JP5369723B2 - Centrifugal compressor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To maintain the performance of compressor efficiency or the like of a centrifugal compressor 1 while making the centrifugal compressor 1 compact and lighter in weight, even when part of high-pressure air is allowed to return from a scroll flow path 21 side to an inlet side of an impeller 7 in consideration of surging. <P>SOLUTION: A throttling part 25 gradually reduced in inner diameter toward a downstream side is formed near the upstream side of the impeller 7 in a shroud wall 5 of a casing 3. A bypass flow path 27 is formed inside the casing 3 to provide communication between the scroll flow path 21 and the inlet side of the impeller 7. A downstream end 29d of an opening 29 of the bypass flow path 27 is situated at the same position with the upstream end 25u of the throttling part 25 in the axial direction of the casing 3 or upstream of the upstream end 25u of the throttling part 25. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a centrifugal compressor that is used in a supercharger such as a supercharger for a vehicle and compresses a gas such as air using centrifugal force.

  In recent years, various developments have been made on centrifugal compressors used in superchargers for vehicles. The configuration of the centrifugal compressor according to the prior art will be described as follows.

  That is, the centrifugal compressor according to the prior art includes a casing, and the casing has a shroud wall inside. Further, an impeller is rotatably provided in the shroud wall of the casing. The impeller includes a hub that can rotate around an axis (an impeller axis, in other words, an axis of the casing), and the impeller. The blade includes a plurality of blades which are provided on the outer peripheral surface of the hub at intervals and whose outer edges extend along the shroud wall of the casing. The hub is linked to a turbine wheel in the vehicle supercharger via a turbine shaft.

  An air supply port for supplying air (an example of gas) is formed at the upstream peripheral edge of the shroud wall of the casing, and compressed high-pressure air (an example of high-pressure gas) is provided at the downstream peripheral edge of the shroud wall of the casing. ) Is exhausted. In the casing, a bypass flow path is formed so as to communicate with the exhaust flow path and the inlet side of the impeller, and this bypass flow path has an opening (return port) opened on the inlet side of the impeller. ing. Furthermore, a bypass valve mechanism for opening and closing the bypass flow path is provided at an appropriate position of the casing.

  Therefore, by rotating the turbine wheel, the blades are rotated together with the hub, in other words, by rotating the impeller, the air supplied from the air supply port to the impeller side is compressed using centrifugal force. can do. The compressed high-pressure air is exhausted from the exhaust passage.

  During operation of the centrifugal compressor, if air is no longer supplied from the air supply port due to, for example, accelerator off, the bypass valve mechanism opens the bypass flow path, and part of the high-pressure air from the exhaust flow path side to the impeller inlet side (One mode in which high-pressure air flows out to the inlet side of the impeller). Thereby, it can prevent that a centrifugal compressor rushes into surging.

Japanese Utility Model Publication No. 61-33918

  By the way, when the position of the opening of the bypass flow path is close to the impeller, the bypass flow path is closed by the bypass valve mechanism, that is, in the normal operation state of the centrifugal compressor, The air turbulent due to the interference flows into the impeller, and the performance such as the compressor efficiency of the centrifugal compressor is lowered.

  On the other hand, if the position of the opening of the bypass channel is moved away from the impeller in order to suppress the deterioration of the performance of the centrifugal compressor, the axial length of the casing becomes long, leading to an increase in size and weight of the centrifugal compressor. Become.

  In other words, it is extremely difficult to maintain the performance of the centrifugal compressor while reducing the size and weight of the centrifugal compressor when high pressure air can flow out to the inlet side of the impeller in consideration of surging. There's a problem.

  Then, an object of this invention is to provide the centrifugal compressor of a novel structure which can solve the above-mentioned problem.

