Centrifugal compressor and passage design method therefor

Abstract

To uniformize static pressure distribution in a circumferential direction inside of a scroll.SOLUTION: A centrifugal compressor comprises a scroll. The scroll includes: a scroll passage 28 extending in a circumferential direction with a rotation axis X defined as a reference; a discharge passage 32 extending from a downstream end 28B of the scroll passage 28 in a direction that is different from the circumferential direction; and a communication port 33 communicating between an upstream end 28A of the scroll passage 28 and the discharge passage 32. The discharge passage 32 includes an upstream portion 32A from an upstream end of the discharge passage 32 to the communication port 33 and a downstream portion 32B from the communication port 33 to a downstream end of the discharge passage 32. A cross-sectional area of the scroll passage 28 on a cross section that is cut by a plane including the rotation axis X increases from the upstream end to the downstream end of the scroll passage 28. A cross-sectional area of the upstream portion 32A on a cross section that is cut by a plane including the rotation axis X increases with a fixed inclination from an upstream end to a downstream end of the upstream portion 32A.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a centrifugal compressor and a flow path design method thereof. [Background technology]

[0002] BACKGROUND ART Conventionally, centrifugal compressors are known that are used in superchargers for internal combustion engines, gas turbine engines, pumps for compressing fluids, and the like.

[0003] For example, Patent Document 1 discloses a centrifugal compressor including an impeller and a scroll disposed around the impeller. The scroll includes a scroll passage in which a flow is formed along the rotation direction of the impeller, a discharge passage connected to the end of the scroll passage and in which a flow is formed in a direction other than the rotation direction, and a junction port connecting the start of the scroll passage and a side of the discharge passage. The discharge passage is provided with a tongue along the downstream edge of the junction port. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 7146364 Summary of the Invention [Problem to be solved by the invention]

[0005] In Patent Document 1, the cross section of the discharge passage is locally narrowed at the tongue portion. As a result, the static pressure inside the scroll changes suddenly around the tongue portion, resulting in an uneven distribution of static pressure in the circumferential direction inside the scroll. As a result, the stall characteristics (resistance to stall occurrence) of the centrifugal compressor deteriorate, and there is a risk that the operating range of the centrifugal compressor will become narrow.

[0006] In view of the above background, an object of the present invention is to provide a centrifugal compressor that can improve stall characteristics and widen the operating range by making the static pressure distribution in the circumferential direction inside the scroll uniform. [Means for solving the problem]

[0007] In order to solve the above-mentioned problems, one aspect of the present invention is a centrifugal compressor (6), comprising: an impeller (22) rotatable about a rotation axis (X); and a scroll (23) arranged around the impeller, wherein the scroll has a scroll passage (28) extending in a circumferential direction based on the rotation axis, a discharge passage (32) extending from a downstream end of the scroll passage in a direction different from the circumferential direction, and a communication port (33) connecting an upstream end of the scroll passage and the discharge passage, wherein the discharge passage has an upstream portion (32A) extending from the upstream end of the discharge passage to the communication port, and a downstream portion (32B) extending from the communication port to the downstream end of the discharge passage, wherein a cross-sectional area of ​​the scroll passage in a cross section taken along a plane including the rotation axis increases from the upstream end to the downstream end of the scroll passage, and a cross-sectional area of ​​the upstream portion in a cross section taken along the plane including the rotation axis increases at a constant gradient from the upstream end to the downstream end of the upstream portion.

[0008] According to this aspect, by appropriately setting the cross-sectional area schedule of the upstream portions of the scroll passage and the discharge passage, it is possible to uniformize the static pressure distribution in the circumferential direction within the scroll, thereby improving the stall characteristics of the centrifugal compressor and widening the operating range of the centrifugal compressor.

[0009] In the above aspect, when the cross section of the downstream portion is gradually changed from a cross section cut by a plane including the rotation axis to a cross section perpendicular to the central axis (Y) of the discharge flow path, the cross-sectional area of ​​the downstream portion may increase at the same constant gradient from the upstream end to the downstream end of the downstream portion.

[0010] According to this aspect, by appropriately setting the cross-sectional area schedule of the downstream portion of the discharge flow path, the static pressure distribution in the circumferential direction within the scroll can be made more uniform.

[0011] In the above aspect, the cross-sectional area of ​​the downstream portion in a cross section perpendicular to the central axis of the discharge flow path may increase at the constant gradient from the upstream end to the downstream end of the downstream portion.

[0012] According to this aspect, by appropriately setting the cross-sectional area schedule of the downstream portion of the discharge flow path, the static pressure distribution in the circumferential direction within the scroll can be made more uniform.

[0013] In the above aspect, the discharge flow path may be provided with a raised portion (37) that bulges toward the central axis of the discharge flow path at a position where it intersects with a plane that includes the rotation axis and passes through the communication port.

[0014] According to this aspect, an ideal cross-sectional area schedule can be achieved with a simple configuration.

[0015] In the above aspect, the raised portion may include a minimum diameter portion (38) having the smallest inner diameter within the discharge flow path, and may gradually decrease in diameter from the upstream side of the minimum diameter portion toward the minimum diameter portion while maintaining the cross-sectional shape, and gradually increase in diameter from the minimum diameter portion toward the downstream side of the minimum diameter portion while maintaining the cross-sectional shape.

