a diagram schematically showing the flow of the discharge channel according to the comparative embodiment.

A portion of the fluid flowing through the discharge channels 55, 105 re-enters the scroll channels 54, 104 through the confluence ports 57, 107 to form recirculation flows. As a result, in the area downstream of the confluence ports 57 and 107, the flow rate is reduced. See) creates an environment where it is easy to peel off from the inner wall surface. As shown in FIG. 7, in the discharge flow path 105 according to the comparative embodiment, since a portion corresponding to the throttle cross-section is not formed, the flowing fluid separates from the inner wall surface and backflow occurs, resulting in pressure loss. growing. This separation reduces the flow rate through the discharge section by increasing the proportion of flow recirculating through the scroll flow path 104 rather than toward the discharge flow path 105 during low flow operation, resulting in a reduced flow rate through the scroll flow path. It is considered that this is caused by the rapid expansion of the channel cross-section at the junction 107 that connects the starting point of 104 and the discharge channel 105 .

On the other hand, in the discharge channel 55 (see FIG. 6) according to the present embodiment, a narrowed cross-sectional area 53b that intentionally narrows the cross-sectional area of the channel is provided in a region downstream of the confluence port 57 . By providing the throttle cross section 53b, it is possible to set an appropriate cross section in consideration of the flow rate that decreases due to recirculation. Prevents backflow and reduces pressure loss.

The above is an advantage mainly when operating with a small flow rate, but when operating with a large flow rate, the provision of the throttle cross section 53b increases the flow velocity, and conversely, there is concern about an increase in pressure loss. However, when we compared and verified the reduction in pressure loss during low-flow operation and the increase in pressure loss during high-flow operation, we found that even if the cross-section of the flow path was narrowed, the reduction in pressure loss during low-flow operation was large. It was confirmed that the degree of increase in pressure loss during flow rate operation was small.

The operation at a small flow rate means, for example, an operating point close to the operating limit of the small flow rate side in the operable range of the compressor 3. Even if there is, it depends on the rotation speed. Also, the high flow rate operation means, for example, an operating point close to the operation limit on the large flow side in the operable range of the compressor 3 .

Further, in this embodiment, when the cross-sectional area of the maximum cross-sectional portion 53a is defined as S1, the cross-sectional area of the narrowed cross-sectional portion as S2, and the cross-sectional area of the minimum cross-sectional portion 53c as S3, the flow path 53 is defined by the following formula (1) meet.

S1-S3≤S2 (Formula 1)

Supplementing formula (1), if the cross-sectional area S2 of the throttle section is too small, the increase in pressure loss during high-flow operation is greater than the decrease in pressure loss during low-flow operation. It becomes difficult to optimize the road cross section. Here, if the cross-sectional area S2 is designed so as to satisfy the above formula (1), it becomes easier to optimize the flow passage cross-section in consideration of the pressure loss during high-flow operation, and the pressure during high-flow operation is reduced. It becomes easier to effectively reduce the pressure loss during operation with a small flow rate while suppressing an increase in loss.

In addition, the narrowed cross-section portion 53b according to the present embodiment has an inner portion 56a recessed inward on the center line La side of the flow path 53 . The backflow in the discharge channel 55 is considered to be caused by peeling occurring on the inner portion 56 a side of the discharge channel 55 . In other words, by recessing the inner portion 56a toward the center line La, it is possible to reduce the area where separation is likely to occur, which is advantageous for effectively suppressing backflow.

Further, in the present embodiment, the tongue portion 73 protrudes inward of the discharge flow path 55, and the projection of the tongue portion 73 forms the throttle cross-sectional portion 53b. That is, the throttle cross-section portion 53b is provided in a portion in contact with the tongue portion 73, and is provided along the edge of the confluence port 57 on the downstream side. In other words, the throttle cross section 53b is provided close to the confluence port 57, which is advantageous for effectively suppressing backflow. Further, by making the portion in contact with the tongue portion 73 the narrowed cross-sectional portion 53b, the function of introducing the fluid by the tongue portion 73, that is, the function of guiding the fluid flowing through the discharge flow path 55 to the confluence port 57 is improved. As a result, it is advantageous to maintain and increase the recirculation flow rate through the scroll flow path 54 and to optimize the flow rate through the discharge flow path 55 .

In the present embodiment, as described above, the narrowed cross-section portion 53b is provided at the portion in contact with the tongue portion 73, but the position at which the narrowed cross-section portion 53b is provided is not limited to the portion in contact with the tongue portion 73. It can also be provided downstream of the port 57 and away from the confluence port 57 . According to this form, it is possible to prevent backflow from occurring downstream of the throttle cross section 53b. In addition, in the present embodiment, as a suitable example, for example, a form in which the inner portion 56a of the throttle cross-section portion 53b is recessed inward on the side of the center line La of the flow path 53 has been described. It can also have a shape that is recessed inward.

The present invention can be embodied in various forms with various modifications and improvements based on the knowledge of those skilled in the art, including the embodiment described above. Moreover, it is also possible to configure modifications of each embodiment using the technical matters described in the above-described embodiments. You may use it, combining the structure of each embodiment suitably.

Moreover, the present invention is not limited to being applied to a supercharger for automobiles, and may be applied to ships and the like. Furthermore, it may be applied to centrifugal compressors other than superchargers.

7 scroll 17 compressor wheel (impeller)
53 Flow path 53a Maximum cross section 53b Constricted cross section 53c Minimum cross section 54 Scroll flow path 54a Starting point portion 54b Ending point portion 55 Discharge flow path 56 Side portion 56a Inner portion 56b Outer portion 57 Confluence port Rd Rotational direction La Center line

Claims (2)

An impeller, and a scroll arranged around the impeller and formed with a flow path through which gas passes,
The flow path is connected to a scroll flow path in which a flow is formed along the rotational direction of the impeller, and an end point portion of the scroll flow path in the rotational direction, and forms a flow in a direction other than the rotational direction. and a confluence port connecting a starting point portion of the scroll flow path in the rotational direction and a side portion of the discharge flow path,
In the region from the starting point portion to the confluence along the direction of rotation, a portion located upstream of the confluence and having a maximum cross-sectional area of the flow passage perpendicular to the center line of the flow passage. is the maximum cross-sectional area, in the downstream region of the discharge flow path from the confluence, the narrowed cross-sectional area where the cross-sectional area of the flow path is smaller than the maximum cross-sectional area is the downstream of the confluence. is provided along the edge of the side, and is provided so as to be recessed inward, which is on the center line side of the flow path, from the downstream edge of the confluence port ,
When the area of the maximum cross section is defined as S1, the area of the throttle cross section is defined as S2, and the area of the minimum cross section where the cross section of the scroll flow path is the smallest is defined as S3, the following formula 1 is satisfied. centrifugal compressor.
S1-S3≤S2 (Formula 1) The discharge passage has an inner portion closer to the rotation axis of the impeller and an outer portion farther from the rotation axis,
2. The centrifugal compressor according to claim 1 , wherein said throttle cross-sectional portion is recessed inwardly on the centerline side of said flow path.

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