A feature of the present invention is a centrifugal compressor that is used in a supercharger and compresses gas by utilizing centrifugal force. A casing having a shroud wall on the inside thereof, and a casing that is rotatably provided in the shroud wall of the casing. And an impeller provided with a plurality of blades that are rotatable about an axis and provided on the outer peripheral surface of the hub at intervals in the circumferential direction and whose outer edges extend along the shroud wall of the casing. And an air supply port (intake port) for supplying (inhaling) gas to the upstream peripheral edge of the shroud wall of the casing is formed, and the inner diameter of the air supply port gradually decreases toward the downstream side. and each other and reduced in diameter, the exhaust passage for exhausting the high-pressure gas compressed in the downstream edge of the shroud wall of the casing is formed, near the upstream side of the impeller in the shroud wall of the casing Narrowed portion gradually reduced in diameter to the inner diameter toward the downstream side is formed, the shroud wall of the casing has a portion parallel to the axial direction of the casing between the narrowed portion and the air inlet, the A high-pressure gas passage capable of circulating high-pressure gas is formed inside the casing, and the high-pressure gas passage opens to the inlet side of the impeller and can be connected to and shut off from a high-pressure gas supply source that supplies high-pressure gas has a section, the length of the blade in the axial direction of the casing L1, the length from the leading edge of the blade in the axial direction to the downstream end of the opening of the high-pressure gas flow path when the L2 , (L2 / L1) <1.5, and the downstream end of the opening of the high-pressure gas flow path is the same position as the upstream end of the throttle in the axial direction or Upstream end of the throttle Located in remote upstream, the opening of the high-pressure gas passage is directed to subject matter that are located in the parallel portions of the shroud wall of the casing.

  Here, the relationship of (L2 / L1) <1.5 is established because the position of the opening of the high-pressure gas flow path is too far from the impeller, and the axial length of the casing is long. Because it becomes.

  In the claims and the description, the “upstream side” refers to the upstream side when viewed from the flow direction of the mainstream gas, and the “downstream side” refers to the flow direction of the mainstream gas. This is the downstream side. In addition, the “plurality of blades” may be composed of a plurality of types of blades having different axial lengths. In this case, the “length of the blade” is the length of the blade having the longest axial length. That is, “the leading edge of the blade” refers to the leading edge of the blade having the longest axial length.

  According to a feature of the present invention, a plurality of the blades are rotated integrally with the hub, in other words, the impeller is rotated so that the gas supplied from the air supply port to the impeller side is subjected to centrifugal force. Can be compressed. The compressed high-pressure gas is exhausted from the exhaust passage.

  During operation of the centrifugal compressor, when gas is no longer supplied from the supply port due to, for example, accelerator off, the opening of the high-pressure gas flow path is connected to the high-pressure gas supply source, and the high-pressure gas A high-pressure gas is allowed to flow from the supply source side to the inlet side of the impeller. Thereby, it can prevent that the said centrifugal compressor rushes into surging.

  In addition to the above-described action, the throttle portion having an inner diameter gradually reduced toward the downstream side is formed in the shroud wall of the casing in the vicinity of the upstream side of the impeller, and downstream of the opening portion of the high-pressure gas flow path. Since the end is located at the same position as the upstream end of the throttle part in the axial direction or upstream of the upstream end of the throttle part, the rectification action due to the contracted flow is effectively exhibited in the vicinity of the inlet of the impeller. be able to. Thus, the state in which the opening of the high-pressure gas flow path is blocked by the high-pressure gas source without moving the opening of the high-pressure gas flow path away from the impeller, in other words, the centrifugal compressor In a normal operation state, it is possible to suppress the flow gas turbulent due to interference with the opening of the high-pressure gas flow path from flowing into the impeller.

  According to the present invention, even if the opening of the high-pressure gas passage is not kept away from the impeller, the centrifugal compressor is disturbed by interference with the opening of the high-pressure gas passage in a normal operating state. Since the flow gas can be suppressed from flowing into the impeller, as described above, even when the high pressure gas can be discharged to the inlet side of the impeller in consideration of surging, the centrifugal compressor is made compact and lightweight. While maintaining the above, it is possible to maintain the performance such as the compressor efficiency of the centrifugal compressor.

It is a typical sectional side view of the centrifugal compressor which concerns on 1st Embodiment. It is a typical sectional side view of the principal part of the centrifugal compressor which concerns on 2nd Embodiment. It is a typical sectional side view of the principal part of the centrifugal compressor which concerns on 3rd Embodiment. It is a typical sectional side view of the principal part of the centrifugal compressor which concerns on a 1st comparative example. It is a typical sectional side view of the principal part of the centrifugal compressor which concerns on a 2nd comparative example. It is a figure which shows the compressor efficiency in the case of Examples 1-3 and the case of Comparative Examples 1 and 2.

[First Embodiment]
A first embodiment will be described with reference to FIG.

  Here, FIG. 1 is a schematic sectional side view of the centrifugal compressor according to the first embodiment. In the drawings, “F” indicates the forward direction, and “R” indicates the backward direction.