[0016] According to this aspect, the raised portion is gently inclined while maintaining its cross-sectional shape, thereby allowing the fluid to flow smoothly.

[0017] In the above aspect, the communication port may be located radially inward relative to the central axis of the discharge flow path, with the rotation axis as the reference, and the raised portion may bulge from at least the radially outward relative to the rotation axis toward the central axis of the discharge flow path.

[0018] According to this aspect, it is not necessary to significantly expand the raised portion from the inside in the radial direction in order to achieve an ideal cross-sectional area schedule, and therefore it is possible to suppress abrupt changes in static pressure inside the scroll around the communication port located on the inside in the radial direction.

[0019] In the above aspect, the discharge flow path may gradually increase in diameter from the raised portion to the downstream end.

[0020] According to this aspect, the fluid can flow smoothly from the raised portion to the downstream end of the discharge flow path.

[0021] In the above aspect, the cross-sectional area of ​​the scroll passage in a cross section cut along a plane including the rotation axis may increase at the constant gradient from the upstream end to the downstream end of the scroll passage.

[0022] According to this aspect, by more appropriately setting the cross-sectional area schedule of the scroll flow passage, the static pressure distribution in the circumferential direction within the scroll can be made more uniform.

[0023] In order to solve the above-mentioned problems, another aspect of the present invention is a centrifugal compressor (6), comprising: an impeller (22) rotatable about a rotation axis (X); and a scroll (40) arranged around the impeller, wherein the scroll has a plurality of scroll passages (41, 42) extending in a circumferential direction based on the rotation axis; a plurality of discharge passages (44, 45) each extending from a downstream end of the plurality of scroll passages in a direction different from the circumferential direction; and a plurality of discharge passages (44, 45) each connecting an upstream end of one of the plurality of scroll passages to one of the plurality of discharge passages. and a plurality of communication ports (47, 48) through which the scroll flow passages pass, and each of the discharge flow passages has an upstream portion (44A, 45A) extending from the upstream end of the discharge flow passage to the respective communication port, and a downstream portion (44B, 45B) extending from the respective communication port to the downstream end of the discharge flow passage, and the cross-sectional area of ​​each of the scroll flow passages in a cross section taken along a plane including the rotation axis increases from the upstream end to the downstream end of each of the scroll flow passages, and the cross-sectional area of ​​the upstream portion in a cross section taken along the plane including the rotation axis increases at a constant gradient from the upstream end to the downstream end of the upstream portion.

[0024] According to this aspect, in a centrifugal compressor in which a plurality of scroll passages, a plurality of discharge passages, and a plurality of communication ports are provided for one scroll, the cross-sectional area schedule of the upstream portions of the scroll passage and the discharge passage can be appropriately set to uniformize the static pressure distribution in the circumferential direction within the scroll, thereby improving the stall characteristics of the centrifugal compressor and widening the operating range of the centrifugal compressor.

[0025] In order to solve the above-mentioned problems, another aspect of the present invention is a scroll (23) that includes an impeller (22) that can rotate around a rotation axis (X), and a scroll (23) that is arranged around the impeller, wherein the scroll has a scroll flow path (28) that extends in a circumferential direction based on the rotation axis, a discharge flow path (32) that extends from a downstream end of the scroll flow path in a direction different from the circumferential direction, and a communication port (33) that communicates an upstream end of the scroll flow path with the discharge flow path, and the discharge flow path is A flow path design method for a centrifugal compressor (6) having an upstream portion (32A) extending from the upstream end of an outlet flow path to the communication port and a downstream portion (32B) extending from the communication port to the downstream end of the discharge flow path, wherein a cross-sectional area of ​​the scroll flow path in a cross section taken along a plane including the rotation axis is increased from the upstream end to the downstream end of the scroll flow path, and a cross-sectional area of ​​the upstream portion in a cross section taken along the plane including the rotation axis is increased at a constant gradient from the upstream end to the downstream end of the upstream portion.

[0026] According to this aspect, by appropriately setting the cross-sectional area schedule of the upstream portions of the scroll passage and the discharge passage, it is possible to uniformize the static pressure distribution in the circumferential direction within the scroll, thereby improving the stall characteristics of the centrifugal compressor and widening the operating range of the centrifugal compressor.

[0027] In order to solve the above-mentioned problems, another aspect of the present invention is a scroll (40) that includes an impeller (22) that can rotate about a rotation axis (X), and a scroll (40) that is arranged around the impeller, the scroll including a plurality of scroll passages (41, 42) that extend in a circumferential direction based on the rotation axis, a plurality of discharge passages (44, 45) that extend from downstream ends of the plurality of scroll passages in a direction different from the circumferential direction, and a plurality of communication ports (47, 48) that respectively communicate an upstream end of one of the plurality of scroll passages with one of the plurality of discharge passages. ), each discharge flow path having an upstream portion (44A, 45A) extending from the upstream end of the discharge flow path to the respective communication port, and a downstream portion (44B, 45B) extending from the respective communication port to the downstream end of the discharge flow path, wherein a cross-sectional area of ​​each scroll flow path in a cross section taken along a plane including the rotation axis is increased from the upstream end to the downstream end of each scroll flow path, and a cross-sectional area of ​​the upstream portion in a cross section taken along the plane including the rotation axis is increased at a constant gradient from the upstream end to the downstream end of the upstream portion.

[0028] According to this aspect, in a centrifugal compressor in which a plurality of scroll passages, a plurality of discharge passages, and a plurality of communication ports are provided for one scroll, the cross-sectional area schedule of the upstream portions of the scroll passage and the discharge passage can be appropriately set to uniformize the static pressure distribution in the circumferential direction within the scroll, thereby improving the stall characteristics of the centrifugal compressor and widening the operating range of the centrifugal compressor. [Effects of the Invention]

[0029] According to the above-described aspect, it is possible to provide a centrifugal compressor that can improve stall characteristics and widen the operating range by making the static pressure distribution in the circumferential direction inside the scroll uniform. [Brief explanation of the drawings]

[0030] [Figure 1] 1 is a cross-sectional view showing a turbocharger according to a first embodiment; [Figure 2]FIG. 1 is a side view of a compressor scroll according to a first embodiment, viewed in the axial direction; [Figure 3] FIG. 1 is a perspective view of a compressor scroll according to a first embodiment; [Figure 4] FIG. 1 is a side view of a scroll passage and a discharge passage according to a first embodiment, viewed in the axial direction. [Figure 5] Graph showing the relationship between scroll phase and cross-sectional area in the first embodiment and a comparative example. [Figure 6] Graph showing the relationship between scroll phase and static pressure in the first embodiment and a comparative example. [Figure 7] Graph showing the relationship between scroll phase and flow rate in the first embodiment and a comparative example. [Figure 8] Graph showing the relationship between flow rate and pressure ratio in the first embodiment and a comparative example. [Figure 9] 10 is a cross-sectional view of a scroll passage according to another embodiment of the present invention; [Figure 10] Graph showing the relationship between scroll phase and cross-sectional area in another embodiment [Figure 11] FIG. 10 is a side view of the compressor scroll according to the second embodiment, viewed in the axial direction. DETAILED DESCRIPTION OF THE INVENTION

[0031] First Embodiment A turbocharger 1 according to a first embodiment of the present invention will be described below with reference to Fig. 1 to Fig. 8. The dashed-dotted line X in Fig. 1 indicates the rotational axis of the turbocharger 1 (hereinafter referred to as "rotational axis X"). Hereinafter, when the terms axial direction, radial direction, and circumferential direction are mentioned, they respectively refer to the axial direction, radial direction, and circumferential direction based on the rotational axis X.

[0032] 1, the turbocharger 1 has a center housing 3, a rotary shaft 4 rotatably supported by the center housing 3, a turbine 5 disposed on one axial side of the center housing 3, and a centrifugal compressor 6 (hereinafter referred to as "compressor 6") disposed on the other axial side of the center housing 3. The components of the turbocharger 1 will be described below in order.

[0033] <Center housing 3> The center housing 3 has a cylindrical shape extending in the axial direction. A bearing accommodating portion 8 is provided in the radial center of the center housing 3. A bearing 9 is accommodated in the bearing accommodating portion 8.

[0034] <Rotation axis 4> The rotating shaft 4 extends in the axial direction centered on the rotation axis X. The rotating shaft 4 axially passes through the center housing 3. The rotating shaft 4 is rotatably supported by the center housing 3 via bearings 9. Therefore, the rotating shaft 4 is rotatable around the rotation axis X.

[0035] <Turbine 5> The turbine 5 includes a turbine housing 11 , a turbine impeller 12 housed in the turbine housing 11 , and a turbine scroll 13 arranged around the turbine impeller 12 .

[0036] A turbine impeller chamber 15 is provided at one axial end of the turbine housing 11. The turbine impeller chamber 15 is connected to an exhaust pipe (not shown) via an exhaust outlet passage 16 that extends in the axial direction.

[0037] The turbine impeller 12 is housed in a turbine impeller chamber 15. The turbine impeller 12 is fixed to one axial end of the rotating shaft 4. Therefore, the turbine impeller 12 is rotatable integrally with the rotating shaft 4 around the rotation axis X.

[0038] The turbine scroll 13 is disposed around one axial end of the turbine housing 11. The turbine scroll 13 is formed integrally with the turbine housing 11. The turbine scroll 13 is provided with an exhaust inlet passage 17. The exhaust inlet passage 17 extends in the circumferential direction. The exhaust inlet passage 17 is connected to an exhaust passage (not shown). The exhaust inlet passage 17 communicates with the turbine impeller chamber 15 via an annular communication passage 18 that extends in the radial direction.

[0039] <Compressor 6> Hereinafter, when describing the compressor 6, the upstream side or upstream end refers to the upstream side or upstream end in the flow direction of air (one example of a fluid) inside the compressor 6. Similarly, when describing the compressor 6, the downstream side or downstream end refers to the downstream side or downstream end in the flow direction of air inside the compressor 6. Furthermore, when describing the compressor 6, the middle part of a certain component refers to the part between the upstream end and downstream end of that component.