  As shown in FIG. 1, a centrifugal compressor 1 according to the first embodiment is used for a supercharger for a vehicle, and compresses air (an example of gas) using centrifugal force. And the specific structure of the centrifugal compressor 1 which concerns on 1st Embodiment is as follows.

  The centrifugal compressor 1 includes a casing 3, and the casing 3 has a shroud wall 5 inside. The casing 3 is integrally attached to another casing (not shown).

  An impeller 7 is rotatably provided in the shroud wall 5 of the casing 3. Specifically, a hub 9 is provided in the shroud wall 5 of the casing 3, and the outer peripheral surface of the hub 9 gradually increases from the axial direction of the casing 3 (in other words, the axial direction of the impeller 7). The casing 3 extends outward in the radial direction of the casing 3 (in other words, the radial direction of the impeller 7). Further, the hub 9 is rotatable around the axis of the impeller 7 (in other words, the axis of the casing 3), and the turbine shaft 11 is attached to a turbine wheel (not shown) rotatably provided in another casing. It is linked and connected through. Furthermore, on the outer peripheral surface of the hub 9, a plurality of (only one) long blade (full blade) 13 and a plurality (one only) short blade (splitter blade) 15 are spaced apart in the circumferential direction. Are provided alternately. Here, the front edge of the long blade 13 is located on the upstream side (front side) of the front edge of the short blade 15, and the outer edge of the long blade 13 and the outer edge of the short blade 15 are the shroud wall 5 of the casing 3. It extends so that. Instead of using two types of blades 13 and 15 having different axial lengths, blades having the same axial length may be used.

  An air supply port (suction port) 17 for supplying air to the impeller 7 side (suction port) 17 is formed at the upstream peripheral edge (inlet peripheral edge of the impeller 7) of the shroud wall 5 of the casing 3. An annular diffuser flow path 19 (one of the exhaust flow paths) for decelerating and exhausting compressed high-pressure air (an example of high-pressure gas) is formed at the downstream peripheral edge of the shroud wall 5 (exit-side peripheral edge of the impeller 7). Has been. A spiral scroll channel 21 (one of the exhaust channels) for exhausting high-pressure air is formed on the peripheral side of the diffuser channel 19 inside the casing 3. A discharge port 23 for discharging high-pressure air is formed at an appropriate position of the casing 3, and this discharge port 23 communicates with the scroll flow path 21 and the diffuser flow path 19, and is used for intake air of the internal combustion engine. It is connected to a manifold (not shown).

A bypass passage 27 as a high-pressure gas passage through which high-pressure gas can flow is formed at an appropriate position inside the casing 3 so as to connect the scroll passage 21 and the inlet side of the impeller 7. The passage 27 has an opening (return port) 29 that opens to the inlet side of the impeller 7. Further, a bypass valve mechanism 31 for opening and closing the bypass flow path 27 is provided at an appropriate position on the front side of the casing 3, and the bypass valve mechanism 31 has a known configuration as shown in Patent Document 1 described above. It comprises an actuator 35 that operates the valve body 33 and the valve body 33 in accordance with the driving state of the vehicle. Here, by opening and closing the bypass flow path 27 by the bypass valve mechanism 31, the opening 29 of the bypass flow path 27 is connected to and disconnected from the scroll flow path 21 as a high pressure gas supply source for supplying high pressure air (communication and communication). Blocking) is possible.

  A throttle portion 25 is formed in the shroud wall 5 of the casing 3 in the vicinity of the upstream side (front side) of the impeller 7, and the inner diameter of the throttle portion 25 is gradually reduced toward the downstream side. Further, the taper angle (gradient angle) θ of the throttle portion 25 with respect to the axis of the casing 3 (in other words, the axis of the impeller 7) is set to 30 ° or less (preferably 20 ° or less). Specifically, in the first embodiment, when the taper angle θ of the throttle portion 25 is 20 °, the inner diameter of the downstream end 25d of the throttle portion 25 is R1, and the inner diameter of the upstream end 25u is R2, (R2 /R1)=1.12. Here, the taper angle θ of the throttle portion 25 is set to 30 ° or less because if the taper angle θ of the throttle portion 25 exceeds 30 °, there is a concern about the disturbance of the air flow due to the collision with the throttle portion 25. It is.