[0040] Referring to FIG. 1, the compressor 6 includes a compressor housing 21 , a compressor impeller 22 housed in the compressor housing 21 , and a compressor scroll 23 disposed around the compressor impeller 22 .

[0041] A compressor impeller chamber 25 is provided at one axial end of the compressor housing 21. The compressor impeller chamber 25 communicates with an intake passage (not shown) via an intake inlet passage 26 extending in the axial direction.

[0042] The compressor impeller 22 is housed in a compressor impeller chamber 25. The compressor impeller 22 is fixed to the other axial end of the rotating shaft 4. Therefore, the compressor impeller 22 is rotatable integrally with the rotating shaft 4 around the rotation axis X.

[0043] The compressor scroll 23 is disposed around one axial end of the compressor housing 21. The compressor scroll 23 is formed integrally with the compressor housing 21.

[0044] 1 to 3, the compressor scroll 23 is provided with a scroll passage 28. The scroll passage 28 extends in the circumferential direction. The scroll passage 28 has a perfectly circular cross-sectional shape. The scroll passage 28 communicates with the compressor impeller chamber 25 via an annular diffuser chamber 29 that extends in the radial direction. The scroll passage 28 gradually increases in diameter from its upstream end 28A to its downstream end 28B.

[0045] 2 and 3, the compressor scroll 23 is provided with a discharge passage 32. The discharge passage 32 extends linearly from the downstream end 28B of the scroll passage 28 in a tangential direction to the circumferential direction (an example of a direction different from the circumferential direction). In other embodiments, the discharge passage 32 may extend from the downstream end 28B of the scroll passage 28 in a direction other than a tangential direction to the circumferential direction. In other embodiments, the discharge passage 32 may be partially or entirely curved. The discharge passage 32 has a perfectly circular cross-sectional shape.

[0046] An inner diameter portion (a radially inner portion) of the middle portion of the discharge flow path 32 communicates with the upstream end 28A of the scroll flow path 28 via a communication port 33. The communication port 33 is located radially inward with respect to the central axis Y of the discharge flow path 32. Hereinafter, the portion from the upstream end of the discharge flow path 32 to the communication port 33 (more specifically, the downstream end of the communication port 33) will be referred to as the upstream portion 32A of the discharge flow path 32, and the portion from the communication port 33 (more specifically, the downstream end of the communication port 33) to the downstream end of the discharge flow path 32 will be referred to as the downstream portion 32B of the discharge flow path 32.

[0047] A raised portion 37 is provided in the middle of the discharge flow path 32 at a position where it intersects with a plane Z that includes the rotation axis X and passes through the communication port 33 (more specifically, the downstream end of the communication port 33). The raised portion 37 is provided across the upstream portion 32A and the downstream portion 32B of the discharge flow path 32. The raised portion 37 bulges toward the central axis Y of the discharge flow path 32 around its entire circumference and has a true circular cross-sectional shape. The raised portion 37 includes a minimum diameter portion 38 that has the smallest inner diameter within the discharge flow path 32. The diameter of the raised portion 37 gradually decreases from the upstream side of the minimum diameter portion 38 toward the minimum diameter portion 38 while maintaining the true circular cross-sectional shape. The diameter of the raised portion 37 gradually increases from the minimum diameter portion 38 toward the downstream side of the minimum diameter portion 38 while maintaining the true circular cross-sectional shape.

[0048] The diameter of the discharge passage 32 gradually increases while maintaining a circular cross-sectional shape from the raised portion 37 to the downstream end of the discharge passage 32. The compressor scroll 23 is provided with an annular flange 35 on the outer periphery of the downstream end of the discharge passage 32. A flange of an intake pipe (not shown) connected to the compressor 6 is fixed to the flange 35.

[0049] <Function of turbocharger 1> 1, when an internal combustion engine (not shown) is operating, exhaust gas discharged from an exhaust port of the internal combustion engine flows into an exhaust inlet passage 17 via an exhaust passage (not shown). The exhaust gas that has flowed into the exhaust inlet passage 17 flows from the exhaust inlet passage 17 through a communication passage 18 into a turbine impeller chamber 15 and is blown onto the turbine impeller 12 in the turbine impeller chamber 15. This applies a rotational driving force to the turbine impeller 12, causing the turbine impeller 12 to rotate around the rotation axis X. Accordingly, the rotating shaft 4 and the compressor impeller 22 rotate integrally with the turbine impeller 12 around the rotation axis X.

[0050] When the compressor impeller 22 rotates in this manner, air in the intake passage (not shown) flows into the compressor impeller chamber 25 through the intake inlet passage 26. The air that has flowed into the compressor impeller chamber 25 is compressed by the compressor impeller 22 and flows from the compressor impeller chamber 25 through the diffuser chamber 29 into the scroll passage 28.

[0051] 2 and 3, the air that has flowed into the scroll passage 28 as described above is decelerated in the scroll passage 28. The air that has passed through the scroll passage 28 flows into the discharge passage 32. A portion of the air that has flowed into the discharge passage 32 flows again into the scroll passage 28 through the communication port 33. In this manner, the air circulates within the compressor scroll 23. Another portion of the air that has flowed into the discharge passage 32 passes through the discharge passage 32, and is then supplied to an intake port of the internal combustion engine through an intake pipe (not shown).

[0052] <Compressor Scroll 23 Cross-Sectional Area Schedule> Next, with reference to FIGS. 4 to 8, the cross-sectional area schedule of the compressor scroll 23 in the first embodiment and the comparative example will be described. Hereinafter, for convenience of explanation, the scroll phase at the boundary between the scroll passage 28 and the discharge passage 32 is set to 0 degrees (360 degrees, 720 degrees, ...), and the scroll phase at the communication port 33 (specifically, the downstream end of the communication port 33) is set to θ degrees. The scroll phase increases in the direction of circulation of air in the compressor scroll 23 (arrow R in FIG. 4). Hereinafter, a cross section cut along a plane including the rotation axis X (in other words, a plane extending radially from the rotation axis X when viewed in the axial direction) will be referred to as a rotation axis cross section, and a cross section perpendicular to the central axis Y of the discharge passage 32 will be referred to as a central axis cross section.

[0053] 4 and 5, in the first embodiment and the comparative example, the cross-sectional area of ​​the scroll passage 28 in the rotation axis cross section (see S1 to S4 in FIG. 4) increases at a constant gradient M (M=a / b) from the upstream end 28A of the scroll passage 28 to the downstream end 28B.

[0054] As shown by the two-dot chain line in Fig. 4, in the comparative example, the discharge passage 32 does not have a raised portion 37, and the diameter of the discharge passage 32 increases linearly from the upstream end to the downstream end. Therefore, as shown by the two-dot chain line in Fig. 5, the cross-sectional area of ​​the upstream portion 32A of the discharge passage 32 in the cross section along the rotation axis increases sharply. As a result, as shown in Figs. 6 and 7, the static pressure distribution and flow rate distribution in the circumferential direction within the compressor scroll 23 become non-uniform. In particular, the difference in static pressure and flow rate becomes large between the upstream side and downstream side of the communication port 33 (scroll phase = θ).

[0055] In contrast, as shown by the solid line in Fig. 4, in the first embodiment, a raised portion 37 is provided in the discharge passage 32, and the diameter of the discharge passage 32 is first reduced and then expanded. Therefore, as shown by the dashed line in Fig. 5, the cross-sectional area of ​​the upstream portion 32A of the discharge passage 32 in the rotation axis cross section (see S4 to S6 in Fig. 4) increases at a constant gradient M from the upstream end to the downstream end of the upstream portion 32A. Furthermore, when the cross section of the downstream portion 32B of the discharge passage 32 is gradually changed at a constant rate from the rotation axis cross section (see S6 in Fig. 4) to the central axis cross section (see S7 in Fig. 4), the cross-sectional area of ​​the downstream portion 32B increases at a constant gradient M from the upstream end to the downstream end of the downstream portion 32B. Accordingly, as shown in Figs. 6 and 7, the static pressure distribution and the flow rate distribution in the circumferential direction within the compressor scroll 23 can be made uniform.

[0056] FIG. 8 shows the relationship between the flow rate and pressure ratio inside the compressor scroll 23 for each rotation speed P of the compressor impeller 22. L1 in FIG. 8 shows the stall limit line (a line indicating the limit as to whether or not a stall will occur) in the comparative example, and L2 in FIG. 8 shows the stall limit line in the first embodiment. As shown in FIG. 8, in the first embodiment, the stall limit line is shifted to the upper left compared to the comparative example. This shows that in the first embodiment, stalling is less likely to occur even when the compressor 6 is used with a low flow rate and a high pressure ratio.

[0057] As described above, in the first embodiment, by appropriately setting the cross-sectional area schedule of the compressor scroll 23, it is possible to uniformize the static pressure distribution and the flow rate distribution in the circumferential direction inside the compressor scroll 23. This improves the stall characteristics of the compressor 6 and widens the operating range of the compressor 6.

[0058] <Flow path design method for compressor 6> The designer designs the scroll passage 28 and the discharge passage 32 so as to satisfy the following (1) to (3). Note that the designer may be a human being or a computer equipped with a processor. (1) The cross-sectional area of ​​the scroll passage 28 in the cross section along the rotation axis increases at a constant gradient M from the upstream end 28A of the scroll passage 28 to the downstream end 28B. (2) The cross-sectional area of ​​the upstream portion 32A of the discharge flow passage 32 in the cross section along the axis of rotation increases at a constant gradient M from the upstream end to the downstream end of the upstream portion 32A. (3) When the cross section of the downstream portion 32B of the discharge flow path 32 is gradually changed at a constant rate from the rotation axis cross section to the central axis cross section, the cross-sectional area of ​​the downstream portion 32B increases at a constant gradient M from the upstream end to the downstream end of the downstream portion 32B.