  The length of the long blade 13 in the axial direction of the casing 3 (in other words, the axial direction of the impeller 7) is L1, and the downstream edge of the opening 29 of the bypass channel 27 from the front edge of the long blade 13 in the axial direction of the casing 3 When the length up to 29d is L2, the relationship of (L2 / L1) <1.5 is established. Specifically, in the first embodiment, (L2 / L1) = 0.48 is set. Here, the relationship of (L2 / L1) <1.5 is established because the position of the opening 29 of the bypass channel 27 is too far from the impeller 7 and the axial length of the casing 3 becomes long. Because.

  The downstream end 29 d of the opening 29 of the bypass channel 27 is located at the same position as the upstream end 25 u of the throttle portion 25 in the axial direction of the casing 3. Instead of the downstream end 29d of the opening 29 of the bypass channel 27 being located at the same position as the upstream end 25u of the throttle 25, the downstream end 29d may be positioned upstream of the upstream end 25u of the throttle 25. Absent.

  Then, the effect | action and effect of 1st Embodiment are demonstrated.

  By rotating the turbine shaft 11 by the rotation of the turbine wheel, the plurality of blades 13 and 15 are rotated integrally with the hub 9, in other words, the impeller 7 is rotated. Thereby, the air supplied to the impeller 7 side from the air supply port 17 can be compressed using centrifugal force. The compressed high-pressure air is exhausted from the diffuser flow path 19 and the scroll flow path 21 and sent to the intake manifold of the internal combustion engine via the discharge port 23.

  During operation of the centrifugal compressor 1, when air is no longer supplied from the air supply port 17 due to, for example, accelerator off, the bypass flow path 27 is opened by the bypass valve mechanism 31, and high pressure air is supplied from the scroll flow path 21 side. The part is returned to the inlet side of the impeller 7 (one mode in which high-pressure air flows out to the inlet side of the impeller 7). Thereby, it can prevent that the centrifugal compressor 1 rushes into surging.

  In addition to the above-described action, a constricted portion 25 whose inner diameter is gradually reduced toward the downstream side is formed near the upstream side of the impeller 7 in the shroud wall 5 of the casing 3, and downstream of the opening 29 of the bypass flow path 27. Since the end 29d is located at the same position as the upstream end 25u of the throttle portion 25 in the axial direction of the casing 3 or upstream of the upstream end of the throttle portion, the effect of rectification by contraction is effective in the vicinity of the inlet of the impeller 7. Can be demonstrated. Thus, even if the opening 29 of the bypass channel 27 is not moved away from the impeller 7, the state in which the opening 29 of the bypass channel 27 is blocked by the scroll channel 21, in other words, the normal state of the centrifugal compressor 1. In the operating state, it is possible to suppress the flow air turbulent due to interference with the opening 29 of the bypass channel 27 from flowing into the impeller 7.

  Therefore, according to the first embodiment, as described above, even in the case where part of the high-pressure air can be returned from the scroll flow path 21 side to the inlet side of the impeller 7 in consideration of surging, the centrifugal compressor 1 While achieving compactness and weight reduction, the performance such as the compressor efficiency of the centrifugal compressor 1 can be maintained (see examples described later).

[Second Embodiment]
A second embodiment will be briefly described with reference to FIG.

  Here, FIG. 2 is a schematic cross-sectional side view of the main part of the centrifugal compressor according to the second embodiment. In the drawings, “F” indicates the forward direction, and “R” indicates the backward direction.

  As shown in FIG. 2, the centrifugal compressor 37 according to the second embodiment is configured such that (L2 / L1) = 1.08, (R2 / R1) = 1.20, and θ = 18 °. It has the same configuration as the centrifugal compressor 1 according to the first embodiment. And also in 2nd Embodiment, there exists an effect | action and effect similar to 1st Embodiment.

[Third Embodiment]
A third embodiment will be briefly described with reference to FIG.

  Here, FIG. 3 is a schematic side cross-sectional view of the main part of the centrifugal compressor according to the third embodiment. In the drawings, “F” indicates the forward direction, and “R” indicates the backward direction.

  As shown in FIG. 3, the centrifugal compressor 39 according to the third embodiment is configured with (L2 / L1) = 0.46, (R2 / R1) = 1.20, and θ = 31 °, It has the same configuration as the centrifugal compressor 1 according to the first embodiment. And in 3rd Embodiment, there exists the same effect | action and effect as 1st Embodiment.

  The present invention is not limited to the description of the above-described embodiment. For example, instead of making the cross-sectional shape of the narrowed portion 25 linear, it can be implemented in various other forms. is there. Further, the scope of rights encompassed by the present invention is not limited to these embodiments.