[0059] <Modification> Referring to FIG. 1 , in the first embodiment, the scroll passage 28 has a true circular cross-sectional shape. In other embodiments, the scroll passage 28 may have a circular cross-sectional shape other than a true circular shape (e.g., an oval, an ellipse, a semicircle, etc.). Furthermore, in other embodiments, as shown in FIG. 9 , the scroll passage 28 may have a non-circular (irregular) cross-sectional shape. For example, as shown in FIG. 9( a), a protrusion 28X may be provided in a radially inner portion of the scroll passage 28. Alternatively, as shown in FIG. 9( b), a recess 28Y may be provided in a radially inner portion of the scroll passage 28. The above-described modified shapes of the scroll passage 28 can also be applied to the shape of the discharge passage 32.

[0060] Referring to Fig. 5, in the first embodiment, the cross-sectional area of ​​the scroll passage 28 in the rotation axis cross section increases at a constant gradient M (M = a / b) from the upstream end 28A to the downstream end 28B of the scroll passage 28. As shown in Fig. 10, in another embodiment, the cross-sectional area of ​​the scroll passage 28 in the rotation axis cross section may increase with a changing gradient from the upstream end 28A to the downstream end 28B of the scroll passage 28. For example, as shown by the solid line in Fig. 10, the gradient of the cross-sectional area of ​​the scroll passage 28 in the rotation axis cross section may decrease once and then increase. Alternatively, as shown by the dashed line in Fig. 10, the gradient of the cross-sectional area of ​​the scroll passage 28 in the rotation axis cross section may increase once and then decrease.

[0061] In the first embodiment, the raised portion 37 bulges toward the central axis Y of the discharge flow path 32 over its entire circumference. In other embodiments, the raised portion 37 may bulge toward the central axis Y of the discharge flow path 32 over only a portion of its circumference. For example, the raised portion 37 may bulge toward the central axis Y of the discharge flow path 32 from one or both axial sides, or may bulge toward the central axis Y of the discharge flow path 32 from one or both radial sides. However, it is preferable that the raised portion 37 bulges toward the central axis Y of the discharge flow path 32 at least from the radial outer side.

[0062] In the first embodiment, when the cross section of the downstream portion 32B of the discharge flow path 32 is gradually changed from the rotation axis cross section to the central axis cross section, the cross-sectional area of ​​the downstream portion 32B increases from the upstream end to the downstream end of the downstream portion 32B at a constant gradient M. In other embodiments, the cross-sectional area of ​​the downstream portion 32B in the central axis cross section may increase at a constant rate from the upstream end to the downstream end of the downstream portion 32B.

[0063] Second Embodiment A compressor scroll 40 according to a second embodiment of the present invention will be described below with reference to Fig. 11. The compressor scroll 40 is applied to the compressor 6 of the turbocharger 1, similar to the compressor scroll 23 according to the first embodiment. Note that a description of the same content as in the first embodiment will be omitted.

[0064] The compressor scroll 40 is provided with first and second scroll passages 41, 42. The first and second scroll passages 41, 42 extend in the circumferential direction. The first and second scroll passages 41, 42 are arranged so that their circumferential positions do not overlap with each other. The cross-sectional area of ​​the first scroll passage 41 in the rotation axis cross section (a cross section cut along a plane including the rotation axis X) increases at a constant gradient N from the upstream end 41A to the downstream end 41B of the first scroll passage 41. The cross-sectional area of ​​the second scroll passage 42 in the rotation axis cross section increases at a constant gradient N from the upstream end 42A to the downstream end 42B of the second scroll passage 42.

[0065] The compressor scroll 40 is provided with a first discharge flow path 44. The first discharge flow path 44 extends linearly from a downstream end 41B of the first scroll flow path 41 in a direction different from the circumferential direction. An inner diameter portion (a radially inner portion) of an intermediate portion of the first discharge flow path 44 is in communication with an upstream end 42A of the second scroll flow path 42 via a first communication port 47. Hereinafter, the portion from the upstream end of the first discharge flow path 44 to the first communication port 47 (more specifically, the downstream end of the first communication port 47) will be referred to as an upstream portion 44A of the first discharge flow path 44, and the portion from the first communication port 47 (more specifically, the downstream end of the first communication port 47) to the downstream end of the first discharge flow path 44 will be referred to as a downstream portion 44B of the first discharge flow path 44.

[0066] The cross-sectional area of ​​the upstream portion 44A of the first discharge flow path 44 in the rotation axis cross section increases at a constant gradient N from the upstream end to the downstream end of the upstream portion 44A. Furthermore, when the cross section of the downstream portion 44B of the first discharge flow path 44 is gradually changed at a constant rate from the rotation axis cross section to the central axis cross section (a cross section perpendicular to the central axis Y1 of the first discharge flow path 44), the cross-sectional area of ​​the downstream portion 44B increases at a constant gradient N from the upstream end to the downstream end of the downstream portion 44B. In other embodiments, the cross-sectional area of ​​the downstream portion 44B of the first discharge flow path 44 in the central axis cross section may increase at a constant rate from the upstream end to the downstream end of the downstream portion 44B.

[0067] The compressor scroll 40 is provided with a second discharge flow path 45. The second discharge flow path 45 extends linearly from a downstream end 42B of the second scroll flow path 42 in a direction different from the circumferential direction. An inner diameter portion (a radially inner portion) of an intermediate portion of the second discharge flow path 45 is in communication with an upstream end 41A of the first scroll flow path 41 via a second communication port 48. Hereinafter, the portion from the upstream end of the second discharge flow path 45 to the second communication port 48 (more specifically, the downstream end of the second communication port 48) will be referred to as an upstream portion 45A of the second discharge flow path 45, and the portion from the second communication port 48 (more specifically, the downstream end of the second communication port 48) to the downstream end of the second discharge flow path 45 will be referred to as a downstream portion 45B of the second discharge flow path 45.

[0068] The cross-sectional area of ​​the upstream portion 45A of the second discharge flow path 45 in the rotation axis cross section increases at a constant gradient N from the upstream end to the downstream end of the upstream portion 45A. Furthermore, when the cross section of the downstream portion 45B of the second discharge flow path 45 is gradually changed at a constant rate from the rotation axis cross section to the central axis cross section (a cross section perpendicular to the central axis Y2 of the second discharge flow path 45), the cross-sectional area of ​​the downstream portion 45B increases at a constant gradient N from the upstream end to the downstream end of the downstream portion 45B. Note that in other embodiments, the cross-sectional area of ​​the downstream portion 45B of the second discharge flow path 45 in the central axis cross section may increase at a constant rate from the upstream end to the downstream end of the downstream portion 45B.

[0069] <Flow path design method for compressor 6> The designer designs the first and second scroll passages 41, 42 and the first and second discharge passages 44, 45 so as to satisfy the following (1) to (6). Note that the designer may be a human being or a computer equipped with a processor. (1) The cross-sectional area of ​​the first scroll passage 41 in the cross section along the rotation axis increases at a constant gradient N from the upstream end 41A of the first scroll passage 41 to the downstream end 41B. (2) The cross-sectional area of ​​the second scroll passage 42 in the cross section along the rotation axis increases at a constant gradient N from the upstream end 42A of the second scroll passage 42 to the downstream end 42B. (3) The cross-sectional area of ​​the upstream portion 44A of the first discharge flow path 44 in the cross section along the rotation axis increases at a constant gradient N from the upstream end to the downstream end of the upstream portion 44A. (4) When the cross section of the downstream portion 44B of the first discharge flow path 44 is gradually changed at a constant rate from the rotation axis cross section to the central axis cross section, the cross-sectional area of ​​the downstream portion 44B increases at a constant gradient N from the upstream end to the downstream end of the downstream portion 44B. (5) The cross-sectional area of ​​the upstream portion 45A of the second discharge flow path 45 in the cross section along the rotation axis increases at a constant gradient N from the upstream end to the downstream end of the upstream portion 45A. (6) When the cross section of the downstream portion 45B of the second discharge flow path 45 is gradually changed at a constant rate from the rotation axis cross section to the central axis cross section, the cross-sectional area of ​​the downstream portion 45B increases at a constant gradient N from the upstream end to the downstream end of the downstream portion 45B.

[0070] <Modification> In the second embodiment, the compressor scroll 40 has two scroll passages, two discharge passages, and two communication ports. In other embodiments, the compressor scroll 40 may have three or more scroll passages, three or more discharge passages, and three or more communication ports.

[0071] In the first and second embodiments, the configuration of the present invention is applied to a mechanical compressor that uses exhaust gas to rotate the rotary shaft 4. In other embodiments, the configuration of the present invention may be applied to an electric compressor that uses an electric motor to rotate the rotary shaft 4.

[0072] In the first and second embodiments, the configuration of the present invention is applied to the compressor 6 of the turbocharger 1. In other embodiments, the configuration of the present invention may be applied to a compressor of equipment other than the turbocharger 1 (for example, a gas turbine engine or a pump for compressing a fluid).

[0073] Although the description of the specific embodiment has been completed above, the present invention is not limited to the above embodiment and its modifications, and can be modified in a wide range of ways. [Explanation of symbols]

[0074] 6: Compressor (centrifugal compressor) 22: Compressor impeller 23: Compressor scroll 28:Scroll flow path 28A: Upstream end 28B: Downstream end 32: Discharge flow path 32A:Upstream part 32B: Downstream part 33: Connecting port 37: Protuberance 38:Minimum diameter part 40: Compressor scroll 41: First scroll passage 41A: Upstream end 41B: Downstream end 42: Second scroll passage 42A: Upstream end 42B: Downstream end 44: First discharge flow path 44A:Upstream part 44B: Downstream part 45: Second discharge flow path 45A:Upstream part 45B: Downstream part 47: 1st communication port 48:Second communication port X: Rotation axis Y: Center axis line

Claims

1. A centrifugal compressor, an impeller rotatable about a rotation axis; a scroll disposed around the impeller, The scroll a scroll flow path extending in a circumferential direction based on the rotation axis; a discharge flow path extending from a downstream end of the scroll flow path in a direction different from the circumferential direction; a communication port that communicates the upstream end of the scroll flow path with the discharge flow path, The discharge flow path is an upstream portion extending from the upstream end of the discharge flow path to the communication port; a downstream portion extending from the communication port to a downstream end of the discharge flow path, a cross-sectional area of ​​the scroll passage in a cross section taken along a plane including the rotation axis increases from the upstream end to the downstream end of the scroll passage, A centrifugal compressor wherein the cross-sectional area of ​​the upstream portion in a cross section taken along a plane including the rotation axis increases at a constant gradient from the upstream end to the downstream end of the upstream portion.