(Comparative example)
Before describing the specific contents of the examples, the centrifugal compressors according to Comparative Examples 1 and 2 will be described with reference to FIGS. 4 and 5.

  Here, FIG. 4 is a schematic side sectional view of the main part of the centrifugal compressor according to the first comparative example, and FIG. 5 is a schematic side sectional view of the main part of the centrifugal compressor according to the second comparative example. It is. In the drawings, “F” indicates the forward direction, and “R” indicates the backward direction.

  As shown in FIG. 4, the centrifugal compressor 41 according to the first comparative example is different from the centrifugal compressors 1, 37, and 39 according to the first to third embodiments, and the downstream end 29 d of the opening 29 of the bypass flow path 27. Is positioned downstream of the upstream end 25u of the throttle portion 25. Further, (L2 / L1) = 0.48, (R2 / R1) = 1.20, and θ = 18 ° are set.

  As illustrated in FIG. 5, the centrifugal compressor 43 according to the second comparative example is different from the centrifugal compressors 1, 37, and 39 according to the first to third embodiments, and the throttle unit 25 is omitted. Further, (L2 / L1) = 0.48 is set.

(Specific contents)
The centrifugal compressors 1, 37 and 39 according to the first to third embodiments are the cases of Examples 1 to 3, and the centrifugal compressors 41 and 43 according to the first and second comparative examples are the cases of Comparative Examples 1 and 2. In each case, when the compressor efficiency is obtained by CFD (Computational Fluid Dynamics) analysis, it is as shown in FIG. Here, FIG. 6 is a diagram showing the compressor efficiency in the cases of Examples 1 to 3 and Comparative Examples 1 and 2, and the compressor efficiency in the case of Example 1 is used as an index (reference).

According to the CFD analysis result, it was confirmed that the compressor efficiency was higher in the cases of Examples 1 to 3 than in the cases of Comparative Examples 1 and 2.

DESCRIPTION OF SYMBOLS 1 Centrifugal compressor 3 Casing 5 Shroud wall 7 Impeller 13 Long blade 15 Short blade 17 Air supply port 19 Diffuser flow path 21 Scroll flow path 23 Discharge port 25 Restriction part 25d Downstream end 25u Upstream end 27 Bypass flow path 29 Opening part 29d Downstream End 31 Bypass valve mechanism 37 Centrifugal compressor 39 Centrifugal compressor

Claims (3)

In a centrifugal compressor that is used in a supercharger and compresses gas using centrifugal force,
A casing having a shroud wall on the inside;
A hub rotatably provided in the shroud wall of the casing and rotatable about an axis, and a circumferentially spaced outer peripheral surface of the hub and having an outer edge along the shroud wall of the casing An impeller having a plurality of blades extending in a manner
An air supply port for supplying gas is formed at the upstream peripheral edge of the shroud wall of the casing, and the air supply port is gradually reduced in inner diameter toward the downstream side, and the shroud wall of the casing An exhaust passage for exhausting compressed high-pressure gas is formed on the downstream peripheral edge of the
In the shroud wall of the casing, a narrowed portion is formed in which the inner diameter is gradually reduced toward the downstream side in the vicinity of the upstream side of the impeller,
The shroud wall of the casing has a portion parallel to the axial direction of the casing between the air supply port and the throttle portion ,
A high-pressure gas passage capable of circulating high-pressure gas is formed inside the casing, and the high-pressure gas passage is open to the inlet side of the impeller and can be connected to and shut off from a high-pressure gas supply source that supplies high-pressure gas. Has an opening,
When the length of the blade in the axial direction of the casing is L1, and the length from the leading edge of the blade in the axial direction to the downstream end of the opening of the high-pressure gas flow path is L2, (L2 / L1 ) <1.5 relationship has been established,
The downstream end of the opening of the high-pressure gas channel is located at the same position as the upstream end of the throttle portion in the axial direction or upstream of the upstream end of the throttle portion,
The centrifugal compressor characterized in that the opening of the high-pressure gas flow path is located in the parallel portion of the shroud wall of the casing .   2. The centrifugal compressor according to claim 1, wherein a taper angle of the throttle portion with respect to an axis of the casing is set to 30 ° or less.   The high-pressure gas supply source is the exhaust flow path, and the high-pressure gas flow path is a bypass flow path formed so as to connect the exhaust flow path and the inlet side of the impeller to the casing, The centrifugal compressor according to claim 1 or 2, wherein a bypass valve mechanism for opening and closing the bypass flow path is provided in the casing.

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