2. 2. The centrifugal compressor according to claim 1, wherein when a cross section of the downstream portion is gradually changed from a cross section taken along a plane including the rotation axis to a cross section perpendicular to a central axis of the discharge flow path, the cross-sectional area of ​​the downstream portion increases at the constant gradient from the upstream end to the downstream end of the downstream portion.

3. 2. The centrifugal compressor according to claim 1, wherein the cross-sectional area of ​​the downstream portion in a cross section perpendicular to the central axis of the discharge passage increases at the constant gradient from the upstream end to the downstream end of the downstream portion.

4. 2. The centrifugal compressor according to claim 1, wherein the discharge passage is provided with a raised portion that bulges toward a central axis of the discharge passage at a position where the raised portion intersects with a plane that includes the rotation axis and passes through the communication port.

5. The raised portion is 5. The centrifugal compressor according to claim 4, wherein the discharge flow path includes a minimum diameter portion having the smallest inner diameter within the discharge flow path, the diameter of the discharge flow path gradually decreasing from an upstream side of the minimum diameter portion toward the minimum diameter portion while maintaining a cross-sectional shape, and the diameter of the discharge flow path gradually increasing from the minimum diameter portion toward a downstream side of the minimum diameter portion while maintaining a cross-sectional shape.

6. the communication port is located radially inward with respect to the central axis of the discharge flow path, the rotation axis being used as a reference; The centrifugal compressor according to claim 4 , wherein the raised portion bulges from at least the radially outer side toward the central axis of the discharge flow passage.

7. The centrifugal compressor according to claim 4, wherein the discharge passage gradually expands in diameter from the raised portion to the downstream end.

8. 8. The centrifugal compressor according to claim 1, wherein a cross-sectional area of ​​the scroll passage in a cross section taken along a plane including the rotation axis increases at the constant gradient from the upstream end to the downstream end of the scroll passage.

9. A centrifugal compressor, an impeller rotatable about a rotation axis; a scroll disposed around the impeller, The scroll a plurality of scroll flow paths extending in a circumferential direction based on the rotation axis; a plurality of discharge flow paths each extending in a direction different from the circumferential direction from downstream ends of the plurality of scroll flow paths; a plurality of communication ports each communicating an upstream end of one of the plurality of scroll flow paths with one of the plurality of discharge flow paths, Each of the discharge channels is an upstream portion extending from the upstream end of each of the discharge flow paths to each of the communication ports; a downstream portion extending from each of the communication ports to a downstream end of each of the discharge flow paths, a cross-sectional area of ​​each of the scroll passages in a cross section taken along a plane including the rotation axis increases from the upstream end to the downstream end of each of the scroll passages, A centrifugal compressor wherein the cross-sectional area of ​​the upstream portion in a cross section taken along a plane including the rotation axis increases at a constant gradient from the upstream end to the downstream end of the upstream portion.

10. an impeller rotatable about a rotation axis; a scroll disposed around the impeller, The scroll a scroll flow path extending in a circumferential direction based on the rotation axis; a discharge flow path extending from a downstream end of the scroll flow path in a direction different from the circumferential direction; a communication port that communicates the upstream end of the scroll flow path with the discharge flow path, The discharge flow path is an upstream portion extending from the upstream end of the discharge flow path to the communication port; a downstream portion extending from the communication port to a downstream end of the discharge flow path, a cross-sectional area of ​​the scroll passage in a cross section cut along a plane including the rotation axis increases from the upstream end to the downstream end of the scroll passage; A flow path design method for a centrifugal compressor, wherein a cross-sectional area of ​​the upstream portion in a cross section taken along a plane including the rotation axis increases at a constant gradient from the upstream end to the downstream end of the upstream portion.

11. an impeller rotatable about a rotation axis; a scroll disposed around the impeller, The scroll a plurality of scroll flow paths extending in a circumferential direction based on the rotation axis; a plurality of discharge flow paths each extending in a direction different from the circumferential direction from downstream ends of the plurality of scroll flow paths; a plurality of communication ports each communicating an upstream end of one of the plurality of scroll flow paths with one of the plurality of discharge flow paths, Each of the discharge channels is an upstream portion extending from the upstream end of each of the discharge flow paths to each of the communication ports; a downstream portion extending from each of the communication ports to a downstream end of each of the discharge flow paths, a cross-sectional area of ​​each of the scroll passages in a cross section cut along a plane including the rotation axis increases from the upstream end to the downstream end of each of the scroll passages; A flow path design method for a centrifugal compressor, wherein a cross-sectional area of ​​the upstream portion in a cross section taken along a plane including the rotation axis increases at a constant gradient from the upstream end to the downstream end of the upstream portion.

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